Vegetation in terrestrial ecosystems as a carbon sink is a crucial factor in mitigating global warming and reaching carbon neutrality targets,although the drivers of net ecosystem productivity(NEP)under combined human...Vegetation in terrestrial ecosystems as a carbon sink is a crucial factor in mitigating global warming and reaching carbon neutrality targets,although the drivers of net ecosystem productivity(NEP)under combined human and environmental pressures remain poorly understood.In this study,we analyzed the spatiotemporal evolution of NEP in the Horqin Sandy Land,China from 2000 to 2020,and observed the variation in NEP across different land use types.We further identified and quantified the effects of human activities,topographical features,climatic conditions,and soil properties on NEP through the application of structural equation modeling(SEM)and boosted regression trees(BRT).The results showed that the multi-year average NEP ranged from–137.79 to 461.96 g C/m^(2) in the Horqin Sandy Land,with 88.21%of the area showing a significant increasing trend.Among different land use types,forestland exhibited the highest NEP values,followed by cropland,grassland,impervious land,and unused land.The NEP in carbon sink areas was primarily regulated by potential evapotranspiration(negatively correlated)and precipitation(positively correlated).Slope was identified as the most significant positive determinant in carbon source areas.Forestland exhibited climate–topography interactions driving NEP,whereas cropland and grassland relied on temperature;unused land and impervious land were susceptible to land use/cover change and human footprint.This study has significant implications for maintaining the carbon sink function and promoting ecological engineering programs that aim to enhance the capacity of terrestrial carbon sinks in the semi-arid agro-pastoral ecotone.展开更多
Aims Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions.However,temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because so...Aims Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions.However,temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because soil water condition also plays an important role in mediating phenology.Methods We used growing degree day(GDD)model and growing season index(GSI)model,coupling minimum temperature(T_(min))with soil moisture(SM)to explore the influence of heat requirement and hydroclimatic interaction on the start of carbon uptake period(SCUP)and net ecosystem productivity(NEP)in two alpine meadows with different precipitation regimes on the Qinghai-Tibet Plateau(QTP).One is the water-limited alpine steppe-meadow,and the other is the temperature-limited alpine shrub-meadow.Important Findings We observed two clear patterns linking GDD and GSI to SCUP:SCUP was similarly sensitive to variations in preseason GDD and GSI in the humid alpine shrub-meadow,while SCUP was more sensitive to the variability in preseason GSI than GDD in the semiarid alpine steppe-meadow.The divergent patterns indicated a balance of the limiting climatic factors between temperature and water availability.In the humid meadow,higher temperature sensitivity of SCUP could maximize thermal benefit without drought stress,as evidenced by the stronger linear correlation coefficient(R2)and Akaike’s information criterion(AIC)between observed SCUPs and those of simulated by GDD model.However,greater water sensitivity of SCUP could maximize the benefit of water in semiarid steppe-meadow,which is indicated by the stronger R2 and AIC between observed SCUPs and those of simulated by GSI model.Additionally,although SCUPs were determined by GDD in the alpine shrub-meadow ecosystem,NEP was both controlled by accumulative GSI in two alpine meadows.Our study highlights the impacts of hydroclimatic interaction on spring carbon flux phenology and vegetation productivity in the humid and semiarid alpine ecosystems.The results also suggest that water,together with temperature should be included in the models of phenology and carbon budget for alpine ecosystems in semiarid regions.These fi ndings have important implications for improving vegetation phenology models,thus advancing our understanding of the interplay between vegetation phenology,productivity and climate change in future.展开更多
Farmland ecosystems are the primary ecosystem type in inland river basins,providing the biological and material basis for human development and survival.The foundation for monetizing the value of agricultural ecologic...Farmland ecosystems are the primary ecosystem type in inland river basins,providing the biological and material basis for human development and survival.The foundation for monetizing the value of agricultural ecological products and transforming green mountains into gold mountains is the precise assessment of ecosystem products in specific geographic units(VEP)within farmland ecosystems,which elucidates regional agricultural resource endowments and spatial distribution.However,agricultural ecological products face challenges in valuation,trading,and monetization,and research on pathways for their value transformation remains limited.This study uses Zhangye City in inland river basins as an example to construct a catalog of farmland ecosystem ecological products and explores VEP accounting methods based on multi-source data,including statistical,remote sensing,and monitoring data,at the city and county scales,and analyzes differentiated value transformation pathways according to the attributes of various agricultural ecological products.The results show that material supply value ranks highest among the VEP of farmland ecosystems in inland river basins,followed by regulatory services,while recreational agriculture value ranks lowest.The ranking of VEP varies from the ranking of farmland ecosystem area,with available agricultural water being a major constraint on the VEP of farmland ecosystems in inland river basins.Regional climate,geographic position,and transportation are linked to the value of agricultural ecosystem products within material supply products.Precipitation,soil structure,and cropping patterns are linked to the value of agricultural ecosystem products within regulatory services.The local cultural resources and tourism infrastructure are linked to the value of agricultural ecosystem products within cultural services.Regarding the pathways for achieving the value of agricultural ecological products,market-oriented strategies dominate the mainstay of material supply products,government-led mechanisms are pivotal for regulatory service products,and a combination of government and market strategies is essential for cultural service products.展开更多
A dynamic biogeochemical model was used to estimate the responses of China's terrestrial net primary productivity (NPP), soil heterotrophic respiration (HR) and net ecosystem productivity (NEP) to changes in clima...A dynamic biogeochemical model was used to estimate the responses of China's terrestrial net primary productivity (NPP), soil heterotrophic respiration (HR) and net ecosystem productivity (NEP) to changes in climate and atmospheric CO2 from 1981 to 1998. Results show that China's total NPP varied between 2.89 and 3.37 Gt C/a and had an increasing trend by 0.32% per year, HR varied between 2.89 and 3.21 Gt C/a and grew by 0.40% per year, Annual NEP varied between -0.32 and 0.25 Gt C but had no statistically significant interannual trend. The positive mean NEP indicates that China's terrestrial ecosystems were taking up carbon with a total carbon sequestration of 1.22 Gt C during the analysis period. The terrestrial NEP in China related to climate and atmospheric CO2 increases accounted for about 10% of the world's total and was similar to the level of the United States in the same period. The mean annual NEP for the analysis period was near to zero for most of the regions in China, but significantly positive NEP occurred in Northeast China Plain, the southeastern Xizang (Tibet) and Huang-Huai-Hai Plain, and negative NEP occurred in the Da Hinggan Mountains, Xiao Hinggan Mountains, Loess Plateau and Yunnan-Guizhou Plateau. China's climate at the time was warm and dry relative to other periods, so the estimated NEP is probably lower than the average level. China's terrestrial NEP may increase if climate becomes wetter but is likely to continue to decrease if the present warming and drying trend sustains.展开更多
Grasslands and agro-ecosystems occupy one-third of the global terrestrial area. However, great uncertainty still exists about their contributions to the global carbon cycle. This study used various combinations of a s...Grasslands and agro-ecosystems occupy one-third of the global terrestrial area. However, great uncertainty still exists about their contributions to the global carbon cycle. This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors, specifically radiation, temperature, and moisture, on the ecosystem carbon exchange at two dissimilar study sites. Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases, we investigated the response char- acteristics of productivity of grasslands and croplands to different environmental factors, and analyzed the seasonal change patterns of different model parameters. Parameter estimations and uncertainty analyses were performed based on a Bayesian approach. Our results indicated that： （1） the net ecosystem exchange （NEE） of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns. On the whole, the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO2; （2） in the daytime, the mean NEE of the two ecosystems had the largest values in July and the lowest values in October. However, overall carbon uptake in the cropland was greater than in the alpine meadow from June to September; （3） at the alpine meadow site, temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season, while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region; （4） at the cropland site, both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and （5） some parameters had an obvious characteristic of seasonal patterns, while others had only small seasonal variations.展开更多
Based on the concept of“Lucid waters and lush mountains are invaluable assets”,Chinese government is relying on the ecological and environmental characteristics of cities,in combination with modern ecological,econom...Based on the concept of“Lucid waters and lush mountains are invaluable assets”,Chinese government is relying on the ecological and environmental characteristics of cities,in combination with modern ecological,economic,and sociological theories,to achieve sustainable urban development.However,the value realization of ecological products(EP)faces challenges in four major aspects:quantification,trading,transformation,and sustainability.At this stage,seeking breakthroughs to form a stable development path for the realization of the value of EPs is crucial.This paper examines the Guilin Sustainable Development Innovation Demonstration Zone and conducts a case study on oil tea,a characteristic EP.Based on the value realization of EPs,this paper analyzes the oil tea industry in terms of three functions:ecological protection,regional economic development,and traditional cultural support.Drawing on the theory of the gross ecosystem product,this paper examines the role of the value realization of oil tea in improving the quality of the urban living environment and ecosystem functions in Guilin.The results can help promote research on the shaping effects of endemic EPs on sustainable development with respect to the urban economy.Taking a human-centered perspective,the principles of landsenses ecology and traditional ecological knowledge can help analyze the social,historical,and cultural value of oil tea.Combined with on-site research data,a relationship map centered on oil tea culture is created to explore the importance of developing traditional cultural attributes of local EPs in promoting cultural customs,protecting the cultural diversity of ethnic minorities,and driving the development of the cultural tourism industry.By constructing a sustainable urban development model centered on developing local characteristic EPs with the core elements of ecology-economy-traditional culture,this paper aims to strengthen the ecological protection function of cities,promote high-quality economic development,and enhance the soft power of traditional culture.It provides scientific support for the sustainable development planning in Guilin.展开更多
Urbanization radically alters the climatic environment and landscape patterns of urban areas,but its impact on the carbon sequestration capacity of vegetation remains uncertain.Given the limitations of current small-s...Urbanization radically alters the climatic environment and landscape patterns of urban areas,but its impact on the carbon sequestration capacity of vegetation remains uncertain.Given the limitations of current small-scale ground-based in situ experiments,the response of vegetation carbon sequestration capacity to urbanization and the factors influencing it remain unclear at the global scale.Using multisource remote sensing data,we quanti-fied and differentiated the direct and indirect impacts of urbanization on the carbon sequestration capacity of vegetation in 508 large urban areas globally from 2000 to 2020.The results revealed that the direct impacts of urbanization were generally negative.However,446 cities experienced an indirect enhancement in vegetation carbon sequestration capacity during urbanization,averaging 19.6%globally and offsetting 14.7%of the di-rect loss due to urbanization.These positive indirect effects were most pronounced in environments with limited hydrothermal conditions and increased most in densely populated temperate and cold regions.Furthermore,indi-rect impacts were closely related to urbanization intensity,human footprint,and level of urban development.Our study enhances the understanding of how the carbon sequestration capacity of vegetation dynamically responds to changes in the urban environment,which is crucial for improving future urban vegetation management and building sustainable cities.展开更多
The preliminary results of long-term CO_(2)flux measurements at forest sites in East Asia are explained and compared with each other.The features of seasonal variation of CO_(2)fluxes are different among deciduous-bro...The preliminary results of long-term CO_(2)flux measurements at forest sites in East Asia are explained and compared with each other.The features of seasonal variation of CO_(2)fluxes are different among deciduous-broadleaf,evergreen-coniferous,deciduous-coniferous and tropical forests in East Asia,and the causes of difference are discussed.The integrated yearly NEP(net ecosystem production)estimated from the CO_(2)flux by eddy covariance method in various forests of East Asia has a notable difference in the range of 2 to 8 tC ha^(-1)yr^(-1).The main factors of this difference are the annual mean temperature and tree species.Furthermore,the remaining issues are discussed,such as the quantitative estimation of the CO_(2)flux by the eddy covariance method and the synthetic analysis of the carbon budget under collaborations with biological survey.展开更多
Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity （NPP） of terrestrial ecosystems is important for carbon cycle ...Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity （NPP） of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen （N） cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator （BEPS） model. With the established database （leaf area index, land cover, daily meteorology data, vegetation and soil） at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g？m-2？a-1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model （without considering nitrogen effect）, it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.展开更多
Wetland ecosystems are crucial to the global carbon cycle.In this study,the Zhalong Wetland was investigated.Based on remote sensing and meteorological observation data from 1975-2018 and the downscaled fifth phase of...Wetland ecosystems are crucial to the global carbon cycle.In this study,the Zhalong Wetland was investigated.Based on remote sensing and meteorological observation data from 1975-2018 and the downscaled fifth phase of the coupled model intercomparison project(CMIP5)climate projection dataset from 1961-2100,the parameters of a net primary productivity(NPP)climatic potential productivity model were adjusted,and the simulation ability of the CMIP5 coupled models was evaluated.On this basis,we analysed the spatial and temporal variations of land cover types and landscape transformation processes in the Zhalong Nature Reserve over the past 44 years.We also evaluated the influence of climate change on the NPP of the vegetation,microbial heterotrophic respiration(Rh),and net ecosystem productivity(NEP)of the Zhalong Wetland and predicted the carbon sequestration potential of the Zhalong Wetland from 2019-2029 under the representative concentration pathways(RCP)4.5 and RCP 8.5 scenarios.Our results indicate the following:(1)Herbaceous bog was the primary land cover type of the Zhalong Nature Reserve,occupying an average area of 1168.02±224.05 km^(2),equivalent to 51.84% of the total reserve area.(2)Since 1975,the Zhalong Nature Reserve has undergone a dry-wet-dry transformation process.Excluding several wet periods during the mid-1980s to early 1990s,the reserve has remained a dry habitat,with particularly severe conditions from 2000 onwards.(3)The 1975-2018 mean NPP,Rh,and NEP values of the Zhalong Wetland were 500.21±52.76,337.59±10.80,and 162.62±45.56 gC·m^(2)·a^(-1),respectively,and an evaluation of the carbon balance indicated that the reserve served as a carbon sink.(4)From 1975-2018,NPP showed a significant linear increase,Rh showed a highly significant linear increase,while the increase in the carbon absorption rate was smaller than the increase in the carbon release rate.(5)Variations in NPP and NEP were precipitation-driven,with the correlations of NPP and NEP with annual precipitation and summer precipitation being highly significantly positive(P<0.001);variations in Rh were temperature-driven,with the correlations of Rh with the average annual,summer,and autumn temperatures being highly significantly positive(P<0.001).The interaction of precipitation and temperature enhances the impact on NPP,Rh and NEP.(6)Under the RCP 4.5 and RCP 8.5 scenarios,the predicted carbon sequestration by the Zhalong Wetland from 2019-2029 was 2.421(±0.225)× 10^(11) gC·a^(-1) and 2.407(±0.382)× 10^(11)gC·a^(-1),respectively,which were both lower than the mean carbon sequestration during the last 44 years(2.467(±0.950)× 10^(11) gC·a^(-1)).Future climate change may negatively contribute to the carbon sequestration potential of the Zhalong Wetland.The results of the present study are significant for enhancing the abilities of integrated eco-meteorological moni-toring,evaluation,and early warning systems for wetlands.展开更多
Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) ar...Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) are being tested to limit forest losses, but the quantitative impact on forest carbon (C) dynamics is still unclear. In this study, we designed 19 separate scenarios of no intervention or varying success of EIS, FP, and their combination on SBW caused defoliation and mortality. We then used the TRIPLEX-Insect model to quantify their effects on forest C dynamics in the forests of the four provinces of Atlantic Canada. A scenario applying FP to 10%of the area with the greatest potential C losses of living biomass, protecting foliage in 10%of the forests is more realistic than higher proportion of FP given the high cost and large areas involved, resulted in reducing average cumulative net ecosystem productivity (NEP) from 2020 to 2039 by 56%–127%compared to a no outbreak scenario.Our results showed that FP would have to be applied everywhere to reduce tree mortality and increase NEP more than 8 years of successful EIS applied. However, if EIS can be successfully implemented for 12 years, it will maintain more forest C than FP applied everywhere during a moderate outbreak. We also found that the combination of EIS followed by FP in 10%of the areas disturbed by the SBW could maintain average cumulative NEP at similar levels to no defoliation in every province of Atlantic Canada. Black/red spruce forests younger than 60years old underwent the smallest changes in C dynamics whether using EIS, FP, or both. This highlights the importance of forest species, forest age, and their interactions on the effectiveness of a treatment during SBW outbreak. Overall, 31%–76%of the study area in Atlantic Canada could convert from a C sink to a source by 2039,if no protective measures are used under the worst-case scenarios, thus contributing to future climate warming.展开更多
Estuarial saline wetlands have been recognized as a vital role in CO_2 cycling.However,insufficient attention has been paid to estimating CO_2 fluxes from estuarial saline wetlands.In this study,the static chamber-gas...Estuarial saline wetlands have been recognized as a vital role in CO_2 cycling.However,insufficient attention has been paid to estimating CO_2 fluxes from estuarial saline wetlands.In this study,the static chamber-gas chromatography(GC) method was used to quantify CO_2 budget of an estuarial saline reed(Phragmites australis) wetland in Jiaozhou Bay in Qingdao City of Shandong Province,China during the reed growing season(May to October) in 2014.The CO_2 budget study involved net ecosystem CO_2 exchange(NEE),ecosystem respiration(Reco) and gross primary production(GPP).Temporal variation in CO_2 budget and the impact of air/soil temperature,illumination intensity and aboveground biomass exerted on CO_2 budget were analyzed.Results indicated that the wetland was acting as a net sink of 1129.16 g/m^2 during the entire growing season.Moreover,the values of Reco and GPP were 1744.89 g/m^2 and 2874.05 g/m^2,respectively;the ratio of Reco and GPP was 0.61.Diurnal and monthly patterns of CO_2 budget varied significantly during the study period.Reco showed exponential relationships with air temperature and soil temperature at 5 cm,10 cm,20 cm depths,and soil temperature at 5 cm depth was the most crucial influence factor among them.Meanwhile,temperature sensitivity(Q10) of Reco was negatively correlated with soil temperature.Light and temperature exerted strong controls over NEE and GPP.Aboveground biomass over the whole growing season showed non-linear relationships with CO_2 budget,while those during the early and peak growing season showed significant linear relationships with CO_2 budget.This research provides valuable reference for CO_2 exchange in estuarial saline wetland ecosystem.展开更多
Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in ...Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in the global carbon cycle. Although many previous studies have examined tundra carbon dioxide fluxes, few have concentrated on elevated terrain(hills and ridge tops) that is exposed to harsh environmental conditions resulting in sparse vegetation cover and seemingly low productivity. In this study we measured carbon dioxide(CO2) exchange of four common tundra communities on the crest of an esker located in the central Canadian low-Arctic. The objectives were to quantify and compare CO2 fluxes from these communities, investigate responses to environmental variables and qualitatively compare fluxes with those from similar communities growing in less harsh lowland tundra environments. Measurements made during July and August 2010 show there was little difference in net ecosystem exchange(NEE) and gross ecosystem production(GEP) among the three deciduous shrub communities, Arctous alpina, Betula glandulosa and Vaccinium uliginosum, with means ranging from -4.09 to -6.57 μmol·m^-2·s^-1 and -7.92 to -9.24 μmol·m^-2·s^-1, respectively. Empetrum nigrum communities had significantly smaller mean NEE and GEP(-1.74 and -4.08 μmol·m^-2·s^-1, respectively). Ecosystem respiration(ER) was similar for all communities(2.56 to 3.03 μmol·m^-2·s^-1), except the B. glandulosa community which had a larger mean flux(4.66 μmol·m^-2·s^-1). Overall, fluxes for these esker-top communities were near the upper range of fluxes reported for other tundra communities. ER was related to soil temperature in all of the communities. Only B. glandulosa GEP and ER showed sensitivity to a persistent decline in soil moisture throughout the study. These findings may have important implications for how esker tops would be treated in construction of regional carbon budgets and for predicting the impacts of climate change on Arctic tundra future carbon budgets.展开更多
This study develops geospatial analysis of terrestrial carbon exchange for the conterminous United State and estimates large-scale NEP （net ecosystem production） dynamic from 2008 to 2013. We apply land-use and land...This study develops geospatial analysis of terrestrial carbon exchange for the conterminous United State and estimates large-scale NEP （net ecosystem production） dynamic from 2008 to 2013. We apply land-use and land-cover data in order to coherently include cropland, forest, wetland and other ecologically active landscapes in the mapping. Our results show a distribution of high harvest carbon release in the Corn Belt states, in addition to hot spots around the US in areas like Southern California and Arizona. Harvest carbon is low in areas in the southern United States, and central/southern Appalachian Mountains. We identify NEP changes for coupled agricultural, forest and other high-carbon-uptake ecosystems systems, conversions to and from crop, and land in frequent conversion among forest, wetland, pasture and rangeland. Findings from this study will provide important information to support and promote the co-production of science and decision-making.展开更多
Background:Global warming impacts ecosystem carbon exchange,thus altering the carbon sink capacity of terrestrial ecosystems.However,the response of ecosystem carbon fluxes to whole-soil-profile warming remains unclea...Background:Global warming impacts ecosystem carbon exchange,thus altering the carbon sink capacity of terrestrial ecosystems.However,the response of ecosystem carbon fluxes to whole-soil-profile warming remains unclear.Methods:We first investigated the effect of whole-soil warming on ecosystem carbon fluxes in an alpine grassland ecosystem on the Qinghai-Tibet Plateau.We also compiled a database of 48 articles to examine the general patterns of experimental warming effects on these fluxes using a global meta-analysis.Results:Our results showed that whole-soil warming elevated gross ecosystem productivity(GEP)by 14%and ecosystem respiration(ER)by 11%,but had a minor impact on net ecosystem carbon exchange(NEE)in the alpine grassland.In the meta-analysis,warming also enhanced GEP(10%-11%)and ER(13%),but did not alter NEE.Warming-induced shifts in plant community and extension of growing season may be the main reasons for the higher GEP and ER under warming,and the offset of both fluxes likely caused the minor response of NEE to warming.Conclusions:More attention should be paid to the long-term response of ecosystem carbon fluxes to whole-soil or whole-ecosystem warming throughout the year.These novel findings may help us better predict and mitigate future climate-carbon feedback under realistic warming scenarios.展开更多
Many studies on global climate have forecast major changes in the amounts and spatial patterns of precipitation that may significantly affect temperate grasslands in arid and semi-arid regions.As a part of ChinaFLUX,e...Many studies on global climate have forecast major changes in the amounts and spatial patterns of precipitation that may significantly affect temperate grasslands in arid and semi-arid regions.As a part of ChinaFLUX,eddy covariance flux measurements were made at a semi-arid Leymus chinensis steppe in Inner Mongolia,China during 2003-2004 to quantify the response of carbon exchange to environmental changes.Results showed that gross ecosystem production(FGEP)and ecosystem respiration(Reco)of the steppe were significantly depressed by water stress due to lack of precipitation during the growing season.Temperature was the dominant factor affecting FGEP and Reco in 2003,whereas soil moisture imposed a significant influence on both Reco and FGEP in 2004.Under wet conditions,Reco showed an exponentially increasing trend with temperature(Q10=2.0),but an apparent reduction in the value of Reco and its temperature sensitivity were observed during the periods of water stress(Q10=1.6).Both heat and water stress can cause decrease in FGEP.The sea-sonality of ecosystem carbon exchange was strongly correlated with the variation of precipitation.With less precipitation in 2003,the steppe sequestrated carbon in June and July,and went into a senescence in early August due to water stress.As compared to 2003,the severe drought during the spring of 2004 delayed the growth of the steppe until late June,and the steppe became a CO_(2)sink from early July until mid-September,with ample precipitation in August.The semi-arid steppe released a total of 9.7 g C·m-2 from May 16 to the end of September 2003,whereas the net carbon budget during the same period in 2004 was close to zero.Long-term measurements over various grasslands are needed to quantify carbon balance in temperate grasslands.展开更多
Aims Recent studies have recognized the alpine grasslands on the Qinghai-Tibetan plateau as a significant sink for atmospheric CO_(2).The carbon-sink strength may differ among grassland ecosystems at various altitudes...Aims Recent studies have recognized the alpine grasslands on the Qinghai-Tibetan plateau as a significant sink for atmospheric CO_(2).The carbon-sink strength may differ among grassland ecosystems at various altitudes because of contrasting biotic and physical environments.This study aims(i)to clarify the altitudinal pattern of ecosystem CO_(2) fluxes,including gross primary production(GPP),daytime ecosystem respiration(Redaytime)and net ecosystem production(NEP),during the period with peak above-ground biomass;and(ii)to elucidate the effects of biotic and abiotic factors on the altitudinal variation of ecosystem CO_(2) fluxes.Methods Ecosystem CO_(2) fluxes and abiotic and biotic environmental factors were measured in an alpine grassland at four altitudes from 3600 to 4200 m along a slope of the Qilian Mountains on the northwestern Qinghai-Tibetan Plateau during the growing season of 2007.We used a closed-chamber method combined with shade screens and an opaque cloth to measure several carbon fluxes,GPP,Redaytime and NEP,and factors,light-response curve for GPP and temperature sensitivity of Redaytime.Above-and below-ground biomasses and soil C and N contents at each measurement point were also measured.Important Findings(i)Altitudinal pattern of ecosystem CO_(2) fluxes:The maximum net ecosystem CO_(2) flux(NEPmax),i.e.the potential ecosystem CO_(2) sink strength,was markedly different among the four altitudes.NEPmax was higher at the highest and lowest sites,ap proximately7.460.9 and6.760.6 lmol CO_(2) m^(-2)s^(-1)(mean 6 standard error),respectively,but smaller at the intermediate altitude sites(3800 and 4000 m).The altitudinal pattern of maximum gross primary production was similar to that of NEPmax.The Redaytime,however,was significantly higher at the lowest altitude(3.460.3 lmol CO_(2) m^(-2)s^(-1))than at the other three altitudes.(ii)Altitudinal variation of vegetation biomass:The aboveground biomass was higher at the highest altitude(154627 g DW m2)than at the other altitudes,which we attribute mainly to the large biomass in cushion plants at the highest altitude.The small above-ground biomass at the lower altitudes was probably due to heavy grazing during the growing season.(iii)Features of ecosystem CO_(2) fluxes:Redaytime and GPP were positively correlated with above-ground biomass.The low ratio of Redaytime to GPP at either the measurement point or the site level suggests that CO_(2) uptake efficiency tends to be higher at higher altitudes,which indicates a high potential sink strength for atmospheric CO_(2) despite the low temperature at high altitudes.The results suggest that the effect of grazing intensity on ecosystem carbon dynamics,partly by decreasing vegetation biomass,should be clarified further.展开更多
Gross ecosystem product(GEP) is the gross value of all ecosystem products and services provided by ecosystems for human society. In practice, GEP measures the ecosystems’ contributions to human well-being and constit...Gross ecosystem product(GEP) is the gross value of all ecosystem products and services provided by ecosystems for human society. In practice, GEP measures the ecosystems’ contributions to human well-being and constitutes one of the core issues in the construction of ecological civilization systems. Currently, GEP accounting faces a series of problems, such as the inconsistency of accounting subjects and a lack of accounting standards,the result of which is the non-reproducibility and weak applicability of accounting results. In this paper, mainstream models for ecosystem service valuation are summarized in a systematic manner. On this basis, eight basic principles are established for screening accounting indicators: biological productivity, human benefits, production territoriality, current increment, actual effectiveness, physical metrizability, data availability, and harmlessness. Next, a series of ecosystem service subjects are identified that need to be excluded from accounting, and the detailed reasons for their exclusion are presented. Finally, three ideas for improving GEP accounting are offered from the perspectives of the relationship between biological production and human production, the circulation-transport relationship and spatial differences, and harms to the ecosystem carrying capacity. The purpose is to provide positive considerations aimed at promoting the socio-economic applications of accounting and to contribute to the scientific quantification of the values of ecological products.展开更多
Aims Recent studies have shown that alpine meadows on the Qinghai-Tibetan plateau act as significant CO_(2)sinks.On the plateau,alpine shrub meadow is one of typical grassland ecosystems.The major alpine shrub on the ...Aims Recent studies have shown that alpine meadows on the Qinghai-Tibetan plateau act as significant CO_(2)sinks.On the plateau,alpine shrub meadow is one of typical grassland ecosystems.The major alpine shrub on the plateau is Potentilla fruticosa L.(Rosaceae),which is distributed widely from 3200 to 4000 m.Shrub species play an important role on carbon sequestration in grassland ecosystems.In addition,alpine shrubs are sensitive to climate change such as global warming.Considering global warming,the biomass and productivity of P.fruticosa will increase on Qinghai-Tibetan Plateau.Thus,understanding the carbon dynamics in alpine shrub meadow and the role of shrubs around the upper distribution limit at present is essential to predict the change in carbon sequestration on the plateau.However,the role of shrubs on the carbon dynamics in alpine shrub meadow remains unclear.The objectives of the present study were to evaluate the magnitude of CO_(2)exchange of P.fruticosa shrub patches around the upper distribution limit and to elucidate the role of P.fruticosa on ecosystem CO_(2)fluxes in an alpine meadow.Methods We used the static acrylic chamber technique to measure and estimate the net ecosystem productivity(NEP),ecosystem respiration(Re),and gross primary productivity(GPP)of P.fruticosa shrub patches at three elevations around the species’upper distribution limit.Ecosystem CO_(2)fluxes and environmental factors were measured from 17 to 20 July 2008 at 3400,3600,and 3800 m a.s.l.We examined the maximum GPP at infinite light(GPPmax)and maximum Re(Remax)during the experimental time at each elevation in relation to aboveground biomass and environmental factors,including air and soil temperature,and soil water content.Important Findings Patches of P.fruticosa around the species’upper distribution limit absorbed CO_(2),at least during the daytime.Maximum NEP at infinite light(NEPmax)and GPPmax of shrub patches in the alpine meadow varied among the three elevations,with the highest values at 3400 m and the lowest at 3800 m.GPPmax was positively correlated with the green biomass of P.fruticosa more strongly than with total green biomass,suggesting that P.fruticosa is the major contributor to CO_(2)uptake in the alpine shrub meadow.Air temperature influenced the potential GPPat the shrub-patch scale.Remax was correlated with aboveground biomass and Remax normalized by aboveground biomass was influenced by soil water content.Potentilla fruticosa height(biomass)and frequency increased clearly as elevation decreased,which promotes the large-scale spatial variation of carbon uptake and the strength of the carbon sink at lower elevations.展开更多
基金funded by the National Major Science and Technology Program for Water Pollution Control and Treatment(2017ZX07101-002)the Discipline Construction Program of ZHANG Huayong,Distinguished Professor of School of Life Sciences,Shandong University(61200082363001).
文摘Vegetation in terrestrial ecosystems as a carbon sink is a crucial factor in mitigating global warming and reaching carbon neutrality targets,although the drivers of net ecosystem productivity(NEP)under combined human and environmental pressures remain poorly understood.In this study,we analyzed the spatiotemporal evolution of NEP in the Horqin Sandy Land,China from 2000 to 2020,and observed the variation in NEP across different land use types.We further identified and quantified the effects of human activities,topographical features,climatic conditions,and soil properties on NEP through the application of structural equation modeling(SEM)and boosted regression trees(BRT).The results showed that the multi-year average NEP ranged from–137.79 to 461.96 g C/m^(2) in the Horqin Sandy Land,with 88.21%of the area showing a significant increasing trend.Among different land use types,forestland exhibited the highest NEP values,followed by cropland,grassland,impervious land,and unused land.The NEP in carbon sink areas was primarily regulated by potential evapotranspiration(negatively correlated)and precipitation(positively correlated).Slope was identified as the most significant positive determinant in carbon source areas.Forestland exhibited climate–topography interactions driving NEP,whereas cropland and grassland relied on temperature;unused land and impervious land were susceptible to land use/cover change and human footprint.This study has significant implications for maintaining the carbon sink function and promoting ecological engineering programs that aim to enhance the capacity of terrestrial carbon sinks in the semi-arid agro-pastoral ecotone.
基金supported by the National Natural Science Foundation of China(31870406,41661144045)the State Key Research and Development Program(2016YFC0502001,2017YFA0604801).
文摘Aims Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions.However,temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because soil water condition also plays an important role in mediating phenology.Methods We used growing degree day(GDD)model and growing season index(GSI)model,coupling minimum temperature(T_(min))with soil moisture(SM)to explore the influence of heat requirement and hydroclimatic interaction on the start of carbon uptake period(SCUP)and net ecosystem productivity(NEP)in two alpine meadows with different precipitation regimes on the Qinghai-Tibet Plateau(QTP).One is the water-limited alpine steppe-meadow,and the other is the temperature-limited alpine shrub-meadow.Important Findings We observed two clear patterns linking GDD and GSI to SCUP:SCUP was similarly sensitive to variations in preseason GDD and GSI in the humid alpine shrub-meadow,while SCUP was more sensitive to the variability in preseason GSI than GDD in the semiarid alpine steppe-meadow.The divergent patterns indicated a balance of the limiting climatic factors between temperature and water availability.In the humid meadow,higher temperature sensitivity of SCUP could maximize thermal benefit without drought stress,as evidenced by the stronger linear correlation coefficient(R2)and Akaike’s information criterion(AIC)between observed SCUPs and those of simulated by GDD model.However,greater water sensitivity of SCUP could maximize the benefit of water in semiarid steppe-meadow,which is indicated by the stronger R2 and AIC between observed SCUPs and those of simulated by GSI model.Additionally,although SCUPs were determined by GDD in the alpine shrub-meadow ecosystem,NEP was both controlled by accumulative GSI in two alpine meadows.Our study highlights the impacts of hydroclimatic interaction on spring carbon flux phenology and vegetation productivity in the humid and semiarid alpine ecosystems.The results also suggest that water,together with temperature should be included in the models of phenology and carbon budget for alpine ecosystems in semiarid regions.These fi ndings have important implications for improving vegetation phenology models,thus advancing our understanding of the interplay between vegetation phenology,productivity and climate change in future.
基金supported by Humanities and Social Sciences research project of Ministry of Education(Grant No.24YJCZH342)the Inventory of ecological products and calculation of Gross ecosystem product(GEP)in Zhangye City(Grant No.E4390901)。
文摘Farmland ecosystems are the primary ecosystem type in inland river basins,providing the biological and material basis for human development and survival.The foundation for monetizing the value of agricultural ecological products and transforming green mountains into gold mountains is the precise assessment of ecosystem products in specific geographic units(VEP)within farmland ecosystems,which elucidates regional agricultural resource endowments and spatial distribution.However,agricultural ecological products face challenges in valuation,trading,and monetization,and research on pathways for their value transformation remains limited.This study uses Zhangye City in inland river basins as an example to construct a catalog of farmland ecosystem ecological products and explores VEP accounting methods based on multi-source data,including statistical,remote sensing,and monitoring data,at the city and county scales,and analyzes differentiated value transformation pathways according to the attributes of various agricultural ecological products.The results show that material supply value ranks highest among the VEP of farmland ecosystems in inland river basins,followed by regulatory services,while recreational agriculture value ranks lowest.The ranking of VEP varies from the ranking of farmland ecosystem area,with available agricultural water being a major constraint on the VEP of farmland ecosystems in inland river basins.Regional climate,geographic position,and transportation are linked to the value of agricultural ecosystem products within material supply products.Precipitation,soil structure,and cropping patterns are linked to the value of agricultural ecosystem products within regulatory services.The local cultural resources and tourism infrastructure are linked to the value of agricultural ecosystem products within cultural services.Regarding the pathways for achieving the value of agricultural ecological products,market-oriented strategies dominate the mainstay of material supply products,government-led mechanisms are pivotal for regulatory service products,and a combination of government and market strategies is essential for cultural service products.
文摘A dynamic biogeochemical model was used to estimate the responses of China's terrestrial net primary productivity (NPP), soil heterotrophic respiration (HR) and net ecosystem productivity (NEP) to changes in climate and atmospheric CO2 from 1981 to 1998. Results show that China's total NPP varied between 2.89 and 3.37 Gt C/a and had an increasing trend by 0.32% per year, HR varied between 2.89 and 3.21 Gt C/a and grew by 0.40% per year, Annual NEP varied between -0.32 and 0.25 Gt C but had no statistically significant interannual trend. The positive mean NEP indicates that China's terrestrial ecosystems were taking up carbon with a total carbon sequestration of 1.22 Gt C during the analysis period. The terrestrial NEP in China related to climate and atmospheric CO2 increases accounted for about 10% of the world's total and was similar to the level of the United States in the same period. The mean annual NEP for the analysis period was near to zero for most of the regions in China, but significantly positive NEP occurred in Northeast China Plain, the southeastern Xizang (Tibet) and Huang-Huai-Hai Plain, and negative NEP occurred in the Da Hinggan Mountains, Xiao Hinggan Mountains, Loess Plateau and Yunnan-Guizhou Plateau. China's climate at the time was warm and dry relative to other periods, so the estimated NEP is probably lower than the average level. China's terrestrial NEP may increase if climate becomes wetter but is likely to continue to decrease if the present warming and drying trend sustains.
基金funded by the National Natural Science Foundation of China(Nos.41401412,91125004)the Foundation for Excellent Youth Scholars of CAREERI,CAS(No.51Y451271)the Open Fund of the Key Laboratory of Desert and Desertification,CAS(No.KLDD-2014-007)
文摘Grasslands and agro-ecosystems occupy one-third of the global terrestrial area. However, great uncertainty still exists about their contributions to the global carbon cycle. This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors, specifically radiation, temperature, and moisture, on the ecosystem carbon exchange at two dissimilar study sites. Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases, we investigated the response char- acteristics of productivity of grasslands and croplands to different environmental factors, and analyzed the seasonal change patterns of different model parameters. Parameter estimations and uncertainty analyses were performed based on a Bayesian approach. Our results indicated that： （1） the net ecosystem exchange （NEE） of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns. On the whole, the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO2; （2） in the daytime, the mean NEE of the two ecosystems had the largest values in July and the lowest values in October. However, overall carbon uptake in the cropland was greater than in the alpine meadow from June to September; （3） at the alpine meadow site, temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season, while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region; （4） at the cropland site, both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and （5） some parameters had an obvious characteristic of seasonal patterns, while others had only small seasonal variations.
基金supported by the National Key Research and Development Program of China“Research on urban sustainable development evaluation data fusion management technology”[Grant No.2022YFC3802903]the Strategic Priority Research Program of the Chinese Academy of Sciences[Grant No.XDA23030403].
文摘Based on the concept of“Lucid waters and lush mountains are invaluable assets”,Chinese government is relying on the ecological and environmental characteristics of cities,in combination with modern ecological,economic,and sociological theories,to achieve sustainable urban development.However,the value realization of ecological products(EP)faces challenges in four major aspects:quantification,trading,transformation,and sustainability.At this stage,seeking breakthroughs to form a stable development path for the realization of the value of EPs is crucial.This paper examines the Guilin Sustainable Development Innovation Demonstration Zone and conducts a case study on oil tea,a characteristic EP.Based on the value realization of EPs,this paper analyzes the oil tea industry in terms of three functions:ecological protection,regional economic development,and traditional cultural support.Drawing on the theory of the gross ecosystem product,this paper examines the role of the value realization of oil tea in improving the quality of the urban living environment and ecosystem functions in Guilin.The results can help promote research on the shaping effects of endemic EPs on sustainable development with respect to the urban economy.Taking a human-centered perspective,the principles of landsenses ecology and traditional ecological knowledge can help analyze the social,historical,and cultural value of oil tea.Combined with on-site research data,a relationship map centered on oil tea culture is created to explore the importance of developing traditional cultural attributes of local EPs in promoting cultural customs,protecting the cultural diversity of ethnic minorities,and driving the development of the cultural tourism industry.By constructing a sustainable urban development model centered on developing local characteristic EPs with the core elements of ecology-economy-traditional culture,this paper aims to strengthen the ecological protection function of cities,promote high-quality economic development,and enhance the soft power of traditional culture.It provides scientific support for the sustainable development planning in Guilin.
基金supported by the National Natural Science Foun-dation of China(Grants No.42471118 and 52078440)the Youth Innovation Promotion Association of CAS(Grant No.2021194).
文摘Urbanization radically alters the climatic environment and landscape patterns of urban areas,but its impact on the carbon sequestration capacity of vegetation remains uncertain.Given the limitations of current small-scale ground-based in situ experiments,the response of vegetation carbon sequestration capacity to urbanization and the factors influencing it remain unclear at the global scale.Using multisource remote sensing data,we quanti-fied and differentiated the direct and indirect impacts of urbanization on the carbon sequestration capacity of vegetation in 508 large urban areas globally from 2000 to 2020.The results revealed that the direct impacts of urbanization were generally negative.However,446 cities experienced an indirect enhancement in vegetation carbon sequestration capacity during urbanization,averaging 19.6%globally and offsetting 14.7%of the di-rect loss due to urbanization.These positive indirect effects were most pronounced in environments with limited hydrothermal conditions and increased most in densely populated temperate and cold regions.Furthermore,indi-rect impacts were closely related to urbanization intensity,human footprint,and level of urban development.Our study enhances the understanding of how the carbon sequestration capacity of vegetation dynamically responds to changes in the urban environment,which is crucial for improving future urban vegetation management and building sustainable cities.
基金Global Environment Research Fund of the Ministry of the Environment,Japan AsiaFLUXChinaFLUX
文摘The preliminary results of long-term CO_(2)flux measurements at forest sites in East Asia are explained and compared with each other.The features of seasonal variation of CO_(2)fluxes are different among deciduous-broadleaf,evergreen-coniferous,deciduous-coniferous and tropical forests in East Asia,and the causes of difference are discussed.The integrated yearly NEP(net ecosystem production)estimated from the CO_(2)flux by eddy covariance method in various forests of East Asia has a notable difference in the range of 2 to 8 tC ha^(-1)yr^(-1).The main factors of this difference are the annual mean temperature and tree species.Furthermore,the remaining issues are discussed,such as the quantitative estimation of the CO_(2)flux by the eddy covariance method and the synthetic analysis of the carbon budget under collaborations with biological survey.
基金supported by the National Natu-ral Science Foundation of China (No.40771172 No. 40901223)+1 种基金the Innovative Program of the Chinese Academy of Sciences (No. kzcx2-yw-308)the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS (SKLLQG0821)
文摘Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity （NPP） of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen （N） cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator （BEPS） model. With the established database （leaf area index, land cover, daily meteorology data, vegetation and soil） at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g？m-2？a-1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model （without considering nitrogen effect）, it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.
基金Science Foundation of Heilongjiang Province(General Program),No.D2018006National Natural Science Foundation of China,No.41665007,No.41165005CMA/Northeast China Innovation and Open Laboratory of Eco-meteorology,No.stqx2017zd01,No.stqx2018zd03。
文摘Wetland ecosystems are crucial to the global carbon cycle.In this study,the Zhalong Wetland was investigated.Based on remote sensing and meteorological observation data from 1975-2018 and the downscaled fifth phase of the coupled model intercomparison project(CMIP5)climate projection dataset from 1961-2100,the parameters of a net primary productivity(NPP)climatic potential productivity model were adjusted,and the simulation ability of the CMIP5 coupled models was evaluated.On this basis,we analysed the spatial and temporal variations of land cover types and landscape transformation processes in the Zhalong Nature Reserve over the past 44 years.We also evaluated the influence of climate change on the NPP of the vegetation,microbial heterotrophic respiration(Rh),and net ecosystem productivity(NEP)of the Zhalong Wetland and predicted the carbon sequestration potential of the Zhalong Wetland from 2019-2029 under the representative concentration pathways(RCP)4.5 and RCP 8.5 scenarios.Our results indicate the following:(1)Herbaceous bog was the primary land cover type of the Zhalong Nature Reserve,occupying an average area of 1168.02±224.05 km^(2),equivalent to 51.84% of the total reserve area.(2)Since 1975,the Zhalong Nature Reserve has undergone a dry-wet-dry transformation process.Excluding several wet periods during the mid-1980s to early 1990s,the reserve has remained a dry habitat,with particularly severe conditions from 2000 onwards.(3)The 1975-2018 mean NPP,Rh,and NEP values of the Zhalong Wetland were 500.21±52.76,337.59±10.80,and 162.62±45.56 gC·m^(2)·a^(-1),respectively,and an evaluation of the carbon balance indicated that the reserve served as a carbon sink.(4)From 1975-2018,NPP showed a significant linear increase,Rh showed a highly significant linear increase,while the increase in the carbon absorption rate was smaller than the increase in the carbon release rate.(5)Variations in NPP and NEP were precipitation-driven,with the correlations of NPP and NEP with annual precipitation and summer precipitation being highly significantly positive(P<0.001);variations in Rh were temperature-driven,with the correlations of Rh with the average annual,summer,and autumn temperatures being highly significantly positive(P<0.001).The interaction of precipitation and temperature enhances the impact on NPP,Rh and NEP.(6)Under the RCP 4.5 and RCP 8.5 scenarios,the predicted carbon sequestration by the Zhalong Wetland from 2019-2029 was 2.421(±0.225)× 10^(11) gC·a^(-1) and 2.407(±0.382)× 10^(11)gC·a^(-1),respectively,which were both lower than the mean carbon sequestration during the last 44 years(2.467(±0.950)× 10^(11) gC·a^(-1)).Future climate change may negatively contribute to the carbon sequestration potential of the Zhalong Wetland.The results of the present study are significant for enhancing the abilities of integrated eco-meteorological moni-toring,evaluation,and early warning systems for wetlands.
基金part of an Early Intervention Strategy research project funded by Natural Resources Canada and the Healthy Forest Partnershipfinanced by the Fonds de Recherche du Québec (FQRNT) programNatural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant
文摘Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) are being tested to limit forest losses, but the quantitative impact on forest carbon (C) dynamics is still unclear. In this study, we designed 19 separate scenarios of no intervention or varying success of EIS, FP, and their combination on SBW caused defoliation and mortality. We then used the TRIPLEX-Insect model to quantify their effects on forest C dynamics in the forests of the four provinces of Atlantic Canada. A scenario applying FP to 10%of the area with the greatest potential C losses of living biomass, protecting foliage in 10%of the forests is more realistic than higher proportion of FP given the high cost and large areas involved, resulted in reducing average cumulative net ecosystem productivity (NEP) from 2020 to 2039 by 56%–127%compared to a no outbreak scenario.Our results showed that FP would have to be applied everywhere to reduce tree mortality and increase NEP more than 8 years of successful EIS applied. However, if EIS can be successfully implemented for 12 years, it will maintain more forest C than FP applied everywhere during a moderate outbreak. We also found that the combination of EIS followed by FP in 10%of the areas disturbed by the SBW could maintain average cumulative NEP at similar levels to no defoliation in every province of Atlantic Canada. Black/red spruce forests younger than 60years old underwent the smallest changes in C dynamics whether using EIS, FP, or both. This highlights the importance of forest species, forest age, and their interactions on the effectiveness of a treatment during SBW outbreak. Overall, 31%–76%of the study area in Atlantic Canada could convert from a C sink to a source by 2039,if no protective measures are used under the worst-case scenarios, thus contributing to future climate warming.
基金Under the auspices of National Natural Science Foundation of China(No.41101080)Shandong Natural Science Foundation of China(No.ZR2014DQ028,ZR2015DM004)
文摘Estuarial saline wetlands have been recognized as a vital role in CO_2 cycling.However,insufficient attention has been paid to estimating CO_2 fluxes from estuarial saline wetlands.In this study,the static chamber-gas chromatography(GC) method was used to quantify CO_2 budget of an estuarial saline reed(Phragmites australis) wetland in Jiaozhou Bay in Qingdao City of Shandong Province,China during the reed growing season(May to October) in 2014.The CO_2 budget study involved net ecosystem CO_2 exchange(NEE),ecosystem respiration(Reco) and gross primary production(GPP).Temporal variation in CO_2 budget and the impact of air/soil temperature,illumination intensity and aboveground biomass exerted on CO_2 budget were analyzed.Results indicated that the wetland was acting as a net sink of 1129.16 g/m^2 during the entire growing season.Moreover,the values of Reco and GPP were 1744.89 g/m^2 and 2874.05 g/m^2,respectively;the ratio of Reco and GPP was 0.61.Diurnal and monthly patterns of CO_2 budget varied significantly during the study period.Reco showed exponential relationships with air temperature and soil temperature at 5 cm,10 cm,20 cm depths,and soil temperature at 5 cm depth was the most crucial influence factor among them.Meanwhile,temperature sensitivity(Q10) of Reco was negatively correlated with soil temperature.Light and temperature exerted strong controls over NEE and GPP.Aboveground biomass over the whole growing season showed non-linear relationships with CO_2 budget,while those during the early and peak growing season showed significant linear relationships with CO_2 budget.This research provides valuable reference for CO_2 exchange in estuarial saline wetland ecosystem.
基金Funding for this research to PML was from the Natural Science and Engineering Research Council of Canada(NSERC)ABC was supported through the Northern Scientific Training Programan NSERC Undergraduate Student Research Award。
文摘Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in the global carbon cycle. Although many previous studies have examined tundra carbon dioxide fluxes, few have concentrated on elevated terrain(hills and ridge tops) that is exposed to harsh environmental conditions resulting in sparse vegetation cover and seemingly low productivity. In this study we measured carbon dioxide(CO2) exchange of four common tundra communities on the crest of an esker located in the central Canadian low-Arctic. The objectives were to quantify and compare CO2 fluxes from these communities, investigate responses to environmental variables and qualitatively compare fluxes with those from similar communities growing in less harsh lowland tundra environments. Measurements made during July and August 2010 show there was little difference in net ecosystem exchange(NEE) and gross ecosystem production(GEP) among the three deciduous shrub communities, Arctous alpina, Betula glandulosa and Vaccinium uliginosum, with means ranging from -4.09 to -6.57 μmol·m^-2·s^-1 and -7.92 to -9.24 μmol·m^-2·s^-1, respectively. Empetrum nigrum communities had significantly smaller mean NEE and GEP(-1.74 and -4.08 μmol·m^-2·s^-1, respectively). Ecosystem respiration(ER) was similar for all communities(2.56 to 3.03 μmol·m^-2·s^-1), except the B. glandulosa community which had a larger mean flux(4.66 μmol·m^-2·s^-1). Overall, fluxes for these esker-top communities were near the upper range of fluxes reported for other tundra communities. ER was related to soil temperature in all of the communities. Only B. glandulosa GEP and ER showed sensitivity to a persistent decline in soil moisture throughout the study. These findings may have important implications for how esker tops would be treated in construction of regional carbon budgets and for predicting the impacts of climate change on Arctic tundra future carbon budgets.
文摘This study develops geospatial analysis of terrestrial carbon exchange for the conterminous United State and estimates large-scale NEP （net ecosystem production） dynamic from 2008 to 2013. We apply land-use and land-cover data in order to coherently include cropland, forest, wetland and other ecologically active landscapes in the mapping. Our results show a distribution of high harvest carbon release in the Corn Belt states, in addition to hot spots around the US in areas like Southern California and Arizona. Harvest carbon is low in areas in the southern United States, and central/southern Appalachian Mountains. We identify NEP changes for coupled agricultural, forest and other high-carbon-uptake ecosystems systems, conversions to and from crop, and land in frequent conversion among forest, wetland, pasture and rangeland. Findings from this study will provide important information to support and promote the co-production of science and decision-making.
基金National Key Research and Development Program of China,Grant/Award Number:2022YFF0801902National Natural Science Foundation of China,Grant/Award Numbers:32301426,32425038+1 种基金China Postdoctoral Science Foundation,Grant/Award Numbers:2022M720252,2024T170025Chinese Academy of Sciences(CAS)Interdisciplinary Innovation Team,Grant/Award Number:xbzg-zdsys-202203。
文摘Background:Global warming impacts ecosystem carbon exchange,thus altering the carbon sink capacity of terrestrial ecosystems.However,the response of ecosystem carbon fluxes to whole-soil-profile warming remains unclear.Methods:We first investigated the effect of whole-soil warming on ecosystem carbon fluxes in an alpine grassland ecosystem on the Qinghai-Tibet Plateau.We also compiled a database of 48 articles to examine the general patterns of experimental warming effects on these fluxes using a global meta-analysis.Results:Our results showed that whole-soil warming elevated gross ecosystem productivity(GEP)by 14%and ecosystem respiration(ER)by 11%,but had a minor impact on net ecosystem carbon exchange(NEE)in the alpine grassland.In the meta-analysis,warming also enhanced GEP(10%-11%)and ER(13%),but did not alter NEE.Warming-induced shifts in plant community and extension of growing season may be the main reasons for the higher GEP and ER under warming,and the offset of both fluxes likely caused the minor response of NEE to warming.Conclusions:More attention should be paid to the long-term response of ecosystem carbon fluxes to whole-soil or whole-ecosystem warming throughout the year.These novel findings may help us better predict and mitigate future climate-carbon feedback under realistic warming scenarios.
基金This study was supported by the Chi-nese Academy of Sciences and the Ministry of Science and Technology through grants KZCX1-SW-01 and 2002CB412500.
文摘Many studies on global climate have forecast major changes in the amounts and spatial patterns of precipitation that may significantly affect temperate grasslands in arid and semi-arid regions.As a part of ChinaFLUX,eddy covariance flux measurements were made at a semi-arid Leymus chinensis steppe in Inner Mongolia,China during 2003-2004 to quantify the response of carbon exchange to environmental changes.Results showed that gross ecosystem production(FGEP)and ecosystem respiration(Reco)of the steppe were significantly depressed by water stress due to lack of precipitation during the growing season.Temperature was the dominant factor affecting FGEP and Reco in 2003,whereas soil moisture imposed a significant influence on both Reco and FGEP in 2004.Under wet conditions,Reco showed an exponentially increasing trend with temperature(Q10=2.0),but an apparent reduction in the value of Reco and its temperature sensitivity were observed during the periods of water stress(Q10=1.6).Both heat and water stress can cause decrease in FGEP.The sea-sonality of ecosystem carbon exchange was strongly correlated with the variation of precipitation.With less precipitation in 2003,the steppe sequestrated carbon in June and July,and went into a senescence in early August due to water stress.As compared to 2003,the severe drought during the spring of 2004 delayed the growth of the steppe until late June,and the steppe became a CO_(2)sink from early July until mid-September,with ample precipitation in August.The semi-arid steppe released a total of 9.7 g C·m-2 from May 16 to the end of September 2003,whereas the net carbon budget during the same period in 2004 was close to zero.Long-term measurements over various grasslands are needed to quantify carbon balance in temperate grasslands.
基金One Hundred Talent Project(0429091211)Scientific Research from the Japan Society for the Promotion of Science(JSPS+1 种基金No.18710017)JSPS-KOSEF-NSFC A3 Foresight Program(Quantifying and Predicting Terrestrial Carbon Sinks in East Asia:Toward a Network of Climate Change Research).
文摘Aims Recent studies have recognized the alpine grasslands on the Qinghai-Tibetan plateau as a significant sink for atmospheric CO_(2).The carbon-sink strength may differ among grassland ecosystems at various altitudes because of contrasting biotic and physical environments.This study aims(i)to clarify the altitudinal pattern of ecosystem CO_(2) fluxes,including gross primary production(GPP),daytime ecosystem respiration(Redaytime)and net ecosystem production(NEP),during the period with peak above-ground biomass;and(ii)to elucidate the effects of biotic and abiotic factors on the altitudinal variation of ecosystem CO_(2) fluxes.Methods Ecosystem CO_(2) fluxes and abiotic and biotic environmental factors were measured in an alpine grassland at four altitudes from 3600 to 4200 m along a slope of the Qilian Mountains on the northwestern Qinghai-Tibetan Plateau during the growing season of 2007.We used a closed-chamber method combined with shade screens and an opaque cloth to measure several carbon fluxes,GPP,Redaytime and NEP,and factors,light-response curve for GPP and temperature sensitivity of Redaytime.Above-and below-ground biomasses and soil C and N contents at each measurement point were also measured.Important Findings(i)Altitudinal pattern of ecosystem CO_(2) fluxes:The maximum net ecosystem CO_(2) flux(NEPmax),i.e.the potential ecosystem CO_(2) sink strength,was markedly different among the four altitudes.NEPmax was higher at the highest and lowest sites,ap proximately7.460.9 and6.760.6 lmol CO_(2) m^(-2)s^(-1)(mean 6 standard error),respectively,but smaller at the intermediate altitude sites(3800 and 4000 m).The altitudinal pattern of maximum gross primary production was similar to that of NEPmax.The Redaytime,however,was significantly higher at the lowest altitude(3.460.3 lmol CO_(2) m^(-2)s^(-1))than at the other three altitudes.(ii)Altitudinal variation of vegetation biomass:The aboveground biomass was higher at the highest altitude(154627 g DW m2)than at the other altitudes,which we attribute mainly to the large biomass in cushion plants at the highest altitude.The small above-ground biomass at the lower altitudes was probably due to heavy grazing during the growing season.(iii)Features of ecosystem CO_(2) fluxes:Redaytime and GPP were positively correlated with above-ground biomass.The low ratio of Redaytime to GPP at either the measurement point or the site level suggests that CO_(2) uptake efficiency tends to be higher at higher altitudes,which indicates a high potential sink strength for atmospheric CO_(2) despite the low temperature at high altitudes.The results suggest that the effect of grazing intensity on ecosystem carbon dynamics,partly by decreasing vegetation biomass,should be clarified further.
基金The Projects of Shandong Social Science Planning(21CGLJ19)The Fundamental Research Funds of Shandong University(2020GN107).
文摘Gross ecosystem product(GEP) is the gross value of all ecosystem products and services provided by ecosystems for human society. In practice, GEP measures the ecosystems’ contributions to human well-being and constitutes one of the core issues in the construction of ecological civilization systems. Currently, GEP accounting faces a series of problems, such as the inconsistency of accounting subjects and a lack of accounting standards,the result of which is the non-reproducibility and weak applicability of accounting results. In this paper, mainstream models for ecosystem service valuation are summarized in a systematic manner. On this basis, eight basic principles are established for screening accounting indicators: biological productivity, human benefits, production territoriality, current increment, actual effectiveness, physical metrizability, data availability, and harmlessness. Next, a series of ecosystem service subjects are identified that need to be excluded from accounting, and the detailed reasons for their exclusion are presented. Finally, three ideas for improving GEP accounting are offered from the perspectives of the relationship between biological production and human production, the circulation-transport relationship and spatial differences, and harms to the ecosystem carrying capacity. The purpose is to provide positive considerations aimed at promoting the socio-economic applications of accounting and to contribute to the scientific quantification of the values of ecological products.
基金JSPS-KOSEF-NSFC A3 Foresight Program(Quantifying and Predicting Terrestrial Carbon Sinks in East Asia:Toward a Network of Climate Change Research).
文摘Aims Recent studies have shown that alpine meadows on the Qinghai-Tibetan plateau act as significant CO_(2)sinks.On the plateau,alpine shrub meadow is one of typical grassland ecosystems.The major alpine shrub on the plateau is Potentilla fruticosa L.(Rosaceae),which is distributed widely from 3200 to 4000 m.Shrub species play an important role on carbon sequestration in grassland ecosystems.In addition,alpine shrubs are sensitive to climate change such as global warming.Considering global warming,the biomass and productivity of P.fruticosa will increase on Qinghai-Tibetan Plateau.Thus,understanding the carbon dynamics in alpine shrub meadow and the role of shrubs around the upper distribution limit at present is essential to predict the change in carbon sequestration on the plateau.However,the role of shrubs on the carbon dynamics in alpine shrub meadow remains unclear.The objectives of the present study were to evaluate the magnitude of CO_(2)exchange of P.fruticosa shrub patches around the upper distribution limit and to elucidate the role of P.fruticosa on ecosystem CO_(2)fluxes in an alpine meadow.Methods We used the static acrylic chamber technique to measure and estimate the net ecosystem productivity(NEP),ecosystem respiration(Re),and gross primary productivity(GPP)of P.fruticosa shrub patches at three elevations around the species’upper distribution limit.Ecosystem CO_(2)fluxes and environmental factors were measured from 17 to 20 July 2008 at 3400,3600,and 3800 m a.s.l.We examined the maximum GPP at infinite light(GPPmax)and maximum Re(Remax)during the experimental time at each elevation in relation to aboveground biomass and environmental factors,including air and soil temperature,and soil water content.Important Findings Patches of P.fruticosa around the species’upper distribution limit absorbed CO_(2),at least during the daytime.Maximum NEP at infinite light(NEPmax)and GPPmax of shrub patches in the alpine meadow varied among the three elevations,with the highest values at 3400 m and the lowest at 3800 m.GPPmax was positively correlated with the green biomass of P.fruticosa more strongly than with total green biomass,suggesting that P.fruticosa is the major contributor to CO_(2)uptake in the alpine shrub meadow.Air temperature influenced the potential GPPat the shrub-patch scale.Remax was correlated with aboveground biomass and Remax normalized by aboveground biomass was influenced by soil water content.Potentilla fruticosa height(biomass)and frequency increased clearly as elevation decreased,which promotes the large-scale spatial variation of carbon uptake and the strength of the carbon sink at lower elevations.
