Higher fluxes of C, N and P in plant/soil cycles associated with plant invasion in a subtropical estuarine wetland in China

Abstract

Invasion of plants in wetland ecosystems is often associated with changes in litter decomposition and in nutrient use, uptake and cycling between invasive and native plants. We studied litter decomposition rates, N and P release and elemental composition and stoichiometry during the invasion of Phragmites australis and Spartina alterniflora into native Cyperus malaccensis wetlands in the Minjiang River estuary (China). Aboveground litter in mono-specific stands decomposed faster for Cyperus malaccensis than for Spartina alterniflora and for Phragmites australis. Cyperus malaccensis litter decomposed slower under the stands of both invasive species. In contrast, the litter of both invasive species decomposed faster under Cyperus malaccesis stands. We observed that the invasion of these species was associated with an increased rate of aboveground litter decomposition and large absolute amounts of C, N and P released from the litter when litter from invasive species was mixed with that of native species. Our results suggest that the large nutrient release from litter during early stages of the invasion favored invasive species with larger size and higher nutrient-uptake capacity than the native species.

Keywords: C:N; C:P; Cyperus malaccensis; Ecological stoichiometry; Litter mineralization; N:P; Nitrogen; Phosphorus; Phragmites australis; Soil carbon; Spartina alterniflora.