Modeling sediment accumulation in North American playa wetlands in response to climate change, 1940–2100

Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and examined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.     

山地风电场开发过程中水土流失相关问题研究进展

风力发电在提供清洁能源的同时亦带来了一定程度的水土流失和生态环境破坏。特别是山地风电场,由于其所在的山区土壤抗蚀性低,且植被破坏后恢复难度大,在开发过程中引起的水土流失问题尤为突出。回顾了山区风电场水土流失特点、影响风电场水土流失关键因子等方面的相关研究成果,并对其进行了总结。山区风电场水土流失具有地域不完整性及扰动多样性的特点,道路施工区、风电机组建设区是水土流失的重点区域;水土流失呈现时空分布不均性特点,水土流失时段主要集中在施工期,且流失剧烈阶段主要发生在每年的降雨集中期;降雨是影响风电场水土流失的关键因子,滑坡稳定性系数在降水期间急剧下降,降水入渗作用促进了边坡变形破坏向不利的一面发展,容易引起水土流失及边坡不稳;降雨侵蚀力指标与降雨量及雨强有关,按照获取气象资料的不同,目前主要采用月降雨量及日降雨量来分别估算降雨侵蚀力;在进行山区风电场水土流失强度预测时,将整个预测区域划分为4~6个单元,确定各预测单元工程扰动前、施工期、扰动后的土壤侵蚀模数,采用类比法结合数学模型法预测造成的水土流失量。     

Beneficial land use change: Strategic expansion of new biomass plantations can reduce environmental impacts from EU agriculture

Society faces the double challenge of increasing biomass production to meet the future demands for food, materials and bioenergy, while addressing negative impacts of current (and future) land use. In the discourse, land use change (LUC) has often been considered as negative, referring to impacts of deforestation and expansion of biomass plantations. However, strategic establishment of suitable perennial production systems in agricultural landscapes can mitigate environmental impacts of current crop production, while providing biomass for the bioeconomy. Here, we explore the potential for such “beneficial LUC” in EU28. First, we map and quantify the degree of accumulated soil organic carbon losses, soil loss by wind and water erosion, nitrogen emissions to water, and recurring floods, in ∼81.000 individual landscapes in EU28. We then estimate the effectiveness in mitigating these impacts through establishment of perennial plants, in each landscape. The results indicate that there is a substantial potential for effective impact mitigation. Depending on criteria selection, 10–46% of the land used for annual crop production in EU28 is located in landscapes that could be considered priority areas for beneficial LUC. These areas are scattered all over Europe, but there are notable “hot-spots” where priority areas are concentrated, e.g., large parts of Denmark, western UK, The Po valley in Italy, and the Danube basin. While some policy developments support beneficial LUC, implementation could benefit from attempts to realize synergies between different Sustainable Development Goals, e.g., “Zero hunger”, “Clean water and sanitation”, “Affordable and Clean Energy”, “Climate Action”, and “Life on Land”.     

Satellite-Based Monitoring of Decadal Soil Salinization and Climate Effects in a Semi-arid Region of China

Soil salinization is a common phenomenon that affects both the environment and the socio-economy in arid and semi-arid regions; it is also an important aspect of land cover change. In this study, we integrated multi-sensor remote sensing data with a field survey to analyze processes of soil salinization in a semi-arid area in China from 1979 to 2009. Generally, the area of salt-affected soils increased by 0.28% per year with remarkable acceleration from 1999 to 2009 (0.42% increase per year). In contrast, the area of surface water bodies showed a decreasing trend (-0.08% per year) in the same period. Decreases in precipitation and increases in aridity due to annual (especially summer) warming provided a favorable condition for soil salinization. The relatively flat terrain favored waterlogging at the surface, and continuous drought facilitated upward movement of soil water and accumulation of surface saline and calcium. Meanwhile, land-use practices also played a crucial role in accelerating soil salinization. The conversion to cropland from natural vegetation greatly increased the demand for groundwater irrigation and aggravated the process of soil salinization. Furthermore, there are potential feedbacks of soil salinization to regional climate. The salinization of soils can limit the efficiency of plant water use as well as photosynthesis; therefore, it reduces the amount of carbon sequestrated by terrestrial ecosystem. Soil salinization also reduces the absorbed solar radiation by increasing land surface albedo. Such conversions of land cover significantly change the energy and water balance between land and atmosphere.     

Potential impact of land use change on land productivity dynamics with focus on land degradation in a sub-humid terrestrial ecosystem

The aim of this study was to generate a land productivity dynamics (LPD) map of a degraded catchment located in sub-humid terrestrial ecosystem via a land degradation assessment using three indicators, namely land use and land cover, land productivity, and soil organic carbon density. The study was carried out in two adjacent microcatchments located in Gediz River Basin and conducted between 2001 and 2015. For this purpose, Landsat satellite images were used to determine changing of land use and land cover and vegetation density. In addition, 319 soil samples were collected from surface and subsurface soil depths to detect soil organic carbon density of the study area in May 2015. According to the study results, in more than 23% of the catchments’ area of approx. 3896 ha, land productivity is observed to decline while about 24% shows early signs of decline level. Some of these areas used under agricultural cropping, overgrazed pasture, and artificial areas showed evidence of soil erosion problem. Only very small area of the catchment shows stable and increasing land productivity dynamics trend during the 14-year period.     

区域生态环境质量评价方法研究

以江西省贵溪市为研究区域，从生态学和环境科学观点出发，在3S技术支持下，应用20m分辨率的中巴资源卫星遥感资料、1：100000数字化地理数据和GPS抽样调查数据，结合常规调查统计法，选择与区域生态环境有关的因子(如气候、水资源、土地利用、植被、水土流失)以及部分人类活动和经济因素(污染物排放、人均耕地面积、单位面积粮食产量、人均国内生产总值等)，构建了评价指标体系，空间尺度以研究区域平均水平取值，时间尺度截止到2000年。该体系通过专家定权法和中间截取求平均值方法进行权值估计，应用生态环境评价模型对2000年研究区域的生态环境质量进行评价。结果表明，该研究区域2000年生态环境质量达Ⅱ级标准，生态环境质量总体处较好水平，主要表现在森林覆盖率高于全省平均水平，达61．0％；人均耕地面积及产量水平分别为0．06hm^2／人和8025kg／hm^2，处全省中上水平；水土流失面积达61974hm^2，且治理效果好；生物多样性受到一定保护；GDP居全省前列，为该区域生态环境保护和治理提供了一定的经济基础。目前该区域存在的主要问题是：水质为国家Ⅲ级标准，应通过综合治理进一步提高标准；为较多气象灾害发生区；由于特殊的地理条件，导致土壤侵蚀的隐患较大。     

WRF中土壤图及参数表的更新对华北夏季预报的影响研究

土壤质地及其物理性质的参数化对陆面过程模拟具有明显的影响。研究了土壤质地和土壤水文参数表的更新对WRF（Weather Research and Forecasting）模拟性能的影响。使用北京师范大学土壤属性数据集和修正后的土壤水文参数表替换WRF默认数据,对2017年6—8月华北地区开展数值模拟试验和评估验证。结果表明,模拟结果对土壤类型数据集和水文参数表的更新较为敏感,对地面要素预报有正效果。WRF默认土壤数据集中,中国东部以粘壤土为主,而在北京师范大学土壤数据集里则以壤土为主;修正后的土壤水文参数在Noah陆面过程中增强了裸土潜热蒸发能力。数值模拟试验表明,土壤输入数据和土壤水文参数的更新能够增强陆面向大气的潜热同时减弱感热输送,致使大气底层温度降低而湿度增大。利用华北区域748个地面气象观测站的2 m温度和2 m湿度对2017年夏季的模拟结果进行验证,结果显示更新试验对地面要素的预报偏差有较好的修正作用,能够将2 m温、湿度的预报技巧分别提高3.4%和2.9%。      

浙江省地理参数对地闪的影响

利用2007—2016年浙江省地闪数据,数字地形海拔数据、土地覆盖数据和HWSD数据集,定量化分析海拔、坡度、坡向、土地覆盖类型、土壤电导率对该地区地闪的影响。研究结果表明:浙江省地闪主要集中在海拔0～600m、坡度0°～30°;坡向东南地闪次数最高,坡向西地闪次数最低;林地地闪次数最高,湿地地闪次数最低;地闪对应的电导率主要集中在0.1dS/m。单位面积下,地闪次数随海拔、坡度、电导率均呈现先增加后减少的趋势;坡向东、东南地闪次数较多,坡向西、西南地闪次数较少;土地覆盖类型地闪次数最高是城市和建筑区,最低是水体。此外,地闪强度平均值随海拔增加呈现先减小后增加的趋势;陡度平均值随海拔增加而减小。两参数均随坡度增加而减小;随电导率增加呈现先增加后减少的趋势。以5km×5km为网格单元统计网格内各参量平均值进行相关分析发现,浙江地区电流强度、陡度均和海拔、坡度呈现负相关。     

基于植被指数的绿地信息提取的比较

运用遥感图像处理系统(ENVI)对快鸟(Quickbird)高分辨率遥感影像进行预处理,利用归一化差值植被指数(NDVI)、归一化差异绿度指数(NDGI)、土壤调节植被指数(SAVI)和修正土壤调节植被指数(MSAVI)对南京市鼓楼区进行了绿地信息提取,通过Matlab软件比较了其灰度图像、直方图和二值图像,并分析其方差,在C语言的平台上进行了精度评定.实验结果表明:在该研究区中,SAVI、NDVI的绿地提取能力较好;NDGI、MSAVI出现了明显的漏分、错分情况,但MSAVI在建筑物、植被边缘提取上表现出相对的优越性.     

Soil erosion in the West African Sahel: a review and an application of a “local political ecology” approach in South West Niger

A review of soil erosion research in the West African Sahel finds that there are insufficient data on which to base policy. This is largely because of the difficulties of measuring erosion and the other components of “soil life”, and because of the highly spatially and temporarily variable natural and social environment of the Sahel. However, a “local political ecology” of soil erosion and new methodologies offer some hope of overcoming these problems. Nonetheless, a major knowledge gap will remain, about how rates of erosion are accommodated and appraised within very variable social and economic conditions. An example from recent field work in Niger shows that erosion is correlated with factors such as male migration, suggesting, in this case, that households with access to non-farm income adopt a risk-avoidance strategy in which soil erosion is accelerated incidentally. It is concluded that there needs to be more research into the relations between erosion and socio-economic factors, and clearer thinking about the meaning of sustainability as it refers to soil erosion in the Sahel.     

Effects of Land Use Change On the Storage of Soil Organic Carbon: A Case Study of the Qianyanzhou Forest Experimental Station in China

Forests play an important role in sequestrating carbon from the atmosphere. Since the 1980s, reforestation activities have been implemented in the area surrounding the Qianyanzhou Forest Experimental Station in Jiangxi Province, China. Farmland and heavily eroded waste land were replanted with fruit, orchards and forest plantations. The area surrounding the Qianyanzhou Forest Experimental Station was selected as research site to analyze the potential of reforestation in carbon sequestration. This study evaluates the variation of soil organic carbon storage under the different land use types. Soil organic carbon storage varied greatly with land use types. From 1984 to 2002, soil organic carbon storage increased 2.45 × 10⁶ kg across eight land use types. This study demonstrates the potential for carbon sequestration in soils from reforestation. However, a complete understanding of soil carbon fluxes at the landscape scale will depend on the potential and retention period of soil organic carbon.     

Landslide susceptibility assesssment in the Uttarakhand area (India) using GIS: a comparison study of prediction capability of naïve bayes,multilayer perceptron neural networks,and functional trees methods

The objective of this study is to make a comparison of the prediction performance of three techniques, Functional Trees (FT), Multilayer Perceptron Neural Networks (MLP Neural Nets), and Naïve Bayes (NB) for landslide susceptibility assessment at the Uttarakhand Area (India). Firstly, a landslide inventory map with 430 landslide locations in the study area was constructed from various sources. Landslide locations were then randomly split into two parts (i) 70 % landslide locations being used for training models (ii) 30 % landslide locations being employed for validation process. Secondly, a total of eleven landslide conditioning factors including slope angle, slope aspect, elevation, curvature, lithology, soil, land cover, distance to roads, distance to lineaments, distance to rivers, and rainfall were used in the analysis to elucidate the spatial relationship between these factors and landslide occurrences. Feature selection of Linear Support Vector Machine (LSVM) algorithm was employed to assess the prediction capability of these conditioning factors on landslide models. Subsequently, the NB, MLP Neural Nets, and FT models were constructed using training dataset. Finally, success rate and predictive rate curves were employed to validate and compare the predictive capability of three used models. Overall, all the three models performed very well for landslide susceptibility assessment. Out of these models, the MLP Neural Nets and the FT models had almost the same predictive capability whereas the MLP Neural Nets (AUC = 0.850) was slightly better than the FT model (AUC = 0.849). The NB model (AUC = 0.838) had the lowest predictive capability compared to other models. Landslide susceptibility maps were final developed using these three models. These maps would be helpful to planners and engineers for the development activities and land-use planning.     

Food production and climate protection—What abandoned lands can do to preserve natural forests

Approaches to reconciling food production with climatic and environmental protection often require agricultural intensification. The production of more food per unit of agricultural land through “sustainable intensification” is intended to enable the protection of natural ecosystems elsewhere (land sparing). However, there are problems associated with agricultural intensification; such as soil erosion, eutrophication or pollution of water bodies with chemicals, landscape homogenization and loss of biodiversity; for which solutions have not yet been found. Reuse of abandoned agricultural lands – which are abundant throughout the world – to address the rising demand for food is a potentially important alternative, which up to now has been widely ignored. To test the power of this alternative, equilibrium economic land allocation to various land-use practices by risk-avoiding tropical farmers in Ecuador was simulated. The reestablishment of pastures on abandoned cattle lands lowered prices for pasture products, and also triggered conversion of existing pasture into cropland. The resulting land-use change increased total annual food production in a moderate scenario from the current level of 17.8–23.1 petacalories (10¹⁵ calories), which amounted to a production increase of 30%. At the same time, there was a 19% reduction in the amount of payments to farmers required to preserve tropical forests – one of the world's greatest terrestrial carbon stores.     

Crop residue effects on aerodynamic processes and wind erosion

Summary This study focuses on both the mechanisms and degree of wind erosion control that various residue levels provide. First, scale parameters of Weibull wind-speed distributions at meteorological stations were modified to predict friction velocity distributions at eroding field sites. Simplified erosion prediction equations then were used to evaluate wind erosion on highly erodible, loose, sandy soils. Parameters for the erosion prediction equations were developed from wind tunnel data on soil loss and threshold friction velocities at various residue levels. Erosion-control mechanisms of flat residue include restricting soil emission from the surface and increasing threshold wind speeds. A minimum of 30 to 60 percent flat cover is needed to provide adequate control on highly erodible sands. The control level by flat residue can be increased by using short fields. Erosion-control mechanisms of standing residue include reducing the soil-surface friction velocity and intercepting saltating soil. Standing residue is more effective than flat residue, and 5 percent vertical silhouette area of standing residue per unit horizontal area provides adequate erosion-control in low and moderate wind regimes.Contribution from USDA, ARS in cooperation with Kansas Agricultural Experiment Station, Contribution Number 95-41-J.With 6 Figures     

Soil Carbon Sequestration in India

With a large land area and diverse ecoregions, there is a considerable potential of terrestrial/soil carbon sequestration in India. Of the total land area of 329 million hectares (Mha), 297 Mha is the land area comprising 162 Mha of arable land, 69 Mha of forest and woodland, 11 Mha of permanent pasture, 8 Mha of permanent crops and 58 Mha is other land uses. Thesoil organic carbon (SOC) pool is estimated at 21 Pg (petagram = Pg = 1 ×10¹⁵ g= billion ton) to 30-cm depth and 63 Pg to 150-cm depth. The soil inorganic carbon (SIC) pool is estimated at 196 Pg to 1-m depth. The SOC concentration in most cultivated soils is less than 5 g/kg compared with 15 to 20 g/kg in uncultivated soils. Low SOC concentration is attributed to plowing, removal of crop residue and other biosolids, and mining of soil fertility. Accelerated soil erosion by water leads to emission of 6 Tg C/y. Important strategies of soil C sequestration include restoration of degraded soils, and adoption of recommended management practices (RMPs) of agricultural and forestry soils. Potential of soil C sequestration in India is estimated at 7 to 10 Tg C/y for restoration of degraded soils and ecosystems, 5 to 7 Tg C/y for erosion control, 6 to 7 Tg C/y for adoption of RMPs on agricultural soils, and 22 to 26 Tg C/y for secondary carbonates. Thus, total potential of soil C sequestration is 39 to 49 (44± 5) Tg C/y.     

Impact of soil map specifications for European climate simulations

Soil physical characteristics can influence terrestrial hydrology and the energy balance and may thus affect land–atmosphere exchanges. However, only few studies have investigated the importance of soil textures for climate. In this study, we examine the impact of soil texture specification in a regional climate model. We perform climate simulations over Europe using soil maps derived from two different sources: the soil map of the world from the Food and Agricultural Organization and the European Soil Database from the European Commission Joint Research Center. These simulations highlight the importance of the specified soil texture in summer, with differences of up to 2 °C in mean 2-m temperature and 20 % in precipitation resulting from changes in the partitioning of energy at the land surface into sensible and latent heat flux. Furthermore, we perform additional simulations where individual soil parameters are perturbed in order to understand their role for summer climate. These simulations highlight the importance of the vertical profile of soil moisture for evapotranspiration. Parameters affecting the latter are hydraulic diffusivity parameters, field capacity and plant wilting point. Our study highlights the importance of soil properties for climate simulations. Given the uncertainty associated with the geographical distribution of soil texture and the resulting differences between maps from different sources, efforts to improve existing databases are needed. In addition, climate models would benefit from tackling unresolved issues in land-surface modeling related to the high spatial variability in soil parameters, both horizontally and vertically, and to limitations of the concept of soil textural class.     

Impact of refined land surface properties on the simulation of a heavy convective rainfall process in the Pearl River Delta region,China

The location and occurrence time of convective rainfalls have attracted great public concern as they can lead to terrible disasters. However, the simulation results of convective rainfalls in the Pearl River Delta region often show significant discrepancies from the observations. One of the major causes lies in the inaccurate geographic distribution of land surface properties used in the model simulation of the heavy precipitation. In this study, we replaced the default soil and vegetation datasets of Weather Research and Forecasting (WRF) model with two refined datasets, i.e. the GlobCover 2009 (GLC2009) land cover map and the Harmonized World Soil Database (HWSD) soil texture, to investigate the impact of vegetation and soil on the rainfall patterns. The result showed that the simulation patterns of convective rainfalls obtained from the coupled refined datasets are more consistent with the observations than those obtained from the default ones. By using the coupled refined land surface datasets, the overlap ratio of high precipitation districts reached 36.3% with a variance of 28.5 km from the observed maximum rainfall position, while those of the default United States Geological Survey (USGS) dataset and Moderate Resolution Imaging Spectroradiometer (MODIS) dataset are 17.0%/32.8 km and 24.9%/49.0 km, respectively. The simulated total rainfall amount and occurrence time using the coupled refined datasets are the closest to the observed peak values. In addition, the HWSD soil data has improved the accuracy of the simulated precipitation amount, and the GLC2009 land cover data also did better in catching the early peak time.     

四川省会理县风能资源分析研究

本研究利用四川省会理县测风塔短期2012年2月1日~2013年1月31日期间的70m高度实测逐时数据,经会理和会东气象观测站1981年1月~2010年12月共计30年的风速逐时数据采用长年代法订正推算后,对会理县该研究区域风能资源参数进行计算。结果表明:该区域风能资源应用于并网风力发电分别为“很好”和“好”的等级,具有较好开发潜力;风能和风向较为集中,有利于风机布设;测风塔地处高海拔地形较为平坦的山脊地带,不占用耕地,临近公路,气候较为温和,利于风电场修建。      

Current trends of rubber plantation expansion may threaten biodiversity and livelihoods

The first decade of the new millennium saw a boom in rubber prices. This led to rapid and widespread land conversion to monoculture rubber plantations in continental SE Asia, where natural rubber production has increased >50% since 2000. Here, we analyze the subsequent spread of rubber between 2005 and 2010 in combination with environmental data and reports on rubber plantation performance. We show that rubber has been planted into increasingly sub-optimal environments. Currently, 72% of plantation area is in environmentally marginal zones where reduced yields are likely. An estimated 57% of the area is susceptible to insufficient water availability, erosion, frost, or wind damage, all of which may make long-term rubber production unsustainable. In 2013 typhoons destroyed plantations worth US$ >250 million in Vietnam alone, and future climate change is likely to lead to a net exacerbation of environmental marginality for both current and predicted future rubber plantation area. New rubber plantations are also frequently placed on lands that are important for biodiversity conservation and ecological functions. For example, between 2005 and 2010 >2500 km² of natural tree cover and 610 km² of protected areas were converted to plantations. Overall, expansion into marginal areas creates potential for loss-loss scenarios: clearing of high-biodiversity value land for economically unsustainable plantations that are poorly adapted to local conditions and alter landscape functions (e.g. hydrology, erosion) – ultimately compromising livelihoods, particularly when rubber prices fall.