New assessment indicator of habitat suitability for migratory bird in wetland based on hydrodynamic model and vegetation growth threshold

Migratory birds are indicator organisms for the health of wetland ecosystems. Choosing the key environmental indicators is vital to the assessment of habitat suitability for migratory birds. In the study, hydroperiod was used to predict wetland suitability for migratory birds. It control growth of vegetation used for migratory birds' food and could predicted by hydrodynamic model. This study presents a new indicator for assessing migratory bird habitat suitability in wetland, continuous flooding time (CFT), based on two-dimensional (2D) hydrodynamic model and vegetation growth threshold. In Poyang Lake wetland (the largest migratory bird wintering based in Asia), variation in CFT amongst different hydrological years (wet, dry and normal flow years) was calculated by using the 2D hydrodynamic model based on incompressible Reynolds Average Navier-Stokes (N-S) equation. The habitat suitability for migratory birds were calculated based on the vegetation growth threshold (CFT) of Carex spp., Phalaris arundinacea and Polygonum criopolitanum in the typical (hydrological) years. Results show that migratory birds have the largest suitable area (with High and Very High suitability) in 2009 (normal flow year). The suitable area in severe drought (flood) year is significantly less than the area in normal dry (wet)year. The average of the suitable CFTs (with High and Very High suitability) are almost equal in 2007 (dry year) and 2002 (wet year). The suitable CFT is between 120 and 240 days, and the average of the suitable CFT is 170.39, 190.26 and 173.49 days in 2007 (dry year), 2009 (normal flow year) and 2002 (wet year), respectively. Overall, the study provides a valuable evaluation indicator of habitat suitability for migratory bird, however the use of the indicator must depend on a certain study of the vegetation growth threshold and the feeding habit of migratory birds for the study area. The proposed indicator can further improve the comprehensive evaluation system for wetland migratory birds and provide a scientific reference of the water environment planning and ecological management for the scheduled Poyang lake dam.