Dynamic Changes of Plantations and Natural Forests in the Middle Reaches of the Yangtze River and Their Relationship with Climatic Factors

Abstract

Based on Landsat TM/ETM/OLI images and MODIS NDVI time series remote sensing data from 1999 to 2015, the changes of land use/cover types (including natural forests and plantations) through NDVI trends and their relationship with meteorological factors in the middle reaches of the Yangtze River (MRYR) were analyzed by supervised classification, coefficient of variation, trend analysis, rescaled range analysis, and partial correlation analysis. The results showed that, in the past 17 years, the main landscape type in the MRYR is forestland (accounting for more than 50%), and the built-up land and plantations area increased by four fifths and one fifth, respectively. The area of natural forests had been reduced by one fifth. Additionally, NDVI showed an upward trend (0.37%), especially in natural forests (0.57%). Two thirds of the natural forests had NDVI values greater than 0.80, and 89.21% of them were significantly improved. The area with an uncertain future development trend of all vegetation was more than half of the area. At the same time, partial correlation analysis with climate factors showed that relative humidity had an inhibitory effect on vegetation growth (p < 0.05). Climate factors had a certain lag effect on the growth of natural forests and plantations. Generally speaking, sunshine duration had a positive effect on forests growth, while relative humidity had a negative effect. The results showed that if the forest land was studied as a whole, many of the problems of natural forests and plantations would be ignored. The continuous decrease of natural forests and possible further degradation in the future are worthy of attention. The results could provide a reference for forest ecological protection in other areas.