【作者】 刘秉儒；

【导师】 王刚；

【作者基本信息】 兰州大学 ， 生态学， 2009， 博士

【摘要】 土壤作为生态系统中一个重要因子,对于植物多样性的分布和空间格局有着决定性的作用,土壤微生物和生态系统的初级生产力紧密相关,对土壤的发育和功能以及土壤营养的循环起重要的作用。土壤质量的恢复与保育是黄土高原半干旱丘陵区植被建设及生态环境可持续发展的关键之一。探讨黄土高原半干旱地区植被自然恢复期间植被-土壤-微生物的变化规律,对于指导该地区的人工生态恢复具有重要的理论价值与实际意义。本研究围绕兰州南北两山地区“雨养”生态系统恢复重建的重大科学问题,以自然恢复的红砂群落为研究对象,探讨黄土高原红砂植被恢复期间群落结构、土壤微生物和养分特性动态及其相互关系,为“雨养”生态系统保育恢复与重建技术与模式提供理论支撑。该研究运用5级盖度分类法对植物群落和对应的土壤做分析研究,结果表明:1.红砂的个体大小与冠幅有十分密切的关系,与植株高度相关不明显。红砂冠幅(长与宽的乘积,x)与个体地上生物量(y)线性关系非常显著:y=0.764x—0.016(R~2=0.8709 P<0.001)。2.植被盖度和地上生物量逐渐增大的同时植物物种多样性也逐渐增大,总盖度在48.73%(地上生物量为35.62 g/m~2)后虽然植被盖度和地上生物量继续增大,但是植物物种多样性有所降低,个别物种消失,物种多样性分布呈正态型。护理效应可能对物种多样性变化产生了影响。3.植被盖度、地上生物量增加,土壤有机碳(SOC)和全氮(TN)、土壤微生物碳(MBC)和微生物氮(MBN)都有所提高,但是当总盖度超过48.73%(地上生物量35.62g/m~2)之后,SOC、TN、MBC、MBN增加比较缓慢,而且增加的差异不显著。4.相关分析表明,地上生物量与土壤微生物碳、氮(P<0.05);SOC和TN与植被盖度、地上生物量、土壤含水量(P<0.05)以及SOC与TN之间(P<0.05)均有显著的正相关性。SOC和TN与地下微生物量碳、氮均显示正相关(P<0.05),MBC和MBN呈正相关(P<0.05)。MBC与SOC、TN间的相关性表明地上群落结构变化过程中土壤微生物生物量与土壤养分状况关系密切。5.土壤细菌多样性随植被盖度有所增加,在达到48.73%后多样性维持在彼此接近的水平,尽管微生物多样性群落结构有差异。虽然许多相关研究表明,植被决定土壤微生物群落的组成,土壤微生物多样性与覆盖于土壤上的植物群落多样性呈正相关,但是本研究却表明土壤微生物多样性与植物物种多样性不相关。这些结果说明,在植被稀疏、物种多样性较低的干旱地区,植被盖度和生物量的变化对土壤微生物和理化特性有关键性的影响,植被盖度和生物量的增加明显改善了土壤生态功能,但是片面追求植被盖度的增加,对土壤特性改善有限。更多还原

【Abstract】 Soil is an important component of terrestrial ecosysteml,and plays a crucial role in spatial distribution pattern of plant diversity.Soil microorganisms play acentral in decomposing organic matter,in detrmining the release of mineral nutrients,and in nutrient cycling,they affect soil nutrient contents, chemical-physical properties,and consequently,primary productivity.Soil quality restoration and soil management is a key question for vegetation restoration and eco-environment sustainable development for the hilly region of the semiarid Loess Plateau.It has theory and reality significance to study on Vegetation- soil-microorganism change at the semiarid Loess Plateau.In order to provide scientific reference for vegetation restoration and soil care in the Loess Plateau,the change of soil carbon and nitrogen and soil bacterial diversity were studied by designed five gradient levels of plant cover of Reaumuria soongorica at Lanzhou Experiment Base of Environmental Afforestation of South-North Mountains.The results showed:.1.Based on the research of Reaumuria soongorica in study area,using the length of crown diameter and the width of crown diameter as parameters,the fitted equation was set up and tested to estimate the aboveground biomass of Reaumuria soongorica.The fitted equation is given: y=0.7643x-0.0161(R~2=0.8709 P＜0.001),which had a relatively high accuracy and a fine quadratic relationship between the predicted values and measured values.2.Plant cover and aboveground biomass of Reaumuria soongorica increased with plant species diversity nd tended to be the highest with biomass 35.62 g/m2(total cover 48.73%),then species diversity decreased while plant biomass increased,and all plant diversity distribution pattern showed a normal distribution during plant restoration.3.Soil organic carbon(SOC),total nitrogen(TN),soil microbial biomass C (MBC) and microbial biomass N(MBN) gradually increased with vegetation cover.SOC,TN,MBC and MBN increased quickly before the vegetation cover approaching 48.73%.There were similar trend between soil microbial biomass(MBC and MBN) and nutrients(SOC and TN) under the same vegetation cover.4.Aboveground biomass showed a positive relationship with soil microbial biomass C and N(P＜0.05).SOC and N were positively correlated with the vegetation cover,aboveground biomass and soil moisture(P＜0.05).MBC、MBN、TN、MBN/TN showed positive relationship with SOC and TN either(P＜0.05),while MBC was positively associated with MBN(P＜0.05).The positive correlation between MBC and SOC or TN suggested that there were close relationships between soil microbial biomass and nutrients during the vegetation restoration,which also showed that the vegetation restoration improved the soil nutrient status and indirectly affected the soil microbial biomass.5.Soil bacterial diversity increased with vegetation cover,and then gradually remained at a quite constant level,although soil microbial communities structure was different from each other under different vegetation cover.There are no correlation between plant species diversity and soil bacterial diversity.These results imply that in arid and semiarid areas with sparse vegetation and lower plant diversity,the increase of the vegetation cover of Reaumuria soongorica obviously changed the ecological function of the soil.However,the unilateral increase of vegetation cover will have less effect to the soil properties.更多还原