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题名: 区域尺度环境因素与植被特征的关系研究 ——以呼伦贝尔草原为例
作者: 刘苗
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 刘国华
关键词: 区域尺度 ; 植被动态 ; 环境因素,regional scale, vegetation dynamics, environmental factors
其他题名: The Relationship of Environmental Factors with Vegetation Characteristics on Regional Scale —— A Case Study in Hulunbuir Grassland
学位专业: 生态学
中文摘要:     作为欧亚大陆草原的重要组成部分,研究环境因子与植被动态之间关系对认识呼伦贝尔草原生态系统运行机制具有十分重要的意义。本文通过样带调查,对不同草地管理方式下生物量、生物多样性以及土壤性质比较研究,同时验证放牧最优化假说,功能平衡假说等,旨在探索可持续草地管理方式。在此基础上通过分类回归树筛选出非生物因子中影响植被特征和生物量的主要因子,利用结构方程模型定量化这些影响作用的大小。基于得到的主要影响因子,利用广义加性模型把这些主要影响因子和植被特征建模,以预测不同管理模式下植被特征随着主要影响因子的未来变化趋势。结合遥感技术手段,分析了40 年来(1973-2013)该区域温度、降水以及干燥度的时空变化格局。利用GIMMS 遥感产品,分析呼伦贝尔1982-2006 年以来的NDVI 时空动态,进而分析对应时间序列气候要素与植被指数之间的关系。利用样带调查和遥感产品分析相结合,以期探索影响呼伦贝尔草地植被动态的主要因子,为草地可持续发展提供理论依据。主要结论如下:
1) 研究了不同草原管理方式下植被特征和土壤性质之间的关系,发现,地上生物量(aboveground biomass, AGB)和地下生物量(Belowground biomass,BGB)在放牧方式下低于围封和刈割,但是根冠比(Root/shoot, R/S)结果相反;不放牧对AGB 和BGB 有明显提高作用,与生物多样性及土壤养分一样,刈割和围封是有效的草地保护措施。
2) 通过分类回归树(Classification And Regression Tree, CART)分析,发现与AGB 关系较密切的因子有经度、纬度、土壤有机碳(Total organic carbion, TOC)和土壤含水量(Soil water content, SWC);影响BGB 的主要因子有TOC、总磷(Total phosphorus, TP)、速效磷(Available phosphorus, AP)和容重(Bulk density,BD);影响R/S 的主要因子有纬度、总氮(Total nitrogen, TN)、BD、TOC 和AP。影响AGB 最大的是经度,总效应是0.633;影响BGB 最大的是土壤总有机碳,总效应是0.532,其次是土壤容重;影响R/S 最大的是经度,总效应是-0.872。根据结构方程模型(Structural equation modeling,SEM)得出的结论,经纬度对生物量的影响比较大,即水热对生物量具有较大的影响,因此接下来分析温度、降水与生物量的关系。发现,随着温度升高,AGB 和BGB 都是降低的,而随着降水的增加,AGB 和BGB 都是升高的。讨论水热对土壤养分的影响,发现,随着降水增加,土壤TOC 和TN 是增加的,而随着温度的升高,土壤TOC 和TN 是降低的。
3)通过广义加性模型(Generalized additive models,GAM)预测AGB,BGB,凋落物和盖度随着典型变量的变化趋势,发现AGB 随着降雨的增加而增加,BGB呈现相反趋势,BGB 随着TOC 总体上呈现增加趋势;BGB,凋落物和盖度随着AP 的增加而增加,符合功能平衡假说。
4) 1973-2013 年,时间序列上呼伦贝尔区域年降雨量变化不明显,而年均温度趋势上升明显(P<0.05),就干燥度而言,呈现下降趋势,但是趋势也不显著。
5) 1982-2006 年,时间序列上,距平分析表明呼伦贝尔区域NDVI 均值呈显著下降趋势(P<0.01),且森林,草甸和湿地均呈现显著下降趋势,而草原变化不明显,这可能与采取的有效的草地管理措施有关。空间上,植被指数变幅表明中东部呈下降趋势,而西部植被向好趋势明显,1982-2006 以来最大变幅达到96.73%。
英文摘要:     The study on the relationship of environmental factors with vegetation dynamic is significant to understand the mechanism of Hulunbuir steppe, which is an important part of Eurasia Steppe. Plant biomass, diversity and soil property under different grassland management practices was contrasted via transect survey. Meantime, the gazing optimization hypothesis and function equilibrium hypothesis was also tested. It was aimed at exploring a sustainable grassland management type. And then, some main abiotic factors affecting vegetation characters and biomass was screened out via classification and regression tree (CART) model, the structural equation modeling (SEM) was conducted to explicitly evaluate the both direct and indirect effect of these critical environmental elements on vegetation biomass. Next, the model was established between those elements and vegetation characters via generalized additive model (GAM), aiming to explore the future tendency of vegetation dynamics with main environmental factors under different grassland managements. Moreover, to combined with remote sensing technique, the temperature, precipitation and aridity from 1973 to 2013 in study region was analyzed. The spatial and temporal of normalized Difference Vegetation Index (NDVI) from 1982 to 2006 in Hulunbuir was studied via GIMMS/NDVI data set, and also, the relationship of meteorological factors with corresponding NDVI was explored. Transect survey and remote sensing as united in order to explore the main elements influencing vegetation dynamic in Hulunbuir grassland, and provide theoretical foundation for sustainable development of grassland. The main results were as followings:
1 ) Both aboveground biomass (AGB) and Belowground biomass (BGB) were lower on the grazing regime than on fencing and mowing, but the root-to-shoot ratio was higher than other utilization patterns; We concluded that the significant effect of grazing exclusion on the increment of AGB and BGB, as well as species diversity and soil nutrients, could be promoted via mowing and fencing.
2)AGB was closely related to longitude, latitude, total organic carbon (TOC) and soil water content, (SWC). BGB was related to TOC, total phosphorus (TP), available phosphorus (AP) and bulk density (BD). R/S was mainly affected by latitude, total nitrogen (TN), BD, TOC, AP. Longitude affected AGB (direct effect) scored at 0.633 (P<0.05). The total effect of TOC on BGB was 0.532, while that of longitude on R/S was -0.872. The results were determined by structural equation modeling (SEM). Our results indicate that AGB and BGB in semi-arid ecosystems are strongly affected by precipitation and temperature. Thus, the relationship of precipitation and temperature with biomass was analyzed next. We found that, AGB and BGB was decreasing with the increasing temperature, whereas, precipitation and temperature was increasing with the increasing. In addition, TOC and TN was increasing with the increasing precipitation and decreasing temperature.
3)There are complex trends with regards to vegetation characteristics and critical environmental factors. Our results indicated the change of AGB, BGB, litter and coverage with typical variables via generalized additive models (GAM). That is, AGB was increasing with increasing precipitation, while BGB is opposite. BGB was increased with TOC in the whole. BGB, litter and coverage was increased with the increased AP, which was according with function equilibrium hypothesis.
4)From 1973 to 2013, there was not large variation of annual precipitation and marked change of annual mean temperature in the study area. As for aridity, there was a decline and insignificant trend, but this trend was not obvious.
5)From 1982 to 2006, there was a decreased and significant tendency of NDVI (Mean value) in the study area (P<0.01), as well as forest, meadow and wetland vegetation types with an exception of steppe. It could be related to the grassland management practices. Spatially, NDVI was showed a down trend in mid-eastern zone and an obviously positive trend in western area. The maximum amplitude of NDVI was up to 96.73%.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34348
Appears in Collections:城市与区域生态国家重点实验室_学位论文

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Recommended Citation:
刘苗. 区域尺度环境因素与植被特征的关系研究 ——以呼伦贝尔草原为例[D]. 北京. 中国科学院研究生院. 2015.
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