【作者】 王小利；

【导师】 吴金水；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2006， 博士

【摘要】 黄土高原是我国主要生态脆弱区之一,多种不利因素(干旱、水土流失、植被退化等)制约着该区土壤有机碳的积累,亚热带丘陵区自然资源和环境条件的综合生产潜力明显高于黄土高原地区。系统研究两大区域土壤有机碳的积累差异并探讨其主要控制因子对于黄土高原和亚热带丘陵区土壤肥力调控和生态环境建设具有重要意义。本研究以黄土高原的燕沟样区和亚热带丘陵区北部的盘塘样区和南部的肯福样区为例,通过对土壤表层(0～20cm)取样分析,分析两大区域土壤有机碳及其活性组分的积累差异,并探讨土地利用、地形和植被等关键控制因素对土壤有机碳积累的影响,其主要结果如下:1.黄土高原样区土壤有机碳含量均值为7.50g/kg,以林地(9.88g/kg)最高,草地次之(6.51g/kg),旱地(4.67g/kg)和果园(4.33g/kg)较低,林地土壤有机碳变异系数较大,果园较小,均属于中等变异。各土地利用方式下土壤有机碳和全氮均呈极显著正线性相关。土壤碳氮比以林地最高,草地、旱地和果园之间无显著差异。土壤可溶性有机碳、微生物生物量碳和有机碳之间总体呈极显著正相关。说明该区退耕还林还草对土壤有机碳积累具有积极作用,果园建设不利于表层土壤有机碳的积累。地形断面可以直观地展示土壤有机碳的地形分异特征。不同地形单元土壤有机碳含量为梁峁顶<中部坡<沟谷底。坡向对林草地土壤有机碳含量有显著影响,对旱地和果园则无明显影响。自然恢复草、灌、乔地段的土壤有机碳含量显著高于相应的人工恢复植被。坡耕地坡面的上、中、下三个坡位土壤有机碳含量基本一致;多年生黄刺玫坡面的土壤有机碳含量显著提高且从上到下逐渐降低;多年生刺槐和小叶杨坡面的土壤有机碳含量也显著高于坡耕地,且呈中间高,上下部低的分布模式。黄土高原各地土壤有机碳含量均以林草地较高,旱地和果园较低。旱地和果园利用方式下土壤有机碳含量由南部向北部逐渐减少,林地和草地利用方式下均以子午岭最高,燕沟、固原和王东沟居于中间,安塞最低。黄土高原不同地区之间气候、植被和土壤的地带性差异是其土壤有机碳积累差异的主要原因。2.亚热带丘陵北部样区土壤有机碳含量均值为12.75g/kg,以水田最高(16.04g/kg),旱地次之,果园和林地(9.48g/kg和8.36g/kg)较低。亚热带丘陵南部样区也以水田最高,旱地和林地次之,果园最低,其土壤有机碳含量比北部样区总体高37.5%,其中水田、旱地、果园和林地利用方式下分别高31.0%、55.8%、40.5%和117.7%。土壤全氮更多还原

【Abstract】 The Loess Plateau region is one of the friable regions in China and there are many factors limiting the accumulation of soil organic carbon (SOC), such as aridity, erosion and vegetation degradation, and so on. The agricultural productivity of subtropical hilly region is superior to the Loess Plateau distinctly. Therefore, study of the SOC contents differences of two regions and its key controlling factors is of great important for the soil fertility regulation and controlling of the farmland in China. Taking Yangou watershed in the Loess Plateau and Pantang area and Kenfu area in subtropical hilly region of China as examples, the contents of SOC and its active components of surface soils (0~20cm) were studied based on the field surveys and the impacts of the key controlling factors, such as land use, landform and vegetation on SOC were discussed in this study. The main results were as follows:1. Mean SOC content was 7.50 g/kg in Yangou watershed in Loess Plateau. Mean SOC content of the woodland was the highest (9.88g/kg), those of the dry land and orchard were the lowest (4.67g/kg and 4.33g/kg), and those of the grassland were in the middle. The coefficients of variation of SOC of the woodland was higher and those of the orchard was lower, belonging to moderate variation. There were significant positive correlations between SOC and total nitrogen (TN) under different land uses in the area. Soil C/N ratio of the woodland were the highest and there were no significant differences among those of the grassland, dry land and orchard. There were significant positive correlations among soil dissolvable organic C (DOC) and microbial biomass C (MBC) and SOC in the area. The study indicated that conversion of farmland into woodland or grassland promoted the accumulation of SOC distinctly and orchard constructions accelerated the decomposition of surface soil organic C in the area. The cross sections of a small valley can visually express the distribution of SOC in three landforms. Mean SOC content of the tableland in Yangou watershed was the lowest, that of bottomland was the highest, and that of slope land was in the middle. Aspect affected significantly the SOC contents of the woodland and grassland, with no significant effects on those of dry land and orchard. The SOC contents under the condition of natural recovery of grasses, bushes and woods were significantly higher than that under man-built vegetation. For the slope dry land, the SOC content was low and similar along the slope. For更多还原