【作者】 王占礼；

【导师】 常庆瑞； 邵明安；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2002， 博士

【摘要】 耕作侵蚀是导致坡地土壤退化，使坡耕地出现严重水土流失极其重要的一种侵蚀，在耕作历史悠久的我国黄土地区表现的尤为突出。耕作侵蚀也是国际土壤侵蚀研究的一个新领域，国内对它的研究极为薄弱。本文以黄土丘陵沟壑区的典型坡地为研究对象，采用人为施放示踪材料进行耕作侵蚀试验、理论推导、测量、¹³⁷Cs示踪、重复耕作、土壤理化分析及数理统计分析相结合的方法，系统定量研究了黄土坡地畜力横坡耕作条件下的耕作侵蚀及其效应，取得了创新性的研究成果，对丰富和推动国际耕作侵蚀及国内土壤侵蚀研究，有效地治理黄土地区坡耕地水土流失和实现土壤可持续利用具有重要理论和实践意义。本研究条件下的主要结论如下： 1．阐明了耕作侵蚀过程中的土壤再分布规律 研究表明，一次耕作造成的耕层土壤水平位移及垂直位移随坡度及深度的变化均可用二元线性相关方程描述；耕作后原耕层土壤距地表深度随耕作前距地表深度及坡度的变化可用二元二次抛物面相关方程描述；一次耕作前后，原耕层深度约1／3处的土壤距地表深度基本不变，小于1／3处的土壤距地表深度增大，大于1／3处的土壤距地表深度减小。 2．建立了不同形式的耕作侵蚀模型 研究表明，耕作搬运量模型是一次耕作导致的单宽耕作搬运土量随坡度变化的线性相关方程；耕作侵蚀模型是一次耕作导致的坡地任何位置耕作净侵蚀模数等于耕层土壤容重、耕作深度、土壤与耕作条件决定的系数与地形曲率的乘积。 各种耕作侵蚀模型均表明，地形是影响耕作侵蚀的主要因素，在特定土壤与耕作条件下，地形则是唯一的因素。一次耕作导致的坡地单宽土壤搬运量只与坡度有关。一次耕作导致的坡地耕作净侵蚀模数，只受坡地地形曲率的影响，与地形因子的坡度和坡长特征无关。耕作净侵蚀主要在复合地形上发生，在耕作过程中，坡地的凸形部位发生净侵蚀，坡地的凹形部位发生沉积，坡地地形越不规则，起伏越大，这种净侵蚀和沉积过程越广泛，越强烈。 3．评价了耕作侵蚀强度及其空间格局 研究表明，研究坡地一次耕作造成的单宽土壤搬运量为24.02—44.58 kg·m^-1。其中，搬运量小于30.00 kg·m^-1的坡段占坡地面积的23.43％，分布在坡地的最上段和最下段，搬运量为30.00—40.00 kg·m^-1的坡段占坡地面积的42.07％，分布在坡地V的中上段和中下段，搬运量大于40.00kg’m一’的坡段占坡地面积的34.5俄，分布在坡地的中段。 研究坡地耕作侵蚀模数主要集中在700一1800 t.km众之间，平均为1 324.33t.kzn一，占坡地面积的49.24%，发生在坡地上部凸形部位;耕作沉积模数主要集中在1200一1800t·km·2之间，平均为1452.77t·km·，，占坡地面积的35.0钱，发生在坡地下部凹形部位;零侵蚀与沉积发生在坡地由上部凸形向下部凹形过渡的部位。 4.分析了耕作侵蚀对艳一137分布的影响 研究表明，研究坡地耕作侵蚀部位土壤中的’37Cs含量在2 16.80-930.O8Bq’‘2之间，平均为525.49Bq’m-2，耕作沉积部位土壤中的’37Cs含量在1004.95一3163.26Bq’m一2之间，平均为2184.72Bq’m-，;研究坡地耕作侵蚀与土壤中的’3ts含量存在着好的负相关性，相关关系可通过指数相关方程描述。 5.揭示了耕作侵蚀对水蚀的影响及对总土壤侵蚀的贡献 研究表明，研究坡地的平均水力侵蚀模数为501.6.51 t.km一a，占坡地面积的88.18%，主要发生在凸型坡面及凹型坡面上部约314的坡段:平均水力沉积模数为1346.50 t.km·，·a，占坡地面积的11.82%，主要发生在凹型坡面下部约114的坡段;水蚀导致的坡地平均土壤流失模数为3844.犯tkm一a，泥沙输移比为0.9689;研究坡地不同地形部位坡度与坡长差异造成的径流变化是导致水蚀空间分异的主要原因，坡度与坡长对水蚀空间变化的影响可通过二元线性相关方程很好地描述。 总土壤侵蚀具有与水蚀相似的特征，但与水蚀相比:侵蚀强度沿坡地投影坡长的变率增大，侵蚀区面积减小，沉积区面积增大，凸形坡段上侵蚀强度增大，凹形坡段上侵蚀强度减小、沉积强度增大、部分坡段由侵蚀变为沉积;坡地平均总土壤流失模数为4400.18 t.km，2.a，总泥沙输移比为0.91:总土壤侵蚀强度空间分异的主要原因转变为坡度、坡长及地形曲率的综合影响，其影响关系可通过三元线性相关方程很好地描述。 在研究坡地，耕作侵蚀与水蚀之间存在着正相关关系，并可以通过抛物线相关方程进行描述;在研究坡地的凸形部位，耕作侵蚀与水蚀皆表现为侵蚀，且水蚀大于耕作侵蚀;在研究坡地的凹形部位，耕作侵蚀均表现为沉积，但水蚀分别表现为侵蚀、水力沉积速率小于及大于耕作沉积速率的沉积。 研究坡地耕作侵蚀占总土壤侵蚀的百分比沿坡地投影坡长的空间分布由坡顶到坡底明显地分为三段，并逐段依次变化:在耕作侵蚀与总土壤侵蚀皆呈侵蚀的部位，VI该百分比的平均值为17.36%，占坡地面积的52.81%，发生在坡地上部呈凸起的部位;在耕作侵蚀表现为沉积，而总土壤侵蚀又表现为侵蚀的部位，该百分比的平均值为-34.42%，占坡地面积的19.28%更多还原

【Abstract】 Tillage erosion is one of soil erosion processes, which may cause soil degradation and further severe soil and water loss on sloping cultivated land. These effects of tillage erosion are very obvious in the loess region of China where tillage history is very long. Research on tillage erosion has become a new area in the world recently, but little has been done in China. This paper, taking a typical sloping land in the loess region of hilly and gully in China as an example, quantitatively study tillage erosion and its effects there in the case of animal powered across-slope tillage operation by tillage erosion experiment in which small cubes are used as tracers of soil displacement, theoretical deduction, measurements, 137Cs tracing, repeated tillage, analyses of soil physics and chemistry, and statistics analyses. The research work has obtained innovational results which are significant in enhancing research on tillage erosion in the World and research on soil erosion in China, promoting efficient management of sloping land, controlling soil and water loss, and realizing sustainable use of soil resources in the loess region of China. The main progresses are as follows:1. Features of soil displacement in-processes of tillage are clarifiedStudy shows that the variations of horizontal and vertical soil displacements per tillage operation with slope gradient and depth can be described with a binary linear regression equation. The variations of soil depth after tillage with its depth before tillage and slope gradient can be described with a binary quadratic paraboloid regression equation. After per tillage operation, depth of soil with about one thirds of tillage depth did not change basically. Depth of soil shallower than one thirds of tillage depth became deeper than before. Depth of soil deeper than one thirds of tillage depth became shallower than before.2. Tillage erosion models for calculating soil flux and erosion intensity are developed Study shows that model for calculating tillage soil flux is a linear regression equationwhich describes relationship between soil flux per unit width per tillage operation at any position of sloping land and slope gradient. The model for calculating erosion intensity is that net soil erosion module (amount per unit area) per tillage operation at any position ofsloping land is equal to products of soil bulk density, tillage depth, coefficient determined with soil and tillage factors, and topography curvature.The tillage erosion models indicate that topography is the major factor affecting tillage erosion. It becomes a controlling factor when conditions of soil and tillage are fixed. The soil flux per unit width per tillage operation on sloping land is only related to slope gradient in a tillage process. The net erosion modulus per tillage operation on sloping land is only affected by topography curvature of the sloping land and is not correlated to slope gradient and slope length. A net erosion is mainly observed in the complex topography. When soil plough is implemented, net erosion is produced on convexities of slope profile and the deposition appears on concavities of slope profile. The more irregular and fluctuant the topography , the more extensive and intense the net erosion and deposition processes.3. Tillage erosion intensity and its spatial pattern are evaluatedStudy shows that soil flux per tillage operation is 24.02-44.58 kg-m’1 on study site. The segments of study site with soil flux less than 30.00 kg-m"1, between 30.00 and 40.00 kg-m’ ’, and grater than 40.00k kg-m"1 account for 23.43%, 42.07%, and 34.5% of the whole slope respectively, and mainly distribute in the upper and the lower parts, the upper middle and the lower middle parts, and the middle part of sloping land respectively.The tillage erosion modulus mainly ranges from 700 to 1800 t-km-2, taking an average of 1324.33 t-km-2 on study site. The net eroded area accounts for 49.24% of the slope, distributing on the convexity located in the upper part of the slope. The tillage depo更多还原