Global change pressures on soils from land use and management

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land‐use change, land management and land degradation (erosion, compaction, sealing and salinization). The intensity of land use also exerts a great impact on soils, and soils are also subject to indirect impacts arising from human activity, such as acid deposition (sulphur and nitrogen) and heavy metal pollution. In this critical review, we report the state‐of‐the‐art understanding of these global change pressures on soils, identify knowledge gaps and research challenges and highlight actions and policies to minimize adverse environmental impacts arising from these global change drivers. Soils are central to considerations of what constitutes sustainable intensification. Therefore, ensuring that vulnerable and high environmental value soils are considered when protecting important habitats and ecosystems, will help to reduce the pressure on land from global change drivers. To ensure that soils are protected as part of wider environmental efforts, a global soil resilience programme should be considered, to monitor, recover or sustain soil fertility and function, and to enhance the ecosystem services provided by soils. Soils cannot, and should not, be considered in isolation of the ecosystems that they underpin and vice versa. The role of soils in supporting ecosystems and natural capital needs greater recognition. The lasting legacy of the International Year of Soils in 2015 should be to put soils at the centre of policy supporting environmental protection and sustainable development.     

快速城镇化过程中的城市蔓延与生态保护冲突空间识别与量化评估——以长三角生态绿色一体化发展示范区为例

如何解决社会经济发展与生态环境保护之间的矛盾是实现区域和城市可持续发展的首要问题,表现在空间上就是城市无序蔓延与生态环境保护用地的冲突,本质上是建成区与非建成区的生态系统之间的冲突。以长三角生态绿色一体化发展示范区为例,基于自然环境因子和社会经济因子构建城市蔓延风险空间量化评估模型,得到城市蔓延风险空间分布并提取城市蔓延严重风险区;利用生态侵蚀度指数识别评估生态保护压力空间并提取生态保护压力高值区。根据城市蔓延严重风险区与生态保护压力高值区的重合空间,对城市无序蔓延与生态保护的冲突程度进行分析,进而探讨快速城镇化发展过程中二者的协调关系,为城市国土空间规划与区域生态保护决策提供科技支撑。长三角生态绿色一体化发展示范区案例研究结果表明:(1)城市蔓延的严重风险区与生态保护压力高值区的重合面积达到583.83km~2;其中较高风险区与侵蚀度高的地区重合面积为311.73km~2,冲突度为53.39%;高风险区与侵蚀度高的地区重合面积为47.70 km~2,冲突度为8.17%。(2)示范区内各类生态系统中,耕地生态系统受城市蔓延冲突程度均为最高,其在较高和高风险区的占比分别为91.58%、8...     

页岩气开发对植被和土壤的影响研究进展

页岩气开发和生产过程影响水资源与水质、土地利用与植被覆盖、土壤侵蚀与土壤质量。综述了页岩气开发和生产过程可能存在的生态环境影响,并重点评价了国际上不同区域页岩气开发和生产对土地利用和植被覆被变化、景观破碎化的影响,以及对土壤侵蚀和土壤质量的影响。研究发现页岩气开发平台、运输道路和管线占用农田、牧场、森林,造成不同程度的景观破碎化,在坡地开发页岩气会导致土壤侵蚀与沉积风险增大。截止2015年末,在我国重庆涪陵焦石坝页岩气产建区55.8%的面积(146.56 km~2)存在土壤侵蚀和石漠化生态风险。我国页岩气开发区水基钻屑固化填埋未对周边土壤造成污染。建议页岩气开发设计应考虑占地、景观破碎化的影响,并及时开展页岩气开发暂时占地的复垦工作。     

广东小良水保站三种生态系统地表侵蚀的研究

在系统地研究了广东小良水保站的混交林,桉树林,裸地等三种生态系统类型的水文效益以后,本文着重探讨了它们的水土保持效益。结果表明裸地的降雨侵蚀率分别是桉树林的５．２倍,是混交林的２２８．１倍;径流侵蚀率裸地是桉树林的１１．３倍,是混交林的３１．９倍。从总体上来看,无论是降雨侵蚀率还是径流侵蚀率都是混交林的最小,而且从侵蚀物的组成来看,混交林地表径流中的悬浮物占较大的比重。侵蚀物与降雨量存在ｘ＝ｆ（ＰＡ）的相关关系,Ａ的大小反映了降雨对侵蚀的影响程度,不同的土壤是不同的,混交林Ａ＜１,桉树林Ａ＝１．４８,裸地Ａ＝１．８５,侵蚀率的年间变化以混交林的最大。用灰色系统的ＧＭ（２,１）模型,本文较为成功地预测了年际间的侵蚀率。     

辽宁省土地退化与景观生态建设

利用1997－1998年1：25万辽宁省TM遥感影像及相应的GIS获取的数据,调查分析了辽宁省土壤侵蚀,土地沙化和盐渍化3种类型土地退化程度,面积和分布,结果表明,全省92．52％的土地面积遭受不同程度的侵蚀,3．39％的土地为沙化土地,2．22％土地为盐渍化土地,在此基础上,以新的角度进行全省地土地退化分区,现代侵蚀退化区,地质侵蚀退化区和沙化盐渍化退化区,分析不同区域内不同类型的退化特点和原因,依据区域自身特点和景观生态学原理,提出相应的景观生态建设恢复治理模式。     

生态安全条件下土地利用格局优化——以皇甫川流域为例

在人类活动导致的生态环境问题中,土地利用格局变化对区域生态安全起着决定性作用。选择我国乃至在世界上都罕见的多沙、粗沙、强烈水土流失的黄河皇甫川流域作为研究区域,针对土壤侵蚀和生态用水这两大影响流域生态安全的关键问题,开展土地利用变化模拟、土壤侵蚀3S监测、适宜植被盖度估算、土壤侵蚀情景模拟、土地利用格局优化等方面的综合研究。结果表明:(1)土地利用格局变化是导致土壤侵蚀变化的重要因素。从1987年到2015年,建筑用地、林地和灌丛面积增加,水域、沙地和裸砒砂岩面积减少,导致流域年平均土壤侵蚀模数由16160.72 t km-2a-1降至9710.72 t km-2a-1。(2)土地利用类型与土壤侵蚀模数密切相关并存在一定规律。6种不同土地利用类型多年平均土壤侵蚀模数的大小顺序为:裸砒砂岩沙地耕地草地林地灌丛,表明灌、林措施是流域植被恢复和土壤侵蚀减少的首选。(3)土地利用结构和空间格局优化有助于提升区域生态安全水平。在优化格局下,2007年和2015年土壤侵蚀模数比优化前分别减少5469.57 t km-2a-1和5432.77 t km-2a-1,优化后2015年土壤侵蚀模数仅为4277.95 t km-2a-1,低于流域自然侵蚀临界值或允许土壤侵蚀模数5300 t km-2a-1,优化土地利用格局成为加强流域生态环境建设的重要途径。     

Carbon storage capacity of semi‐arid grassland soils and sequestration potentials in northern China

Organic carbon (OC) sequestration in degraded semi‐arid environments by improved soil management is assumed to contribute substantially to climate change mitigation. However, information about the soil organic carbon (SOC) sequestration potential in steppe soils and their current saturation status remains unknown. In this study, we estimated the OC storage capacity of semi‐arid grassland soils on the basis of remote, natural steppe fragments in northern China. Based on the maximum OC saturation of silt and clay particles <20 μm, OC sequestration potentials of degraded steppe soils (grazing land, arable land, eroded areas) were estimated. The analysis of natural grassland soils revealed a strong linear regression between the proportion of the fine fraction and its OC content, confirming the importance of silt and clay particles for OC stabilization in steppe soils. This relationship was similar to derived regressions in temperate and tropical soils but on a lower level, probably due to a lower C input and different clay mineralogy. In relation to the estimated OC storage capacity, degraded steppe soils showed a high OC saturation of 78–85% despite massive SOC losses due to unsustainable land use. As a result, the potential of degraded grassland soils to sequester additional OC was generally low. This can be related to a relatively high contribution of labile SOC, which is preferentially lost in the course of soil degradation. Moreover, wind erosion leads to substantial loss of silt and clay particles and consequently results in a direct loss of the ability to stabilize additional OC. Our findings indicate that the SOC loss in semi‐arid environments induced by intensive land use is largely irreversible. Observed SOC increases after improved land management mainly result in an accumulation of labile SOC prone to land use/climate changes and therefore cannot be regarded as contribution to long‐term OC sequestration.     

Reducing soil erosion and the loss of soil fertility for environmentally-sustainable agricultural cropping and livestock production systems

My proposals for reducing soil erosion are based on my experience of assessing erosion, largely in Britain, both of cultivated land and of upland grazings. I have assessed the extent and rates of erosion in the field mostly by using easily‐ and rapidly‐used photographic and measurement techniques, rather than by using experimental plots set up either in the field or laboratory which overstate erosion. Policies which have governed the economics of agricultural production have also been examined. Much of the increase in occurrence of runoff and soil erosion in Britain is due to changes in land use and in intensity of use since the Agriculture Act was passed in 1947, and especially since joining the Common Market in 1973, with its even greater emphasis on paying for increased production. The increasing numbers of animals grazing the land, especially sheep, led to the initiation and erosion of bare soil in the uplands and to trampling and puddling of soils in lowland pastures. There is evidence that runoff from the land, and sedimentation of water courses have also increased. In the cultivated lowlands, the expansion in area of land drilled to winter cereals, the increase in area of land sown to maize or used to rear outdoor pigs, changes in farming techniques, and larger machines working in larger fields can explain much of the increase in erosion. Reversing some of these changes, for example by lowering the intensity of grazing and inserting grass (set‐aside) into the arable rotation will reduce the extent of erosion. Other techniques to reduce erosion are well‐known but need national and international agricultural policies that improve farmers' incomes to bring them into use. In developed countries, erosion need not reduce soil fertility, as nutrients removed from the soil by animals or crops can be affordably replaced. This may not be so in other parts of the world. Education of farmers also has a vital role to play in persuading them to use the land more sustainably, for many of the impacts of erosion such as flooding and pollution of water supplies bear on society as a whole, not just farmers who are themselves little affected. The principles devised to reduce erosion in developed countries are likely to be successful in developing countries. However, it may take many years for better and more sustainable agricultural policies at national and international level to be devised and brought into being.     

Agro-ecological field vulnerability evaluation and climate change impacts in Souma area (Iran), using MicroLEIS DSS

Soil erosion and contamination are two main desertification indices or land degradation agents in agricultural areas. Global climate change consequence is a priority to predict global environmental change impacts on these degradation risks. This agro-ecological approach can be especially useful when formulating soil specific agricultural practices based on the spatial variability of soils and related resources to reverse environmental degradation. Raizal and Pantanal models within the new MicroLEIS framework, the Ero&Con package, are database/expert system evaluation approach for assessing limitations to land use, or vulnerability of the land to specified agricultural degradation risks. This study was performed in Souma area with approximately 4100 ha extension in the North-West of Iran (west Azarbaijan). Based on 35 sampling soils, Typic Xerofluvents, Typic Calcixerepts, Fluventic Haploxerepts and Fluventic Endaquepts were classified as main subgroups. Climatological data, referred to temperature and precipitation of more than 36 consecutive years were collected from Urmieh station reports and stored in monthly Climate Database CDBm, as a major component of MicroLEIS DSS (CDBm) program. Climate data for a hypothetical future scenario were collected from the Intergovernmental Panel on Climate Change (IPCC) reports for the 2080s period. The evaluation approach predicts that attainable water erosion vulnerability classes were none (V1) very low (V2) and moderately low (V4) in the total of 72%, 13% and 15% of the Souma area, respectively and they will not affected by climate change. On contrary, attainable wind erosion vulnerability classes will increase. Also, phosphorous and heavy metal contamination vulnerability risks will not differ in two compared scenarios while nitrogen and pesticides vulnerability classes will be improved.     

Determining the Pattern of Oak Woodland Regeneration for a Cleared Watershed in Northwest California: A Necessary First Step for Restoration

Historically, oak woodlands of northern California have been subject to intensive tree and brush removal efforts to improve land for livestock grazing. As a result of this tree removal, these watersheds are susceptible to soil erosion and stream degradation. Therefore, planting woody vegetation is often required to restore watershed function. Prior to such actions, a thorough understanding of natural vegetation regeneration patterns is essential. The physical and biological attributes of natural vegetation regeneration in a cleared watershed were characterized using remote sensing, a Geographic Information System, and field surveys. A 79‐ha watershed at the University of California's Hopland Research and Extension Center was examined because the clearing of vegetation was part of a well‐documented experiment in the early 1960s, providing essential baseline data. The results of this study reveal that significantly more oak regeneration, consisting mostly of evergreen oaks, occurred on moister and steeper northerly slopes. Deciduous oaks, located primarily on drier and less steep southerly slopes, have not regenerated. Hardwood regeneration was associated with Josephine, Los Gatos, and Maymen soils. The distribution of hardwood regeneration is clustered, suggesting that the presence of other trees may promote regeneration. These results also suggest that without active restoration efforts such as tree planting and seedling protection, southerly slopes will most likely remain barren and erosion will continue, while northerly slopes and riparian areas will recover under the current land management practices. Despite some woody plant regeneration, the once densely forested watershed is now predominantly grassland, emphasizing the need to minimize clearing of California oak woodlands.     

黄土丘陵小流域土壤侵蚀的时空变异及其影响因子

采用土壤侵蚀模型LISEM(Limburg Soil Erosion Model)模拟黄土丘陵沟壑区大南沟小流域5种土地利用格局下立地尺度上土壤侵蚀量的空间分布,从土壤侵蚀量与环境因子的关系分析入手,研究黄土丘陵小流域立地尺度上土壤侵蚀的时空变异性及其影响因子.研究结果表明,立地尺度上平均土壤侵蚀强度以1975年>1998年>退耕格局,可见优化土地利用格局(陡坡农地退耕)可以有效地降低立地尺度上的土壤侵蚀强度.各种土地利用方案下土壤侵蚀强度的空间变异都很显著,相对来说以1975年<1998年<退耕格局,可见优化土地利用格局可以提高土壤侵蚀的空间变异性,降低土壤侵蚀危险的空间聚集度.土壤侵蚀量与降雨呈现显著正相关性,相关性以LU75>LU98>退耕格局,可见合理的土地利用格局可以有效地削弱降雨对土壤侵蚀强度的影响.土地利用方式对土壤侵蚀空间分布具有显著影响.从1975年、1998年到3种退耕格局,陡坡农地退耕还林还草,植被覆盖度增加,林地/灌木地、果园/经济林地、农地和休闲地的平均土壤侵蚀强度都逐渐降低.相关分析表明,林地/灌木地上土壤侵蚀量最小,荒草地相对最严重;果园、休闲地和农地居中.土壤侵蚀强度还存在显著的地形分异.水平凹凸度和相对海拔对土壤侵蚀空间分布的影响比较显著,而坡向、坡度和垂直凹凸度的影响较小.土壤侵蚀强度以水平凸坡大于水平凹坡、垂直凹坡略大于垂直凸坡、偏南坡大于偏北坡、低海拔大于高海拔.对1975年和1998年土地利用格局来说,土壤侵蚀强度以偏西坡大于偏东坡、陡坡大于缓坡;对3种退耕格局而言则正相反.可见,优化土地利用格局(陡坡农地退耕),可以有效地削弱甚至逆转地形对土壤侵蚀强度的影响.     

The Risk of Peat Erosion from Climate Change: Land Management Combinations—An Assessment with Bayesian Belief Networks

Modeling risk factors to soils is constrained by the lack of key data and understanding that explicitly and quantitatively link specific threats to risk. Peat erosion results from the complex interaction of climatic, topographic, and anthropogenic influences acting over a long period of time. With numerous contemporary factors operating to perpetuate the erosion processes, it is often difficult to identify with certainty what actually are the initial and subsequent drivers of erosion. In this situation, expert opinion forms a vital source of information. Here we demonstrate how Bayesian Belief Networks (BBN) can be used to combine quantitative data from the National Soils Inventory of Scotland (NSIS) with qualitative expert knowledge to estimate risk of peat erosion in Scotland. This model was used to identify the main factors associated with peat erosion. It was shown that climatic variables (increased temperature, decreased precipitation) are the most important risk factors for perpetuating peatland erosion. However, the BBN approach also indicated that maintaining good vegetation cover is a significant mitigating factor. It would follow that land management practices that impact negatively on vegetation cover would also exacerbate peatland erosion given a hot dry climate.     

红壤坡地不同土地利用方式土壤侵蚀的时空分布规律研究

应用定位土芯Eu(Europium)示踪新方法 ,研究红壤坡地不同土地利用方式下土壤侵蚀的时空分布规律 .结果表明 ,新方法对以片蚀和细沟侵蚀为主的红壤坡地是适用的 ;土壤侵蚀的时间分布与降雨量的年时间分布相一致 ,过程性暴雨期表现为全年土壤侵蚀的高峰期 ;在复合坡面 ,随坡面的陡、缓、凹 ,土壤侵蚀表现强、弱、沉积 ;相同坡度和坡长条件下 ,幼龄板栗园的土壤侵蚀速率 >雷竹园 >稀疏马尾松林地 >茶园 .     

土壤侵蚀与土地利用方式对黑土地土壤水气传输特性的影响

土壤侵蚀是东北黑土退化的主要原因之一,了解不同土地利用方式下土壤水气传输性质的差异,可以为黑土区水土资源的高效利用和保护提供科学依据。本研究选取东北黑土区典型的3种土地利用方式(农地、林地、撂荒地)进行0~5 cm土层原位土壤饱和导水率、导气率和相对气体扩散率的测定,探讨土壤侵蚀和土地利用方式对土壤水气传输性质的影响。结果表明:不同侵蚀程度农地之间以及不同土地利用方式之间土壤水气传输性质差异显著。重度侵蚀农地容重显著高于其他样地,未侵蚀农地容重显著低于其他样地。与未侵蚀农地相比,轻度、中度和重度侵蚀农地容重分别增加12.7%、17.6%和39.2%,饱和导水率分别降低84.4%、53.7%和12.7%,导气率分别降低94.6%、64.4%和14.0%,相对气体扩散率分别降低91.3%、82.6%和4.3%。松林地饱和导水率、导气率和相对气体扩散率较未侵蚀农地分别降低86.5%、83.0%和91.3%。沙棘林地饱和导水率、导气率和相对气体扩散率较未侵蚀农地分别降低51.7%、45.6%和82.6%,撂荒地饱和导水率、导气率和相对气体扩散率较未侵蚀农地分别降低16.2%、1.4%和73.9%。可以利用测得的土壤导气率、相对气体扩散率估算土壤饱和导水率。土壤侵蚀和土地利用方式显著影响黑土地土壤水气传输特性。     

神木市生态安全格局构建与生态问题定量诊断

黄河流域生态保护和高质量发展是重大的国家战略,县域生态安全格局构建与生态问题定量诊断是实施生态保护修复的最基本单元。以神木市为研究对象,首先,基于电路理论构建神木市生态安全格局,将识别出的生态夹点、生态障碍点和低质量生态空间作为生态修复关键区域;其次,通过构建生态问题指标体系,在生态修复关键区域内定量化诊断现存生态问题;最后,通过生态问题指数(EPI)测算结果划定生态修复分区。研究表明：(1)神木市生态源地面积为411.64km²,以草地为主,主要分布在中部、东部和南部地区,源间生态廊道共63条,总长度约610.71km,中部地区的生态廊道较东南部密度大。(2)基于生态安全格局识别的生态修复关键区域包括生态夹点415个,面积达30.55km²;生态障碍点341个,面积共计25.72km²;低质量生态空间面积为1043.73km²。(3)生态修复关键区域内土壤侵蚀主要以微度侵蚀为主;地质灾害多发于采矿区以及黄土丘陵沟壑区;水源涵养低值区主要分布在低质量生态空间;林地和草地的退化程度呈现东部较中部和西南...     

Tracking changes in the land use,management and drainage status of organic soils as indicators of the effectiveness of mitigation strategies for climate change

The tracking of land use since 1990 presents a major challenge in greenhouse gas (GHG) reporting under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol because there is often limited availability of data, especially for the base year of 1990. There is even less land management and soil moisture data, which are needed to track climate change mitigation activities since soil moisture is one of the main drivers of GHG emissions of organic soils. Information is also needed for the reporting of land-based activities such as grazing land management or wetland drainage and rewetting of organic soils. Different spatial and thematic resolutions of land-use data produce inconsistent time series with a strong overestimation of land-use change (LUC) if not adequately accounted for. Our aim was to create a consistent time series of land use since 1990 that is in line with GHG reporting under the UNFCCC and the Kyoto Protocol by combining official cadastral data with colour-infrared aerial photography used for biodiversity monitoring in six federal states in northern and eastern Germany. We developed a generic hierarchical classification by land use, management and drainage status, and a translation key for data harmonisation into a consistent time series. This time series enabled the quantification of LUC on organic soils between 1992 and 2013 in a spatially explicit manner. Furthermore we used this time series to develop indicators for changes in land management and drainage to evaluate the success of protection statuses on peatland restoration.The study area encompassed one million hectares, half of which had some type of legal nature protection status. Areas with no protection status tended to become more intensively farmed and drier, while highly protected areas (e.g. Natura 2000) showed the opposite trend. Land-use trends also differed greatly between federal states. In Schleswig-Holstein organic soils tended to become drier during the study period, while in Mecklenburg-Western Pomerania they tended to become wetter overall. The trends and differences in LUC between federal states were linked to German reunification, changes in the European Common Agricultural Policy (CAP) and Germany's Renewable Energy Act (EEG). A large-scale peatland protection programme also had major impact.In conclusion, our study demonstrates how data derived for biodiversity monitoring and other highly detailed land-use data can be used to track changes in land use, management and drainage status in accordance with the reporting requirements under the UNFCCC and the Kyoto Protocol.     

汉江流域景观格局变化对土壤侵蚀的影响

在流域尺度上,景观格局变化是决定土壤侵蚀程度的重要因素。以汉江流域为研究区域,基于2000—2015年四期土地利用类型数据及环境气象数据,运用中国土壤流失方程和逐步回归法,探究景观格局变化对土壤侵蚀的影响。结果表明:(1)在2000—2015年间,汉江流域土壤侵蚀量下降,高值区分布在流域中部草地区,低值区分布在流域东西两侧的林地和耕地区。不同坡度下各等级土壤侵蚀量不同,侵蚀量最大值出现在10—30°的坡度范围内。(2)研究期间,汉江流域的景观破碎化程度加强,斑块形状趋于简单,各斑块自身连通性增强,景观类型空间分布均匀。(3)汉江流域土壤侵蚀量与斑块密度和平均邻接度指数呈正相关,与蔓延度指数和香农均匀度指数呈负相关,即景观破碎度越高、连通性越差,土壤越容易遭受侵蚀,反之则不易受到侵蚀;研究表明景观格局变化对土壤侵蚀有显著影响,结果可为流域尺度景观管理与水土保持研究提供参考。     

Analysis of land consolidation projects and their impact on land use change,landscape structure,and agricultural land resource protection: case studies of Pilsen-South and Pilsen-North (Czech Republic)

Within the countries of the former socialist bloc, the changes in the politico-economic system at the end of the 1990s created a situation where it was (and still is) necessary to restore agricultural land resource property rights, to adjust the structure of agricultural land to current needs and to improve the current state of environmental resources. This case study covers 19 cadastral areas in the western part of the Czech Republic that were affected by the land consolidation process during 2000–2006. The main task of this study was to document how land consolidation processes could affect the change of land use and landscape structure and whether the land consolidation planners take into account the protection of natural resources. The increased acreage of grasslands was the most important change which has occurred in the land use in the 19 analysed cadastral areas, before and after land consolidations. In the studied area, the changes of land use involved 6.8 % of the total land consolidation area. This area of grassland significantly increased the protection of agricultural land from water erosion. In terms of changes in the landscape structure, the construction of new field road networks is the most important result. The results confirm the importance of land consolidation processes not only for the organization and recovery of ownership and cadastral records but also for the improvement of agricultural use of landscape and protection of natural resources such as soil, water and plant and animal communities.     

黄丘区特色治理开发小流域土壤侵蚀变化对景观格局演变的响应

研究土壤侵蚀与景观格局变化的关系对小流域的治理开发具有重要的指导意义。本研究以实施退耕还林草、生态农业、生态旅游及科技示范的黄土高原安塞南沟特色治理小流域为研究对象,基于GIS平台和通用土壤流失方程,分析小流域1981—2018年景观格局和土壤侵蚀量的时空演化特征,并利用主成分回归法,从斑块类型水平和景观水平两个尺度分析土壤侵蚀模数与3类9个景观格局指标的关系。结果表明: 研究期间,在5种景观类型中,耕地和林地面积的时空变化主导了南沟小流域景观格局的演化,并且影响整个小流域的聚集分散程度;南沟小流域的土壤侵蚀量逐年减少,1981—2018年土壤侵蚀面积减少29.7%,侵蚀模数减少61.2%,且有73.4%的区域土壤侵蚀强度减轻;耕地和林地面积的变化决定了整个小流域土壤侵蚀模数的变化,其景观格局指数的变化方向与该景观类型土壤侵蚀的变化方向一致;退耕还林草工程是流域景观格局变化、土壤侵蚀减轻的主要原因,特色开发治理可以减弱局部地区土壤侵蚀强度。景观类型的合理化配置能有效地防治小流域土壤侵蚀,将其与特色治理开发相结合有助于实现小流域可持续高质量发展。     

Effects of soil erosion on crop productivity

Soil erosion and the effects of soil erosion on crop productivity have become emotional issues and have attracted the attention of agriculturists, environmentalists, and the public in general. In spite of heavy investments in research and development, the global rates of accelerated erosion are now presumbly higher than ever before. However, the data from available records obtained by diverse methods are uncomparable, unreliable, confusing, and often vary by several orders of magnitude. Reports of erosion‐caused alterations in crop productivity and soil properties are also contradictory and subjective. In addition to the lack of standardized methodology in evaluating soil erosion and its effects on crops, controversial interpretations are attributed to differences in soil profile characteristics, nutrient status, crops grown, and prevailing climatic conditions. Although erosion is generally associated wtih yield reductions, there are examples of where soil erosion has had no effect or has had a positive effect on crop production. Accelerated erosion affects productivity both directly and indirectly. Directly, the erosion‐induced reduction in crop yields is attributed to loss of rooting depth, degradation of soil structure, decrease in plant‐available water reserves, reduction in organic matter, and nutrient imbalance. Depending on soil properties and the degree of degradation, adverse effects of erosion on crop yields can be mostly compensated for by additional inputs of macronu‐trients (N, P, K) and macronutrients plus organic matter, by supplemental applications of some micronu‐trients, and by irrigation. For some soils, e.g., tropical soils, crop yields from severely eroded soils are significantly lower than those from uneroded lands and are often uneconomic in spite of additional inputs. Specific examples of yield alterations are given in relation to the loss of plant nutrients, soil water reserves, and alterations in soil properties. Criteria for soil‐loss tolerance are discussed, and productivity restoration of eroded soils is reviewed in relation to soil organic matter content and nutrient requirments. Research and development priorities are presented.