Abstract:

Sites with spontaneous vegetation are important for studying the mutual feedback mechanisms between urbanization and urban ecosystems. The study of the relationship between species diversity and functional diversity of spontaneous vegetation and their response to urbanization can be predictive of the distribution patterns of species and can aid elucidation of mechanisms of ecosystem function. In this study， the spontaneous vegetation community in Lanzhou riverside parks was chosen for study， and the distribution patterns of species were recorded to clarify vegetation response mechanisms to urbanization. This was achieved by analyzing spontaneous vegetation species composition and functional characteristics， and the differences between species diversity and functional diversity of the spontaneous vegetation community under different urbanization levels and for different habitat types， and by probing the relationship between species diversity and functional diversity and their responses to urbanization. It was found that there were 142 spontaneously occurring plant species among the vegetation in the Lanzhou riverside parks， belonging to 42 families and 116 genera， and dominated by herbaceous plants. On life-history type， perennial herbaceous plants （38%） and annual herbaceous plants （30%） were dominant. The flora was 54.2% native， with a noticeable spread of invasive plants （14.1%）. Overall， species with herbaceous foliage （61.87%） and papery foliage （26.06%）， species with small- （24.65%） and medium-sized leaves （59.15%）， insect vectors （73.24%）， and wind dispersal （59.15%） had the greatest contribution to functional traits. Urbanization had a significant impact on spontaneous vegetation in park green spaces， with significant expansion of annuals in high disturbance environments and habitat fragmentation promoting invasion of short-life-cycle， high dispersal species. Spontaneous vegetation’s species and functional diversity differed significantly （P<0.05） among urbanization levels and habitat types. Functional richness （FRic）， differed significantly （P<0.05） between scrub and hard-substrate habitat， and between woodland and scrub； and Patrick index， between woodlands and scrub （P<0.05）. Across different urbanization levels， spontaneous vegetation had the highest Patrick index and the lowest FRic at medium urbanization level， and the prevailing abiotic conditions filtered species possessing traits that can adapt to the local environment， thereby causing the functional traits of community members to converge. High urbanization level caused community homogenization. Patrick index showed a significant positive correlation （P<0.05） with functional richness and Rao’s quadratic entropy value （RaoQ）， which is in line with theory of ecological niche complementarity. There was a highly significant positive correlation （P<0.01） between species diversity and functional diversity in most of the different urbanization levels， and a linear relationship between Shannon-Wiener index and RaoQ was more evident at high urbanization levels. This study reveals the response patterns of spontaneous vegetation to urbanization in Lanzhou riverside parks， and provides scientific data for managing the ecological protection and sustainable development of urban riverside green space.

Key words: urbanization, spontaneous vegetation, species diversity, functional diversity, the riverside parks, Lanzhou City