Effects of Agricultural Drainage on Plant Community in Bolboschoenus planiculmis Wetlands in Songnen Plain, China

Water scarcity frequently contributes to wetland degradation or functional loss. Although agricultural drainage can alleviate water deficits, this often comes at the cost of disrupting native vegetation succession and altering community structures. In the Songnen Plain of Northeast China, Bolboschoenus planiculmis, a dominant species in saline-alkaline wetlands, provides crucial food for the endangered Siberian crane (Grus leucogeranus). These wetlands, currently threatened by drought, increasingly rely on agricultural drainage for restoration. Previous research has focused on water table change and soil salinization effects, often overlooking the impacts of agricultural drainage-induced water environment changes. A two-year field study was conducted in the Momoge National Natural Reserve on the Songnen Plain, Northeast China from May to August in 2019 and 2020 to examine water environment parameters, vegetation growth, and reproduction characteristics, aiming to identify key factors influencing the plant community. Results reveal spatial heterogeneity in the plant community, with significant correlation between biomass, species diversity, tuber characteristics, and water parameters (P < 0.05), albeit with some annual variations. Redundancy analysis identifies water depth, nitrate nitrogen, dissolved oxygen, total dissolved solids, and total phosphorus as primary determinants of community changes (P < 0.05). Structural equation modelling demonstrates that water depth directly negatively affects species diversity and reproduction, while indirectly influencing productivity through its direct influence on water salinization. Phosphorus and nitrogen contents positively affect diversity and reproduction, exhibiting a trade-off relationship. These findings highlight the significant impact of agricultural drainage-induced water environment changes on community dynamics, with water parameters collectively influencing species diversity and reproduction through their synergistic and trade-off effects. This study provides valuable scientific insights for optimizing agricultural drainage management and facilitating ecological function restoration amidst ongoing global environmental changes.