东北地区植被时空演变及影响因素分析

基于2000~2020年MODIS NDVI遥感数据,辅以气象数据和土地利用数据,通过小波分析、Sen+Mann-Kendall趋势分析、Hurst指数、偏相关分析及残差分析法,以不同地形地貌为单元,对不同周期阶段下东北地区植被时空演变特征及其对气候变化和人类活动的响应机制进行深入解析.结果表明:时间上,21a间东北地区植被NDVI呈速率为0.0308/10a(P<0.001)的上升趋势,以16a第一主周期下10a左右的周期变化最为稳定;空间上,东北地区植被NDVI整体处于较高水平,但空间分异明显,呈“西南低东北高”的格局.各周期阶段均为NDVI改善面积大于退化面积且改善范围不断扩增.NDVI未来变化趋势主旋律为持续改善,占总面积的63.56%;响应机制上,东北地区植被NDVI受气候变化与人类活动共同影响.2000~2020年NDVI与气温、降水和相对湿度呈正相关,与日照时数呈负相关,其中降水对NDVI的影响作用最强,且随周期演替以降水为主导气候因子的面积显著递增.各周期阶段人类活动对NDVI变化均以正向促进为主,林业工程实施是植被状况改善的关键,而建设用地扩张是植被减少的主要原因.

Spatiotemporal evolution and influencing factors of vegetation in Northeast China

Based on MODIS NDVI remote sensing data from 2000 to 2020, supplemented with meteorological data and land use data, the spatiotemporal evolution characteristics of vegetation and its response mechanism to climate change and human activities of each topographic unit in different cycle phases in Northeast China were investigated in-depth, using the methods of wavelet analysis, Sen+Mann-Kendall trend analysis, Hurst index, partial correlation analysis and residual analysis. The results showed that: Temporally, the vegetation NDVI in Northeast China showed an increasing trend with a rate of 0.0308/10a (P<0.001), and the most stable cycle change was about 10a under the first main cycle of 16a. Spatially, the vegetation NDVI in Northeast China was at a high level overall, but the spatial differentiation was obvious, with a pattern of "low in the southwest and high in the northeast". The NDVI improvement area was larger than the degradation area in each cycle phase and the improvement area was expanding. The main theme of NDVI future trend is continuous improvement, accounting for 63.56% of the total area. In terms of response mechanism, the vegetation NDVI in Northeast China was influenced by both climate change and human activities. NDVI was positively correlated with temperature, precipitation and relative humidity, while negatively correlated with sunshine hours from 2000 to 2020, among which precipitation had the strongest influence on NDVI, and the area with precipitation as the dominant climate factor increased significantly with the cycle succession. Human activities mainly positive contribute the variation of NDVI, the implementation of forestry projects was the key to the improvement of vegetation condition, while the expansion of land for construction was the main cause of vegetation reduction.