气候变化领域集成服务门户

Plant litter (including standing litter) modification plays a vital role in wetland carbon (C) balance, which can be greatly altered by global change. Our knowledge of the fundamental function of plant litter in ecosystem respiration (Re) is crucial for evaluating C exchange between the atmosphere and biosphere. However, it is not well understood how litter manipulation could influence the dynamics of Re and its temperature sensitivity (Q(10)) in wetland ecosystems. In the present study, we conducted a field manipulation experiment with the following treatments of total aboveground plant litter removal (ALR), standing litter exclusion (AR), doubled plant litter (DL) and unchanged litter input (CK) to study the effects of wetland plant litter on Re and Q(10) values over two growing seasons (2015 and 2016) in a Deyeuxia angustifolia-dominated freshwater marsh in the Sanjiang Plain, Northeast China. Results showed that wetland Re was significantly affected by different plant litter input manipulations. During the two growing seasons, the Re ranged from 27.16 to 643.61 (ALR), 39.61-690.25 (AR), 136.27-1270.38 (DL) and 72.11-862.42 mg CO2-C m(-2) h(-1) (CK), which decreased by 28.36-68.04% and 15.11-63.23% of the ALR and AR treatments and increased by 15.41-20.59% of the DL treatment compared with CK, respectively. The changes in Re was more susceptible to litter removal effects. In 2016, the mean Re values of ALR and AR treatments decreased significantly compared with the corresponding values in 2015, while it was significantly increased in the DL treatment. The concentrations of NH4+ and DOC, as microbes directly used carbon and nitrogen sources in soil pore water were significantly affected by litter input manipulations suggesting that there are various carbon and nitrogen sources within and outside the plant litter. The Q(10) values of Re under each litter input manipulation treatment differed markedly, and the highest value (3.32-4.06) occurred in the total plant-derived litter input removal treatments indicating that the wetland soil was vulnerable to disturbance that prone to carbon losses in the context of global warming. Our results also demonstrated that the Q(10) values of the deeper soil (below 15 cm) with vegetation present were lower than that for the other litter removal treatments implying the important function of the carbon sink in this wetland ecosystem. Overall, we recommend that the role of wetland plant litter input to the soil system should be seriously considered when predicting biosphere-atmosphere C exchange model under the background of global climate change.