水生植物对淡水生态系统温室气体排放的影响研究进展

淡水生态系统温室气体(CO_2、CH_4、N_2O)排放是全球气候变化背景下的研究热点。水生植物作为淡水生态系统重要的组成部分,对水体生源要素的生物地球化学循环过程具有重要影响,进而影响水体温室气体产生与排放。本研究基于目前水生植物与水体温室气体排放关系的研究,探讨了水生植物对淡水生态系统温室气体排放动力学过程的影响,提出水生植物分布区可能是温室气体排放热点;水生植物种类、生活型的多样性增加了水体温室气体排放的变异性和不确定性,对监测和估算方法的准确性产生一定影响;进一步总结了水生植物对淡水生态系统温室气体排放的影响机制:1)机械作用,包括气体传输通道作用和浮叶植物的滞留作用; 2)水生植物光合/呼吸作用参与水体碳循环,同时水生植物凋落物分解为水体代谢提供新鲜碳、氮源,提高温室气体产生速率; 3)改变根际厌氧环境,影响根际CH_4和N_2O产生与排放; 4)水生植物群落改变水体生态因子分配格局,影响水体异养代谢等。基于当前研究现状,本文提出要进一步开展不同尺度或不同生境条件下水生植物种类、生活型和生长代谢等对水体温室气体排放动力学的影响研究,并从水生植物群落尺度构建温室气体排放动力学模型,优化监测方法与估算模型,为推进我国淡水生态系统温室气体排放研究提供理论基础。

Review on Effects of Aquatic Plants on the Greenhouse Gas Emission from Freshwater Ecosystems

The greenhouse gases (GHGs) emission from freshwater ecosystems, an important natural source of atmospheric greenhouse gases, had attracted extensive attention worldwide. As an important part of the freshwater ecosystem, aquatic plants played important roles in the biogeochemical process of water biogenic elements. Exploring the influence of aquatic plants on the greenhouse gas emission from freshwater ecosystems was of great significance to the understanding of ecosystem functions. In this study, based on current researches on the relationship between aquatic plants and greenhouse gas emissions from freshwater ecosystems, effects of aquatic plants on the dynamic process of GHG emission from freshwater ecosystems were discussed to propose that the water area with rich aquatic plants will be hotspots of the greenhouse gas emission. Meanwhile, on account of the multiplicity of life form and species of aquatic plants, the GHG emission from the freshwater ecosystem showed characteristics of high variability and uncertainty. The effect mechanisms of aquatic plants on CO₂, CH₄ and N₂O emissions from freshwater ecosystems were further summarized:1) the mechanical effects, including the gas transport channel effect and the retention effect of floating leaf plants; 2) the photosynthesis/respiration of aquatic plants affects the carbon cycle in water, while the decomposition of litters of aquatic plants provides fresh sources of carbon and nitrogen for the metabolism of aquatic organisms which increases the greenhouse gas production rate; 3) aquatic plants affect the generation and emission of CH₄ and N₂O by changing the anaerobic environment of the rhizosphere; 4) the aquatic plant community can change the distribution pattern of water ecological factors and affect the heterotrophic metabolism of aquatic organisms. Based on the current research status, this paper proposed that the further study should focus on influences of aquatic plant species, life forms and growth metabolism on the dynamic process of the greenhouse gases emission from water under different scales and different habitat conditions. In addition, a dynamic model of the greenhouse gas emission should be built based on the scale of aquatic plant community and the monitoring method and the estimation model should be optimized in further researches. This study can provide a theoretical basis for researches on the greenhouse gas emission in freshwater ecosystems of China.