For me there is a basic flaw with this introduction. The objectives are not clear and the introduction does not prepared the reader for this. Your objectives are
(1) to measure the species composition of the plant community of Xiejiadian landslide through field investigation
(2) to evaluate how the occurring plant species associated with each other during the natural recovery by calculating the Schluter’s variance ratio (VR), x2 test, Association coefficient (AC), Ochiai index (OI) and Pearson’s and Spearman’s correlation coefficients