Effects of forest type and urbanization on species composition and diversity of urban forest in Changchun, Northeast China

Urban forest is considered as the most important component of urban green infrastructure and can make vital contributions to urban biodiversity. Understanding the species composition and diversity of urban forest is important for urban biodiversity enrichment. In this study, we evaluated the urban forest woody plant diversity and spatial pattern in Changchun, northeast China. The differentiations in species composition and diversity among types of urban forests and gradients of urbanization were then explored. Principal Component Analysis (PCA) was performed to characterize the species distribution. Similarity Percentage (SIMPER) analysis was adopted to determine the species differentiation and the main contributed species among different urban forest types and different urbanization gradients. The results showed that urban forest species in Changchun were abundant with 88 species that belonged to 50 genera and 24 families. The three major species were Salix matsudana, Populus davidiana, and Pinus sylvestris var. mongolica. Native species were preferred in urban forest of Changchun. Significant differentiations in species composition were observed among different types of urban forests. Attached forest (AF) had the highest species richness and biodiversity, whereas production and management forest (PF) had the lowest ones. SIMPER results showed the highest species dissimilarity between AF and PF and lowest species dissimilarity between AF and landscape and relaxation forest (LF). For different urbanization gradients, species richness and diversity in the third ring were the highest and in the first ring were the lowest. SIMPER results showed the lowest species dissimilarity between the third ring and the fourth ring and highest species dissimilarity between the first ring and the fourth ring. Based on the 10/20/30 "rule of thumb", the diversity must be urgently increased at the species, genus, and family levels for EF and PF. For different urbanization gradients, diversity should be increased at the species level in the first ring and the fifth ring, and should be increased at the family level in the second ring and the fifth ring