In recent years,many studies have focused on the effects of global climate warming and increased nitrogen deposition on the structure and function of grassland ecosystem.However,there are still significant uncertainti...In recent years,many studies have focused on the effects of global climate warming and increased nitrogen deposition on the structure and function of grassland ecosystem.However,there are still significant uncertainties in the response mechanism of stability of plant community biomass in alpine meadows of the Qinghai-Xizang Plateau,China to these two major climate factors.Given this,based on field control experiments,this study systematically evaluated the effects of different levels of climate warming(W0(no warming),W1(air temperature increased by 0.47℃ or soil temperature increased by 0.61℃),W2(air temperature increased by 0.92℃ or soil temperature increased by 1.09℃),W3(air temperature increased by 1.44℃ or soil temperature increased by 1.95℃)),nitrogen deposition(N0(0 kg N/(hm^(2)·a)),N16(16 kg N/(hm^(2)·a)),and N32(32 kg N/(hm^(2)·a))),and their interactions on plant community biomass and its temporal stability,and explored its potential regulatory mechanisms.The results showed that the biomass of total community,Gramineae,and dominant species increased significantly with increasing temperature,but the biomass of common and rare species decreased significantly.Nitrogen deposition also significantly promoted the biomass accumulation of community and gramineous plants.Under the treatment of W3N32,the biomass of plant community,Gramineae,and dominant species reached the highest values,indicating that there was a synergistic effect under this treatment.Structural equation model showed that increasing temperature significantly decreased the stability of plant community biomass by reducing the stability of grass and dominant species biomass and weakening species asynchronism.Interaction of increased nitrogen deposition and temperature increased the biomass fluctuation of grass functional group,thus amplifying its negative influence on community stability.More attention should be paid to the response and regulatory mechanisms of dominant species and functional groups under global climate change.This study provides a theoretical basis for revealing the stability maintenance mechanism of alpine grassland and also provides scientific support for the development of future grassland ecosystem management and assessment.展开更多
In recent decades, global climate change and overgrazing have led to severe degradation of alpine meadows. Understanding the changes in soil characteristics and vegetation communities in alpine meadows with different ...In recent decades, global climate change and overgrazing have led to severe degradation of alpine meadows. Understanding the changes in soil characteristics and vegetation communities in alpine meadows with different degrees of degradation is helpful to reveal the mechanism of degradation process and take the remediation measures effectively. This study analyzed the changes in vegetation types and soil characteristics and their interrelationships under three degradation degrees, i.e., non-degradation(ND),moderate degradation(MD), and severe degradation(SD) in the alpine meadows of northeastern Qinghai-Xizang Plateau, China through the long-term observation. Results showed that the aggressive degradation changed the plant species, with the vegetation altering from leguminous and gramineous to forbs and harmful grasses. The Pielou evenness and Simpson index increased by 24.58% and 7.01%,respectively, the Shannon-Wiener index decreased by 17.52%, and the species richness index remained constant. Soil conductivity, soil organic matter, total potassium, available potassium, and porosity declined.However, the number of vegetation species increased in MD. Compared with ND, the plant diversity in MD enhanced by 8.33%, 8.69%, and 7.41% at family, genus, and species levels, respectively. In conclusion,changes in soil properties due to degradation can significantly influence the condition of above-ground vegetation. Plant diversity increases, which improves the structure of belowground network. These findings may contribute to designing better protection measures of alpine meadows against global climate change and overgrazing.展开更多
The impact of summer cattle grazing on water quality during three very different climatic years in the Sierra Nevada was investigated. Water year 2009 had near normal precipitation;2010 had late precipitation and snow...The impact of summer cattle grazing on water quality during three very different climatic years in the Sierra Nevada was investigated. Water year 2009 had near normal precipitation;2010 had late precipitation and snowmelt;and 2011 had 150% above normal precipitation. Surface waters were tested for pathogenic bacteria indicators fecal coliform, E. coli, and total coliform before and after cattle were released onto summer grazing allotments. Water samples were collected from meadow stream sites up to 6 weeks before and up to 6 weeks after cattle grazing began. Streams passing through ungrazed meadow served as controls. Eight sample sites were between 1694 m and 2273 m in elevation;one site was lower at 1145 m in elevation. Samples were transported within 6 hours to a water analysis laboratory, where samples were analyzed following standardized laboratory methods. Results showed that individual site and total mean concentrations of E. coli in surface waters were within regulatory standards before cattle arrived during each of the 3 study years. After the beginning of grazing, mean E. coli counts increased as follows: 2009 from 8 to 240 CFU/100mL, 2010 from 7 to 561 CFU/10mL;2011 from 7 to 657 CFU/100mL (p < 0.05 all years). Total coliform bacteria and fecal coliform concentrations showed the same pattern. This study shows that cattle grazing in the high elevation Sierra Nevada results in a significant increase in indicator bacteria. This impact on the watersheds occurs despite widely variable annual climatic conditions.展开更多
Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and...Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and direction of changes in seagrass meadows remain unclear.This study aimed to provide a nationwide seagrass distribution map and explore the dynamic changes in seagrass population under global climate change.Simulation studies were performed using the modeling software MaxEnt with 58961 occurrence records and 27 marine environmental variables to predict the potential distribution of seagrasses and calculate the area.Seven environmental variables were excluded from the modeling processes based on a correlation analysis to ensure predicted suitability.The predicted area was 790.09 km^(2),which is much larger than the known seagrass distribution in China(87.65 km^(2)).By 2100,the suitable habitat of seagrass will shift northwest and increase to 923.62 km2.Models of the sum of the individual family under-pre-dicted the national distribution of seagrasses and consistently showed a downward trend in the future.Out of all environmental vari-ables,physical parameters(e.g.,depth,land distance,and sea surface temperature)contributed the most in predicting seagrass distri-butions,and nutrients(e.g.,nitrate,phosphate)ranked among the key influential predictors for habitat suitability in our study area.This study is the first effort to fill a gap in understanding the distribution of seagrasses in China.Further studies using modeling and biological/ecological approaches are warranted.展开更多
On the basis of multifaceted investigations of approximately 600 phytosociological surveys of foxtail meadows taken in years 2002-2012 in river valleys with the assistance of the Braun-Blanquet method, the authors car...On the basis of multifaceted investigations of approximately 600 phytosociological surveys of foxtail meadows taken in years 2002-2012 in river valleys with the assistance of the Braun-Blanquet method, the authors carried out evaluation of the floristic composition with respect to phytosociological structure, floristic variability, degree of synanthropisation and life form structures. In addition, they ascertained the dependence of floristic variability of Alopecuretum pratensis phytocenoses on site conditions determined using： the phytoindication method and the laboratory analyses assessed the soil content of available forms of P and K and of Mg. The greatest areas among the recognised syntaxons are taken up by patches of a typical sub-association developed in fresh sites on soils of lightly acid reaction and moderate nitrogen availability. Floristic variability of Alopecuretum pratensis is characterised by： presence in the phytosociological structure of species characteristic for other syntaxons, floristic abundance and botanical structure, domination of species of the 1 st and 2nd degree of stability, high proportion of synanthropic species, values of the floristic diversity index （H＇）, natural and fodder score values. Geobotanical variability of foxtail meadows confirms difficulties with unequivocal determination of the systematic position of the Alopecuretum pratensis association.展开更多
Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing e...Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon （SOC） and soil total nitrogen （STN） storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass （AGB）, belowground biomass （BGB）, SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation （MAP）. Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer （10 cm） after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversitv conservation.展开更多
Potentilla fruticosascrub, Kobresia humilismeadow and Kobresia tibeticameadow are widely distributed on the Qinghai-Tibet Plateau. During the grass exuberance period from 3 July to 4 September, based on close chamber-...Potentilla fruticosascrub, Kobresia humilismeadow and Kobresia tibeticameadow are widely distributed on the Qinghai-Tibet Plateau. During the grass exuberance period from 3 July to 4 September, based on close chamber-GC method, a study on CO 2 emissions from different treatments was conducted in these meadows at Haibei research station, CAS. Results indicated that mean CO 2 emission rates from various treatments were 672.09±152.37 mgm -2 h -1 for FC (grass treatment); 425.41±191.99 mgm -2 h -1 for FJ (grass exclusion treatment); 280.36±174.83 mgm -2 h -1 for FL (grass and roots exclusion treatment); 838.95±237.02 mgm -2 h -1 for GG (scrub+grass treatment); 528.48±205.67 mgm -2 h -1 for GC (grass treatment); 268.97±99.72 mgm -2 h -1 for GL (grass and roots exclusion treatment); and 659.20±94.83 mgm -2 h -1 for LC (grass treatment), respectively (FC, FJ, FL, GG, GC, GL, LC were the Chinese abbreviation for various treatments). Furthermore, Kobresia humilismeadow, Potentilla fruticosascrub meadow and Kobresia tibeticameadow differed greatly in average CO 2 emission rate of soil-plant system, in the order of GG>FC>LC>GC. Moreover, in Kobresia humilismeadow, heterotrophic and autotrophic respiration accounted for 42% and 58% of the total respiration of soil-plant system respectively, whereas, in Potentilla fruticosascrub meadow, heterotrophic and autotrophic respiration accounted for 32% and 68% of total system respiration from GG; 49% and 51% from GC. In addition, root respiration from Kobresia humilismeadow approximated 145 mgCO 2 m -2 h -1 , contributed 34% to soil respiration. During the experiment period, Kobresia humilismeadow and Potentilla fruticosascrub meadow had a net carbon fixation of 111.11 gm -2 and 243.89 gm -2 , respectively. Results also showed that soil temperature was the main factor which influenced CO 2 emission from alpine meadow ecosystem, significant correlations were found between soil temperature at 5 cm depth and CO 2 emission from GG, GC, FC and FJ treatments. In addition, soil moisture may be the inhibitory factor of CO 2 emission from Kobresia tibeticameadow, and more detailed analyses should be done in further research.展开更多
Steller chamaejasme L. （S. chamaejasme for short） is one of the most noxious unpalatable weeds in China, which has been frequently reported its negative interaction （i.e. competition and allelopathy） with other he...Steller chamaejasme L. （S. chamaejasme for short） is one of the most noxious unpalatable weeds in China, which has been frequently reported its negative interaction （i.e. competition and allelopathy） with other herbaceous species in grasslands. This study compared species diversity, biomass and sexual reproduction of herbaceous plants in meadows with S. chamaejasme and in open meadows without S. ehamaejasme in overgrazing meadows on the Tibetan Plateau in China to determine whether positive facilitation exist between S. chamaejasme and other herbaceous species under livestock＇s overgrazing. The results showed that there are more herbaceous species in meadows with S. chamaejasme than those in open meadows （35s and30s, respectively）. Diversity index and above-ground biomass were also significantly higher in meadows with S. charnaejasme. There were 39% （11/28） of all species with sexual reproduction found in meadows with S. charnaejasme, which was 7 times more than those in open meadows. Our study showed that S. charnaejasme could provide biotic refuge for neighboring plants and preserve plant diversity from livestock＇s overgrazing in alpine meadows on the Tibetan Plateau. It also suggested that inter-specific facilitation between S. charnaejasme and other herbaceous species may play a key role in overgrazing alpine meadows.展开更多
[ Objective ] The paper was to understand the characteristics of plant communities in three kinds of typical alpine meadows in Haibei Region, Qinghai Province. [ Method] The characteristics and diversity of plant comm...[ Objective ] The paper was to understand the characteristics of plant communities in three kinds of typical alpine meadows in Haibei Region, Qinghai Province. [ Method] The characteristics and diversity of plant communities in typical alpine meadow, including Kobresia humilis, PotentiUafruticose and Kobresia menyuanica, were studied, with Menyuan studfarm in Haibei region of Qinghai Province as an example. [ Result] Results showed that the three kinds of plant communities in alpine meadows presented complex structure; the diversity index had close relationship with the evenness index; there were fewer common species and higher species replacement rate among different alpine meadow communities ; the aboveground biomass of K. humilis alpine meadow was 1.62 and 1.69 times of P. fruticose and K. menyuanica meadows, respectively; the underground biomass mainly distributed in the 0 - 10 cm soil layer, and the vertical spatial distribution structure was ＂T＂ type; the aboveground and underground biomass were negatively correlated. [ Conclusion] The paper will provide basis for protection and further use of different grassland plant communities in Haibei Region, Qinghai Province.展开更多
Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems. A field soil survey was conducted to compare microbial biomass carbon （Cmin） and soil fauna communities ...Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems. A field soil survey was conducted to compare microbial biomass carbon （Cmin） and soil fauna communities in the two main grassland management systems in subalpine regions of Yunnan Province, China： perennial grazing currently practiced due to increasing herd sizes and traditional seasonal grazing. A three-year exclosure experiment was then conducted to further compare the effects of different grazing practices, including treatments of no mowing, perennial grazing （NM ＋ G）, mowing followed by seasonal grazing （M ＋ G）, mowing and no grazing （M ＋ NG）, and no mowing or grazing （NM ＋ NG）. The comparative survey result revealed that Cmin and total density of soil fauna were significantly lower at a perennially grazed site than at a seasonally grazed site. The experiment results showed that in comparison to non-grazing treatments （M ＋ NG and NM ＋ NG）, grazing （NM ＋ G and M ＋ G） reduced total fauna density （by 150 individuals m-2） and the number of taxonomic groups present （by 0.32 taxa m-2）. Mowing decreased Cmin （by 0.31 mg g-l）. Furthermore, the NM ＋ G treatment （perennial grazing） had the lowest density of Collembola （16.24 individuals m-2）, one of the two most common taxonomic groups, although other taxonomic groups responded differently to the treatments. Treatment effects on soil fauna were consistent with those on above-ground grasses, in which C：N ratios were greatly reduced by grazing, with this effect being the greatest for the NM ＋ G treatment. In contrast, different grazing treatments had little effect on C：N ratio of soil. Furthermore, the traditional grazing method （mowing followed by seasonal grazing） may have less severe effects on some taxonomic groups than perennial grazing. Therefore, an appropriate management should aim to protect soil fauna and microbes in this area from over-grazing and against further degradation.展开更多
Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradient...Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradients in subalpine meadow ecosystems. To reveal the elevational patterns of warming effects on plant biodiversity, community structure, productivity, and soil properties, we conducted a warming experiment using open-top chambers from August 2019 to August 2022 at high(2764 m a. s. l.), medium(2631 m a. s. l.), and low(2544 m a. s. l.) elevational gradients on a subalpine meadow slope of Mount Wutai, Northern China. Our results showed that three years of warming significantly increased topsoil temperature but significantly decreased topsoil moisture at all elevations(P<0.05), and the percentage of increasing temperature and decreasing moisture both gradually raised with elevation lifting. Warming-induced decreasing proportions of soil organic carbon(SOC, by 19.24%), and total nitrogen(TN, by 24.56%) were the greatest at high elevational gradients. Experimental warming did not affect topsoil C: N, p H, NO_(3)^(-)-N, or NH_(4)^(+)-N at the three elevational gradients. Warming significantly increased species richness(P<0.01) and Shannon-Weiner index(P<0.05) at low elevational gradients but significantly decreased belowground biomass(P<0.05) at a depth of 0–10 cm at three elevational gradients. Warming caused significant increases in the aboveground biomass in the three elevational plots. Warming significantly increased the aboveground biomass of graminoids in medium(by 92.47%) and low(by 98.25%) elevational gradients, that of sedges in high(by 72.44%) and medium(by 57.16%) elevational plots, and that of forbs in high(by 75.88%), medium(by 34.38%), and low(by 74.95%) elevational plots. Species richness had significant linear correlations with SOC, TN, and C: N(P<0.05), but significant nonlinear responses to soil temperature and soil moisture in the warmed treatment(P<0.05). The warmed aboveground biomass had a significant nonlinear response to soil temperature and significant linear responses to soil moisture(P<0.05). This study provided evidence that altitude is a factor in sensitivity to climate warming, and these different parameters(e.g., plant species richness, Shannon-Weiner index, soil temperature, soil moisture, SOC, and TN) can be used to measure this sensitivity.展开更多
[Objective] To investigate the relationship between the grassland caterpillar with different grades and the structure of alpine Kobresia meadow or soil feature. [Method] A total of 10 plots （20.00 m × 20.00 m） ...[Objective] To investigate the relationship between the grassland caterpillar with different grades and the structure of alpine Kobresia meadow or soil feature. [Method] A total of 10 plots （20.00 m × 20.00 m） were chosen. In each plot, five smaller plots （5.00 m × 5.00 m） were randomly selected and six sample plots （0.25 m × 0.25 m） were then selected in each smaller plot. The biomass, vegetation height, grasslayer thickness, bare land area, soil moisture and total vegetation cover degree were determined. Data were analyzed statistically by Excel 2003 and SPSS 13.0 software. [ Result] There was a significant difference （P 〈 0.05） between the grassland caterpillars at different hazard grades and the structure of alpine Kobresia meadow or soil properties. [ Conclusion] With the increase of grassland caterpillar density, the plant community structure of alpine Kobresia meadows changes from sedge family-dominant community to the forbs-dominant community.展开更多
Three alpine meadows were chosen from the eastern margin of the Qilian Mountain：Polygonum viviparum meadow（P）,Stipa capillata grassland（S）and Rhododendron simsii shrub meadow（R）;LI-8100 A soil CO2 flux auto-mon...Three alpine meadows were chosen from the eastern margin of the Qilian Mountain：Polygonum viviparum meadow（P）,Stipa capillata grassland（S）and Rhododendron simsii shrub meadow（R）;LI-8100 A soil CO2 flux auto-monitoring system and lab analysis were applied to analyze the soil organic carbon density,dynamics of carbon flux,and their relationship with environmental factors.The results showed that different vegetations varied greatly in soil organic carbon density：R 〉 S 〉 P,and the soil carbon density reduced with the increasing depth;soil CO2flux：S 〉 P 〉 R,and sample plot P and S showed unimodal changes.The peak values appeared at 14：00-15：00 p.m.;soil CO2 flux was negatively correlated with near-ground air humidity and carbon content,positively correlated with soil temperature and near-ground air temperature,and showed no obvious correlation with soil moisture.展开更多
Alpine meadows of the Qinghai-Tibetan Plateau(QTP)are experiencing severe degradation due to intensified human activity and climate changes.However,there has been litle attention paid to the effects of different grazi...Alpine meadows of the Qinghai-Tibetan Plateau(QTP)are experiencing severe degradation due to intensified human activity and climate changes.However,there has been litle attention paid to the effects of different grazing practices on the soil hydrological properties of alpine meadows.In this study,three grazing practices were established in an alpine Kobresia meadow:free grazing,reduced grazing and grazing exclusion.We found that the 0-10 cm soil water retention capacity(SWR)and plant available water content(AWC)in grazing exclusion treatment were higher than that in reduced or free grazing treatments,whereas the 20-40 cm SWR and AWC display the opposite pattern.The AWC and SWR variations were closely related to soil properties,and the redundancy analysis showed that SWR and AWC were positive related to soil organic matter(SOM),total porosity(TP)and capillary porosity(CP),but were negative correlated with soil bulk density(BD),clay and silt content.Structural equation modeling found that SOM was identified as the most important factor affecting SWR,and CP was the key factor influencing AWC.Therefore,the higher O-10 cm SWR and AWC in grazing exclusion treatment may be attributed to its higher SOM and CP,respectively.Furthermore,root biomass can affect SWR and AWC through altering BD and SOM.Our study suggests that the response of soil hydrological properties to grazing practices was different,grazing exclusion only increase topsoil water retention capacity but not favor deep soil water retention capacity.展开更多
Background Grassland degradation decreases the capacity of soil carbon sequestration,while the supplementation of exogenous organic matter enhances the soil priming effect(PE)and affects the carbon cycle in the soil.T...Background Grassland degradation decreases the capacity of soil carbon sequestration,while the supplementation of exogenous organic matter enhances the soil priming effect(PE)and affects the carbon cycle in the soil.The excrements of Tibetan sheep(Ovis aries)and plateau pika(Ochotona curzoniae)play an important role in soil carbon cycling.Therefore,they were used to enrich alpine meadow soils degraded to different levels after incubation at 20℃for up to 45 days.The PE was analyzed using the natural13C isoto pe tracer method in relation to the alpine meadow soil properties.Results The supplementation of the two kinds of excrement significantly increased soil PE accumulation and soil carbon sequestration.Of the two,Tibetan sheep excrement achieved a better effect.Compared with non-degraded alpine meadow soil,severely degraded alpine meadow soil had significantly different PE,but the PE of lightly and moderately degraded meadow soil was not significantly different from each other.Structural equation modelling shows that total nitrogen(TN),soil organic carbon(SOC),β-1,4-N-acetylaminoglucosidase(NAG),β-1,4-glucosidase(βG),pH,and microbial biomass carbon(MBC)are the main factors affecting PE.In particular,TN directly negatively affected PE,SOC and the NO_(3)^(-)-N:NH_(4)^(+)-N ratio indirectly affected PE by affecting soil enzyme activity and MBC.Conclusions This study demonstrates that the supplement of animal excrements can improve the extracellular enzyme activity and nitrogen content in soils,which is conducive to PE and net carbon balance.Supplementation of both Tibetan sheep and plateau pika excrements can effectively enhance soil pH,further increase microbial biomass and extracellular enzyme activity,and improve soil fe rtility and carbon sequestration ability of se riously degraded alpine meadow soil.The NO_(3)^(-)-N:NH_(4)^(+)-N ratio and enzyme activity in plateau pika excrement were higher than those in Tibetan sheep excrement,which promote the soil PE in alpine meadows.The findings of this study provide theoretical evidence for the rational utilization of the excrements in the alpine meadow with different levels of degradation.展开更多
Aims Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions.However,temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because so...Aims Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions.However,temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because soil water condition also plays an important role in mediating phenology.Methods We used growing degree day(GDD)model and growing season index(GSI)model,coupling minimum temperature(T_(min))with soil moisture(SM)to explore the influence of heat requirement and hydroclimatic interaction on the start of carbon uptake period(SCUP)and net ecosystem productivity(NEP)in two alpine meadows with different precipitation regimes on the Qinghai-Tibet Plateau(QTP).One is the water-limited alpine steppe-meadow,and the other is the temperature-limited alpine shrub-meadow.Important Findings We observed two clear patterns linking GDD and GSI to SCUP:SCUP was similarly sensitive to variations in preseason GDD and GSI in the humid alpine shrub-meadow,while SCUP was more sensitive to the variability in preseason GSI than GDD in the semiarid alpine steppe-meadow.The divergent patterns indicated a balance of the limiting climatic factors between temperature and water availability.In the humid meadow,higher temperature sensitivity of SCUP could maximize thermal benefit without drought stress,as evidenced by the stronger linear correlation coefficient(R2)and Akaike’s information criterion(AIC)between observed SCUPs and those of simulated by GDD model.However,greater water sensitivity of SCUP could maximize the benefit of water in semiarid steppe-meadow,which is indicated by the stronger R2 and AIC between observed SCUPs and those of simulated by GSI model.Additionally,although SCUPs were determined by GDD in the alpine shrub-meadow ecosystem,NEP was both controlled by accumulative GSI in two alpine meadows.Our study highlights the impacts of hydroclimatic interaction on spring carbon flux phenology and vegetation productivity in the humid and semiarid alpine ecosystems.The results also suggest that water,together with temperature should be included in the models of phenology and carbon budget for alpine ecosystems in semiarid regions.These fi ndings have important implications for improving vegetation phenology models,thus advancing our understanding of the interplay between vegetation phenology,productivity and climate change in future.展开更多
Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the im-portance of specie...Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the im-portance of species composition, species richness, the type of different growth forms, and plant bio-mass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, her-baceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a de-crease from 13196.96±719.69 g/m2 in the sedge-dominated K. tibetica swamp to 2869.58±147.52 g/m2 in the forb and sedge dominated K. pygmaea meadow, and to 2153.08±141.95 g/m2 in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of below-ground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P<0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P<0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P<0.05); belowground biomass was positively correlated with soil moisture (P<0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was posi-tively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribu-tion of biomass coincided with soil moisture and edaphic gradient in alpine meadows.展开更多
From 30 June to 24 September in 2003 ecosystem respiration （Re） in two alpine meadows on the Tibetan Plateau were measured using static chamber- and gas chromatography- （GC） based techniques. Simultaneously, plant...From 30 June to 24 September in 2003 ecosystem respiration （Re） in two alpine meadows on the Tibetan Plateau were measured using static chamber- and gas chromatography- （GC） based techniques. Simultaneously, plant removal treatments were set to partition Re into plant autotrophic respiration （Ra） and microbial heterotrophic respiration （Rh）. Results indicated that Re had clear diurnal and seasonal variation patterns in both of the meadows. The seasonal variability of Re at both meadow sites was caused mainly by changes in Ra, rather than Rh. Moreover, atthe Kobresia humilis meadow site （K_site）, Ra and Rh accounted for 54% and 46% of Re, respectively. While at the Potentilla fruticosa scrub meadow （P_site）, the counterparts accounted for 61% and 39%, respectively. T test showed that there was significant difference in Re rates between the two meadows （t = 2.387, P = 0.022）. However, no significant difference was found in Rh rates, whereas a significant difference was observed in Ra rates between the two meadows. Thus, the difference in Re rate between the two meadows was mainly attributed to plant autotrophic respirations. During the growing season, the two meadows showed relatively low Q10 values, suggesting that Re, especially Rh was not sensitive to temperature variation in the growing season. Additionally, Re and Rh at the K_site, as well as Rh at the Psite was negatively correlated with soil moisture, indicating that soil moisture would also play an important role in respirations.展开更多
Aims Kobresia meadows,the dominant species of which differ in different habitats,cover a large area of alpine grassland on the QinghaiTibetan Plateau and act as potential CO_(2) sinks.Kobresia meadows with different d...Aims Kobresia meadows,the dominant species of which differ in different habitats,cover a large area of alpine grassland on the QinghaiTibetan Plateau and act as potential CO_(2) sinks.Kobresia meadows with different dominant species may differ in carbon sink strength.We aimed to test the hypothesis and to clarify the differences in CO_(2) sink strength among three major Kobresia meadows on the plateau and the mechanisms underlying these differences.Methods We measured the net ecosystem exchange flux(NEE),ecosystem respiration flux(ER),aboveground biomass(AGB)and environmental variables in three Kobresia meadows,dominated by K.pygmaea,K.humilis,or K.tibetica,respectively,in Haibei,Qinghai.NEE and ER were measured by a closed-chamber method.Environmental variables,including photosynthetic photon flux density(PPFD),air and soil temperature and air and soil moisture,were monitored during the above flux measurements.Important findings The measured peak AGB increased with soil water content and was 365,402 and 434 g dry weight m2 for K.pygmaea,K.humilis and K.tibetica meadow,respectively.From the maximum ecosystem photosynthetic rate in relation to PPFD measured during the growing season,we estimated gross ecosystem photosynthetic potential(GEPmax)as 22.2,29.9 and 37.8 lmol CO_(2) m2 s1 for K.pygmaea,K.humilis and K.tibetica meadow,respectively.We estimated the respective gross primary production(GPP)values as 799,1063 and 1158 g C m^(-2) year^(-1) and ER as 722,914 and 1011 g C m^(-2) year^(-1).Average net ecosystem production(NEP)was estimated to be 76.9,149.4 and 147.6 g C m^(-2) year^(-1) in K.pygmaea,K.humilis and K.tibetica meadows,respectively.The results indicate that(i)the three meadows were CO_(2) sinks during the study period and(ii)Kobresia meadows dominated by different species can differ considerably in carbon sink strength even under the same climatic conditions,which suggests the importance of characterizing spatial heterogeneity of carbon dynamics in the future.展开更多
Aims Grasslands used for animal husbandry are chosen depending on the nutritive values of dominant herbage species.However,the influence of grazing in combination with precipitation and growing season on the nutritive...Aims Grasslands used for animal husbandry are chosen depending on the nutritive values of dominant herbage species.However,the influence of grazing in combination with precipitation and growing season on the nutritive values of dominant species has not been explicated.Methods To unveil the influence of the different grazing intensities on the nutritional values,an ecological study was formulated,namely fencing(G0),light grazing(G1),moderate grazing(G2)and high grazing(G3).This ambitious study was undertaken on the nutritive values of the four dominant species of herbage in an alpine meadow on the Qinghai-Tibet Plateau(QTP)during growing season(June–September)for two successive years,namely 2015(rainy year)and 2016(droughty year).Important Findings We found that(i)the nutritive value of Kobresia capillifolia,Polygonum viviparum and Caragana sinica was noticeably increased by grazing,but negligible effect on Potentilla fruticosa nutritive value was recorded.(ii)During the rainy year(2015),compared with G0,Polygonum viviparum and Potentilla fruticosa displayed 5.4 and 1.5%increases in the crude protein(CP)content and 8.5 and 2.4%increases in vitro true digestibility(IVTD),respectively,while the neutral detergent fibre(NDF)decreased by 13.5 and 0.9%,respectively.During the droughty year(2016),compared with G0,C.sinica and Potentilla fruticosa showed increases in the CP content by 4.3 and 1.3%and increases in the IVTD by 10.7 and 0.4%,respectively,during G3,while the NDF decreased by 6.0 and 1.0%,respectively.(iii)The nutritive values of all species were higher in the years when the rains were good.However,the nutritive values suffered heavily during drought conditions.Besides,the highest and lowest values of nutrition were detected in June and in September,respectively.The inter-seasonal and the inter-annual changes in the nutritional values of species were higher for K.capillifolia and Polygonum viviparum than for Potentilla fruticosa and C.sinica,suggesting that Potentilla fruticosa and C.sinica had higher water-use efficiency.(iv)Grazing clearly reduced the drought tolerance of three species and showed no effects on Potentilla fruticosa.(v)Grazing clearly increased the inter-month variation in the nutritional value of K.capillifolia and Polygonum viviparum but showed no effects on Potentilla fruticosa or C.sinica.Evidently,the grazing effects impacting the nutritional value of the dominant species of herbage exhibited conspicuous inter-annual and seasonal variations with species-specific influences and responses.Our findings are expected to have far-reaching implications enabling the authorities to arrive at strategic decisions and designing of relevant policies for the efficient management of the ecosystems ensuring the speed restoration of the QTP under severe grazing and extreme climatic circumstances.展开更多
基金supported by the Key Research and Development and Transformation Plan of Qinghai Provincial Science and Technology Department(2024-NK-137)the Qinghai Province Science and Technology Commissioner Special Project(2024-NK-P28).
文摘In recent years,many studies have focused on the effects of global climate warming and increased nitrogen deposition on the structure and function of grassland ecosystem.However,there are still significant uncertainties in the response mechanism of stability of plant community biomass in alpine meadows of the Qinghai-Xizang Plateau,China to these two major climate factors.Given this,based on field control experiments,this study systematically evaluated the effects of different levels of climate warming(W0(no warming),W1(air temperature increased by 0.47℃ or soil temperature increased by 0.61℃),W2(air temperature increased by 0.92℃ or soil temperature increased by 1.09℃),W3(air temperature increased by 1.44℃ or soil temperature increased by 1.95℃)),nitrogen deposition(N0(0 kg N/(hm^(2)·a)),N16(16 kg N/(hm^(2)·a)),and N32(32 kg N/(hm^(2)·a))),and their interactions on plant community biomass and its temporal stability,and explored its potential regulatory mechanisms.The results showed that the biomass of total community,Gramineae,and dominant species increased significantly with increasing temperature,but the biomass of common and rare species decreased significantly.Nitrogen deposition also significantly promoted the biomass accumulation of community and gramineous plants.Under the treatment of W3N32,the biomass of plant community,Gramineae,and dominant species reached the highest values,indicating that there was a synergistic effect under this treatment.Structural equation model showed that increasing temperature significantly decreased the stability of plant community biomass by reducing the stability of grass and dominant species biomass and weakening species asynchronism.Interaction of increased nitrogen deposition and temperature increased the biomass fluctuation of grass functional group,thus amplifying its negative influence on community stability.More attention should be paid to the response and regulatory mechanisms of dominant species and functional groups under global climate change.This study provides a theoretical basis for revealing the stability maintenance mechanism of alpine grassland and also provides scientific support for the development of future grassland ecosystem management and assessment.
基金supported by the National Forage Industry Technology System Program (CARS-34)Grassland Ecological Restoration and Management Science and Technology Support Project of Gansu Forestry and Grassland Bureau (GSAU-TSYF-2021-011)。
文摘In recent decades, global climate change and overgrazing have led to severe degradation of alpine meadows. Understanding the changes in soil characteristics and vegetation communities in alpine meadows with different degrees of degradation is helpful to reveal the mechanism of degradation process and take the remediation measures effectively. This study analyzed the changes in vegetation types and soil characteristics and their interrelationships under three degradation degrees, i.e., non-degradation(ND),moderate degradation(MD), and severe degradation(SD) in the alpine meadows of northeastern Qinghai-Xizang Plateau, China through the long-term observation. Results showed that the aggressive degradation changed the plant species, with the vegetation altering from leguminous and gramineous to forbs and harmful grasses. The Pielou evenness and Simpson index increased by 24.58% and 7.01%,respectively, the Shannon-Wiener index decreased by 17.52%, and the species richness index remained constant. Soil conductivity, soil organic matter, total potassium, available potassium, and porosity declined.However, the number of vegetation species increased in MD. Compared with ND, the plant diversity in MD enhanced by 8.33%, 8.69%, and 7.41% at family, genus, and species levels, respectively. In conclusion,changes in soil properties due to degradation can significantly influence the condition of above-ground vegetation. Plant diversity increases, which improves the structure of belowground network. These findings may contribute to designing better protection measures of alpine meadows against global climate change and overgrazing.
文摘The impact of summer cattle grazing on water quality during three very different climatic years in the Sierra Nevada was investigated. Water year 2009 had near normal precipitation;2010 had late precipitation and snowmelt;and 2011 had 150% above normal precipitation. Surface waters were tested for pathogenic bacteria indicators fecal coliform, E. coli, and total coliform before and after cattle were released onto summer grazing allotments. Water samples were collected from meadow stream sites up to 6 weeks before and up to 6 weeks after cattle grazing began. Streams passing through ungrazed meadow served as controls. Eight sample sites were between 1694 m and 2273 m in elevation;one site was lower at 1145 m in elevation. Samples were transported within 6 hours to a water analysis laboratory, where samples were analyzed following standardized laboratory methods. Results showed that individual site and total mean concentrations of E. coli in surface waters were within regulatory standards before cattle arrived during each of the 3 study years. After the beginning of grazing, mean E. coli counts increased as follows: 2009 from 8 to 240 CFU/100mL, 2010 from 7 to 561 CFU/10mL;2011 from 7 to 657 CFU/100mL (p < 0.05 all years). Total coliform bacteria and fecal coliform concentrations showed the same pattern. This study shows that cattle grazing in the high elevation Sierra Nevada results in a significant increase in indicator bacteria. This impact on the watersheds occurs despite widely variable annual climatic conditions.
基金supported by the National Key R&D Program of China(No.2019YFC1408405-02)the National Natural Science Foundation of China(No.6207070555)the Youth Foundation of the Shandong Academy of Sciences(No.2019QN0026).
文摘Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and direction of changes in seagrass meadows remain unclear.This study aimed to provide a nationwide seagrass distribution map and explore the dynamic changes in seagrass population under global climate change.Simulation studies were performed using the modeling software MaxEnt with 58961 occurrence records and 27 marine environmental variables to predict the potential distribution of seagrasses and calculate the area.Seven environmental variables were excluded from the modeling processes based on a correlation analysis to ensure predicted suitability.The predicted area was 790.09 km^(2),which is much larger than the known seagrass distribution in China(87.65 km^(2)).By 2100,the suitable habitat of seagrass will shift northwest and increase to 923.62 km2.Models of the sum of the individual family under-pre-dicted the national distribution of seagrasses and consistently showed a downward trend in the future.Out of all environmental vari-ables,physical parameters(e.g.,depth,land distance,and sea surface temperature)contributed the most in predicting seagrass distri-butions,and nutrients(e.g.,nitrate,phosphate)ranked among the key influential predictors for habitat suitability in our study area.This study is the first effort to fill a gap in understanding the distribution of seagrasses in China.Further studies using modeling and biological/ecological approaches are warranted.
文摘On the basis of multifaceted investigations of approximately 600 phytosociological surveys of foxtail meadows taken in years 2002-2012 in river valleys with the assistance of the Braun-Blanquet method, the authors carried out evaluation of the floristic composition with respect to phytosociological structure, floristic variability, degree of synanthropisation and life form structures. In addition, they ascertained the dependence of floristic variability of Alopecuretum pratensis phytocenoses on site conditions determined using： the phytoindication method and the laboratory analyses assessed the soil content of available forms of P and K and of Mg. The greatest areas among the recognised syntaxons are taken up by patches of a typical sub-association developed in fresh sites on soils of lightly acid reaction and moderate nitrogen availability. Floristic variability of Alopecuretum pratensis is characterised by： presence in the phytosociological structure of species characteristic for other syntaxons, floristic abundance and botanical structure, domination of species of the 1 st and 2nd degree of stability, high proportion of synanthropic species, values of the floristic diversity index （H＇）, natural and fodder score values. Geobotanical variability of foxtail meadows confirms difficulties with unequivocal determination of the systematic position of the Alopecuretum pratensis association.
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05060700)Postdoctoral Science Foundation of China(No.2013M530716)
文摘Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon （SOC） and soil total nitrogen （STN） storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass （AGB）, belowground biomass （BGB）, SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation （MAP）. Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer （10 cm） after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversitv conservation.
文摘Potentilla fruticosascrub, Kobresia humilismeadow and Kobresia tibeticameadow are widely distributed on the Qinghai-Tibet Plateau. During the grass exuberance period from 3 July to 4 September, based on close chamber-GC method, a study on CO 2 emissions from different treatments was conducted in these meadows at Haibei research station, CAS. Results indicated that mean CO 2 emission rates from various treatments were 672.09±152.37 mgm -2 h -1 for FC (grass treatment); 425.41±191.99 mgm -2 h -1 for FJ (grass exclusion treatment); 280.36±174.83 mgm -2 h -1 for FL (grass and roots exclusion treatment); 838.95±237.02 mgm -2 h -1 for GG (scrub+grass treatment); 528.48±205.67 mgm -2 h -1 for GC (grass treatment); 268.97±99.72 mgm -2 h -1 for GL (grass and roots exclusion treatment); and 659.20±94.83 mgm -2 h -1 for LC (grass treatment), respectively (FC, FJ, FL, GG, GC, GL, LC were the Chinese abbreviation for various treatments). Furthermore, Kobresia humilismeadow, Potentilla fruticosascrub meadow and Kobresia tibeticameadow differed greatly in average CO 2 emission rate of soil-plant system, in the order of GG>FC>LC>GC. Moreover, in Kobresia humilismeadow, heterotrophic and autotrophic respiration accounted for 42% and 58% of the total respiration of soil-plant system respectively, whereas, in Potentilla fruticosascrub meadow, heterotrophic and autotrophic respiration accounted for 32% and 68% of total system respiration from GG; 49% and 51% from GC. In addition, root respiration from Kobresia humilismeadow approximated 145 mgCO 2 m -2 h -1 , contributed 34% to soil respiration. During the experiment period, Kobresia humilismeadow and Potentilla fruticosascrub meadow had a net carbon fixation of 111.11 gm -2 and 243.89 gm -2 , respectively. Results also showed that soil temperature was the main factor which influenced CO 2 emission from alpine meadow ecosystem, significant correlations were found between soil temperature at 5 cm depth and CO 2 emission from GG, GC, FC and FJ treatments. In addition, soil moisture may be the inhibitory factor of CO 2 emission from Kobresia tibeticameadow, and more detailed analyses should be done in further research.
基金funded by the National Natural Science Foundation of China (Grant Nos. 31100360, 31200378, 31000233)
文摘Steller chamaejasme L. （S. chamaejasme for short） is one of the most noxious unpalatable weeds in China, which has been frequently reported its negative interaction （i.e. competition and allelopathy） with other herbaceous species in grasslands. This study compared species diversity, biomass and sexual reproduction of herbaceous plants in meadows with S. chamaejasme and in open meadows without S. ehamaejasme in overgrazing meadows on the Tibetan Plateau in China to determine whether positive facilitation exist between S. chamaejasme and other herbaceous species under livestock＇s overgrazing. The results showed that there are more herbaceous species in meadows with S. chamaejasme than those in open meadows （35s and30s, respectively）. Diversity index and above-ground biomass were also significantly higher in meadows with S. charnaejasme. There were 39% （11/28） of all species with sexual reproduction found in meadows with S. charnaejasme, which was 7 times more than those in open meadows. Our study showed that S. charnaejasme could provide biotic refuge for neighboring plants and preserve plant diversity from livestock＇s overgrazing in alpine meadows on the Tibetan Plateau. It also suggested that inter-specific facilitation between S. charnaejasme and other herbaceous species may play a key role in overgrazing alpine meadows.
基金Supported by Technology R&D Program"Research and Demonstration of Fragile Ecological Restoration Technology for the Tibetan Plateau"(2013BAC04B02)Sub Project of National Key Technology R&D Program"Health Assessment Technology for Typical Fragile Ecosystem in the Tibetan Plateau"(2013BAC04B02-05)National Natural Science Foundation of China(31160120)
文摘[ Objective ] The paper was to understand the characteristics of plant communities in three kinds of typical alpine meadows in Haibei Region, Qinghai Province. [ Method] The characteristics and diversity of plant communities in typical alpine meadow, including Kobresia humilis, PotentiUafruticose and Kobresia menyuanica, were studied, with Menyuan studfarm in Haibei region of Qinghai Province as an example. [ Result] Results showed that the three kinds of plant communities in alpine meadows presented complex structure; the diversity index had close relationship with the evenness index; there were fewer common species and higher species replacement rate among different alpine meadow communities ; the aboveground biomass of K. humilis alpine meadow was 1.62 and 1.69 times of P. fruticose and K. menyuanica meadows, respectively; the underground biomass mainly distributed in the 0 - 10 cm soil layer, and the vertical spatial distribution structure was ＂T＂ type; the aboveground and underground biomass were negatively correlated. [ Conclusion] The paper will provide basis for protection and further use of different grassland plant communities in Haibei Region, Qinghai Province.
基金supported by the Biogeochemistry Laboratory of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, the National Natural Science Foundation of China (Nos. 40671103 and 41271278)the Innovative Program of Chinese Academy of Sciences- “The Effects of Different Land Use on Biodiversity in Northwest of Yunnan, China” (No. KSCX2-SW-123-5)
文摘Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems. A field soil survey was conducted to compare microbial biomass carbon （Cmin） and soil fauna communities in the two main grassland management systems in subalpine regions of Yunnan Province, China： perennial grazing currently practiced due to increasing herd sizes and traditional seasonal grazing. A three-year exclosure experiment was then conducted to further compare the effects of different grazing practices, including treatments of no mowing, perennial grazing （NM ＋ G）, mowing followed by seasonal grazing （M ＋ G）, mowing and no grazing （M ＋ NG）, and no mowing or grazing （NM ＋ NG）. The comparative survey result revealed that Cmin and total density of soil fauna were significantly lower at a perennially grazed site than at a seasonally grazed site. The experiment results showed that in comparison to non-grazing treatments （M ＋ NG and NM ＋ NG）, grazing （NM ＋ G and M ＋ G） reduced total fauna density （by 150 individuals m-2） and the number of taxonomic groups present （by 0.32 taxa m-2）. Mowing decreased Cmin （by 0.31 mg g-l）. Furthermore, the NM ＋ G treatment （perennial grazing） had the lowest density of Collembola （16.24 individuals m-2）, one of the two most common taxonomic groups, although other taxonomic groups responded differently to the treatments. Treatment effects on soil fauna were consistent with those on above-ground grasses, in which C：N ratios were greatly reduced by grazing, with this effect being the greatest for the NM ＋ G treatment. In contrast, different grazing treatments had little effect on C：N ratio of soil. Furthermore, the traditional grazing method （mowing followed by seasonal grazing） may have less severe effects on some taxonomic groups than perennial grazing. Therefore, an appropriate management should aim to protect soil fauna and microbes in this area from over-grazing and against further degradation.
基金carried out in the framework of the 1331 Project of Cultural Ecology Collaborative Innovation Center in Wutai Mountain (00000342)co-financed by Program for the Philosophy and Social Sciences Research of Higher Learning Institutions of Shanxi (2022J027)+1 种基金Applied Basic Research Project of Shanxi Province (202203021221225)Basic Research Project of Xinzhou Science and Technology Bureau (20230501)。
文摘Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradients in subalpine meadow ecosystems. To reveal the elevational patterns of warming effects on plant biodiversity, community structure, productivity, and soil properties, we conducted a warming experiment using open-top chambers from August 2019 to August 2022 at high(2764 m a. s. l.), medium(2631 m a. s. l.), and low(2544 m a. s. l.) elevational gradients on a subalpine meadow slope of Mount Wutai, Northern China. Our results showed that three years of warming significantly increased topsoil temperature but significantly decreased topsoil moisture at all elevations(P<0.05), and the percentage of increasing temperature and decreasing moisture both gradually raised with elevation lifting. Warming-induced decreasing proportions of soil organic carbon(SOC, by 19.24%), and total nitrogen(TN, by 24.56%) were the greatest at high elevational gradients. Experimental warming did not affect topsoil C: N, p H, NO_(3)^(-)-N, or NH_(4)^(+)-N at the three elevational gradients. Warming significantly increased species richness(P<0.01) and Shannon-Weiner index(P<0.05) at low elevational gradients but significantly decreased belowground biomass(P<0.05) at a depth of 0–10 cm at three elevational gradients. Warming caused significant increases in the aboveground biomass in the three elevational plots. Warming significantly increased the aboveground biomass of graminoids in medium(by 92.47%) and low(by 98.25%) elevational gradients, that of sedges in high(by 72.44%) and medium(by 57.16%) elevational plots, and that of forbs in high(by 75.88%), medium(by 34.38%), and low(by 74.95%) elevational plots. Species richness had significant linear correlations with SOC, TN, and C: N(P<0.05), but significant nonlinear responses to soil temperature and soil moisture in the warmed treatment(P<0.05). The warmed aboveground biomass had a significant nonlinear response to soil temperature and significant linear responses to soil moisture(P<0.05). This study provided evidence that altitude is a factor in sensitivity to climate warming, and these different parameters(e.g., plant species richness, Shannon-Weiner index, soil temperature, soil moisture, SOC, and TN) can be used to measure this sensitivity.
基金funded by the grants from Basic Science and Research Special Fund for the State Level and Public Scientific Research Institute (Grassland Research Institute,Chinese Academy of Agricultural Sciences) and Wild Science Observation Testing Station of Alpine Meadow Grassland Resource and Ecotope of the Ministry of Agriculture
文摘[Objective] To investigate the relationship between the grassland caterpillar with different grades and the structure of alpine Kobresia meadow or soil feature. [Method] A total of 10 plots （20.00 m × 20.00 m） were chosen. In each plot, five smaller plots （5.00 m × 5.00 m） were randomly selected and six sample plots （0.25 m × 0.25 m） were then selected in each smaller plot. The biomass, vegetation height, grasslayer thickness, bare land area, soil moisture and total vegetation cover degree were determined. Data were analyzed statistically by Excel 2003 and SPSS 13.0 software. [ Result] There was a significant difference （P 〈 0.05） between the grassland caterpillars at different hazard grades and the structure of alpine Kobresia meadow or soil properties. [ Conclusion] With the increase of grassland caterpillar density, the plant community structure of alpine Kobresia meadows changes from sedge family-dominant community to the forbs-dominant community.
基金Sponsored by Natural Science Foundation of China(31360569)Key Laboratory of Grassland Ecosystem Program(CYZS-2011007)Modern Agricultural Technical System of Gansu Agricultural University CARS-35
文摘Three alpine meadows were chosen from the eastern margin of the Qilian Mountain：Polygonum viviparum meadow（P）,Stipa capillata grassland（S）and Rhododendron simsii shrub meadow（R）;LI-8100 A soil CO2 flux auto-monitoring system and lab analysis were applied to analyze the soil organic carbon density,dynamics of carbon flux,and their relationship with environmental factors.The results showed that different vegetations varied greatly in soil organic carbon density：R 〉 S 〉 P,and the soil carbon density reduced with the increasing depth;soil CO2flux：S 〉 P 〉 R,and sample plot P and S showed unimodal changes.The peak values appeared at 14：00-15：00 p.m.;soil CO2 flux was negatively correlated with near-ground air humidity and carbon content,positively correlated with soil temperature and near-ground air temperature,and showed no obvious correlation with soil moisture.
基金supported by the CAS"Light of West China"Program(grant no.xbzglzb2022031)the National Natural Science Foundation of China(grant no.U23A2002,42207524 and 32171650)+3 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(grant no.2019QzKK0405)Collaborative Innovation Center for ecological civilization from Hainan University(XTCX2022STC01 and XTCX2022STB07)Independent Initiated Project from Environment and Plant Protection Institute,Chinese Academy of Tropical Agriculture Sciences(hzs2024003)start-up funding from Hainan University[KYQD(ZR)-22085].
文摘Alpine meadows of the Qinghai-Tibetan Plateau(QTP)are experiencing severe degradation due to intensified human activity and climate changes.However,there has been litle attention paid to the effects of different grazing practices on the soil hydrological properties of alpine meadows.In this study,three grazing practices were established in an alpine Kobresia meadow:free grazing,reduced grazing and grazing exclusion.We found that the 0-10 cm soil water retention capacity(SWR)and plant available water content(AWC)in grazing exclusion treatment were higher than that in reduced or free grazing treatments,whereas the 20-40 cm SWR and AWC display the opposite pattern.The AWC and SWR variations were closely related to soil properties,and the redundancy analysis showed that SWR and AWC were positive related to soil organic matter(SOM),total porosity(TP)and capillary porosity(CP),but were negative correlated with soil bulk density(BD),clay and silt content.Structural equation modeling found that SOM was identified as the most important factor affecting SWR,and CP was the key factor influencing AWC.Therefore,the higher O-10 cm SWR and AWC in grazing exclusion treatment may be attributed to its higher SOM and CP,respectively.Furthermore,root biomass can affect SWR and AWC through altering BD and SOM.Our study suggests that the response of soil hydrological properties to grazing practices was different,grazing exclusion only increase topsoil water retention capacity but not favor deep soil water retention capacity.
基金supported by the National Natural Science Foundation of China(grant numbers U21A20191,U23A20159)the Northwest A&F University Student Innovation and Entrepreneurship Training Program Project(grant number S202310712513)
文摘Background Grassland degradation decreases the capacity of soil carbon sequestration,while the supplementation of exogenous organic matter enhances the soil priming effect(PE)and affects the carbon cycle in the soil.The excrements of Tibetan sheep(Ovis aries)and plateau pika(Ochotona curzoniae)play an important role in soil carbon cycling.Therefore,they were used to enrich alpine meadow soils degraded to different levels after incubation at 20℃for up to 45 days.The PE was analyzed using the natural13C isoto pe tracer method in relation to the alpine meadow soil properties.Results The supplementation of the two kinds of excrement significantly increased soil PE accumulation and soil carbon sequestration.Of the two,Tibetan sheep excrement achieved a better effect.Compared with non-degraded alpine meadow soil,severely degraded alpine meadow soil had significantly different PE,but the PE of lightly and moderately degraded meadow soil was not significantly different from each other.Structural equation modelling shows that total nitrogen(TN),soil organic carbon(SOC),β-1,4-N-acetylaminoglucosidase(NAG),β-1,4-glucosidase(βG),pH,and microbial biomass carbon(MBC)are the main factors affecting PE.In particular,TN directly negatively affected PE,SOC and the NO_(3)^(-)-N:NH_(4)^(+)-N ratio indirectly affected PE by affecting soil enzyme activity and MBC.Conclusions This study demonstrates that the supplement of animal excrements can improve the extracellular enzyme activity and nitrogen content in soils,which is conducive to PE and net carbon balance.Supplementation of both Tibetan sheep and plateau pika excrements can effectively enhance soil pH,further increase microbial biomass and extracellular enzyme activity,and improve soil fe rtility and carbon sequestration ability of se riously degraded alpine meadow soil.The NO_(3)^(-)-N:NH_(4)^(+)-N ratio and enzyme activity in plateau pika excrement were higher than those in Tibetan sheep excrement,which promote the soil PE in alpine meadows.The findings of this study provide theoretical evidence for the rational utilization of the excrements in the alpine meadow with different levels of degradation.
基金supported by the National Natural Science Foundation of China(31870406,41661144045)the State Key Research and Development Program(2016YFC0502001,2017YFA0604801).
文摘Aims Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions.However,temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because soil water condition also plays an important role in mediating phenology.Methods We used growing degree day(GDD)model and growing season index(GSI)model,coupling minimum temperature(T_(min))with soil moisture(SM)to explore the influence of heat requirement and hydroclimatic interaction on the start of carbon uptake period(SCUP)and net ecosystem productivity(NEP)in two alpine meadows with different precipitation regimes on the Qinghai-Tibet Plateau(QTP).One is the water-limited alpine steppe-meadow,and the other is the temperature-limited alpine shrub-meadow.Important Findings We observed two clear patterns linking GDD and GSI to SCUP:SCUP was similarly sensitive to variations in preseason GDD and GSI in the humid alpine shrub-meadow,while SCUP was more sensitive to the variability in preseason GSI than GDD in the semiarid alpine steppe-meadow.The divergent patterns indicated a balance of the limiting climatic factors between temperature and water availability.In the humid meadow,higher temperature sensitivity of SCUP could maximize thermal benefit without drought stress,as evidenced by the stronger linear correlation coefficient(R2)and Akaike’s information criterion(AIC)between observed SCUPs and those of simulated by GDD model.However,greater water sensitivity of SCUP could maximize the benefit of water in semiarid steppe-meadow,which is indicated by the stronger R2 and AIC between observed SCUPs and those of simulated by GSI model.Additionally,although SCUPs were determined by GDD in the alpine shrub-meadow ecosystem,NEP was both controlled by accumulative GSI in two alpine meadows.Our study highlights the impacts of hydroclimatic interaction on spring carbon flux phenology and vegetation productivity in the humid and semiarid alpine ecosystems.The results also suggest that water,together with temperature should be included in the models of phenology and carbon budget for alpine ecosystems in semiarid regions.These fi ndings have important implications for improving vegetation phenology models,thus advancing our understanding of the interplay between vegetation phenology,productivity and climate change in future.
基金Supported by the Hundred Talents Programs of the Chinese Academy of Sciencesthe National Natural Science Important Foundation of China (Grant No. 30730069)
文摘Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the im-portance of species composition, species richness, the type of different growth forms, and plant bio-mass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, her-baceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a de-crease from 13196.96±719.69 g/m2 in the sedge-dominated K. tibetica swamp to 2869.58±147.52 g/m2 in the forb and sedge dominated K. pygmaea meadow, and to 2153.08±141.95 g/m2 in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of below-ground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P<0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P<0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P<0.05); belowground biomass was positively correlated with soil moisture (P<0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was posi-tively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribu-tion of biomass coincided with soil moisture and edaphic gradient in alpine meadows.
基金Field Station Foundation In the Domain of Resource and Environment, CAS and GEF program (052456 and CHA-GS-Y-4)
文摘From 30 June to 24 September in 2003 ecosystem respiration （Re） in two alpine meadows on the Tibetan Plateau were measured using static chamber- and gas chromatography- （GC） based techniques. Simultaneously, plant removal treatments were set to partition Re into plant autotrophic respiration （Ra） and microbial heterotrophic respiration （Rh）. Results indicated that Re had clear diurnal and seasonal variation patterns in both of the meadows. The seasonal variability of Re at both meadow sites was caused mainly by changes in Ra, rather than Rh. Moreover, atthe Kobresia humilis meadow site （K_site）, Ra and Rh accounted for 54% and 46% of Re, respectively. While at the Potentilla fruticosa scrub meadow （P_site）, the counterparts accounted for 61% and 39%, respectively. T test showed that there was significant difference in Re rates between the two meadows （t = 2.387, P = 0.022）. However, no significant difference was found in Rh rates, whereas a significant difference was observed in Ra rates between the two meadows. Thus, the difference in Re rate between the two meadows was mainly attributed to plant autotrophic respirations. During the growing season, the two meadows showed relatively low Q10 values, suggesting that Re, especially Rh was not sensitive to temperature variation in the growing season. Additionally, Re and Rh at the K_site, as well as Rh at the Psite was negatively correlated with soil moisture, indicating that soil moisture would also play an important role in respirations.
基金Integrated Study for Terrestrial Carbon Management of Asia in the 21st Century Based on Scientific AdvancementsEarly Detection and Prediction of Climate Warming Based on the LongTerm Monitoring of Alpine Ecosystems on the Tibetan Plateau.
文摘Aims Kobresia meadows,the dominant species of which differ in different habitats,cover a large area of alpine grassland on the QinghaiTibetan Plateau and act as potential CO_(2) sinks.Kobresia meadows with different dominant species may differ in carbon sink strength.We aimed to test the hypothesis and to clarify the differences in CO_(2) sink strength among three major Kobresia meadows on the plateau and the mechanisms underlying these differences.Methods We measured the net ecosystem exchange flux(NEE),ecosystem respiration flux(ER),aboveground biomass(AGB)and environmental variables in three Kobresia meadows,dominated by K.pygmaea,K.humilis,or K.tibetica,respectively,in Haibei,Qinghai.NEE and ER were measured by a closed-chamber method.Environmental variables,including photosynthetic photon flux density(PPFD),air and soil temperature and air and soil moisture,were monitored during the above flux measurements.Important findings The measured peak AGB increased with soil water content and was 365,402 and 434 g dry weight m2 for K.pygmaea,K.humilis and K.tibetica meadow,respectively.From the maximum ecosystem photosynthetic rate in relation to PPFD measured during the growing season,we estimated gross ecosystem photosynthetic potential(GEPmax)as 22.2,29.9 and 37.8 lmol CO_(2) m2 s1 for K.pygmaea,K.humilis and K.tibetica meadow,respectively.We estimated the respective gross primary production(GPP)values as 799,1063 and 1158 g C m^(-2) year^(-1) and ER as 722,914 and 1011 g C m^(-2) year^(-1).Average net ecosystem production(NEP)was estimated to be 76.9,149.4 and 147.6 g C m^(-2) year^(-1) in K.pygmaea,K.humilis and K.tibetica meadows,respectively.The results indicate that(i)the three meadows were CO_(2) sinks during the study period and(ii)Kobresia meadows dominated by different species can differ considerably in carbon sink strength even under the same climatic conditions,which suggests the importance of characterizing spatial heterogeneity of carbon dynamics in the future.
基金Our research was funded by China’s Agricultural Research system(CARS-39-18).
文摘Aims Grasslands used for animal husbandry are chosen depending on the nutritive values of dominant herbage species.However,the influence of grazing in combination with precipitation and growing season on the nutritive values of dominant species has not been explicated.Methods To unveil the influence of the different grazing intensities on the nutritional values,an ecological study was formulated,namely fencing(G0),light grazing(G1),moderate grazing(G2)and high grazing(G3).This ambitious study was undertaken on the nutritive values of the four dominant species of herbage in an alpine meadow on the Qinghai-Tibet Plateau(QTP)during growing season(June–September)for two successive years,namely 2015(rainy year)and 2016(droughty year).Important Findings We found that(i)the nutritive value of Kobresia capillifolia,Polygonum viviparum and Caragana sinica was noticeably increased by grazing,but negligible effect on Potentilla fruticosa nutritive value was recorded.(ii)During the rainy year(2015),compared with G0,Polygonum viviparum and Potentilla fruticosa displayed 5.4 and 1.5%increases in the crude protein(CP)content and 8.5 and 2.4%increases in vitro true digestibility(IVTD),respectively,while the neutral detergent fibre(NDF)decreased by 13.5 and 0.9%,respectively.During the droughty year(2016),compared with G0,C.sinica and Potentilla fruticosa showed increases in the CP content by 4.3 and 1.3%and increases in the IVTD by 10.7 and 0.4%,respectively,during G3,while the NDF decreased by 6.0 and 1.0%,respectively.(iii)The nutritive values of all species were higher in the years when the rains were good.However,the nutritive values suffered heavily during drought conditions.Besides,the highest and lowest values of nutrition were detected in June and in September,respectively.The inter-seasonal and the inter-annual changes in the nutritional values of species were higher for K.capillifolia and Polygonum viviparum than for Potentilla fruticosa and C.sinica,suggesting that Potentilla fruticosa and C.sinica had higher water-use efficiency.(iv)Grazing clearly reduced the drought tolerance of three species and showed no effects on Potentilla fruticosa.(v)Grazing clearly increased the inter-month variation in the nutritional value of K.capillifolia and Polygonum viviparum but showed no effects on Potentilla fruticosa or C.sinica.Evidently,the grazing effects impacting the nutritional value of the dominant species of herbage exhibited conspicuous inter-annual and seasonal variations with species-specific influences and responses.Our findings are expected to have far-reaching implications enabling the authorities to arrive at strategic decisions and designing of relevant policies for the efficient management of the ecosystems ensuring the speed restoration of the QTP under severe grazing and extreme climatic circumstances.
