Impacts of historical land use changes on erosion and agricultural soil properties in the Kali Basin at Lake Balaton,Hungary

Historical land use changes may have significant impact on erosion and agricultural soil properties, including soil degradation by acidification, nutrient leaching and organic matter depletion. The Kali Basin study area, a small catchment of high landscape value located in a national park at Lake Balaton, Hungary, with its historical agricultural records, together with the available unique historical land use data for the last 200 years, provides an opportunity to study and model impacts of historical land use changes on erosion and agricultural soil properties. Comparison of long-term land uses with present soil degradation indicator parameters showed that permanent arable land use has led to degradation of both the physical and chemical properties of soils in the Kali Basin. Application of the SEDEM/WATEM distributed erosion and sediment transport model showed that, despite the low overall sediment export from the catchment, land use changes introduced by property ownership and agricultural changes have decreased average soil erosion in the catchment but increased relative sediment export to Lake Balaton. This is due to changes in the land cover pattern that allow more sediment transported to the river system. The overall conclusion of this study is that besides the size and area proportion of land use types, land use pattern seems to be equally important in soil erosion and degradation processes, thus land use pattern is a key factor for landscape planning and development in the Kali Basin. A relationship between the sociological and agro-ecological reasons for the recorded land use changes is also shown in this study.     

Implications of decadal changes in precipitation and land use policy to soil erosion in Basilicata,Italy

This paper examines the implications of changes in precipitation and land use to soil erosion from 1955 to 2002 in Basilicata, a hilly portion of southern Italy. Analysis of daily precipitation records reveals statistically significant trends using both non-parametric and parametric approaches. The inter-annual variability of precipitation increases in intensity; primarily between October and January. From 1955 to 2000, the length of dry spells greatly increased, while wet days decreased. A land use change map was produced for the three study areas using aerial photos (1955) and orthophotos (1997 and 2002), integrated with field surveys. Results show that land use is highly dynamic in Basilicata, especially due to the application of the European Union's Common Agricultural Policy (CAP) measures. The EU policies resulted in reclamation of badlands and degraded grasslands for agriculture, principally the cultivation of durum wheat. This farming practice and the abandonment of some of the remodeled areas have increased the risk of soil erosion and desertification processes, and is manifest in land degradation by rill networks and gullying.     

Climate change and soil erosion on agricultural land in england and wales

To assess the effects of climate change on soil erosion we need to model changes in rate, frequency and extent of erosion. Present day rates of soil erosion for agricultural land in England and Wales are known from a national monitoring scheme and also from a local one. The latter, for the South Downs, covers a seven-year period and includes climatic data. This shows a strong correlation between total erosion and a Rainfall Index. The availability of these databases allows us to use existing models such as EPIC and an Expert System to predict erosion rates for postulated warmer and wetter (winter) conditions. EPIC is particularly suitable for specific sites where detailed data exists and crop yield implications can also be modelled. A rule-based Expert System approach allows us to examine erosion rates at a different scale across the landscape. We postulate that water erosion rates on arable land in the lowlands will increase markedly in severity, frequency and extent especially if land use changes. In the uplands predicted climatic warming suggests a longer growing season and fewer frosts: these may lead to a decrease in erosion of overgrazed eroding slopes. Increases in erosion rates are not inevitable if policy decisions are taken and implemented in good time.     

Influence of land use change on soil nutrients in an intensive agricultural region of North China

The pressures of development and major shifts in land use have increased the need to assess the impact of land use change on soil nutrients. This study was conducted in an area with intensive agricultural land use in north China to assess effects of land use change on soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP) and available potassium (AK). Soil samples were collected from rainfed land, irrigated land, virgin grassland and vegetable land in 1980 and 1999. SOC, TN and AP were higher in 1999 than in 1980, and the increases followed the following order: vegetable land > irrigated land > rainfed land, except for AK. Soil nutrient contents were increased when land uses underwent the following changes (except for AK): virgin grassland → rainfed land → irrigated farmland → vegetable land. The SOC, TN and AP fluxes (rate of change in C, N, P and K as kg(ha y)⁻¹) in the transition systems from rainfed land to vegetable land were 518.46, 69 and 3.9 kg(ha y)⁻¹, respectively, which were considerably higher than the transition systems from rainfed land to irrigated land. The SOC, TN and AP fluxes in the transition systems from virgin grassland to irrigated land were 297.83, 56.3, 2.1 kg(ha y)⁻¹, respectively, which were higher than the transition systems from virgin grassland to rainfed land. The study shows that land use intensification can increase soil nutrient contents if accompanied by increased fertilizer application.     

Gully erosion: Impacts, factors and control

Gully erosion attracts increasing attention from scientists as reflected by two recent international meetings [Poesen and Valentin (Eds.), Catena 50 (2–4), 87–564; Li et al., 2004. Gully Erosion Under Global Change. Sichuan Science Technology Press, Chengu, China, 354 pp.]. This growing interest is associated with the increasing concern over off-site impacts caused by soil erosion at larger spatial scales than the cultivated plots. The objective of this paper is to review recent studies on impacts, factors and control of gully erosion and update the review on ‘gully erosion and environmental change: importance and research needs’ [Poesen et al., 2003. Catena 50 (2–4), 91–134.]. For the farmers, the development of gullies leads to a loss of crop yields and available land as well as an increase of workload (i.e. labour necessary to cultivate the land). Gullies can also change the mosaic patterns between fallow and cultivated fields, enhancing hillslope erosion in a feedback loop. In addition, gullies tend to enhance drainage and accelerate aridification processes in the semi-arid zones. Fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion. In this respect, tracers such as carbon, nitrogen, the nuclear bomb-derived radionuclide 137 Cs, magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment. Recent studies conducted in Australia, China, Ethiopia and USA showed that the major part of the sediment in reservoirs might have come from gully erosion.Gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess (European belt, Chinese Loess Plateau, North America) and sandy soils (Sahelian zone, north-east Thailand) or in soils prone to piping and tunnelling such as dispersive soils. Most of the time, the gullying processes are triggered by inappropriate cultivation and irrigation systems, overgrazing, log haulage tracks, road building and urbanization. As exemplified by recent examples from all over the world, land use change is expected to have a greater impact on gully erosion than climate change. Yet, reconstructions of historical causes of gully erosion, using high-resolution stratigraphy, archaeological dating of pottery and ¹⁴C dating of wood and charcoal, show that the main gully erosion periods identified in Europe correspond to a combination not only of deforestation and overuse of the land but also to periods with high frequency of extreme rainfall events.Many techniques have proved to be effective for gully prevention and control, including vegetation cover, zero or reduced tillage, stone bunds, exclosures, terracing and check dams. However, these techniques are rarely adopted by farmers in the long run and at a larger spatial scale because their introduction is rarely associated with a rapid benefit for the farmers in terms of an increase in land or labour productivity and is often contingent upon incentives.     

Climate change impacts on soil erosion in Midwest United States with changes in crop management

This study investigates potential changes in erosion rates in the Midwestern United States under climate change, including the adaptation of crop management to climate change. Previous studies of erosion under climate change have not taken into account farmer choices of crop rotations or planting dates, which will adjust to compensate for climate change. In this study, changes in management were assigned based on previous studies of crop yield, optimal planting date, and most profitable rotations under climate change in the Midwestern United States. Those studies predicted future shifts from maize and wheat to soybeans based on price and yield advantages to soybeans. In the results of our simulations, for 10 of 11 regions of the study area runoff increased from + 10% to + 310%, and soil loss increased from + 33% to + 274%, in 2040–2059 relative to 1990–1999. Soil loss changes were more variable compared to studies that did not take into account changes in management. Increased precipitation and decreasing cover from temperature-stressed maize were important factors in the results. The soil erosion model appeared to underestimate the impact of change in crop type, particularly to soybeans, meaning that erosion increases could be even higher than simulated. This research shows that future crop management changes due to climate and economics can affect the magnitude of erosional impacts beyond that which would be predicted from direct climate change alone. Prediction of future soil erosion can help in the management of valuable cropland and suggest the need for continually changing soil conservation strategies.     

Impacts of land use/cover change on soil properties in the Mediterranean region of northwestern Jordan

This study was carried out to evaluate the effects of deforestation on physical and chemical properties of soils under native forest in the Mediterranean region of northwestern Jordan. Land use/cover maps of 1953, 1978 and 2002 were interpreted and analysed within GIS to quantify the shift from forest to rainfed cultivation. Six sites were sampled in a non‐changed forest and in cultivated fields, three for each. Different soil properties of texture, bulk density, organic matter, total nitrogen, pH, cation exchange capacity (CEC), phosphorous and potassium were analysed. Results showed that many forests were changed into cultivated lands at a rate more than the reforestation. Subsequently, adverse effects on the studied physical and chemical properties were observed. The most affected properties were particle size distribution, bulk density of surface soil and subsoil. Organic matter and CEC decreased in cultivated soil as compared to the forest soil. Cultivated soils were found to exhibit a significantly lower status in physical and chemical soil properties as compared to forest soils. This general decline in the soil physical and chemical properties, in turn, contributed to soil erosion, reduction of soil fertility and land degradation. There is an urgent need to improve soil quality by developing sustainable land use practices to reduce the rate of soil degradation and to ensure long‐term sustainability of the farming system in the study area and in similar biophysical settings. Copyright © 2008 John Wiley & Sons, Ltd.     

基于土地利用结构特征的土壤侵蚀强度预测研究——以四川省为例

研究计算四川省土地利用结构特征指数和土壤侵蚀强度指数结果表明,该省土地利用结构特征指数与土壤侵蚀强度指数的变化具有同步性,用土地利用结构特征指数预测其土壤侵蚀强度变化是合理可行的。     

Effects of land use on soil erosion in a tropical dry forest ecosystem,Chamela watershed,Mexico

During the past few decades, Mexico has been converting tropical dry forest (TDF) into cropland and pasture, with land degradation expressed as soil erosion being the main environmental consequence. The factors and processes influencing soil erosion are related to scale. At a microscale, the stability of soil aggregates has a significant impact on soil erodibility and strongly influences other soil properties. However, at plot and watershed scales, these relationships are less well known. The relationships between the distribution of soil aggregate size, soil properties and soil erosion were examined for two soil geomorphological units (hillslopes over granite and hillslopes over tuffs) and three land uses (TDF, unburned pasture and burned pasture) within the Chamela watershed of west–central Mexico. To evaluate soil aggregation as a parameter for upscaling soil erosion, the researchers measured microtopographic features at plot scales and interpreted 1:35,000 panchromatic aerial photographs at a watershed scale. Analysis of variance indicated significant differences in soil organic carbon (P < 0.05) and soil moisture (P < 0.01) contents between the two soil geomorphological units, and field tests showed differences in soil texture and structure.     

RS与GIS支持下的土地利用及植被覆盖变化研究

利用遥感（RS）和地理信息系统（GIS）技术，对泰国北部山区1985－1995年土地利用及植被覆盖变化进行了定量研究，并以Mae Uam子流域为例研究了各类用地的地形分布状况及其变化趋势。结果表明，10年间流域内森林面积减少，而耕地、裸地、草地和城镇建设用地 增加且这些变化主要发生在地势较为平坦的地形范围内，在高坡度地区土地利用变化较小。     

Impact of climate change on soil erosion, runoff, and wheat productivity in central Oklahoma

The potential for global climate changes to increase the risk of soil erosion is clear, but the actual damage is not. The objectives of this study were to evaluate the potential impacts of climate change on soil erosion, surface runoff, and wheat productivity in central Oklahoma. Monthly projections were used from the Hadley Centre's general circulation model, HadCM3, using scenarios A2a, B2a, and GGa1 for the periods of 1950–1999 and 2070–2099. Projected changes in monthly precipitation and temperature distributions between the two periods were incorporated into daily weather series by means of a stochastic weather generator (CLIGEN) with its input parameters adjusted to each scenario. The Water Erosion Prediction Project (WEPP) model was run for four climate scenarios including a recent historical climate and three tillage systems (conventional tillage, conservation tillage, and no-till). HadCM3-projected mean annual precipitation during 2070–2099 at El Reno, Oklahoma decreased by 13.6%, 7.2%, and 6.2% for A2a, B2a, and GGa1, respectively; and mean annual temperature increased by 5.7, 4.0, and 4.7 °C, respectively. Predicted average annual soil loss in the tillage systems other than no-till, compared with historical climate (1950–1999), increased by 18–30% for A2a, remained similar for B2a, and increased by 67–82% for GGa1. Predicted soil loss in no-till did not increase in the three scenarios. Predicted mean annual runoff in all three tillage systems increased by 16–25% for A2a, remained similar for B2a, and increased by 6–19% for GGa1. The greater increases in soil loss and runoff in GGa1 were attributed to greater variability in monthly precipitation as projected by HadCM3. The increased variability led to increased frequency of large storms. Small changes in wheat yield, which ranged from a 5% decrease in B2a to a 5% increase in GGa1, were because the adverse effects of the temperature increase on winter wheat growth were largely offset by CO₂ rise as well as the bulky decrease in precipitation occurred outside the growing season. The overall results indicate that no-till and conservation tillage systems will be effective in combating soil erosion under projected climates in central Oklahoma.     

Land use history and historical soil erosion at Albersdorf (northern Germany) — Ceased agricultural land use after the pre-historical period

The Holocene landscape history and historical soil erosion were reconstructed at Albersdorf (Schleswig-Holstein, Germany) from soils and colluvial layers. In contrast to many landscapes in central Europe, agricultural land use and soil erosion were more frequent during pre-historical times, whereas it has almost ceased after the advent of history. Pre-historical soil erosion rates from about 0.1 to 6.9 t ha^− 1 a^− 1 were reconstructed with no significant differences between the prehistoric cultural phases. The study of buried soils within the soil/soil-sediment-sequences provided evidence for an acceleration of soil formation processes probably as a consequence of excessive prehistoric woodland pasture on poor sandy soils.     

Effects of land use on soil erosion and nutrient loss in the Three Gorges Reservoir Area, China

Abstract. By comparing field measurements from 1989, 1997, and 1998, the differences between farmland (sloping farmland, sloping farmland with contour cultivation, terraced farmland) and orchard (terraced orchard, unterraced orchard), in the Three Gorges Reservoir Area, were significant for runoff ( P <0.01), erosion ( P <0.05) and nutrient loss ( P <0.05). Taking into account economic costs and environmental influences, reasonable and sustainable land use on slopes of 25° in the Three Gorges Reservoir Area should be unterraced orchard.     

Global analysis of cover management and support practice factors that control soil erosion and conservation

Cover management and support practices largely control the magnitude and variability of soil erosion. Although soil erosion models account for their importance (particularly by C- and P-factors in the Revised Universal Soil Loss Equation), obtaining spatially explicit quantitative field data on these factors remains challenging. Hence, also our insight into the effects of soil conservation measures at larger spatial scales remains limited. We analyzed the variation in C- and P-factors caused by human activities and climatic variables by reviewing 255 published articles reporting measured or calculated C- and P-factor values. We found a wide variation in both factor values across climatic zones, land use or cover types, and support practices. The average C-factor values decreased from arid (0.26) to humid (0.15) climates, whereas the average P-factor values increased (from 0.33 to 0.47, respectively). Thus, support practices reduce soil loss more effectively in drylands and drought-prone areas. The global average C-factor varies by one order of magnitude from cropland (0.34) to forest (0.03). Among the major crops, the average C-factor was highest for maize (0.42) followed by potato (0.40), among the major orchard crops, it was highest for olive (0.31), followed by vineyards (0.26). The P-factor ranged from 0.62 for contouring in cropland plots to 0.19 for trenches in uncultivated land. The C-factor results indicate that cultivated lands requiring intensive site preparation and weeding are most vulnerable to soil loss by sheet and rill erosion. The low P-factor for trenches, reduced tillage cultivation, and terraces suggests that significantly decreased soil loss is possible by implementing more efficient management practices. These results improve our understanding of the variation in C- and P-factors and support large-scale integrated catchment management interventions by applying soil erosion models where it is difficult to empirically determine the impact of particular land use or cover types and support practices: the datasets compiled in this study can support further modeling and land management attempts in different countries and geographic regions.     

Soil erosion prediction in the Grande River Basin, Brazil using distributed modeling

Mapping and assessment of erosion risk is an important tool for planning of natural resources management, allowing researchers to modify land-use properly and implement management strategies more sustainable in the long-term. The Grande River Basin (GRB), located in Minas Gerais State, is one of the Planning Units for Management of Water Resources (UPGRH) and is divided into seven smaller units of UPGRH. GD1 is one of them that is essential for the future development of Minas Gerais State due to its high water yield capacity and potential for electric energy production. The objective of this study is to apply the Universal Soil Loss Equation (USLE) with GIS PCRaster in order to estimate potential soil loss from the Grande River Basin upstream from the Itutinga/Camargos Hydroelectric Plant Reservoir (GD1), allowing identification of the susceptible areas to water erosion and estimate of the sediment delivery ratio for the adoption of land management so that further soil loss can be minimized. For the USLE model, the following factors were used: rainfall–runoff erosivity (R), erodibility (K), topographic (LS), cover-management (C) and support practice (P). The Fournier Index was applied to estimate R for the basin using six pluviometric stations. Maps of the K, C, LS and P factors were derived from the digital elevation model (DEM), and soil and land-use maps, taking into account information available in the literature. In order to validate the simulation process, Sediment Delivery Ratio (SDR) was estimated, which is based on transported sediment (TS) to basin outlet and mean soil loss in the basin (MSL). The SDR calculation included data (total solids in the water and respective discharge) between 1996 and 2003 which were measured at a gauging station located on the Grande River and a daily flow data set was obtained from the Brazilian National Water Agency (ANA). It was possible to validate the erosion process based on the USLE and SDR application for the basin conditions, since absolute errors of estimate were low. The major area of the basin (about 53%) had an average annual soil loss of less than 5 t ha^− 1 yr^− 1. With the results obtained we were able to conclude that 49% of the overall basin presently has soil loss greater than the tolerable rate, thus indicating that there are zones where the erosion process is critical, meaning that both management and land-use have not been used appropriately in these areas of the basin. The methodology applied showed acceptable precision and allowed identification of the most susceptible areas to water erosion, constituting an important predictive tool for soil and environmental management in this region, which is highly relevant for prediction of varying development scenarios for Minas Gerais State due to its hydroelectric energy potential. This approach can be applied to other areas for simple, reliable identification of critical areas of soil erosion in watersheds.     

有机管理对不同土地利用方式下土壤质量的影响

许多研究发现有机管理可以改善农田土壤质量,但是否不同土地利用方式下都存在此结论尚未明确。为探究有机管理对不同土地利用方式土壤质量的影响,本研究基于一个多土地利用方式的有机管理农场及其附近常规管理农田进行土壤质量调查,对比不同管理措施及大棚菜地、果园、露天菜地、农田边界、稻田田埂5种土地利用方式下农田土壤质量的差异,并对不同管理措施下农田土壤养分含量、重金属含量、动物数量共计20个指标进行方差分析和主成分分析。研究发现虽然总体上(综合5种土地利用方式的均值)有机管理的土壤pH显著高于常规农田;但针对一种土地利用方式,只有露天菜地和农田边界的土壤pH显著提高。总体上有机管理下土壤全磷、全钾、有效磷含量显著降低,但露天菜地土壤有机质和全氮含量均显著高于常规管理农田。有机管理在总体上显著降低了土壤Cr、Cu、Ni、Zn含量;但针对一种土地利用方式,只显著降低了大棚菜地土壤Cr、Ni、Zn含量,果园和稻田田埂土壤Cu含量,露天菜地和农田边界土壤Zn含量。有机管理虽然总体上均显著增加了土壤中蜘蛛目、倍足纲、步甲、蚯蚓的数量;但针对一种土地利用方式,只显著增加了露天菜地地表蜘蛛目、倍足纲、步甲,稻田田埂地表步甲、土壤蚯蚓以及果园倍足纲数量。主成分分析结果表明,不同管理方式下土壤质量差异明显,有机管理下蜘蛛目、倍足纲、步甲和蚯蚓等土壤动物较多,土壤pH较高,土壤P含量较低,重金属Cu、Pb、Zn、Cr含量较低,但并非在所有土地利用方式下都成立。由此可见,有机管理虽然总体上可以改善土壤质量,但受具体管理措施、人为投入品数量和有机种植时间等因素影响,并非在所有土地利用方式下效果都显著,且在不同土地利用方式下显著改善的指标也各不相同,因此需要针对不同土地利用方式和不同指标采取针对性的改善措施。     

Temporal and spatial changes of soil erosion under land use and land cover change based on Chinese soil loss equation in the typical watershed on the Loess Plateau

Land use and land cover change (LULCC) directly affect the temporal and spatial change of soil erosion. As a typical governance watershed in the hilly and gully area of the Loess Plateau, the Jiuyuangou watershed has experienced significant LULCC in the past 10 years due to conversion of farmland to forests, economic construction, and cropland abandonment. However, the evolution process of soil erosion change and LULCC in the watershed is unclear, as is the relationship between the two. This study used satellite images to extract information on LULCC in the watershed and the Chinese soil loss equation (CSLE) model to evaluate the temporal and spatial evolution of soil erosion in the watershed from 2010 to 2020. The main results showed that (1) the continuous vegetation restoration project in the watershed reduced soil erosion from 2010 to 2015; however, the increased frequency of extreme rainfall events after 2015 reduced its impact. The annual average soil erosion modulus decreased from 10.85 t ha⁻¹ year⁻¹ in 2010 to 8.03 t ha⁻¹ year⁻¹ in 2015 but then increased to 10.57 t ha⁻¹ year⁻¹ in 2020; (2) the main land use and land cover (LULC) type in the Jiuyuangou watershed is grassland, accounting for 62% of the total area, followed by forestland, cropland, buildings, and water. Cropland has the largest multi-year average soil erosion modulus, followed by grassland and buildings, with forestland having the smallest; (3) significant spatial correlations occurred between soil erosion change and LULCC for common ‘no change’ and common ‘gain’ in the settlements, roads, and areas near the human influences with good soil and water conservation, but not other regions due to the influence of climatic factors (heavy rain events). Thus, we should repair terraces, control dams in the watershed, and actively conserve water and soil. This study provides a scientific reference for planning and managing water and soil conservation and ecological environment construction in the watershed.     

History, origin and extent of soil erosion on Easter Island (Rapa Nui)

The isolated Easter Island (Rapa Nui) is an outstanding example of land degradation caused by land use in a sensitive ecosystem. The focus of the investigation was placed on Poike peninsula, the most eastern part of Rapa Nui. While Poike peninsula was once supplied with fertile soils, in large areas desertification takes place today. Detailed analysis of soil profiles allowed the reconstruction of the history and of causes and effects of soil erosion and gullying in the context of land use history and cultural evolution. The results of the stratigraphic analysis prove that from the beginning of human settlement around AD 300/600 until AD 1280 the agriculture on Poike peninsula was characterised by sustainable land use and a traditional type of agro-forestry. Soil erosion was not significant. At around AD 1280 the woodland on Poike, dominated by the endemic palm Jubaea sp., was cleared by slashing and burning. Intensive farming on the upper slopes of the volcanic peninsula resulted in sheet erosion lasting until the 20th century. Settlements and ceremonial places which were built around AD 1300 on downslope areas were buried soon by sediments. Agriculture ceased around AD 1400 on downslope areas as the fertile soils were completely eroded. From AD 1400 until the late 19th century sheet erosion and the accumulation of fine-layered sediments migrated upslope. On average 8.6 Mg of soil per hectare and per year were reworked by erosion (eroded and accumulated within the catchment). Gullying began on Rapa Nui with the sudden increase in the number of sheep during the early 20th century. Gullies are still developing on the island and their ongoing enlargement created extended badlands on Poike which pose a significant problem for ecological and archaeological conservation strategies. Gullying rates exceed 190 Mg ha^{− 1} y^{− 1}.     

土地利用变化对粮食产量与环境效应的影响——以黑龙江省双城市为例

以1986年和2000年1:10万陆地卫星解译数据为基础,结合统计数据,利用地理信息系统的空间分析功能,分析了14年来双城市土地利用变化情况及其对粮食产量和环境效应的影响。结果表明:双城市旱田面积、草地面积和水域面积在逐年减少,分别减少1841．15hm2、3030．25hm2和70．86hm2;城镇用地、居民用地、林地和水田面积呈增加趋势,分别增加581．78hm2、363．91hm2、1103．5hm2和2934．77hm2;双城市粮食产量趋于一种起伏的上升状态,由1982年37．3万t上升到2001年135．3万t,最高年份1998年粮食产量为165．1万t;从双城市1957～2000年的年均气温和降水分析得出,年均气温上升,年均降水量减少。     

Landscape and land use effects on soil resources in a Himalayan watershed

Sustainable land management decisions at all scales require solid, science-based information. Soil quality assessment can provide this regarding soil physical, chemical, and biological characteristics and the ability to provide ecosystem and societal services. Our objective was to make a regional assessment of soils in the Garhwal Himalayas to determine their ability to perform various functions and respond to external influences. Five functional categories were assessed using 13 soil parameters focused on ecological sustainability. Human land use effects on soils were referenced to natural woodlands at each landscape position. Within upper-slope regions, flora and fauna habitat, moisture retention, organic matter and nutrient cycling, air and water infiltration and resistance to erosion were decreased 35, 27, 24, 24, and 9%, respectively. At mid-slope positions the order and magnitude of decrease were organic matter and nutrient cycling, flora and fauna habitat, and moisture retention (26, 22, and 16%, respectively). Changes within the valley were lowest, averaging − 3% for flora and fauna habitat and − 13% for organic matter and nutrient cycling. We conclude that the minimum data set (MDS) used provided a representative assessment of soil quality and could serve as a basis for assessment in similar tropical watersheds.