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Net Ecosystem Productivity (NEP) is an important measure to assess the carbon balance and dynamics of ecosystems, providing a direct measure of carbon source–sink dynamics in terrestrial ecosystems and finding widespread applications in carbon cycle research. However, the nonlinear characteristics of NEP in Xinjiang's terrestrial ecosystems remain unclear. Additionally, the influence of land use patterns, temperature, and precipitation variations on carbon sink capacity remains unclear. Ensemble Empirical Mode Decomposition (EEMD) is used to investigate the nonlinear variation of NEP in Xinjiang. Landscape pattern analysis of Xinjiang's land use patterns from 1981 to 2019 is conducted using a 30 km moving window, and the interannual relationships between NEP, land use patterns, and meteorological factors are investigated through EEMD detrending analysis and Pearson correlation. The findings indicate that: (1) NEP exhibits interannual variations, primarily concentrated in the foothills of the Tianshan Mountains, with a three-year cycle. (2) Although NEP changes in most regions are not significant, urban clusters on the northern slopes of the Tianshan Mountains show noteworthy trends, with initial decrease followed by an increase, covering around 34.87% of the total area. Areas at risk of NEP decline constitute approximately 7.32% of the total area. (3) Across Xinjiang, we observe a widespread rise in patch fragmentation and complexity, coupled with a decline in patch connectivity and the size of the dominant patch. Additionally, there is a notable increase in both the diversity and evenness of land use types. However, the correlation between land use patterns and NEP is generally found to be insignificant in the majority of areas, with a percentage exceeding 85%. (4) Approximately 62% of regions in Xinjiang have NEP that is positively correlated with temperature, with significance observed in 33% of these areas. Furthermore, almost 95% of regions demonstrate that NEP is positively correlated with precipitation, with significance noted in 83% of these regions. It appears that precipitation exerts a more pronounced influence on NEP fluctuations in Xinjiang when compared to temperature. [ABSTRACT FROM AUTHOR]

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[Objective] The spatial and temporal distribution characteristics of land use carbon sources/sinks in the Huainan mining area from 2000 to 2020 were analyzed, in order to provide a basis for Huainan City’s territorial spatial planning and future low-carbon regulation policy formulation. [Methods] The study was conducted in the Huainan mining area. Grid-scale land use data in 2000, 2010, and 2020 were used to quantify the spatial and temporal patterns of carbon sources/sinks/emissions under different stages of land use change development. The spatial patterns of carbon sources/sinks/emissions were determined based on coldspots and hotspots. [Results] ① From 2000 to 2020, the land use type shifted from a single land use type to multiple land use types at the same time. The area of construction land increased, leading to an enhanced carbon source effect, a relatively weaker carbon sink effect, and a continuous increase in carbon emissions, with an annual increase in carbon sources of 2.76×106 t, an annual increase in carbon sinks of only 130 t, and an annual increase in carbon emissions of 2.76×106 t. ② The spatial distribution characteristics of carbon sources and emissions were basically the same, with the central built-up area and the northwest mining area being the main concentration areas of carbon sources and emissions. Carbon sinks were mainly concentrated in the eastern and western fringe areas and the western mining area. ③ The central built-up area of the study area was a significant hotspot area for carbon sources and emissions, dominated by significant hotspot change characteristics. Significant coldspots were mainly located in the eastern and western marginal areas of the study area and in the northwest part of the mining area. [Conclusion] Greater attention should be given to the carbon emission reduction and low carbon effect of the Huainan mining area in the large plain area of farm land in the north, as well as to controlling the mining of coal resources, to the development of construction land, and to rapid restoration of subsidized water areas. With the rapid increase of urbanization in Southern China, the area of productive carbon absorption capacity from forest land and grassland should be moderately increased to avoid unlimited expansion of construction land.

Aims: Coastal salt marshes are productive ecosystems that are highly efficient carbon sinks, but there is uncertainty regarding the interactions among climate warming, plant species, and tidal restriction on C cycling. Methods: Open-top chambers (OTCs) were deployed at two coastal wetlands in Yancheng, China, where native Phragmites australis (Phragmites) and invasive Spartina alterniflora (Spartina) were dominant, respectively. Two study locations were set up in each area based on difference in tidal action. The OTCs achieved an increase of average daytime air temperature of ~ 1.11–1.55 °C. Net ecosystem CO2 exchange (NEE), ecosystem respiration (Reco), CH4 fluxes, aboveground biomass and other abiotic factors were monitored over three years. Results: Warming reduced the magnitude of the radiative balance of native Phragmites, which was determined to still be a consistent C sink. In contrast, warming or tidal flooding presumably transform the Spartina into a weak C source, because either warming-induced high salinity reduced the magnitude of NEE by 19% or flooding increased CH4 emissions by 789%. Remarkably, native Phragmites affected by tidal restrictions appeared to be a consistent C source with the radiative balance of 7.11–9.64 kg CO2-eq m–2 yr–1 because of a reduction in the magnitude of NEE and increase of CH4 fluxes. Conclusions: Tidal restrictions that disconnect the tidal hydrologic connection between the ocean and land may transform coastal wetlands from C sinks to C sources. This transformation may potentially be an even greater threat to coastal carbon sequestration than climate warming or invasive plant species in isolation. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The differences in CO2 equivalent emissions and carbon compensation due to land use changes can provide a basis for formulating low-carbon development policies in various regions according to net CO2 emissions. Based on the land use and energy consumption data of Hunan Province from 2000 to 2020, the calculation model is constructed to calculate the CO2 equivalent emissions and carbon compensation values for different cities in different periods. The results showed that: (1) From 2000 to 2020, there was a significant growth trend in the area of built-up land in Hunan Province, mainly from the forest and cropland, while the area of forest is relatively stable. (2) The net CO2 equivalent emissions from land use changes in Hunan Province shows a trend of increasing first and then decreasing with an initially fast and then slowed growth rate. Built-up land is the main carbon source, and its CO2 equivalent emissions increased by 26.78 million tons, while the forest is the main carbon sink, and its carbon absorption decreased by 4.11 × 104 tons. (3) The carbon sink areas are mainly located in Zhangjiajie and Xiangxi in western Hunan, and the CO2 equivalent emission intensity of other carbon source areas is gradually increasing from eastern Hunan to southern Hunan. (4) The carbon compensation value is very similar to the spatial distribution of CO2 equivalent emissions in different cities. The high carbon compensation areas are mainly Yueyang, Loudi, and Xiangtan due to their backward energy structure, un-upgraded industrial structure, and large net CO2 equivalent emissions, while the high carbon compensation areas are mainly Changsha, due to its high economic development level, great technological progress, and small net CO2 equivalent emissions. To achieve regional coordination and low-carbon development, it is necessary to continually improve the carbon compensation mechanism and to build on carbon compensation to promote regional low-carbon coordinated development from a low-carbon level. Meanwhile, the government should rank and direct the transformation and development of different types of cities, to build a low-carbon land development model and achieve the goal of developing carbon neutrality. [ABSTRACT FROM AUTHOR]

Net ecosystem productivity ( NEP) represents the carbon sequestration capacity of a regional ecosystem. Based on the Google Earth Engine ( GEE) platform, this study analyzed the temporal and spatial variations in the NEP of the Three - River Headwaters Region ( TRHR) from 2001 to 2020 based on the Moderate Resolution Imaging Spectrometer ( MODIS) and meteorological data and revealed their relationships with climate factors. The results are as follows; 1 The TRHR had an important carbon sink function, with carbon sink areas accounting for 99. 89% ; The carbon source areas in the TRHR were primarily distributed in the northwest, accounting for only 0. 11%. The NEP of the TRHR decreased gradually from the southeast to the northwest and differed significantly among different ecological areas; 2 The NEP of the TRHR showed an upward trend overaU in the past 20 years, with an annual increasing rate of 1. 13 gC/(m ² • a), indicating huge carbon sequestration potential; 3 The area of zones whose NEP showed an upward trend accounted for 95. 05% of the total area. Ecological engineering construction significantly improved the NEP of vegetation. As a result, the carbon sink function gradually increased and was highly stable; 4 The TRHR had an annual average NEP of 120. 93 gC/( m ² • a), and the NEP was positively correlated with the annual precipitation but negatively correlated with average annual temperature and annual solar radiation. The warm, humid climate and the ecological engineering construction contributed to the carbon sink function of vegetation in the TRHR. This is of great significance for improving the carbon sink value of the terrestrial ecosystem and achieving the peak carbon dioxide emissions and carbon neutrality of China. [ABSTRACT FROM AUTHOR]

Net ecosystem productivity (NEP) refers to the portion of net primary productivity (NPP) that is available for carbon cycling in terrestrial ecosystems after subtracting photosynthetic carbon consumed by heterotrophic respiration. The amount of the NEP reflects the size of carbon sinks/sources in terrestrial ecosystems, holding great significance for the research of climate change and global carbon cycle. In this study, the NEP of the Zoige grassland wetland ecological function zone (ZGW) on the eastern slope of the Tibetan Plateau from 2001 to 2020 is estimated by using the improved Carnegie-Ames-Stanford Approach model for NPP and a statistical model for soil heterotrophic respiration, based on the meteorological data, vegetation data and socioeconomic data. Additionally, the spatio-temporal variations of the NEP are analyzed, and the influences of natural factors and anthropogenic activities on the NEP are investigated. The results indicate that the ZGW overall plays a role as a carbon sink, and the carbon sink area accounts for approximately 99.3% of the whole ZGW. The annual average NEP in the study area is 447.9 g·m ^−2 , showing a gradual increase at a rate of 5.0 g·m ^−2 ·a ^−1 , although the increasing trend is not significant. The carbon sink capacity increased in 93.5% of the ZGW, remained relatively stable in 5.9% of the ZGW, and decreased and significantly decreased in 0.6% of the ZGW. Climate warming and humidifying promote the enhancement of carbon sink capacity in the ecosystem of the ZGW, and precipitation is the dominant climatic factor influencing NEP variations. Natural factors are the determinants of NEP variations, while anthropogenic activities play a secondary role. The implementation of ecological restoration and management projects in the areas along the Yellow River, around the main roads and the core area of wetlands, as well as the continuation of green and coordinated development policies of orderly developing grassland resources, is conducive to enhancing vegetation carbon sink capacity of the ZGW.

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Land use changes are thought to deeply impact the changes of terrestrial carbon sink, however, how the changes of land use pattern affect the carbon sink remains unclear. To investigate the response of Net Ecosystem Productivity (NEP) to the pattern of land use dynamics in China, a landscape pattern approach (with the 30 km moving window) was used to analyze the pattern dynamics with continuous Land Use and Land Cover Change (LUCC) data from 1981 to 2019 and the nonlinear trends of the NEP and the patterns of land use were explored from 1981 to 2019 using Ensemble empirical modal decomposition (EEMD) methods, and their interannual relationship was further explored using Pearson correlation. The results are as follows: (1) For NEP, nearly half of the regions did not experience significant changes. 90 %) have experienced significant changes in land use patterns, the fragmentation and shape complexity, diversity and evenness of land use types has increased, while the connection decreased, meanwhile, most of these changes are not monotonical, but experiencing trend shifts; (3) In most of the total area (>80 %), land use patterns showed insignificant relationship with NEP, especially in Qinghai-Tibetan Plateau. However, in Greater Khingan Range, Loess Plateau and southern Hilly area, it showed significant relationship with NEP. Our studies highlight the importance of nonlinear analysis for fully understanding the spatial–temporal changes of NEP and land use patterns, and deepened the understanding the impacts of land use changes on NEP.

Copyright of Journal of Ecology & Rural Environment is the property of Journal of Ecology & Rural Environment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the past several decades, the carbon budget in the dryland ecosystem has experienced great variation under the joint impact of climate change and anthropogenic interference. How the net ecosystem productivity (NEP) responds to climate change and human interference in the Qilian Mountains (QLM), Northwest China, remains unclear. To fill these gaps, we first estimated the NEP in the QLM and then quantified the independent and interactive influences of natural environment factors, climatic factors, and human activity intensity on the NEP change from 2000 to 2020 by linking the Geodetector and structural equation models. The NEP of the QLM showed a significant increase during the recent 20 years, and 78.93% of the QLM experienced a significant increase in NEP; while only 4.83% of the area in the QLM experienced a decreasing trend, which is dominantly located on the southeast edge, surrounding the Qinghai Lake, and the midland of the QLM. The area percentage of the carbon sink region increased from 47% in 2000 to 62% in 2020. The natural environment factors (e.g., altitude and soil type) and climate factors (e.g., temperature and precipitation) were the dominant factors that determine the spatial distribution of NEP. Compared with a single factor, the interaction of pairs of factors enhanced the influence strength on NEP. The natural environment factors indirectly affected NEP change through influencing human activities intensity and climatic factors. Human activities intensity played a medium indirectly negative effect on NEP, while climatic factors exerted strong direct and indirect positive influences on NEP. The contributions of human activity intensity, climatic factors, and natural environment on NEP change in the QLM were 33.5%, 62.3%, and 38.3%, respectively. Overall, warming and wetting shifts in meteorological conditions offset the negative impact of human activities on NEP in the QLM, and the QLM has acted as a growing carbon sink in the past 20 years. [ABSTRACT FROM AUTHOR]

To quantify the carbon source/sink function of riparian zone swamps and explore the feedback relationship with climate change, we measured the annual fluxes of soil greenhouse gas, soil carbon emission, net vegetation carbon sequestration and related environmental factors (temperature, water level, etc .) by static chamber-gas chromatography and relative growth equation methods in three kinds of forest swamps ( Alnus sibirica swamp, Betula platyphylla swamp, and Larix olgensis swamp) distributed along the water reduction gradient of lowland to highland in the stream riparian zone of Changbai Mountains. The results showed that the annual fluxes of CH 4 (0.19-0.85 mg·m -2 ·h -1 ), CO 2 (60.81-228.63 mg·m -2 ·h -1 ), and N 2 O (-0.02-0.05 mg·m -2 ·h -1 ) showed spatial variations along the water gradient of lowland to highland, with a trend of first constant then decreasing, decreasing, and first absorption then emission, respectively. The spatial variations of annual fluxes of these greenhouse gases were controlled by water levels. The annual net carbon sequestration of vegetation (2.61-3.45 t C·hm -2 ·a -1 ) was constant along the water gradient, which was mainly promoted by nitrate nitrogen content. The carbon source/sink and global warming potential (GWP) undergo regular changes along water gradients. The A. sibirica swamp was a carbon sink (1.93 t C·hm -2 ·a -1 ), the B. platyphylla swamp was a weak carbon source (-0.18 t C·hm -2 ·a -1 ), and the L. olgensis swamp was a strong carbon source (-2.51 t C·hm -2 ·a -1 ). The spatial variation of carbon source/sink in forest swamps was jointly promoted by water level and nitrate nitrogen content. A. sibirica swamp exhibited a strong cooling effect with a strong negative feedback effect on climate change (-5.88 t CO 2 ·hm -2 ·a -1 ). L. olgensis swamp exhibited a strong warming effect with a strong positive feedback effect (10.97 t CO 2 ·hm -2 ·a -1 ). B. platyphylla swamp exhibited a weak warming effect, approximately neutral (2.95 t CO 2 ·hm -2 ·a -1 ). The spatial variation of GWP in forest swamps was mainly inhibited by water level.

Soil microbial biomass regulates plant litter decomposition and provides a sensitive measure of change in organic matter status. Reconstruction of low-function forest by inter-planting broadleaved trees change the composition of plant community, but how this change would affect microbial biomass and soil carbon and nitrogen pools are unclear. We reconstructed low-function forests by inter-planting broadleaved trees under Pinas massoniana which is the typical coniferous and low-function forest in China. The treatments included P. massoniana pure forest (PM). P. massoniana inter-planted with Schima superba (PMSS) and Liquidambar for-mosana (PMLF). respectively. The results showed that soil microbial biomass carbon and organic matter in PMSS were significantly lower than that in PM. However, soil soluble carbon contents in PMSS was higher than that in PM. These results indicate that the reconstruction mode of PMSS accelerate decomposition of soil organic matter. There was no obvious change of soil microbial biomass between PMLF and PM. Both soil organic matter and soluble carbon in PMLF were higher than that in PM. suggesting that the reconstruction mode of PMLF facilitate soil organic carbon accumulation as carbon sink. [ABSTRACT FROM AUTHOR]

Wetland ecosystems play an important role in regulating the Earth's climate. This paper presents the results of a study on the alpine wetland ecosystem CO fluxes at the Qinghai Lake at different vegetative development stages and CO controlling factors measured by eddy covariance system. The results showed that the alpine wetland ecosystem at the Qinghai Lake area was a carbon sink on the whole year basis. The average net ecosystem CO exchange (NEE) amount was −904.42 g CO/m; the average amount of the ecosystem reparation (Re) was 1450 g CO/m; the average gross primary productivity (GPP) was 2354.42 g CO/m from July 2011 to June 2013 year. The NEE, Re and GPP amounts were the maximum during the growing stage of the whole year. There were significant negative linear correlations between monthly NEE amount and monthly average total solar radiation (SR) ( R = 0.27, p < 0.05), incident photosynthetically active radiation (PAR) ( R = 0.28, p < 0.05), ambient vapor pressure deficit (VPD) ( R = 0.38, p < 0.01), monthly total precipitation ( P) ( R = 0.65, p < 0.0001), monthly mean leaf area index (LAI) ( R = 0.85, p < 0.0001) and enhanced vegetation index (EVI) ( R = 0.84, p < 0.0001). Extreme significant polynomial nonlinear negative correlations were found between NEE amounts and monthly average air temperature ( T ) ( R = 0.84, p < 0.0001), soil temperature at 0-5 cm depth ( T ) ( R = 0.90, p < 0.0001) and air relative humidity (RH) ( R = 0.76, p < 0.0001). The monthly Re amount of alpine wetland ecosystem at the Qinghai Lake at different stages showed significant nonlinear positive correlations with all the identified affecting factors except for monthly mean EVI, which showed a linear relationship ( R = 0.72, p < 0.0001). The monthly GPP amount at different vegetative development stages showed a significant exponential correlation with monthly average T ( R = 0.92, p < 0.0001), a power function with VPD ( R = 0.24, p < 0.05), quadratic polynomial ones with monthly average T ( R = 0.93, p < 0.0001), RH ( R = 0.74, p < 0.0001) and monthly P ( R = 0.55, p < 0.05). Extremely significant linear correlations of the monthly GPP amount at different developing stages with monthly average LAI ( R = 0.85, p < 0.0001) and EVI ( R = 0.92, p < 0.0001) were also found. [ABSTRACT FROM AUTHOR]

Lacustrine wetlands have long-term carbon storage capacity and contribute significantly to regional carbon cycle, but it is unclear how its carbon sinks respond to climate change. We measured soil heterotrophic respiration carbon emissions (CO 2 and CH 4 ), vegetation carbon sequestration, and related environmental factors (temperature, water level, etc .) of five kinds of natural swamps ( Phragmites marsh-L, Carex schmidtii marsh-C, Rhododendron capitatum swamp-D, Betula fruticose swamp-H, Larix olgensis swamp-LT)by using static chamber gas chromatography and relative growth equation methods, along the water environmental gradients from lakeside to highlands in Yuanchi of Changbai Mountains. We quantified the carbon source/sink function (CSS) and global warming potential (GWP) of various swamp types by estimating ecosystem net carbon balance, and revealed the variation patterns and formation mechanisms of CSS and GWP along the environmental gradients, aiming to explore the response of carbon source/sink of lakeside wetland in high altitude area to climate change. The results showed that marshes (L and C) were weak sources (-1.018 and -0.090 t C·hm -1 ·a -1 ) at the lower habitats of the water environment gradient, shrub swamps (D and H) were strong or weak sinks (1.956 and 0.239 t C·hm -1 ·a -1 ) at the middle habitats, forest swamp (LT) was strong source (-3.214 t C·hm -1 ·a -1 ) at the upper habitat. The spatial changes were promoted by water level and suppressed by soil temperature. For GWP, strong thermal radiation for marshes (from 44.682 to 59.282 t CO 2 ·hm -1 ·a -1 ), cold radiation for shrub swamps (from -0.920 to -7.008 t CO 2 ·hm -1 ·a -1 ), and weak thermal radiation for forest swamp (11.668 t CO 2 ·hm -1 ·a -1 ), and their GWP was only promoted by soil temperature. Under current climate change background, marshes and forest swamp at both ends of the water environment gradient from lakeside to highlands played a positive feedback effect due to the increases of CH 4 or CO 2 emissions, while the middle shrub swamp still maintained a negative feedback effect in Yuanchi located the high-altitude area of the temperate Changbai Mountains.

The seasonal evolution of dissolved inorganic carbon (DIC) and CO2 air-sea fluxes in the Jiaozhou Bay was investigated by means of a data set from four cruises covering a seasonal cycle during 2003 and 2004. The results revealed that DIC had no obvious seasonal variation, with an average concentration of 2035 µmol kg-1 C in surface water. However, the sea surface partial pressure of CO2 changed with the season. pCO2 was 695 µatm in July and 317 µatm in February. Using the gas exchange coefficient calculated with Wanninkhof’s model, it was concluded that the Jiaozhou Bay was a source of atmospheric CO2 in spring, summer, and autumn, whereas it was a sink in winter. The Jiaozhou Bay released 2.60 x 1011 mmol C to the atmosphere in spring, 6.18 x 1011 mmol C in summer, and 3.01 x 1011 mmol C in autumn, whereas it absorbed 5.32 x 1010 mmol C from the atmosphere in winter. A total of 1.13 x 1012 mmol C was released to the atmosphere over one year. The behaviour as a carbon source/sink obviously varied in the different regions of the Jiaozhou Bay. In February, the inner bay was a carbon sink, while the bay mouth and the outer bay were carbon sources. In June and July, the inner and outer bay were carbon sources, but the strength was different, increasing from the inner to the outer bay. In November, the inner bay was a carbon source, but the bay mouth was a carbon sink. The outer bay was a weaker CO2 source. These changes are controlled by many factors, the most important being temperature and phytoplankton. Water temperature in particular was the main factor controlling the carbon dioxide system and the behaviour of the Jiaozhou Bay as a carbon source/sink. The Jiaozhou Bay is a carbon dioxide source when the water temperature is higher than 6.6°C. Otherwise, it is a carbon sink. Phytoplankton is another controlling factor that may play an important role in behaviour as a carbon source or sink in regions where the source or sink nature is weaker.

Tibetan Plateau (TP) is the highest and most extensive plateau in the world and has been known as the roof of the world, and it is sensitive to climate change. The researches of CO fluxes ( F) in the TP region play a significant role in understanding regional and global carbon balance and climate change. Eddy covariance flux measurements were conducted at three sites of south-eastern TP comprising Dali (DL, cropland ecosystem), LinZhi (LZ, alpine meadow ecosystem) and Wenjiang (WJ, cropland ecosystem); amongst those DL and LZ are located in plateau region, while WJ is in plain region. Dynamics of F and influences of vegetation, meteorological (air temperature, photosynthetically active radiation, soil temperature and soil water content) and terrain factors (altitude) were analysed on the basis of data taken during 2008. The results showed that, in the cool sub-season (March, April, October and December), carbon sink appeared even in December with fluxes of (−0.021 to −0.05) mg CO m s and carbon source only in October (0.03 ± 0.0048) mg CO m s in DL and WJ site. In LZ site, carbon sink was observed in April: (−0.036 ± 0.0023) mg COm s and carbon sources in December and March (0.008-0.010 mg CO m s). In the hot sub-season (May-August), carbon source was observed only in May with (0.011 ± 0.0022), (0.104 ± 0.0029) and (0.036 ± 0.0017) fluxes in LZ, DL and WJ site, respectively, while carbon sinks with (−0.021 ± 0.0041), (−0.213 ± 0.0007) and (−0.110 ± 0.0015) mg CO m s fluxes in LZ, DL, and WJ, respectively. Comparing with plain region (WJ), carbon sinks in plateau region (DL and LZ) lasted for a longer time, and the absorption sum was large and up to (-357.718 ± 0.0054) and (−371.111 ± 0.0039) g C m year, respectively. The LZ site had the weakest carbon sink with (−178.547 ± 0.0070) g C myear. Multivariate analysis of covariance showed that altitude ( AL) as an independent factor explained 39.5 % of F ( P < 0.026). F had a quadratic relationship with Normalized difference vegetation index (NDVI) ( R ranges from 0.485 to 0.640 for three sites ), an exponential relationship with soil temperature at 5-cm depth ( ST) at night time and a quadratic relationship with air temperature ( T) at day time. Path analysis indicated that photosynthetically active radiation ( PAR), sensible heat fluxes ( H) and other factors all had direct or indirect effects on F in all of the three tested sites around the south-eastern TP. [ABSTRACT FROM AUTHOR]

Abstract: Changes of land-use policy and herdsmen settlement in mid-1980s have significantly altered the diversity of vegetations in aid grazing ecosystems. To examine the spatial dynamics of vegetation species and the changes of carbon source/sink, ecological survey, accompanied with 3S technology, had been applied in this study. A total of 1169 vegetation samples were collected along two 5km transects, along with topographic and demographic variables (slope, aspects, population, distance from the center of new herd farms). Analysis of this dataset revealed that more than 1/3 of the lands were in serious degradation with dominant unpalatable plant community. The increase in the abundance of inedible plant Peganum harmala in sunny slope near the farm and some annual unpalatable species in the lower land indicated serious degradation of grassland. The roads, the heavily used patches, impacted plant cover greatly, a decrease of 24.8% comparing to adjacent patches. This field experiment demonstrated that there were significant relationships between plant cover and two driving factors; slope degree and distances from the new farm center; on the other side, the results of spatial data analysis provided basis for improving the grassland carbon balance condition. In general, plant cover declined with increases in slope and decreases in the distance. [Copyright &y& Elsevier]

Abstract: With the deepening research of global change, studies of carbon cycle of grassland ecosystem, one of the widely distributed vegetation type, is of great significance in estimating global carbon cycle. Grassland degradation and desertification caused by human activities(such as land reclamation and grazing etc) is becoming increasingly serious in our country, so it is urgency to study the effects of human on grassland soil carbon. Under the condition of increasing measuring precision and region density, it is superior to use remote sensing in grassland carbon storage measurement through acquisition and inversion vegetation information and related biophysics parameters, it is possible to monitor the space distribution of grassland carbon-fixed amount in large range and multi-scale timely and accurately. In this paper, the importance of carbon cycle of grassland ecosystem was discussed, and researches on carbon cycle of grassland ecosystem in China was summarized and analysed, including the three carbon pools(plants carbon pool, litterfall carbon pool and soil carbon pool), effects of natural or human activities on carbon storage and methods to estimate the carbon storage. Additionally, based on the principal of grass growth, together with analysis of various global ecosystem NPP estimation methods, we put forward a novel thought to establish an carbon estimation model and testify its accuracy with meteorological data and field observation data such as grassland biomass, NPP, net ecological productivity (NEP) etc, which is much more suitable for carbon source/sink estimation of grassland ecosystem in China. At last, the existing problems and prospects of carbon source/sink researches of main grassland in China were discussed. [Copyright &y& Elsevier]