| 摘要: | 本研究自2012年7月至2013年5月期間對嘉南藥理科技大學人工濕地表面上流(Free water surface，FWS)濕地系統的進出流水質、二氧化碳(CO2)的釋放通量進行碳通量的質量收支平衡，使進一步了解FWS人工濕地系統是CO2的儲存的碳庫(carbon stock)還是釋放源。由於FWS濕地系統中擁有大量的大型水生植物蘆葦(reed)約佔了濕地面積的80%至90%，所以本研究以蘆葦對FWS濕地系統的CO2的釋放通量進行調查。 近年來濕地也被發現能從大氣中吸收二氧化碳，轉換為有機碳捕集於濕地土壤、底泥或植物碎屑中，具有可觀的碳吸存(carbon sequestration)能力。濕地能將大氣中CO2吸收或捕集於濕地的程序，稱之為碳匯(carbon sink)。本研究利用壓克力製的靜置式採氣罩，配合紅外線二氧化碳分析儀，現地監測人工濕地在水生植物存在下的二氧化碳交換通量，並由不同光照強度條件的二氧化碳交換通量監測結果，進一步計算濕地的總呼吸通量及濕地總初級生產量。調查場址為嘉南藥理科技大學人工濕地系統的表面流濕地單元，監測時間自2012年7月起，每月監測一次。在完全不透光條件下測得的濕地二氧化碳交換通量(NEE)均為正值，亦既呈淨釋放通量，介於632.4~789.9 mg C/m2/hr，此數值可視為濕地的總呼吸通量(TR)。當採氣罩透光比率增加，光照強度提高時，二氧化碳交換通量可轉為負值，亦既為淨吸收通量，在完全透光條件下測得的濕地二氧化碳交換通量則都呈淨吸收通量，介於-234.8~-762.0 mg C/m2/hr。將完全不透光條件下測得的二氧化碳交換通量減去不同透光條件測得的二氧化碳交換通量，即可得不同光照強度下濕地的總初級生產量(GPP)。本研究發現，濕地的總初級生產量隨著光合作用有效輻射值(PAR)的增加初期呈直線增加，當有效輻射值持續增加時總初級生產量呈最大的飽和值，經由線性迴歸可建立GPP-PAR之相關方程式，並求得最大總初級生產量(GPPmax)。本研究發現，不同採樣月份測得的濕地的最大總初級生產量之間呈顯著差異，最高的GPPmax值發生在2013年5月，最低值發生在2012年10月，顯示濕地的總初級生產量與植物的生長狀況、光照強度有關。本研究亦發現濕地的總呼吸通量與氣溫(T)呈顯著正相關，ER與T的關係符合阿瑞尼亞氏方程式。 本研究在不同月份所建立的GPP-PAR及ER-T兩項方程式，未來將可進一步使用於每日總初級生產量及總呼吸通量的估算，並可進一步推估濕地的每年淨生態系統初級生產量(NEP)，以了解人工溼地中的碳循環屬於源或匯。
Wetlands are important ecosystems on earth,which normally have high primary production and provide multi-functions of storm water retention, water resource conservation,habitats for wildlife,water quality improvement, weatherregulation, recreation, education etc. Wetlands are also found acting as a carbon sink that can absorb carbon dioxide (CO2) from the atmosphere, converting into organic carbon and being accumulated in wetland sediment or soil.This study monitored net ecosystem CO2 exchange (NEE) monthly in a constructed wetland (CW) system by using the static chamber technique employing a flow-path infrared CO2 analyzer,which was further used to estimate gross primary production(GPP) and total respiration(TR) of the wetland. The investigation was conducted in the free water surface flow (FWS)unit of the CW system located in Chia-Nan University of Pharmacy and Science since July, 2012. The measurements were performed under various intensity of photosynthetically active radiation (PAR) in the chamber so that the relationship between GPP and PAR could be obtained. The NEE flux measured in completely dark chamber is recognized as the TR, were all positive values, ranging from 632.4 to 789.9 mg C/m2/hr, which represented net CO2 emission from wetland to the atmosphere. When PAR in the chamber increased, the NEE turned to be negative values, which means net CO2 sequestration from the atmosphere to wetland. The NEE fluxes measured in transparent chamber were all negative values, ranging from -234.8~-762.0 mg C/m2/hr. The GPP was the subtraction of the NEE from the TR (GPP=TR-NEE). The GPP was found increasing proportionally to PAR and reaching to a maximum value (GPPmax) when further increasing PAR. During the study, the highest GPPmax occurred in May, 2013, whereas the lowest value in October, 2012, suggesting GPP varied seasonally.The relationship between TR and ambient temperature (T) was found to follow the modified Arrhenius Equation. Both the GPP-PAR and TR-Tcurves obtained in the study can be used to estimate daily GPP and TR for the whole year, and then annual net ecosystem production of the CW could be valuated. |
