地貌发育阶段判识方法研究——以泥河沟流域和枣子沟流域为例

为更加准确判识小流域地貌发育阶段，以黄土高原综合治理小流域——陕西省淳化县泥河沟流域和乾县枣子沟流域为例，分别应用盒分维方法和Horton分维方法进行水系分维值的计算，并利用面积高程积分和地貌信息熵进行验证。结果表明，泥河沟和枣子沟流域水系盒分维值分别为1.886和1.827。根据Strahler曲线积分值和地貌信息熵方法验证结果表明，盒分维方法计算的水系分维值对流域地貌发育阶段的判识更加准确、可靠；这2个流域地貌处于侵蚀发育阶段的壮龄期，其生态敏感性整体上处于较低水平，生态环境抗干扰能力增强并趋于更加稳定的状态。     

北疆盐碱地空间分布特征分析

为了探究北疆盐碱地空间分布过程中盐碱化程度与经度、纬度及海拔高度之间的关系，基于1985年土壤调查结果，结合2015年Landest 8遥感解译去除人工绿洲结果，采用2 km×2 km网格单元，以盐碱地面积占总面积的比例作为检验区域盐碱化程度的指标，对盐碱地分布情况进行统计和分析。结果表明，北疆地区盐碱化程度受地形和降水的影响明显，特别是受土壤类型的影响更为密切；北疆地区盐碱化程度，由西向东呈增大趋势（P=0838），主要集中分布在E90°～E96°范围内，盐碱土占总面积的比例为7562%；由南向北呈减小趋势（P=-0768），主要集中分布在N40°～N43°范围内，盐碱土占总面积的比例为7782%；由低到高呈减小趋势（P=-0767），主要集中分布在-160～500 m范围内，盐碱土占总面积的比例为4741%。北疆盐碱地空间分布特征的分析对于揭示北疆盐碱化程度的变化规律，促进北疆盐碱土资源的合理开发和维持地区生态安全具有重要的意义。     

乌海市平沟煤矸石山小地形土壤养分分析

文章以乌海市平沟煤矸石山上平台和边坡两种不同小地形上的土壤为研究对象,通过野外调查取样和室内分析化验,研究煤矸石山两种小地形对土壤养分的恢复情况。结果表明,土壤有机质、全N、碱解N含量在两种不同小地形上表现为边坡>平台,土壤P素、K素含量表现为平台>边坡,总体而言,边坡上土壤养分恢复效果比平台好。平台和边坡上土壤养分含量在不同土层深度中均表现为:0~20 cm层>20~40 cm层。通过参考土壤养分分级与丰缺度标准,目前土壤养分丰缺度主要呈现出缺或极缺状态。     

基于GIS技术的小型水库规划方法

在小流域治理中，为了提高水库规划的精确度和速度，提出了基于GIS技术来实现小型水库规划的方法。主要是基于GIS技术的库客曲线的制作方法；小型水库规划的可视化。在GIS中，真实地形在计算机中的表达用数字高程模型(DEM)表示，水库规划的三维可视化环境的实现需利用0penGL技术。     

蝴蝶多样性与地形相关性研究——以大峪流域为例

蝴蝶物种丰富度是蝴蝶多样性研究的热点之一,以大峪流域的蝴蝶为研究对象,借助GIS技术,结合数字高程模型（DEM）数据,研究了大峪流域内的蝴蝶多样性沿海拔梯度分布格局,及其与地形复杂度之间的关系。结果表明：随着海拔的升高,蝴蝶的科、属、种丰富度和密度均呈逐渐降低的趋势;蝴蝶的丰富度和密度与地形复杂度成正相关,随地形复杂度的降低而降低。     

黑土区基准坡长和LS算法对地形因子的影响

该文结合小区实测坡长资料及Mc Cool数据,对地形因子算法中涉及的基准坡长影响和不同算法计算值的特征进行了讨论。研究表明,在坡长较小的情况下,20和22.13 m基准坡长计算得到的坡长因子相差不大,但随着坡度增加,在坡长指数的复合影响下,两者的差异渐趋增大。理论分析表明,坡长指数采用与坡度相关的变值更为合理。通过与实测数据对比发现,修正版通用土壤侵蚀模型(RUSLE)算法中的坡长因子与其更为接近,结合与Mc Cool数据的对比分析表明,研究区坡长指数更适合细沟和细沟间侵蚀比率中等的情形,或者采用RUSLE模型算法计算得到。同时研究发现,张宪奎算法、Moore算法、Desmet算法和B?hner算法计算得到的LS因子值都要比参照值小,而且4种算法与参照值的接近程度依次降低。空间分布特征而言,栅格累计算法总体较为破碎,并在平直坡面出现较多平行分布条带,而含有面积指标的其他3种算法则总体呈现光滑连续特性,但有无数据区域的存在。该结果对于研究区土壤侵蚀模型地形因子算法选择具有一定的现实意义。     

石蜡-松香包膜尿素的形貌及其释放行为的研究

以石蜡-松香混合物作为包膜材料，以磷酸氢钙为调理剂，采用熔融喷雾包涂的方法制备一种新型、多营养、不污染土壤的缓释尿素。用水浸泡法和土壤培养法探讨了包膜尿素的释放特性，用扫描电子显微镜研究了包膜尿素的表面和截面形貌。分析了松香与石蜡的配比、涂层量对包膜尿素养分释放速率的影响。结果表明，松香与石蜡的配比是影响包膜尿索养分释放速率的主要因素，涂层量是影响尿素释放的重要因素，包膜尿素在水中氮索的释放行为可用一级释放动力学方程来描述；其中，CRC-25和CRC-30包膜尿素在水中溶出80％的氮素分别需要10．07d、17．88d，在土壤中溶出80％的氮索所需要的时间大于130d；包膜尿素的扫描电镜照片显示，包膜层中的缝隙小于5μm。     

Temporal and spatial dynamics of mineral levels of forage,soil and cattle blood serum in two semi-arid savannas of South Africa

In this study, we examined temporal and spatial dynamics of minerals of forage, soil and cattle serum in two savannas (valley and plain) of South Africa. The aims were to explore the relationships between ecosystem components, and plan communal grazing and fodder flow for sustainable livestock production. In each area, grazing sites near, at intermediate distance from (middle) and far from homesteads were selected. In the valley land, site interacted with season to influence local variations (P<0.05) of soil calcium and microelements. In the plain lands, local variations occurred for soil phosphorus and magnesium. At the large scale, most macro-minerals showed differences between the valley and plain lands. In the valley areas, forage calcium differed (P<0.05) locally in the dry season, whereas in the plain areas, potassium and phosphorus showed local variations (P<0.05) in the wet season. Seasonal variations of most forage elements were significant within each local site of both study areas. All forages were deficient in phosphorus and copper. Cattle serum from the valley area had low iron concentrations. The study concluded that biotic and abiotic factors may influence the distribution of soil and forage elements, but their effects may vary between the two areas. Rangeland improvement and supplementation strategies are suggested to sustain animal production.     

Relationship between Oil Palm Yield and Soil Fertility as Affected by Topography in an Indonesian Plantation

Abstract

Typically, Indonesian oil palm plantations rest on rolling topography. There is limited information on how topography affects soil fertility and oil palm yields. A study was conducted to evaluate these relationships in a commercial oil palm plantation located in South Sumatra, Indonesia. Two sites with differing past management history and fertility regimes were each partitioned into three topographic positions. At each topographic position, yields were recorded at 10‐day intervals over a period of 2 years. Leaf and soil samples were collected from corresponding points spaced at 36.4 m (x direction) and 8.7 m (y direction) using a systematic scheme. Leaf analysis was performed to quantify nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca), and soil analysis was carried out to determine pH, organic carbon (C), extractable P, exchangeable K, Mg, and Ca, effective cation exchange capacity (ECEC), and texture. The collected data were subjected to exploratory, univariate, and bivariate analyses, as well as analysis of variance. Empirical production functions based on measured variables were defined for each topographic position. Results showed that average yields at both study sites varied with topographic position. At site 1 (Sungai Pelepah Estate), the sideslope and the summit consistently gave higher yields than the toeslope. At site 2 (Sri Gunung Estate), a yield gradient was observed with the highest yield occurring at the toeslope and the lowest yield from the summit. Soil fertility varied across topographic positions at both sites. The measured leaf/soil variables showed varying levels of optimality/sufficiency across topographic positions. In most cases, leaf and soil variables showed comparable performance as yield predictors. Validation of the calibrated models showed reasonable accuracy for the toeslope of site 1 and all three positions at site 2.     

Spatial variability and change in soil organic carbon stocks in response to recovery following land abandonment and erosion in mountainous drylands

This research investigates the impact of human activities on carbon (C) dynamics in a mountainous and semi‐arid environment. Despite the low C status of drylands, soil organic carbon (SOC) is the largest C pool in these systems and therefore may offer significant C sequestration potential in systems recovering from degradation. Nevertheless, quantification of this potential is limited by lack of knowledge concerning the magnitude of and controls on regional SOC stocks. Therefore, this study aimed to (i) investigate the variability of soil organic carbon in relation to recovery period and key soil and topographical variables, and (ii) quantify the effects of recovery period following abandonment on SOC stocks. Soil profiles were sampled in the Sierra de los Filabres (southeast Spain) in different land units along geomorphic and degradation gradients. SOC contents were modelled using recovery period and soil and topographical variables. Sample depth, topographic position, altitude, recovery period and stone content were identified as the main factors for predicting SOC concentrations. SOC stocks in 1 m depth of soil varied between 3.16 and 76.44 t/ha. Recovery period (years since abandonment), topographic position and altitude were used to predict and map SOC stocks in the top 0.2 m. The results show that C accumulates rapidly during the first 10–50 yr following abandonment; thereafter, the stocks evolve towards a steady‐state level. The erosion zones in the study area demonstrate greater potential to increase their SOC stocks when abandoned. Deposition zones have greater SOC values, although their C accumulation rate is lower compared with erosional landscapes in the first 10–50 yr following abandonment. Therefore, full understanding of the C sequestration potential of land use change in areas of complex topography requires knowledge of spatial variability in soil properties and in particular SOC.