近20 a云南文山州植被覆盖动态变化及其驱动因素

Dynamic change of vegetation cover and its driving factors in Wenshan of Yunnan over the past 20 years

地表植被覆盖对于土壤侵蚀的抑制作用广为人知。许多研究证实在降水、土壤、地形等环境因素一定的情况下,植被覆盖度与水土流失量具有显著的负相关关系。分析研究山区植被覆盖动态变化及其驱动因素对区域水土保持、水土流失治理成效评价及国土空间规划等意义重大。笔者利用MOD13Q1数据,采用像元二分、一元线性回归方程、变异系数、叠加分析等方法,系统地分析2001-2020年间云南省文山州植被覆盖时空演变特征及其驱动因素。结果表明:1)研究区近20 a年均植被覆盖度呈逐年波动上升趋势,且植被覆盖度>80%的极高植被覆盖度区域面积明显增加;2)植被覆盖度改善和显著改善区面积(84.51%)明显大于退化和显著退化区面积(6.47%);约80.98%的区域植被覆盖度变化较为稳定,仅0.50%的区域变异性较强且分布零散;文山州71.14%的区域平均Hurst指数<0.5,未来一段时间内植被覆盖会有一定程度的减少;3)通过叠加分析可知,耕地、林地和人造地表面积的转化率分别为38.14%、35.01%和27.67%,是引起植被覆盖度变化的最重要因素。总体而言,文山州植被覆盖状况较好,过去20 a生态文明建设取得了显著成效。

[Background]Vegetation is the most active factor in the natural ecosystem and the inhibitory effect of surface vegetation cover on soil erosion has been well known.Existing studies have shown that under certain other conditions(precipitation,soil and topography),vegetation coverage has a significant negative correlation with soil erosion.Therefore,analyzing the dynamic changes of vegetation cover and its driving factors is critical to regional soil and water conservation,governance effectiveness evaluation and land space planning in mountainous areas.[Methods]Based on MOD13Q1 data,this paper systematically analyzed the temporal and spatial evolution characteristics of vegetation coverage in Wenshan from 2001 to 2020 using methods such as pixel dichotomy,one-dimensional linear regression equation,coefficient of variation,Hurst index and statistical methods.Spatial analysis was also employed by overlaying vegetation cover change information with land use during the past two decades to reveal the driving forces behind.[Results]1)In the past 20 years,the annual vegetation coverage in the study area showed an upward trend of fluctuation,areas of extremely high vegetation coverage with FVC over 80%increased dramatically,ranging from 3997.22 km 2 in 2001 to 15313.78 km 2 in 2020.2)Areas with improved and significantly improved vegetation coverage(84.51%)were more dominant than those areas of degraded and significantly degraded vegetation coverage(6.47%).About 80.98%of the total area was characterized by a stable vegetation coverage change,only 0.50%of the area showed a strong variability in vegetation coverage change,with a scattering distribution.However,the average Hurst index for 71.14%of Wenshan was<0.5,which indicated that there will be a certain degree of reverse decline for the future vegetation coverage change.3)Based on overlay analysis,the dynamic change ratios of cultivated land,forest land and artificial surface were 38.14%,35.01%and 27.67%,respectively,which were the major factors responsible for the vegetation coverage change.[Conclusions]The method mentioned in this study provides a reliable estimation,due to the consideration of time series images and multi-perspective analysis,which are potentially transferable to other mountainous areas as a robust approach for rapid assessment of vegetation coverage,as well as soil erosion control efforts.Overall,the status of vegetation coverage,the ecological environment has been continuously improved during the past 20 years,as well as the construction of ecological civilization.