Responses of Soil Respiration to Nitrogen Addition Across Different Habitats Induced by Lake Shrinkage

Soil respiration in lakeshore wetlands may vary with nitrogen addition and habitat differences associated with lake shrinkage, yet the responses of its components remain unclear. A controlled experiment at Daihai Lake was used to compare growing-season morning total soil respiration (Rs), autotrophic respiration (Ra), and heterotrophic respiration (Rh) between a wet meadow (WM) and an exposed lakebed (EL) using measurements collected from 2022 to 2024. Averaged across the three years, Rs, Rh, and Ra in the EL were 59.6%, 85.5%, and 38.7% of their respective levels in the WM. The differences were significant for Rs and Ra but not for Rh. Nitrogen addition had no significant overall effect on Rs, Rh, or Ra and did not interact significantly with habitat when averaged across years. However, Ra showed a significant nitrogen addition × habitat × year interaction. Model-averaged AIC weights indicated that aboveground and belowground biomass were associated with Rs, whereas aboveground biomass and soil moisture were associated with Ra. The SEM further showed statistical associations among nitrogen addition, habitat, vegetation biomass, soil moisture, Rs, and Ra, including a negative association between soil moisture and Ra. These findings indicate that nitrogen-addition effects on soil respiration were limited overall, while Ra responses varied among habitat–year combinations and were associated with vegetation characteristics in the studied lakeshore wetland. These findings provide insights into carbon cycling and support the sustainable management of lakeshore wetlands under global change.