Evaluation and mapping of relative sensitivity of the terrestrial ecosystems to acidic deposition in Fujian

Based on the semi-quantitative approach, four environmental factors of sites (i.e. bedrock lithology, soil type, land use, and rainfall) were categorized, weighted and combined to determine and assess the relative sensitivity of the terrestrial ecosystems to acidic deposition in Fujian Province. Then the factors have been digitized and combined to assign an overall value for each mesh square (16.77 km×18.39 km) by using the geographic information system (GIS) The results indicated that the most sensitive area in Fujian was mainly located in the southeast, and the least: ensitive area was distributed sporadically in the east along the coast. Due to slow weathering rate of siliceous rocks, acid to weakly acid reactions of the soils, along with the greater percent of coniferous forests, more than 80 percent of the total area exhibits higher sensitivity classes (4–7).

Risk Assessment of Carbon Sequestration for Terrestrial Ecosystems in China

Climate change will alter the capacity of carbon sequestration,and the risk assessment of carbon sequestration for terrestrial ecosystems will be helpful to the decision-making for climate change countermeasures and international climate negotiations.Based on the net ecosystem productivity of terrestrial ecosystems simulated by Atmosphere Vegetation Integrated Model,each grid of the risk criterion was set by time series trend analysis.Then the risks of carbon sequestration of terrestrial ecosystems were investigated.The results show that,in the IPCCSRES-B2 climate scenario,climate change will bring risks of carbon sequestration,and the high-risk level will dominate terrestrial ecosystems.The risk would expand with the increase of warming degree.By the end of the long-term of this century,about 60% of the whole country will face the risk;Northwest China,mountainous areas in Northeast China,middle and lower reaches plain of Yangtze River areas,Southwest China and Southeast China tend to be extremely vulnerable.Risk levels in most regions are likely to grow with the increase of warming degree,and this increase will mainly occur during the near-term to mid-term.Northwest China will become an area of high risks,and deciduous coniferous forests,temperate mixed forests and desert grassland tend to be extremely vulnerable.

Spatial-temporal patterns and evolution of carbon storage in China's terrestrial ecosystems from 1980 to 2020

Analyzing the changes in carbon storage in terrestrial ecosystems caused by land use changes is a crucial part of exploring the carbon cycle. In addition, enhancing carbon storage in terrestrial ecosystems is an effective and environmentally friendly measure to sequester anthropogenic carbon emissions, which is significant for achieving carbon neutrality and curbing global climate change. This paper uses land use data and carbon density tables with the In VEST model to obtain a carbon storage distribution map of China. It further applies land use response elasticity coefficients, Theil index multi-stage nested decomposition, and spatial autocorrelation analysis to examine the spatial-temporal patterns, causes of changes, and evolution characteristics of carbon storage in terrestrial ecosystems from 1980 to 2020. The results show that the temporal changes in China's carbon storage generally present an inverted S-curve, with an initial rapid decline followed by a slower decrease. Spatially, it features high levels in the northeast, low levels in the northwest, and a uniform distribution in the central and southern regions.The disturbance of land use type changes on terrestrial ecosystem carbon storage has been effectively mitigated. The significant reduction in grassland area in the Southwest region is the main source of carbon storage loss during the study period, and the encroachment of construction land on arable land in large urban agglomerations is one of the important causes of carbon storage loss. The Theil index multi-stage nested decomposition results indicate that the overall difference in carbon storage in China has decreased, while differences among cities within provinces and among counties within cities have increased. The influence of natural factors on the distribution of carbon storage is weakening, whereas the impact of human activities is becoming more profound, enhancing its influence on the spatial distribution of carbon storage in China. From 1980 to 2000, the carbon density in coastal metropolises generally showed a declining trend. From 2000 to 2020, the carbon density in the central urban areas of eastern coastal city clusters gradually showed an upward trend and continued to expand outward, revealing to some extent the“Environmental Kuznets Curve” characteristic in the development process of urban carbon storage. Therefore, in future ecological construction, the government should fully consider the impact of land management planning on carbon storage in different regions, promote the efficient use and standardized management of land, and strive to cross the “Environmental Kuznets Curve” inflection point of carbon storage as soon as possible.

Dimethylsulfoniopropionate (DMSP) Increases Longevity and Mitochondrial Function in Caenorhabditis elegans: Implications for the Role of the Global Sulfur Cycle in Terrestrial Ecosystems

Dimethylsulfoniopropionate(DMSP)is a compound synthesized by marine phytoplankton that contributes to the oceanic sulfur cycle.Interestingly,DMSP has also been found in algal species and several terrestrial plants,forming part of the global sulfur cycle.However,compared to its role in the marine environment,the impact of DMSP on terrestrial ecosystems remains relatively unexplored.In this study,DMSP was shown to promote longevity and prevent age-associated functional decline in Caenorhabditis elegans(C.elegans),a soil-dwelling organism.DMSP decreased mitochondrial content and improved mitochondrial function in C.elegans at the old stage,which was via enhancing autophagy flux.It was demonstrated that DMSP significantly increased the expression of autophagy and mitophagy genes during aging.Furthermore,DMSP protected against Parkinson’s disease(PD)induced byα-synuclein(α-syn)aggregation via autophagy.Mechanistic studies showed that DMSP directly activated nuclear translocation of the Skinhead-1(SKN-1)transcription factor from the cytoplasm.Moreover,SKN-1 was involved in DMSP-induced autophagy and played a key role in lifespan extension andα-syn clearance in C.elegans.In conclusion,DMSP delays physiological aspects of aging in C.elegans,providing insights into the interplay between the global sulfur cycle and terrestrial organisms.

Current scenario and challenges of plastic pollution in Bangladesh:a focus on farmlands and terrestrial ecosystems

Plastic is considered one of the most indispensable commodities in our daily life.At the end of life,the huge ever-growing pile of plastic waste(PW)causes serious concerns for our environment,including agricultural farmlands,groundwater quality,marine and land ecosystems,food toxicity and human health hazards.Lack of proper infrastructure,financial backup,and technological advancement turn this hazardous waste plastic management into a serious threat to developing countries,especially for Bangladesh.A comprehensive review of PW generation and its consequences on environment in both global and Bangladesh contexts is presented.The dispersion routes of PW from different sources in different forms(microplastic,macroplastic,nanoplastic)and its adverse effect on agriculture,marine life and terrestrial ecosystems are illustrated in this work.The key challenges to mitigate PW pollution and tackle down the climate change issue is discussed in this work.Moreover,way forward toward the design and implementation of proper PW management strategies are highlighted in this study.

The phytolith carbon sequestration in terrestrial ecosystems:the underestimated potential of bamboo forest

Background Terrestrial ecosystems contain significant carbon storage,vital to the global carbon cycle and climate change.Alterations in human production activities and environmental factors affect the stability of carbon storage in soil.Carbon sequestration in plant phytoliths offers a sustainable method for long-term carbon stabilization.Carbon occluded in phytoliths(PhytOC)is a kind of carbon that can be stable and not decomposed for a long time,so it is crucial to conduct more in-depth research on it.Results We undertook a meta-analysis on PhytOC across global terrestrial ecosystems,analyzing 60 articles,encapsulating 534 observations.We observed notable differences in phytolith and PhytOC contents across various ecosystems.Bamboo forest ecosystems exhibited the highest vegetation phytolith and PhytOC content,while soil phytolith content was most prominent in bamboo forests and PhytOC content in croplands.Human activities,such as grassland grazing,had a lesser impact on soil PhytOC transport than actions like cutting and tillage in croplands and forests.Our study separated bamboo ecosystems,analyzing their PhytOC content and revealing an underestimation of their carbon sink capacity.Conclusions Notwithstanding our findings,phytoliths’intricate environmental interactions warrant further exploration,crucial for refining ecosystem management and accurately estimating PhytOC stocks.This deepened understanding lays the foundation for studying phytoliths and the carbon sink dynamics.

Rates of litter decomposition in terrestrial ecosystems:global patterns and controlling factors

Aims We aim to construct a comprehensive global database of litter decomposition rate(k value)estimated by surface floor litterbags,and investigate the direct and indirect effects of impact factors such as geographic factors(latitude and altitude),climatic factors(mean annual tempePlrature,MAT;mean annual precipitation,MAP)and litter quality factors(the contents of N,P,K,Ca,Mg and C:N ratio,lignin:N ratio)on litter decomposition.Methods We compiled a large data set of litter decomposition rates(k values)from 110 research sites and conducted simple,multiple regression and path analyses to explore the relationship between the k values and impact factors at the global scale.Important findings The k values tended to decrease with latitude(LAT)and lignin content(LIGN)of litter but increased with temperature,precipitation and nutrient concentrations at the large spatial scale.Single factor such as climate,litter quality and geographic variable could not explain litter decomposition rates well.However,the combination of total nutrient(TN)elements and C:N accounted for 70.2%of the variation in the litter decomposition rates.The combination of LAT,MAT,C:N and TN accounted for 87.54%of the variation in the litter decomposition rates.These results indicate that litter quality is the most important direct regulator of litter decomposition at the global scale.This data synthesis revealed significant relationships between litter decomposition rates and the combination of climatic factor(MAT)and litter quality(C:N,TN).The global-scale empirical relationships developed here are useful for a better understanding and modeling of the effects of litter quality and climatic factors on litter decomposition rates.

Greenhouse gas budget for terrestrial ecosystems in China

Terrestrial ecosystems may act as a source or a sink for the atmospheric greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), depending on land use and management. This paper reviews the literature on carbon, CH4, and N2O fluxes from terrestrial ecosystems in China, and analyzes its national greenhouse gas budget. Carbon storage in biomass and soils in Chinese terrestrial ecosystems decreased in the past 300 years, due to deforestation and expansion of cultivated land, and reached a minimum in the late 1970s. Since then, carbon storage has increased at an estimated rate of 0.19 to 0.26 Pg C yr-1, mainly owing to reforestation and afforestation. CH4 emission from natural wetlands decreased from 6.65 Tg CH4 yr-1 in 1990 to 5.71 Tg CH4 yr-1 in 2000 owing to the decrease in wetland area. CH4 emission from flooded rice fields was 7.41 Tg CH4 yr-1. At the same time, aerobic soils took up atmospheric CH4 at a rate of 2.56 Tg CH4 yr-1. Nitrous oxide emission from forestlands, grasslands, and farmlands was positively correlated with precipitation at a national scale, and the emission rate was positively correlated with the CH4 uptake rate of forestlands and grasslands (P<0.01). Natural N2O sources were estimated to be 419 Gg N yr-1 and anthropogenic sources (from farmlands) to be 292 to 476.3 Gg N yr-1, with a mean of 372.6 Gg N yr-1. The integrated budget of greenhouse gasses indicates that Chinese terrestrial ecosystems act as a small net sink for global warming potential (GWP), ranging from 0.04 to 0.32 Pg CO2-eq yr-1, in a striking contrast to terrestrial ecosystems globally, which are a source of 2.75 to 6.78 Pg CO2-eq yr-1. The ratios of anthropogenic to natural sources of CH4 and N2O are much larger in Chinese terrestrial ecosystems than they are in global averages, reflecting greater human disturbance of terrestrial ecosystems in China.

Changes in soil organic carbon of terrestrial ecosystems in China:A mini-review

The present study provides an overview of existing literature on changes in soil organic carbon(SOC) of various terrestrial ecosystems in China.Datasets from the literature suggest that SOC stocks in forest,grassland,shrubland and cropland increased between the early 1980s and the early 2000s,amounting to(71±19) Tg·a-1.Conversion of marshland to cropland in the Sanjiang Plain of northeast China resulted in SOC loss of(6±2) Tg·a-1 during the same period.Nevertheless,large uncertainties exist in these estimates,especially for the SOC changes in the forest,shrubland and grassland.To reduce uncertainty,we suggest that future research should focus on:(i) identifying land use changes throughout China with high spatiotemporal resolution,and measuring the SOC loss and sequestration due to land use change;(ii) estimating the changes in SOC of shrubland and non-forest trees(i.e.,cash,shelter and landscape trees);(iii) quantifying the impacts of grassland management on the SOC pool;(iv) evaluating carbon changes in deep soil layers;(v) projecting SOC sequestration potential;and(vi) developing carbon budget models for better estimating the changes in SOC of terrestrial ecosystems in China.

Perspectives on the role of terrestrial ecosystems in the ‘carbon neutrality' strategy

The Chinese government has made a strategic decision to reach ‘carbon neutrality' before 2060. China's terrestrial ecosystem carbon sink is currently offsetting 7–15% of national anthropogenic emissions and has received widespread attention regarding its role in the ‘carbon neutrality' strategy. We provide perspectives on this question by inferring from the fundamental principles of terrestrial ecosystem carbon cycles. We first elucidate the basic ecological theory that, over the long-term succession of ecosystem without regenerative disturbances, the carbon sink of a given ecosystem will inevitably approach zero as the ecosystem reaches its equilibrium state or climax. In this sense, we argue that the currently observed global terrestrial carbon sink largely emerges from the processes of carbon uptake and release of ecosystem responding to environmental changes and, as such, the carbon sink is never an intrinsic ecosystem function. We further elaborate on the long-term effects of atmospheric CO_(2) changes and afforestation on China's terrestrial carbon sink: the enhancement of the terrestrial carbon sink by the CO_(2) fertilization effect will diminish as the growth of the atmospheric CO_(2) slows down, or completely stops, depending on international efforts to combat climate change, and carbon sinks induced by ecological engineering, such as afforestation, will also decline as forest ecosystems become mature and reach their late-successional stage. We conclude that terrestrial ecosystems have nonetheless an important role to play to gain time for industrial emission reduction during the implementation of the ‘carbon neutrality' strategy. In addition, science-based ecological engineering measures including afforestation and forest management could be used to elongate the time of ecosystem carbon sink service. We propose that the terrestrial carbon sink pathway should be optimized, by addressing the questions of ‘when' and ‘where' to plan afforestation projects, in order to effectively strengthen the terrestrial ecosystem carbon sink and maximize its contribution to the realization of the ‘carbon neutrality' strategy.

Global methane and nitrous oxide emissions from terrestrial ecosystems due to multiple environmental changes

Greenhouse gas(GHG)-induced climate change is among the most pressing sustainability challenges facing humanity today,posing serious risks for ecosystem health.Methane(CH_(4))and nitrous oxide(N_(2)O)are the two most important GHGs after carbon dioxide(CO_(2)),but their regional and global budgets are not well known.In this study,we applied a process-based coupled biogeochemical model to concurrently estimate the magnitude and spatial and temporal patterns of CH_(4)and N_(2)O fluxes as driven by multiple environmental changes,including climate variability,rising atmospheric CO_(2),increasing nitrogen deposition,tropospheric ozone pollution,land use change,and nitrogen fertilizer use.The estimated CH_(4)and N_(2)O emissions from global land ecosystems during 1981-2010 were 144.39±12.90 Tg C/yr(mean 62 SE;1 Tg=1012 g)and 12.52±0.74 Tg N/yr,respectively.Our simulations indicated a significant(P,0.01)annually increasing trend for CH_(4)(0.43±0.06 Tg C/yr)and N_(2)O(0.14±0.02 Tg N/yr)in the study period.CH_(4)and N_(2)O emissions increased significantly in most climatic zones and continents,especially in the tropical regions and Asia.The most rapid increase in CH_(4)emission was found in natural wetlands and rice fields due to increased rice cultivation area and climate warming.N_(2)O emission increased substantially in all the biome types and the largest increase occurred in upland crops due to increasing air temperature and nitrogen fertilizer use.Clearly,the three major GHGs(CH_(4),N_(2)O,and CO_(2))should be simultaneously considered when evaluating if a policy is effective to mitigate climate change.

Spatial variation in annual actual evapotranspiration of terrestrial ecosystems in China: Results from eddy covariance measurements

Understanding the spatial variation in annual actual evapotranspiration （AET） and its influencing factors is crucial for a better understanding of hydrological processes and water resources management. By synthesizing ecosystem-level observations of eddy-covariance flux sites in China （a total of 61 sites）, we constructed the most complete AET dataset in China up to now. Based on this dataset, we quantified the statistic characteristics of AET and water budgets （defined as the ratio of AET to annual mean precipitation （MAP）, AET/MAP） of terrestrial ecosystems in China. Results showed that AET differed significantly among both different vegetation types and climate types in China, with overall mean AET of 534.7＋232.8 mm yr1. AET/MAP also differed significantly among different climate types, but there were no distinct differences in AET/MAP values across vegetation types, with mean AET/MAP of 0.82＋0.28 for non-irrigated ecosystems. We further investigated how the main climatic factors and vegetation attributes control the spatial variation in AET. Our findings revealed that the spatial variation of AET in China was closely correlated with the geographical patterns of climate and vegetation, in which the effects of total annual net radiation （Ro）, MAP and mean annual air temperature （MAT） were dominant. Thus, we proposed an empirical equation to describe the spatial patterns of AET in China, which could explain about 84% of the spatial variation in AET of terrestrial ecosystems in China. Based on the constructed dataset, we also evaluated the uncertainties of five published global evapotranspiration products in simulating site-specific AET in China. Results showed that large biases in site-specific AET values existed for all five global evapotranspiration products, which indicated that it is necessary to involve more observation data of China in their parameterization or validation, while our AET dataset would provide a data source for it.

Carbon cycle in the Arctic terrestrial ecosystems in relation to the global warming

The relationship between the global warming and carbon cycle in the Arctic terrestrial ecosystem was discussed based on a literature survey. As a result, atmospheric carbon dioxide (CO 2) and methane (CH 4) concentrations increased markedly during the past few centuries. The increase in concentration of these greenhouse gases was coupled with the global warming. Summer temperature in the Arctic regions showed a rapid rising. The Arctic soil is a huge organic carbon pool, with a mean estimate of 355×10 9 tC, being 23.7% 32.3% of global soil carbon pool. At present the Arctic terretrial ecosystem is functioning as a sink of atmospheric CO 2. The rising global temperature resulting from an increase in atmospheric CO 2 would influence markedly the Arctic soil carbon and CO 2 source/sink relation of the Arctic ecosystems.

Carbon sink response of terrestrial vegetation ecosystems in the Yangtze River Delta and its driving mechanism

The carbon cycle of terrestrial ecosystems is influenced by global climate change and human activities.Using remote sensing data and land cover products,the spatio-temporal variation characteristics and trends of NEP in the Yangtze River Delta from 2000 to 2020 were analyzed based on the soil respiration model.The driving influences of ecosystem structure evolution,temperature,rainfall,and human activities on NEP were studied.The results show that the NEP shows an overall distribution pattern of high in the southeast and low in the northwest.The area of carbon sinks is larger than that of the carbon sources.NEP spatial heterogeneity is significant.NEP change trend is basically unchanged or significantly better.The future change trend in most areas will be continuous decrease.Compared with temperature,NEP are more sensitive to precipitation.The positive influence of human activities on NEP is mainly observed in north-central Anhui and northern Jiangsu coastal areas,while the negative influence is mainly found in highly urbanized areas.In the process of ecosystem structure,the contribution of unchanged areas to NEP change is greater than that of changed areas.

The temporal and spatial patterns of terrestrial net primary productivity in China

In this paper, we use CEVSA, a process-based model, which has been validated on regional and global scales, to explore the temporal and spatial patterns of Net Primary Productivity (NPP) and its responses to interannual climate fluctuations in China's terrestrial ecosystems over the period 1981-1998. The estimated results suggest that, in this study period, the averaged annual total NPP is about 3.09 Gt C/yr -1 and average NPP is about 342 g C/m 2 . The results also showed that the precipitation was the key factor determining the spatial distribution and temporal trends of NPP. Temporally, the total NPP exhibited a slowly increasing trend. In some ENSO years (e.g. 1982, 1986, 1997) NPP decreased clearly compared to the previous year, but the relationship between ENSO and NPP is complex due to the integrated effects of monsoons and regional differentiation. Spatially, the relatively high NPP occurred at the middle high latitudes, the low latitudes and the lower appeared at the middle latitudes. On national scale, precipitation is the key control factor on NPP variations and there exists a weak correlation between NPP and temperature, but regional responses are greatly different.

Summary of Recent Climate Change Studies on the Carbon and Nitrogen Cycles in the Terrestrial Ecosystem and Ocean in China

This article reviews recent advances over the past and their relationship to climate change in China. The was 0.19-0.26 Pg C yr-1 for the 1980s and 1990s. 4 years in the study of the carbon-nitrogen cycling net carbon sink in the Chinese terrestrial ecosystem Both natural wetlands and the rice-paddy regions emitted 1.76 Tg and 6.62 Tg of CH4 per year for the periods 1995 2004 and 2005 2009, respectively. China emitted -1.1 Tg N20-N yr-1 to the atmosphere in 2004. Land soil contained -8.3 Pg N. The excess nitrogen stored in farmland of the Yangtze River basin reached 1.51 Tg N and 2.67 Tg N in 1980 and 1990, respectively. The outer Yangtze Estuary served as a moderate or significant sink of atmospheric CO2 except in autumn. Phytoplankton could take up carbon at a rate of 6.4 ×1011 kg yr-1 in the China Sea. The global ocean absorbed anthropogenic CO2 at the rates of 1.64 and 1.73 Pg C yr-1 for two sinmlations in the 1990s. Land net ecosystem production in China would increase until the mid-21st century then would decrease gradually under future climate change scenarios. This research should be strengthened in the future, including collection of more observation data, measurement of the soil organic carbon （SOC） loss and sequestration, evaluation of changes in SOC in deep soil layers, and the impacts of grassland management, carbon-nitrogen coupled effects, and development and improvement of various component models and of the coupled carbon cycle-climate model.

Quantifying the impacts of fire aerosols on global terrestrial ecosystem productivity with the fully-coupled Earth system model CESM

Fire is a global phenomenon and a major source of aerosols from the terrestrial biosphere to the atmosphere.Most previous studies quantified the effect of fire aerosols on climate and atmospheric circulation,or on the regional and site-scale terrestrial ecosystem productivity.So far,only one work has quantified their global impacts on terrestrial ecosystem productivity based on offline simulations,which,however,did not consider the impacts of aerosol–cloud interactions and aerosol–climate feedbacks.This study quantitatively assesses the influence of fire aerosols on the global annual gross primary productivity(GPP)of terrestrial ecosystems using simulations with the fully coupled global Earth system model CESM1.2.Results show that fire aerosols generally decrease GPP in vegetated areas,with a global total of−1.6 Pg C yr^−1,mainly because fire aerosols cool and dry the land surface and weaken the direct photosynthetically active radiation(PAR).The exception to this is the Amazon region,which is mainly due to a fire-aerosol-induced wetter land surface and increased diffuse PAR.This study emphasizes the importance of the influence of fire aerosols on climate in quantifying global-scale fire aerosols’impacts on terrestrial ecosystem productivity.

Simulation of terrestrial carbon cycle balance model in Tibet

Based on climate material, the simplified terrestrial carbon cycle balance (TCCB) model was established, which is semi-mechanism and semi-statistics. Through TCCB model, our estimate indicates that the southeastern part of the Tibetan Plateau has much higher carbon content, and we have calculated the litter carbon pool, NPP, carbon fluxes and described their spatial characteristics in this region. Based on the TCCB model simulation, NPP in Tibet is 1.73×10 8 tC/a, soil organic input rate is 0.66×10 8 tC/a, litter mineralization rate is 1.07×10 8 tC/a, vegetation litterfall rate is 1.73×10 8 tC/a, the litter carbon pool is 7.26×10 8 tC, and soil decomposition rate is 309.54×10 8 tC/a. The carbon budget was also analyzed based on the estimates of carbon pool and fluxes. The spatial distributions of carbon pools and carbon fluxes in different compartments of terrestrial ecosystem were depicted with map respectively in Tibet. The distribution of NPP, vegetation litterfall rate, litter, litter mineralization rate, soil organic input rate and the soil decomposition rate were abstracted with temperature, precipitation, fractional vegetation and land feature.

Effects of grassland amelioration on terrestrial ecosystem nutrients:a case study in Jianou Niukenglong Grassland Ecosystem Experimental Station, Fujian Province

This paper studies the effects of land cover changes on distributions andcirculations of nutrients in a terrestrial ecosystem, taking Jianou Niukenglong Grassland EcosystemExperimental Station as a case study. During a two year experiment from 1994 to 1996, the land covertypes were changed from desert slopeland to grasslands, in particular, Chamaecristarotundifolia(pers) green + Pasdum thunbergii and Glycine max var. + Pasalum thunbergii. In order tostudy land cover change effects on nutrients in the terrestrial ecosystem, we selected organicmaterials (OMs), nitrogen (N), phosphorus (P), potassium (K) and aluminum (Al) to study theirchanges in total soil nutrient concentrations, nutrient reserves in soil, distributions andreservations of nutrients in distinct grassland communities and overall nutrient contents reservedin terrestrial ecosystem, and their circulation with land cover change. The experimental resultsindicate that with the increase of vegetation coverage, the total concentrations of N, P and K growrapidly in the soil, but that of Al decreases markedly. The increases of the total concentrations ofN, P and K were mainly the consequences of changes of the factors that affect soil evolution, e.g.,soil moisture, and changes of soil evolution processes, e.g., weathering rate and the decrease ofsoil erosion. These changes were caused by land coverage growth from desert slopeland to grassland.With the change of the land cover types and the increase of land coverage, the activity of Alaccelerated as well, and the vertical penetration and lateral penetration of Al have been increased.Therefore, the loss of Al within the experimental terrestrial ecosystem was inevitable, and thetotal concentration and reserve of Al in soil have become smaller and smaller, in spite of thegrowth of grass absorbing some amounts of Al. The Al reserve has increased in vegetation, but it hasdeclined in total terrestrial ecosystem. Land cover change also affects the circulations ofnutrients in the terrestrial ecosystem and for the purpose of study on nutrient circulations, wechoose to study plant absorption, litter and reservation of nutrients to establish an index toindicate the situations of nutrient circulations within terrestrial ecosystems. The results indicatethat in the two land cover types (two grassland ecosystems), the sequence of nutrient circulationindices are N > K > P > Al in Chamaecrista rotundifolia(pers) green + Pasalum thunbergii and P > N >K > Al in Glycine max var. + Pasalum thunbergii. On the basis of the study, we can conclude thatland cover change affects both distributions and circulations in the terrestrial ecosystem, and thatdifferent changes have distinct influences on distributions and circulations. Some nutrients wereaffected differently in some contents.

Effects of atmospheric mercury pollution on terrestrial ecosystem in Chongqing, China

The results from investigations indicated that mercury pollution in terrestrial ecosystem was serious due to the anthropogenic mercury emission growing in Chongqing, China. The concentration of atmospheric mercury in Chongqing was 34.4±2.7 ng/m\+3 with the range of 9.2—101.5. The accumulation of mercury in surface soil was increasing with time. The mercury content of some agricultural products have exceeded the food health standard value, especially near the mercury emission sources. The mercury accumulation in soil plant system was affected by atmospheric mercury and a positive correlation between them was found. Volatilization of mercury was the most important processes with which soil mercury joined the global mercury recycling.