典型干旱区甘肃民勤光合/非光合植被覆盖度时空演变分析

The Spatio-temporal Evolution Analysis of Photosynthetic/Non-photosynthetic Vegetation Coverage in Minqin Gansu Typical Arid Area

光合植被(Photosynthetic Vegetation, PV)和非光合植被(Non-Photosyntletic Vegetation, NPV)是用于描述干旱区植物生存状态和监测植物生产力的重要因子,及时监测PV/NPV的覆盖度是研究植被衰退驱动机制的必要条件。鉴于此,以中国西部甘肃省民勤县荒漠过渡带为研究区,采用线性光谱混合模型,通过Google Earth Engine地理云计算平台上Landsat系列的年NDVI(归一化植被指数Normalized Difference Vegetation Index)最大合成影像数据生成一套1987年—2017年的PV与NPV覆盖度产品(1期/年)。通过数据分析发现近30 a间民勤的PV和NPV覆盖度均明显增加,2007年—2008年是PV大量向NPV转化的时间节点;PV覆盖度增加主要是在石羊河两侧耕地范围内及其南部腾格里沙漠区域,而NPV覆盖度增加分布于绿洲外的整个民勤境内的荒漠区域,此结论可作为研究区PV与NPV覆盖度变化及其发生的根源分析的依据。

Photosynthetic vegetation(PV) and non-photosynthetic vegetation(NPV) are the important factors for describing plant survival and monitoring plant productivity in arid area.And timely monitoring of photosynthesis/non-photosynthesis desert vegetation coverage(fPV and fNPV) is a necessary condition to research on the mechanism driving vegetation recession.In view of this, this paper takes the Minqin desert transition zone in western Gansu Province of China as the study area, adopts the linear spectral mixture modelby Google Earth Engine geographic cloud computing platform to produce a set of fPV and fNPVwith 30 m resolution generated(once every one year) by annual NDVI maximum composite Landsat series images from 1987 to 2017 in Minqin, Gansu province.Through the analysis of long-time series fPV and fNPVmaps, it was found that: The PV and NPV fractional coverageis increasing significantly during the past 30 years, and the period 2007—2008 was the time node of PV conversion to NPV.The spatial distribution of the PV fractional coverage increasedis mainly near the water source in the core area of Shiyang river and its southern area, while the areaof NPV fractional coverage increased is distributed in the desert area of Minqin county outside the cultivated area.This conclusion provide the theoretical basis for the analysis of the causes and root causes of PV and NPV coverage changes in the study area.