Responses of plant productivity and diversity to drought in Carex schmidtii tussock wetlands, Northeast China

Global change projections predict more recurrent and intense drought events that along with their legacy effects have potentially long-term impacts on wetland ecosystem structure and function. Carex schmidtii tussocks in wetlands can form different microtopographies that maintain biodiversity and ecological balance. However, how these abiotic factors and their interactions drive C. schmidtii tussock wetland community dynamics and post-drought recovery are still unclear. Therefore, we selected three C. schmidtii tussock wetland types (drought, drought-rewetting, wetting) in the Momoge National Nature Reserve for further investigation. We combined relative importance value, alpha diversity, community similarity and productivity to explore drought and microtopography effects on plant community structure and function. Drought reduced biomass and C. schmidtii dominance, but increased richness and diversity. The degree of C. schmidtii dominance and community biomass was similar to those in the wetting wetland after drought-rewetting, but similarity was low. Plant diversity on tussock hummocks was lower than in hummock interspaces. Lower plant diversity was favorable for biomass accumulation among hummocks and in the overall community, but an opposite trend was found between hummock interspaces. Under drought, loss of C. schmidtii dominance and its biomass proportion resulted in lower hummock biomass, plant diversity, and richness compared to hummock interspaces. Furthermore, there would be significant differences in drought effects on plant similarity across the different microtopographies. Compared to hummock interspaces, hummock community structure was more similar to the overall community, was more susceptible to drought, and did not readily recover. Therefore, in restoration practice, C. schmidtii and hummock community structure should preferentially be restored, to ensure wetland recovery and stability.