Long-term harvesting of reeds affects greenhouse gas emissions and microbial functional genes in alkaline wetlands

Abstract

Reed (Phragmites australis) is dominant vegetation in alkaline wetlands that is harvested annually due to its economic value. To reveal the effects of harvesting reeds on the emission of greenhouse gases (GHG), the annual soil physicochemical characteristics and flux of GHGs in a reed wetland without harvesting (NHRW) and with harvesting (HRW) were measured. The results showed that after the harvesting of reeds, the total organic carbon (TOC) and total nitrogen (TN) significantly decreased, and soil temperature significantly increased. The annual cumulative N2O emissions decreased from 0.73 ± 0.20 kg ha−1 to −0.57 ± 0.49 kg ha−1 with the harvesting of reeds. The annual cumulative CH4 emissions also decreased from 561.88 ± 18.61 kg ha−1 to 183.13 ± 18.77 kg ha−1 with the harvesting of reeds. However, harvesting of reeds had only a limited influence on the annual cumulative CO2 emissions. A Pearson correlation analysis revealed that the CO2 and N2O emissions were more sensitive to temperature than the CH4 emissions. Both structural equation modeling (SEM) analysis and slurry incubation confirmed that higher temperatures offset the reduction of CO2 emissions after reed harvesting. Metagenomics showed that the abundance of functional genes involved in both GHG sink and source decreased with reed harvesting. This study presents a comprehensive view of reed harvesting on GHG emissions in alkaline wetlands, yielding new insight into the microbial response and offering a novel perspective on the potential impacts of wetland management.