Spatio-temporal patterns of tree diversity and distribution in urban resettlement areas for displaced farmers

Abstract

Resettlement residential areas (RRAs) are a unique product of China’s urbanisation process. Their greening environment is critical to the quality of life and liveable green neighbourhood of the displaced farmers. Our study aimed to (1) interpret the species composition of the landscape trees and their contributions to urban biodiversity in RRAs, and (2) elucidate the structural changes in the tree composition in the last 20 years. Twenty selected RRAs in Changzhou, Jiangsu Province, China, were divided into three categories by completion year. We assessed tree species composition, floristic diversity, tree dimensions, importance value, RRA characteristics, and greening management. The sampled sites accommodated 741 stems and 52 species belonging to 25 families. The three most abundant species were Cinnamomum camphora, Osmanthus fragrans, and Magnolia grandiflora, constituting 45.75% of all trees. The importance values revealed a changing tree planting pattern over time, with persistent domination by a few species. The oldest sites did not harbour the largest trees due to long-term mismanagement and mistreatment by residents. Compared with other housing types and cities, the tree count, importance value, and diversity in RRAs were low. The species diversity was not correlated with RRA completion time, distance from the city centre, and RRA area. The trees were in poor shape with limited trunk diameter and tree height and suffered from frequent and drastic pruning. Residents with lingering farmer mentality commonly exploited the vegetation and green spaces indiscriminately as natural resources. The greenery management could be overhauled by increasing tree number, native species, species diversity, and tree-care quality and engaging residents in a collaborative and participatory mode for a joint maintenance endeavour. The findings offer a scientific basis to improve or design RRA green spaces.