黄土高原水蚀风蚀交错带坡耕地土壤风蚀特征

黄土高原水蚀风蚀交错带受风力及水力共同作用,是世界上土壤侵蚀最严重区域之一。研究通过选取神木县六道沟流域迎风坡和背风坡4块坡耕地,所选样地进行留茬和翻耕处理,利用~7Be示踪技术测试表层土壤样品(0—20 mm),估算土壤风蚀速率,以期阐明坡面风蚀速率空间分布特征,明确有效防治风蚀的农田耕作措施。结果表明:迎风坡风蚀速率显著高于背风坡(p0.05),留茬可显著减少坡面风蚀速率(p0.05),迎风坡翻耕地、迎风坡留茬地、背风坡翻耕地和背风坡留茬地平均风蚀速率分别为778.2,388.4,78.5,4.7 t/(km~2·a)。风蚀速率沿坡面由上而下均呈现递减趋势,且留茬地更为显著。4块样地风蚀速率等值线的局部形变显示了坡面的微地貌变化,其中以留茬地更为明显且出现高侵蚀中心和沉积中心。因此,为有效防治该区域的土壤风蚀,建议采取秋收后留茬、春季播种前翻耕的方式,并根据坡向和作物类型等调整留茬高度。     

黄土高原水蚀风蚀交错带小流域治理模式探讨

黄土高原水蚀风蚀交错带为强烈侵蚀地区,也是黄河下游河床粗泥沙主要来源区。该地区生态环境脆弱,治理难度大;另一方面,区域内蕴藏有丰富的煤炭资源,到21世纪将建成世界级煤田。鉴于治黄和煤田开发的紧迫需要,本区迎来了以水土保持为中心环境整治的新机遇。根据工矿交通社会经济发展的新形势,以神木县六道沟小流域为试区,探讨了工矿业与农业相结合,生态效益与经济效益同步发展,农林牧生产走向商品化,走向市场的综合治理模式和系统工程。     

黄土高原水蚀风蚀交错带小流域土壤水分季节变化特征与主控因素

土壤水分是黄土高原水蚀风蚀交错带生态环境恢复的关键因子,具有明显的时空异质性.以水蚀风蚀交错带的代表性流域—老爷满渠小流域为对象,采用网格法(50 m×50 m)共布设了73个样点,原位观测0—5 m土壤含水率,共测定23次(2013年6月至2019年10月),通过获取每个样点的环境因子,结合经典统计、地统计、随机森林...     

黄土高原王东沟小流域土壤表层全磷空间变异性

[目的]分析黄土高原小流域尺度地貌单元和土地利用方式对全磷空间变异的影响。确定全磷空间变异规律,为土地生产管理提供依据。[方法]2017年在黄土高原王东沟小流域采集了267个土壤样品进行了分析研究。用ArcGIS 10.2绘制样点全磷含量分布图,并分析不同地貌单元和土地利用方式下全磷含量的空间变异特征。[结果]王东沟小流域内不同地貌单元下全磷含量呈现为:塬面塬坡沟道的分布规律,不同的土地利用类型下全磷含量呈现为:果园废弃果园农地林地荒草地的分布规律。土地利用方式和地貌单元对全磷空间变异的影响极为显著。[结论]王东沟小流域土地利用经过14a不断的调整,全磷的含量有了大幅度的提升,土地利用方式显著改变了全磷的空间分布格局。     

水蚀风蚀交错带土壤-植被系统氮素空间变异特征

采用经典统计学和地统计学相结合的方法,分析了黄土高原水蚀风蚀交错带本氏针茅草坡地土壤—植物系统氮素沿坡面的分布,并从不同空间尺度研究了土壤—植物系统氮素的空间结构特征,以揭示水蚀风蚀交错带草坡地土壤—植物系统氮素分布特征。研究结果表明,随坡位的降低,草坡地植物生物量、植物氮含量和储量均逐渐增加;土壤有机质和全氮含量在坡上部和坡中部相近,但均低于坡底部;土壤硝态氮和铵态氮含量沿坡面呈先降低而后在坡底部迅速增加的变化趋势。这些变量的变异系数除硝态氮和铵态氮以坡中部最小外,均以坡底部最小,表明坡底部土壤—植物系统氮素分布最为均匀。各变量的最佳拟合模型在3个分析尺度上均保持一致,且随分析尺度的增加,块金常数、块金效应逐渐增大,样点间的空间依赖性逐渐减弱,空间相关性减弱。表明水蚀风蚀交错带草坡地土壤—植物系统氮素在不同尺度上空间结构比较稳定,属中等或强空间相关性,其空间变异主要来源于结构性因素。     

神木水蚀风蚀交错带退耕坡地土壤水分空间变异性研究

运用统计学方法,对黄土高原神木水蚀风蚀交错带退耕坡地土壤水分空间变异性及其影响因子进行研究. 结果表明(1)土壤水分含量在垂直剖面方向表现出随深度增加,土壤水分含量呈增加趋势,在100 cm土层内变异最大,在100 cm以下其变化的梯度基本趋于稳定;(2)土壤水分含量沿坡长方向(即坡顶到坡下)呈波浪状递增趋势,且在各坡位变异程度不一,呈现出变异程度为坡上＞坡中＞坡下的趋势;(3)土壤水分含量沿垂直于坡长方向表现为阴坡＞山脊＞阳坡的明显趋势,其变异程度表现为阳坡＞阴坡的趋势.本文对神木水蚀风蚀交错带退耕坡地土壤水分的研究有助于了解退耕地土壤水分的变异特征,为区域环境治理和植被建设提供科学依据.     

黄土高原小流域土壤有机碳空间变异性研究

Soil organic carbon (SOC) has great impacts on global warming, land degradation and food security. Classic statistical and geostatistical methods were used to characterize and compare the spatial heterogeneity of SOC and related factors, such as topography, soil type and land use, in the Liudaogou watershed on the Loess Plateau of North China. SOC concentrations followed a log-normal distribution with an arithmetic and geometric means of 23.4 and 21.3 g kg^-1, respectively, were moderately variable (CV = 75.9%), and demonstrated a moderate spatial dependence according to the nugget ratio (34.7%). The experimental variogram of SOC was best-fitted by a spherical model, after the spatial outliers had been detected and subsequently eliminated. Lower SOC concentrations were associated with higher elevations. Warp soils and farmland had the highest SOC concentrations, while aeolian sand soil and shrublands had the lowest SOC values. The geostatistical characteristics of SOC for the different soil and land use types were different. These patterns were closely related to the spatial structure of topography, and soil and land use types.     

水蚀风蚀交错带坡面土壤入渗特性的空间变异及其分形特征

研究在水蚀风蚀交错带的强烈侵蚀中心陕北神木县六道沟流域进行。在一个自然完整坡面上网格布点,采用双环定水头入渗法研究了坡面土壤的入渗特性,在应用传统统计学方法的基础上,将分形理论和地统计学方法结合起来对坡面土壤入渗特性的空间变异进行了研究。获得以下结论:(1)稳定入渗率、平均入渗率和前30 min累积入渗量等三个参数的变异系数分别为0.48、0.36与0.40,在坡面上的变异程度属于中等变异性;(2)三个参数的分维值D分别为1.88、1.92与1.85,样本之间土壤特性值的差异较小,短距离的变异影响占主导地位;(3)研究的土壤在一定的空间范围内具有分形特征。稳定入渗率、平均入渗率与前30 min累积入渗量的自相关范围分别为20~120 m2、0~140 m与40~100 m。     

黄土高原水蚀风蚀交错带不同立地条件下土壤呼吸特征

水蚀风蚀交错带是黄土高原土壤侵蚀最严重地区,该地区立地条件复杂,土壤质地有较大的空间变异性,对生态系统碳循环过程产生重要影响。该文选取土壤质地为立地条件的主要参考因子,利用便携式CO2分析仪对黄土高原水蚀风蚀交错带不同立地条件下2种典型灌木(柠条和沙柳)土壤呼吸特征进行了连续2a的野外对比研究,分析不同立地条件下灌木林地土壤呼吸之间的差异,阐明土壤呼吸的动态变化及其对土壤温度的敏感性。结果表明:在不同立地条件下,柠条林地黄绵土土壤呼吸高于风沙土,相反,沙柳林地风沙土土壤呼吸高于黄绵土。每种灌木林地在不同立地条件下土壤呼吸呈现明显的季节性变化,土壤呼吸速率的高峰值出现在7、8月份。不同立地条件下土壤呼吸与土壤温度呈现显著指数函数关系,每种灌木林地黄绵土土壤呼吸的温度敏感性系数Q10高于风沙土,从而对土壤温度的响应更为敏感。     

黄土高原水蚀风蚀交错带沟岸灌木林地土壤水分变化

选择黄土高原水蚀风蚀交错带典型切沟,采用人工取样和中子仪测定研究了柠条坡地不同坡位土壤水分变化,明确了切沟对沟岸柠条林地土壤水分的影响范围,建立了土壤储水量与距沟沿不同距离之间的关系。结果表明：在黄土高原雨季(7～10月),天然降水对柠条坡地下位的补给深度达到了220 cm,对坡地上位和中位的补给深度分别为180 cm和160 cm。在土壤剖面200 cm深度范围内,坡下位土壤水分含量始终高于坡上位和坡中位,200 cm深度以下,坡地上、中、下位土壤水分趋于一致。切沟对柠条林地土壤水分影响水平宽度达到3～4 m,垂直深度达到6 m以下。沟岸柠条坡地距沟沿不同距离土壤剖面储水量与沟沿距离间的关系可以用线性函数来表达。研究沟岸地距沟沿不同距离的土壤水分变化规律对沟岸地植被的恢复具有重要的科学意义。     

黄土高原水蚀风蚀交错带六道沟小流域坡面表土钙质结核分布

量化坡面钙质结核分布,有助于深化对黄土高原水蚀风蚀交错带特定土壤类型(含钙质结核土壤)中水土过程的认识.本研究通过对坡面不同部位的表层土壤(0～20 cm)颗粒组成、钙质结核质量分数和植被地上生物量、盖度、丰富度及多样性指数的测定和分析,研究了坡面钙质结核的分布及影响因素.结果表明:土壤黏粒体积分数沿坡面呈逐渐降低趋势;钙质结核质量分数沿坡面呈单峰曲线分布,在坡面1/4～1/3的位置(距离坡顶20～30 m)处,达到峰值(10％～15％).钙质结核质量分数与坡度呈线性正相关,与植被地上生物量(盖度)呈单峰曲线关系,峰值即为植被影响钙质结核质量分数的临界点,临界点处的植被盖度在11％～16％之间.影响坡面钙质结核分布的最主要因素为坡度和植被;小尺寸的钙质结核在坡面分布范围最广、数量最多,起决定作用的钙质结核尺寸在5～ 15 mm之间.坡面钙质结核质量分数及分布反映了径流、植被和钙质结核之间的相互作用关系,钙质结核质量分数可以用来指示坡面的土壤侵蚀状况.     

黄土高原风蚀水蚀交错带沟岸对柠条林地土壤水分的影响

The most serious erosion on the Loess Plateau of China exists in the wind-water erosion crisscross region where the annual precipitation is about 400 mm, the ecological environment is very fragile, and water is the key limiting factor for improving the environment. In this study, changes of soil moisture content for Caragana korshinskii Kom. shrubland in the gully bank of the Loess Plateau were studied using the methods of soil sampling and neutron probe. A typical gully （75 m long, 28 m wide, and 10 m deep） was selected, and six neutron probe access tubes （6 m long） were installed at points 50, 100, 200, 300, 400, and 500 cm from the gully border for obtaining soil moisture data from July to October 2004 at approximately 10 d intervals. Soil samplings were simultaneously carried out for moisture determination at the six points. Results showed that the soil moisture of the shrubland in the gully bank significantly varied between 300 and 400 cm in the horizontal direction and up to 600 cm in vertical direction of the gully. Seasonal changes in soil moisture revealed a curve with a single peak that occurred at the end of August or early September. A linear regression equation was fit for soil water storage and the distance from the gully border, with coefficients depending on rainfall characteristics, sampling point, and time of measurement.     

黄土区不同土地利用方式坡面土壤含水率的空间变异性研究

为掌握不同土地利用方式下坡面土壤含水率的空间分布特征及其变异规律，利用经典统计学方法对黄土高原水蚀风蚀交错带草地和农地坡面土壤含水率的空间变异性进行了对比研究。结果表明：草地和农地的土壤含水率均值在同一土层深度下差异极显著，但二者在垂直方向、坡长方向的变异程度均为中等变异程度；草地和农地坡面土壤含水率的垂直变化特征不同，前者为降低型，后者在100 cm以上为波动型，以下为稳定型；草地和农地坡面土壤含水率均随坡长的增加呈波浪式变化规律，整体上有增加趋势；将坡面划分为5个坡长或将土层划分为4层以后，草地和农地坡面土壤含水率沿垂直方向、坡长方向的总体变化趋势均没有改变，但由于尺度的扩展获得了一些较大尺度上的水分信息。     

黄土高原小流域土壤水分及全氮的垂直变异

为了研究黄土高原土壤中水分及全氮垂直分布及变异情况,对陕北神木县六道沟小流域中苜蓿地、荒草地、农地、柠条地以及油松地5种不同植被类型下0～800 cm土层中土壤含水率和土壤全氮进行了测定和分析。土壤含水率在垂直方向上呈现出干湿交替的层状分布。植被类型影响土壤水分含量的垂直剖面分布;各植被类型下相对高湿层和低湿层出现的深度不同;不同深度土层平均土壤含水率不同。农地及退耕荒草地土壤水分涵养较好,垂直方向上含水率变化较大;人工植被苜蓿、柠条消耗土壤水分较多,土壤含水率变化相对平缓;油松地平均土壤含水率及变化幅度居中。研究区域中,土壤全氮含量水平较低,表层发生陡降后,在20 cm以下土层中仍以很小的变幅降低,变化平缓。柠条地土壤全氮含量高于其他植被类型。     

近20年来黄土高原水蚀风蚀交错区典型小流域土地利用/覆被变化分析

剖析黄土高原水蚀风蚀交错区小流域不同土地利用/覆被类型的演变方向和程度,是认识该区侵蚀环境演变趋势,评价区域水土流失动态的重要基础性工作.通过收集黄土高原水蚀风蚀交错区典型代表流域——神木县六道沟流域1990、1995、2002年土地利用信息和2010年遥感影像,结合近期实地调查结果,分析该区耕地、林草地和工矿用地等主要土地利用类型在流域内分布格局的变化态势.结果表明:1)1990-2010年,流域林草地面积占总面积比例由35.74％增加到62.79％,耕地面积比例从33.87％锐减至7.61％,坡耕地和旱梯田向林草地大量转移,耕作区域向沟缘线以下沟谷地转移和集中,沟缘线以下耕地面积占耕地总面积比例由13.82％上升至74.04％,工矿用地作业面积由0.28 hm2扩展到14.89 hm2,煤矿开采趋于活跃;2)就影响侵蚀环境演变的流域下垫面条件而言,地表覆被,尤其沟缘线以上坡面植被显著改善,但煤矿开采活动的活跃,一方面对流域内林草生长及土地利用方式存在着极大影响,另一方面,对侵蚀环境的人为恶化起着巨大的促进作用.     

黄土高原北部水蚀风蚀交错带坡面降雨分析

为探明黄土高原北部水蚀风蚀交错带的降雨特点,进而为该地区开展土壤侵蚀、开发利用降雨及地表径流的研究提供科学依据,该文对黄土高原六道沟流域5 a （2006－2010年）雨季的坡面降雨进行了分析。采用Box Car Pro 4.3软件对降雨数据在时间轴上进行分割,分割时间间隔分别为3、5、10 min和1 h,分析了六道沟流域雨季的坡面雨强、降雨历时及降雨量的分布。结果表明,3、5、10 min和1 h时间间隔的最大雨强分别为2.2、2.08、1.68和0.7 mm/min,各时间间隔 5 a内雨季所有降雨历时的平均雨强分别为0.12、0.09、0.06和0.03 mm/min。随着单位时间间隔的增加平均降雨强度降低,各时间间隔的小雨强发生概率远高于大雨强发生概率。3 min时间间隔雨强大于1 mm/min、5 min时间间隔雨强大于1 mm/min、10 min时间间隔雨强大于0.8 mm/min以及1 h时间间隔雨强大于0.4 mm/min发生的概率分别为0.4%、0.2%、0.2%和0.1%。降雨历时小于30 min的降雨事件占总降雨事件的近50%;降雨历时在2 h以上的降雨事件约占总降雨事件的23%,其中降雨历时大于12 h的降雨事件只占总降雨事件的2.6%。降雨量小于等于1 mm 的降雨事件占年均雨季降雨事件的近50%,但其总降雨量不足年均降雨量的7%;降雨量大于20 mm的降雨事件年均5次,其降雨量占年均雨量超过20%。研究结果在一定程度上揭示了黄土高原北部水蚀风蚀交错带的坡面降雨特征。     

Spatial variability of soil organic carbon in a catchment of the Loess Plateau

Abstract

The issue of soil organic carbon (SOC) is of increasing concern. Because SOC, as an important soil component in farming systems, is essential for improving soil quality, sustaining food production and quality, and maintaining water quality and as a major part of the terrestrial carbon reservoir, it plays an important role in the global carbon cycle. In this paper, a total of 665 soil samples from different depths were collected randomly in the autumn of 2007, and the spatial variability of SOC content at a small catchment of the Loess Plateau was analysed using classical statistics and geo-statistical analysis. In nonsampled areas classical kriging was utilized for interpolation of SOC estimation. The classic statistical analysis revealed moderate spatial variability with all five layers of SOC-content. In addition, the average SOC content decreased with soil depth and the relationship can be modelled by an exponential equation (y=3.1795x ^?1.2015, R ²=0.9866) and all of the SOC-content data in the different depth were normally distributed. The geo-statistical analysis indicated a moderate spatial dependence in 0–60 cm, while in the 60–80 cm depth spatial dependence was strong. The semi-variogram could be fitted by an exponential model for 0–10 cm depth; by a spherical model for 10–20 cm depth and 60–80 cm depth; and by a Gaussian model for 20–60 cm depth. The range increases with increasing depth. In addition, classical kriging could successfully interpolate SOC content in the catchment. In general, the geo-statistics method on a watershed scale could be accurately used to evaluate spatial variability of the SOC content in the Loess Plateau, China.     

Effects of land use on soil erosion and nitrogen loss in the hilly area of the Loess Plateau,China

This study examines the effects of land use and slope angle on runoff, soil loss and nitrogen loss from hillslopes of the Loess Plateau in China. Farmland, wasteland and four forest treatments (sea buckthorn+poplar, immature sea buckthorn, mature sea buckthorn, and immature Chinese pine) were the types of land use that were compared. The results showed that July was the critical period for runoff, soil loss and nitrogen loss from farmland. Farmland was the most susceptible land use. Sea buckthorn+poplar, immature sea buckthorn, and mature sea buckthorn limited the runoff, soil loss and nitrogen loss. Farmland on slopes over 15 degrees should be abandoned because of the high erosion rate and nitrogen loss. Copyright © 2003 John Wiley & Sons, Ltd.     

How representatively can we sample soil mineral nitrogen?

Spatial distribution of soil mineral‐N content (N_min) is a scale‐variant process. Precision farming assumes knowledge about the spatial distribution of N_min. Moreover, sampling in management zones is based on the assumption of spatial dependence between sampling points. In the present study, variability structure of N_min and the sources of variability were investigated. Within an agricultural landscape, N_min was investigated across a field in a nested design over four consecutive years. Temporally unstable structure of individual nests require a sampling with several nests in the field. In the investigated field, 35%–49% of the total variability derived from small‐scale variability observed at spatial distances of <5 m and from sampling and analytical errors. Differences between 10 and 26 kg N ha^–1 for the soil depth increment 0–60 cm can be expected. Uncertainty due to analytical errors were in the order of 5–10 kg N ha^–1 for a 0–60 cm layer.