Lakes are carbon dioxide(CO_(2))and methane(CH_(4))emission hotspots,whose associated flux is spatially vari-able.Many studies have investigated the impact of microorganisms and environmental factors on CO_(2) and CH_...Lakes are carbon dioxide(CO_(2))and methane(CH_(4))emission hotspots,whose associated flux is spatially vari-able.Many studies have investigated the impact of microorganisms and environmental factors on CO_(2) and CH_(4) emissions between different lakes.However,the carbon emissions and their influencing factors of different areas within a single lake remain poorly understood.Accordingly,this study investigates CO_(2) and CH_(4) emission hetero-geneity in a large floodplain lake system and distribution characteristics of associated functional microorganisms.Findings show that mean CO_(2) and CH_(4) flux values in the sub lake area were 62.03±24.21 mg/(m2·day)and 5.97±3.2μg/(m2·day),which were greater by factors of 1.78 and 2.96 compared to the water channel and the main lake area,respectively.The alpha diversity of methanogens in the sub lake area was lower than that in the main lake and water channel areas.The abundance of methanogens in bottom water layer was higher compared with the middle and surface layers.Conversely,the abundance of methane(CH_(4))-oxidizing bacteria in the surface layer was higher than that in the bottom layer.Additionally,the composition of methanogen and CH_(4)-oxidizing bacterial community,chlorophyll a(Chl-a),pH,total phosphorus(TP)and dissolved organic carbon(DOC)con-tent constituted the dominate driving factors affecting lake C emissions.Results from this study can be used to improve our understanding of lake spatial heterogeneous of CO_(2) and CH_(4) emission and the driving mechanisms within floodplain lakes under the coupling effects of functional C microorganisms and environmental factors.展开更多
Eddy Covariance technique(EC) achieves the direct measurement on ecosystem carbon, nitrogen and water fluxes, and it provides scientific data for accurately assessing ecosystem functions in mitigating global climate c...Eddy Covariance technique(EC) achieves the direct measurement on ecosystem carbon, nitrogen and water fluxes, and it provides scientific data for accurately assessing ecosystem functions in mitigating global climate change. This paper briefly reviewed the construction and development of Chinese terrestrial ecosystem flux observation and research network(China FLUX), and systematically introduced the design principle and technology of the terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation system of China FLUX. In addition, this paper summarized the main progress of China FLUX in the ecosystem carbon, nitrogen and water exchange and environmental controlling mechanisms, the spatial pattern of carbon, nitrogen and water fluxes and biogeographical mechanisms, and the regional terrestrial ecosystem carbon budget assessment. Finally, the prospects and emphases of the terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation of China FLUX are put forward to provide theoretical references for the development of flux observation and research in China.展开更多
From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. B...From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency （WUE） and nitrogen use efficiency （NUE）, and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed： （1） vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. （2） Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE （p0.001）. While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE （p0.001）. Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. （3） There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC （p0.001）, indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.展开更多
Characterization of the vertical distribution of soil organic carbon(C), nitrogen(N), and phosphorus(P) may improve our ability to accurately estimate soil C, N, and P storage. Based on a database of 21 354 records in...Characterization of the vertical distribution of soil organic carbon(C), nitrogen(N), and phosphorus(P) may improve our ability to accurately estimate soil C, N, and P storage. Based on a database of 21 354 records in 74 long-term monitoring plots from 2004 to 2013 in the Chinese Ecosystem Research Network(CERN), we built fitting functions to quantify the vertical distribution of soil C, N, and P(up to 100 cm depth) in the typical Chinese terrestrial ecosystems. The decrease of soil C, N, and P content with depth can be well fitted with various mathematical functions. The fitting functions differed greatly between artificial(agriculture) and natural(desert, forest, and grassland) ecosystems, and also differed with respect to soil C, N, and P content. In both the artificial and natural ecosystems, the best fitting functions were exponential functions for C, quadratic functions for N, and quadratic functions for P. Furthermore, the stoichiometric ratios of soil C, N, and P were ranked in descending order: grassland > forest > agriculture > desert, and were also associated with climate. This study is the first to build the fitting functions for the profile distribution of soil C, N, and P in China at a national scale. Our findings provide a scientific basis to accurately assess the storage of C, N, and P in soils at a large scale, especially for the integrative analysis of historical data.展开更多
The alpine meadow, as one of the typical vegetation types on the Tibetan Plateau, is one of the most sensitive terrestrial ecosystems to climate warming. However, how climate warming affects the carbon cycling of the ...The alpine meadow, as one of the typical vegetation types on the Tibetan Plateau, is one of the most sensitive terrestrial ecosystems to climate warming. However, how climate warming affects the carbon cycling of the alpine meadow on the Tibetan Plateau is not very dear. A field experiment under controlled experimental warming and clipping conditions was conducted in an alpine meadow on the Northern Tibetan Plateau since July 2008. Open top chambers （0TCs） were used to simulate climate warming. The main objective of this study was to examine the responses of ecosystem respiration （Reco） and its temperature sensitivity to experimental warming and clipping at daily time scale. Therefore, we measured Reco once or twice a month from July to September in 2010, from June to September in 2011 and from August to September in 2012. Air temperature dominated daily variation of Reco whether or not experimental warming and clipping were present. Air temperature was exponentially correlated with Reco and it could significantly explain 58-96% variation of Redo at daily time scale. Experimental warming and clipping decreased daily mean Reco by 5.8-37.7% and -11.9-23.0%, respectively, although not all these changes were significant. Experimental warming tended to decrease the temperature sensitivity of Reco, whereas clipping tended to increase the temperature sensitivity of Reco at daily time scale. Our findings suggest that Reco wasmainly controlled by air temperature and may acclimate to climate warming due to its lower temperature sensitivity under experimental warming at daily time scale.展开更多
Afforestation is believed to be an effective practice to reduce global warming by sequestering large amounts of carbon in plant biomass and soil.However,the factors that determine the rate of carbon sequestration with...Afforestation is believed to be an effective practice to reduce global warming by sequestering large amounts of carbon in plant biomass and soil.However,the factors that determine the rate of carbon sequestration with afforestation are still poorly understood.We analyzed ecosystem carbon exchange after afforestation based on eddy covariance measurements with the aim to identify factors responsible for the rate of carbon exchange following afforestation.The results indicated that afforestation in the tropical/subtropical and temperate climate zones had greater capacities for carbon sequestration than those in boreal zones.Net ecosystem production(NEP),gross primary production(GPP)and ecosystem respiration(RE)varied greatly with age groups over time.Specifically,NEP was initially less than zero in the\10 year group and then increased to its peak in the 10-20 year group.Afforestation of varied previous land use types and planting of diverse tree species did not result in different carbon fluxes.The general linear model showed that climate zone and age of afforestation were the dominant factors influencing carbon sequestration.These factors jointly controlled 51%,61%and 63%of the variation in NEP,GPP and RE,respectively.Compared to the strong regulation of climate on GPP and RE,NEP showed greater sensitivity to the age of afforestation.These results increase our understanding of the variation in ecosystem carbon exchange of afforestation and suggest that afforestation in subtropical and temperate areas after 20 years would yield greater carbon sink benefits than would afforestation of boreal regions.展开更多
A continuous three-year observation(from May 2008 to April 2011)was conducted to characterize the spatial variation of dissolved inorganic nitrogen(DIN)deposition at eight main forest ecosystems along the north-south ...A continuous three-year observation(from May 2008 to April 2011)was conducted to characterize the spatial variation of dissolved inorganic nitrogen(DIN)deposition at eight main forest ecosystems along the north-south transect of eastern China(NSTEC).The results show that both throughfall DIN deposition and bulk DIN deposition increase from north to south along the NSTEC.Throughfall DIN deposition varies greatly from 2.7 kg N/(ha·yr)to 33.0 kg N/(ha·yr),with an average of 10.6 kg N/(ha·yr),and bulk DIN deposition ranges from 4.1 kg N/(ha·yr)to 25.4 kg N/(ha·yr),with an average of 9.8 kg N/(ha·yr).NH4+-N is the dominant form of DIN deposition at most sampling sites.Additionally,the spatial variation of DIN deposition is controlled mainly by precipitation.Moreover,in the northern part of the NSTEC,bulk DIN deposition is 17%higher than throughfall DIN deposition,whereas the trend is opposite in the southern part of the NSTEC.The results demonstrate that DIN deposition would likely threaten the forest ecosystems along the NSTEC,compared with the critical loads(CL)of N deposition,and DIN deposition in this region is mostly controlled by agricultural activities rather than industrial activities or transportation.展开更多
Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about t...Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about to what extent grassland productivity will respond to an individual precipitation event. In this study, we quantified the duration, the maximum, and the time-integrated amount of the response of daily gross primary productivity (GPP) to an individual precipitation event and their variations with different sizes of precipitation events in a typical temperate steppe in Inner Mongolia, China. Results showed that the duration of GPP-response (τ<sub>R</sub>) and the maximum absolute GPP-response (GPP<sub>max</sub>) increased linearly with the sizes of precipitation events (P<sub>es</sub>), driving a corresponding increase in time-integrated amount of the GPP-response (GPP<sub>total</sub>) because variations of GPPtotal were largely explained by τ<sub>R</sub> and GPP<sub>max</sub>. The relative contributions of these two parameters to GPP<sub>total</sub> were strongly P<sub>es</sub>-dependent. The GPP<sub>max</sub> contributed more to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively small (<20 mm), whereas τ<sub>R</sub> was the main driver to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively large. In addition, a threshold size of at least 5 mm of precipitation was required to induce a GPP-response for the temperate steppe in this study. Our work has important implications for the modeling community to obtain an advanced understanding of productivity-response of grassland ecosystems to altered precipitation regimes.展开更多
Forest soil carbon is a major carbon pool of terrestrial ecosystems,and accurate estimation of soil organic carbon(SOC)stocks in forest ecosystems is rather challenging.This study compared the prediction performance o...Forest soil carbon is a major carbon pool of terrestrial ecosystems,and accurate estimation of soil organic carbon(SOC)stocks in forest ecosystems is rather challenging.This study compared the prediction performance of three empirical model approaches namely,regression kriging(RK),multiple stepwise regression(MSR),random forest(RF),and boosted regression trees(BRT)to predict SOC stocks in Northeast China for 1990 and 2015.Furthermore,the spatial variation of SOC stocks and the main controlling environmental factors during the past 25 years were identified.A total of 82(in 1990)and 157(in 2015)topsoil(0–20 cm)samples with 12 environmental factors(soil property,climate,topography and biology)were selected for model construction.Randomly selected80%of the soil sample data were used to train the models and the other 20%data for model verification using mean absolute error,root mean square error,coefficient of determination and Lin's consistency correlation coefficient indices.We found BRT model as the best prediction model and it could explain 67%and 60%spatial variation of SOC stocks,in 1990,and 2015,respectively.Predicted maps of all models in both periods showed similar spatial distribution characteristics,with the lower SOC in northeast and higher SOC in southwest.Mean annual temperature and elevation were the key environmental factors influencing the spatial variation of SOC stock in both periods.SOC stocks were mainly stored under Cambosols,Gleyosols and Isohumosols,accounting for 95.6%(1990)and 95.9%(2015).Overall,SOC stocks increased by 471 Tg C during the past 25 years.Our study found that the BRT model employing common environmental factors was the most robust method for forest topsoil SOC stocks inventories.The spatial resolution of BRT model enabled us to pinpoint in which areas of Northeast China that new forest tree planting would be most effective for enhancing forest C stocks.Overall,our approach is likely to be useful in forestry management and ecological restoration at and beyond the regional scale.展开更多
Air pollution has seriously endangered human health and the natural ecosystem during the last decades.Air quality monitoring stations(AQMS)have played a critical role in providing valuable data sets for recording regi...Air pollution has seriously endangered human health and the natural ecosystem during the last decades.Air quality monitoring stations(AQMS)have played a critical role in providing valuable data sets for recording regional air pollutants.The spatial representativeness of AQMS is a critical parameter when choosing the location of stations and assessing effects on the population to long-term exposure to air pollution.In this paper,we proposed a methodological framework for assessing the spatial representativeness of the regional air quality monitoring network and applied it to ground-based PM_(2.5)observation in the mainland of China.Weighted multidimensional Euclidean distance between each pixel and the stations was used to determine the representativeness of the existing monitoring network.In addition,the K-means clustering method was adopted to improve the spatial representativeness of the existing AQMS.The results showed that there were obvious differences among the representative area of 1820 stations in the mainland of China.The monitoring stations could well represent the PM_(2.5)spatial distribution of the entire region,and the effectively represented area(i.e.the area where the Euclidean distance between the pixels and the stations was lower than the average value)accounted for 67.32%of the total area and covered 93.12%of the population.Forty additional stations were identified in the Northwest,North China,and Northeast regions,which could improve the spatial representativeness by 14.31%.展开更多
The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction between ecosystem carbon uptake and water cycling in the ...The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction between ecosystem carbon uptake and water cycling in the context of global change.The estimation of T/ET has been paid increasing attention from the scientific community in recent years globally.In this paper,we used the Priestly-Taylor Jet Propulsion Laboratory Model (PT-JPL) driven by regional remote sensing data and gridded meteorological data,to simulate the T/ET in forest ecosystems along the North-South Transect of East China (NSTEC) during 2001-2010,and to analyze the spatial distribution and temporal variation of T/ET,as well as the factors influencing the variation in T/ET.The results showed that:(1) The PT-JPL model is suitable for the simulation of evapotranspiration and its components of forest ecosystems in Eastern China,and has relatively good stability and reliability.(2) Spatial distribution of T/ET in forest ecosystems along NSTEC was heterogeneous,i.e.,T/ET was higher in the north and lower in the south,with an averaged value of 0.69;and the inter-annual variation of T/ET showed a significantly increasing trend,with an increment of 0.007/yr (p<0.01).(3) Seasonal and inter- annual variations of T/ET had different dominant factors.Temperature and EVI can explain around 90%(p<0.01) of the seasonal variation in T/ET,while the inter-annual variation in T/ET was mainly controlled by EVI (53%,p<0.05).展开更多
Understanding climatic effects on cropland water use efficiency at different elevations is imperative for managing agricultural water and production in response to ongoing climate change in climate-sensitive areas wit...Understanding climatic effects on cropland water use efficiency at different elevations is imperative for managing agricultural water and production in response to ongoing climate change in climate-sensitive areas with complex topography, such as southwestern China. We investigated climatic effects on cropland water use efficiency in southwestern China at each 100-m elevation bin during 2001–2017. The maximum water use efficiency was 1.71 gC kg^(–1) H_2O for the 1900–1999 m elevation bin under the growing season temperature and precipitation of 14.58±0.32℃ and 965.40±136.45 mm, respectively. The water use efficiency slopes were dominated by the evapotranspiration slopes at elevations below 1999 m but were controlled by the gross primary productivity slopes at elevations above 2000 m. This difference was caused by the substantial responses of evaporation to climate change at lower elevations and the increased climatic sensitivity of gross primary productivity at higher elevations. In comparison to those at other elevations, croplands at lower elevations were more vulnerable to extreme drought because of the dominant role fluctuating evapotranspiration played in water use efficiency. The findings will improve cropland water management in the study area.展开更多
The effects of climatic warming on phyllosphere microbial communities remain uncertain.In this study,the effects of long-term(>10 years)experimental warming on phyllosphere epiphytic bacterial and fungal communitie...The effects of climatic warming on phyllosphere microbial communities remain uncertain.In this study,the effects of long-term(>10 years)experimental warming on phyllosphere epiphytic bacterial and fungal communities of Carex alrofusca,Kobresia pygmaea,Potentilla bifurca and Stipa capillacea were examined in the northern Xizang.Overall,warming increased bacterialα-diversity,but reduced fungalα-diversity across the four host plants.Warming altered the bacterial and fungal community compositions mainly by increasing Actinobacteria,Firmicutes and pathotrophsaprotroph fungi,and reducing Basidiomycota and symbiotroph fungi across the four host plants.Warming increased the relative effect of the‘drift&others’process in the bacterial community,but reduced the relative effect of the‘dispersal limitation’process in the bacterial community and the relative effect of the‘homogeneous selection’process in the fungal community across the four host plants.The overall warming effects on the bacterial and fungal communities may be due to overall warming effects on temperature,leaf morphology structure and physicochemical properties,ecological processes of community assembly and topological parameters of species co-occurrence networks of bacteria and fungi.Warming altered the bacterial species co-occurrence network mainly by increasing the vertex,clustering coefficient and heterogeneity,while reducing the average path length and network diameter across host species.Warming altered the fungal species co-occurrence network mainly by increasing the network diameter and reducing the vertex across host species.Warming effects on bacterial and fungal communities varied among host plants,which may be due to the diverse responses to warming of plant height,leaf malondialdehyde,ecological processes of community assembly and topological parameters of species co-occurrence network.Therefore,warming can alter phyllosphere epiphytic bacterial and fungal communities of alpine plants.Such changes varied among host plants and may cause adverse effects on the host plants.展开更多
Poyang Lake,China's largest freshwater lake,is a critical wintering ground for most of the global Siberian Grane(Grus leucogeranus)population.However,increasingly prolonged dry seasons have degraded the natural we...Poyang Lake,China's largest freshwater lake,is a critical wintering ground for most of the global Siberian Grane(Grus leucogeranus)population.However,increasingly prolonged dry seasons have degraded the natural wetlands of Poyang Lake,forcing Siberian Cranes to shift to artificial habitats.From 2015 to 2023,field surveys revealed a substantial increase in the number of Siberian Cranes in artificial habitats,with peak counts reaching 3000individuals,accounting for up to 53%of the species'global population.Satellite telemetry of 13 individuals further confirmed the spatial use of these habitats,highlighting their consistent reliance on artificial sites over multiple years.Seven high-use hotspots were identified outside of Poyang Lake,including two artificial provisioning sites that supported dense foraging flocks for extended periods.Satellite telemetry confirmed this trend,with artificial habitats making up to 64.2%of the occurrence sites in some years.This reliance on artificial habitats was closely linked to the reduced tuber biomass in natural wetlands and low winter water levels in Poyang Lake,which collectively explained 83%of the variance in crane abundance in artificial habitats.Artificial habitat use peaked in December and January,indicating marked seasonal variation.Siberian Cranes also exhibited a pronounced circadian rhythm,foraging in artificial habitats during the day and returning to natural wetlands to roost at night.Despite the shift toward artificial habitats,natural wetlands remain critical for nighttime refuge.The continued dependence on artificial habitats raises concerns about disease transmission owing to dense congregations.Conservation strategies should prioritize both the careful management of artificial provisioning sites and the restoration of natural wetlands to improve food and habitat availability within natural ecosystems,ultimately enabling the return of Siberian Cranes to their traditional natural habitats.展开更多
Drought significantly constrains vegetation growth and reduces terrestrial carbon sinks.Currently,the spatiotemporal patterns and mechanisms of the differential impacts of soil and meteorological droughts on vegetatio...Drought significantly constrains vegetation growth and reduces terrestrial carbon sinks.Currently,the spatiotemporal patterns and mechanisms of the differential impacts of soil and meteorological droughts on vegetation productivity remain inadequately understood.In this study,we analyzed soil moisture(SM),vapor pressure deficit(VPD),and gross primary productivity(GPP)to investigate their spatiotemporal patterns and the combined effects on GPP over China.The results revealed that:(1)Soil drought and meteorological drought generally exhibited temporally synchronous trends across China.(2)GPP was predominantly affected by the combined and synchronous effects of both SM and VPD,although their effects displayed directional variability differences in certain regions.(3)SM demonstrated a greater relative importance on GPP than VPD across more than half of the regions in China,whereas deciduous broadleaf forests were the only vegetation type primarily affected by VPD.(4)Under the lag effects,both SM and VPD exhibited bidirectional Granger causality with GPP,with the interaction between VPD and GPP proving more pronounced than that of SM.Our research provides valuable insights into the mechanisms through which SM and VPD influence GPP,contributing to improved predictions vegetation productivity and implementing ecological restoration.展开更多
The land application of livestock manure has been widely acknowledged as a beneficial approach for nutrient recycling and environmental protection.However,the impact of residual antibiotics,a common contaminant of man...The land application of livestock manure has been widely acknowledged as a beneficial approach for nutrient recycling and environmental protection.However,the impact of residual antibiotics,a common contaminant of manure,on the degradation of organic compounds and nutrient release in Eutric Regosol is not well understood.Here,we studied,how oxytetracycline(OTC)and ciprofloxacin(CIP)affect the decomposition,microbial community structure,extracellular enzyme activities and nutrient release from cattle and pig manure using litterbag incubation experiments.Results showed that OTC and CIP greatly inhibited livestock manure decomposition,causing a decreased rate of carbon(28%-87%),nitrogen(15%-44%)and phosphorus(26%-43%)release.The relative abundance of gramnegative(G-)bacteria was reduced by 4.0%-13%while fungi increased by 7.0%-71%during a 28-day incubation period.Co-occurrence network analysis showed that antibiotic exposure disrupted microbial interactions,particularly among G-bacteria,G+bacteria,and actinomycetes.These changes in microbial community structure and function resulted in decreased activity of urease,β-1,4-N-acetyl-glucosaminidase,alkaline protease,chitinase,and catalase,causing reduced decomposition and nutrient release in cattle and pig ma-nures.These findings advance our understanding of decomposition and nutrient recycling from manure-contaminated antibiotics,which will help facilitate sustainable agricultural production and soil carbon sequestration.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
Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and dr...Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and drying. It is essential to investigate the effects of climatic change （temperature and precipitation） on vegetation dynamics for a better understanding of climatic change. NDVI （Normalized Difference Vegetation Index）, reflecting characteristics of plant growth, vegetation coverage and biomass, is used as an indicator to monitor vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation changes in Hulun Buir Grassland. The responses of vegetation coverage to climatic change on the yearly, seasonal and monthly scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage was more correlated with climatic factors, and the correlations were dependent on the time scales. On an inter-annual scale, vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation changes. On a seasonal-interannual scale, correlations between vegetation coverage change and climatic factors showed that the sensitivity of vegetation growth to the aqueous and thermal condition changes was different in different seasons. The sensitivity of vegetation growth to temperature in summers was higher than in the other seasons, while its sensitivity to rainfall in both summers and autumns was higher, especially in summers. On a monthly-interannual scale, correlations between vegetation coverage change and climatic factors during growth seasons showed that the response of vegetation changes to temperature in both April and May was stronger. This indicates that the temperature effect occurs in the early stage of vegetation growth. Correlations between vegetation growth and precipitation of the month before the current month, were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses get green and begin to grow in April, and the impacts of temperature on grass growth are obvious. The increase of NDVI in April may be due to climatic warming that leads to an advanced growth season. In summary, relationships between monthly-interannual variations of vegetation coverage and climatic factors represent the temporal rhythm controls of temperature and precipitation on grass growth largely.展开更多
Negative soil water balance （i.e., water input 〈 water output） can lead to soil desiccation and subsequently the occurrence of a dried soil layer （DSL）. The DSLs are generally studied at a specific sampling depth...Negative soil water balance （i.e., water input 〈 water output） can lead to soil desiccation and subsequently the occurrence of a dried soil layer （DSL）. The DSLs are generally studied at a specific sampling depth （e.g., 500 cm）, and the actual extent of DSLs remains unknown due to the challenge of collecting deep soil samples. To investigate the characteristics of actual DSLs under different ages of apple orchards and ascertain the optimal age of apple orchards for avoiding/controlling the formation of DSLs, soil samples were collected to a depth of 1800 cm under apple orchards of different ages in Changwu on the Loess Plateau of China. As the ages increased, soil water content （SWC） and mean SWC in DSLs showed an overall decreasing trend, whereas while DSL thickness and the quantity of water deficit （QWD） in DSLs demonstrated an increasing trend. The DSL was the thickest （1 600 cm） under the 17-yeax-old orchard, the forming velocity of DSL thickness was the highest at the apple tree growth stage of 9-17 years （168 cm year-l）, and the highest increasing velocity of QWD （-181 mm year-1） was also observed at this stage. The thickness of DSL was significantly correlated with growth age and root depth of apple trees （r 〉 0.88）, whereas the QWD and mean SWC in DSLs were found to have no correlation with them. The optimal age of apple orchards for avoiding/controlling the formation of DSLs was about 9 years. This information provided pertinent references for the management of deep water resources by controlling the growth age of plants. Key Words： deep soil, growth age, plant roots, soil desiccation, soil water content, soil-plant water relation.展开更多
Water shortage is a key constraint to sustainable agricultural production in Xinjiang, Northwest China. To enhance the use efficiency of valuable irrigation water resources, a 2-year experiment(2010–2011) was conduct...Water shortage is a key constraint to sustainable agricultural production in Xinjiang, Northwest China. To enhance the use efficiency of valuable irrigation water resources, a 2-year experiment(2010–2011) was conducted to quantify the response of cotton(Gossypium hirsutum L.) growth and yield to different degrees of deficit irrigation(DI) regimes; to determine the effects of DI on the characteristics of water use for cotton, seasonal water use, available soil water in the root zone, soil water depletion, evapotranspiration(ET)-based water use efficiency and irrigation-based water use efficiency, and to determine the best DI regime for optimal water-saving and yield output. The plots were irrigated at 100%(100ET), 85%(85ET), 70%(70ET), 55%(55ET) and 45%(45ET) of the regional ET of cotton in northern Xinjiang. The effect of DI irrigation on water use characteristics was evaluated by analyzing available soil water and soil water depletion in the root zone along with water use efficiencies of cotton. The study showed that the growth, water use characteristics and yield of cotton varied with irrigation regime. Seasonal ET and seed cotton yield were linearly correlated with irrigation amount. The second-order polynomial equation best approximated water-yield relationship of cotton in the study area.Cotton yield response factor was 0.65, suggesting limited water conditions were suitable for cotton cultivation. Economic evaluation of DI treatments confirmed that the yield loss was less than 10% under 70 ET and 85 ET, which was acceptable for greater sustainability.The results suggested that proper DI schemes were necessary for sustainable cotton production in the region. While irrigation at 85 ET was safe for high cotton yield, irrigation at 70 ET was a viable alternative under limited irrigation water availability.展开更多
基金supported by the National Natural Science Foundation of China(No.42225103).
文摘Lakes are carbon dioxide(CO_(2))and methane(CH_(4))emission hotspots,whose associated flux is spatially vari-able.Many studies have investigated the impact of microorganisms and environmental factors on CO_(2) and CH_(4) emissions between different lakes.However,the carbon emissions and their influencing factors of different areas within a single lake remain poorly understood.Accordingly,this study investigates CO_(2) and CH_(4) emission hetero-geneity in a large floodplain lake system and distribution characteristics of associated functional microorganisms.Findings show that mean CO_(2) and CH_(4) flux values in the sub lake area were 62.03±24.21 mg/(m2·day)and 5.97±3.2μg/(m2·day),which were greater by factors of 1.78 and 2.96 compared to the water channel and the main lake area,respectively.The alpha diversity of methanogens in the sub lake area was lower than that in the main lake and water channel areas.The abundance of methanogens in bottom water layer was higher compared with the middle and surface layers.Conversely,the abundance of methane(CH_(4))-oxidizing bacteria in the surface layer was higher than that in the bottom layer.Additionally,the composition of methanogen and CH_(4)-oxidizing bacterial community,chlorophyll a(Chl-a),pH,total phosphorus(TP)and dissolved organic carbon(DOC)con-tent constituted the dominate driving factors affecting lake C emissions.Results from this study can be used to improve our understanding of lake spatial heterogeneous of CO_(2) and CH_(4) emission and the driving mechanisms within floodplain lakes under the coupling effects of functional C microorganisms and environmental factors.
基金Science and Technology Service Network Initiative of CAS,No.KFJ-SW-STS-169National Natural Science Foundation of China,No.31420103917
文摘Eddy Covariance technique(EC) achieves the direct measurement on ecosystem carbon, nitrogen and water fluxes, and it provides scientific data for accurately assessing ecosystem functions in mitigating global climate change. This paper briefly reviewed the construction and development of Chinese terrestrial ecosystem flux observation and research network(China FLUX), and systematically introduced the design principle and technology of the terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation system of China FLUX. In addition, this paper summarized the main progress of China FLUX in the ecosystem carbon, nitrogen and water exchange and environmental controlling mechanisms, the spatial pattern of carbon, nitrogen and water fluxes and biogeographical mechanisms, and the regional terrestrial ecosystem carbon budget assessment. Finally, the prospects and emphases of the terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation of China FLUX are put forward to provide theoretical references for the development of flux observation and research in China.
基金National Natural Science Foundation of China No.30590381 No.31000211 National Basic Research Program of China No.2010CB833504
文摘From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency （WUE） and nitrogen use efficiency （NUE）, and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed： （1） vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. （2） Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE （p0.001）. While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE （p0.001）. Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. （3） There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC （p0.001）, indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.
基金under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05050702)National Natural Science Foundation of China(No.31270519,31470506)Kezhen Distinguished Talents in Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences(No.2013RC102)
文摘Characterization of the vertical distribution of soil organic carbon(C), nitrogen(N), and phosphorus(P) may improve our ability to accurately estimate soil C, N, and P storage. Based on a database of 21 354 records in 74 long-term monitoring plots from 2004 to 2013 in the Chinese Ecosystem Research Network(CERN), we built fitting functions to quantify the vertical distribution of soil C, N, and P(up to 100 cm depth) in the typical Chinese terrestrial ecosystems. The decrease of soil C, N, and P content with depth can be well fitted with various mathematical functions. The fitting functions differed greatly between artificial(agriculture) and natural(desert, forest, and grassland) ecosystems, and also differed with respect to soil C, N, and P content. In both the artificial and natural ecosystems, the best fitting functions were exponential functions for C, quadratic functions for N, and quadratic functions for P. Furthermore, the stoichiometric ratios of soil C, N, and P were ranked in descending order: grassland > forest > agriculture > desert, and were also associated with climate. This study is the first to build the fitting functions for the profile distribution of soil C, N, and P in China at a national scale. Our findings provide a scientific basis to accurately assess the storage of C, N, and P in soils at a large scale, especially for the integrative analysis of historical data.
基金funded by the National Natural Science Foundation of China (Grant Nos. 41171084and 40771121)Innovation Project of the Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences (Grant No.2012ZD005)+2 种基金the Natural Science Foundation of the Tibet Autonomous Region (Name. the Response Experiment of the Alpine Meadow Vegetation to Climate Warming)the National Basic Research Program of China (Grant No.2010CB951704)the National Science and Technology Plan Project of China (Grant No.2011BAC09B03)
文摘The alpine meadow, as one of the typical vegetation types on the Tibetan Plateau, is one of the most sensitive terrestrial ecosystems to climate warming. However, how climate warming affects the carbon cycling of the alpine meadow on the Tibetan Plateau is not very dear. A field experiment under controlled experimental warming and clipping conditions was conducted in an alpine meadow on the Northern Tibetan Plateau since July 2008. Open top chambers （0TCs） were used to simulate climate warming. The main objective of this study was to examine the responses of ecosystem respiration （Reco） and its temperature sensitivity to experimental warming and clipping at daily time scale. Therefore, we measured Reco once or twice a month from July to September in 2010, from June to September in 2011 and from August to September in 2012. Air temperature dominated daily variation of Reco whether or not experimental warming and clipping were present. Air temperature was exponentially correlated with Reco and it could significantly explain 58-96% variation of Redo at daily time scale. Experimental warming and clipping decreased daily mean Reco by 5.8-37.7% and -11.9-23.0%, respectively, although not all these changes were significant. Experimental warming tended to decrease the temperature sensitivity of Reco, whereas clipping tended to increase the temperature sensitivity of Reco at daily time scale. Our findings suggest that Reco wasmainly controlled by air temperature and may acclimate to climate warming due to its lower temperature sensitivity under experimental warming at daily time scale.
基金The work was supported by the National Natural Science Foundation of China(Nos.31600347 and 41501381)National Key Research and Development Program of China(No.2016YFA0600103)International Partnership Program of Chinese Academy of Sciences(No.121311KYSB20170004).
文摘Afforestation is believed to be an effective practice to reduce global warming by sequestering large amounts of carbon in plant biomass and soil.However,the factors that determine the rate of carbon sequestration with afforestation are still poorly understood.We analyzed ecosystem carbon exchange after afforestation based on eddy covariance measurements with the aim to identify factors responsible for the rate of carbon exchange following afforestation.The results indicated that afforestation in the tropical/subtropical and temperate climate zones had greater capacities for carbon sequestration than those in boreal zones.Net ecosystem production(NEP),gross primary production(GPP)and ecosystem respiration(RE)varied greatly with age groups over time.Specifically,NEP was initially less than zero in the\10 year group and then increased to its peak in the 10-20 year group.Afforestation of varied previous land use types and planting of diverse tree species did not result in different carbon fluxes.The general linear model showed that climate zone and age of afforestation were the dominant factors influencing carbon sequestration.These factors jointly controlled 51%,61%and 63%of the variation in NEP,GPP and RE,respectively.Compared to the strong regulation of climate on GPP and RE,NEP showed greater sensitivity to the age of afforestation.These results increase our understanding of the variation in ecosystem carbon exchange of afforestation and suggest that afforestation in subtropical and temperate areas after 20 years would yield greater carbon sink benefits than would afforestation of boreal regions.
基金Under the auspices of Major State Basic Research Development Program of China(No.2010CB833504)Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05050601)
文摘A continuous three-year observation(from May 2008 to April 2011)was conducted to characterize the spatial variation of dissolved inorganic nitrogen(DIN)deposition at eight main forest ecosystems along the north-south transect of eastern China(NSTEC).The results show that both throughfall DIN deposition and bulk DIN deposition increase from north to south along the NSTEC.Throughfall DIN deposition varies greatly from 2.7 kg N/(ha·yr)to 33.0 kg N/(ha·yr),with an average of 10.6 kg N/(ha·yr),and bulk DIN deposition ranges from 4.1 kg N/(ha·yr)to 25.4 kg N/(ha·yr),with an average of 9.8 kg N/(ha·yr).NH4+-N is the dominant form of DIN deposition at most sampling sites.Additionally,the spatial variation of DIN deposition is controlled mainly by precipitation.Moreover,in the northern part of the NSTEC,bulk DIN deposition is 17%higher than throughfall DIN deposition,whereas the trend is opposite in the southern part of the NSTEC.The results demonstrate that DIN deposition would likely threaten the forest ecosystems along the NSTEC,compared with the critical loads(CL)of N deposition,and DIN deposition in this region is mostly controlled by agricultural activities rather than industrial activities or transportation.
基金jointly supported by the National Natural Science Foundation of China(31400425,31570437,41301043,31420103917)the National Key Project of Scientific and Technical Supporting Program(2013BAC03B03)+1 种基金the Funding for Talented Young Scientists of IGSNRR(2013RC203)the Social Foundation of Beijing Academy of Social Sciences(154005)
文摘Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about to what extent grassland productivity will respond to an individual precipitation event. In this study, we quantified the duration, the maximum, and the time-integrated amount of the response of daily gross primary productivity (GPP) to an individual precipitation event and their variations with different sizes of precipitation events in a typical temperate steppe in Inner Mongolia, China. Results showed that the duration of GPP-response (τ<sub>R</sub>) and the maximum absolute GPP-response (GPP<sub>max</sub>) increased linearly with the sizes of precipitation events (P<sub>es</sub>), driving a corresponding increase in time-integrated amount of the GPP-response (GPP<sub>total</sub>) because variations of GPPtotal were largely explained by τ<sub>R</sub> and GPP<sub>max</sub>. The relative contributions of these two parameters to GPP<sub>total</sub> were strongly P<sub>es</sub>-dependent. The GPP<sub>max</sub> contributed more to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively small (<20 mm), whereas τ<sub>R</sub> was the main driver to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively large. In addition, a threshold size of at least 5 mm of precipitation was required to induce a GPP-response for the temperate steppe in this study. Our work has important implications for the modeling community to obtain an advanced understanding of productivity-response of grassland ecosystems to altered precipitation regimes.
基金funded by the National Key R&D Program of China(Grant No.2021YFD1500200)National Natural Science Foundation of China(Grant No.42077149)+4 种基金China Postdoctoral Science Foundation(Grant No.2019M660782)National Science and Technology Basic Resources Survey Program of China(Grant No.2019FY101300)Doctoral research start-up fund project of Liaoning Provincial Department of Science and Technology(Grant No.2021-BS-136)China Scholarship Council(201908210132)Young Scientific and Technological Talents Project of Liaoning Province(Grant Nos.LSNQN201910 and LSNQN201914)。
文摘Forest soil carbon is a major carbon pool of terrestrial ecosystems,and accurate estimation of soil organic carbon(SOC)stocks in forest ecosystems is rather challenging.This study compared the prediction performance of three empirical model approaches namely,regression kriging(RK),multiple stepwise regression(MSR),random forest(RF),and boosted regression trees(BRT)to predict SOC stocks in Northeast China for 1990 and 2015.Furthermore,the spatial variation of SOC stocks and the main controlling environmental factors during the past 25 years were identified.A total of 82(in 1990)and 157(in 2015)topsoil(0–20 cm)samples with 12 environmental factors(soil property,climate,topography and biology)were selected for model construction.Randomly selected80%of the soil sample data were used to train the models and the other 20%data for model verification using mean absolute error,root mean square error,coefficient of determination and Lin's consistency correlation coefficient indices.We found BRT model as the best prediction model and it could explain 67%and 60%spatial variation of SOC stocks,in 1990,and 2015,respectively.Predicted maps of all models in both periods showed similar spatial distribution characteristics,with the lower SOC in northeast and higher SOC in southwest.Mean annual temperature and elevation were the key environmental factors influencing the spatial variation of SOC stock in both periods.SOC stocks were mainly stored under Cambosols,Gleyosols and Isohumosols,accounting for 95.6%(1990)and 95.9%(2015).Overall,SOC stocks increased by 471 Tg C during the past 25 years.Our study found that the BRT model employing common environmental factors was the most robust method for forest topsoil SOC stocks inventories.The spatial resolution of BRT model enabled us to pinpoint in which areas of Northeast China that new forest tree planting would be most effective for enhancing forest C stocks.Overall,our approach is likely to be useful in forestry management and ecological restoration at and beyond the regional scale.
基金funded by the National Natural Science Foundation of China (41977399)the National Key Research and Development Program (2017YFC0505800)
文摘Air pollution has seriously endangered human health and the natural ecosystem during the last decades.Air quality monitoring stations(AQMS)have played a critical role in providing valuable data sets for recording regional air pollutants.The spatial representativeness of AQMS is a critical parameter when choosing the location of stations and assessing effects on the population to long-term exposure to air pollution.In this paper,we proposed a methodological framework for assessing the spatial representativeness of the regional air quality monitoring network and applied it to ground-based PM_(2.5)observation in the mainland of China.Weighted multidimensional Euclidean distance between each pixel and the stations was used to determine the representativeness of the existing monitoring network.In addition,the K-means clustering method was adopted to improve the spatial representativeness of the existing AQMS.The results showed that there were obvious differences among the representative area of 1820 stations in the mainland of China.The monitoring stations could well represent the PM_(2.5)spatial distribution of the entire region,and the effectively represented area(i.e.the area where the Euclidean distance between the pixels and the stations was lower than the average value)accounted for 67.32%of the total area and covered 93.12%of the population.Forty additional stations were identified in the Northwest,North China,and Northeast regions,which could improve the spatial representativeness by 14.31%.
基金National Key Research and Development Program of China,No.2015CB954102National Natural Science Foundation of China,No.31700417,No.41571424
文摘The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction between ecosystem carbon uptake and water cycling in the context of global change.The estimation of T/ET has been paid increasing attention from the scientific community in recent years globally.In this paper,we used the Priestly-Taylor Jet Propulsion Laboratory Model (PT-JPL) driven by regional remote sensing data and gridded meteorological data,to simulate the T/ET in forest ecosystems along the North-South Transect of East China (NSTEC) during 2001-2010,and to analyze the spatial distribution and temporal variation of T/ET,as well as the factors influencing the variation in T/ET.The results showed that:(1) The PT-JPL model is suitable for the simulation of evapotranspiration and its components of forest ecosystems in Eastern China,and has relatively good stability and reliability.(2) Spatial distribution of T/ET in forest ecosystems along NSTEC was heterogeneous,i.e.,T/ET was higher in the north and lower in the south,with an averaged value of 0.69;and the inter-annual variation of T/ET showed a significantly increasing trend,with an increment of 0.007/yr (p<0.01).(3) Seasonal and inter- annual variations of T/ET had different dominant factors.Temperature and EVI can explain around 90%(p<0.01) of the seasonal variation in T/ET,while the inter-annual variation in T/ET was mainly controlled by EVI (53%,p<0.05).
基金National Natural Science Foundation of China,No.41501054Scientific Research Foundation of Shandong Technology and Business University,No.BS201735Key Research Program of Frontier Sciences of the Chinese Academy of Sciences,No.QYZDB-SSW-DQC005。
文摘Understanding climatic effects on cropland water use efficiency at different elevations is imperative for managing agricultural water and production in response to ongoing climate change in climate-sensitive areas with complex topography, such as southwestern China. We investigated climatic effects on cropland water use efficiency in southwestern China at each 100-m elevation bin during 2001–2017. The maximum water use efficiency was 1.71 gC kg^(–1) H_2O for the 1900–1999 m elevation bin under the growing season temperature and precipitation of 14.58±0.32℃ and 965.40±136.45 mm, respectively. The water use efficiency slopes were dominated by the evapotranspiration slopes at elevations below 1999 m but were controlled by the gross primary productivity slopes at elevations above 2000 m. This difference was caused by the substantial responses of evaporation to climate change at lower elevations and the increased climatic sensitivity of gross primary productivity at higher elevations. In comparison to those at other elevations, croplands at lower elevations were more vulnerable to extreme drought because of the dominant role fluctuating evapotranspiration played in water use efficiency. The findings will improve cropland water management in the study area.
基金funded by the Pilot Project of Chinese Academy of Sciences(XDA26050501)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2020054)+3 种基金the National Natural Science Foundation of China(31600432)the Lhasa Science and Technology Plan Project,China(LSKJ202422)the Tibet Autonomous Region Science and Technology Project,China(XZ202401JD0029)the Construction of Zhongba County Fixed Observation and Experiment Station of First Support System for Agriculture Green Development,China。
文摘The effects of climatic warming on phyllosphere microbial communities remain uncertain.In this study,the effects of long-term(>10 years)experimental warming on phyllosphere epiphytic bacterial and fungal communities of Carex alrofusca,Kobresia pygmaea,Potentilla bifurca and Stipa capillacea were examined in the northern Xizang.Overall,warming increased bacterialα-diversity,but reduced fungalα-diversity across the four host plants.Warming altered the bacterial and fungal community compositions mainly by increasing Actinobacteria,Firmicutes and pathotrophsaprotroph fungi,and reducing Basidiomycota and symbiotroph fungi across the four host plants.Warming increased the relative effect of the‘drift&others’process in the bacterial community,but reduced the relative effect of the‘dispersal limitation’process in the bacterial community and the relative effect of the‘homogeneous selection’process in the fungal community across the four host plants.The overall warming effects on the bacterial and fungal communities may be due to overall warming effects on temperature,leaf morphology structure and physicochemical properties,ecological processes of community assembly and topological parameters of species co-occurrence networks of bacteria and fungi.Warming altered the bacterial species co-occurrence network mainly by increasing the vertex,clustering coefficient and heterogeneity,while reducing the average path length and network diameter across host species.Warming altered the fungal species co-occurrence network mainly by increasing the network diameter and reducing the vertex across host species.Warming effects on bacterial and fungal communities varied among host plants,which may be due to the diverse responses to warming of plant height,leaf malondialdehyde,ecological processes of community assembly and topological parameters of species co-occurrence network.Therefore,warming can alter phyllosphere epiphytic bacterial and fungal communities of alpine plants.Such changes varied among host plants and may cause adverse effects on the host plants.
基金supported by the National Natural Science Foundation of China(No.32260275)Fundamental Research Funds of CAF(CAFYBB2024ZA033)。
文摘Poyang Lake,China's largest freshwater lake,is a critical wintering ground for most of the global Siberian Grane(Grus leucogeranus)population.However,increasingly prolonged dry seasons have degraded the natural wetlands of Poyang Lake,forcing Siberian Cranes to shift to artificial habitats.From 2015 to 2023,field surveys revealed a substantial increase in the number of Siberian Cranes in artificial habitats,with peak counts reaching 3000individuals,accounting for up to 53%of the species'global population.Satellite telemetry of 13 individuals further confirmed the spatial use of these habitats,highlighting their consistent reliance on artificial sites over multiple years.Seven high-use hotspots were identified outside of Poyang Lake,including two artificial provisioning sites that supported dense foraging flocks for extended periods.Satellite telemetry confirmed this trend,with artificial habitats making up to 64.2%of the occurrence sites in some years.This reliance on artificial habitats was closely linked to the reduced tuber biomass in natural wetlands and low winter water levels in Poyang Lake,which collectively explained 83%of the variance in crane abundance in artificial habitats.Artificial habitat use peaked in December and January,indicating marked seasonal variation.Siberian Cranes also exhibited a pronounced circadian rhythm,foraging in artificial habitats during the day and returning to natural wetlands to roost at night.Despite the shift toward artificial habitats,natural wetlands remain critical for nighttime refuge.The continued dependence on artificial habitats raises concerns about disease transmission owing to dense congregations.Conservation strategies should prioritize both the careful management of artificial provisioning sites and the restoration of natural wetlands to improve food and habitat availability within natural ecosystems,ultimately enabling the return of Siberian Cranes to their traditional natural habitats.
基金National Key Research and Development Program,No.2021xjkk0303。
文摘Drought significantly constrains vegetation growth and reduces terrestrial carbon sinks.Currently,the spatiotemporal patterns and mechanisms of the differential impacts of soil and meteorological droughts on vegetation productivity remain inadequately understood.In this study,we analyzed soil moisture(SM),vapor pressure deficit(VPD),and gross primary productivity(GPP)to investigate their spatiotemporal patterns and the combined effects on GPP over China.The results revealed that:(1)Soil drought and meteorological drought generally exhibited temporally synchronous trends across China.(2)GPP was predominantly affected by the combined and synchronous effects of both SM and VPD,although their effects displayed directional variability differences in certain regions.(3)SM demonstrated a greater relative importance on GPP than VPD across more than half of the regions in China,whereas deciduous broadleaf forests were the only vegetation type primarily affected by VPD.(4)Under the lag effects,both SM and VPD exhibited bidirectional Granger causality with GPP,with the interaction between VPD and GPP proving more pronounced than that of SM.Our research provides valuable insights into the mechanisms through which SM and VPD influence GPP,contributing to improved predictions vegetation productivity and implementing ecological restoration.
基金supported by the National Natural Science Foundation of China(No.U20A2047)the Key Research and Development Project for Tibet Autonomous Region(No.XZ202201ZY0003N)+2 种基金the National Key Research and Development Program of China(No.2022YFD1901402)the Lasa Science and Technology Bureau(No.LSKJ202206)the Foundation of Graduate Research and Innovation in Chongqing(No.CYB22127).
文摘The land application of livestock manure has been widely acknowledged as a beneficial approach for nutrient recycling and environmental protection.However,the impact of residual antibiotics,a common contaminant of manure,on the degradation of organic compounds and nutrient release in Eutric Regosol is not well understood.Here,we studied,how oxytetracycline(OTC)and ciprofloxacin(CIP)affect the decomposition,microbial community structure,extracellular enzyme activities and nutrient release from cattle and pig manure using litterbag incubation experiments.Results showed that OTC and CIP greatly inhibited livestock manure decomposition,causing a decreased rate of carbon(28%-87%),nitrogen(15%-44%)and phosphorus(26%-43%)release.The relative abundance of gramnegative(G-)bacteria was reduced by 4.0%-13%while fungi increased by 7.0%-71%during a 28-day incubation period.Co-occurrence network analysis showed that antibiotic exposure disrupted microbial interactions,particularly among G-bacteria,G+bacteria,and actinomycetes.These changes in microbial community structure and function resulted in decreased activity of urease,β-1,4-N-acetyl-glucosaminidase,alkaline protease,chitinase,and catalase,causing reduced decomposition and nutrient release in cattle and pig ma-nures.These findings advance our understanding of decomposition and nutrient recycling from manure-contaminated antibiotics,which will help facilitate sustainable agricultural production and soil carbon sequestration.
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.
基金Open Project of Hulun Buir Grassland Ecosystem Observation and Research Station, No.2010-10Open Project of Ministry of Agriculture Key Laboratory of Resource Remote Sensing and Digital Agriculture, No.RDA0803+1 种基金 No.RDA0903Basic Research Project of the Ministry of Science and Technology, No.2007FY110300
文摘Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and drying. It is essential to investigate the effects of climatic change （temperature and precipitation） on vegetation dynamics for a better understanding of climatic change. NDVI （Normalized Difference Vegetation Index）, reflecting characteristics of plant growth, vegetation coverage and biomass, is used as an indicator to monitor vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation changes in Hulun Buir Grassland. The responses of vegetation coverage to climatic change on the yearly, seasonal and monthly scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage was more correlated with climatic factors, and the correlations were dependent on the time scales. On an inter-annual scale, vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation changes. On a seasonal-interannual scale, correlations between vegetation coverage change and climatic factors showed that the sensitivity of vegetation growth to the aqueous and thermal condition changes was different in different seasons. The sensitivity of vegetation growth to temperature in summers was higher than in the other seasons, while its sensitivity to rainfall in both summers and autumns was higher, especially in summers. On a monthly-interannual scale, correlations between vegetation coverage change and climatic factors during growth seasons showed that the response of vegetation changes to temperature in both April and May was stronger. This indicates that the temperature effect occurs in the early stage of vegetation growth. Correlations between vegetation growth and precipitation of the month before the current month, were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses get green and begin to grow in April, and the impacts of temperature on grass growth are obvious. The increase of NDVI in April may be due to climatic warming that leads to an advanced growth season. In summary, relationships between monthly-interannual variations of vegetation coverage and climatic factors represent the temporal rhythm controls of temperature and precipitation on grass growth largely.
基金supported by the National Natural Science Foundation of China (No. 41471189)the Youth Science and Technology New Star Foundation of Shaanxi Province, China (No. 2013KJXX-09)+1 种基金the CAS "Light of West China" Programthe Youth Innovation Promotion Association CAS
文摘Negative soil water balance （i.e., water input 〈 water output） can lead to soil desiccation and subsequently the occurrence of a dried soil layer （DSL）. The DSLs are generally studied at a specific sampling depth （e.g., 500 cm）, and the actual extent of DSLs remains unknown due to the challenge of collecting deep soil samples. To investigate the characteristics of actual DSLs under different ages of apple orchards and ascertain the optimal age of apple orchards for avoiding/controlling the formation of DSLs, soil samples were collected to a depth of 1800 cm under apple orchards of different ages in Changwu on the Loess Plateau of China. As the ages increased, soil water content （SWC） and mean SWC in DSLs showed an overall decreasing trend, whereas while DSL thickness and the quantity of water deficit （QWD） in DSLs demonstrated an increasing trend. The DSL was the thickest （1 600 cm） under the 17-yeax-old orchard, the forming velocity of DSL thickness was the highest at the apple tree growth stage of 9-17 years （168 cm year-l）, and the highest increasing velocity of QWD （-181 mm year-1） was also observed at this stage. The thickness of DSL was significantly correlated with growth age and root depth of apple trees （r 〉 0.88）, whereas the QWD and mean SWC in DSLs were found to have no correlation with them. The optimal age of apple orchards for avoiding/controlling the formation of DSLs was about 9 years. This information provided pertinent references for the management of deep water resources by controlling the growth age of plants. Key Words： deep soil, growth age, plant roots, soil desiccation, soil water content, soil-plant water relation.
基金supported by the National Natural Science Foundation of China (No. 41371115)the 100 Talents Program of Chinese Academy of Sciences (No. KZXC2-YW-BR-12)
文摘Water shortage is a key constraint to sustainable agricultural production in Xinjiang, Northwest China. To enhance the use efficiency of valuable irrigation water resources, a 2-year experiment(2010–2011) was conducted to quantify the response of cotton(Gossypium hirsutum L.) growth and yield to different degrees of deficit irrigation(DI) regimes; to determine the effects of DI on the characteristics of water use for cotton, seasonal water use, available soil water in the root zone, soil water depletion, evapotranspiration(ET)-based water use efficiency and irrigation-based water use efficiency, and to determine the best DI regime for optimal water-saving and yield output. The plots were irrigated at 100%(100ET), 85%(85ET), 70%(70ET), 55%(55ET) and 45%(45ET) of the regional ET of cotton in northern Xinjiang. The effect of DI irrigation on water use characteristics was evaluated by analyzing available soil water and soil water depletion in the root zone along with water use efficiencies of cotton. The study showed that the growth, water use characteristics and yield of cotton varied with irrigation regime. Seasonal ET and seed cotton yield were linearly correlated with irrigation amount. The second-order polynomial equation best approximated water-yield relationship of cotton in the study area.Cotton yield response factor was 0.65, suggesting limited water conditions were suitable for cotton cultivation. Economic evaluation of DI treatments confirmed that the yield loss was less than 10% under 70 ET and 85 ET, which was acceptable for greater sustainability.The results suggested that proper DI schemes were necessary for sustainable cotton production in the region. While irrigation at 85 ET was safe for high cotton yield, irrigation at 70 ET was a viable alternative under limited irrigation water availability.
