【作者】 贾国梅；

【导师】 王刚；

【作者基本信息】 兰州大学 ， 生态学， 2006， 博士

【摘要】 土地退化是土地持续性利用的主要威胁,土地退化降低植被的实际和潜在的覆盖度。土壤利用和植被覆盖对生态环境有重要的影响,改善土壤物理化学和微生物大小、活性和微生物群落结构有利于土地的持续性利用和退化土地的恢复。本文从恢复黄土高原退化地土壤肥力的角度出发,将农田和干扰较轻,从未开垦的原生植被作为对照,研究植被自然恢复过程中土壤物理化学和微生物大小、活性和微生物群落结构的变化以及植物物种变化和地上生物量变化与土壤养分和微生物大小、活性和微生物群落结构之间的关系;研究人工种植油松后随着植被次生演替土壤物理化学和微生物量的变化动态;同时分析了施用化肥对土壤养分和微生物大小的影响。主要研究结果如下: 1.耕地弃耕后随着植被的自然恢复演替,地上植物多样性和均匀度逐渐增大,第10年达到最大,随后有所降低,植物物种丰富度随着植被自然演替逐渐提高,而地上生物量在植被演替初期即3年弃耕地比较高,5年弃耕地有所降低,5年后又逐步提高。 2.耕地弃耕后,随着植被自然恢复演替,土壤表层有机碳(OC)、全氮(TN)、碳氮比、碳磷比、氮磷比、微生物碳氮(MBC,MBN),总FAME生物量、真菌生物量、真菌/细菌、放线菌和革兰氏阴性菌生物量逐渐提高,微生物代谢熵和MBC/OC和MBN/TN以及MBC/MBN都没有明显的变化趋势。相关性分析表明,土壤微生物碳氮、总FAME生物量与土壤有机碳、全氮含量之间互相之间具有显著的正相关性,说明土壤肥力和土壤微生物量之间具有紧密的联系,总FAME生物量和微生物碳氮是该研究地的土壤肥力的良好指标。三种类型土壤利用和植被覆盖相比,土壤表层的有机质和微生物碳氮含量、总FAME生物量、真菌生物量、真菌/细菌和革兰氏阴性菌生物量是农田的最低,原生植被的最大,而各弃耕地处于中间状态。结果表明耕地弃耕后植被自然恢复演替有利于土壤表层肥力的提高。 3.随着土壤深度的增加,除农田、3年弃耕地和面向东的原生植被外,各弃耕地和原生植被的土壤有机碳、全氮、微生物碳氮、MBC/OC、MBN/TN、总FAME生物量、革兰氏阴性菌生物量都逐渐降低,而微生物代谢熵、革兰氏阳性菌和放更多还原

【Abstract】 Soil degradation is a major threat to sustainable use of soil ecosystem, because it decreases actual and potential level of vegetation cover. Local land use and land-cover change can play a pivotal role in environmental and ecological changes and furthermore contributes to global change. Consequently, improving the physical, chemical and microbial properties of degraded soil is very important for sustainable use of soil ecosystem. The results showed:1. After abandonment of agricultural land, with vegetation succession plant species diversity and evenness increased gradually, and tended to be the highest contents under 10-yr fallow. after that they decreased, whereas plant species richness increased gradually, and above-ground biomass was higher under 3-yr fallow than that of under 5-yr fallow, after 5-yr fallow above-ground biomass increased gradually.2. With vegetation succession organic carbon (OC), total nitrogen (TN), ratio of organic C/ total P (C/P), ratio of total N/total P (N/P), microbial biomass carbon (MBC), N (MBN), total FAMEs, fungal biomass, ratio of fungal to bacterial biomass, actinomycetes biomass and Gram-negative bacterial biomass in the topsoil (0-10cm) increased gradually, whereas there were no trends in metabolic quotient, MBC/OC and MBN/TN. Soil organic C and total N in the topsoil showed a positive correlation with microbial biomass C, N, and total FAMEs, suggesting that there was close relationship between soil fertility and microbial biomass, that total FAMEs and microbial biomass were potentially good indices of soil fertility in study area. The chemical and microbial properties measured in soil were significantly higher in the virgin vegetation than those of arable land, with various fallows being intermediate. Organic C and TN in the 10-30cm at various fallows were higher compared with arable land, while the accumulation of microbial biomass C, N mainly occurred in the topsoil. Therefore, the results showed that soil fertility may be improved, while total P may become the limiting factor relative to C and N with vegetation succession after abandoned arable land.3. With soil depths, the OC, TN, MBC, MBN, MBC/OC, MBN/TN, total FAME, and Gram-negative bacterial biomass readily decreased, metabolic quotient, actinomycetes biomass and Gram-positive bacterial biomass gradually increased except for arable land, 3-yr fallow and virgin vegetation facing east which were higher in the 10-30cm than other depths, suggesting that microbes inhabiting the deeper soil horizons were more carbon limited than surface-dwelling microbes.4. Plant species diversity and richness index showed a positive relationship with C/N, fungal biomass, ratio of fungal/bacterial biomass. Above-ground biomass showed a positive relationship with organic C, total N, C/N, total FAMEs and fungal biomass in soil, a negative relationship with metabolic quotient, no significantrelationship with microbial biomass C, N. Therefore, the results showed that that plant above-ground biomass affected the active microbial biomass, but not microbial C, N, that C/N in soil increased readily with plant species diversity, that microbial communities changed and fungi became gradually the dominated species of microbial community with succession.5. The effects of fertilization combined with crop rotation on the chemical properties and microbial biomass was investigated in the central Loess Plateau, China. In order to create a more uniform experimental environment and avoid the influence of different crop residues on effects of fertilization, wheat/potato (W/P) rotation was selected in fertilization treatment. The results showed that fertilization could increase organic carbon, total nitrogen, MBC and MBN content compared to the control. It was concluded that appropriate land management such as fertilization combined with crop rotation would be helpful to improve or maintain soil fertility.6. Microbial biomass, organic carbon, total nitrogen, and microbial quotient (MBC/Corg) in soil were determined during the secondary forest succession in north Ziwulin region in the middle of Loess Plateau. The results showed that with secondary forest succession organic carbon (Corg), total nitrogen (TN), microbial biomass carbon (MBC) and N (MBN) in soil increased quickly, and tended to be the highest contents under SF17 (17-year secondary forest), after that they decreased and gradually remained at a quite constant level, suggesting that accumulations of organic C, total N, MBC and MBN in soil occurred mainly at the early succession stages (before SF17). Soil microbial biomass was markedly correlated with the organic carbon and total nitrogen content of soil (p<0.01), Furthermore, microbial quotient showed significant correlation not only with MBC and organic C, but also with succession duration during the secondary forest succession. Therefore, the results suggested that changes in microbial biomass in soil were related not only to the quantity, but also to the quality of soil organic matter during secondary forest succession, and that changes in above-ground plant species during succession were critical to improve degradation soil physical, chemical and microbial properties in north Ziwulin of Loess Plateau.更多还原