Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation...Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks,aiding efforts to mitigate the detrimental effects of climate change.In this study,we utilized the precipitation and temperature data from the Climatic Research Unit,the standardized precipitation evapotranspiration index(SPEI),the standardized precipitation index(SPI),and the simulated vegetation GPP using the eddy covariance-light use efficiency(EC-LUE)model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982-2018.The main findings indicated that vegetation GPP decreased in 50.53% of the plateau,mainly in its northern and northeastern parts,while it increased in the remaining 49.47%area.Specifically,meadow steppe(78.92%)and deciduous forest(79.46%)witnessed a significant decrease in vegetation GPP,while alpine steppe(75.08%),cropland(76.27%),and sandy vegetation(87.88%)recovered well.Warming aridification areas accounted for 71.39% of the affected areas,while 28.53% of the areas underwent severe aridification,mainly located in the south and central regions.Notably,the warming aridification areas of desert steppe(92.68%)and sandy vegetation(90.24%)were significant.Climate warming was found to amplify the sensitivity of coniferous forest,deciduous forest,meadow steppe,and alpine steppe GPP to drought.Additionally,the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased.The cumulative effect of drought on vegetation GPP persisted for 3.00-8.00 months.The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.展开更多
It is necessary to quantitatively study the relationship between climate and human factors on net primary productivity(NPP)inorder to understand the driving mechanism of NPP and prevent desertification.This study inve...It is necessary to quantitatively study the relationship between climate and human factors on net primary productivity(NPP)inorder to understand the driving mechanism of NPP and prevent desertification.This study investigated the spatial and temporal differentiation features of actual net primary productivity(ANPP)in the Ili River Basin,a transboundary river between China and Kazakhstan,as well as the proportional contributions of climate and human causes to ANPP variation.Additionally,we analyzed the pixel-scale relationship between ANPP and significant climatic parameters.ANPP in the Ili River Basin increased from 2001 to 2020 and was lower in the northeast and higher in the southwest;furthermore,it was distributed in a ring around the Tianshan Mountains.In the vegetation improvement zone,human activities were the dominant driving force,whereas in the degraded zone,climate change was the primary major driving force.The correlation coefficients of ANPP with precipitation and temperature were 0.322 and 0.098,respectively.In most areas,there was a positive relationship between vegetation change,temperature and precipitation.During 2001 to 2020,the basin’s climatic change trend was warm and humid,which promoted vegetation growth.One of the driving factors in the vegetation improvement area was moderate grazing by livestock.展开更多
Net primary productivity (NPP) of the vegetation in an oasis can reflect the productivity capacity of a plant community under natural environmental conditions. Owing to the extreme arid climate conditions and scarce p...Net primary productivity (NPP) of the vegetation in an oasis can reflect the productivity capacity of a plant community under natural environmental conditions. Owing to the extreme arid climate conditions and scarce precipitation in the arid oasis regions, groundwater plays a key role in restricting the development of the vegetation. The Qira Oasis is located on the southern margin of the Taklimakan Desert (Tarim Basin, China) that is one of the most vulnerable regions regarding vegetation growth and water scarcity in the world. Based on remote sensing images of the Qira Oasis and daily meteorological data measured by the ground stations during the period 2006-2019, this study analyzed the temporal and spatial patterns of NPP in the oasis as well as its relation with the variation of groundwater depth using a modified Carnegie Ames Stanford Approach (CASA) model. At the spatial scale, NPP of the vegetation decreased from the interior of the Qira Oasis to the margin;at the temporal scale, NPP of the vegetation in the oasis fluctuated significantly (ranging from 29.80 to 50.07 g C/(m2•month)) but generally showed an increasing trend, with the average increase rate of 0.07 g C/(m2•month). The regions with decreasing NPP occupied 64% of the total area of the oasis. During the study period, NPP of both farmland and grassland showed an increasing trend, while that of forest showed a decreasing trend. The depth of groundwater was deep in the south of the oasis and shallow in the north, showing a gradual increasing trend from south to north. Groundwater, as one of the key factors in the surface change and evolution of the arid oasis, determines the succession direction of the vegetation in the Qira Oasis. With the increase of groundwater depth, grassland coverage and vegetation NPP decreased. During the period 2008-2015, with the recovery of groundwater level, NPP values of all types of vegetation with different coverages increased. This study will provide a scientific basis for the rational utilization and sustainable management of groundwater resources in the oasis.展开更多
With global warming, the great changes in the patterns of plant growth have occurred. The conditions in early spring and late autumn have changed the process of vegetation photosynthesis, which are expected to have a ...With global warming, the great changes in the patterns of plant growth have occurred. The conditions in early spring and late autumn have changed the process of vegetation photosynthesis, which are expected to have a significant impact on net primary productivity(NPP) and affect the global carbon cycle. Currently, the seasonal response characteristics of NPP to phenological changes in dryland ecosystems are still not well defined. This article calibrated and analyzed the normalized difference vegetation index(NDVI)time series of Advanced Very-High-Resolution Radiometer(AVHRR) data from 1982 to 2015 in the Loess Plateau, China. The spatial and temporal distributions of vegetation phenology and NPP in the Loess Plateau under semihumid and semiarid conditions were investigated. The seasonal variation in the NPP response to vegetation phenology under the climate change was also analyzed. The results showed that, different from the northern forest, there was distinct spatial heterogeneity in the effect of climate change on the dynamic change in vegetation growth in the Loess Plateau: 1) an advance of the start of the growing season(SOS) and a delay of the end of the growing season(EOS) significantly increased the NPP in spring and autumn, respectively, in the humid southeast;2) in the arid northwest, the NPP did not significantly increase in spring and autumn but significantly decreased in summer.展开更多
Vegetation growth status is an important indicator of ecological security.The Tarim River Basin is located in the inland arid region of Northwest China and has a highly fragile ecological environment.Assessing the veg...Vegetation growth status is an important indicator of ecological security.The Tarim River Basin is located in the inland arid region of Northwest China and has a highly fragile ecological environment.Assessing the vegetation net primary productivity(NPP)of the Tarim River Basin can provide insights into the vegetation growth variations in the region.Therefore,based on the Google Earth Engine(GEE)cloud platform,we studied the spatiotemporal variation of vegetation NPP in the Tarim River Basin(except for the eastern Gobi and Kumutag deserts)from 2001 to 2020 and analyzed the correlations between vegetation NPP and meteorological factors(air temperature and precipitation)using the Sen slope estimation method,coefficient of variation,and rescaled range analysis method.In terms of temporal characteristics,vegetation NPP in the Tarim River Basin showed an overall fluctuating upward trend from 2001 to 2020,with the smallest value of 118.99 g C/(m2•a)in 2001 and the largest value of 155.07 g C/(m2•a)in 2017.Regarding the spatial characteristics,vegetation NPP in the Tarim River Basin showed a downward trend from northwest to southeast along the outer edge of the study area.The annual average value of vegetation NPP was 133.35 g C/(m2•a),and the area with annual average vegetation NPP values greater than 100.00 g C/(m2•a)was 82,638.75 km2,accounting for 57.76%of the basin.The future trend of vegetation NPP was dominated by anti-continuity characteristic;the percentage of the area with anti-continuity characteristic was 63.57%.The area with a significant positive correlation between vegetation NPP and air temperature accounted for 53.74%of the regions that passed the significance test,while the area with a significant positive correlation between vegetation NPP and precipitation occupied 98.68%of the regions that passed the significance test.Hence,the effect of precipitation on vegetation NPP was greater than that of air temperature.The results of this study improve the understanding on the spatiotemporal variation of vegetation NPP in the Tarim River Basin and the impact of meteorological factors on vegetation NPP.展开更多
Individual coal seams formed in paleo-peatlands represent sustained periods of terrestrial carbon accumulation and a key environmental indicator attributed to this record is the rate of carbon accumulation.Determining...Individual coal seams formed in paleo-peatlands represent sustained periods of terrestrial carbon accumulation and a key environmental indicator attributed to this record is the rate of carbon accumulation.Determining the rate of carbon accumulation requires a measure of time contained within the coal.This study aimed to determine this rate via the identification of Milankovitch orbital cycles in the coals.The geophysical log is an ideal paleoclimate proxy and has been widely used in the study of sedimentary records using spectral analysis.Spectral analyses of geophysical log from thick coal seams can be used to identify the Milankovitch cycles and to calculate the period of the coal deposition.By considering the carbon loss during coalification,the long-term average carbon accumulation rate and net primary productivity(NPP)of paleo-peatlands in coal seams can be obtained.This review paper presents the procedures of analysis,assessment of results and interpretation of geophysical logs in determining the NPP of paleo-peatlands.展开更多
Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutrient into coastal waters,and generally comprises two components:submarine fresh groundwater discharge(SFGD)and recirc...Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutrient into coastal waters,and generally comprises two components:submarine fresh groundwater discharge(SFGD)and recirculated saline groundwater discharge(RSGD).The separate evaluation of SFGD and RSGD is extremely limited as compared to the conventional estimation of total SGD and associated nutrient fluxes,especially in marginal-scale regions.In this study,new high-resolution radium isotopes data in seawater and coastal groundwater enabled an estimation of SGD flux in a typical marginal sea of the Yellow Sea.By establishing 226Ra and 228Ra mass balance models,we obtained the SGD-derived radium fluxes,and then estimated the SFGD and RSGD fluxes through a two end-member model.The results showed that the total SGD flux into the Yellow Sea was equivalent to approximately 6.6 times the total freshwater discharge of surrounding rivers,and the SFGD flux accounted for only 5.2%–8.8%of the total SGD.Considering the nutrient concentrations in coastal fresh and saline groundwater,we obtained the dissolved inorganic nutrient fluxes(mmol m^(-2) yr^(-1))to be 52–353 for nitrogen(DIN),0.21–1.4 for phosphorus(DIP),34–226 for silicon(DSi)via SFGD,and 69–262 for DIN,1.0–3.9 for DIP,70–368 for DSi via RSGD,with the sum of nutrient fluxes equaling to(1.8–9.3)-fold,(1.3–5.6)-fold and(2.0–9.5)-fold of the riverine inputs.Compared to the conventional estimation of the total SGD flux,the nutrient fluxes derived from the separation of SFGD and RSGD were(1.6–2.1),(1.6–1.8)and(4.0–4.9)times lower for DIN,DIP and DSi,respectively,indicating that the estimates by separating SFGD and RSGD could be conservative and representative results of the Yellow Sea.Furthermore,we suggested that SGD played an important role in nutrient sources among all the traditional nutrient inputs sources,providing 15%–48%,33%–68%and 14%–43%of the total DIN,DIP and DSi input fluxes into the Yellow Sea,and the high nutrient stoichiometric ratios(i.e.,DIN/DIP)in SGD probably contributed to the increasing ratios in the Yellow Sea.In addition delivering large amounts of nutrient into the Yellow Sea,SGD would create primary productivity of 10–49,1.6–6.8 and 8.8–42 g C m^(-2)yr^(-1) based on N,P and Si,which were equivalent to 5.2%–27%,0.9%–3.7%and 4.7%–23%of the total primary productivity,respectively.In particular,the SFGD-derived DIN flux can be converted to primary productivity of 4.2–28 g C m^(-2)yr^(-1) thus demonstrating the disproportionately large role of SFGD in ecological environment of the Yellow Sea relative to its flux.Therefore,we conclude that SGD,particularly SFGD,plays an important role as a nutrient source for the Yellow Sea,and not only affects nutrient budgets and structures but also enhances the primary productivity.展开更多
The net primary productivity of vegetation reflects the total amount of carbon fixed by plants through photosynthesis each year. The study of vegetation net primary productivity is one of the core contents of global c...The net primary productivity of vegetation reflects the total amount of carbon fixed by plants through photosynthesis each year. The study of vegetation net primary productivity is one of the core contents of global change and terrestrial ecosystems. This article reviews the current research status of net primary productivity of terrestrial vegetation, and comprehensively analyzes the advantages and disadvantages of three types of productivity estimation models, climate relative models, biogeochemical models, and light energy utilization models. The light energy utilization models have become the mainstream method for estimating vegetation net primary productivity because they can directly use remote sensing data. However, there are still many deficiencies in the estimation of vegetation net primary productivity, which need to be further improved and tested.展开更多
The dynamic variation of net primary productivity of artificial Pinus tabulaeformis forest was studied in Shanxi Province,and potential productivity of artificial forest was predicted to provide reference for improvin...The dynamic variation of net primary productivity of artificial Pinus tabulaeformis forest was studied in Shanxi Province,and potential productivity of artificial forest was predicted to provide reference for improving quality of regional forest stand. The regression equation was established by using the stratification and harvesting method with the relative growth model. Cumulative method and Thornthwaite Memorial model was used to estimate the actual and potential productivity of the forest. The productivity of P. tabulaeformis forest increased with the increase of age and started decrease with the mature period. The actual productivity of P. tabulaeformis forest was 4. 462 t/( ha·year); the contribution rate of trees was 72. 17% of the total productivity,and with the increase of age,the total biomass increased but productivity decreased at late near-mature forest; the contribution rate of herb layer was 21. 16% in the young forest stage,and then decreased gradually. On the contrary,the contribution rate of shrub layer increased gradually,and the contribution rate of the grassland was more than that of the herb layer,so as the key period of structural management; the average potential productivity of forest was 8. 422 t/( ha·year),and the potential space of P. tabulaeformis was at least 32% in Shanxi Province. In conclusion,the potential space of productivity of P. tabulaeformis was at least 32%,and the primary limiting factor of P. tabulaeformis forest productivity in Shanxi Province was rainfall.展开更多
Vegetation net primary productivity(NPP)is a sensitive indicator to characterize the response of terrestrial ecosystems to the climate change.Projections of the NPP changes of the Loess Plateau under future climate sc...Vegetation net primary productivity(NPP)is a sensitive indicator to characterize the response of terrestrial ecosystems to the climate change.Projections of the NPP changes of the Loess Plateau under future climate scenarios have great significances in revealing the interactions among terrestrial ecosystems and climatic systems,as well as instructing future vegetation construction of this region.Here,we carried out a case study on the Yangou watershed in the Loess Plateau.Using the vegetation-producing process model(VPP)established for such small watersheds,we simulated the NPP of the Yangou watershed under different scenarios of climate changes.The results showed that the NPP significandy increased with the precipitation increasing and evidently decreased with the temperature increasing where the climate change occurred in the whole year or in the summer half year.However,where the climate change occurred in the winter half year,the increased precipitation had little effect on the NPP,and the increased temperature significantly reduced the NPP.There were clear differences among the response sensitivities of different vegetation types with trees and shrubs were more sensitive to the changes in temperature and precipitation than crops and grasses.Currently,the most favourable climate change scenario to the NPP in the Yangou watershed was T0P15 under which the precipitation increased by 15%and the temperature did not changed,in the whole year;in the meantime,the most unfavourable climate change scenarios was T2P-15 under which the precipitation declined by 15%and the temperature increased by 2℃,in the whole year.展开更多
INTRODUCTIONThe coast zone is the area where most human activities take place and where the highest economic benefit is produced. The knowledge of the distribution and variation of primary production provides the base...INTRODUCTIONThe coast zone is the area where most human activities take place and where the highest economic benefit is produced. The knowledge of the distribution and variation of primary production provides the bases as reference helping the marine exploitation and management.展开更多
Net Primary Productivity (NPP) is the basis of the material and energy transport calculation in ecosystem studies. NPP directly reflects the production capacity of plant communities under natural conditions. Ecosystem...Net Primary Productivity (NPP) is the basis of the material and energy transport calculation in ecosystem studies. NPP directly reflects the production capacity of plant communities under natural conditions. Ecosystem services are hot topics in the field of ecology. Many studies calculate ecosystem service value based on NPP. Taking Guanshanhu District of Guiyang City, Guizhou Province as the research object, using TM, ETM<sup>+</sup>, Gaofen2 and MOD17A3HGF.006 as data sources, this paper analyzed the change of ecosystem service value based on NPP in 2000, 2010 and 2020. The results showed that the area of forest ecosystem increased during 2000-2010 and decreased during 2010-2020. The artificial surface grew rapidly from 1146.82 hm<sup>2</sup> to 7544.29 hm<sup>2</sup> during 2000-2020. The farmland ecosystem decreased from 13308.29 hm<sup>2</sup> to 6342.33 hm<sup>2</sup> during 2000-2020. With the dynamic changes in ecosystem spatial distribution and component structure, the total NPP in 2000, 2010 and 2020 was 12.58 × 10<sup>4</sup> t, 11.90 × 10<sup>4</sup> t and 11.78 × 10<sup>4</sup> t, respectively, showing a decreasing trend. The total value of natural and semi-natural ecosystems services based on NPP showed an increasing trend, which was ￥ 6.938 × 10<sup>8</sup> in 2000, ￥ 8.052 × 10<sup>8</sup> in 2010 and ￥ 10.306 × 10<sup>8</sup> in 2020 respectively. The ecosystem contributed the most to the ecological service value in 2000 was farmland, but in 2010 and 2020, it was the forest ecosystem. The ecological service value of grassland and wetland was relatively small, while the ratio of the wetland ecological service value displayed a decreasing trend. In the future, it is necessary to establish a strict pretrial system for land use, so as to effectively protect the natural and semi-natural ecosystems and fulfill the growing ecological demands of residents.展开更多
Background:Net primary productivity(NPP)in forests plays an important role in the global carbon cycle.However,it is not well known about the increase rate of China’s forest NPP,and there are different opinions about ...Background:Net primary productivity(NPP)in forests plays an important role in the global carbon cycle.However,it is not well known about the increase rate of China’s forest NPP,and there are different opinions about the key factors controlling the variability of forest NPP.Methods:This paper established a statistics-based multiple regression model to estimate forest NPP,using the observed NPP,meteorological and remote sensing data in five major forest ecosystems.The fluctuation values of NPP and environment variables were extracted to identify the key variables influencing the variation of forest NPP by correlation analysis.Results:The long-term trends and annual fluctuations of forest NPP between 2000 and 2018 were examined.The results showed a significant increase in forest NPP for all five forest ecosystems,with an average rise of 5.2 gC·m-2·year-1 over China.Over 90%of the forest area had an increasing NPP range of 0-161 gC·m-2·year-1.Forest NPP had an interannual fluctuation of 50-269 gC.m-2·year-1 for the five major forest ecosystems.The evergreen broadleaf forest had the largest fluctuation.The variability in forest NPP was caused mainly by variations in precipitation,then by temperature fluctuations.Conclusions:All five forest ecosystems in China exhibited a significant increasing NPP along with annual fluctuations evidently during 2000-2018.The variations in China’s forest NPP were controlled mainly by changes in precipitation.展开更多
Background:The article presents the first estimates of biomass and productivity for mangrove forests along the Oligohaline zone of the Sundarbans Reserve Forest(SRF),Bangladesh.This study was conducted overone year fr...Background:The article presents the first estimates of biomass and productivity for mangrove forests along the Oligohaline zone of the Sundarbans Reserve Forest(SRF),Bangladesh.This study was conducted overone year from March 2016 to April 2017.Stand structure,above and below-ground biomass changes,and litterfall production were measured within a 2100 m^2 sample plot.Methods:All trees in the study plots were numbered and height(H) and diameter at breast height(DBH) were measured.Tree height(H) and DBH for each tree were measured in March 2016 and 2017.We apply the above and belowground biomass equation for estimating the biomass of the mangrove tree species(Chave et al.Oecologia145:87-99,2005; Komiyama et al.J Trop Ecol 21:471-477,2005).Litterfall was collected using 1-mm mesh litter traps with collection area of 0.42 m^2.Net Primary Production(NPP) was estimated by the summation method of Ogawa Primary productivity of Japanese forests:productivity of terrestrial communities,JIBP synthesis(1977) and Matsuura and Kajimoto Carbon dynamics of terrestrial ecosystem:Systems approach to global environment(2013).Results:Heritiera fomes has maintained its dominance of the stand and also suffered the highest tree mortality(2.4%) in the suppressed crown class.The total above-ground biomass(AGB) and below-ground biomass(BGB) of the studied stand was 154.8 and 84.2 Mg ha^(-1),respectively.Among the total biomass of the trees,64.8% was allocated to AGB and 35.2% to BGB.In case of species-wise contribution of biomass allocation,Avicennia officinalis showed the highest score and Aglaia cucullata the lowest.Mean annual total litterfall was 10.1 Mg ha^(-1)·yr^(-1),with the maximum litterfall in winter or dry season and late summer or rainy season.The mean AGB increment and above-ground net primary productivity(AGNPP) were 7.1 and 172 Mg·ha^(-1)·yr^(-1),respectively.Total net primary productivity(NPP) was estimated to be 21.0 Mg·ha^(-1)·yr^(-1) over the observed period.The results in the Sundarbans mangrove forests exhibited that mangrove communities with similar height and diameter produced different biomass production with the different basal area.The present analysis revealed that the root biomass was large enough and the mean ratio of above-/below-ground biomass was estimated to be 1.84.Conclusions:Mangrove communities growing at the oligohaline zone of the Sundarbans,Bangladesh showed high biomass and net primary production indicating their ecological and conservation significance that may be considered in future decision making process for the area as well as in understanding the role of Sundarbans mangrove forest on mitigating the effect of global warming.展开更多
Current ecosystem models used to simulate global terrestrial carbon balance generally suggest that terrestrial landscapes are stable and mature,but terrestrial net primary productivity(NPP)data estimated without accou...Current ecosystem models used to simulate global terrestrial carbon balance generally suggest that terrestrial landscapes are stable and mature,but terrestrial net primary productivity(NPP)data estimated without accounting for disturbances in species composition,environment,structure,and ecological characteristics will reduce the accuracy of the global carbon budget.Therefore,the steady-state assumption and neglect of elevation-related changes in forest NPP is a concern.The Qilian Mountains are located in continental climate zone,and vegetation is highly sensitive to climate change.We quantified aboveground biomass(AGB)and aboveground net primary productivity(ANPP)sequences at three elevations using field-collected tree rings of Picea crassifolia in Qilian Mountains of Northwest China.The results showed that(1)There were significant differences between AGB and ANPP at the three elevations,and the growth rate of AGB was the highest at the low elevation(55.99 t ha^(–1)10a^(–1)).(2)There are differences in the response relationship between the ANPP and climate factors at the three elevations,and drought stress is the main climate signal affecting the change of ANPP.(3)Under the future climate scenario,drought stress intensifies,and the predicted decline trend of ANPP at the three elevations from mid-century to the end of this century is–0.025 t ha^(–1)10a^(–1),respectively;–0.022 t ha^(–1)10a^(–1);At–0.246 t ha^(–1)10a^(–1),the level of forest productivity was significantly degraded.The results reveal the elevation gradient differences in forest productivity levels and provide key information for studying the carbon sink potential of boreal forests.展开更多
The pan-Arctic is confronted with air pollution transported from lower latitudes.Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects(DRFEs).Whil...The pan-Arctic is confronted with air pollution transported from lower latitudes.Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects(DRFEs).While such DRFEs have been explored at low to middle latitudes,the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified.Here,we perform regional simulations at 0.2o×0.2ousing a well-validated vegetation model(Yale Interactive terrestrial Biosphere,YIBs)in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity(NPP)in the pan-Arctic during 2001-19.Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C(12.8%)yr^(-1)under clear-sky conditions,in which natural and anthropogenic sources contribute to 8.9% and 3.9%,respectively.Under all-sky conditions,such DRFEs are largely dampened by cloud to only 0.26 Pg C(1.24%)yr^(-1),with contributions of 0.65% by natural and 0.59% by anthropogenic species.Natural aerosols cause a positive NPP trend of 0.022% yr^(-1)following the increased fire activities in the pan-Arctic.In contrast,anthropogenic aerosols induce a negative trend of-0.01% yr^(-1)due to reduced emissions from the middle latitudes.Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter.Though affected by modeling uncertainties,this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming.展开更多
The biomass and productivity of Schima superba-Castanopsis carlesii forests in Tiantong,Zhejiang Province,were determined using overlapping quadrants and stem analyses.The total community biomass was(225.3±30.1) ...The biomass and productivity of Schima superba-Castanopsis carlesii forests in Tiantong,Zhejiang Province,were determined using overlapping quadrants and stem analyses.The total community biomass was(225.3±30.1) t hm-2,of which the aboveground parts accounted for 72.0% and the underground parts accounted for 28.0%.About 87.2% of biomass existed in the tree layer.The resprouting biomass was small,of which over 95.0% occurred in the shrub layer.The productivity of the aboveground parts of the community was(386.8±98.9) g m-2a-1,in which more than 96.0% was present at the tree level.The trunk's contribution to productivity was the greatest,while that of leaves was the smallest.In China,the community biomass of subtropical evergreen broadleaved forests differs significantly with the age of the forest.The community biomass of the 52-year-old S.superba-C.carlesii forests in this study was lower than the average biomass of subtropical evergreen broadleaved forests in China,and was lower than the biomass of other subtropical evergreen broadleaved forests elsewhere in the world.Moreover,its productivity was lower than the model estimate,indicating that without disturbance,this community has great developmental potential in terms of community biomass and productivity.展开更多
Ecological restoration measures implemented in China have profoundly impacted vegetation NPP.This study aimed to estimate the effects of the land conversion and management measures on the grassland ecosystem in semi-a...Ecological restoration measures implemented in China have profoundly impacted vegetation NPP.This study aimed to estimate the effects of the land conversion and management measures on the grassland ecosystem in semi-arid regions.Land use data were employed from 2000 to 2015 to compare land conversion and coverage changes in Xilingol grassland.Then,the contributions of land conversion and management policies were quantified by assessing the difference between actual NPP and climate-induced NPP changes.The results indicated that the grassland area had a net loss of 534.42 km^(2),and the net area of increased vegetation coverage was 74,683.05 km^(2).Furthermore,the total NPP increased by 8,010.73 Gg C·yr^(−1)(1 Gg=10^(9)g),of which the human activities,including grazing management measures(+6,809.40 Gg C·yr^(−1))and land conversion(45.72 Gg C·yr^(−1))contributed to 85.58%of the increase in NPP.Transformation from desert and farmland dominated grassland expansion and NPP increase,while urbanization and desertification caused large grassland reduction and NPP loss.The grazing management increased vegetation NPP in most regions except for some regions in the desert steppe and the farming-pastoral zone.Related policies should be further adjusted to strengthen the management of the desert steppe and farming-pastoral regions.展开更多
Understanding patterns and determinants of net primary productivity(NPP)in global grasslands is ongoing challenges,especially for belowground NPP(BNPP)and its fraction(fBNPP).By developing a comprehensive field-based ...Understanding patterns and determinants of net primary productivity(NPP)in global grasslands is ongoing challenges,especially for belowground NPP(BNPP)and its fraction(fBNPP).By developing a comprehensive field-based dataset,we revealed that,along with gradients of mean annual precipitation,actual evapotranspiration,and aridity,aboveground NPP(ANPP),BNPP,and total NPP(TNPP)exhibited hump-shaped patterns,whereas fBNPPshowed an opposite trend.ANPP and TNPP showed positive correlations with mean annual temperature,but fBNPPwas negatively correlated with it.The relationship between BNPP and climatic factors was considerably weak,indicating that BNPP was relatively stable regardless of the climate conditions.We also observed that the sensitivities of ANPP and BNPP to interannual temperature variability and those of BNPP to interannual precipitation fluctuations exhibited large variations among different study sites,and differed from those at the spatial scale.In contrast,the temporal sensitivities of ANPP to interannual precipitation variability were highly similar across all the individual sites and much smaller than those at the spatial scale.Overall,these results highlight that precipitation,temperature and evapotranspiration all play vital roles in shaping ANPP pattern and its partitioning to belowground and that the patterns of BNPP along climatic gradients do not mirror those of the ANPP.展开更多
Currently,the satellite data used to estimate terrestrial net primary productivity(NPP)in China are predominantly from foreign satellites,and very few studies have based their estimates on data from China’s Fengyun s...Currently,the satellite data used to estimate terrestrial net primary productivity(NPP)in China are predominantly from foreign satellites,and very few studies have based their estimates on data from China’s Fengyun satellites.Moreover,despite their importance,the influence of land cover types and the normalized difference vegetation index(NDVI)on NPP estimation has not been clarified.This study employs the Carnegie–Ames–Stanford approach(CASA)model to compute the fraction of absorbed photosynthetically active radiation and the maximum light use efficiency suitable for the main vegetation types in China in accordance with the finer resolution observation and monitoring-global land cover(FROM-GLC)classification product.Then,the NPP is estimated from the Fengyun-3D(FY-3D)data and compared with the Moderate Resolution Imaging Spectroradiometer(MODIS)NPP product.The FY-3D NPP is also validated with existing research results and historical field-measured NPP data.In addition,the effects of land cover types and the NDVI on NPP estimation are analyzed.The results show that the CASA model and the FY-3D satellite data estimate an average NPP of 441.2 g C m^(−2) yr^(−1) in 2019 for China’s terrestrial vegetation,while the total NPP is 3.19 Pg C yr^(−1).Compared with the MODIS NPP,the FY-3D NPP is overestimated in areas of low vegetation productivity and is underestimated in high-productivity areas.These discrepancies are largely due to the differences between the FY-3D NDVI and MODIS NDVI.Compared with historical field-measured data,the FY-3D NPP estimation results outperformed the MODIS NPP results,although the deviation between the FY-3D NPP estimate and the in-situ measurement was large and may exceed 20%at the pixel scale.The land cover types and the NDVI significantly affected the spatial distribution of NPP and accounted for NPP deviations of 17.0%and 18.1%,respectively.Additionally,the total deviation resulting from the two factors reached 29.5%.These results show that accurate NDVI products and land cover types are important prerequisites for NPP estimation.展开更多
基金jointly supported by the National Natural Science Foundation of China(42361024,42101030,42261079,and 41961058)the Talent Project of Science and Technology in Inner Mongolia of China(NJYT22027 and NJYT23019)the Fundamental Research Funds for the Inner Mongolia Normal University,China(2022JBBJ014 and 2022JBQN093)。
文摘Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks,aiding efforts to mitigate the detrimental effects of climate change.In this study,we utilized the precipitation and temperature data from the Climatic Research Unit,the standardized precipitation evapotranspiration index(SPEI),the standardized precipitation index(SPI),and the simulated vegetation GPP using the eddy covariance-light use efficiency(EC-LUE)model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982-2018.The main findings indicated that vegetation GPP decreased in 50.53% of the plateau,mainly in its northern and northeastern parts,while it increased in the remaining 49.47%area.Specifically,meadow steppe(78.92%)and deciduous forest(79.46%)witnessed a significant decrease in vegetation GPP,while alpine steppe(75.08%),cropland(76.27%),and sandy vegetation(87.88%)recovered well.Warming aridification areas accounted for 71.39% of the affected areas,while 28.53% of the areas underwent severe aridification,mainly located in the south and central regions.Notably,the warming aridification areas of desert steppe(92.68%)and sandy vegetation(90.24%)were significant.Climate warming was found to amplify the sensitivity of coniferous forest,deciduous forest,meadow steppe,and alpine steppe GPP to drought.Additionally,the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased.The cumulative effect of drought on vegetation GPP persisted for 3.00-8.00 months.The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.
基金Under the auspices of the Key Laboratory of Xinjiang Science and Technology Department(No.2022D04009)National Social Science Foundation of China’s Major Program(No.17ZDA064)。
文摘It is necessary to quantitatively study the relationship between climate and human factors on net primary productivity(NPP)inorder to understand the driving mechanism of NPP and prevent desertification.This study investigated the spatial and temporal differentiation features of actual net primary productivity(ANPP)in the Ili River Basin,a transboundary river between China and Kazakhstan,as well as the proportional contributions of climate and human causes to ANPP variation.Additionally,we analyzed the pixel-scale relationship between ANPP and significant climatic parameters.ANPP in the Ili River Basin increased from 2001 to 2020 and was lower in the northeast and higher in the southwest;furthermore,it was distributed in a ring around the Tianshan Mountains.In the vegetation improvement zone,human activities were the dominant driving force,whereas in the degraded zone,climate change was the primary major driving force.The correlation coefficients of ANPP with precipitation and temperature were 0.322 and 0.098,respectively.In most areas,there was a positive relationship between vegetation change,temperature and precipitation.During 2001 to 2020,the basin’s climatic change trend was warm and humid,which promoted vegetation growth.One of the driving factors in the vegetation improvement area was moderate grazing by livestock.
基金This research was supported by the West Light Foundation of the Chinese Academy of Sciences(2018-XBQNXZ-B-017)the High-Level Talents Project in Xinjiang(Y942171)This study was also supported by the CAS President's International Fellowship Initiative(PIFI)Project(2021VCA0003,2021VCB0013).
文摘Net primary productivity (NPP) of the vegetation in an oasis can reflect the productivity capacity of a plant community under natural environmental conditions. Owing to the extreme arid climate conditions and scarce precipitation in the arid oasis regions, groundwater plays a key role in restricting the development of the vegetation. The Qira Oasis is located on the southern margin of the Taklimakan Desert (Tarim Basin, China) that is one of the most vulnerable regions regarding vegetation growth and water scarcity in the world. Based on remote sensing images of the Qira Oasis and daily meteorological data measured by the ground stations during the period 2006-2019, this study analyzed the temporal and spatial patterns of NPP in the oasis as well as its relation with the variation of groundwater depth using a modified Carnegie Ames Stanford Approach (CASA) model. At the spatial scale, NPP of the vegetation decreased from the interior of the Qira Oasis to the margin;at the temporal scale, NPP of the vegetation in the oasis fluctuated significantly (ranging from 29.80 to 50.07 g C/(m2•month)) but generally showed an increasing trend, with the average increase rate of 0.07 g C/(m2•month). The regions with decreasing NPP occupied 64% of the total area of the oasis. During the study period, NPP of both farmland and grassland showed an increasing trend, while that of forest showed a decreasing trend. The depth of groundwater was deep in the south of the oasis and shallow in the north, showing a gradual increasing trend from south to north. Groundwater, as one of the key factors in the surface change and evolution of the arid oasis, determines the succession direction of the vegetation in the Qira Oasis. With the increase of groundwater depth, grassland coverage and vegetation NPP decreased. During the period 2008-2015, with the recovery of groundwater level, NPP values of all types of vegetation with different coverages increased. This study will provide a scientific basis for the rational utilization and sustainable management of groundwater resources in the oasis.
基金Under the auspices of MOE(Ministry of Education in China)Project of Humanities and Social Sciences(No.20YJC840027)Natural Science Basic Research Program of Shaanxi,China(No.2021JQ-771,No.2021JQ-768)Soft Science Project of Xi’an Science and Technology Bureau,Shaanxi Province(No.2021-0013)。
文摘With global warming, the great changes in the patterns of plant growth have occurred. The conditions in early spring and late autumn have changed the process of vegetation photosynthesis, which are expected to have a significant impact on net primary productivity(NPP) and affect the global carbon cycle. Currently, the seasonal response characteristics of NPP to phenological changes in dryland ecosystems are still not well defined. This article calibrated and analyzed the normalized difference vegetation index(NDVI)time series of Advanced Very-High-Resolution Radiometer(AVHRR) data from 1982 to 2015 in the Loess Plateau, China. The spatial and temporal distributions of vegetation phenology and NPP in the Loess Plateau under semihumid and semiarid conditions were investigated. The seasonal variation in the NPP response to vegetation phenology under the climate change was also analyzed. The results showed that, different from the northern forest, there was distinct spatial heterogeneity in the effect of climate change on the dynamic change in vegetation growth in the Loess Plateau: 1) an advance of the start of the growing season(SOS) and a delay of the end of the growing season(EOS) significantly increased the NPP in spring and autumn, respectively, in the humid southeast;2) in the arid northwest, the NPP did not significantly increase in spring and autumn but significantly decreased in summer.
基金funded by the National Natural Science Foundation of China(42161049,41761019,41061052)the Special Project for Talent Development in the Western Region(201408655089).
文摘Vegetation growth status is an important indicator of ecological security.The Tarim River Basin is located in the inland arid region of Northwest China and has a highly fragile ecological environment.Assessing the vegetation net primary productivity(NPP)of the Tarim River Basin can provide insights into the vegetation growth variations in the region.Therefore,based on the Google Earth Engine(GEE)cloud platform,we studied the spatiotemporal variation of vegetation NPP in the Tarim River Basin(except for the eastern Gobi and Kumutag deserts)from 2001 to 2020 and analyzed the correlations between vegetation NPP and meteorological factors(air temperature and precipitation)using the Sen slope estimation method,coefficient of variation,and rescaled range analysis method.In terms of temporal characteristics,vegetation NPP in the Tarim River Basin showed an overall fluctuating upward trend from 2001 to 2020,with the smallest value of 118.99 g C/(m2•a)in 2001 and the largest value of 155.07 g C/(m2•a)in 2017.Regarding the spatial characteristics,vegetation NPP in the Tarim River Basin showed a downward trend from northwest to southeast along the outer edge of the study area.The annual average value of vegetation NPP was 133.35 g C/(m2•a),and the area with annual average vegetation NPP values greater than 100.00 g C/(m2•a)was 82,638.75 km2,accounting for 57.76%of the basin.The future trend of vegetation NPP was dominated by anti-continuity characteristic;the percentage of the area with anti-continuity characteristic was 63.57%.The area with a significant positive correlation between vegetation NPP and air temperature accounted for 53.74%of the regions that passed the significance test,while the area with a significant positive correlation between vegetation NPP and precipitation occupied 98.68%of the regions that passed the significance test.Hence,the effect of precipitation on vegetation NPP was greater than that of air temperature.The results of this study improve the understanding on the spatiotemporal variation of vegetation NPP in the Tarim River Basin and the impact of meteorological factors on vegetation NPP.
基金supported by the National Natural Science Foundation of China(Grant Nos.41030213 and 41572090)the Fundamental Research Funds for the Central Universities(Grant No.2022YJSDC05)the Yue Qi Scholar Project of China University of Mining and Technology(Beijing).
文摘Individual coal seams formed in paleo-peatlands represent sustained periods of terrestrial carbon accumulation and a key environmental indicator attributed to this record is the rate of carbon accumulation.Determining the rate of carbon accumulation requires a measure of time contained within the coal.This study aimed to determine this rate via the identification of Milankovitch orbital cycles in the coals.The geophysical log is an ideal paleoclimate proxy and has been widely used in the study of sedimentary records using spectral analysis.Spectral analyses of geophysical log from thick coal seams can be used to identify the Milankovitch cycles and to calculate the period of the coal deposition.By considering the carbon loss during coalification,the long-term average carbon accumulation rate and net primary productivity(NPP)of paleo-peatlands in coal seams can be obtained.This review paper presents the procedures of analysis,assessment of results and interpretation of geophysical logs in determining the NPP of paleo-peatlands.
基金This research was supported by the National Natural Science Foundation of China(Grants Nos.41376089,41576083,41976040)the National Science and Technology Major Project of the Ministry of Science and Technology of China(2016YFC1402106)China Postdoctoral Science Foundation(2020M671048)。
文摘Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutrient into coastal waters,and generally comprises two components:submarine fresh groundwater discharge(SFGD)and recirculated saline groundwater discharge(RSGD).The separate evaluation of SFGD and RSGD is extremely limited as compared to the conventional estimation of total SGD and associated nutrient fluxes,especially in marginal-scale regions.In this study,new high-resolution radium isotopes data in seawater and coastal groundwater enabled an estimation of SGD flux in a typical marginal sea of the Yellow Sea.By establishing 226Ra and 228Ra mass balance models,we obtained the SGD-derived radium fluxes,and then estimated the SFGD and RSGD fluxes through a two end-member model.The results showed that the total SGD flux into the Yellow Sea was equivalent to approximately 6.6 times the total freshwater discharge of surrounding rivers,and the SFGD flux accounted for only 5.2%–8.8%of the total SGD.Considering the nutrient concentrations in coastal fresh and saline groundwater,we obtained the dissolved inorganic nutrient fluxes(mmol m^(-2) yr^(-1))to be 52–353 for nitrogen(DIN),0.21–1.4 for phosphorus(DIP),34–226 for silicon(DSi)via SFGD,and 69–262 for DIN,1.0–3.9 for DIP,70–368 for DSi via RSGD,with the sum of nutrient fluxes equaling to(1.8–9.3)-fold,(1.3–5.6)-fold and(2.0–9.5)-fold of the riverine inputs.Compared to the conventional estimation of the total SGD flux,the nutrient fluxes derived from the separation of SFGD and RSGD were(1.6–2.1),(1.6–1.8)and(4.0–4.9)times lower for DIN,DIP and DSi,respectively,indicating that the estimates by separating SFGD and RSGD could be conservative and representative results of the Yellow Sea.Furthermore,we suggested that SGD played an important role in nutrient sources among all the traditional nutrient inputs sources,providing 15%–48%,33%–68%and 14%–43%of the total DIN,DIP and DSi input fluxes into the Yellow Sea,and the high nutrient stoichiometric ratios(i.e.,DIN/DIP)in SGD probably contributed to the increasing ratios in the Yellow Sea.In addition delivering large amounts of nutrient into the Yellow Sea,SGD would create primary productivity of 10–49,1.6–6.8 and 8.8–42 g C m^(-2)yr^(-1) based on N,P and Si,which were equivalent to 5.2%–27%,0.9%–3.7%and 4.7%–23%of the total primary productivity,respectively.In particular,the SFGD-derived DIN flux can be converted to primary productivity of 4.2–28 g C m^(-2)yr^(-1) thus demonstrating the disproportionately large role of SFGD in ecological environment of the Yellow Sea relative to its flux.Therefore,we conclude that SGD,particularly SFGD,plays an important role as a nutrient source for the Yellow Sea,and not only affects nutrient budgets and structures but also enhances the primary productivity.
文摘The net primary productivity of vegetation reflects the total amount of carbon fixed by plants through photosynthesis each year. The study of vegetation net primary productivity is one of the core contents of global change and terrestrial ecosystems. This article reviews the current research status of net primary productivity of terrestrial vegetation, and comprehensively analyzes the advantages and disadvantages of three types of productivity estimation models, climate relative models, biogeochemical models, and light energy utilization models. The light energy utilization models have become the mainstream method for estimating vegetation net primary productivity because they can directly use remote sensing data. However, there are still many deficiencies in the estimation of vegetation net primary productivity, which need to be further improved and tested.
基金Supported by Shanxi Province Science Foundation for Youths(201601D021115)Shanxi Province Science Foundation(201601D011063)
文摘The dynamic variation of net primary productivity of artificial Pinus tabulaeformis forest was studied in Shanxi Province,and potential productivity of artificial forest was predicted to provide reference for improving quality of regional forest stand. The regression equation was established by using the stratification and harvesting method with the relative growth model. Cumulative method and Thornthwaite Memorial model was used to estimate the actual and potential productivity of the forest. The productivity of P. tabulaeformis forest increased with the increase of age and started decrease with the mature period. The actual productivity of P. tabulaeformis forest was 4. 462 t/( ha·year); the contribution rate of trees was 72. 17% of the total productivity,and with the increase of age,the total biomass increased but productivity decreased at late near-mature forest; the contribution rate of herb layer was 21. 16% in the young forest stage,and then decreased gradually. On the contrary,the contribution rate of shrub layer increased gradually,and the contribution rate of the grassland was more than that of the herb layer,so as the key period of structural management; the average potential productivity of forest was 8. 422 t/( ha·year),and the potential space of P. tabulaeformis was at least 32% in Shanxi Province. In conclusion,the potential space of productivity of P. tabulaeformis was at least 32%,and the primary limiting factor of P. tabulaeformis forest productivity in Shanxi Province was rainfall.
基金Key Research Program of the Chinese Academy of Sciences(KZZD-EW-04)West Light Foundation of the Chinese Academy of Sciences and Funds of State Key Laboratory of Loess and Quaternary Geology,Chinese Academy of Sciences(SKLLQG1123)
文摘Vegetation net primary productivity(NPP)is a sensitive indicator to characterize the response of terrestrial ecosystems to the climate change.Projections of the NPP changes of the Loess Plateau under future climate scenarios have great significances in revealing the interactions among terrestrial ecosystems and climatic systems,as well as instructing future vegetation construction of this region.Here,we carried out a case study on the Yangou watershed in the Loess Plateau.Using the vegetation-producing process model(VPP)established for such small watersheds,we simulated the NPP of the Yangou watershed under different scenarios of climate changes.The results showed that the NPP significandy increased with the precipitation increasing and evidently decreased with the temperature increasing where the climate change occurred in the whole year or in the summer half year.However,where the climate change occurred in the winter half year,the increased precipitation had little effect on the NPP,and the increased temperature significantly reduced the NPP.There were clear differences among the response sensitivities of different vegetation types with trees and shrubs were more sensitive to the changes in temperature and precipitation than crops and grasses.Currently,the most favourable climate change scenario to the NPP in the Yangou watershed was T0P15 under which the precipitation increased by 15%and the temperature did not changed,in the whole year;in the meantime,the most unfavourable climate change scenarios was T2P-15 under which the precipitation declined by 15%and the temperature increased by 2℃,in the whole year.
文摘INTRODUCTIONThe coast zone is the area where most human activities take place and where the highest economic benefit is produced. The knowledge of the distribution and variation of primary production provides the bases as reference helping the marine exploitation and management.
文摘Net Primary Productivity (NPP) is the basis of the material and energy transport calculation in ecosystem studies. NPP directly reflects the production capacity of plant communities under natural conditions. Ecosystem services are hot topics in the field of ecology. Many studies calculate ecosystem service value based on NPP. Taking Guanshanhu District of Guiyang City, Guizhou Province as the research object, using TM, ETM<sup>+</sup>, Gaofen2 and MOD17A3HGF.006 as data sources, this paper analyzed the change of ecosystem service value based on NPP in 2000, 2010 and 2020. The results showed that the area of forest ecosystem increased during 2000-2010 and decreased during 2010-2020. The artificial surface grew rapidly from 1146.82 hm<sup>2</sup> to 7544.29 hm<sup>2</sup> during 2000-2020. The farmland ecosystem decreased from 13308.29 hm<sup>2</sup> to 6342.33 hm<sup>2</sup> during 2000-2020. With the dynamic changes in ecosystem spatial distribution and component structure, the total NPP in 2000, 2010 and 2020 was 12.58 × 10<sup>4</sup> t, 11.90 × 10<sup>4</sup> t and 11.78 × 10<sup>4</sup> t, respectively, showing a decreasing trend. The total value of natural and semi-natural ecosystems services based on NPP showed an increasing trend, which was ￥ 6.938 × 10<sup>8</sup> in 2000, ￥ 8.052 × 10<sup>8</sup> in 2010 and ￥ 10.306 × 10<sup>8</sup> in 2020 respectively. The ecosystem contributed the most to the ecological service value in 2000 was farmland, but in 2010 and 2020, it was the forest ecosystem. The ecological service value of grassland and wetland was relatively small, while the ratio of the wetland ecological service value displayed a decreasing trend. In the future, it is necessary to establish a strict pretrial system for land use, so as to effectively protect the natural and semi-natural ecosystems and fulfill the growing ecological demands of residents.
基金supported by the National Natural Science Fundation of China(No.41571175,31661143028)the special funds for basic research and operation from the Chinese Academy of Meteorological Science(2017Y003)。
文摘Background:Net primary productivity(NPP)in forests plays an important role in the global carbon cycle.However,it is not well known about the increase rate of China’s forest NPP,and there are different opinions about the key factors controlling the variability of forest NPP.Methods:This paper established a statistics-based multiple regression model to estimate forest NPP,using the observed NPP,meteorological and remote sensing data in five major forest ecosystems.The fluctuation values of NPP and environment variables were extracted to identify the key variables influencing the variation of forest NPP by correlation analysis.Results:The long-term trends and annual fluctuations of forest NPP between 2000 and 2018 were examined.The results showed a significant increase in forest NPP for all five forest ecosystems,with an average rise of 5.2 gC·m-2·year-1 over China.Over 90%of the forest area had an increasing NPP range of 0-161 gC·m-2·year-1.Forest NPP had an interannual fluctuation of 50-269 gC.m-2·year-1 for the five major forest ecosystems.The evergreen broadleaf forest had the largest fluctuation.The variability in forest NPP was caused mainly by variations in precipitation,then by temperature fluctuations.Conclusions:All five forest ecosystems in China exhibited a significant increasing NPP along with annual fluctuations evidently during 2000-2018.The variations in China’s forest NPP were controlled mainly by changes in precipitation.
基金supported by a Grant-in-Aid for Scientific Research (JSPS KAKENHI 15F15389) from the Japan Society for the promotion of Science to Professor Akira Osawa and Md.Kamruzzaman
文摘Background:The article presents the first estimates of biomass and productivity for mangrove forests along the Oligohaline zone of the Sundarbans Reserve Forest(SRF),Bangladesh.This study was conducted overone year from March 2016 to April 2017.Stand structure,above and below-ground biomass changes,and litterfall production were measured within a 2100 m^2 sample plot.Methods:All trees in the study plots were numbered and height(H) and diameter at breast height(DBH) were measured.Tree height(H) and DBH for each tree were measured in March 2016 and 2017.We apply the above and belowground biomass equation for estimating the biomass of the mangrove tree species(Chave et al.Oecologia145:87-99,2005; Komiyama et al.J Trop Ecol 21:471-477,2005).Litterfall was collected using 1-mm mesh litter traps with collection area of 0.42 m^2.Net Primary Production(NPP) was estimated by the summation method of Ogawa Primary productivity of Japanese forests:productivity of terrestrial communities,JIBP synthesis(1977) and Matsuura and Kajimoto Carbon dynamics of terrestrial ecosystem:Systems approach to global environment(2013).Results:Heritiera fomes has maintained its dominance of the stand and also suffered the highest tree mortality(2.4%) in the suppressed crown class.The total above-ground biomass(AGB) and below-ground biomass(BGB) of the studied stand was 154.8 and 84.2 Mg ha^(-1),respectively.Among the total biomass of the trees,64.8% was allocated to AGB and 35.2% to BGB.In case of species-wise contribution of biomass allocation,Avicennia officinalis showed the highest score and Aglaia cucullata the lowest.Mean annual total litterfall was 10.1 Mg ha^(-1)·yr^(-1),with the maximum litterfall in winter or dry season and late summer or rainy season.The mean AGB increment and above-ground net primary productivity(AGNPP) were 7.1 and 172 Mg·ha^(-1)·yr^(-1),respectively.Total net primary productivity(NPP) was estimated to be 21.0 Mg·ha^(-1)·yr^(-1) over the observed period.The results in the Sundarbans mangrove forests exhibited that mangrove communities with similar height and diameter produced different biomass production with the different basal area.The present analysis revealed that the root biomass was large enough and the mean ratio of above-/below-ground biomass was estimated to be 1.84.Conclusions:Mangrove communities growing at the oligohaline zone of the Sundarbans,Bangladesh showed high biomass and net primary production indicating their ecological and conservation significance that may be considered in future decision making process for the area as well as in understanding the role of Sundarbans mangrove forest on mitigating the effect of global warming.
基金The CAS“Light of West China”Program,No.2020XBZG-XBQNXZ-ACultivation Program of 2022 Major Scientific Research Project of Northwest Normal University,No.WNU-LKZD2022-04National Natural Science Foundation of Gansu,No.20JR10RA093。
文摘Current ecosystem models used to simulate global terrestrial carbon balance generally suggest that terrestrial landscapes are stable and mature,but terrestrial net primary productivity(NPP)data estimated without accounting for disturbances in species composition,environment,structure,and ecological characteristics will reduce the accuracy of the global carbon budget.Therefore,the steady-state assumption and neglect of elevation-related changes in forest NPP is a concern.The Qilian Mountains are located in continental climate zone,and vegetation is highly sensitive to climate change.We quantified aboveground biomass(AGB)and aboveground net primary productivity(ANPP)sequences at three elevations using field-collected tree rings of Picea crassifolia in Qilian Mountains of Northwest China.The results showed that(1)There were significant differences between AGB and ANPP at the three elevations,and the growth rate of AGB was the highest at the low elevation(55.99 t ha^(–1)10a^(–1)).(2)There are differences in the response relationship between the ANPP and climate factors at the three elevations,and drought stress is the main climate signal affecting the change of ANPP.(3)Under the future climate scenario,drought stress intensifies,and the predicted decline trend of ANPP at the three elevations from mid-century to the end of this century is–0.025 t ha^(–1)10a^(–1),respectively;–0.022 t ha^(–1)10a^(–1);At–0.246 t ha^(–1)10a^(–1),the level of forest productivity was significantly degraded.The results reveal the elevation gradient differences in forest productivity levels and provide key information for studying the carbon sink potential of boreal forests.
基金jointly supported by the National Key Research and Development Program of China(Grant No.2022YFE0106500)Jiangsu Science Fund for Distinguished Young Scholars(Grant No.BK20200040)。
文摘The pan-Arctic is confronted with air pollution transported from lower latitudes.Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects(DRFEs).While such DRFEs have been explored at low to middle latitudes,the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified.Here,we perform regional simulations at 0.2o×0.2ousing a well-validated vegetation model(Yale Interactive terrestrial Biosphere,YIBs)in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity(NPP)in the pan-Arctic during 2001-19.Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C(12.8%)yr^(-1)under clear-sky conditions,in which natural and anthropogenic sources contribute to 8.9% and 3.9%,respectively.Under all-sky conditions,such DRFEs are largely dampened by cloud to only 0.26 Pg C(1.24%)yr^(-1),with contributions of 0.65% by natural and 0.59% by anthropogenic species.Natural aerosols cause a positive NPP trend of 0.022% yr^(-1)following the increased fire activities in the pan-Arctic.In contrast,anthropogenic aerosols induce a negative trend of-0.01% yr^(-1)due to reduced emissions from the middle latitudes.Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter.Though affected by modeling uncertainties,this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming.
基金supported by the National Key Basic Research and Development Program of China (Grant No. G2000046801)the National Natural Science Foundation of China (Grant No. 30130060 )the A3 Foresight Program Project (NSFC)
文摘The biomass and productivity of Schima superba-Castanopsis carlesii forests in Tiantong,Zhejiang Province,were determined using overlapping quadrants and stem analyses.The total community biomass was(225.3±30.1) t hm-2,of which the aboveground parts accounted for 72.0% and the underground parts accounted for 28.0%.About 87.2% of biomass existed in the tree layer.The resprouting biomass was small,of which over 95.0% occurred in the shrub layer.The productivity of the aboveground parts of the community was(386.8±98.9) g m-2a-1,in which more than 96.0% was present at the tree level.The trunk's contribution to productivity was the greatest,while that of leaves was the smallest.In China,the community biomass of subtropical evergreen broadleaved forests differs significantly with the age of the forest.The community biomass of the 52-year-old S.superba-C.carlesii forests in this study was lower than the average biomass of subtropical evergreen broadleaved forests in China,and was lower than the biomass of other subtropical evergreen broadleaved forests elsewhere in the world.Moreover,its productivity was lower than the model estimate,indicating that without disturbance,this community has great developmental potential in terms of community biomass and productivity.
基金This work was supported primarily by the State Key Research Development Program of China(No.2016YFC0501101),(No.2016YFC0503603).
文摘Ecological restoration measures implemented in China have profoundly impacted vegetation NPP.This study aimed to estimate the effects of the land conversion and management measures on the grassland ecosystem in semi-arid regions.Land use data were employed from 2000 to 2015 to compare land conversion and coverage changes in Xilingol grassland.Then,the contributions of land conversion and management policies were quantified by assessing the difference between actual NPP and climate-induced NPP changes.The results indicated that the grassland area had a net loss of 534.42 km^(2),and the net area of increased vegetation coverage was 74,683.05 km^(2).Furthermore,the total NPP increased by 8,010.73 Gg C·yr^(−1)(1 Gg=10^(9)g),of which the human activities,including grazing management measures(+6,809.40 Gg C·yr^(−1))and land conversion(45.72 Gg C·yr^(−1))contributed to 85.58%of the increase in NPP.Transformation from desert and farmland dominated grassland expansion and NPP increase,while urbanization and desertification caused large grassland reduction and NPP loss.The grazing management increased vegetation NPP in most regions except for some regions in the desert steppe and the farming-pastoral zone.Related policies should be further adjusted to strengthen the management of the desert steppe and farming-pastoral regions.
基金the National Natural Science Foundation of China(31988102)the National Key Research and Development Program of China(2017YFC0503906)。
文摘Understanding patterns and determinants of net primary productivity(NPP)in global grasslands is ongoing challenges,especially for belowground NPP(BNPP)and its fraction(fBNPP).By developing a comprehensive field-based dataset,we revealed that,along with gradients of mean annual precipitation,actual evapotranspiration,and aridity,aboveground NPP(ANPP),BNPP,and total NPP(TNPP)exhibited hump-shaped patterns,whereas fBNPPshowed an opposite trend.ANPP and TNPP showed positive correlations with mean annual temperature,but fBNPPwas negatively correlated with it.The relationship between BNPP and climatic factors was considerably weak,indicating that BNPP was relatively stable regardless of the climate conditions.We also observed that the sensitivities of ANPP and BNPP to interannual temperature variability and those of BNPP to interannual precipitation fluctuations exhibited large variations among different study sites,and differed from those at the spatial scale.In contrast,the temporal sensitivities of ANPP to interannual precipitation variability were highly similar across all the individual sites and much smaller than those at the spatial scale.Overall,these results highlight that precipitation,temperature and evapotranspiration all play vital roles in shaping ANPP pattern and its partitioning to belowground and that the patterns of BNPP along climatic gradients do not mirror those of the ANPP.
基金Supported by the National Key Research and Development Program of China(2018YFC1506500)Natural Science Program of China(U2142212)National Natural Science Foundation of China(41871028).
文摘Currently,the satellite data used to estimate terrestrial net primary productivity(NPP)in China are predominantly from foreign satellites,and very few studies have based their estimates on data from China’s Fengyun satellites.Moreover,despite their importance,the influence of land cover types and the normalized difference vegetation index(NDVI)on NPP estimation has not been clarified.This study employs the Carnegie–Ames–Stanford approach(CASA)model to compute the fraction of absorbed photosynthetically active radiation and the maximum light use efficiency suitable for the main vegetation types in China in accordance with the finer resolution observation and monitoring-global land cover(FROM-GLC)classification product.Then,the NPP is estimated from the Fengyun-3D(FY-3D)data and compared with the Moderate Resolution Imaging Spectroradiometer(MODIS)NPP product.The FY-3D NPP is also validated with existing research results and historical field-measured NPP data.In addition,the effects of land cover types and the NDVI on NPP estimation are analyzed.The results show that the CASA model and the FY-3D satellite data estimate an average NPP of 441.2 g C m^(−2) yr^(−1) in 2019 for China’s terrestrial vegetation,while the total NPP is 3.19 Pg C yr^(−1).Compared with the MODIS NPP,the FY-3D NPP is overestimated in areas of low vegetation productivity and is underestimated in high-productivity areas.These discrepancies are largely due to the differences between the FY-3D NDVI and MODIS NDVI.Compared with historical field-measured data,the FY-3D NPP estimation results outperformed the MODIS NPP results,although the deviation between the FY-3D NPP estimate and the in-situ measurement was large and may exceed 20%at the pixel scale.The land cover types and the NDVI significantly affected the spatial distribution of NPP and accounted for NPP deviations of 17.0%and 18.1%,respectively.Additionally,the total deviation resulting from the two factors reached 29.5%.These results show that accurate NDVI products and land cover types are important prerequisites for NPP estimation.
