The response of N_(2)O emissions to nitrogen(N)addition is usually positive,but its response to phosphorus(P)addition varies,and the underlying mechanisms for the changes in N_(2)O emissions remain unclear.We conducte...The response of N_(2)O emissions to nitrogen(N)addition is usually positive,but its response to phosphorus(P)addition varies,and the underlying mechanisms for the changes in N_(2)O emissions remain unclear.We conducted field studies to examine the response of N_(2)O emissions to N and P addition over two years in three typical alpine grasslands,alpine meadow(AM),alpine steppe(AS),and alpine cultivated grassland(CG)on the Qinghai-Tibet Plateau(QTP).Our results showed consistent increases in N_(2)O emissions under N addition alone or with P addition,and insignificant change in N_(2)O emissions under P addition alone in all three grasslands.N addition increased N_(2)O emissions directly in AM,by lowering soil pH in AS,and by lowering abundance of denitrification genes in CG.N and P co-addition increased N_(2)O emissions in AM and AS but only showed an interactive effect in AM.P addition enhanced the increase in N_(2)O emissions caused by N addition mainly by promoting plant growth in AM.Overall,our results illustrate that short-term P addition cannot alleviate the stimulation of N_(2)O emissions by N deposition in alpine grassland ecosystems,and may even further stimulate N_(2)O emissions.展开更多
Understanding the vertical distribution patterns of soil microbial community and its driving factors in alpine grasslands in the humid regions of the Tibet Plateau might be of great significance for predicting the soi...Understanding the vertical distribution patterns of soil microbial community and its driving factors in alpine grasslands in the humid regions of the Tibet Plateau might be of great significance for predicting the soil microbial community of this type of vegetation in response to environmental change. Using phospholipid fatty acids （PLFA）, we investigated soil microbial community composition along an elevational gradient （3094-4131 m above sea level） on Mount Yajiageng, and we explored the impact of plant functional groups and soil chemistry on the soil microbial community. Except for Arbuscular Mycorrhizal fungi （AM fungi） biomarker 18：2ω6,9 increasing significantly, other biomarkers did not show a consistent trend with the elevational gradient. Microbial biomass quantified by total PLFAs did not show the elevational trend and had mean values ranging from 1.64 to 4.09 ktmol per g organic carbon （OC）, which had the maximum value at the highest site. Bacterial PLFAs exhibited a similar trend with total PLFAs, and its mean values ranged from 0.82 to 1.81 μmol （g OC）-1. The bacterial to fungal biomass ratios had the minimum value at the highest site, which might be related to temperature and soil total nitrogen （TN）. The ratios of Gram-negative to Gram-positive bacteria had a significantly negative correlation with soil TN and had the maximum value at the highest site. Leguminous plant coverage and soil TN explained 58% of the total variation in the soil microbial community and could achieve the same interpretation as the whole model. Other factors may influence the soil microbial community through interaction with leguminous plant coverage and soil TN. Soil chemistry and plant functional group composition in substantial amounts explained different parts of the variation within the soil microbial community, and the interaction between them had no impact on the soil microbial community maybe beeause long-term grazing greatly reduces litter. In sum, although there were obvious differences in soil microbial communities along the elevation gradient, there were no clear elevational trends found in general. Plant functional groups and soil chemistry respectively affect the different aspects of soil microbial community. Leguminous plant coverage and soil TN had important effects in shaping soil microbial community.展开更多
Alpine grassland is the typical vegetation in the eastern Qinghai–Tibetan Plateau,which has important ecological service functions,and also supports the development of alpine stock farming.In recent years,under both ...Alpine grassland is the typical vegetation in the eastern Qinghai–Tibetan Plateau,which has important ecological service functions,and also supports the development of alpine stock farming.In recent years,under both the natural and human disturbance,alpine grasslands in this area have appeared to different degrees of desertification.A diagnosis of the desertification degree serves as the basis for grassland ecological restoration.This study constructs a comprehensive index based on remote sensing called alpine grassland desertification index(AGDI)to monitor the areas and degree of desertification.The most relevant indicators of desertification,namely,vegetation fraction,aboveground biomass,soil moisture,and land surface temperature,were selected to establish AGDI.The geographical detector is used to reselect and assess these indicators.The results show that the overall verification accuracy of AGDI is 82.05%.In particular,the accuracy of identifying severe desertification is the highest.Our study confirms that the desertification of alpine grasslands in the eastern Qinghai–Tibetan Plateau is characterized by fragmentation.Thus,Landsat-8 OLI data with a spatial resolution of 30 m is more suitable than MODIS data for alpine grasslands desertification monitoring.The research results can provide a methodological reference for monitoring desertification of alpine grasslands and other grassland regions in the world.展开更多
Knowledge of nitrous oxide(N_(2)O)exchanges through soils and atmosphere in various ecosystems has been of great importance in global climate change studies.However,the relative magnitude of surface and subsurface N_(...Knowledge of nitrous oxide(N_(2)O)exchanges through soils and atmosphere in various ecosystems has been of great importance in global climate change studies.However,the relative magnitude of surface and subsurface N_(2)O production sources from the alpine grassland ecosystem is unclear.In the present study,the N_(2)O concentration profile from 1.5 m in depth in soil to 32 m in height in air was measured from July 2000 to July 2001 in alpine grassland located in the permafrost area of the Qinghai-Xizang Plateau,which revealed that N_(2)O concentrations had a distinct variation pattern both in air and in soil during the study period.Mean N_(2)O concentrations in the atmosphere were significantly lower than those in the soil,which induced the N_(2)O emission from the alpine steppe soil into the atmosphere.Mean flux of N_(2)O in this alpine grassland experiment site was 0.05×10^(-4)μmol·m^(-2)·s^(-1).But the variation in N_(2)O emissions did not show any clear trends over the whole-year experiment in our study site.The highest N_(2)O concentration was found at the depth of 1.5 m in the soil while the lowest N_(2)O concentration occurred at the height of 8 m in the atmosphere.Mean N_(2)O concentrations in the soil increased significantly with depth.This was the influence of increasing soil moistures,which induced the increasing denitrification potential with depth.The mean N_(2)O concentrations at different heights in the air remained a more steady state because of the atmospheric negotiability.Seasonal variations of N_(2)O concentrations showed significant correlations between the neighbor layers both in the soil and in the atmosphere.The seasonal variations of N_(2)O concentrations at all horizons in the soil showed very clear patterns,with the highest concentrations occurring from the onset of frost to the freeze-thaw period and lowest concentrations occurring during the spring and the summer.Further analyses showed that the seasonal variations of N_(2)O concentrations in the soil were hardly explained by soil temperatures at any depth.Temporally,atmospheric N_(2)O concentrations at all heights exhibited almost the same seasonal pattern with the soil N_(2)O variations,while soil is believed to be the predominant natural source of atmospheric N_(2)O near the earth surface in this alpine grassland area.Also,a significant correlation was found between N_(2)O emissions and soil N_(2)O concentrations at 0.2 m in depth during the study period.This implied the variation of N_(2)O concentrations in the soil surface horizon was the most direct driving force of N_(2)O exchanges between the soil and the atmosphere.Soil atmospheric N_(2)O at surface layers is the main source of N_(2)O emissions from the soil surface to the atmosphere.Soil N_(2)O concentrations at deeper layers were all significantly higher than those at surface layers,which indicated that N_(2)O was diffused from the deeper layers to the surface layers in the soil,and finally was emitted to the atmosphere.展开更多
High-precision models enable the visualization of spatiotemporal patterns of soil microorganisms in the Qinghai-Xizang Plateau,a region highly sensitive to global change.However,large-scale,high-resolution data on soi...High-precision models enable the visualization of spatiotemporal patterns of soil microorganisms in the Qinghai-Xizang Plateau,a region highly sensitive to global change.However,large-scale,high-resolution data on soil bacterial and fungal communities,particularly in relation to the ecological impacts of fencing,remains relatively scarce,thereby limiting studies on the spatiotemporal distribution patterns of soil fungi and bacteria.This study constructed models of soil fungal and bacterial abundance andα-diversity(total abundance,major phylum abundance,primary functional group abundance,and species/phylogenetic/functionalα-diversity)in the alpine grasslands of the Qinghai-Xizang Plateau,based on observational data and utilizing the random forest method.Under fencing conditions,the variations in soil fungal and bacterial abundance andα-diversity were collectively explained by temperature,precipitation,and radiation,accounting for 46%-88%of the variation;while under grazing conditions,the inclusion of NDVI allowed these four factors to explain 47%-92%of the variation.The relative biases between simulated and observed values for fungal and bacterial abundance andα-diversity were lower than 10.83%,and the simulated values explained the variation in observed values ranging from 75%to 100%.The slopes of the linear regressions between observed and simulated values ranged between 0.81 and 1.00.Consequently,the random forest models constructed in this study demonstrated high accuracy and they can predicted the total abundance,major phylum abundance,primary functional group abundance,andα-diversity of soil microorganisms in alpine grasslands.These models can serve as a robust foundation for future related research.展开更多
We screened 161 eligible papers of experimental data across the Tibetan Plateau for meta-analysis,in order to systematically assess and validate potential application of plant resource allocation strategies,such as th...We screened 161 eligible papers of experimental data across the Tibetan Plateau for meta-analysis,in order to systematically assess and validate potential application of plant resource allocation strategies,such as the optimal allocation hypothesis,the isometric allocation hypothesis,and the allometric allocation hypothesis under environmental changes,and to explore the effects of environmental factors(temperature change,grazing intensity)on plant resource allocation strategies in alpine grassland ecosystems on the Tibetan Plateau.Overall,we found that the aboveground and belowground growth relationship in alpine grasslands follows the allometric growth hypothesis,which was unaffected by warming,grazing and their interactions.In addition,the biomass transferred between aboveground and belowground,the former was decreased,while the latter was increased under warming conditions in alpine steppe implies that the resource allocation strategy in alpine steppe grassland may potentially follow the optimal allocation hypothesis.We further found that the effect of soil properties on biomass,not the biomass allocation,was different under warming and grazing conditions in alpine grasslands,which further confirms the above conclusion.In addition,warming helped to mitigate the negative effects of grazing,which indicated that the interaction between warming and grazing is important in alpine grassland ecosystems.Overall,the results of this study are of theoretical significance for understanding how moderate grazing affects the growth of plants in alpine grasslands under changing climate.展开更多
Phenological models are valuable tools for predicting vegetation phenology and investigating the relationships between vegetation dynamics and climate. However, compared to temperate and boreal ecosystems, phenologica...Phenological models are valuable tools for predicting vegetation phenology and investigating the relationships between vegetation dynamics and climate. However, compared to temperate and boreal ecosystems, phenological modeling in alpine regions has received limited attention. In this study, we developed a semi-mechanistic phenological model, the Alpine Growing Season Index (AGSI), which incorporates the differential impacts of daily maximum and minimum air temperatures, as well as the constraints of precipitation and photoperiod, to predict foliar phenology in alpine grasslands on the Qinghai–Tibetan Plateau (QTP). The AGSI model is driven by daily minimum temperature (T_(min)), daily maximum temperature (T_(max)), precipitation averaged over the previous month (PA), and daily photoperiod (Photo). Based on the AGSI model, we further assessed the impacts of T_(min), T_(max), PA, and Photo on modeling accuracy, and identified the predominant climatic controls over foliar phenology across the entire QTP. Results showed that the AGSI model had higher accuracy than other GSI models. The total root mean square error (RMSE) of predicted leaf onset and offset dates, when evaluated using ground observations, was 12.9 ± 5.7 days, representing a reduction of 10.9%–54.1% compared to other models. The inclusion of T_(max) and PA in the AGSI model improved the total modeling accuracy of leaf onset and offset dates by 20.2%. Overall, PA and T_(min) showed more critical and extensive constraints on foliar phenology in alpine grasslands. The limiting effect of T_(max) was also considerable, particularly during July–November. This study provides a simple and effective tool for predicting foliar phenology in alpine grasslands and evaluating the climatic effects on vegetation phenological development in alpine regions.展开更多
Livestock grazing is one of primary way to use grasslands throughout the world, and the forage-livestock balance of grasslands is a core issue determining animal husbandry sustainability. However, there are few method...Livestock grazing is one of primary way to use grasslands throughout the world, and the forage-livestock balance of grasslands is a core issue determining animal husbandry sustainability. However, there are few methods for assessing the forage-livestock balance and none of those consider the dynamics of external abiotic factors that influence forage yields. In this study, we combine long-term field observations with remote sensing data and meteorological records of temperature and precipitation to quantify the impacts of climate change and human activities on the forage-livestock balance of alpine grasslands on the northern Tibetan Plateau for the years 2000 to 2016. We developed two methods: one is statical method based on equilibrium theory and the other is dynamic method based on non-equilibrium theory. We also examined the uncertainties and shortcomings of using these two methods as a basis for formulating policies for sustainable grassland management. Our results from the statical method showed severe overgrazing in the grasslands of all counties observed except Nyima(including Shuanghu) for the entire period from 2000 to 2016. In contrast, the results from the dynamic method showed overgrazing in only eight years of the study period 2000–2016, while in the other nine years alpine grasslands throughout the northern Tibetan Plateau were less grazed and had forage surpluses. Additionally, the dynamic method found that the alpine grasslands of counties in the northeastern and southwestern areas of the northern Tibetan Plateau were overgrazed, and that alpine grasslands in the central area of the plateau were less grazed with forage surpluses. The latter finding is consistent with field surveys. Therefore, we suggest that the dynamic method is more appropriate for assessment of forage-livestock management efforts in alpine grasslands on the northern Tibetan Plateau. However, the statical method is still recommended for assessments of alpine grasslands profoundly disturbed by irrational human activities.展开更多
A better understanding the mechanisms driving plant biomass allocation in different ecosystems is an important theoretical basis for ilustrating the adaptive strategies of plants.To date,the effects of habitat conditi...A better understanding the mechanisms driving plant biomass allocation in different ecosystems is an important theoretical basis for ilustrating the adaptive strategies of plants.To date,the effects of habitat conditions on plant biomass allocation have been widely studied.However,it is less known how plant community traits and functions(PCTF)affect biomass allocation,particularly in alpine grassland ecosystems.In this study,community-weighted means(CWM)were calculated at the community level using five leaf functional traits,and the relationships between PCTF and biomass trade-offs were explored using correlation analysis,variation partitioning analysis and structural equation modeling.We found that the trade-off values were greater than zero in both alpine meadow(AM)and alpine steppe(AS)across the Tibetan Plateau,with different values of 0.203 and 0.088 for AM and AS,respectively.Moreover,the critical factors determining biomass allocation in AS were species richness(SR;scored at 0.69)and leaf dry matter content of CWM(CWM_(LDMC),scored at 0.42),while in AM,the key factors were leaf dry matter content(CWM.pMC scored at 0.48)and leaf carbon content of CWM(CWM_(LC),scored at-0.45).In particular,both CWM_(LDMC)and SR in AS,as well as CWM_(LDMC)and CWM_(LDMC)in AM were primarily regulated by precipitation.In summary,precipitation tends to drive biomass allocation in alpine grasslands through its effects on PCTF,hence highlighting the importance of PCTF in regulating plant biomass allocation strategies along precipitation gradients.展开更多
With an average elevation of more than 4500 m,northern Xizang,known as the“roof of the world roof”,serves as the main body of the Qinghai-Tibetan Plateau’s ecological security barrier.However,the alpine grassland e...With an average elevation of more than 4500 m,northern Xizang,known as the“roof of the world roof”,serves as the main body of the Qinghai-Tibetan Plateau’s ecological security barrier.However,the alpine grassland ecosystem in northern Xizang has suffered considerable alterations as a result of both climate change and overgrazing,and there is a degradation trend in some regions.In 2009,one ecological engineering,the Protection and Construction Project of Ecological Security Barrier in Xizang(hereafter referred to as the“Project”)was implemented to preserve the alpine ecosystem and restore service functions in the plateau.Water conservation is one of the most important service functions in alpine grassland ecosystem in northern Xizang,where is one part of the Asian Water Tower.To clarify the specific ecological benefits of the Project,this paper utilized the InVEST model to evaluate the variation trend of the water conservation function of alpine grasslands in northern Xizang before and after the implementation of the Project from 2000 to 2020,and contribution rate of climate change and the Project was also quantified.Results showed that:(1)Although the water conservation capacity of different grassland types in northern Xizang were varied,their water conservation function all altered dramatically after implementation of the Project.Specifically,the water yield has increased by 10.07%,and the water source supply service has increased by 8.86%.Among these grasslands,the alpine meadow had the highest increasing rate,water conservation capacity increased from-1.84 mm yr^(-1)to 2.24 mm yr^(-1)Followed by the alpine desert steppe and the alpine steppe,the rate of water conservation function were decreased significantly due to the Project.(2)Although climate is still the primary factor affecting the water conservation function of alpine grasslands in northern Xizang,the Project has effectively promoted the local water conservation function,with contribution rates of 13.99%,8.75%,and 3.71%in the alpine meadow,alpine steppe and alpine desert steppe regions respectively.展开更多
Aims Litter is frequently buried in the soil in alpine grasslands due to grassland degradation,serious rodent infestation and frequent strong winds.However,the effects of various litter positions on litter decompositi...Aims Litter is frequently buried in the soil in alpine grasslands due to grassland degradation,serious rodent infestation and frequent strong winds.However,the effects of various litter positions on litter decomposition rates and nutrient dynamics under nitrogen(N)enrichment in such areas remain unknown.Methods A field experiment was performed in the alpine grasslands of northwest China to investigate the influence of litter position(surface,buried in the soil and standing)and N enrichment on litter decomposition,using data from two dominant grass species(Festuca ovina and Leymus tianschanicus)in control and N-enriched plots.Important Findings Litter decomposition rates were much faster in buried litter and slower in standing litter than in surface litter.N enrichment significantly affected litter quality and then influenced decomposition.But no significant differences in litter mass remaining were observed between control and N-enriched soil burial.These results indicated that N enrichment significantly affected litter decomposition by changes in litter quality.In addition,all litter exhibited net carbon(C)and phosphorus(P)release regardless of treatments.Litter exhibited net N accumulation for litter from the control plots but showed N release for litter from N enrichment plots.These suggested that litter decomposition can be limited by N and N enrichment influenced N cycling of litter.Current study presented direct evidence that soil buried litter exhibited faster mass loss and C release,and that soil burial can be a candidate explanation why litter decomposes faster than expected in dryland.展开更多
Nitrogen(N)is an essential nutrient for both plants and soil microbes,but it often has limited availability.Currently,little is known about the effects of different vegetation patch types on the partitioning of N betw...Nitrogen(N)is an essential nutrient for both plants and soil microbes,but it often has limited availability.Currently,little is known about the effects of different vegetation patch types on the partitioning of N between plants and soil microorganisms in grassland ecosystems.In the present study,we performed a^(15)N-labelling experiment(using^(15)N-NO_(3)^(-)and^(15)N-NH_(4)^(+))to investigate N uptake by plant biomass and microbial biomass for five common vegetation patch types in a degraded alpine steppe on the Tibetan Plateau,China.The results showed that plants and soil microorganisms in all patches showed a clear preference for the uptake of NO_(3)^(-).Plants in patches dominated by palatable species absorbed more N than plants in unpalatable species patches,while N uptake in the microbial biomass in unpalatable species patches was higher than that in palatable species patches.For the two soil depths,plants in Poa litwinowiana patches had the highest N uptake(NO_(3)^(-):13.32-51.28 mg m^(-2);NH_(4)^(+):0.35-1.36 mg m^(-2)),whereas microbial biomass in Oxytropis glacialis patches had the highest N uptake(NO_(3)^(-):846.97-1,659.87 mg m^(-2);NH_(4)^(+):108.75-185.14 mg m^(-2))among the five vegetation patch types.For both forms of N,soil microorganisms acquired relatively more N than the plants in the five vegetation patch types(i.e.,the ratio of microbial biomass N uptake to plant biomass N uptake was greater than 1).The N-absorbing capacity of plants decreased,whereas the capacity of soil microorganisms to take up N increased with the degradation of vegetation patches.Microorganisms that compete more strongly for N might reduce the uptake of nutrients by plants in degraded patches,which would not be conducive to the restoration of vegetation in N-limited alpine grasslands.展开更多
The source region of the Yellow River, accounting for over 38% of its total runoff, is a critical catchment area,primarily characterized by alpine grasslands. In 2005, the Maqu land surface processes observational sit...The source region of the Yellow River, accounting for over 38% of its total runoff, is a critical catchment area,primarily characterized by alpine grasslands. In 2005, the Maqu land surface processes observational site was established to monitor climate, land surface dynamics, and hydrological variability in this region. Over a 10-year period(2010–19), an extensive observational dataset was compiled, now available to the scientific community. This dataset includes comprehensive details on site characteristics, instrumentation, and data processing methods, covering meteorological and radiative fluxes, energy exchanges, soil moisture dynamics, and heat transfer properties. The dataset is particularly valuable for researchers studying land surface processes, land–atmosphere interactions, and climate modeling, and may also benefit ecological, hydrological, and water resource studies. The report ends with a discussion on perspectives and challenges of continued observational monitoring in this region, focusing on issues such as cryosphere influences, complex topography,and ecological changes like the encroachment of weeds and scrubland.展开更多
The response of plant functional diversity to external disturbances not only effectively predicts changes in the ecosystem but it also reflects how plant communities use external environmental resources.However,resear...The response of plant functional diversity to external disturbances not only effectively predicts changes in the ecosystem but it also reflects how plant communities use external environmental resources.However,research on how different herbivore assemblages affect plant functional diversity is limited.Therefore,this study systematically explored the effects of three typical herbivore assemblages(yak grazing,Tibetan sheep grazing,and mixed grazing by yaks and Tibetan sheep)on species richness,plant functional diversity,and soil physicochemical properties in alpine grasslands on the Qinghai-Tibet Plateau,China.This study further investigated the primary mechanisms driving the changes in plant functional diversity.The results indicate four key aspects of this system:(1)Grazing significantly enhanced plant functional diversity,particularly when the mixed grazing by yaks and Tibetan sheep was applied at a ratio of 1:2.This ratio showed the most substantial improvement in the functional dispersion index and Rao's quadratic entropy index.(2)Compared to enclosed treatments,grazing increased species richness andβ-diversity,contributing to higher plant functional diversity.(3)Grazing treatments affected various plant traits,such as reducing plant community height and leaf thickness while increasing specific leaf area.However,the impact on plant functional diversity was most pronounced under the mixed grazing by yaks and Tibetan sheep at a ratio of 1:2.(4)Speciesα-diversity was positively correlated with plant functional diversity.Changes in plant functional diversity were primarily regulated by variations in soil physicochemical properties.Specifically,increases in soil available nitrogen significantly promoted changes in plant functional diversity,while increases in soil available potassium and bulk density had a significant inhibitory effect on these changes.Long-term grazing significantly reduced the height of plant communities in alpine meadows,while a balanced mixture of yak and Tibetan sheep grazing,especially at a ratio of 1:2,enhanced plant functional diversity the most.This suggests that,under these conditions,the use of external environmental resources by the plant community is optimized.展开更多
[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conduct...[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.展开更多
Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studi...Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studies examining soil particle volume fractal dimension in alpine grasslands.To study the volume fractal dimension of soil particles （D） and its relationships with soil salt,soil nutrient and plant species diversity,we conducted an experiment on an alpine grassland under different disturbance degrees：non-disturbance （N0）,light disturbance （L）,moderate disturbance （M） and heavy disturbance （H）.The results showed that （1） Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance.（2） Shannon-Wiener diversity index,Pielou＇s evenness index and Margalef richness index reached their highest values at the M degree,indicating that moderate disturbance is beneficial to the increase of plant species diversity.（3） In the L and M degrees,there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter （SOM）.In the H degree,D was significantly and positively correlated with total salt （TS）.The results suggested that to a certain extent,D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics.（4） For the L degree,there was a significant negative correlation between D and the Shannon-Wiener diversity index; while for the M degree,there was a significant negative correlation between D and Pielou＇s evenness index.展开更多
Using stat ic chamber technique, fluxes of CO 2 , CH 4 and N 2 O were measured in the alpine grassland area from July 2000 to July 2001, d eterminations of mean fluxes showed that CO 2 and N 2 O were gene rally releas...Using stat ic chamber technique, fluxes of CO 2 , CH 4 and N 2 O were measured in the alpine grassland area from July 2000 to July 2001, d eterminations of mean fluxes showed that CO 2 and N 2 O were gene rally released from the soil, while the alpine grassland accounted for a weak CH 4 sink. Fluxes of CO 2 , CH 4 and N 2 O ranged widely. The highest CO 2 emission occurred in August, whereas a lmost 90% of the whole year emission occurred in the growing season. But the variations of CH 4 and N 2 O fluxes did not show any clear patterns over the one-year-experim ent. During a daily variation, the maximum CO 2 emission occurred at 16:00, and then decreased to the minimum emi ssion in the early morning. Daily pattern analyses indicated that the variation in CO 2 fluxes was positively related to air temperatures (R 2 =0.73) and soil temperatures at a depth of 5 cm (R 2 =0.86), whereas daily variations in CH 4 and N 2 O fluxes were poorly explained by soil temperatures and climatic va riables. CO 2 emissions in this area were much lower than other grasslands in plain areas .展开更多
Methane （OH4）, carbon dioxide （CO2） and nitrous oxide （N2O） are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of gre...Methane （OH4）, carbon dioxide （CO2） and nitrous oxide （N2O） are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of great significance. In this paper, we conducted a comparative study on an alpine grassland and alpine wetland at the Bayinbuluk Grassland Eco-system Research Station, Chinese Academy of Sciences. By using opaque, static, manual stainless steel chambers and gas chromatography, we measured the fluxes of CH4, N2O and CO2 from the grassland and wetland through an in situ monitoring study from May 2010 to October 2012. The mean flux rates of CH4, N2O and CO2 for the experimental alpine wetland in the growing season （from May to October） were estimated at 322.4 μg/（m2.h）, 16.7 μg/（m2.h） and 76.7 mg/（m2.h）, respectively; and the values for the alpine grassland were -88.2 μg/（m2.h）, 12.7 μg/（m2.h）, 57.3 mg/（m2.h）, respectively. The gas fluxes showed large seasonal and annual variations, suggesting weak fluxes in the non-growing season. The relationships between these gas fluxes and environmental factors were analyzed for the two alpine ecosystems. The results showed that air temperature, precipitation, soil temperature and soil moisture can greatly influence the fluxes of CH4, N2O and CO2, but the alpine grassland and alpine wetland showed different feedback mechanisms under the same climate and environmental conditions.展开更多
Fertilization has been shown to have suppressive effects on arbuscular mycorrhizal fungi(AMF) and root hemiparasites separately in numerous investigations, but its effects on AMF in the presence of root hemiparasites ...Fertilization has been shown to have suppressive effects on arbuscular mycorrhizal fungi(AMF) and root hemiparasites separately in numerous investigations, but its effects on AMF in the presence of root hemiparasites remain untested. In view of the contrasting nutritional effects of AMF and root hemiparasites on host plants, we tested the hypothesis that fertilization may not show strong suppressive effects on AMF when a plant community was infested by abundant hemiparasitic plants. Plants and soil samples were collected from experimental field plots in Bayanbulak Grassland, where N and P fertilizers had been applied for three continuous years for control against a spreading root hemiparasite, Pedicularis kansuensis. Shoot and root biomass of each plant functional group were determined. Root AMF colonization levels, soil spore abundance, and extraradical hyphae length density were measured for three soil depths(0 e10 cm, 10 e20 cm, 20 e30 cm). Partial 18 S r RNA gene sequencing was used to detect AMF diversity and community composition. In addition, we analyzed the relationship between relative abundance of different AMF genera and environmental factors using Spearman's correlation method. In contrast to suppressive effects reported by many previous studies, fertilization showed no significant effects on AMF root colonization or AMF species diversity in the soil. Instead, a marked increase in soil spore abundance and extraradical hyphae length density were observed. However, fertilization altered relative abundance and AMF composition in the soil. Our results support the hypothesis that fertilization does not significantly influence the abundance and diversity of AMF in a plant community infested by P. kansuensis.展开更多
In this study, two different methods including Digital Camera and Reference Panel （DCRP） and traditional in situ fPAR observation for measuring the in situ point fPAR of very short alpine grass vegetation were compa...In this study, two different methods including Digital Camera and Reference Panel （DCRP） and traditional in situ fPAR observation for measuring the in situ point fPAR of very short alpine grass vegetation were compared, and the Moderate Resolution Imaging Spectroradiometer （MODIS） fPAR products were evaluated and validated by in situ point data on the alpine grassland over the Northern Tibetan Plateau, which is sensitive to climate change and vulnerable to anthropogenic activities. Results showed that the MODIS alpine grassland fPAR product, examined by using DCRP, and traditional in situ fPAR observation had a significant relationship at the spatial and temporal scales. The decadal MODIS fPAR trend analysis showed that, average growing season fPAR increased by 1.2 × 10^-4 per year and in total increased 0.86% from 2002 to 2011 in alpine grassland, when most of the fPAR increments occurred in southeast and center of the Northern Tibetan Plateau, the alpine grassland tended to recover from degradation slightly. However, climatic factors have influenced the various alpine grassland vegetation fPAR over a period of 10 years; precipitation significantly affected the alpine meadow fPAR in the eastern region, whereas temperature considerably influenced the alpine desert steppe fPAR in the west region. These findings suggest that the regional heterogeneity in alpine grassland fPAR results from various environmental factors, except for vegetation characteristics, such as canopy structure and leaf area.展开更多
基金funded by the National Key R&D Program of China(2021YFE0112400 and 2023YFF1304303)the National Natural Science Foundation of China(32361143870 and 32101315)。
文摘The response of N_(2)O emissions to nitrogen(N)addition is usually positive,but its response to phosphorus(P)addition varies,and the underlying mechanisms for the changes in N_(2)O emissions remain unclear.We conducted field studies to examine the response of N_(2)O emissions to N and P addition over two years in three typical alpine grasslands,alpine meadow(AM),alpine steppe(AS),and alpine cultivated grassland(CG)on the Qinghai-Tibet Plateau(QTP).Our results showed consistent increases in N_(2)O emissions under N addition alone or with P addition,and insignificant change in N_(2)O emissions under P addition alone in all three grasslands.N addition increased N_(2)O emissions directly in AM,by lowering soil pH in AS,and by lowering abundance of denitrification genes in CG.N and P co-addition increased N_(2)O emissions in AM and AS but only showed an interactive effect in AM.P addition enhanced the increase in N_(2)O emissions caused by N addition mainly by promoting plant growth in AM.Overall,our results illustrate that short-term P addition cannot alleviate the stimulation of N_(2)O emissions by N deposition in alpine grassland ecosystems,and may even further stimulate N_(2)O emissions.
基金supported by the CAS/SAFEA International Partnership Program for Creative Research Teams (KZZD-EW-TZ-06)
文摘Understanding the vertical distribution patterns of soil microbial community and its driving factors in alpine grasslands in the humid regions of the Tibet Plateau might be of great significance for predicting the soil microbial community of this type of vegetation in response to environmental change. Using phospholipid fatty acids （PLFA）, we investigated soil microbial community composition along an elevational gradient （3094-4131 m above sea level） on Mount Yajiageng, and we explored the impact of plant functional groups and soil chemistry on the soil microbial community. Except for Arbuscular Mycorrhizal fungi （AM fungi） biomarker 18：2ω6,9 increasing significantly, other biomarkers did not show a consistent trend with the elevational gradient. Microbial biomass quantified by total PLFAs did not show the elevational trend and had mean values ranging from 1.64 to 4.09 ktmol per g organic carbon （OC）, which had the maximum value at the highest site. Bacterial PLFAs exhibited a similar trend with total PLFAs, and its mean values ranged from 0.82 to 1.81 μmol （g OC）-1. The bacterial to fungal biomass ratios had the minimum value at the highest site, which might be related to temperature and soil total nitrogen （TN）. The ratios of Gram-negative to Gram-positive bacteria had a significantly negative correlation with soil TN and had the maximum value at the highest site. Leguminous plant coverage and soil TN explained 58% of the total variation in the soil microbial community and could achieve the same interpretation as the whole model. Other factors may influence the soil microbial community through interaction with leguminous plant coverage and soil TN. Soil chemistry and plant functional group composition in substantial amounts explained different parts of the variation within the soil microbial community, and the interaction between them had no impact on the soil microbial community maybe beeause long-term grazing greatly reduces litter. In sum, although there were obvious differences in soil microbial communities along the elevation gradient, there were no clear elevational trends found in general. Plant functional groups and soil chemistry respectively affect the different aspects of soil microbial community. Leguminous plant coverage and soil TN had important effects in shaping soil microbial community.
基金funded by the Youth Projects of National Natural Science Foundation of China(Grants No.41701100)the Science and technology project of Sichuan Provincial Department of Education(Grants No.15ZB0023)。
文摘Alpine grassland is the typical vegetation in the eastern Qinghai–Tibetan Plateau,which has important ecological service functions,and also supports the development of alpine stock farming.In recent years,under both the natural and human disturbance,alpine grasslands in this area have appeared to different degrees of desertification.A diagnosis of the desertification degree serves as the basis for grassland ecological restoration.This study constructs a comprehensive index based on remote sensing called alpine grassland desertification index(AGDI)to monitor the areas and degree of desertification.The most relevant indicators of desertification,namely,vegetation fraction,aboveground biomass,soil moisture,and land surface temperature,were selected to establish AGDI.The geographical detector is used to reselect and assess these indicators.The results show that the overall verification accuracy of AGDI is 82.05%.In particular,the accuracy of identifying severe desertification is the highest.Our study confirms that the desertification of alpine grasslands in the eastern Qinghai–Tibetan Plateau is characterized by fragmentation.Thus,Landsat-8 OLI data with a spatial resolution of 30 m is more suitable than MODIS data for alpine grasslands desertification monitoring.The research results can provide a methodological reference for monitoring desertification of alpine grasslands and other grassland regions in the world.
文摘Knowledge of nitrous oxide(N_(2)O)exchanges through soils and atmosphere in various ecosystems has been of great importance in global climate change studies.However,the relative magnitude of surface and subsurface N_(2)O production sources from the alpine grassland ecosystem is unclear.In the present study,the N_(2)O concentration profile from 1.5 m in depth in soil to 32 m in height in air was measured from July 2000 to July 2001 in alpine grassland located in the permafrost area of the Qinghai-Xizang Plateau,which revealed that N_(2)O concentrations had a distinct variation pattern both in air and in soil during the study period.Mean N_(2)O concentrations in the atmosphere were significantly lower than those in the soil,which induced the N_(2)O emission from the alpine steppe soil into the atmosphere.Mean flux of N_(2)O in this alpine grassland experiment site was 0.05×10^(-4)μmol·m^(-2)·s^(-1).But the variation in N_(2)O emissions did not show any clear trends over the whole-year experiment in our study site.The highest N_(2)O concentration was found at the depth of 1.5 m in the soil while the lowest N_(2)O concentration occurred at the height of 8 m in the atmosphere.Mean N_(2)O concentrations in the soil increased significantly with depth.This was the influence of increasing soil moistures,which induced the increasing denitrification potential with depth.The mean N_(2)O concentrations at different heights in the air remained a more steady state because of the atmospheric negotiability.Seasonal variations of N_(2)O concentrations showed significant correlations between the neighbor layers both in the soil and in the atmosphere.The seasonal variations of N_(2)O concentrations at all horizons in the soil showed very clear patterns,with the highest concentrations occurring from the onset of frost to the freeze-thaw period and lowest concentrations occurring during the spring and the summer.Further analyses showed that the seasonal variations of N_(2)O concentrations in the soil were hardly explained by soil temperatures at any depth.Temporally,atmospheric N_(2)O concentrations at all heights exhibited almost the same seasonal pattern with the soil N_(2)O variations,while soil is believed to be the predominant natural source of atmospheric N_(2)O near the earth surface in this alpine grassland area.Also,a significant correlation was found between N_(2)O emissions and soil N_(2)O concentrations at 0.2 m in depth during the study period.This implied the variation of N_(2)O concentrations in the soil surface horizon was the most direct driving force of N_(2)O exchanges between the soil and the atmosphere.Soil atmospheric N_(2)O at surface layers is the main source of N_(2)O emissions from the soil surface to the atmosphere.Soil N_(2)O concentrations at deeper layers were all significantly higher than those at surface layers,which indicated that N_(2)O was diffused from the deeper layers to the surface layers in the soil,and finally was emitted to the atmosphere.
基金The Xizang Autonomous Region Science and Technology Project(XZ202401JD0029,XZ202501ZY0086,XZ202501ZY0056)The National Natural Science Foundation of China(31600432)+1 种基金The Lhasa Science and Technology Plan Project(LSKJ202422)The Chinese Academy of Sciences Youth Innovation Promotion Association(2020054)。
文摘High-precision models enable the visualization of spatiotemporal patterns of soil microorganisms in the Qinghai-Xizang Plateau,a region highly sensitive to global change.However,large-scale,high-resolution data on soil bacterial and fungal communities,particularly in relation to the ecological impacts of fencing,remains relatively scarce,thereby limiting studies on the spatiotemporal distribution patterns of soil fungi and bacteria.This study constructed models of soil fungal and bacterial abundance andα-diversity(total abundance,major phylum abundance,primary functional group abundance,and species/phylogenetic/functionalα-diversity)in the alpine grasslands of the Qinghai-Xizang Plateau,based on observational data and utilizing the random forest method.Under fencing conditions,the variations in soil fungal and bacterial abundance andα-diversity were collectively explained by temperature,precipitation,and radiation,accounting for 46%-88%of the variation;while under grazing conditions,the inclusion of NDVI allowed these four factors to explain 47%-92%of the variation.The relative biases between simulated and observed values for fungal and bacterial abundance andα-diversity were lower than 10.83%,and the simulated values explained the variation in observed values ranging from 75%to 100%.The slopes of the linear regressions between observed and simulated values ranged between 0.81 and 1.00.Consequently,the random forest models constructed in this study demonstrated high accuracy and they can predicted the total abundance,major phylum abundance,primary functional group abundance,andα-diversity of soil microorganisms in alpine grasslands.These models can serve as a robust foundation for future related research.
基金supported by the Regional Science and Technology Collaborative Innovation Special Project of Ngari in Tibetan Autonomous Region of China(QYXTZX-AL2022-05,QYXTZX-AL2024-05)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0600)+1 种基金the Tibet Central Government Guides Local Funding Projects(XZ202301YD0012C)the Joint Key Research Fund under cooperative agreement between the National Natural Science Foundation of China(NSFC)and Tibet Autonomous Region(TAR)(U20A2005).
文摘We screened 161 eligible papers of experimental data across the Tibetan Plateau for meta-analysis,in order to systematically assess and validate potential application of plant resource allocation strategies,such as the optimal allocation hypothesis,the isometric allocation hypothesis,and the allometric allocation hypothesis under environmental changes,and to explore the effects of environmental factors(temperature change,grazing intensity)on plant resource allocation strategies in alpine grassland ecosystems on the Tibetan Plateau.Overall,we found that the aboveground and belowground growth relationship in alpine grasslands follows the allometric growth hypothesis,which was unaffected by warming,grazing and their interactions.In addition,the biomass transferred between aboveground and belowground,the former was decreased,while the latter was increased under warming conditions in alpine steppe implies that the resource allocation strategy in alpine steppe grassland may potentially follow the optimal allocation hypothesis.We further found that the effect of soil properties on biomass,not the biomass allocation,was different under warming and grazing conditions in alpine grasslands,which further confirms the above conclusion.In addition,warming helped to mitigate the negative effects of grazing,which indicated that the interaction between warming and grazing is important in alpine grassland ecosystems.Overall,the results of this study are of theoretical significance for understanding how moderate grazing affects the growth of plants in alpine grasslands under changing climate.
基金jointly funded by the National Natural Science Foundation of China (42201059)the General Program of Guangdong Provincial Natural Science Foundation (2024A1515012731)the Science and Technology Program of Guangdong (2024B1212070012)。
文摘Phenological models are valuable tools for predicting vegetation phenology and investigating the relationships between vegetation dynamics and climate. However, compared to temperate and boreal ecosystems, phenological modeling in alpine regions has received limited attention. In this study, we developed a semi-mechanistic phenological model, the Alpine Growing Season Index (AGSI), which incorporates the differential impacts of daily maximum and minimum air temperatures, as well as the constraints of precipitation and photoperiod, to predict foliar phenology in alpine grasslands on the Qinghai–Tibetan Plateau (QTP). The AGSI model is driven by daily minimum temperature (T_(min)), daily maximum temperature (T_(max)), precipitation averaged over the previous month (PA), and daily photoperiod (Photo). Based on the AGSI model, we further assessed the impacts of T_(min), T_(max), PA, and Photo on modeling accuracy, and identified the predominant climatic controls over foliar phenology across the entire QTP. Results showed that the AGSI model had higher accuracy than other GSI models. The total root mean square error (RMSE) of predicted leaf onset and offset dates, when evaluated using ground observations, was 12.9 ± 5.7 days, representing a reduction of 10.9%–54.1% compared to other models. The inclusion of T_(max) and PA in the AGSI model improved the total modeling accuracy of leaf onset and offset dates by 20.2%. Overall, PA and T_(min) showed more critical and extensive constraints on foliar phenology in alpine grasslands. The limiting effect of T_(max) was also considerable, particularly during July–November. This study provides a simple and effective tool for predicting foliar phenology in alpine grasslands and evaluating the climatic effects on vegetation phenological development in alpine regions.
基金The National Key Research and Development Program of China(2016YFC0502001)The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20010201,DA19050502)。
文摘Livestock grazing is one of primary way to use grasslands throughout the world, and the forage-livestock balance of grasslands is a core issue determining animal husbandry sustainability. However, there are few methods for assessing the forage-livestock balance and none of those consider the dynamics of external abiotic factors that influence forage yields. In this study, we combine long-term field observations with remote sensing data and meteorological records of temperature and precipitation to quantify the impacts of climate change and human activities on the forage-livestock balance of alpine grasslands on the northern Tibetan Plateau for the years 2000 to 2016. We developed two methods: one is statical method based on equilibrium theory and the other is dynamic method based on non-equilibrium theory. We also examined the uncertainties and shortcomings of using these two methods as a basis for formulating policies for sustainable grassland management. Our results from the statical method showed severe overgrazing in the grasslands of all counties observed except Nyima(including Shuanghu) for the entire period from 2000 to 2016. In contrast, the results from the dynamic method showed overgrazing in only eight years of the study period 2000–2016, while in the other nine years alpine grasslands throughout the northern Tibetan Plateau were less grazed and had forage surpluses. Additionally, the dynamic method found that the alpine grasslands of counties in the northeastern and southwestern areas of the northern Tibetan Plateau were overgrazed, and that alpine grasslands in the central area of the plateau were less grazed with forage surpluses. The latter finding is consistent with field surveys. Therefore, we suggest that the dynamic method is more appropriate for assessment of forage-livestock management efforts in alpine grasslands on the northern Tibetan Plateau. However, the statical method is still recommended for assessments of alpine grasslands profoundly disturbed by irrational human activities.
基金the National Science Foundation of China(41871040)the Second Tibetan Plateau Scientific Expedition and Research(2019QZKK0405)Joint Research Project of Three-River-Resource National Park funded by the Chinese Academy of Sciences and Qinghai Provincial People's Government(LHZX-2020-08).
文摘A better understanding the mechanisms driving plant biomass allocation in different ecosystems is an important theoretical basis for ilustrating the adaptive strategies of plants.To date,the effects of habitat conditions on plant biomass allocation have been widely studied.However,it is less known how plant community traits and functions(PCTF)affect biomass allocation,particularly in alpine grassland ecosystems.In this study,community-weighted means(CWM)were calculated at the community level using five leaf functional traits,and the relationships between PCTF and biomass trade-offs were explored using correlation analysis,variation partitioning analysis and structural equation modeling.We found that the trade-off values were greater than zero in both alpine meadow(AM)and alpine steppe(AS)across the Tibetan Plateau,with different values of 0.203 and 0.088 for AM and AS,respectively.Moreover,the critical factors determining biomass allocation in AS were species richness(SR;scored at 0.69)and leaf dry matter content of CWM(CWM_(LDMC),scored at 0.42),while in AM,the key factors were leaf dry matter content(CWM.pMC scored at 0.48)and leaf carbon content of CWM(CWM_(LC),scored at-0.45).In particular,both CWM_(LDMC)and SR in AS,as well as CWM_(LDMC)and CWM_(LDMC)in AM were primarily regulated by precipitation.In summary,precipitation tends to drive biomass allocation in alpine grasslands through its effects on PCTF,hence highlighting the importance of PCTF in regulating plant biomass allocation strategies along precipitation gradients.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19050502)The Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK1006).
文摘With an average elevation of more than 4500 m,northern Xizang,known as the“roof of the world roof”,serves as the main body of the Qinghai-Tibetan Plateau’s ecological security barrier.However,the alpine grassland ecosystem in northern Xizang has suffered considerable alterations as a result of both climate change and overgrazing,and there is a degradation trend in some regions.In 2009,one ecological engineering,the Protection and Construction Project of Ecological Security Barrier in Xizang(hereafter referred to as the“Project”)was implemented to preserve the alpine ecosystem and restore service functions in the plateau.Water conservation is one of the most important service functions in alpine grassland ecosystem in northern Xizang,where is one part of the Asian Water Tower.To clarify the specific ecological benefits of the Project,this paper utilized the InVEST model to evaluate the variation trend of the water conservation function of alpine grasslands in northern Xizang before and after the implementation of the Project from 2000 to 2020,and contribution rate of climate change and the Project was also quantified.Results showed that:(1)Although the water conservation capacity of different grassland types in northern Xizang were varied,their water conservation function all altered dramatically after implementation of the Project.Specifically,the water yield has increased by 10.07%,and the water source supply service has increased by 8.86%.Among these grasslands,the alpine meadow had the highest increasing rate,water conservation capacity increased from-1.84 mm yr^(-1)to 2.24 mm yr^(-1)Followed by the alpine desert steppe and the alpine steppe,the rate of water conservation function were decreased significantly due to the Project.(2)Although climate is still the primary factor affecting the water conservation function of alpine grasslands in northern Xizang,the Project has effectively promoted the local water conservation function,with contribution rates of 13.99%,8.75%,and 3.71%in the alpine meadow,alpine steppe and alpine desert steppe regions respectively.
基金This work was supported financially by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20050103)Natural Science Foundation of Xinjiang Uygur Autonomous Region(2019D01C066)+1 种基金Tianshan Cedar Project of Xinjiang Uygur Autonomous Region(2020XS26)the National Natural Science Foundation of China(41425007,41673079)。
文摘Aims Litter is frequently buried in the soil in alpine grasslands due to grassland degradation,serious rodent infestation and frequent strong winds.However,the effects of various litter positions on litter decomposition rates and nutrient dynamics under nitrogen(N)enrichment in such areas remain unknown.Methods A field experiment was performed in the alpine grasslands of northwest China to investigate the influence of litter position(surface,buried in the soil and standing)and N enrichment on litter decomposition,using data from two dominant grass species(Festuca ovina and Leymus tianschanicus)in control and N-enriched plots.Important Findings Litter decomposition rates were much faster in buried litter and slower in standing litter than in surface litter.N enrichment significantly affected litter quality and then influenced decomposition.But no significant differences in litter mass remaining were observed between control and N-enriched soil burial.These results indicated that N enrichment significantly affected litter decomposition by changes in litter quality.In addition,all litter exhibited net carbon(C)and phosphorus(P)release regardless of treatments.Litter exhibited net N accumulation for litter from the control plots but showed N release for litter from N enrichment plots.These suggested that litter decomposition can be limited by N and N enrichment influenced N cycling of litter.Current study presented direct evidence that soil buried litter exhibited faster mass loss and C release,and that soil burial can be a candidate explanation why litter decomposes faster than expected in dryland.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program,China(2019QZKK0404)the National Natural Science Foundation of China(42271070)+1 种基金the West Light Scholar of Chinese Academy of Sciences(xbzg-zdsys-202202)the Technology Major Project of Tibetan Autonomous Region of China(XZ202201ZD0005G01)。
文摘Nitrogen(N)is an essential nutrient for both plants and soil microbes,but it often has limited availability.Currently,little is known about the effects of different vegetation patch types on the partitioning of N between plants and soil microorganisms in grassland ecosystems.In the present study,we performed a^(15)N-labelling experiment(using^(15)N-NO_(3)^(-)and^(15)N-NH_(4)^(+))to investigate N uptake by plant biomass and microbial biomass for five common vegetation patch types in a degraded alpine steppe on the Tibetan Plateau,China.The results showed that plants and soil microorganisms in all patches showed a clear preference for the uptake of NO_(3)^(-).Plants in patches dominated by palatable species absorbed more N than plants in unpalatable species patches,while N uptake in the microbial biomass in unpalatable species patches was higher than that in palatable species patches.For the two soil depths,plants in Poa litwinowiana patches had the highest N uptake(NO_(3)^(-):13.32-51.28 mg m^(-2);NH_(4)^(+):0.35-1.36 mg m^(-2)),whereas microbial biomass in Oxytropis glacialis patches had the highest N uptake(NO_(3)^(-):846.97-1,659.87 mg m^(-2);NH_(4)^(+):108.75-185.14 mg m^(-2))among the five vegetation patch types.For both forms of N,soil microorganisms acquired relatively more N than the plants in the five vegetation patch types(i.e.,the ratio of microbial biomass N uptake to plant biomass N uptake was greater than 1).The N-absorbing capacity of plants decreased,whereas the capacity of soil microorganisms to take up N increased with the degradation of vegetation patches.Microorganisms that compete more strongly for N might reduce the uptake of nutrients by plants in degraded patches,which would not be conducive to the restoration of vegetation in N-limited alpine grasslands.
基金supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No.42325502)the 2nd Scientific Expedition to the Qinghai–Tibet Plateau (Grant No.2019QZKK0102)+3 种基金the West Light Foundation of the Chinese Academy of Sciences (Grant No.xbzg-zdsys-202215)the Science and Technology Research Plan of Gansu Province (Grant Nos.23JRRA654 and 20JR10RA070)the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No.QCH2019004)iLEAPS (integrated Land Ecosystem–Atmosphere Processes Study)。
文摘The source region of the Yellow River, accounting for over 38% of its total runoff, is a critical catchment area,primarily characterized by alpine grasslands. In 2005, the Maqu land surface processes observational site was established to monitor climate, land surface dynamics, and hydrological variability in this region. Over a 10-year period(2010–19), an extensive observational dataset was compiled, now available to the scientific community. This dataset includes comprehensive details on site characteristics, instrumentation, and data processing methods, covering meteorological and radiative fluxes, energy exchanges, soil moisture dynamics, and heat transfer properties. The dataset is particularly valuable for researchers studying land surface processes, land–atmosphere interactions, and climate modeling, and may also benefit ecological, hydrological, and water resource studies. The report ends with a discussion on perspectives and challenges of continued observational monitoring in this region, focusing on issues such as cryosphere influences, complex topography,and ecological changes like the encroachment of weeds and scrubland.
基金financially supported by the National Natural Science Foundation of China(U20A2007 and 32160343)the Open Project of Key Laboratory of the Alpine Grassland Ecology in the Three Rivers Region(Qinghai University),Ministry of Education of China(2023-SJY-KF-02)the West Light Foundation of the Chinese Academy of Sciences。
文摘The response of plant functional diversity to external disturbances not only effectively predicts changes in the ecosystem but it also reflects how plant communities use external environmental resources.However,research on how different herbivore assemblages affect plant functional diversity is limited.Therefore,this study systematically explored the effects of three typical herbivore assemblages(yak grazing,Tibetan sheep grazing,and mixed grazing by yaks and Tibetan sheep)on species richness,plant functional diversity,and soil physicochemical properties in alpine grasslands on the Qinghai-Tibet Plateau,China.This study further investigated the primary mechanisms driving the changes in plant functional diversity.The results indicate four key aspects of this system:(1)Grazing significantly enhanced plant functional diversity,particularly when the mixed grazing by yaks and Tibetan sheep was applied at a ratio of 1:2.This ratio showed the most substantial improvement in the functional dispersion index and Rao's quadratic entropy index.(2)Compared to enclosed treatments,grazing increased species richness andβ-diversity,contributing to higher plant functional diversity.(3)Grazing treatments affected various plant traits,such as reducing plant community height and leaf thickness while increasing specific leaf area.However,the impact on plant functional diversity was most pronounced under the mixed grazing by yaks and Tibetan sheep at a ratio of 1:2.(4)Speciesα-diversity was positively correlated with plant functional diversity.Changes in plant functional diversity were primarily regulated by variations in soil physicochemical properties.Specifically,increases in soil available nitrogen significantly promoted changes in plant functional diversity,while increases in soil available potassium and bulk density had a significant inhibitory effect on these changes.Long-term grazing significantly reduced the height of plant communities in alpine meadows,while a balanced mixture of yak and Tibetan sheep grazing,especially at a ratio of 1:2,enhanced plant functional diversity the most.This suggests that,under these conditions,the use of external environmental resources by the plant community is optimized.
基金Supported by Young Talents Project of Chinese Academy of Sciences (KZCX2-YW-QN302)the National Natural Science Found ofChina (41071209,30870424)~~
文摘[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.
基金financially supported by the National Basic Research Program of China(2009CB825103)
文摘Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studies examining soil particle volume fractal dimension in alpine grasslands.To study the volume fractal dimension of soil particles （D） and its relationships with soil salt,soil nutrient and plant species diversity,we conducted an experiment on an alpine grassland under different disturbance degrees：non-disturbance （N0）,light disturbance （L）,moderate disturbance （M） and heavy disturbance （H）.The results showed that （1） Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance.（2） Shannon-Wiener diversity index,Pielou＇s evenness index and Margalef richness index reached their highest values at the M degree,indicating that moderate disturbance is beneficial to the increase of plant species diversity.（3） In the L and M degrees,there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter （SOM）.In the H degree,D was significantly and positively correlated with total salt （TS）.The results suggested that to a certain extent,D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics.（4） For the L degree,there was a significant negative correlation between D and the Shannon-Wiener diversity index; while for the M degree,there was a significant negative correlation between D and Pielou＇s evenness index.
基金National Key Project for Basic Research,No.G1998040800
文摘Using stat ic chamber technique, fluxes of CO 2 , CH 4 and N 2 O were measured in the alpine grassland area from July 2000 to July 2001, d eterminations of mean fluxes showed that CO 2 and N 2 O were gene rally released from the soil, while the alpine grassland accounted for a weak CH 4 sink. Fluxes of CO 2 , CH 4 and N 2 O ranged widely. The highest CO 2 emission occurred in August, whereas a lmost 90% of the whole year emission occurred in the growing season. But the variations of CH 4 and N 2 O fluxes did not show any clear patterns over the one-year-experim ent. During a daily variation, the maximum CO 2 emission occurred at 16:00, and then decreased to the minimum emi ssion in the early morning. Daily pattern analyses indicated that the variation in CO 2 fluxes was positively related to air temperatures (R 2 =0.73) and soil temperatures at a depth of 5 cm (R 2 =0.86), whereas daily variations in CH 4 and N 2 O fluxes were poorly explained by soil temperatures and climatic va riables. CO 2 emissions in this area were much lower than other grasslands in plain areas .
基金funded by the National Basic Research Program of China (2009CB825103)the National Natural Science Foundation of China (41340041)the West Light Foundation of the Chinese Academy of Sciences (XBBS201206)
文摘Methane （OH4）, carbon dioxide （CO2） and nitrous oxide （N2O） are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of great significance. In this paper, we conducted a comparative study on an alpine grassland and alpine wetland at the Bayinbuluk Grassland Eco-system Research Station, Chinese Academy of Sciences. By using opaque, static, manual stainless steel chambers and gas chromatography, we measured the fluxes of CH4, N2O and CO2 from the grassland and wetland through an in situ monitoring study from May 2010 to October 2012. The mean flux rates of CH4, N2O and CO2 for the experimental alpine wetland in the growing season （from May to October） were estimated at 322.4 μg/（m2.h）, 16.7 μg/（m2.h） and 76.7 mg/（m2.h）, respectively; and the values for the alpine grassland were -88.2 μg/（m2.h）, 12.7 μg/（m2.h）, 57.3 mg/（m2.h）, respectively. The gas fluxes showed large seasonal and annual variations, suggesting weak fluxes in the non-growing season. The relationships between these gas fluxes and environmental factors were analyzed for the two alpine ecosystems. The results showed that air temperature, precipitation, soil temperature and soil moisture can greatly influence the fluxes of CH4, N2O and CO2, but the alpine grassland and alpine wetland showed different feedback mechanisms under the same climate and environmental conditions.
基金financially supported by the Natural Science Foundation of China (U1303201, No. 31400440 and No. 31370512)China Agriculture Research System (CARS-34)+2 种基金Natural Science Foundation of Yunnan Province (2016FB059)funding for Airong Li from The Youth Innovation Promotion Association of Chinese Academy of Sciencesthe Young Academic and Technical Leader Raising Foundation of Yunnan Province (2014HB047)
文摘Fertilization has been shown to have suppressive effects on arbuscular mycorrhizal fungi(AMF) and root hemiparasites separately in numerous investigations, but its effects on AMF in the presence of root hemiparasites remain untested. In view of the contrasting nutritional effects of AMF and root hemiparasites on host plants, we tested the hypothesis that fertilization may not show strong suppressive effects on AMF when a plant community was infested by abundant hemiparasitic plants. Plants and soil samples were collected from experimental field plots in Bayanbulak Grassland, where N and P fertilizers had been applied for three continuous years for control against a spreading root hemiparasite, Pedicularis kansuensis. Shoot and root biomass of each plant functional group were determined. Root AMF colonization levels, soil spore abundance, and extraradical hyphae length density were measured for three soil depths(0 e10 cm, 10 e20 cm, 20 e30 cm). Partial 18 S r RNA gene sequencing was used to detect AMF diversity and community composition. In addition, we analyzed the relationship between relative abundance of different AMF genera and environmental factors using Spearman's correlation method. In contrast to suppressive effects reported by many previous studies, fertilization showed no significant effects on AMF root colonization or AMF species diversity in the soil. Instead, a marked increase in soil spore abundance and extraradical hyphae length density were observed. However, fertilization altered relative abundance and AMF composition in the soil. Our results support the hypothesis that fertilization does not significantly influence the abundance and diversity of AMF in a plant community infested by P. kansuensis.
文摘In this study, two different methods including Digital Camera and Reference Panel （DCRP） and traditional in situ fPAR observation for measuring the in situ point fPAR of very short alpine grass vegetation were compared, and the Moderate Resolution Imaging Spectroradiometer （MODIS） fPAR products were evaluated and validated by in situ point data on the alpine grassland over the Northern Tibetan Plateau, which is sensitive to climate change and vulnerable to anthropogenic activities. Results showed that the MODIS alpine grassland fPAR product, examined by using DCRP, and traditional in situ fPAR observation had a significant relationship at the spatial and temporal scales. The decadal MODIS fPAR trend analysis showed that, average growing season fPAR increased by 1.2 × 10^-4 per year and in total increased 0.86% from 2002 to 2011 in alpine grassland, when most of the fPAR increments occurred in southeast and center of the Northern Tibetan Plateau, the alpine grassland tended to recover from degradation slightly. However, climatic factors have influenced the various alpine grassland vegetation fPAR over a period of 10 years; precipitation significantly affected the alpine meadow fPAR in the eastern region, whereas temperature considerably influenced the alpine desert steppe fPAR in the west region. These findings suggest that the regional heterogeneity in alpine grassland fPAR results from various environmental factors, except for vegetation characteristics, such as canopy structure and leaf area.
