Effects Of Saline Wetland Restoration And Use On Carbon Fixation And Decomposition Release Characteristics Of Reeds In The Western Songnen Plain

The global carbon cycle is currently a hot issue in international research,and wetlands are an important carbon reservoir for terrestrial ecosystems,serving the dual function of a carbon sink and a carbon source.As a typical type of inland wetland,the Soda saline reed wetland is currently facing a number of risks,including the degradation of natural wetlands,salinization and pollution from agricultural activities.In recent years,the ecological characteristics of the degraded saline wetlands have changed significantly through the restoration of the area through the"rice-reed-fish/crab"ecological agricultural development model.In this paper,we investigated the effects of degradation and restoration on the carbon fixation and decomposition of Reeds in a typical wetland restoration area in the western part of the Songnen Plain.The main findings of the study are as follows:1.restoration of saline wetlands is beneficial to reed growth and carbon sequestrationThe growth and carbon sequestration capacity of reeds in the rehabilitated wetlands are better than those in the degraded wetlands,and the total biomass of reeds in both the degraded and rehabilitated wetlands reached a maximum in summer(1373.87 g·m^-2 and 1897.51 g·m^-2).Reed plant height,basal stem thickness,number of nodes and leaf area all showed that degraded wetlands<restored wetlands and vice versa for density.Differences in hydrological conditions are the dominant factor leading to differences in the ecological characteristics of plants,with the above-ground parts of wetland plants being their most direct response.Carbon accumulation in different organs of reeds is closely related to their biomass,with high reed biomass resulting in relatively high carbon accumulation and sequestration capacity,and flooding being more beneficial for vegetation sequestration.The total carbon accumulation of reeds in degraded and restored wetlands ranged from 282.03 to 518.46 g·m^-2 and 487.81 to872.26 g·m^-2,respectively（p<0.01）.2.Restoration of saline wetlands helps to slow down the decomposition and carbon release of reed litterThe decomposition rate of reed litter is higher in degraded wetlands than in rehabilitated wetlands,at 0.00209 g·d^-1 and 0.00132 g·d^-1,respectively,and lower than in most estuarine salt marsh wetlands.After 351 d of decomposition,the residual rate of reed litter in degraded and restored wetlands was 63.90%and 73.62%,and the time required for 95%decomposition is4.34 a and 6.52 a.During the decomposition period from November to October,the litter decomposition showed a slow-fast-slow alternation.The carbon content of the reed litter was higher in the restored wetland,with both types of reed litter showing a net release of carbon during decomposition（p<0.01）,and the change in carbon content during litter decomposition is strongly influenced by the dry matter residual rate（p<0.01）.Environmental factors and litter quality are the main factors affecting their decomposition rates and carbon accumulation.With increasing temperature and precipitation,litter decomposition rates and carbon release rates tended to accelerate,and both reed litter decomposition rates were significantly and positively correlated with water and soil conductivity（p<0.05）.Salinity is the main factor influencing carbon accumulation in sodic saline wetlands,with increasing salinity inhibiting the release of carbon from the litter and promoting carbon accumulation.