辽河三角洲河口芦苇沼泽湿地植被固碳潜力

增加陆地生态系统碳汇是一种有效应对CO2浓度升高的措施。河口湿地是一类特殊的陆地生态系统,是生产力最高的生态系统之一。研究河口湿地的固碳潜力对准确评估河口湿地碳汇、发挥和提高湿地固碳功能具有重要意义。通过野外调查和数值模型,量化研究了辽河三角洲河口沼泽湿地的植被固碳潜力。根据区域的实际情况,将植被的固碳潜力分为湿地演替、人工灌溉苇田和气候变化的潜力。研究结果表明辽河三角洲河口沼泽湿地植被具有很高的固碳潜力,翅碱蓬(Suaeda pterantha)群落扩张每年可递增固碳潜力0.053—0.07Gg C,滩涂转变为芦苇(Phragmites australis)沼泽每年可递增固碳潜力0.07Gg C,芦苇、獐毛草甸(Aeluropus sinensis)演替为芦苇沼泽的固碳潜力为17.2 Gg C/a,通过灌溉管理措施,芦苇沼泽的固碳潜力为474.6—544.6 Gg C/a。根据未来气候变化情景和预测结果,到2030年、2050年、2100年,芦苇沼泽湿地的固碳潜力分别为576.9—655.1Gg C/a,603.3—684.1Gg C/a,680.9—769.4Gg C/a,其中由人工灌溉苇田的潜力最大。

Carbon sequestration potential of a Phragmites salt marsh in the Liaohe River estuarine wetland

Enhancing the carbon sink of terrestrial ecosystems has been suggested as a useful measure to ameliorate the greenhouse effect. Estuarine wetlands, characterized by high net primary productivity (NPP), have the highest carbon sequestration reported for terrestrial ecosystems. However, owing to the dynamic and complex environmental factors in estuarine wetlands, the enhancement of their carbon sink has not been well documented, and the amount of the carbon sequestration potential of estuarine wetlands remains unknown. Therefore, it is fundamental to investigate the carbon sequestration potential of estuarine wetlands to assess and enhance their carbon sink. The main objective of this study was to investigate the carbon sequestration potential of plants for Phragmites salt marshes in the Liaohe River estuarine wetland using field observations and numerical modeling. According to the practice managements and environmental characteristics in the Liaohe River estuarine wetland, the carbon sequestration potential of plants can be classified by wetland plant succession, Phragmites field irrigation, and the effect of climate change. The carbon sequestration potential of plant succession was calculated using the area expansion by tidal deposition and NPP. The ratio of tidal deposition was obtained from the LiaoNing Province Geological Monitoring Report, and the NPP was observed at field sampling sites. The carbon sequestration potential of Phragmites field irrigation was determined by the area of Phragmites fields and the maximum Phragmites NPP, which was modeled with the relationship between NPP and soil moisture, salinity, and irrigation depth. Soil moisture and salinity were measured using a WET Sensor, and irrigation depth was obtained from the Liaohe River Estuarine Wetland Management Office. The carbon sequestration potential of climate change was modeled using the Carnegie Ames Stanford Approach (CASA) model. The parameters in the CASA model were measured using a Moderate Resolution Imaging Spectroradiometer (MODIS) data product and meteorological variables, including air temperature, precipitation, and solar radiation, which were obtained from predicted results under projected climate change scenarios. The results suggested that the Phragmites salt marsh in the Liaohe River estuarine wetland has very high carbon sequestration potential, which could be enhanced by wetland succession and irrigation under the influence of the projected climate change in the future. NPP will be increased progressively by 53.18-70.91 MgC annually owing to the expansion of the Suaeda pterantha salt marsh, and by 70.32 MgC annually owing to the conversion of the tidal flat to a Phragmites salt marsh. It will increase by 17.2 GgC annually owing to the succession of Aeluropus littoralis meadows to Phragmites salt marshes, and by 0.47-0.54 TgC annually owing to the irrigation of Phragmites fields. The NPP of Phragmites salt marshes will increase to 1.33-1.49 TgC in 2030, which is 0.58-0.66 TgC higher than that in 2011. More than 94% of the carbon sequestration potential is a result of Phragmites field irrigation, whereas only 3.2% and 2.4% are a result of plant succession, and climate change, respectively. In 2050, the NPP of Phragmites salt marshes will increase by 0.61-0.68 TgC. The contribution of irrigation will decease to 90%, whereas the contribution of climate change will increase to 6% since the increasing temperature is favorable for plant photosynthesis. The NPP of Phragmites salt marshes will increase to 1.43-1.6 TgC in 2100, which is 0.68-0.77 TgC higher than that in 2011. The contribution of irrigation will decease to 80%, whereas the contribution of climate change will increase to 15%.