武陵山区植被生长季NDVI时空变化及其对气候变化的响应

Spatiotemporal Variation of NDVI in the Vegetation Growing Season of Wuling Mountainous Area and Its Response to Climate Change During 2000-2019

为了厘清武陵山区植被覆盖变化及其对气候变化响应的特征,基于MODIS NDVI和同期气象数据,采用变异系数、Sen趋势检验和Hurst指数等方法分析了该区2000—2019年植被生长季NDVI的时空变化特征,揭示了不同时空尺度NDVI对水热因子的响应特征。结果表明:(1)近20年武陵山区植被生长季NDVI呈现波动增加态势,植被条件不断改善;武陵山区植被覆盖较好,生长季NDVI的空间格局总体表现为"东北高、东南和西部低",空间变化整体处于较稳定状态,垂直变化特征为随海拔升高先增后减;NDVI变化趋势多为不显著增加,增速仅0.004/a,而退化区域主要集中在2 000 m以下;变化整体趋向反持续性,未来变化特征主要表现为下降。(2)生长季尺度,武陵山区气候趋向暖湿,NDVI与气温、降水均整体表现为正相关,且受降水影响更大;月尺度,NDVI整体上对气温的响应未见明显滞后性,而对降水以滞后一个月为主,0—2月滞后期主控气候因子依次是降水、气温和气温。研究结果能够为气候变化背景下该区的植被保护提供一定参考。

In order to clarify the spatiotemporal variation characteristics of vegetation covers in the Wuling Mountainous Area and their responses to climate change, based on the MODIS NDVI and the meteorological data of the same period, the coefficient of variation, Sen trend test, and Hurst index were used to analyze the spatiotemporal variation of NDVI during vegetation growing season from 2000 to 2019 in the Wuling Mountainous Area. Meanwhile, the response characteristics of NDVI to different scales of hydrothermal factors were revealed. The results show that:(1) as for the temporal pattern of the recent 20 years, vegetation conditions had shown the trend of increasing fluctuation and continuously improving;the vegetation coverage in the Wuling Mountainous Area was good, and its spatial pattern could be summarized as ‘high in the northeast, low in the southeast and west’;the spatial variation was in a relatively stable state, and its value increased first and then decreased with the elevation;the variation trend of NDVI was mostly insignificant with the annual growth rate of only 0.004, while the degradation area mainly concentrated below the altitude of 2 000 m;the overall spatial change tended to be anti-persistent, and the main characteristics of future change are decline;(2) during the vegetation growing season of the research period, the climate in the Wuling Mountainous Area was getting warmer and wetter;NDVI was positively correlated with temperature and precipitation as a whole, but it was more affected by the latter;on the monthly scale, the overall response of NDVI to temperature showed no obvious hysteresis, while the response to precipitation was mainly manifested as a lag of one month;in the lag period from 0 to 2 months, the main controlling climate factors were precipitation, temperature, and temperature in turn. The results can provide some reference for vegetation protection in this area under the background of climate change.