A 3-Year In-Situ Measurement of CO_2 Efflux in Coastal Wetlands: Understanding Carbon Loss through Ecosystem Respiration and its Partitioning

摘要

Understanding the link between ecosystem respiration (R-eco) and its influential factors is necessary to evaluate the sources of gaseous carbon loss in coastal wetlands. Seablite (Suaeda salsaPall.) is the main vegetation type pioneering temperate coastal wetlands in northeast China, and is generally an understudied wetland type. To evaluate the influence of environmental factors onR(eco), a multi-year in-situ experiment was carried out during the growing seasons of 2012 to 2014. Total CO(2)efflux was measured and separated further into soil microbial and belowground root respiration (Rs + r) and plant respiration (R-plant).R(eco)displayed strong seasonal variation, with effluxes as high as 845 to 1150 mg CO(2)m(-2) h(-1)during summer months and as low as 32 to 111 mg CO(2)m(-2) h(-1)during spring (when new shoots are sprouting) and fall (when plants are senescing) months. Aboveground plant structures contributed on average 79% to total plant biomass, and accounted for most of theR(eco)measured; i.e., 62-96% was associated asR(plant). Plant activity was strongly seasonal, accordingly drivingR(eco), with 1 g of soil-emergentS. salsabiomass (dry weight) producing approximately 1.58 mg CO(2)per hour towardR(eco)during mid-summer. When water level was below the soil surface,R(s + r)was exponentially correlated to air temperature. BecauseR(eco)forS. salsamarsh in the Liaohe Delta is controlled by plant growth cycles, inundation regime, and air temperature, this finding may be applied for national carbon budget estimation purposes fromS. salsawetlands throughout Northeast China and potentially close a key gap in understanding the role of this large wetland area in contributing to respiratory CO(2)emissions globally.