首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
This paper illustrates a methodology to quantify vegetation quality and its possible degradation in a large ‘shrinking’ Mediterranean city. Vegetation quality was estimated at three years (1960, 1990, 2006) in the Nuts-3 prefecture of Rome, central Italy (5355 km2) through the analysis of comparable land cover maps. The aims of this work are to assess how ‘compact growth’ and ‘sprawl’ impact on vegetation quality, and to monitor the territorial disparities observed in the vegetation quality as caused by urbanization and land use polarization. Built-up areas covered 3.3% and 12.9% of the investigated area in 1960 and 2006, respectively, with a dispersed to compact urban surface ratio passing from 1.2 to 1.9. Vegetation quality increased slightly during the investigated period with a diverging trend between urban and rural areas. As a consequence, territorial disparities in the same variable grew due to low-density urban diffusion in lowlands and depopulation with land abandonment and natural forestation in mountain areas.  相似文献   

2.
The Koshi River Basin is in the middle of the Himalayas, a tributary of the Ganges River and a very important cross-border watershed. Across the basin there are large changes in altitude, habitat complexity, ecosystem integrity, land cover diversity and regional difference and this area is sensitive to global climate change. Based on Landsat TM images, vegetation mapping, field investigations and 3S technology, we compiled high-precision land cover data for the Koshi River Basin and analyzed current land cover characteristics. We found that from source to downstream, land cover in the Koshi River Basin in 2010 was composed of water body (glacier), bare land, sparse vegetation, grassland, wetland, shrubland, forest, cropland, water body (river or lake) and built-up areas. Among them, grassland, forest, bare land and cropland are the main types, accounting for 25.83%, 21.19%, 19.31% and 15.09% of the basin’s area respectively. The composition and structure of the Koshi River Basin land cover types are different between southern and northern slopes. The north slope is dominated by grassland, bare land and glacier; forest, bare land and glacier are mainly found on northern slopes. Northern slopes contain nearly seven times more grassland than southern slopes; while 97.13% of forest is located on southern slopes. Grassland area on northern slope is 6.67 times than on southern slope. The vertical distribution of major land cover types has obvious zonal characteristics. Land cover types from low to high altitudes are cropland, forest, Shrubland and mixed cropland, grassland, sparse vegetation, bare land and water bodies. These results provide a scientific basis for the study of land use and cover change in a critical region and will inform ecosystem protection, sustainability and management in this and other alpine transboundary basins.  相似文献   

3.
Grasslands are the largest of the Earth's four major vegetation types and are among the most agriculturally productive lands. Grassland management practices alter biophysical factors, such as plant species composition, soil structure and chemistry, and primary productivity. Large-scale changes in land management practices can have significant impacts on available natural resources, therefore impacting a regional socioeconomics. For these reasons, an improved understanding of the geographic distribution of changing land management practices and how these changes affect grassland biophysical characteristics of an area is critical to improve land use planning and practices. This study investigated the spectral characteristics, as measured using satellite remotelysensed data, of three land management practices [grazing, haying, and management under Conservation Reserve Program (CRP)] on areas dominated by cool- and warm-season grasslands. The satellite imagery was acquired in May, July, and September in 1997 over Douglas County, Kansas. Biomass, vegetation cover, and species richness data were collected around the satellite overflight periods. Our results indicate that the biophysical characteristics and spectral reflectances are significantly different among the three management practices over cool- and warm-season grasslands. Interestingly, sites grazed by livestock had the highest species richness and the highest forb cover, although the total cover is almost the same as the other practices, and they have the highest near-infrared reflectance throughout the growing season.  相似文献   

4.
Zhuo G  Xin Li  Luo Bu  CaiYun Wang 《寒旱区科学》2011,3(5):0426-0435
This research investigates the recent distribution variation trends of vegetation in the Tibet region using Normalized Difference Vegetation Index (NDVI) data from 2000 to 2007. It also discusses the causes of vegetation degradation in typical regions (such as Nagqu) based on climatic conditions, human activity, and other influencing factors. Results show that the areas with the best vegetation cover are in Nyingchi and the southern part of Shannan, followed by Chamdo, the Lhasa area, and the eastern part of Nagqu. Vegetation in various regions exhibits significant seasonal differences. The vegetation status has improved in some parts of the Tibet region in the past few years, while the areas with the most serious degradation are in the middle and southern parts of the Nagqu region. On average, distinct vegetation degradation occurred between 2003 and 2006 in the whole Tibet region but vegetation has been increasing since 2006. The vegetation cover in summer basically determines the annual vegetation status. An increase in precipitation and decrease in wind speed generally corresponds to an increase in vegetation cover. The reverse is also true: a decrease in precipitation and increase in wind speed correspond to the decrease in vegetation cover. NDVI is thus positively related to temperature and precipitation but has a negative relation with wind speed. Increasing temperature and decreasing precipitation have led to the present vegetation degradation in Nagqu, and vegetation in all of these regions has been affected by growth of human population, intensified urbanization, livestock overgrazing leading to the proliferation of noxious plants, extraction of underground minerals and alluvial gold, extensive harvesting of traditional Chinese medicinal plants [e.g., Cordyceps sinensis, Caladium spp., and saffron crocus (Crocus sativus)], and serious rodent and other pest damage.  相似文献   

5.
The Norwegian area frame survey of land cover and outfield land resources (AR18X18), completed in 2014, provided unbiased statistics of land cover in Norway. The article reports the new statistics, discusses implications of the data set, and provides potential value in terms of research, management, and monitoring. A gridded sampling design for 1081 primary statistical units of 0.9 km2 at 18?km intervals was implemented in the survey. The plots were mapped in situ, aided by aerial photos, and all areas were coded following a vegetation type system. The results provide new insights into the cover and distribution of vegetation and land cover types. The statistic for mire and wetlands, which previously covered 5.8%, has since been corrected to 8.9%. The survey results can be used for environmental and agricultural management, and the data can be stratified for regional analyses. The survey data can also serve as training data for remote sensing and distribution modelling. Finally, the survey data can be used to calibrate vegetation perturbations in climate change research that focuses on atmospheric–vegetation feedback. The survey documented novel land cover statistics and revealed that the national cover of wetlands had previously been underestimated.  相似文献   

6.
Vertical differentiation of land cover in the central Himalayas   总被引:1,自引:0,他引:1  
Zhang  Yili  Wu  Xue  Zheng  Du 《地理学报(英文版)》2020,30(6):969-987
Characterized by obvious altitudinal variation, habitat complexity, and diversity in land cover, the Mt. Qomolangma region within the central Himalayas is one of the most sensitive areas to climate change in the world. At the same time, because the Mt. Qomolangma region possesses the most complete natural vertical spectrum in the world, it is also an ideal place to study the vertical structure of alpine land cover. In this study, land cover data for 2010 along with digital elevation model data were used to define three methods for dividing the northern and southern slopes in the Mt. Qomolangma region, i.e., the ridgeline method, the sample transect method, and the sector method. The altitudinal distributions of different land cover types were then investigated for both the northern and southern slopes of the Mt. Qomolangma region by using the above three division methods along with Arc GIS and MATLAB tools. The results indicate that the land cover in the study region was characterized by obviously vertical zonation with the south-six and north-four pattern of vertical spectrum that reflected both the natural vertical structure of vegetation and the effects of human activities. From low to high elevation, the main land cover types were forests, grasslands, sparse vegetation, bare land, and glacier/snow cover. The compositions and distributions of land cover types differed significantly between the northern and southern slopes; the southern slope exhibited more complex land cover distributions with wider elevation ranges than the northern slope. The area proportion of each land cover type also varied with elevation. Accordingly, the vertical distribution patterns of different land cover types on the southern and northern slopes could be divided into four categories, with glaciers/snow cover, sparse vegetation, and grasslands conforming to unimodal distributions. The distribution of bare land followed a unimodal pattern on the southern slope but a bimodal pattern on the northern slope. Finally, the use of different slope division methods produced similar vertical belt structures on the southern slope but different ones on the northern slope. Among the three division methods, the sector method was better to reflect the natural distribution pattern of land cover.  相似文献   

7.
There is a growing requirement for techniques to assess land susceptibility to wind erosion, i.e. land erodibility, over large geographic areas (>104 km2). This requirement stems from a lack of wind erosion research between the field (101 km2) and regional scales, and a need to evaluate the performance of spatially explicit wind erosion models across these scales. This paper addresses this issue by presenting a methodology for monitoring land erodibility at the landscape scale (103 km2). First, we define criteria suitable for evaluating land erodibility based on empirical relationships between soil texture, vegetation cover, geomorphology, and wind erosion. The criteria were used to visually assess land erodibility over long distances (103 km) using vehicle-based transects run through the rangelands of western Queensland, Australia. Application of the data for testing the performance of a spatially explicit land erodibility model (AUSLEM) is then demonstrated by comparing the visual assessments of land erodibility with the model output. The model performed best in the west of the study area in the open rangelands. In regions with higher woody shrub and tree cover the model performance decreases. This highlights the need for research to better parameterise controls on erodibility in semi-arid landscapes consisting of forested and rangeland mosaics.  相似文献   

8.
The objective of this paper is to examine a method for estimation of land cover statistics for local environments from available area frame surveys of larger, surrounding areas. The method is a simple version of the small-area estimation methodology. The starting point is a national area frame survey of land cover. This survey is post-stratified using a coarse land cover map based on topographic maps and segmentation of satellite images. The approach is to describe the land cover composition of each stratum and subsequently use the results to calculate land cover statistics for a smaller area where the relative distribution of the strata is known. The method was applied to a mountain environment in Gausdal in Eastern Norway and the result was compared to reference data from a complete in situ land cover map of the study area. The overall correlation (Pearson’s rho) between the observed and the estimated land cover figures was r = 0.95. The method does not produce a map of the target area and the estimation error was large for a few of the land cover classes. The overall conclusion is, however, that the method is applicable when the objective is to produce land cover statistics and the interest is the general composition of land cover classes - not the precise estimate of each class. The method will be applied in outfield pasture management in Norway, where it offers a cost-efficient way to screen the management units and identify local areas with a land cover composition suitable for grazing. The limited resources available for in situ land cover mapping can then be allocated efficiently to in-depth studies of the areas with the highest grazing potential. It is also expected that the method can be used to compile land cover statistics for other purposes as well, provided that the motivation is to describe the overall land cover composition and not to provide exact estimates for the individual land cover classes.  相似文献   

9.
This study examines interspecific differences in the architecture and field characteristics of the burrow systems of Brants' whistling rat, Parotomys brantsii, and Littledale's whistling rat, Parotomys littledalei. The two rodents are endemic to the arid west region of southern Africa. Both build complex burrow systems with numerous nest chambers and associated interconnecting tunnels, as well as a number of entrances. Burrow systems of P. littledalei are restricted to areas of good plant cover, whilst many P. brantsii burrows are situated in open locations with only limited plant cover. Further, the burrows of P. brantsii cover a much larger area than those of P. littledalei, with many more entrances. As P. brantsii feed predominantly within the boundaries of their burrows and not in the open veld, their burrow systems effectively serve as a predator refuge, into which this diurnal rodent can quickly run in the event of danger. Thus, by building large multi-holed burrow systems, P. brantsii have become independent of the protection offered by bush cover and can exist within relatively open areas within their distributional range. On the other hand, the reduced number of entrances to P. littledalei burrow systems may largely restrict this species to areas with adequate cover, including coastal and riverine bush, with which it is often associated.  相似文献   

10.
张镱锂  吴雪  郑度 《地理学报》2020,75(5):931-948
喜马拉雅山脉中段的珠穆朗玛峰等地,海拔高差巨大、生境复杂多变、土地覆被类型多样且植被垂直带谱完整,是全球范围内研究土地覆被垂直变化的理想场所。本文基于30 m空间分辨率的土地覆被数据(2010年)和DEM数据,在ArcGIS和Matlab平台的支持下,提出并运用脊线法、样带法和扇区法3种山地南北坡划分方法,研究了喜马拉雅山土地覆被垂直分布与结构差异。结果表明:① 山地土地覆被分布具有明确的垂直地带性结构特征,喜马拉雅中部土地覆被垂直带谱为南六北四式,土地覆被垂直带谱中具有人类活动的特点。② 南北坡之间的土地覆被垂直带谱差异明显,南坡土地覆被类型完整多样,北坡相对简单;对同类型土地覆被而言,南坡较北坡分布高程低、幅度宽。③ 依据各类型分布面积比随海拔变化情况,土地覆被类型在南北坡上的垂直分布可分为4种模式:冰川雪被、稀疏植被和草地为单峰分布型,裸地为南单峰北双峰分布型。④ 3种划分方法中,南坡的土地覆被垂直带结构具有相似性,而北坡的土地覆被垂直带结构存在差异,扇区法较好地反映了土地覆被自然分布格局。  相似文献   

11.
In Nepal, changing demographic patterns are leading to changes in land use. The high level of outmigration of men in the hills of Kaski District, Western Development Region of Nepal, is affecting the household structure but also land management. Land is often abandoned, as the burden on those left behind is too high. How do these developments affect the state of the land in terms of land degradation? To find out, we studied land degradation, land abandonment caused by outmigration, and existing sustainable land management practices in a subwatershed in Kaski District. Mapping was done using the methodology of the World Overview of Conservation Approaches and Technologies (WOCAT). While previous studies expected land abandonment to exacerbate slope erosion, we demonstrate in this paper that it is in fact leading to an increase in vegetation cover due to favourable conditions for ecosystem recovery. However, negative impacts are several, including the increase of invasive species harmful to livestock and a decline in soil fertility. Traditional land management practices such as terraces and forest management exist. To date, however, these measures fail to take account of the changing population dynamics in the region, making the question of how migration and land degradation are linked worth revisiting.  相似文献   

12.
Land managers need sound, evidence-based information about land degradation patterns and about the effectiveness of their management responses. Obtaining such information is particularly difficult in Mediterranean grazing lands and forests, where a long history of anthropogenic pressure, high topographical and climatic variability, and frequent disturbances combine to create a highly diverse and unstable environment.Our study aimed at designing a methodology to provide land managers in three data-scarce drylands in Spain, Greece, and Cyprus with spatially explicit, up-to-date information on the state of their land, the pressures driving land degradation, and the effectiveness of their management efforts using remotely sensed NDVI data. To translate NDVI values into a land degradation assessment, we analysed the variance of the annual average NDVI within different landscape units, which we identified based on land cover, aspect, and slope steepness parameters. After calibrating and validating the land degradation mapping methodology using field observations, we related the obtained land degradation patterns with spatial information about grazing and wildfire, as well as controlled grazing and afforestation practices.Our methodology proved useful to assess land degradation and management measures in dry, semi-natural ecosystems. It also provided insights into the role of landscape in modulating land degradation. Results indicate that grazing is a significant cause of land degradation even in partially abandoned areas; repeated fires have a negative impact; slope steepness increases the land's sensitivity to grazing; north- and east-facing slopes are less sensitive to fire in the long term than south- and west-facing slopes; and the effectiveness of responses to land degradation is substantially affected by land cover and topography.The methodology presented can be used to overcome the lack of spatially explicit information on the state of the land in drylands of the Mediterranean and beyond, or as a basis for more in-depth studies to plan restoration interventions.  相似文献   

13.
Using an integrated method combining wavelet analysis and non-parameter Mann-Kendall test, this paper analyzed spatial-temporal variations of vegetation cover in the Yellow River Basin based on SPOT-VEG images from 1998 to 2008. The results indicate: (1) Vegetation cover presented marked seasonal variation during the study period, with minima around winter and maxima in summer. The detail component D5 (with semi-period of 240 days) has presented a major contribution to the intra-annual variability. Forest vegetation presents a marked decreasing trend, while alpine shrubs, meadow, typical steppe, desert steppe, and forest (meadow) steppe vegetation all show a marked increasing trend. (2) Mean vegetation amount increased from the upper to lower reaches of the basin. It is low in the Ordos Plateau and Loess Plateau, and high in the southern Loess Plateau and the lower reaches. Amplitude of the annual phenological cycle presents an opposite pattern in spatial distribution with that of the mean vegetation amount. (3) Vegetation cover presented a dominant positive inter-annual change trend, which implies that the eco-environment in the region has steadily improved. Only a few areas show a negative trend, which are located in the upper reaches and the southern Loess Plateau.  相似文献   

14.
Geografisk Tidsskrift, Danish Journal of Geography 106(2): 115–130, 2006

This paper examines the relationship between the intensity of agricultural land use and the abundance and richness of trees and birds in a humid tropical developing region where natural vegetation is being rapidly converted into farmland under market and population pressures. We analysed survey data on land use, birds and woody plants collected in 14 study sites situated within smallholder cropland and commercial plantations in southern Uganda. Commercial plantations had very few trees and only 10% of the original bird species. Land use intensification in smallholder systems also showed losses in bird abundance and species richness, but not nearly as much as in plantations. In both systems the impact of intensification was much bigger on the specialised and threatened birds compared to the less specialised species. This argues strongly for ‘species-sensitive’ conservation policies combining protected areas with land use regulation in areas undergoing intensification. We also found a much higher loss in bird biodiversity during the first phases of land use intensification (when larger tracts of forest are cleared) than in later phases characterised by clearing of smaller patches of vegetation and improved management of farm trees. This suggests high pay-offs to geographical targeting of conservation efforts in farmed landscapes.  相似文献   

15.
刘宇  傅伯杰 《干旱区地理》2013,36(6):1097-1102
基于16 d合成MODIS NDVI数据提取的时间序列植被覆盖度数据,采用一元线性回归趋势分析,对黄土高原2000-2008年植被覆盖度的时空变化及其地形分异、土地利用/覆被变化的影响进行了定量分析。结果表明:(1)研究时段黄土高原植被覆盖度整体呈快速上升趋势,局部下降;(2)黄土高原植被覆盖度变化存在明显的地形分异,陡坡等植被恢复、重建和保育的主要区域植被覆盖度增速显著;(3)土地利用/覆被变化对植被覆盖度的增加影响突出,土地利用/覆被类型变更区植被覆盖度增速显著高于未变化区域,退耕还林还草区增速尤其突出;(4)土地利用/覆被类型未变化区域植被覆盖度总体上也呈增加趋势,但因植被覆盖度水平相对较高,增速明显低于土地利用/覆被类型变化区。上述结果表明,黄土高原植被保育、植被恢复和重建在植被覆盖度提升方面取得了明显成效。  相似文献   

16.
Long-term vegetation response to mesquite removal in Desert Grassland   总被引:1,自引:0,他引:1  
Forty-six years of vegetation response to mesquite removal at dry, low elevation sites on the Santa Rita Experimental Range in southern Arizona was only slightly different than the vegetation dynamics where mesquite trees were left intact. Only the density of threeawn grass species (Aristida spp.) was greater in the mesquite removal areas: and that difference persisted even after the cover of mesquite was no longer different between treatment and control areas. Cover of shrubs and perennial grasses, and density of all other perennial grasses did not differ between mesquite treatments throughout the study period. Mesquite cover on treated areas was not different than untreated areas 40 years after tree removal. The long-term results support the interpretation that vegetation dynamics at these dry locations, are not limited by the abundance of neighbouring mesquite. Alternatively, mesquite abundance is self-limiting at levels less than would influence grass abundance and precipitation anomalies may override any effects of neighbouring mesquite. Practically, these results suggest that areas with 350 mm year−1 of annual precipitation and <20% mesquite cover may have very little potential for increasing grass abundance through the removal of mesquite trees.  相似文献   

17.
Located in the foothills of the Indian Himalaya, Rajaji National Park was established to protect and enhance the habitat of the Asian elephant (Elephas maximus) and tiger (Panthera tigris). In 2002 the Van Gujjars, indigenous forest pastoralists, were voluntarily resettled from the Chilla Range (an administrative unit of Rajaji National Park) to Gaindikhata, a nearby area where they were granted land for agriculture. In this study we used a variety of remote sensing approaches to identify changes in land cover associated with the resettlement. The methods comprise two main approaches. First, we used object-based image analysis (OBIA) to identify the pre-resettlement land cover classes of use areas (representing agricultural expansion and adjacent areas of grazing, and collection of fuelwood and fodder) and recovery areas (representing areas where settlements were removed, and the adjacent areas of resource use). Secondly, we used trend analysis to assess the gradual and abrupt changes in vegetation that took place in use and recovery areas. To conduct the trend analysis we used BFAST (Breaks For Additive Season and Trend), which separates seasonal variation from long-term trends, and identifies breaks that can be linked back to disturbances or land cover changes. We found that the OBIA classification yielded high average class accuracies, and we were able to make class distinctions that would have been difficult to make using a traditional pixel-based approach. Pre-resettlement, the recovery areas were classified as mixed forest and riparian vegetation. In contrast, the use areas were classified primarily as grass dominated, brush dominated, and plantation forest, and were located relatively far away from riparian areas. Following the resettlement, the trend analysis showed a sudden change in the seasonal variation of NDVI in areas converted to agriculture. Areas neighboring the new agricultural land experienced sudden decreases in NDVI, suggestive of disturbances, at a higher rate than the same land cover types elsewhere. At the same time, these neighboring areas experienced a gradual overall increase in NDVI which could be caused by an expansion of leafy invasive shrubs such as Lantana camara in areas heavily used for biomass collection. The recovery areas also experienced a gradual increase in NDVI as well as sudden breaks to this trend, but we lacked evidence to connect these changes to the resettlement. Our findings support the claim that the resettlement has shifted pressure from more ecologically valuable to less ecologically valuable land cover types, and suggest that to some degree resource use pressure has increased outside the park. The study employs a novel synthesis of OBIA and trend analysis that could be applied to land change studies more broadly.  相似文献   

18.
The Atlantic Forest biome has only 13 percent of its pristine vegetation cover left. This article analyzes the consequences of land changes on forest cover in the Paraíba Valley, São Paulo state, Brazil, from 1985 to 2011. Multitemporal satellite image classifications were carried out to map eight land use and land cover classes. The forest cover increased from 2,696 km2 in 1985 to 4,704 km2 in 2011, mostly over areas of degraded pastures. The highest rates of afforestation were observed within protected areas around eucalyptus plantations. On the other hand, deforestation processes were concentrated on areas covered by secondary forests. Socioeconomic changes taking place in particular Brazilian settings, such as industrialization and agricultural modernization, allied to the Paraíba Valley's natural biophysical constraints for agricultural production, have led the region to experience a remarkable case of forest transition.  相似文献   

19.
Vegetation changes in the Jornada Basin from 1858 to 1998   总被引:1,自引:1,他引:1  
Notes made by land surveyors in 1858 were utilized to estimate cover of grasses and shrubs on the Jornada Experimental Range (JER) and the Chihuahuan Desert Range Research Center (CDRRC) in the northern Chihuahuan Desert in southern New Mexico, USA. Portions of these areas have been previously assessed for historical vegetation dynamics but the entire 84,271 ha assessed in the 19th century has not been examined in total. In 1858, fair to very good grass cover occurred on 98% and 67% of the JER and CDRRC, respectively. Shrubs were present throughout both properties but 45% of the JER and 18% of the CDRRC were shrub free. Reconnaissance surveys, made to determine carrying capacity for livestock were made in 1915–1916 and 1928–1929 on the JER and in 1938 on the CDRRC, show that shrubs had made large increases in area occupied at the time of the surveys. Vegetation type maps were made of both properties in 1998. Mesquite (Prosopis glandulosa) was the primary dominant on 59% of the JER in 1998 and creosotebush (Larrea tridentata) was the primary dominant on 27% of the area. On the CDRRC mesquite and creosotebush were primary dominants on 37% and 46% of the area, respectively. Grass cover has decreased greatly with the increase in shrubs and only shrub control efforts have maintained the once abundant black grama (Bouteloua eriopoda) as a primary dominant on 1% or less of the area on both properties.  相似文献   

20.
Soil degradation is perceived as a major threat in the Mediterranean region due to changes in land-use and possible future climate change. Soil aggregation parameters are used here to demonstrate their potential as a key-indicator for land degradation studies. The monitoring of these indicators offers a means of establishing the vulnerability and resilience of geo-ecosystems. Soil aggregation stability and distribution were studied on soils with an open shrubby vegetation cover, from several places in southeastern Spain and southern France, by applying drop tests and determining aggregate size distributions. Aspect and vegetation cover were incorporated in the soil sampling. Several indices were derived from these analyses to indicate the degree of soil aggregation. This was done by referencing to a base level of aggregation (bare soil aggregation). It was found that soil aggregates were more stable and were often coarser under vegetation, when compared to their immediate surrounding bare areas. A similar, slightly less clear effect was noted on N-facing exposed slopes when compared to S-facing exposed slopes. Long-term changes were found by studying cultivated land, abandoned fields and land covered by semi-natural vegetation, on comparable substrate and comparable land units. It is clear that soil aggregation and aggregate stability increases with time (years). It is argued that soil aggregation indices can be used as a key-indicator for degradation processes at a fine scale with implications for runoff and sediment generating processes at the hillslope scale.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号