ABSTRACT
Soil microbial carbon metabolism is critical in wetland soil carbon cycling, and is also a research hotspot at present. However, most studies focus on the surface soil layer in the wetlands and the microorganisms associated with this layer. In this study, 0-75 cm soil profiles were collected from five widely separated reed wetlands in the Songnen Plain, which has a large number of middle-high latitude inland saline-sodic wetlands. The Biolog-ECO method was used to determine the carbon metabolic activity and functional diversity of soil microorganisms. The results showed that soil carbon metabolic activity decreased with increasing soil depth. The carbon metabolic activity of soil microorganisms in the 60-75 cm layer was approximately 57.41%-74.60% of that in the 0-15 cm layer. The soil microbial Shannon index and utilization rate of amines decreased with an increase in soil depth, while the Evenness index and utilization rate of polymers tended to increase with soil depth. Dissolved organic carbon (DOC) is the most important factor affecting microbial carbon source utilization preference, because microorganisms mainly obtain the carbon source from DOC. The result of the correlation analysis showed that the soil microbial carbon metabolic activity, Shannon index, and Evenness index significantly correlated with soil total carbon (TC), microbial biomass carbon (MBC), DOC, total nitrogen (TN), ammonium nitrogen (NH4 +-N), nitrate nitrogen (NO3 --N) contents, and electrical conductivity (EC). This study emphasized the important role of microbial carbon metabolic function in deep soil.
ABSTRACT
Northern peatlands are typical nitrogen-limited ecosystems, which are sensitive to global climate change and human activities. The increases of endogenous available nitrogen caused by climate warming and exogenous nitrogen input caused by human activities changed the nitrogen availability of northern peatlands, and would affect carbon and nitrogen cycling and carbon sink function of peatland. Here, we review the influence factors of carbon accumulation rate and carbon sink function in northern peatlands. The effects of nitrogen deposition, freezing and thawing, fire and other factors on nitrogen availability of northern peatlands were reviewed. The responses of plants and soil microorganisms to changes in nitrogen availability were elaborated from carbon fixation and carbon emission processes, respectively. The research related to carbon sink function of peat ecosystems under the influence of glo-bal change was prospected, aiming to help the implementation of the 'double carbon' goal.
Subject(s)
Carbon Sequestration , Nitrogen , Humans , Nitrogen/analysis , Ecosystem , Carbon , SoilABSTRACT
The changes in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) were examined in order to assess the effect of surface layer soil (0 - 10 cm) under different land-use types after freshwater marshes tillage in the Sanjiang Plain Northeast China. Land uses were Deyeuxia angustifolia freshwater marshes ((DAM), cultivated land (CL), recovery freshwater marsh (RFM), constructed woodland (CW). After DAM soil tillage, MBC, MBN, DOC and DON declined strongly in agricultural surface soil layer, decreased 63.8%-80.5% (MBC), 56.3%-67.1% (MBN), 43.1%-44.3% (DOC) and 25.2%-56.1% (DON) respectively. In contrast, these C, N fraction had significant recovered in RFM and CW surface soil, increased 36.1%-59.9% (MBC), 46.7%-65.9% (MBN), 67.0%-69.3% (DOC)and 81.2%-88.3% (DON) respectively. Cultivation and land-use affected soil MBC, MBN, DOC and DON intensely. Therefore these labile C, N fractions have the significant relative under different land-use types. However DOC was more obvious controlled than DON by the land-use types. The relative between DOC and MBC, MBN have much difference than DON, the main reason of this distinction is the diverse source in available carbon and nitrogen that taken by microbial property under different land uses.
