Loss coefficient of nitrogenous non-point source pollution under various precipitation conditions

In this study, calibrations of non-point source (NPS) pollution models are performed based on Black River basin historical real-time runoff data, sedimentation record data, and NPS sources survey information. The concept of NPS loss coefficient for the watershed or the loss coefficients (LC) for simplicity is brought up by examining NPS build-up and migration processes along riverbanks in natural river systems. The historical data is used for determining the nitrogenous NPS loss coefficient for five land use types including farmland, urban land, grassland, shrub land, and forest under different precipitation conditions. The comparison of outputs from Soil and Water Assessment Tool (SWAT) model and coefficient export method showed that both methods could obtain reasonable LC. The high Pearson correlation coefficient (0.94722) between those two sets of calculation results justified the consistency of those two models. Another result in the study is that different combinations of precipitation condition and land use types could significantly affect the calculated loss coefficient. As for the adsorptive nitrogen, the order of impact on LC for different land use types can be sorted as: farm land > urban land > grassland > shrub land > forest while the order was farmland > grass land > shrub land > forest s>urban land for soluble nitrogen.     

Human drivers,biophysical changes,and climatic variation affecting contemporary cropping proportions in the northern prairie of the U.S

Grassland to cropland conversion in the northern prairie of the United States has been a topic of recent land use change studies. Within this region more corn and soybeans are grown now (2017) than in the past, but most studies to date have not examined multi-decadal trends and the synergistic web of socio-ecological driving forces involved, opting instead for short-term analyses and easily targeted agents of change. This paper examines the coalescing of biophysical and socioeconomic driving forces that have brought change to the agricultural landscape of this region between 1980 and 2013. While land conversion has occurred, most of the region’s cropland in 2013 had been previously cropped by the early 1980s. Furthermore, the agricultural conditions in which crops were grown during those three decades have changed considerably because of non-biophysical alterations to production practices and changing agricultural markets. Findings revealed that human drivers played more of a role in crop change than biophysical changes, that blending quantitative and qualitative methods to tell a more complete story of crop change in this region was difficult because of the synergistic characteristics of the drivers involved, and that more research is needed to understand how farmers make crop choice decisions.     

基于MLP-ANN与Markov Chain的土地利用变化预测方法——以锡林郭勒盟为例

以北方草地典型地区—内蒙古锡林郭勒盟为案例区,在1995年到2000年的土地利用变化与驱动力分析的基础上,利用土地利用转换类型和驱动力模型,采用多层感知人工神经网络模型分析了各种土地利用类型未来的转换潜力;利用马尔可夫链模型,预测了2005和2010年土地利用格局。预测结果显示：高覆盖度草地减少幅度最大,中覆盖度草地减少相对和缓,高、中覆盖度草地的减少造成了未利用地和低覆盖度草地的增加,尤其是前者增加的幅度最大;从空间分布看,高覆盖度草地的减少集中在西北部地区,主要转变为中低覆盖度草地,中覆盖度草地的减少主要集中在西南部地区,其流向主要是以沙化土地为主的未利用地;案例研究表明,多层感知人工神经网络模型与马尔可夫链模型的结合与应用能够在很大程度上预测稳定驱动力作用下的土地利用变化趋势,从而为生态干预提供指导。     

Effect of land use and land cover change on soil erosion and the spatio-temporal variation in Liupan Mountain Region, southern Ningxia, China

The Liupan Mountains are located in the southern Ningxia Hui Autonomous Region of China, that forms an important divide between landforms and biogeographic regions. The populated part of the Liupan Mountain Region has suffered tremendous ecological damage over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. To present the relationship between land use/cover change and spatio-temporal variation of soil erosion, data sets of land use between the late 1980s and 2000 were obtained from Landsat Thematic Mapper (TM) imagery, and spatial models were used to characterize landscape and soil erosion conditions. Also, soil erosion in response to land use and land cover change were quantified and analyzed using data from geographical information systems and remote sensing. Soil erosion by water was the dominant mode of soil loss, while soil erosion by wind was only present on a relatively small area. The degree of soil erosion was classified into five severity classes: slight, light, moderate, severe, and very severe. Soil erosion in the Liupan Mountain Region increased between the late 1980s and 2000, both in terms of acreage and severity. Moderate, severe, and very severe eroded areas accounted for 54.86% of the total land area. The lightly eroded area decreased, while the moderately eroded area increased by 368817 ha (22%) followed by severe erosion with 146552 ha (8.8%), and very severe erosion by 97067.6 ha (5.8%). Soil loss on sloping cropland increased with slope gradients. About 90% of the cropland was located on slopes less than 15°. Most of the increase in soil erosion on cropland was due to conversion of steep slopes to cropland and degradation of grassland and increased activities. Soil erosion was severe on grassland with a moderate or low grass cover and on dry land. Human activities, cultivation on steep slopes, and overgrazing of pastures were the main reasons for the increase in erosion severity.     

Habitat loss through disruption of constrained dispersal networks.

Large losses of habitat could be caused by land use change that disrupts the dispersal networks used by migratory species. We assessed the relative losses of habitat for diadromous fish (i.e., those migrating between sea and freshwater) due to physical barriers, degradation of migratory passage associated with catchment land use, and site-scale land use characteristics on the West Coast, South Island, New Zealand. Fish occurrence, land use data, and river network models were analyzed in a GIS and subjected to a three-level hierarchical analysis. To identify accessible habitat not restricted by physical barriers, we used the migratory distance and maximum downstream slope encountered to identify accessible sites in least-impacted catchments and applied the results to all catchments within the study area. For two fish species, banded kokopu (Galaxias fasciatus) and koaro (G. brevipinnis), sites modeled as accessible using logistic regression in least-impacted catchments were then used to assess the impacts of catchment-scale deforestation and downstream land uses on habitat loss. Finally, sites not restricted by physical barriers or land-use-related impacts on migratory passage were used to model the effects of local land use. The models indicated that koaro and banded kokopu potentially had access to 28,000 km and 5300 km, respectively, of the 40,600 km of streams within the study area. Impacts due to intensive agricultural land use downstream in catchments affecting migratory passage were predicted to reduce the accessible habitats for koaro and banded kokopu by 55% and 70%, respectively. Local land use further reduced koaro and banded kokopu habitats to 70% and 90%, respectively, of total accessible habitat. Habitat lost through disruption of the dispersal network was disproportionately large because potentially useable habitat was rendered inaccessible.     

Assessing effects of land use on landscape connectivity: loss and fragmentation of western U.S. forests

Effects of land-use change on the conservation of biodiversity have become a concern to conservation scientists and land managers, who have identified loss and fragmentation of natural areas as a high-priority issue. Despite urgent calls to inform national, regional, and state planning efforts, there remains a critical need to develop practical approaches to identify where important lands are for landscape connectivity (i.e., linkages), where land use constrains connectivity, and which linkages are most important to maintain network-wide connectivity extents. Our overall goal in this paper was to develop an approach that provides comprehensive, quantitative estimates of the effects of land-use change on landscape connectivity and illustrate its use on a broad, regional expanse of the western United States. We quantified loss of habitat and landscape connectivity for western forested systems due to land uses associated with residential development, roads, and highway traffic. We examined how these land-use changes likely increase the resistance to movement of forest species in non-forested land cover types and, therefore, reduce the connectivity among forested habitat patches. To do so, we applied a graph-theoretic approach that incorporates ecological aspects within a geographic representation of a network. We found that roughly one-quarter of the forested lands in the western United States were integral to a network of forested patches, though the lands outside of patches remain critical for habitat and overall connectivity. Using remotely sensed land cover data (ca. 2000), we found 1.7 million km2 of forested lands. We estimate that land uses associated with residential development, roads, and highway traffic have caused roughly a 4.5% loss in area (20 000 km2) of these forested patches, and continued expansion of residential land will likely reduce forested patches by another 1.2% by 2030. We also identify linkages among forest patches that are critical for landscape connectivity. Our approach can be readily modified to examine connectivity for other habitats/ecological systems and for other geographic areas, as well as to address more specific requirements for particular conservation planning applications.     

Economics of Grassland Conversion to Cropland in the Prairie Pothole Region

Abstract: Much of the remaining grassland, particularly in North America, is privately owned, and its conversion to cultivated cropland is largely driven by economics. An understanding of why landowners convert grassland to cropland could facilitate more effective design of grassland‐conservation programs. We built an empirical model of land‐use change in the Prairie Pothole Region (north‐central United States) to estimate the probability of grassland conversion to alternative agricultural land uses, including cultivated crops. Conversion was largely driven by landscape characteristics and the economic returns of alternative uses. Our estimate of the probability of grassland conversion to cultivated crops (1.33% on average from 1979 to 1997) was higher than past estimates (0.4%). Our model also predicted that grassland‐conversion probabilities will increase if agricultural commodity prices continue to follow the trends observed from 2001 to 2006 (0.93% probability of grassland conversion to cultivated crops in 2006 to 1.5% in 2011). Thus, nearly 121 million ha (30 million acres) of grassland could be converted by 2011. Conversion probabilities, however, are spatially heterogeneous (range 0.2% to 3%), depending on characteristics of a parcel (e.g., soil quality and economic returns). Grassland parcels with relatively high‐quality land for agricultural production are more likely to be converted to cultivated crops than lower‐quality parcels and are more responsive to changes in the economic returns on alternative agricultural land uses (i.e., conversion probability increases by a larger magnitude for high‐quality parcels when economics returns to alternative uses increase). Our results suggest that grassland conservation programs could be proactively targeted toward high‐risk parcels by anticipating changes in economic returns, such as could occur if a new biofuel processing plant were to be built in an area.     

Prioritizing sites for conservation based on similarity to historical baselines and feasibility of protection

The concept of shifting baselines in conservation science implies advocacy for the use of historical knowledge to inform these baselines but does not address the feasibility of restoring sites to those baselines. In many regions, conservation feasibility varies among sites due to differences in resource availability, statutory power, and land‐owner participation. We used zooarchaeological records to identify a historical baseline of the freshwater mussel community's composition before Euro‐American influence at a river‐reach scale (i.e., a kilometer stretch of river that is abiotically similar) in the Leon River of central Texas (U.S.A.). We evaluated how the community reference position and the feasibility of conservation might enable identification of sites where conservation actions would preserve historically representative communities and be likely to succeed. We devised a conceptual model that incorporated community information and landscape factors to link the best conservation areas to potential cost and conservation benefits. Using fuzzy ordination, we identified modern mussel beds that were most like the historical baseline. We then quantified housing density and land use near each river reach identified to estimate feasibility of habitat restoration. Using our conceptual framework, we identified reaches of high conservation value (i.e., contain the best mussel beds) and where restoration actions would be most likely to succeed. Reaches above Lake Belton were most similar in species composition and relative abundance to zooarchaeological sites. A subset of these mussel beds occurred in locations where conservation actions appeared most feasible. Our results show how to use zooarchaeological data (biodiversity data often readily available) and estimates of conservation feasibility to inform conservation priorities at a local spatial scale.     

Quantifying cultural values associated with deforestation in the Brazilian Amazon

This study analyzes the distribution of cultural values associated with forest and non-forest landscapes among stakeholder groups shaping land use and land cover change (LULCC) in an agricultural/forest frontier in the western Brazilian Amazon. The study addresses theoretical and methodological obstacles to the integration of cultural data and social science research into the study of LULCC, providing a simple, systematic, and more accurate way of understanding this missing feature of land change. The findings offer insights on elusive cultural features that influence how diverse actors make land use decisions and respond to drivers, and can thus contribute to enhancing the predictive capacity of land change research.     

Temporal and spatial patterns and driving factors of cultivated land change in Qinghai-Tibet Plateau北大核心CSCD

随着经济快速发展、城镇化进程加快以及人口基数不断增加,在城市用地不断向外扩张以及生态退耕措施的影响下,耕地面积呈逐年减小的趋势.这一现象加剧了农业发展与其他要素间的矛盾,对区域粮食安全也产生重要影响,因此,探讨耕地面积时空变化及其驱动机制对保障区域粮食安全具有现实意义.分析青藏高原地区1980年、1990年、2000年、2010年、2018年的耕地面积数据,结合户籍人口、地区生产总值(GDP)、粮食单产等统计年鉴资料解析影响其变化的主要驱动因子.结果表明:(1)青藏高原近40年耕地面积变化总体经历缓慢增加、显著增加和缓慢递减3个阶段,整个变化过程中耕地主要流失方向为林地和草地,分别占总流失面积的50.99%和32.02%,主要原因为退耕还林还草等政策的实施,其次为建设用地和水域增加.(2)耕地转为非耕地的地区主要集中在四川西部、云南西北部、青海东部,而耕地转入地区主要集中在青藏高原中部.以地市州来看,拉萨、海东、海西、阿坝、林芝等地区耕地面积变化特征以缓慢递增为主;西宁、黄南、甘孜、甘南等地区的耕地面积则呈缓慢递减的变化趋势.(3)主成分分析和结构方程模型结果显示影响耕地面积减少的主要驱动因素包括经济社会发展和粮食生产.其中经济和社会因素对耕地面积变化产生的影响为负值,社会因素产生的负影响最大,为-0.224,人口基数增长、建设用地扩张、土地利用转型要求以及二、三产业红利的吸引都会导致耕地面积减小.本研究揭示了青藏高原地区近40年耕地变化情况及流失方向,耕地面积波动主要受到经济社会因素以及政策因素的影响;上述结果可为今后国家粮食安全及当地生态环境可持续发展提供理论参考.(图7表8参45)     

Modeled historical land use and land cover for the conterminous United States

The landscape of the conterminous United States has changed dramatically over the last 200 years, with agricultural land use, urban expansion, forestry, and other anthropogenic activities altering land cover across vast swaths of the country. While land use and land cover (LULC) models have been developed to model potential future LULC change, few efforts have focused on recreating historical landscapes. Researchers at the US Geological Survey have used a wide range of historical data sources and a spatially explicit modeling framework to model spatially explicit historical LULC change in the conterminous United States from 1992 back to 1938. Annual LULC maps were produced at 250-m resolution, with 14 LULC classes. Assessment of model results showed good agreement with trends and spatial patterns in historical data sources such as the Census of Agriculture and historical housing density data, although comparison with historical data is complicated by definitional and methodological differences. The completion of this dataset allows researchers to assess historical LULC impacts on a range of ecological processes.     

Scale dependency in effectiveness,isolation, and social‐ecological spillover of protected areas

Protected areas are considered vital for the conservation of biodiversity. Given their central role in many conservation strategies, it is important to know whether they adequately protect biodiversity within their boundaries; whether they are becoming more isolated from other natural areas over time; and whether they play a role in facilitating or reducing land‐cover change in their surroundings. We used matching methods and national and local analyses of land‐cover change to evaluate the combined effectiveness (i.e., avoided natural‐cover loss), isolation (i.e., changes in adjacent areas), and spillover effects (i.e., impacts on adjacent areas) of 19 national parks in South Africa from 2000 to 2009. All parks had either similar or lower rates of natural‐cover loss than matched control samples. On a national level, mean net loss of natural cover and mean net gain of cultivation cover decreased with distance from park boundary, but there was considerable variation in trends around individual parks, providing evidence for both increased isolation and buffering of protected areas. Fourteen parks had significant positive spillover and reduced natural‐cover loss in their surroundings, whereas five parks experienced elevated levels of natural‐cover loss. Conclusions about social‐ecological spillover effects from protected areas depended heavily on the measures of land‐cover change used and the scale at which the results were aggregated. Our findings emphasize the need for high‐resolution data when assessing spatially explicit phenomena such as land‐cover change and challenge the usefulness of large‐scale (coarse grain, broad extent) studies for understanding social‐ecological dynamics around protected areas.     

Field measurements of soil CO2 efflux in Heteropogon contortus dominated grassland of semi-arid eco-system

Seasonal changes in soil respiration (SR), soil temperature (ST) and soil moisture (SM) were compared between a barren land with no vegetation (control) and grassland dominated by Heteropogon contortus (L.) of a semi-arid eco-system during 2005-2006. A statistically significant (p<0.001) seasonal change in SR was observed between the two sites. The variation characteristics of soil CO2 effiux rates were observed during wet periods along precipitation gradients and it was consistently higher in grasslands than in control.A maximum soil CO2 efflux of 13.35 +/- 0.33 micromol m2 s-1 in grassland and 7.33 +/- 0.8 micromol m2 s- in control was observed during rainy season-ll, i.e., from October to December, a minimum of 1.27 +/- 0.2 micromol m-2 s-1 in grassland and 0.67 +/- 0.5 micromol m-2 s-1 in control during summer season, i.e., from March to June. A positive significant relation observed between soil respiration and soil moisture (r2above 0.8) and no significant relation was observed between soil CO2 efflux and soil temperature (r2 below 0.3). In water-limited semi-arid ecosystem, rewetting of the soil due to precipitation events triggered the increased pulses of soil respiration especially in grassland when compared to the barren land. The observed soil respiration rates during summer and after the subsequent precipitation events strongly indicated that the soil water-deficit conditions reduce the efflux both in barren land (control) and in grassland of semi-arid eco-system.     

Landscape-level influences of terrestrial snake occupancy within the southeastern United States

Habitat loss and degradation are thought to be the primary drivers of species extirpations, but for many species we have little information regarding specific habitats that influence occupancy. Snakes are of conservation concern throughout North America, but effective management and conservation are hindered by a lack of basic natural history information and the small number of large-scale studies designed to assess general population trends. To address this information gap, we compiled detection/nondetection data for 13 large terrestrial species from 449 traps located across the southeastern United States, and we characterized the land cover surrounding each trap at multiple spatial scales (250-, 500-, and 1000-m buffers). We used occupancy modeling, while accounting for heterogeneity in detection probability, to identify habitat variables that were influential in determining the presence of a particular species. We evaluated 12 competing models for each species, representing various hypotheses pertaining to important habitat features for terrestrial snakes. Overall, considerable interspecific variation existed in important habitat variables and relevant spatial scales. For example, kingsnakes (Lampropeltis getula) were negatively associated with evergreen forests, whereas Louisiana pinesnake (Pituophis ruthveni) occupancy increased with increasing coverage of this forest type. Some species were positively associated with grassland and scrub/shrub (e.g., Slowinski's cornsnake, Elaphe slowinskii) whereas others, (e.g., copperhead, Agkistrodon contortrix, and eastern diamond-backed rattlesnake, Crotalus adamanteus) were positively associated with forested habitats. Although the species that we studied may persist in varied landscapes other than those we identified as important, our data were collected in relatively undeveloped areas. Thus, our findings may be relevant when generating conservation plans or restoration goals. Maintaining or restoring landscapes that are most consistent with the ancestral habitat preferences of terrestrial snake assemblages will require a diverse habitat matrix over large spatial scales.     

A Comparison of Landscapes Occupied by Increasing and Decreasing Populations of Grassland Birds

Abstract:  For several decades, many grassland bird species have been declining in abundance throughout the Midwest and Great Plains regions of the United States, possibly due to loss of natural grassland habitat and increasing urbanization. I used 20 years of data from the North American Breeding Bird Survey to identify increasing, decreasing, and stable populations of 36 grassland-nesting bird species. I characterized the immediate landscape (circle with radius = 30 km) surrounding each population based on data from the National Resources Inventory. For each landscape, I calculated the proportion of eight different land-cover types: restored grassland, rangeland, cultivated cropland, pasture, noncultivated cropland, forest, urban land, and water. Using a null model, I compared landscape composition of increasing, decreasing, and stable populations. As predicted on the basis of the habitat preferences of grassland birds, increasing populations inhabited landscapes that contained significantly more restored grassland and rangeland but significantly less forest land and urban land than landscapes inhabited by decreasing populations. There was no significant difference in the proportion of cropland within the landscapes of increasing and decreasing populations, although cropland composed a large proportion (>30%) of many landscapes. In contrast, restored grassland typically composed a very small proportion (<3.5%) of total land cover, yet it was significantly more common in the landscapes of increasing than decreasing populations. These results suggest that grassland birds may benefit from government initiatives, such as the Conservation Reserve Program, that promote the restoration of grassland at a landscape scale.     

Future habitat loss and extinctions driven by land‐use change in biodiversity hotspots under four scenarios of climate‐change mitigation

Numerous species have been pushed into extinction as an increasing portion of Earth's land surface has been appropriated for human enterprise. In the future, global biodiversity will be affected by both climate change and land‐use change, the latter of which is currently the primary driver of species extinctions. How societies address climate change will critically affect biodiversity because climate‐change mitigation policies will reduce direct climate‐change impacts; however, these policies will influence land‐use decisions, which could have negative impacts on habitat for a substantial number of species. We assessed the potential impact future climate policy could have on the loss of habitable area in biodiversity hotspots due to associated land‐use changes. We estimated past extinctions from historical land‐use changes (1500–2005) based on the global gridded land‐use data used for the Intergovernmental Panel on Climate Change Fifth Assessment Report and habitat extent and species data for each hotspot. We then estimated potential extinctions due to future land‐use changes under alternative climate‐change scenarios (2005–2100). Future land‐use changes are projected to reduce natural vegetative cover by 26‐58% in the hotspots. As a consequence, the number of additional species extinctions, relative to those already incurred between 1500 and 2005, due to land‐use change by 2100 across all hotspots ranged from about 220 to 21000 (0.2% to 16%), depending on the climate‐change mitigation scenario and biological factors such as the slope of the species–area relationship and the contribution of wood harvest to extinctions. These estimates of potential future extinctions were driven by land‐use change only and likely would have been higher if the direct effects of climate change had been considered. Future extinctions could potentially be reduced by incorporating habitat preservation into scenario development to reduce projected future land‐use changes in hotspots or by lessening the impact of future land‐use activities on biodiversity within hotspots.     

Local Land‐Use Planning to Conserve Biodiversity: Planners’ Perspectives on What Works

Abstract: Because habitat loss due to urbanization is a primary threat to biodiversity, and land‐use decisions in urbanizing areas are mainly made at the local level, land‐use planning by municipal planning departments has a potentially important—but largely unrealized—role in conserving biodiversity. To understand planners’ perspectives on the factors that facilitate and impede biodiversity conservation in local planning, we interviewed directors of 17 municipal planning departments in the greater Seattle (Washington, U.S.A.) area and compared responses of planners from similar‐sized jurisdictions that were “high” and “low performing” with respect to incorporation of biodiversity conservation in local planning. Planners from low‐performing jurisdictions regarded mandates from higher governmental levels as the primary drivers of biodiversity conservation, whereas those from high‐performing jurisdictions regarded community values as the main drivers, although they also indicated that mandates were important. Biodiversity conservation was associated with presence of local conservation flagship elements (e.g., salmonids) and human‐centered benefits of biodiversity conservation (e.g., quality of life). Planners from high‐ and low‐performing jurisdictions favored different planning mechanisms for biodiversity conservation, perhaps reflecting differences in funding and staffing. High performers reported more collaborations with other entities on biodiversity issues. Planners’ comments indicated that the term biodiversity may be problematic in the context of local planning. The action most planners recommended to increase biodiversity conservation in local planning was public education. These results suggest that to advance biodiversity conservation in local land‐use planning, conservation biologists should investigate and educate the public about local conservation flagships and human benefits of local biodiversity, work to raise ecological literacy and explain biodiversity more effectively to the public, and promote collaboration on biodiversity conservation among jurisdictions and inclusion of biodiversity specialists in planning departments.     

North East Scotland River Catchment Nitrate Loading in Relation to Agricultural Intensity

Modern agricultural practices have been strongly linked with increased NO₃-N loadings in surface waters. Nitrate leaching increases as land use progresses from forest and moorland through grassland, to arable agriculture. There are, within the UK, few studies on a regional scale capable of displaying a relationship between land cover (agricultural intensity) and water quality. This relationship can be investigated using computer manipulation of spatial geographic information together with conventional river and agricultural census data.

Simple regression analysis against primary land cover suggests that agriculture is reponsible for annual losses of nitrate in North East Scotland river catchments. Further multi-linear regression analysis, using the GIS data and agricultural census returns indicate that most of the outstanding variation can be accounted for if the agricultural variable is related to agricultural practice, such as spring, winter and grass cropping.     

Simulation of soil carbon changes due to land use change in urban areas in China

Land use change can have a strong impact on soil carbon dynamics and carbon stocks in urban areas. Due to rapid urbanization, large areas of land have been paved, and other areas have undergone rapid land use change. Evaluation of the impact of urbanization on carbon dynamics and carbon stock (30 cm) has become an issue of urgent concern. The soil carbon dynamics, due to rapid land use change in Tianjin Binhai New Area of China, have been simulated in this paper using the RothC model. Because this area is saline, a modified version of RothC that includes a salt rate modifier provided more accurate simulations than the original model. The conversion to urban green land was not accurately simulated by either of the models because of the undefined changes in soil and plant conditions. According to the model, changes of arable to grassland resulted in a decline in soil carbon stocks, and changes of grassland to forest and grassland to arable resulted in increased soil carbon stocks in this area. Across the whole area simulated, the total carbon stocks in 2010 had decreased due to land use change by 6.5% from the 1979 value. By 2050, a further decrease of 21.9% is expected according to the 2050 plan for land use and the continuing losses from the soils due to previous land use changes.     

我国自然保护区建设及其对生物多样性的保护

到1991年底,我国共建立各种类型自然保护区708个,总面积56066.6kha,约占国土面积的5.54％。本文从我国森林、草原、荒漠、内陆湿地和水域、海洋、海岸等生态系统类型自然保护区以及野生动、植物类型自然保护区的建设着手,全面分析了我国自然保护区建设对生物多样性保护的贡献和存在的不足。