紫色丘陵区小流域土壤侵蚀产沙空间分布的 137Cs法初步研究

该文通过紫色丘陵区响水滩小流域不同土地利用类型、不同坡度和坡长、不同地貌部位土壤剖面中 ¹³⁷Cs含量的测定与分析，对其侵蚀空间分布进行了估算。研究结果表明：该流域 ¹³⁷Cs含量的背景值为1870 Bq/m²；流域内坡耕地、林地的年平均侵蚀强度分别为4468、1759 t/(km²·a)；土壤侵蚀量与坡长、坡度均指数相关；丘顶、丘坡和鞍部的年平均侵蚀强度分别为2125、4676、3625 t/(km²·a)。结果表明土地利用类型、坡长和坡度、地貌部位对土壤侵蚀量影响很大，坡耕地是该流域泥沙的主要来源。     

Hydrosedimentology of nested subtropical watersheds with native and eucalyptus forests

Purpose

Information on the effects of eucalyptus forests on hydrosedimentological processes is scarce, particularly at the catchment scale. Monitoring and mathematical modeling are efficient scientific tools used to address the lack of information for natural resource management and the representation and prediction of those processes. This study evaluates the effects of eucalyptus cultivation on hydrosedimentological processes in watersheds and to use the Limburg soil erosion model (LISEM) to represent and predict hydrological processes.

Material and methods

The study was conducted in two forested watersheds: the main watershed (94.46 ha) and a nested sub-watershed (38.86 ha), both cultivated with eucalyptus and residual riparian native forest, located in southern Brazil. Hydrosedimentalogical monitoring was conducted from 16th February 2011 to 31st December 2012, and LISEM model calibrations were performed on the bases of six storms events.

Results and discussion

The sediment yield for 2011 was 41.6 Mg km^?2 and 38.5 Mg km^?2 for the watershed and sub-watershed, respectively. An extreme event in 2012 provided greater sediment yield for the sub-watershed (99.8 Mg km^?2) than that for the watershed (51.7 Mg km^?2). Rainfall events with a greater maximum intensity generated rapid discharge and suspended sediment concentration responses in the sub-watershed due to the smaller drainage area and steeper landscape. In the main watershed, the accumulation of flood waves occurred for most events, with less steep hydrographs, and a later occurrence of the discharge peak after that of the sub-watershed. The LISEM adequately reproduced the peak discharge and runoff for the calibrated events; however, the peak time and the shape of the hydrograph were not adequately represented.

Conclusions

The hydrosedimentological patterns of the watershed and sub-watershed, both cultivated with eucalyptus, was characterized by sedimentographs preceding hydrographs during rainfall–runoff events where scale effects occur, with maximum discharge and specific sediment yield greater in the watershed than that in the sub-watershed. Empirical models based on hydrologic variables may be used for estimating the suspended sediment concentration and sediment yield. Therefore, LISEM may be used for the prediction of hydrological variables in these forested watersheds.     

红壤区稀土矿开发导致河流泥沙淤积量的估算--以江西省信丰县崇墩沟小流域为例

不合理的人为活动是侵蚀产沙的主要原因之一。在江西省信丰县崇墩沟小流域内由于稀土矿产的无序开发,导致河流泥沙严重淤积。通过实测河流淤积泥沙断面,计算出在7 500 m长的河道共淤积泥沙30 193 t,考虑到输移比,整个流域内土壤流失量可达3 500 t/km2,平均侵蚀模数也高达1 150 t/(km2.a)以上,属于中等强度的土壤侵蚀。调查结果发现,河流中淤积的泥沙主要来源于稀土矿开发的尾矿流失;土壤流失量高到99 730 t/km2,年平均侵蚀模数为34 000 t/(km2.a)以上,属于极强度的水土流失。治理水土流失,须加强对稀土矿开发的管理,防止形成新的水土流失;将已废弃的稀土尾矿作为治理的重中之重,可有效地降低流域内土壤侵蚀的强度。     

基于ESTARFM NDVI的察汗淖尔流域灌溉耕地提取方法研究

运用遥感精准识别技术提取灌溉耕地可以为区域内农业耗水管理提供关键数据支持,但受限于遥感数据的时空分辨率,对于光谱特性相似容易混淆的灌溉耕地作物识别有一定难度。为此,本研究通过增强型自适应反射率时空融合模型(Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model,ESTARFM)对MODIS和Landsat数据进行融合,得到察汗淖尔流域时间分辨率为8 d、空间分辨率为30 m的NDVI数据,并与同期真实Landsat NDVI进行对比验证,相关系数为0.94。利用HANTS滤波建立ESTARFN NDVI时间序列数据,选取灌溉耕地样本通过支持向量机进行灌溉耕地空间分布的提取,以弥补数据源、特征提取等限制因素对复杂灌溉耕地提取的空缺。结果表明:流域内灌溉耕地总面积为1958.24km~2,商都、兴和、尚义、康保和化德5县耕地总面积占流域耕地总面积的94%,灌溉耕地分别为616.67km~2、337.36km~2、409.85km~2、290.93 km~2和239.38 km~2,主要种植葵花、甜菜、马铃薯等生长季从4月初到9月底的长生育期作物和生长季从5月初到8月初的蔬菜;张北、察哈尔右翼前旗、后旗和镶黄旗耕地占流域耕地总面积为6%, 4县灌溉耕地面积共64.05 km~2。最后,通过真实样本进行验证,总分类精度为93.18%, Kappa系数为0.91。结果表明,用该数据融合模型获得的NDVI时间序列能反映作物真实变化情况,并且使用支持向量机提取察汗淖尔流域灌溉耕地效果较好。     

Sediment Yield Deduction from Check–dams Deposition in the Weathered Sandstone Watershed on the North Loess Plateau,China

As the basic unit of erosion and sediment yield, it was critical to determine the amount of soil erosion and sediment yield in the small watersheds for sustaining a reasonable water resource and sediment regulation system. In this study, we determined the sediment yield from the dams‐controlled watershed on the North Loess Plateau. Three check dams in the watershed were investigated by drilling ten‐hole sedimentation cores. The corresponding flood couplets were dated according to thickness of deposition layers, distribution of sediment particle size and historical erosive rainfall events. On the basis of the check dams capacity curve, the soil bulk density and the thickness of couplets, the deposit mass of check dams, and then the sediment yield of watershed at different temporal and spatial scale were deducted. In total of the 33, 60 and 55 couplets were corresponded to individual flood events in the dam MH1# from 1976 to 1984, the dam MH2# from 1985 to 2007, and the dam MH4# from 1981 to 2009, respectively. The specific sediment yield for flood events was 1,188.5–11,527.9 Mg km⁻², 1,278.6–17,136.7 Mg km⁻², and 3,395.9–33,698.5 Mg km⁻², and the annual average sediment yield was 10,728.6 Mg (km² · a)⁻¹, 12,662.9 Mg (km² · a)⁻¹, and 16,753.3 Mg (km² · a)⁻¹ in dam MH1#, MH2# and MH4# controlled watershed, respectively. The sediment yields were inversely proportional to the dams – controlled areas. For the whole watershed, the annual average sediment yield was 14,011.1 Mg (km² · a)⁻¹ from 1976 to 2009. There were large amounts of sediments (42.3–50.5%) were intercepted gradually along the way from small watersheds to the river channel. And the minimum rainfall for sediment deposited in the dams was greater than 20 mm in this watershed. The results of this study suggested that the sediments retained behind check dams were helpful to quantifying the amount of erosion sediment yield and understanding the soil erosion evolution in the small and ungauged watersheds. Copyright © 2016 John Wiley & Sons, Ltd.     

废黄河沙土区土壤侵蚀量分析

废黄河沙土区是水土流失比较严重地区,通过对废黄河上、中、下游3个典型地带径流小区2006年观测资料的统计分析,获得废黄河沙土区不同下垫面坡面条件下的土壤侵蚀状况.结果分析表明,一般农地土壤年侵蚀量在1191～2714 t/k㎡之间;林地在550～1157 t/k㎡;沟坡在7779～8658 t/k㎡(坡度17°～22°).其中,农地受人工扰动后的土壤年侵蚀量约为未扰动农地侵蚀量的2～4倍.     

137Cs、HCHs测定岩溶洼地沉积物年代及流域产沙强度

以青木关岩溶槽谷区内代表性耕地型与林地型洼地小流域为研究对象,从洼地沉积物入手,探明各洼地沉积物剖面~(137)Cs比活度、六六六(HCHs)、有机质、黏粒含量及容重的深度分布特征;运用~(137)Cs示踪法,辅以HCHs进行沉积物断代,追溯流域近60年来的土壤侵蚀量演变特征及探讨其驱动因素。结果表明:(1)炮台院子耕地型洼地沉积物剖面~(137)Cs、HCHs仅有个别层位检出,无法利用~(137)Cs、HCHs深度分布进行沉积物断代,反映了发育的落水洞对其沉积物剖面影响大。(2)龙洞槽耕地型和劳动村林地型洼地小流域1963—1983,1984—2019年产沙模数分别为231.78,82.04 t/(km~2·a)和68.79,39.46 t/(km~2·a),表明流域生态环境得到明显改善。与1963—1983年时段相比,该地区1984—2019年时段年平均降水量无明显变化,2个小流域产沙模数均显著减小,表明近60年流域产沙强度主要受土地利用方式、水土保持措施等人类活动控制。(3)龙洞槽洼地剖面~(137)Cs、HCHs峰值,表层泥沙~(137)Cs、HCHs数值和不同时期流域产沙模数均明显大于劳动村洼地,主要是由2个洼地分别控制的耕地型与林地型小流域在人类活动影响下产沙强度的差异所致。另外,~(137)Cs和HCHs相结合的示踪方法可较好地用于评估西南岩溶流域产沙量的时间变化。     

南小河沟流域不同措施处理下的水土流失规律

以南小河沟流域长期定位试验场为研究对象,研究了10种不同措施处理下水土流失规律。结果表明,泥沙流失量与径流量变化规律并不一致。一般坡度越大,侵蚀量的增量越大。由于坡度越大,需要坡长越长才能和坡度较小的的坡面受水面积相等,这时即使因为坡度加大,入渗率减少,但实际入渗水量也有较大增加,即坡面水流的径流量并不会随着坡度的加大而无限的加大,20°为径流量临界坡度;采用水平阶整地的油松沙棘混交林地,植被覆盖度达到65%,水土流失治理效果显著,平均含沙量2.377kg/m3,比裸地减少了57.77%以上;平均径流量0.121m3,比裸地减少了19.74%以上;以生物措施为主进行水土保持治理的杨家沟小流域与原始生态环境下的董庄沟小流域相比较,2012年侵蚀模数减少了2 589.95t/(km2·a)。     

Assessment of soil erosion at large watershed scale using RUSLE and GIS: a case study in the Loess Plateau of China

Soil erosion is a serious problem in the Loess Plateau of China, and assessment of soil erosion at large watershed scale is urgently need. This study used RUSLE and GIS to assess soil loss in the Yanhe watershed. All factors used in the RUSLE were calculated for the watershed using local data. RUSLE‐factor maps were made. The mean values of the R‐factor, K‐factor, LS‐factor, C‐factor and P‐factor were 970 209 MJ km⁻² h⁻¹ a⁻¹, 0·0195 Mg h MJ⁻¹ mm⁻¹, 10·27, 0·33359 and 0·2135 respectively. The mean value of the annual average soil loss was found to be 14 458 Mg km⁻² per year, and the soil loss rate in most areas was between 5000 and 20 000 Mg km⁻² per year. There is more erosion in the centre and southeast than in the northwest of Yanhe watershed. Because of the limitations of the RUSLE and spatial heterogeneity, more work should be done on the RUSLE‐factor accuracy, scale effects, etc. Furthermore, it is necessary to apply some physical models in the future, to identify the transport and deposition processes of sediment at a large scale. Copyright © 2005 John Wiley & Sons, Ltd.     

基于RUSLE模型的湟水流域土壤侵蚀时空变化

研究黄河上游土壤侵蚀的时空变化对于维持黄河上游生态系统服务功能、保护黄河上游水塔具有重要意义。以黄河上游典型区域湟水流域为研究区,采用RUSLE模型定量评估了该流域2000—2015年土壤侵蚀的时空变化特征,并分析了有无梯田措施下土壤侵蚀的空间变化,从而量化了梯田建设对防治坡面土壤侵蚀的影响。结果表明:2000—2015年,湟水流域的土壤侵蚀强度整体呈现减小趋势,侵蚀模数由1 183 t/(km~2·a)降低至940 t/(km~2·a),减少幅度为20.54%。不同土地利用类型以及不同坡度下的土壤侵蚀强度均有所降低,其中耕地上的减幅最大为20.58%。15°～20°坡度区间的侵蚀模数减幅最显著,为23.11%。通过有无梯田措施情景模拟发现,湟水流域2015年土壤侵蚀模数由940 t/(km~2·a)降低至有梯田的837 t/(km~2·a),减少11.00%。研究结果可为流域的水土流失防治和生态环境保护提供科学依据。     

Element Budgets in a Forested Watershed in Southern China: Estimation of a Proton Budget

We evaluated the element budgets in a forested watershed in Jiulianshan, southern China. The element input in bulk precipitation was characterized by high depositions of H⁺, NH₄ ⁺, Ca²⁺, and SO₄ ^2?, i.e., 400, 351, 299, and 876 eq/ha/yr, respectively. The outputs of H⁺, NH₄ ⁺, and SO₄ ^2? from the watershed were very low, while those of Ca²⁺ and Mg²⁺ were high, 712 and 960 eq/ha/yr, respectively. The element budgets suggested that i) the net retentions of H⁺, NH₄ ⁺, and SO₄ ^2? in this watershed were high, and ii) the net release of Mg²⁺ from this watershed was high mainly due to weathering. The net release of Ca²⁺ was not so high because of the high atmospheric deposition, while atmospheric deposition of Mg²⁺ was not so high (130 eq/ha/yr). Decrease of acid neutralizing capacity in the soil, i.e., net soil acidification, was caused mainly by the net release of Mg²⁺. Moreover, the net retention of SO₄ ^2? also contributed to soil acidification.     

Changes in soil organic carbon stocks and soil quality: land-use system effects in northern Ethiopia

Abstract

In Tigray, Ethiopia, land degradation is a dominant environmental problem and hence the regional government has undertaken restoration measures on degraded soils since 1991. The present study was aimed to assess the impact of land uses and soil management practices on soil properties, and consequently on soil quality of degraded soils. The catchments selected were Maileba and Gum Selassa, and land uses included cultivated (CL), grazing (GL), plantation (PA) and area exclosure (AE). Replicated soil samples were collected from topsoil and profiles of four land-use types in both catchments. Soils in area exclosure showed higher soil organic carbon (SOC), total N and extractable K than grazing land, cultivated land and plantation area mainly at 0–40 cm soil depth. Estimated soil organic carbon stock at Maileba in 0–40 cm depth varied between 54 to 74 Mg C ha^?1, being lowest in cultivated land and highest in area exclosure, and the soil organic carbon stock in area exclosure represents 63% of total carbon stock stored in the profile. Soil organic carbon stock (0–40 cm) at Gum Selassa ranged between 33 to 38 Mg C ha^?1, being higher in cultivated land and lower in plantation area. Soil quality index (SQI) of area exclosure (0.794) at Maileba and cultivated land (0.721) at Gum Selassa scored highest among all land uses, and the order was area exclosure>grazing land>plantation area>cultivated land at Maileba and cultivated land>grazing land>plantation area at Gum Selassa, highlighting the effectiveness of area exclosure in restoring soil quality of degraded soils.     

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.     

Soil conservation planning at the small watershed level using RUSLE with GIS: a case study in the Three Gorge Area of China

The Three Gorge Project (TGP) of China necessitates the resettlement of over 1 million population (mostly farmers) to more rugged and isolated areas than their original settlements. Soil erosion is a serious environmental and production problem in this area. To decrease the risk on environmental impacts, there is an increasing demand for sound, and readily applicable techniques for soil conservation planning in the Three Gorge Areas (TGA). The objectives of the study were to develop and validate a soil erosion-predicting model based on the revised Universal Soil Loss Equation (RUSLE) in a geographic information systems (GIS) environment. The use of GIS to develop conservation-oriented watershed management strategies in the Wangjiaqiao watershed is presented. Data used for the RUSLE were either determined or taken from published literature pertaining to the Wangjiaqiao watershed. In combination with IDRISI, GIS software (Eastman, R.J., 1997. IDRISI for Windows: User's guide (Version 2.0). Clark University, Graduate School of Geography, Worcester, MA, Chapters 4–17) was used to evaluate different agricultural management strategies in terms of predicted soil loss in the watershed. This model allowed for easy assessment of soil erosion hazards under different crop and land management options over the entire watershed. The study revealed that the annual average soil loss rate from relatively flat agricultural land was approximately 26 t/ha, whereas 52 t/ha was found on the cultivated sloping lands, which constitutes a large proportion of soil loss in the watershed. In the watershed, approximately 38 ha of agricultural land had slopes >47% (25°) and should be reforested or returned to pasture. Contour tillage (CT) and contour farming with a seasonal no-till ridge (CTN) were most effective in reducing soil loss rates. If CT and CTN were implemented, approximately 31% and 70%, respectively, of the areas with soil loss >T_EP would be reduced to <T_EP. T_EP is soil loss tolerance for economic planning and was set at ≤10 t/ha year. In addition to soil loss reduction, the CTN has the potential to increase crop yield. Soil erosion hazards may be alleviated in over 91% of the agricultural lands if combined conservation measures including terraces, CTN, CT, and crop rotations were implemented in the watershed. The results of the study indicate that the RUSLE-GIS model is a useful tool for resource management and soil conservation planning. This technology is readily transferable and accessible to other land managers and agronomists in the TGA.     

南方花岗岩红壤区不同土地利用类型坡地产流与侵蚀产沙研究

基于自然坡面径流小区,分析了南方花岗岩红壤区5种典型土地利用下坡面地表径流与侵蚀产沙规律.结果表明,不同地类地表径流与侵蚀产沙分异规律明显.裸露荒地、坡耕地、早地和疏林地的地表径流分别是典型林分林地的1 354.9%,1 099.9%,712.3%和285.4%;不同地类土壤侵蚀强度排序为裸露荒地＞坡耕地＞旱地＞疏林地＞典型林分林地,说明植被能较好地调蓄地表径流和减少侵蚀产沙.在不同降雨强度和雨型条件下,不同土地利用的坡面产流与侵蚀产沙也表现出显著的差异.裸露荒地、坡耕地、旱地、疏林地是研究区主要的侵蚀产沙地类.基于径流小区次降雨条件下径流和侵蚀产沙观测资料,建立了不同地类坡面径流与侵蚀产沙的回归方程.     

Coastal wetland vegetation features and digital Change Detection Mapping based on remotely sensed imagery: El-Burullus Lake,Egypt

El-Burullus Lake is one of the four Egyptian Ramsar sites that constitute internationally important wetlands as they contain a rich biodiversity and have a large number of water bird species. But the valuable resources in El-Burullus Lake and its surrounding area have faced various threats to wetlands over recent decades. This study was carried out to evaluate the dynamics of land cover change using three change scenes of recent and past satellite data from 1990 to 2019. The study utilized ArcGIS10.7, ERDAS Imagine 14, Landsat TM (1990, 1999, and 2010), Landsat OLI-TIRS (2019) to analyze the land-use/land-cover (LULC) of El-Burullus wetland. Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were employed to assess the change scenario of the area. Results indicated that vegetated land has increased significantly with a concomitant shrinkage in the water body and open soil during the study period. Approximately 53 km² (7.0%) of water body and 8.7 km² (1.3%) of open soil were lost, while vegetation areas expanded to approximately 29.9 km² (7.4%). Factors that underpin the observed changes in the area are; reclamation projects and fish-farms which are creating the danger of drying up of the southern coastal parts of the lake, as well as spreading of reed beds (mainly: Phragmites australis) that covers about 20% of El-Burullus lake which led to dry up the lake parts. Therefore, the study suggests the need for urgent attention on conservation of remaining wetland resources for sustainable utilization for the next generation.     

基于AnnAGNPS模型的黄土高原小流域土壤侵蚀定量评价

以位于黄土丘陵沟壑区的砖窑沟流域为试点，利用AnnAGNPS模型进行土壤侵蚀定量评价。采用流域8次径流事件监测数据进行模型检验，径流量和沉积物量的相对误差分别为10%和-10%，AnnAGNPS模型能够比较理想地模拟流域长期的径流量和沉积物量，并可应用于黄土丘陵沟壑区的径流流失和土壤侵蚀定量评价。采用2004年土地利用状况模拟分析了流域土壤侵蚀量及其空间分布，结果表明：该流域平均片蚀和细沟侵蚀强度为3508 t/(km²·a)，属中度侵蚀等级，黄土沟壑地的平均侵蚀强度最大，属极强度侵蚀等级；严重的沟道侵蚀显著增加了运移到流域出口的泥沙。     

Effect of land management on runoff and soil losses from two small watersheds in St Lucia

The influence of land use on runoff and soil loss was assessed on two small watersheds in the Eastern Caribbean island of St Lucia, under contrasting land management regimes. The data generated from these watersheds revealed that the soil losses from an intensively cultivated agricultural watershed were 20‐times higher in magnitude than that of a forested watershed both for peak rainfall event and for total duration of analysis. This was due to higher surface runoff rates and exposure of soil to direct raindrop impact within cultivated areas. Whereas the forest canopy cover in combination with higher infiltration capacities of the forested land reduced the erosive runoff from the forest watershed and thus the soil loss. Moreover, the energy intensities of large storms in excess of 40 mm were estimated and found to range between 400 MJ mm ha⁻¹ h⁻¹ and 1834 MJ mm ha⁻¹ h⁻¹. 1

1 Megajoules‐millimeters per hectare‐hour.

Soil loss from the agricultural watershed was strongly correlated (R² = 0·85) to storm energy‐intensity (EI₃₀). However, the correlation of soil loss with the EI₃₀ (R² = 0·71) was poor for the forest watershed due to the effect of canopy vegetation, which significantly reduced the energy of raindrop impact. Over the study period, cumulative soil losses were 10·0 t ha⁻¹ for the agricultural site and 0·5 t ha⁻¹ for the forest site. 2

2 Metric tons per hectare.

The largest storm observed during the study period resulted in erosion losses of 3·78 t ha⁻¹ and 0·2 t ha⁻¹ from the agricultural and forest sites respectively. The regression models were developed using the measured data for prediction of runoff and soil loss over the watersheds of St Lucia under similar conditions. This study contributed towards efficient watershed management planning and implementation of suitable water conservation measures in St Lucia. Copyright © 2005 John Wiley & Sons, Ltd.     

基于CSLE模型的天山北坡西白杨沟流域土壤侵蚀定量评价

[目的]定量评价天山北坡西白杨沟流域水土流失土壤侵蚀状况,分析其分布特征,为区域水土保持以及生态环境建设提供科学依据。[方法]以新疆维吾尔自治区乌鲁木齐县西白杨沟流域为研究区,采用样地调查与地理信息系统(GIS)、遥感(RS)技术相结合方法和CSLE模型,对西白杨沟流域进行土壤水力侵蚀评价及侵蚀强度空间分布分析。[结果]天山北坡西白杨沟流域平均土壤侵蚀模数748.91 t/(km~2·a)。地形对土壤侵蚀强度影响明显,在坡度20°～40°区域,土壤侵蚀模数最高,为1 127.22～1 229.62 t/(km~2·a)。缓坡(20°)区域,坡度对土壤侵蚀模数呈正效应,而在陡坡(40°～70°)区域,坡度对土壤侵蚀模数呈负效应。土壤侵蚀主要发生在南坡、东南坡和东坡;不同土地利用方式对土壤水力侵蚀程度影响不同,表现为:呈灌木林地[1 709.80 t/(km~2·a)]有林地[1 389.40 t/(km~2·a)]天然牧草地[605.20 t/(km~2·a)]人工牧草地[334.71 t/(km~2·a)]水浇地[113.69 t/(km~2·a)]的趋势。[结论]土壤侵蚀强度总体以微度和轻度为主,强烈侵蚀、极强烈侵蚀、剧烈侵蚀主要分布在流域的中下游和下游;天山北坡西白杨沟流域侵蚀强度的空间分布与地形、土地利用、土壤性质联系紧密。     

川中丘陵区小流域土壤侵蚀空间分异评价研究

将地理信息系统(GIS)技术Arc/Info与通用土壤流失方程(USLE)相结合进行了小流域土壤侵蚀量的估算。以盐亭农田生态系统国家野外科学观测研究站内的截流村小流域(简称截流村小流域)为研究对象,依据实地调查资料及地形、土地利用、土壤和植被等数据,建立了小流域空间数据库,利用GIS的栅格数据空间分析功能,将小流域空间离散化为10 m×10 m的栅格,在栅格内根据合适的USLE因子算法进行了土壤侵蚀量估算,进而对小流域内土壤侵蚀强度空间分异和小流域内侵蚀量进行了统计分析。结果表明,截流村小流域年均输沙模数为1244.7 t/(km2.a),侵蚀强度属轻度;坡耕地占流域面积的44.17%,年均土壤侵蚀模数为2195.0 t/(km2.a),其侵蚀总量占流域总侵蚀量77.93%,表明坡耕地是该小流域水土流失的策源地,小流域水土流失治理的关键是实现流域内坡耕地的合理利用。同时对于林地和小于10°坡耕地的侵蚀模数结果与相关研究仅相差19.8%和4.4%,证实了该模型的准确性和可靠性。