内蒙古大青山国家级自然保护区植被归一化指数时空变化及其与环境因子的关系

Spatio-temporal variation of NDVI and influencing factors in the Daqing Mountain National Nature Reserve,Inner Mongolia

选取2000—2020年MODIS影像的归一化指数(NDVI)数据及同期的气象数据,采用趋势分析、变异系数、相关分析等方法,从海拔、坡度和坡向的角度分析了内蒙古大青山国家级自然保护区生长季NDVI的时空变化特征,并进一步探讨了NDVI时空变化与气候因子的相关性。结果表明:(1)2000—2020年,内蒙古大青山国家级自然保护区植被总体覆盖状况良好且呈增长趋势,增长速率为0.058/10a;(2)保护区NDVI空间分布呈现出西部低、东部高的从西到东逐渐增加的特征。保护区生长季NDVI均值随着海拔的升高而明显增加,随着坡度的增加呈缓慢增加趋势,在不同坡向上,生长季NDVI均值大小依次为阴坡>半阴坡>半阳坡>阳坡;(3)从NDVI变化趋势分析来看,2000—2020年大青山自然保护区植被覆盖改善的面积占总面积的61.75%,其中,显著改善、极显著改善面积分别占总面积的41.13%、20.62%,基本保持不变的面积占总面积的38.17%,退化面积占总面积的0.07%。在空间分布上,NDVI显著、极显著增加的区域主要分布在保护区西部和东部,中部以变化不显著为主。保护区各功能区NDVI变化趋势看,NDVI极显著增加、显著增加面积百分比大小顺序为实验区>核心区>缓冲区;(4)2000—2020年,稳定性整体表现为“不同波动变化并存,较低、中等和较高波动变化居多,低波动和高波动变化面积占比相对较小”的特点,高波动变化区域主要分布在保护区西部、中部和实验区,人为影响和降水量是影响稳定性的主要驱动因素;(5)大青山自然保护区生长季NDVI与年均降水量以正相关为主,正相关面积比例达到99.79%,与温度相关性不显著为主,不显著面积占总面积的97.91%,降水量是影响大青山自然保护区植被覆盖的最主要气象因子。

Based on the Normalized Difference Vegetation Index(NDVI) data of Moderate Resolution Imaging Spectroradiometer(MODIS) image and the relative meteorological data from 2000 to 2020, the temporal and spatial variation characteristics of NDVI in the growing season of Daqing Mountain National Nature Reserve in Inner Mongolia are analyzed from the perspective of elevation, slope and slope aspect by using the methods of trend analysis, coefficient of variation and correlation analysis. The correlation between temporal and spatial variation of NDVI and climate factors was further explored. The results show that:(1) The overall vegetation coverage of Daqing Mountain National Nature Reserve was good and growing from 2000 to 2020, with a growth rate of 0.058/10 a.(2) The spatial distribution of the NDVI shows the characteristics of low in the west and high in the east, and gradually increasing from west to east of the reserve. With the increase of elevation, the mean value of NDVI in the growing season of the reserve increased significantly, but increased slowly with the increase of the slope. In different slope aspects, the mean value of NDVI in growing season was shady slope > semi-shady slope > semi-sunny slope > sunny slope.(3) From the analysis of NDVI change trend in 2000—2020, the area of vegetation coverage improvement in Daqing Mountain National Nature Reserve accounted for 61.75% of the total area, of which the areas of significant improvement and extremely significant improvement accounted for 41.13% and 20.62% of the total area, respectively, the area basically unchanged accounted for 38.17% of the total area, and the degraded area accounted for 0.07% of the total area. In terms of spatial distribution, the areas with the significant and extremely significant increase in NDVI were mainly distributed in the west and east of the reserve, and the change was not significant in the middle. According to the changing trend of NDVI in each functional area of the reserve, the NDVI increased significantly, and the area percentage increased significantly in the order of experimental zone > core zone > buffer zone.(4) From 2000 to 2020, the overall performance of stability is characterized by the coexistence of different fluctuations, the majority of low, medium and high fluctuations, and the proportion of low and high fluctuations being relatively small. The high fluctuations are mainly distributed in the western and central areas of the reserve and the experimental zone, and human disturbance and precipitation are the main driving factors.(5) The average annual maximum NDVI in the growing season of Daqing Mountain National Nature Reserve is mainly positively correlated with the average annual precipitation, and the proportion of the positive correlation area reaches 99.79%. It is mainly insignificant with temperature, and the insignificant area accounts for 97.91% of the total area. Precipitation is the main meteorological factor affecting the vegetation coverage of Daqing Mountain National Nature Reserve.