生源要素有效性及生物因子对湿地土壤碳矿化的影响

湿地土壤是全球碳存储的重要场所,湿地生态系统的碳循环过程对全球变化有重要指示作用。土壤碳矿化是湿地生态系统碳循环的重要环节,对于认知湿地生态系统生物地球化学循环过程具有重要的意义。综述了生源要素及生物因素对湿地土壤碳矿化的内在作用机制。土壤活性有机碳库通过调节土壤能源物质和微生物活性影响土壤碳库的有效性,是表征土壤碳矿化的敏感指标。湿地其它养分如N、P、S等元素的有效性也是影响土壤碳矿化的关键要素。电子受体(NO₃^-、SO₄^2-、Fe³⁺、Mn⁴⁺等)对湿地土壤碳矿化和有机碳转变的影响主要通过电子受体的还原过程完成,在厌氧分解过程中,湿地土壤利用难溶性电子受体可能是土壤C矿化的更重要途径。动物、植物、微生物群落和区系等则是土壤碳矿化的主要驱动因子。土壤动物区系在有机态养分矿化为无机态养分的过程有着独特的功能,能显著增加土壤碳矿化。土壤微生物的活性,决定着土壤中有机碎屑的降解速率,是土壤有机碳分解周转的主要诱导因素。湿地植物则通过影响根系、微生物呼吸底物的供应以及对小气候和土壤因子的调节而影响土壤有机质的分解。湿地生源要素和生物因子还极易与土壤理化性质如温度、水分、pH值和质地等环境因素形成交互和制约,共同影响土壤碳矿化。最后,提出了进一步研究生源要素和生物因素与湿地土壤碳矿化关系需要解决的一些重要问题。

A review on the effects of biogenic elements and biological factors on wetland soil carbon mineralization

Wetland soils represent globally significant stocks of carbon, and an understanding of carbon cycling in the ecosystems has important implications for global climate change. Soil carbon mineralization is one of the important parts of the carbon cycle in wetland ecosystem. However our knowledge of the ecological processes that control carbon mineralization in wetland soil is limited. This paper reviews the intrinsic mechanisms of biogenic elements and biological factors which affect soil carbon mineralization in wetlands. The active organic carbon pool in the soil was an important sensitive indicator of carbon mineralization. The biogenic elements (N, S and P) were key elements controlling carbon mineralization. The electron acceptors (NO₃^-, SO₄^2-, Fe³⁺ and Mn⁴⁺) contribute to anaerobic carbon mineralization, explained by the reducing conditions found in most wetland studies, but the possible use of organic molecules (e.g., humic acids) as alternative electron acceptors was another potentially important pathway. Animal, plants and microorganism were also important driving factors. The fauna of wetland soil has special function in the decomposition, nutrient mineralization and other ecological processes of soil, which can increase soil carbon mineralization. Microbial biomass and its active control of organic detritus decomposition in soil were strongly correlated with carbon mineralization. Plant material can also alter the soil carbon mineralization rate by influencing microorganism activity by aeration near plant roots. It was noted that invasion by exotic species may influence soil carbon pools and soil carbon mineralization but results are inconsistent. Soil carbon mineralization in wetland ecosystems appear to be controlled by biogenic elements, biological factors, and interacting physical factors, e.g. soil temperature, moisture, pH and texture. Finally, we point out the problems that currently exist in studying the relationship between wetland soil carbon mineralization and controlling variables and present some proposals for further study.