In-Situ CO2 Partitioning Measurements in a Phragmites australis Wetland: Understanding Carbon Loss through Ecosystem Respiration

Abstract

Common reed (Phragmites australis) is dominant vegetation of temperate coastal wetlands in northeast China. To studying the link between ecosystem respiration (Reco) and its influential factors, a multi-year in-situ experiment was carried out in a newly restored wetland during the growing seasons of 2012 to 2014. Total in-situ Reco was separated into soil microbial and belowground root respiration (Rs + r) and plant respiration (Rplant). The soil microbial respiration rate (Rs) was isolated from Rs + r, making it easier to understand each component of Reco. With the wetland restoration process, the seasonal average aboveground biomass (dry mass) increased from 411.5 g m−2 to 2048.1 g m−2 and the corresponding Reco increased from 751.78 mg CO2 m −2 h−1 to 2612.41 mg CO2 m −2 h−1. Rplant contributed averagely 69% ~ 71% to Reco on the whole seasonal scale and the plant activity was strongly seasonal. With 1 g of aboveground common reed biomass (dry weight), approximately 3.6 mg CO2 would be produced per hour during the sprouting period while it could be as low as 0.3 mg CO2 during plant senescence period. Inundation regime dominated the contribution of Rs to Reco and the flooded contribution would lower the Rs contribution to as low as 11%.