Litter mass loss and nutrient dynamics of four emergent macrophytes during aerial decomposition in freshwater marshes of the Sanjiang plain, Northeast China

BACKGROUND AND AIMS: In wetland ecosystems, the litter of emergent macrophytes generally begins to decay while standing, but aerial decomposition has often been overlooked. The goal of this study was therefore to elucidate the processes involved in the decomposition of standing litter of emergent macrophytes in freshwater marshes in the Sanjiang Plain, Northeast China. METHODS: We used the litterbag method to quantify litter mass loss, microbial respiration rates, and nutrient dynamics of four common emergent macrophytes (Carex lasiocarpa, Deyeuxia angustifolia, Glyceria spiculosa, and Phragmites australis) during one year of aerial decomposition. RESULTS: Following one year of aerial decomposition, the leaf and culm mass losses were 19.3–45.1 % and 14.3–23.1 %, respectively. Litter mass loss was closely related to microbial respiration rates and initial ratios of C:N and C:P. The fact that litter N concentrations increased during aerial decomposition resulted in net N immobilization. After one year of decay, however, there was a net release of P from the standing litter in all cases, but the temporal pattern of P concentrations varied between the decomposing litter of the four different species. CONCLUSIONS: Our results provide evidence that the decomposition of standing litter from emergent macrophytes contributes markedly to overall litter decay, and thus is a key component of C and nutrient cycles in temperate wetlands.