Dynamic simulation of functional connectivity and identification of conservation priorities for grassland in China’s Poyang Lake considering ecological processes

Abstract

Analysing dynamics of landscape functional connectivity and evaluating conservation priority of habitat patches are of great significance for biodiversity conservation. Taking the grassland of Poyang Lake as a case, and comprehensively considering the ecological processes of water level change and species dispersal, this study firstly identified the range and patch composition of grassland under different water levels. Then, the graph theoretical approach was applied to analyse the dynamics of functional connectivity of grassland with different water levels and dispersal distances. Finally, the delta value for probability of connectivity (dPC) and betweenness connectivity (BC) were respectively used to identify the most important grassland patches and key grassland nodes. The results showed as follows: (1) The grassland presented the characteristics of “expanding when water falls while shrinking when water rises”. The grassland patches faced both the segmentation effect and the inundation effect of water. With the increase of water level, the distribution of grassland was gradually shrinking, the distribution of grassland decreased from 1813.61 km2 at the water level of 7.54 m to 182.36 km2 at the water level of 17.17 m, and the fragmentation of large patches and the disappearance of small patches coexisted. (2) From the perspective of water level change, the functional connectivity of grassland has progressively decreased with the increase of water level. From the perspective of species dispersal, the species dispersal distance had an absolutely positive impact on landscape functional connectivity. With the increase of dispersal distance, the functional connectivity of grassland increased dramatically. (3) The 124 important grassland patches were identified and mapped. They were all larger ones in area and primarily distributed in the center of Poyang Lake, especially concentrated in the two national nature reserves. The 16 key grassland nodes were determined and mapped. They were very small in size and mainly scattered in the central and southern margin of Poyang Lake. Giant patches and large patches play an extremely vital role in maintaining the grassland connectivity. However, small patches in pivotal locations can not be ignored as stepping stones or connecting elements. Our study provides a scientific reference for the protection and management of natural habitats in lake areas.