Spatial variability of water retention parameters and saturated hydraulic conductivity in a calcareous Inceptisols (Khuzestan province of Iran) under sugarcane cropping

The objective of this study was to quantify inherent spatial variability and spatial cross-correlation of the van Genuchten retention parameters and saturated hydraulic conductivity (K_s) of surface and subsurface layers in a calcareous Inceptisols (Khuzestan province, Iran) under sugarcane cropping. Measurements were performed on 100-cm³ undisturbed soil cores collected at 94 locations along a 30-m-long transect with horizontal sampling distance intervals of 0.3 and 1 m at soil depths of 0–40 and 40–80 cm, respectively. Spatial variability was investigated using conventional statistics and geostatistical techniques. Coefficient of variation (CV) varied from 8.2% (for shape parameter, n at 40–80 cm depth) to 256.7% (for K_s at 0–40 cm depth). The n parameter and saturated water content, θ_s, showed a small-scale spatial heterogeneity with a maximum CV of 11.3% for the first depth and 9.2% for the second depth. Most of the hydraulic parameters at both depths showed a spatial structure and convex experimental semivariograms with dominant spherical models with the influence range of 3.2–41 m. In most cases, the extent of spatial correlation scales of cross-semivariograms for pairs of cross-correlated hydraulic variables was found to be different with reference to those relating to the direct semivariograms of correlated variables.     

Comparing System of Wheat Intensification (SWI) with standard recommended practices in the northwestern plain zone of India

The practices of the System of Rice Intensification (SRI) methodology have been extended to wheat and various other crops with reported good results. To assess such reports with respect to wheat, an experiment was conducted at the Indian Agricultural Research Institute, New Delhi during 2011–2012 and 2012–2013. This experiment compared the performance of wheat under System of Wheat Intensification (SWI) and standard recommended practices (SRPs). In 2011–2012, the SWI yield of 7.93 t ha^?1 was 30% higher than for SRP in 2012–2013, climatically a less favorable year, hence SWI performed relatively better with a 46% yield advantage under climate stress. SWI produced 12.5% less in the stressful year, while the reduction for the SRPs ranged from 18% to 31%. Differences in yield attributes and root traits were also observed in favor of SWI. Available N, P, and K in the soil after harvesting was increased with SWI, whereas depletion in nutrients with the SRPs indicated the scope for SWI sustaining soil fertility. Higher yield compensated for higher SWI costs of cultivation. A net return of US$ 1383 ha^?1 was obtained with SWI, 35% more than the US$ 1020 ha^?1 from SRPs. Overall, SWI outperformed the SRPs in terms of yields, climate resilience, and economics.     

The nature of soil erosion and possible conservation strategies in Ntabelanga area,Eastern Cape Province,South Africa

Soil erosion is a major land degradation problem in South Africa (SA) that has economic, social and environmental implications due to both on-site and off-site effects. High rates of soil erosion by water are causing rapid sedimentation of water bodies, ultimately leading to water crisis in SA. Lots of financial and human resources are channelled towards controlling of soil erosion but unfortunately with little success. The level of soil erosion in a particular area is governed by the site properties. Therefore, it is inappropriate to generalize data on soil erosion at a large-scale spatial context. The literature on soil erosion in SA classifies Eastern Cape Province as a high-erosion-potential area using data collected at a large-scale spatial context. Collecting soil erosion data at a large spatial scale ignores site-specific properties that could influence soil erosion and has resulted in failure of many traditional soil erosion control measures applied in the province. Moreover, scientific principles underlying the processes and mechanisms of soil erosion in highly erodible soils are missing in SA. This review was to find effective soil erosion control measures by having an insight on what happens during soil erosion and how soil erosion occurs in Ntabelanga. The literature suggested that erosion in Ntabelanga could be influenced by both the erosivity and erodibility factors though the erodibility factors being more influential. Soil permeability contrast between the horizons could be influencing the rate and nature of soil erosion. To mitigate the impact of soil erosion in Ntabelanga, efforts should aim to improve the vertical flow capacity in the B horizon. Clay spreading, clay delving, addition of gypsum, deep ploughing and mulching could aid the water permeability problems of the subsurface horizons. However for effective soil management and control option, detailed studies of specific site properties are needed. The generated information can assist in formulating soil erosion policies and erosion control strategies in the Ntabelanga area and SA at large.     

基于GIS与RUSLE模型的喀斯特地区土壤侵蚀研究——以贵州省为例

[目的]对贵州省土壤侵蚀进行快速定量研究,为土壤侵蚀治理工作和土地利用决策提供科学依据。[方法]在GIS技术的支持下,利用日降雨量、土壤类型、土地利用、DEM,MODIS-NDVI等数据,结合RUSLE模型估算研究区土壤侵蚀量。[结果]研究区的2010年年均土壤侵蚀模数为880.81t/(km~2·a),属轻度侵蚀。大部分区域主要以小于500t/(km~2·a)的微度侵蚀为主,占研究区总面积的59.60%。土壤侵蚀面积(轻度侵蚀以上)达71 164.14km~2,占总面积的40.40%。强度以上土壤侵蚀面积达10 431.60km~2,占总面积的5.91%,主要分布在研究区西北部和东北部,以及北部大楼山、武陵山、东南部苗岭以及西部乌蒙山等地势较高以及中东部乌江,西南部北盘江等河流流域。[结论]林地、耕地和草地以及海拔在600~1 600m之间的区域是今后水土流失防治的重点区域。     

基于GIS和RUSLE的高山峡谷区土壤侵蚀研究——以云南省泸水县为例

[目的]研究区域土壤侵蚀,揭示水土流失的空间分异规律,为区域水土保持和生态农业建设提供理论指导依据。[方法]应用GIS和RUSLE模型对云南省泸水县的土壤侵蚀进行研究。RUSLE模型中的因子包括降雨侵蚀力、土壤可蚀性、坡度坡长因子、植被覆盖和水土保持措施因子,运用GIS空间分析模块,获取泸水县土壤侵蚀模数空间分布图,根据SL 190-2007的分级标准进行土壤侵蚀强度分级,并分析该区土壤侵蚀强度空间分布格局。[结果](1)从各强度侵蚀面积上看,泸水县2014年土壤侵蚀以微度侵蚀为主,占总面积的86.86%,但从平均土壤侵蚀模数看,土壤侵蚀量为4.24×10~6 t,平均侵蚀模数为1 373.1t/(km~2·a),土壤侵蚀强度属于轻度侵蚀;(2)土壤侵蚀较严重区与未利用地、耕地空间分布基本一致,在坡度25°~50°的范围内,侵蚀面积占总侵蚀面积的75%,并且在该坡度段上的耕地面积占总耕地的63%,剧烈侵蚀集中分布在未利用地上,中度以上剧烈以下强度侵蚀集中分布在该坡度段上的耕地上,说明该坡耕地、未利用地对土壤侵蚀的贡献最大,要加强对未利用地的生态治理。[结论]坡度大,陡坡垦殖和未利用地的不合理利用是该区土壤侵蚀加重的主要原因,坡度在25°以上的地区不适宜耕种,应优化农业产业结构如实施退耕还林还草等措施,才能有效的保持水土。     

珠江三角洲网河区顶点河道断面侵蚀形态的演变

[目的]研究断面形态的演变特征,给上游来水来沙、人类活动影响的分析提供检验,也为下游水文地貌的演变提供科学依据。[方法]利用珠江三角州网河区三水站和马口站资料,通过提取反映河道断面侵蚀形态的指标,采用模拟退火算法优化的投影寻踪模型,综合解析河道断面侵蚀形态的演变特征。[结果]由于三水站2009年的虚实比远大于其他年份的虚实比,2009年三水站断面侵蚀形态异于其他年份外,其他年份侵蚀形态的变化较为缓和;对于马口站而言,尽管该断面的侵蚀形态变化较多,但综合5项反映河道断面侵蚀形态指标来看,该断面形态的变化类型总体上可以划分成2种侵蚀类别。[结论]总体上,21世纪初马口和三水站断面比20世纪90年代过水断面增大,断面的过水能力有加大的趋势。     

南方崩岗侵蚀风险评估构想

[目的]探讨南方崩岗侵蚀风险评估构架,为崩岗防治规划及分期治理提供科学依据。[方法]通过引入风险评估的理念和方法,结合崩岗发育研究进展,参照生态环境、地质灾害等风险评估流程。[结果]界定了崩岗侵蚀风险内涵,拟定了崩岗侵蚀风险评估方法,构建了崩岗侵蚀风险评估指标体系,并提出了崩岗侵蚀风险评估程序。[结论]风险评估为崩岗侵蚀乃至土壤侵蚀研究领域提供了一种新的理念和方法。     

基于GIS的慈溪市土壤侵蚀敏感性评价

[目的]对影响浙江省慈溪市土壤侵蚀敏感性的各因素进行评价,为该市进行环境功能区划和各项水土保持措施工程的布局调整提供参考。[方法]借鉴土壤侵蚀流失USLE模型,选取降雨侵蚀力、土壤质地、植被覆盖和地形起伏度4因子构建土壤侵蚀敏感性评价体系,并运用GIS进行土壤侵蚀敏感性分析。[结果]慈溪市土壤侵蚀敏感性在空间格局上呈半圆环状结构分布,并且轻度敏感区面积为733.05km2,占比高达75.70%,广泛分布于平原乡镇地区;不敏感区主要分布于近海滩涂区域,极敏感、高度敏感及中度敏感区则位于南部的丘陵、山地地区。[结论]慈溪市土壤侵蚀敏感性评价结果与水土流失现状空间分布走势大致相符,为此应重视和预防水土保持工作。     

砒砂岩与沙复配土壤的冻融特征

[目的]揭示砒砂岩与沙复配土壤冻融特征及其对风蚀的影响,为毛乌素沙地土地整治可持续性提供理论依据。[方法]利用陕西省榆林市榆阳区气象资料和土壤观测数据,结合含水量变化规律,以砒砂岩与沙复配土壤为研究对象,沙土为对照,探究2种土壤冻结层形成差异、冻融过程及积雪消融特点。[结果]由于含水量的差异,复配土壤与沙冻结层形成特点具有差异,沙地表层通常会形成土壤干层,从表层之下冻结,而复配土壤的冻结层在地表形成;复配土壤的最大冻结深度为116.0cm;大于沙地的最大冻结深度96.0cm,且冻结层融解时间晚于沙地一周;积雪覆盖条件下,沙地表层存在1.0~6.4cm的土壤干层,而复配土壤表层不存在干层,复配土壤积雪盖度和厚度均大于原始沙地,阳坡尤为显著。[结论]土壤冻层和积雪在复配土壤地表形成了2层保护层,减少了休闲期的风蚀作用。     

基于RUSLE的线状开发建设项目区土壤侵蚀动态监测——以浙江省宁波市北环快速路工程为例

[目的]全面调查浙江省宁波市北环快速路施工前后及施工过程中土壤侵蚀时空变化状况,为今后线状生产建设项目水土保持遥感监测提供参考。[方法]分别利用2010年宁波市土地利用/覆盖类型图、道路图及调查数据,结合项目区地形图和实测高程点生成的数字高程模型(DEM)、实测土壤属性数据、水文站降雨数据等资料分别获取RUSLE模型中各因子值的空间分布,然后通过RUSLE模型计算项目区3个不同阶段的土壤侵蚀量,最后进行分类统计。[结果]项目施工前期和自然恢复期的土壤侵蚀均以微度侵蚀为主,所占项目面积比例分别为98.53%和99.73%;而施工期的土壤侵蚀等级以轻度和微度侵蚀为主,两者分别占项目区面积的52.5%和35.4%;项目施工期的平均土壤侵蚀模数为1 380.9t/(km2·a),远高于施工前及施工期后的251.3,155.4t/(km2·a)。[结论]项目施工期土壤侵蚀区域主要分布在临时堆土区,进一步分析发现坡度因素对土壤侵蚀空间分布具有重要影响。