黄土高原植被覆盖与土壤湿度的时滞关联及时空特征分析
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宝鸡文理学院,宝鸡文理学院

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宝鸡文理学院校级重点项目(ZK16064);陕西省社会科学基金项目(2016G013)


Analysis of temporal and spatial characteristics of time lag correlation between the vegetation cover and soil moisture in the Loess Plateau
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Baoji University of Arts and Sciences,

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    摘要:

    基于2000-2014年的MODIS-NDVI与MODIS-LST数据,利用温度植被干旱指数对黄土高原土壤湿度进行了反演,采用时滞互相关法分析了土壤湿度与植被覆盖的年内变化特征及其时空相互关系。结果如下:(1)黄土高原植被生长对土壤湿度变化存在明显的时滞效应,植被生长以及植被物候与土壤湿度变化密切相关。(2)黄土高原土壤湿度对其植被覆盖变化影响强烈区,主要分布在农业与草原生态区北部的丘陵沟壑区,植被生长对土壤湿度响应迟缓;而植被覆盖对土壤湿度变化影响强烈区,分布于西部的高寒地带,响应时间相对最短,其次为农业与草原生态区内河流中上游流域,且土壤湿度对植被覆盖的响应较快,自东向西、自北向南响应逐渐加快。(3)从植被类型来看,Ⅰ类植被的植被覆盖与土壤湿度负相关性较强,植被生长对土壤湿度变化的响应程度依次减弱,响应速度较慢且依次加快。Ⅱ类植被的植被覆盖与土壤湿度的相关性很弱,滞后时间接近于0天,反映出植被覆盖与土壤湿度同步变化。土壤湿度变化滞后于Ⅲ类植被(旱生/沙生植被)的植被覆盖变化,植被覆盖正向影响土壤湿度变化的强度依次增加,但时间效应依次延长。Ⅳ类植被(高山/高寒植被)生长对土壤湿度变化的正向影响程度最强,而且响应速度较快。(4)黄土高原植被生长与土壤水分的年内变化具有密切的关系,土壤水分年内变化的峰值和谷值与植被物候期非常吻合,因此土壤水分的年内变化可作为植被物候特征提取的一种重要依据。

    Abstract:

    Based on the MODIS-NDVI and MODIS-LST data from 2001 to 2014, we have estimated the soil moisture using temperature vegetation dryness index, analyzed the spatiotemporal seasonal variation of the vegetation cover and soil moisture and their interrelationship in the Loess Plateau. The findings suggest the following:(1) There are obvious time-lag effect for vegetation growth relative to soil moisture in the Loess Plateau. The vegetation cover and vegetation phenology is closely related to soil moisture change. (2) The intense affected area of soil moisture to vegetation cover located mainly in the mountains and hills of the northern agriculture and grassland biome, which the vegetation cover has slow response. The intense affected area of vegetation cover to soil moisture spread over the western alpine region, which the response time of soil moisture is relatively shortest. The second one distributes across the upper and middle reaches of the rivers in the northern agriculture and grassland biome, and the soil moisture respond slowly. The response speed gradually increase from east to west and from north to south. (3) From vegetation types, there are relatively strong negative correlations between vegetation cover and soil moisture of vegetation Ⅰthat the response degree of vegetation growth to soil moisture change weakens successively, and their response rate is relatively slow and speed up. A weak correlations were found between vegetation cover and soil moisture of vegetation Ⅱ, and their lag time are close to 0 day, which reflects vegetation cover and soil moisture change simultaneously. The soil moisture changes lag behind vegetation cover change of vegetation Ⅲ (xerophytic/psammophytic vegetation), and the degree that vegetation cover positive impacts on soil moisture increase consequently, but time effects extend. The positive impact of alpine vegetation (vegetation Ⅳ) to soil moisture is strong which has better response speed. (4) There is close relationship between the annual variance of vegetation growth and soil moisture in the Loess Plateau. The vegetation phenology is a good fit to the peak and valley of soil moisture changes over the years which can be used as an important evidence for the extraction of vegetation phenological information.

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张翀,雷田旺,宋佃星.黄土高原植被覆盖与土壤湿度的时滞关联及时空特征分析.生态学报,2018,38(6):2128~2138

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