【作者】 包耀贤；

【导师】 吴发启；

【作者基本信息】 西北农林科技大学 ， 水土保持与荒漠化防治， 2008， 博士

【摘要】 坝地和梯田是黄土丘陵沟壑区和残塬沟壑区的基本农田，是群众的“保命田”。二者土壤质量的好坏成为区域农业和经济可持续发展的决定性因素。本研究针对坝地和梯田的土壤质量问题，以延安碾庄沟流域（坝地和梯田）和淳化泥河沟流域（梯田）为研究对象，从资料收集、野外调查和室内土壤物理、化学和生物学质量指标的土样分析入手，结合方差分析、相关性分析、因子分析、逐步回归分析等方法，系统研究了坝地和梯田土壤质量的基本特征、时空分布与演化、相关性、指标体系和综合评价。主要结论如下：1．颗粒组成均为粗粉粒最多（约60％），粗砂粒最少（约5％）；0．01～0．25mm微团聚体占80％以上，＜0．01mm微团聚体占约10％，受粘粒、CaCO₃和有机质影响显著；团聚体总量低（＜12％），水稳性差，受有机质和物理性粘粒影响显著。质地粗化度、团聚度和MWD均为淳化梯田最好，延安坝地和梯田差异很小；团聚度、总团聚体和MWD沿剖面向下降低，但差异较小。含水量延安坝地＞淳化梯田＞延安梯田，水分受物理性粘粒的吸储作用显著，坝地更具备作物稳产高产的水分条件。坝地旋回层次构型对托水保肥和增强抗蚀性极为有利，也衍射出土壤颗粒粗化、抗蚀性减弱的生态变化足迹。2．表层土壤养分含量差异较大。只有全磷和钾素储量丰富，其它养分均属“中”或“低”水平。其中，淳化梯田仅缺碱解氮，延安坝地和梯田基本都缺。养分全量高并非有效养分供应充足。CEC含量淳化梯田为1级（高），延安坝地和梯田为3级（低）；CaCO₃量均高，为6级；pH值显示延安坝地为碱性而淳化梯田和延安梯田属弱碱性。表层有机质、各形态氮素（NO₃^--N除外）、有效性钾、速效钾、速效磷、CEC含量均显著高于下层，下层间差异不显著。其它指标在层次间差异不显著。区域间，除碱解氮外的所有指标含量均为淳化梯田最高。区域内，除了速效磷、CEC、缓效钾和CaCO₃外，其它指标均为延安坝地高于延安梯田。所有化学指标（除了pH值）在细颗粒中均有明显富集，水土流失就是养分的流失。3．受生境条件和生物学性质本身的敏感性影响，生物学指标在区域间的差异并无一致性规律。酶活性、微生物数量、呼吸强度和微生物量C、N、P均沿剖面向下降低，其中，三大菌类数量急剧下降，表现出生境变化的极度敏感性。5种酶活性、MBC、MBN与有机质密切相关。微生物数量细菌（10⁷）＞放线菌（10⁴）＞真菌（10³），其中，细菌占三大菌类数量的99%以上，对有机物质分解起着决定性作用。MBC、MBN和MBP含量虽少，生物有效性却很明显。细菌数量和MBC可较好地反映侵蚀过程。4．坝地和梯田绝大多数土壤物理、化学和生物学质量指标随着经营时间的延续均经历了先逐渐升高后缓慢降低的演变过程，现已处于衰退并将持续衰退的状态。整体来看，各指标拐点年限的出现时段淳化梯田滞后于延安梯田，延安坝地滞后于淳化梯田。5．除容重外，其余9项指标间均呈显著或极显著相关，特别是物理性粘粒协调性较好。17项化学指标间的相关性整体较好，特别是有机质。通径分析显示，全氮主由有机质和C／N比决定；速效磷由CEC、全磷和有机质直接影响；对速效钾的直接影响力为有机质＞CEC＞缓效钾＞全氮；CEC主要决定于有机质、速效磷、全钾和缓效钾。蛋白酶具有拮抗作用，其它酶活性的协调性较好，特别是蔗糖酶。细菌、真菌与脲酶、碱性磷酸酶和蔗糖酶相关性较好；放线菌与过氧化氢酶、蛋白酶相关性较好。MBC受影响的程度MBN＞蔗糖酶＞蛋白酶＞细菌：MBN受影响的程度MBC＞放线菌＞蔗糖酶＞蛋白酶；MBP受影响的程度真菌＞脲酶＞碱性磷酸酶。化学和生物指标的通径分析显示，对有机质的直接效应蔗糖酶＞过氧化氢酶＞放线菌；碱解氮受蔗糖酶直接效应最大；对速效磷的直接效应MBN＞脲酶＞蔗糖酶；速效钾受蛋白酶的直接作用最大。6．筛选出物理性粘粒、质地粗化度、含水量、全钾、有机质、碱解氮、全磷、电导率、CaCO₃、蛋白酶、碱性磷酸酶、细菌和真菌等13项土壤质量综合评价指标。整体看土壤质量等级，淳化梯田属较高水平（Ⅱ级）；延安坝地和延安梯田属中等水平（Ⅲ级），延安坝地稍好于延安梯田。建立了土壤综合质量评价演算模型及其随时间的演化模型。综合土壤质量已处于退化状态，临界年限淳化梯田、延安坝地和延安梯田分别约在33年、40年和22年。更多还原

【Abstract】 Dam land and terrace are basic farmland in hilly-gullied and gullied of Loess region and considered as life farmland. Good and bad on soil quality of them is the decisive factor of regional agriculture and economic sustainable development. This research aimed at the soil quality problem of dam land and terrace, took the Nianzhuanggou watershed of Yan’an City （dam land and terrace） and Nihegou wateshed of Chunhua county（terrace）, Shaanxi province, as the research object, took the collection of materials and data, field investigation, laboratory analysis on soil physical, chemical and biological indicators as a breakthrough point, used methods of variance analysis, correlation analysis, factor analysis and stepwise regression analysis, and systematic research on the basic feature, spatial and temporal distribution and evolvement, correlation, indicator system and comprehensive assessment of soil quality were finished. The main research results were as follows:1. Coarse silt content is the most（about 60%） and coarse sand content is the least（about 5%） in mechanical composition. The microaggregate content of 0.01～0.25mm and <0.01mm accounts for more than 80% and about 10%, respectively, and the content of clay, CaCO₃ and organic matter（OM） had significant infiuence（p<0.01） on microaggregate content. The total content of water-stable aggregate is low（less than 12%） and their water stability is bad, and influenced significantly by organic matter and physical clay（p<0.01）. As a whole, texture coarseness, aggregation rate and mean weight diameter（MWD） of Chunhua terrace（CT） was the best, and that of Yan’an dam land（YD） and Yan’an terrace（YT） was very small difference. The content of aggregation rate, total aggregate and MWD showed decrease of top-down trend in vertical profile, but had no significant differences in profile. Soil water content YD>CT>YT, and it was influenced significantly by physical clay（p<0.01）. Dam land possessed better moisture condition that ensured crops to provide stable and high yields. Cyclothemic hiberarchy of profile in dam land was extremely favorable to preserve soil water and fertility and to increase erosion resistance, this structure illustrated ecological change footprint of particle coarsening and erosion resistance weakening.2. The content of various soil nutrients in topsoil had great differences in study area. The content of total P（TP） and various soil K only was rich in study area, and other content of soil nutrients belonged to "middle" or "low" level, among them, available N（AN） was lack only in CT, and they all lack in YD and YT. High total quantity of nutrient did not mean enough effective nutrients. CEC content of CT was one grade（high）, and that of YD and YT was three grade（low）. CaCO₃ content all belonged to six grade（high）. pH value was alkaline in YD and slightly alkaline in CT and YT.The content of OM, various nitrogens（except NO₃^--N）, available K（AK）, readily available K（RAK）, available P（AP） and CEC in topsoil was highest and their significant differences were found between topsoil and subsoil, but there was no obvious differences in subsoil, the content of other indicator had no significant differences in profile. In inter-area, the content of each indicator（except AN） of terrace in Chunhua was the highest. In intra-area, the content of each indicator of dam land in Yan’an, except AP, CEC, slowly available K （SAK） and CaCO₃, was larger than that of terrace in Yan’an. All chemical properties（except pH） were obviously assembled in fine particles. Water and soil loss meant loss of nutrient.3. Effected by habitat condition and own sensitiveness of biological properties, differences of biological indicator in inter-area had no consistent law. The content of enzyme activities, microorganism quantities, respiration intensity, microbial biomass C（MBC）, MBN and MBP showed decrease of top-down trend in vertical profile, among them, the quantities of three major microorganism dropped suddenly and showed extreme sensitiveness of habitat change. 5 kinds of enzyme activity, MBC, MBN are closely related to OM. Microorganism quantities showed bacterium（10⁷）>actinomyces（10⁴）>fungi（10³）, among three, bacterium’s quantities accounted for more than 99% and it played a decisive role in the decomposition of OM. Although there was poor content of MBC, MBN and MBP, their biological validity was very obvious. Bacterium’s quantities and MBC’s content can better reflected erosion process.4. The overwhelming majority of soil physical, chemical and biological quality indicators increased incipiently and decreased subsequently with the increasing of dam land and terrace use years. They have been degenerate state and degradation will be lasted. As a whole, The critical year of each indicator of terrace in Chunhua hung behind that of dam land in Yan’an, and dam land in Yan’an hung behind terrace in Chunhua.5. Significant or very significant correlations were showed among 10 soil physical indicators（except bulk density）, especially physical clay. The whole correlations of 17 soil chemical indicators were better, especially OM. The results of path analysis of chemical indicators showed that TN was mainly determined by OM and C/N, AP was mainly determined by CEC, TP and OM, the order of direct influence on RAK was OM>CEC>SAK>TN, and CEC was mainly influenced by OM, AP, TK and SAK.Protease had antagonistic effect on other enzyme, significant correlations were found among other 4 enzyme activities, especially invertase activity. There were better correlations between bacterium, fungi and urease, alkaline Phosphatase, invertase, respectively. Catalase and protease are closely related to actinomyces. The influence degree of biological indicators on MBC was MBN>invertase>protease>bacterium, the influence order on MBN was MBO actinomyces>invertase>protease, and the influence order on MBP was fungi>urease>alkaline Phosphatase. The results of path analysis on chemical and biological indicators showed that the order of direct influence on OM was invertase>catalase>actinomyces, the direct influence degree of invertase on AN was largest, the direct influence on AP was MBN>urease> invertase, and the direct influence degree of protease on RAK was largest.6. 13 comprehensive assessment indicators of soil quality were screened out in study area and these indicators included physical clay, texture coarseness, water content, TK, OM, AN, TP, electrical conductivity, CaCO₃, protease, alkaline Phosphatase, bacterium and fungi. Soil quality of CT belonged to "higher" level and was grade two, and that of YD and YT belonged to "middle" level and was grade three. In Yan’an study area, soil quality of dam land was better than that of terrace slightly. Regression computation model and evolutional model changing over time for soil quality comprehensive assessment were established. Comprehensive soil quality have been degenerate state and degradation will be continued, and the critical year was about 33 years in CT and 40 years in YD and 22 years in YT.更多还原