Identifying the drivers of vegetation changes in Inner Mongolia based on residual analysis and Hasse diagram technique

Exploring the effect of climate change and human activities on vegetation is a key requisite for the reconstruction of regional ecological environments. Therefore, based on long-term vegetation GIMMS NDVI data, climate data, and statistical data, the present study applied the Hasse diagram technique and combined the multivariate regression residual analysis to quantitatively analyze the impact of human activities and climate change on vegetation in Inner Mongolia from detail human activities with some innovations. The results showed that (1) NDVI showed an overall increasing trend over the last 39 years, with an abrupt change in 2000; moreover, vegetation growth was better before the abrupt change (PⅠ: 1982–2000) than after it (PⅡ: 2001–2020), with significant downward trends in Xilin Gol and Hulunbuir. (2) Human activities can promote as well as inhibit vegetation, and the promotion effect was larger during 1982–2000 than during 2001–2020, whereas the inhibition effect was larger during 2001–2020. In addition, during PI, vegetation in Inner Mongolia generally experienced promotion by human activities and climate change, while during PII, climate-driven promotion had the strongest effect, followed by human-driven inhibition mainly distributed in Xilin Gol. (3) The result of the Hasse diagram analysis showed that the dominant pathways of human activities affecting most of the cities were economic factors and urbanization during PⅠ and economization during PII.

探究气候变化与人类活动对植被的影响，是区域生态环境重建的关键前提。据此，本研究基于长期GIMMS NDVI（归一化差分植被指数，Normalized Difference Vegetation Index）数据、气象数据与统计数据，采用哈斯图（Hasse diagram）技术并结合多元回归残差分析，从细化人类活动分类的视角开展定量研究，剖析二者对内蒙古地区植被的影响，且研究具备一定创新之处。

研究结果显示：
（1）近39年来，NDVI整体呈上升趋势，并于2000年发生突变；突变前（时段PⅠ：1982–2000年）的植被生长状况优于突变后（时段PⅡ：2001–2020年），其中锡林郭勒盟与呼伦贝尔市的NDVI呈显著下降趋势。
（2）人类活动对植被兼具促进与抑制双重作用：1982–2000年的促进效应强于2001–2020年，而2001–2020年的抑制效应则更为显著。此外，在时段PⅠ内，内蒙古地区植被整体受人类活动与气候变化的共同促进；在时段PⅡ内，气候驱动的促进作用最强，其次是以锡林郭勒盟为主要分布区的人类活动驱动的抑制作用。
（3）哈斯图分析结果表明：在时段PⅠ内，影响多数盟市的人类活动主导路径为经济因素与城市化进程；在时段PⅡ内，则为经济集约化（economization）。