【作者】 张健；

【导师】 刘国彬； 许明祥；

【作者基本信息】 西北农林科技大学 ， 生态学， 2008， 硕士

【摘要】 植被恢复重建是黄土高原生态建设的首要任务。有关该区植被恢复演替对土壤质量的影响已有大量研究报道,但土壤质量如何影响植被恢复演替尚缺乏足够的研究资料。为此,本论文以陕北黄土丘陵区土壤-植被系统为研究对象,采用空间序列代替时间序列,选取草灌植被过渡阶段的典型植物群落,通过根区取样,野外调查试验和室内分析相结合,系统分析了5种草本群落和7种灌木初期的不同层次土壤物理属性、养分状况和微量元素含量,研究了植被次生演替过程中草灌阶段的土壤条件及关键土壤因子,对于科学认识土壤-植被的互动效应,人工调控加速研究区植被恢复演替进程有重要的科学和实际意义。主要结论如下:1.探讨了黄土丘陵区不同地貌类型下植被自然恢复演替的群落特征,进一步揭示了沟缘线植被的植物篱廊道作用和沟谷地植被的斑块分布格局。封禁约20年后沟谷地植被演替表现出健康演替趋势。灌乔物种已有一定数量和分布,在植物群落多样性和结构等方面有着重要影响。沟谷地植被群落呈斑块格局分布。微域范围上沟谷地地形和土壤的异质性对植物群落形成和演替有重要的影响。不同沟向沟谷地的灌乔植物种的重要值构成上存在一定差异,南北沟向较西东沟向分配均匀。2.明确了植被次生演替草灌阶段土壤物理性质特征。植被次生演替草本群落演替阶段,土壤物理性质得到一定的改善,且表层土壤物理性质的改善效果较好;但土壤物理性质变化与演替时间不呈线性关系变化。随草本群落演替,不同土壤物理因子的变化趋势存在差异;天然草地的土壤物理性质好于人工草地。在植被次生演替灌木初期,除土壤含水量外,土壤容重、孔隙度、稳定入渗和水稳性团聚体均好于白羊草地,表明草本演替阶段对土壤的改善作用为灌木的发育定居提供了土壤物理条件基础。灌木树种不同对定居所需适宜土壤物理条件不同。3.明确了植被次生演替草灌阶段的土壤养分特征。随草本群落演替,土壤养分状况总体上呈改善趋势,不同土壤养分因子剖面变化规律不同,土壤养分状况受群落优势种的控制作用大于演替时间。草本阶段对土壤养分的提高幅度是有一定限度的。灌木初期土壤养分状况总体好于草本阶段,表明灌木初期对土壤养分条件的要求高于草本群落。灌木树种在定居环境的选择和适应性及与对土壤养分因子利用和改造强度上存在着差异。4.明确了植被次生演替草灌阶段土壤有效态微量元素特征。在草本阶段,不同土壤有效态微量元素含量不同,表现为Mn> Fe> Cu> Zn;不同有效态微量元素土层间变化的趋势不同,在0～10与10～20cm土层间,Zn和Mn含量变化存在极显著差异,而Cu和Fe含量变化无显著差异;随草本群落演替,有效锌和锰的含量呈增加趋势,有效铜含量呈波动型变化,有效铁含量呈先增后减。植被次生演替到灌木初期,不同土壤有效态微量元素含量不同,表现为Mn>Cu>Fe>Zn;不同有效态微量元素土层间变化存在一定差异,在0～10与10～20cm土层间,Zn含量变化存在极显著差异,而Cu、Mn和Fe含量变化无显著差异;不同灌木树种对土壤有效态微量元素含量的要求和适宜性存在差异。植被次生演替灌木初期阶段,各土壤有效态微量元素(除有效铜外)与各土壤养分因子和pH值间存在较为显著的线性相关关系。5.明确了植被次生演替草灌阶段的土壤条件,初步识别出草-灌演替阶段的关键土壤因子。在植被次生演替灌木初期,土壤物理因子(土壤含水量除外)和养分因子的最小临界值总体上要高于草本阶段,各土壤养分因子(全磷除外)在灌木初期的变化幅度要明显大于草本阶段。灌木初期土壤有效态锰的最小临界值要高于草本阶段,土壤pH值和有效态微量元素的变化幅度总体上大于草本阶段。从土壤养分累积、土壤物质交换环境和土壤通透性3方面的主成分因子信息可基本反映出草本阶段的土壤条件信息;从营养元素有效性、土壤养分累积、土壤通透性3方面的主成分因子信息可基本反映灌木初期的土壤条件信息。其中,有机质、pH值和孔隙度等因素对草本群落阶段的土壤条件的影响较大,可能是该阶段草本群落演替的关键土壤因子;有效锌、土壤磷元素、容重等因素对灌木初期的土壤条件影响较大,可能是对该阶段灌木树种定居发育产生重要影响的关键土壤因子。更多还原

【Abstract】 Vegetation restoration is the key task of ecological construction in the loess plateau of China. There has been many research and publications about the impact of vegetation restoration on soil quality in this region. However, quite fresh research was done on how soil quality affects on vegetation restoration. In this thesis, taking the soil-vegetation system as the research object, using an approach of spatial sequence instead of temporal sequence, through sampling in the root zone of selected typical vegetation communities in herb and early shrub succession stages, combining with field investigations and laboratory test, we studied soil physical properties, nutrients and trace elements in the soil profile of the five kinds of herbal community and seven kinds of shrub trees. Based on this, suitable soil condition and the key soil factors for the secondary succession from herb to shrub were identified. The research was meaningful for understanding the interactive effects of soil and vegetation, and the results could be a reference for artificial controlling of speed up the process of vegetation restoration succession. Main conclusions are as follows:1. The characteristics of vegetation community restoration in the different types of landforms were clarified in the hilly-gully loess region of China. The corridor function of vegetation fence along the edge of the gully and the patch distribution of vegetation in the gully were demonstrated. With hill closing measurement carried out about 20 years, vegetation succession has expressed a healthy proceeding succession trend with a great abundances and diversity. At present in the side of life forms of plant communities, herbage plants were the major, especially perennial herbage, while shrub and arbor trees also have importance position. Shrub and arbor trees have importance influenced on the diversity and structure of plant communities and so on. Patch pattern of vegetation distribution was prominence in the gullies. Differences were found between the construction pattern of importance values of shrub and arbor trees in different direction gullies. We also found that the South-north gully was more uniform than the west-east gully. There were some differences in the similarity of vegetation species in different gully direction; however, these differences were mainly affected by some coexistence species and ancient species.2. The characteristics of soil physical properties of herb and early shrub stage in vegetation secondary succession were clarified. In the herb stage of vegetation secondary succession, the soil physical properties have been improved, and improvement effect of the physical properties of the soil surface was better than the other soil layers. But there was no linear relationship between the changes of soil physical property and succession time. With the herb community succession, the trend of different soil physical changes. Soil physical properties of natural grassland were better than artificial grassland. With the exception of soil moisture, soil bulk density, porosity, stability, infiltration and water stable aggregates of shrub were better than Bothriochloa ischaemum. It showed that improvement of soil physical properties by herb communities succession provided a basic soil physical conditions for shrub trees ecesis and development. Different shrub trees needed different proper soil physical condition of ecesis.3. The characteristics of the soil nutrient of herb and shrub stage in vegetation secondary succession were clarified. With the herb community succession, soil nutrients showed an improving tendency in general. Different soil nutrient factors in the profile varied differently. It seems that soil nutrient status was controlled by the dominant species of the community rather than successional time. Soil nutrient status of early shrub was better than herb stage. It demonstrated that it needs more restricted nutrient condition in early shrub stage than herb stage. Different shrub trees had different condition on selection and adaptability of ecesis.4.The characteristics of the soil available trace elements of herb and shrub stage in vegetation secondary succession were understood. In the herb stage, contents of different kinds of soil available race elements were different. It showed that Mn> Fe> Cu> Zn. Between 0~10cm and 10~20cm soil layers, changes of contents of Zn and Mn were significantly different, however, no significant difference was found in the contents of Cu and Fe. With the herb community succession, available Zn and Mn contents showed an increasing trend, available Cu content had a waving change, available Fe content appeared the trend from increasing to decreasing. In the early shrub stage, contents of different kinds of soil available race elements were different. It showed that was Mn> Cu> Fe> Zn. Changes trend of different kinds of soil available race elements in the profile were different. Between 0~10cm and 10~20cm soil layers, the change of available Fe content was significant, the change of available Cu, Mn and Fe content were not significant. Different shrub trees were difference in the need and adaptability of the soil available trace elements contents. In the early shrub stage, there was a significant linear relationship between soil available trace elements and soil nutrient, as well as soil pH, but except available Cu. 5. Suitable soil condition and the key soil factors for the secondary succession from herb to shrub were identified. In the early shrub stage of vegetation secondary succession, minimum critical values of soil physicals (except soil moisture) and soil nutrient factors were higher than herb stage in general. The range of the soil nutrient contents (except total phosphorus) in the early shrub was bigger than herb stage. The minimum critical value of soil available Mn in the early shrub was higher than herb stage. The range of the soil pH and the soil available trace elements were in general bigger than herb stage. The three factors of soil nutrient accumulations, environment of soil material exchange and soil permeability, which were identified using principal analysis, could basically reflected soil condition information of the herb stage. Availability of nutrient elements, soil nutrient accumulations and soil perviousness could basically reflected soil condition information of the early shrub stage. Organic matter, pH and porosity had great influence on soil condition of the herb community stage and might be the key soil factors in the herb stage. Available Zn, soil P elements and bulk density had significant influence on soil condition of the early shrub stage, which might be the key soil factors in the early shrub stage.更多还原