Research Project: 人工濕地甲烷氧化活性與微生物族群結構之研究(1/2)
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摘要：人工濕地具有包含洪峰管理、水質淨化、棲地保存等生態系服務功能，其場域生長的植物更具有碳儲存與減低大氣淨溫室氣體含量的潛力。然而因其厭氧的土壤條件，卻也造成土壤中的微生物產生具有高熱吸存的溫室氣體，並降低濕地植物提供的淨碳儲存效益。而其中又以甲烷與二氧化碳排放最為重要。由於甲烷在大氣中的熱吸存能力為二氧化碳之25倍以上，因此溼地在甲烷平衡的研究急需要被客觀量化。然而台灣人工濕地溫室氣體排放研究，尚未累積足夠長期的數據資料，作為未來台灣評量人工溼地淨碳匯效益的依據。此外，新復育或建造的人工濕地，其土壤有機碳多以易分解形式存在，這些碳源的成分，是否會因為其自身容易分解，而增加土壤甲烷淨排放量，目前亦尚未有較具規模的研究。
本項研究主要分為兩大主軸，對於濕地甲烷氣體排放潛勢的研究部分，將以現地採集土壤，並以各種環境因子進行實驗室模擬培養，以瞭解人工濕地在各種可能管理方式下，其淨甲烷排放潛勢，並分析不同完工年份之人工濕地其土壤中有機碳組成比例對於甲烷排放量可能具有的影響，藉以評估人工濕地高熱吸存之溫室氣體排放的變化。而對於濕地甲烷排放相關的微生物族群，將針對所採集之土壤，使用次世代定序與實時螢光定量等分子生物學技術，透過16S rRNA、甲烷菌功能性基因mcrA及甲烷氧化菌功能性基因pmoA進行微生物定量、序列解析、親緣關係鑑定以及分子差異分析，探討台灣人工濕地土壤中與甲烷淨排放有關之微生物族群的組成、活性、豐富度，並比較不同環境因子變異可能帶給其族群結構之影響。藉以量化環境因子如何影響土壤細菌族群的具體關聯，並提出對未來人工濕地進行建造與管理的有效方式，以降低濕地甲烷排放並增進濕地淨碳儲存之生態系服務功能。
<br> Abstract: Constructed wetland is one of the ecological engineering practices that have been widely applied in Taiwan for waste water treatment, habitat restoration, ecosystem remediation, or storm water management. However, the diverse anaerobic soil conditions make wetlands major greenhouse gas (GHG) producers among the ecosystems and reduce the net carbon storage potentials of the constructed wetlands that may provide. Methane (CH4) is one of the major GHG that is 25 times more efficient than CO2 at trapping heat. Therefore, the CH4 emission from wetlands ecosystems is needed to be quantified to evaluate net C storage of constructed wetlands yet has not been fully studied in Taiwan. Moreover, the soil C in newly created wetlands is mainly attributed to fresh herbaceous litters, which contain considerable amounts of decomposable C. This readily decomposable C may serve as energy and C sources for soil methane producing bacteria and increases the net CH4 emissions at newly created wetlands. All of these factors that may influent CH4 emission will need to be detailed studied.
This research contains two major attempts. First, we will comprehensively evaluate the relations between environmental factors and CH4 producing potential from wetland soils to estimate the possible CH4 efflux from contracted wetlands under different management practices. Influences of different C sources in soils on CH4 emission will also be quantified to predict the changes of the flux rates with wetlands’ ages. Moreover, this study will also use the quantitative polymerase chain reaction and next-generation sequencing method of bacterial 16S rRNA gene, methanogenic mcrA gene and methanotrophic pmoA gene to better understand the compositions of soil microbial communities that are responsible to net CH4 emissions in constructed wetlands. We will also analyze the molecular variances among communities and clarify the effects of different environmental factors on bacterial community structure. With the knowledge of the relation among environmental factors, CH4 emission and soil microbial community structures, we shall be able to provide best management practices for constructed wetlands to improve C sequestration rate and minimize the CH4 emission from these ecosystems.
Keywords
人工濕地
甲烷
溫室氣體
土壤微生物
碳儲存
constructed wetlands
methane. soil microbial community
greenhouse gases
carbon sequestration
甲烷
溫室氣體
土壤微生物
碳儲存
constructed wetlands
methane. soil microbial community
greenhouse gases
carbon sequestration