Mechanism of Waterbird Diversity Succession and Its Contribution to Nutrient Loads in Chagan Lake, China

Analyzing the spatiotemporal variation of waterbird diversity is important for wetland restoration and protection. However, further research is needed to investigate the mutual feedback between the mechanisms of waterbird diversity and water quality. Thus, we analyzed the waterbird diversity variations and their driving mechanisms in Chagan Lake from 2013 to 2022 based on piecewise structural equation modeling (SEM) and generalized additive model (GAM). The survey identified 197 waterbird species, 35 of which were endangered. The Anseriformes proportion has exceeded 50% over that period. Although the number and diversity of waterbird in the reserve have increased, they were also threatened by non-ecological land (NEL) development and water quality deterioration. The NEL/EL, total nitrogen (TN), and total phosphorus (TP) significantly reduced waterbird diversity with coefficients of -0.66 (<i>p</i> < 0.001), -0.55 (<i>p</i> < 0.001), and -0.49 (<i>p</i> < 0.05), respectively. TN and TP loads of waterbird were 356,601 and 102,941 kg in 2022, respectively. Anseriformes and Gruiformes contributed the most total nitrogen and total phosphorus. The results identified waterbird as one of the exogenous sources of nutrient loads. Additionally, an appropriate NEL/EL threshold (< 1.2) was determined for protecting waterbird diversity. Three conservation strategies were proposed based on these findings. This study could provide theoretical support for waterbird protection in natural reserves.