| 摘要: | 濕地具有高生產量，能吸收大氣中二氧化碳(CO2)，轉換為有機碳捕集於濕地土壤及底泥和植物碎屑中。濕地能將大氣中的CO2吸收或捕集於濕地的程序，稱之為碳匯(carbon sink)。本研究利用位於台江國家公園內的國家級濕地七股鹽田濕地，進行潮間帶灘地初級生產量及溫室氣體(CH4、N2O)與底泥葉綠素a調查。之後進行碳通量的收支計算，進一步了解七股鹽田濕地潮間帶灘地是CO2的儲存場或產生源。
本研究自2011年1月至2012年2月期間監測七股鹽田濕地潮間帶不同底質灘地，分為沙地、泥沙地、泥地三種進行調查。以密閉式靜置氣罩法(closed static chamber)調查結果，灘地CH4年平均釋放通量沙地：5.6 g CH4-C m-2 yr-1，泥沙地：10 g CH4-C m-2 yr-1，泥地：11 g CH4-C m-2 yr-1，調查結果顯示三個底質灘地CH4為穩定釋放。N2O年平均釋放通量沙地：3.1 mg N2O m-2 yr-1，泥沙地：3.5 mg N2O m-2 yr-1，泥地：6.5 mg N2O m-2 yr-1，調查結果顯示灘地N2O的排碳量相當少。
研究結果顯示灘地月平均總初級生產量沙地範圍：1,639~8,312 mg C m-2 month-1，泥沙地範圍：1,350~12,415 mg C m-2 month-1，泥地範圍：5,872~31,402 mg C m-2 month-1，本研究結果月平均總初級生產量有顯著季節性變化，於夏季時總初級生產量較高。三個樣點互相比較下泥地比沙地及泥沙地有顯著較高的趨勢。
研究結果顯示灘地年平均總初級生產量沙地：40 g C m-2 yr-1，泥沙地：89 g C m-2 yr-1，泥地150 g C m-2 yr-1。年總呼吸量沙地：20 g C m-2yr-1，泥沙地：73 g C m-2 yr-1，泥地：110 g C m-2 yr-1。結果顯示泥地有較高的總初級生產量，其總呼吸量也相對較高，泥地淨初級生產量：40 g C m-2 yr-1。泥沙地淨初級生產量：16 g C m-2 yr-1，雖然泥沙地總初級生產量高於沙地但由於總呼吸量也較高因此淨初級生產量低於沙地，則沙地淨初級生產量：20g C m-2 yr-1，雖然沙地總初級生產量低於泥沙地但由於呼吸相對較低因此淨初級生產量高於泥沙地。七股鹽田濕地潮間帶灘地平均碳吸存通量為25 g C m-2 yr-1。結果顯示七股鹽田濕地潮間帶灘地為碳匯的場址。
灘地底泥葉綠素a含量沙地：0~2.2mg m-2，泥沙地：12~102 mg m-2，泥地：43.2~297 mg m-2。研究結果發現灘地土壤葉綠素a含量與總初級生產量有正相關性(沙地：R2 = 0.6808，泥沙地：R2 =0.7219，泥地：R2 =0.351)，顯示灘地有較高的葉綠素a含量，則其總初級生產力也較高。土壤有機碳密度研究結果沙地：1748 g C m-2，泥沙地：1977 g C m-2，泥地：3883 g C m-2。由於泥地土壤有較多的有機物，其次為泥沙地，最低為沙地，因此土壤有機碳密度也有上述明顯的變化。
Wetlands normally exhibit high productivity. Wetland plants can sequester CO2 from the atmosphere and transform into plant debris and organic matter accumulated in wetland sediment. The process of absorbing or capturing CO2 from the atmosphere is called Carbon Sequestration. This thesis investigated primary production, respiration, emission of greenhouse gases (CH4、N2O), and the Chlorophyll a in intertidal flat. The experimental site is in the Chiku salt-pan wetland, which is located at the Taijiang National Park. Then, a calculation of the carbon flux is performed to realize the intertidal flat in the Chiku salt-pan wetland is a carbon sink or a carbon source.
This study examined three different kinds of flats in the Chiku salt panwetland, which are sand flat, sand-mud flat, and mud flat, from January 2011 to the February 2012. The method used for measuring gas exchange fluxes is called static chamber technique. The result showed that the annual average emission fluxes of CH4 are 5.6 g CH4-C m-2 yr-1 in the sand flat, 10 g CH4-C m-2 yr-1 in the sand-mud flat, and 11 g CH4-C m-2 yr-1 in the mud land.
The results showed that the monthly average gross primary production (GPP) in the sand flat is within the range of 1,639~8,312 mg C m-2 month-1, 1,350~12,415 mg C m-2 month-1 in the sand-mud flat, and 5,872~31,402 mg C m-2 month-1 in the mud flat. This result showed the monthly average gross primary production has a marked seasonal variation; the value is higher in summer. Among the three sites, the value of GPP is highest in the mud flat. Annual average gross primary production in the sand flat is 40 g C m-2 yr-1, 89 g C m-2 yr-1 in the sand-mud flat, and 150 g C m-2 yr-1 in the mud flat. The annual ecosystem respiration is 20 g C m-2 yr-1 in the sand flat, 73 g C m-2 yr-1 in the sand-mud flat, and 110 g C m-2 yr-1 in the mud falt. The results indicated that the mud land a higher gross primary production and a higher total ecosystem respiration. Accordingly, the net ecosystem production (NEP) is 20 g C m-2 yr-1 in the sand land, is 16 g C m-2 yr-1 in the sand-mud flat, and 40 g C m-2 yr-1 in the mud flat.
The average carbon sequestration flux in the intertidal flat of the Chiku salt-pan wetland is 25 g C m-2 yr-1, which showed that the Chiku salt-pan wetland is a carbon sink rather carbon source. The content of the chlorophyll a in sediment is 0~2.2mg m-2 in the sand flat, 12~102 mg m-2 in the sand-mud flat, and 43.2~297 mg m-2 in the mud flat. The results showed a positive correlation between the chlorophyll a content on the beaches sediment and the gross primary production (R2 = 0.6808 for the sand flat, R2 =0.7219 for the sand-mud flat, and R2 =0.351 the mud flat). The results indicated that the higher the content of the chlorophyll a on the flat sediment is, the higher the gross primary production will be. Organic carbon density is 1,748 g C m-2 for the sand flat, 1,977g C m-2 for the sand-flat flat, and 3,883 g C m-2 for the mud flat. The organics are more in the mud land, followed by the sand-mud flat, the last one is the sand flat. |
