排水對若爾蓋高寒沼澤CO2和CH4排放通量的影響

周文昌,崔麗娟,王義飛,李 偉,康曉明

排水對若爾蓋高寒沼澤CO2和CH4排放通量的影響

周文昌1,2,崔麗娟1,3*,王義飛1,3,李 偉1,3,康曉明1,3

(1.中國林業(yè)科學(xué)研究院濕地研究所,濕地生態(tài)過程與功能北京市重點實驗,北京 100091；2.湖北省林業(yè)科學(xué)研究院,湖北 武漢 430075；3.四川若爾蓋高寒濕地生態(tài)系統(tǒng)國家定位觀測研究站,四川 若爾蓋 624500)

建立3塊標(biāo)準(zhǔn)樣地(天然沼澤、1990s和1970s排水沼澤),于2014年生長季期間,采用靜態(tài)箱-快速溫室氣體分析儀野外原位觀測CO2和CH4排放通量.結(jié)果表明:沼澤排水增加了土壤溫度(5,20,45cm),但降低沼澤水位;1990s[(680±329) mg CO2/(m2×h)]和1970s排水沼澤[(973±234) mg CO2/(m2×h)]生態(tài)系統(tǒng)CO2排放通量分別較天然沼澤增加了200%和330%,但CH4排放通量[(0.78±0.52) mg CH4/(m2×h)]和[(-0.01±0.02) mg CH4/(m2×h)]較天然沼澤分別降低了90%和100%;綜合考慮兩者排放通量,1990s[(186±89) mg C/(m2×h)]和1970s排水沼澤[(265±64) mg C/(m2×h)]生態(tài)系統(tǒng)碳(C)排放通量較天然沼澤分別增加了180%和300%.天然沼澤、1990s和1970s排水沼澤生態(tài)系統(tǒng)CO2排放通量與5cm土壤溫度存在顯著正相關(guān),而僅1990s排水沼澤生態(tài)系統(tǒng)CO2排放通量與水位存在顯著負相關(guān).天然沼澤生態(tài)系統(tǒng)CH4排放通量與土壤溫度(5,20,45cm)存在顯著正相關(guān),但1970s排水沼澤生態(tài)系統(tǒng)CH4排放通量與土壤溫度(20,45cm)存在顯著負相關(guān),1990s排水沼澤生態(tài)系統(tǒng)CH4排放通量與水位存在顯著正相關(guān).沼澤排水顯著增加了若爾蓋高寒沼澤生態(tài)系統(tǒng)C排放通量,降低了沼澤C匯功能,可能增強區(qū)域氣候變暖.

排水；CO2排放通量；CH4排放通量；溫室氣體；若爾蓋沼澤

溫室氣體CO2、CH4和N2O是導(dǎo)致全球氣候變暖的主要影響因素[1].天然沼澤地作為大氣CO2的匯,同時作為大氣CH4排放源[2-5],植被每年通過光合作用同化的CO2有4%~20%轉(zhuǎn)化為CH4排放到大氣中[6-8],約占全球CH4排放總量的20%~40%[1,9].天然沼澤因其長期具備的微弱碳匯[12.8~23g/(m2×a)],導(dǎo)致土壤儲存了大約600×1015g 碳[10-11],相當(dāng)于全球陸地土壤碳庫的30%[10]和大氣中碳庫(828×1015g碳)的70%[1].因此,沼澤溫室氣體CO2和CH4排放通量變化,將影響著未來氣候的變化趨勢.

由于人類活動的加劇,大量沼澤地被人為疏干,排除沼澤地多余的水分和控制地下水位,是沼澤地開發(fā)利用的關(guān)鍵,沼澤地為林業(yè)、農(nóng)業(yè)排水或為能源開采等利用,已導(dǎo)致全球5000萬hm2的沼澤地損失[12].人類活動嚴重改變了沼澤地土壤地下水位,影響沼澤地溫室氣體CO2和CH4排放通量[13-15],從而影響沼澤地碳匯功能和大氣中CO2和CH4含量.據(jù)Martikainen等[16]研究,北方泥炭地排水導(dǎo)致礦養(yǎng)型泥炭地(fen)和雨養(yǎng)型泥炭地(bog)的CO2和CH4排放通量存在差異,排水均是增加CO2排放通量和降低CH4排放通量;但是Strack等[17]研究的北方泥炭地排水,導(dǎo)致了微地貌草丘(hummock)區(qū)泥炭地CH4排放通量顯著降低97%,而微地貌洼地(hollow)區(qū)泥炭地與對照地?zé)o顯著影響,并且仍觀測到較高CH4排放通量.不同泥炭地類型,排水導(dǎo)致沼澤地CO2和CH4排放通量具有顯著差異,進而影響沼澤地CO2和CH4的排放通量.

若爾蓋高寒沼澤地約46萬hm2,分別占全國泥炭地面積和碳儲量的12%和40%,是我國泥炭最大分布區(qū),亦是世界最大高原沼澤之一[18].自1955年便開始對本區(qū)沼澤地開溝排水,到20世紀(jì)70年代,全區(qū)普遍采取大規(guī)模開溝排水,改造沼澤,經(jīng)過多次開溝排水,累積達20萬hm2沼澤采取了不同程度的改造,以增加區(qū)域草場用地,導(dǎo)致沼澤地大量銳減[18-21],目前有關(guān)該區(qū)域的沼澤地溫室氣體CO2和CH4排放通量的研究集中天然沼澤地[22-24],很少報道人類活動(如沼澤地排水)對若爾蓋高寒沼澤地溫室氣體CO2和CH4排放通量的影響研究.作者選擇若爾蓋濕地自然保護區(qū)不同時期排水沼澤(1970s和1990s排水沼澤)和天然沼澤(未排水沼澤),采用靜態(tài)箱和快速溫室氣體分析儀原位觀測沼澤溫室氣體CO2和CH4排放通量,旨在揭示排水對若爾蓋高寒沼澤CO2和CH4排放通量的影響規(guī)律及控制因子.

1 研究區(qū)域與研究方法

1.1 研究區(qū)概況

若爾蓋濕地自然保護區(qū)(102°29′E~102°59′E, 33°25′N~34°80′N),面積16670.6hm2.若爾蓋高原位于青藏高原的東北邊隅,平均海拔3400~3700m,沼澤是本區(qū)域的特色,土壤主要類型為亞高山草甸土、草甸土和沼澤土[18].該區(qū)域?qū)儆诟咴疁貛駶櫄夂?常年無夏,11月至次年4月受西伯利亞和蒙古冷空氣控制,5~10月受西南季風(fēng)控制,無絕對無霜期,每年9月下旬土壤開始凍結(jié),5月中旬完全解凍,凍土最深達72cm,年均氣溫0.7~1.0℃,最高氣溫和最低氣溫出現(xiàn)于7月和1月,各自氣溫均值10.7,-10.3℃,年均降水量650mm,集中在6~9月,相對濕度78%[24-26].

1.2 樣地選擇

2013年夏季期間在若爾蓋濕地自然保護區(qū)選取天然沼澤(33°55.39′N,102°52.16′E,海拔3439m)、1990s(33°55.2′N,102°48.9′E,海拔3438m)和1970s排水沼澤(33°55.2′N,102°44.1′E,海拔3432m)的3個樣地,3個樣地位于花湖湖泊周邊,沼澤地形成時間大概一致.天然沼澤水位接近地表,植物類型以木里薹草()和西藏嵩草()為主,伴生條葉垂頭菊(),并發(fā)育許多微地貌草丘(hummocks)或洼地(hollows);為了擴大草場牧地,自1955年以來對本區(qū)域采取大規(guī)模開溝排水,疏干沼澤,經(jīng)調(diào)研1990s排水沼澤地,地表無積水,濕潤,植被類型主要以西藏嵩草為主,伴生少些花葶驢蹄草();1970s排水沼澤,地表無積水,極度干旱,主要植被類型以矮生嵩草()、鵝絨委陵菜()為主,伴生海乳草(),因樣地排水和放牧多年,網(wǎng)狀草丘已消失,出現(xiàn)危害草場動物黑唇鼠()和中華鼢鼠(sp.),隨之出現(xiàn)較多鼠兔洞穴,樣地趨向于退化階段,該樣地于2008年通過構(gòu)筑壩堤的堵溝方法,沿著排水溝間隔100m建立壩堤,以抬升水位,實施濕地恢復(fù)工程,但是本研究期間,自2010年后,該壩堤已遭受雨季期的雨水沖刷而損壞,從而水位逐年降低.

1.3 CO2和CH4排放通量測量

2014年5~10月,開展野外實驗研究,CO2和CH4排放通量測量采用靜態(tài)箱和快速溫室氣體分析儀(FGGA,DLT-100,Los Gatos Research Inc.,San Jose, USA)原位觀測[24].每個樣地重復(fù)設(shè)置3個以上靜態(tài)箱(天然沼澤3個,1990s排水沼澤3個,1970s排水沼澤設(shè)置9個靜態(tài)箱,是由于樣地排水溝相隔約為100、200和300m).靜態(tài)箱由鋁皮制作,規(guī)格為50cm× 50cm×50cm,為防止箱內(nèi)溫度波動,箱外用塑料泡沫包裹,箱內(nèi)頂部有2個小型風(fēng)扇,靜態(tài)箱頂部中央附有2個橡皮塞小圓孔,連接快速溫室氣體分析儀的2根附有橡皮塞的透明導(dǎo)氣管,長度約4m(內(nèi)徑為4mm),儀器通過12V的蓄電池供電,設(shè)置數(shù)據(jù)觀測頻率為1Hz[27-28].儀器啟動后,在測量CO2和CH4排放通量前,將底座水槽加滿水,防止頂箱扣在底座后,箱內(nèi)氣體泄漏.然后密閉靜態(tài)箱,測量箱內(nèi)頂部氣體CO2和CH4含量,密閉測量5min(蓋箱的讀數(shù)時間),然后揭開靜態(tài)箱,置于開放狀態(tài)約2min,目的是等待箱頂部氣體含量穩(wěn)定,緊接著連續(xù)操作以上過程,測量下一個靜態(tài)箱位置區(qū)沼澤地兩種排放通量,直到完成所有測量樣點.排放通量測量時間:對照地(天然沼澤)測量時間為5~9月,1990s排水沼澤測量為5~10月,1970s排水沼澤測量為5~9月,均是北京時間早上9:30~11:00.CO2和CH4排放通量是以封閉箱內(nèi)頂部CO2和CH4含量隨時間變化的直線斜率計算[27-28], CO2和CH4排放通量計算公式見文獻[29].

同時,采用數(shù)字溫度計(JM624,天津今明儀器有限公司),測量采樣點5,20,45cm深度的地溫;在靜態(tài)箱附近挖了一個小井,測量地下水位,測量井的深度為地表之下100cm,如超出100cm深度,以-105cm記錄水位值,水位直接用直尺測量,水位為正值表示水位位于土壤地表之上,水位為負值表示水位位于土壤地表之下.

采用獨立樣本檢驗方法,利用SPSS 18.0軟件,CO2和CH4排放通量的差異性采用配對-檢驗.CO2和CH4排放通量與溫度和水位環(huán)境因子采用Pearson相關(guān)分析.顯著差異水平=0.05.利用Origin 9.0軟件制圖.

2 結(jié)果與分析

2.1 排水對沼澤土壤溫度和水位的影響

CK: 天然沼澤; D90s: 1990s排水沼澤; D70s: 1970s排水沼澤

由圖1可知,2014年5~9月觀測期間,沼澤排水后,沼澤土壤溫度升高.天然沼澤、1990s和1970s排水沼澤土壤5cm溫度平均值分別為10.1,10.4, 12.9℃;土壤20cm溫度平均值分別為10.3,10.6, 10.1℃;土壤45cm溫度平均值分別為8.3,10.6, 8.9 ℃.沼澤排水后,水位顯著降低(圖1d).天然沼澤、1990s排水沼澤水位平均值分別為0.7, -56.8cm,而1970s排水沼澤水位觀測期間,測量井100cm深度始終不見有水,從而以-105cm作為記錄1970s排水沼澤水位.

2.2 排水對沼澤生態(tài)系統(tǒng)CO2和CH4排放通量的影響

2014年生長季期間,沼澤排水后,沼澤生態(tài)系統(tǒng)CO2排放通量增加(圖2a).天然沼澤、1990s和1970s排水沼澤生態(tài)系統(tǒng)CO2排放通量(平均值±標(biāo)準(zhǔn)差)分別為96~402mg CO2/(m2×h)[(223±94) mg CO2/ (m2×h)]、95~1284mg CO2/(m2×h)[(680±329) mg CO2/ (m2×h)]和579~1329mg/(m2×h)[(973±234) mg/(m2×h)]. 1990s和1970s排水沼澤生態(tài)系統(tǒng)CO2排放通量平均值較天然沼澤分別增加了約200%和330%.配對-檢驗發(fā)現(xiàn),天然沼澤與2個排水沼澤生態(tài)系統(tǒng)CO2排放通量平均值之間存在極顯著差異(<0.01),2個排水沼澤生態(tài)系統(tǒng)CO2排放通量平均值之間存在顯著差異(<0.05).

2014年生長季期間,沼澤排水后,沼澤生態(tài)系統(tǒng)CH4排放通量降低(圖2b).天然沼澤、1990s和1970s排水沼澤生態(tài)系統(tǒng)CH4排放通量(平均值±標(biāo)準(zhǔn)差)分別為1.02~17.43mg CH4/(m2×h)[(7.04±4.46) mg CH4/(m2×h)]、0.11~2.06mg CH4/(m2×h)[(0.78±0.52) mg CH4/(m2×h)]和-0.04~0.04mg CH4/(m2×h)[-0.01± 0.02] mg CH4/(m2×h)](負值為大氣CH4匯).1990s和1970s排水沼澤生態(tài)系統(tǒng)CH4排放通量平均值較天然沼澤降低了約90%和100%.配對-檢驗發(fā)現(xiàn),天然沼澤、1990s和1970s排水沼澤生態(tài)系統(tǒng)CH4排放通量平均值之間存在極顯著差異(<0.01).

綜合沼澤生態(tài)系統(tǒng)CO2和CH4排放通量,2014年生長季期間,沼澤排水后,沼澤生態(tài)系統(tǒng)碳(C)排放通量顯著增加(圖2c).天然沼澤、1990s和1970s排水沼澤生態(tài)系統(tǒng)C排放通量(平均值±標(biāo)準(zhǔn)差)分別為29~123mg C/(m2×h)[(66±28) mg C/(m2×h)]、25~ 351mg C/(m2×h)[(186±89) mg C/(m2×h)]和158~ 362mg C/(m2×h)[(265±64) mg C/(m2×h)].1990s和1970s排水沼澤生態(tài)系統(tǒng)C排放通量較天然沼澤增加了約180%和300%.配對-檢驗發(fā)現(xiàn),天然沼澤與2個排水沼澤生態(tài)系統(tǒng)C排放通量平均值之間存在極顯著差異(<0.01),2個排水沼澤生態(tài)系統(tǒng)C排放通量之間存在顯著差異(<0.05).

CK:天然沼澤; D90s: 1990s排水沼澤; D70s: 1970s排水沼澤

2.3 沼澤生態(tài)系統(tǒng)CO2和CH4排放通量與土壤溫度和水位的關(guān)系

2014年生長季期間,天然沼澤、1990s和1970s排水沼澤生態(tài)系統(tǒng)CO2排放通量與5cm土壤溫度均存在顯著線性正相關(guān)(<0.05),僅1990s排水沼澤生態(tài)系統(tǒng)CO2排放通量與水位存在顯著線性負相關(guān)(<0.05,表1).天然沼澤生態(tài)系統(tǒng)CH4排放通量與土壤溫度(5,20,45cm)存在顯著線性正相關(guān)(<0.05),然而1970s排水沼澤生態(tài)系統(tǒng)CH4排放通量與20,45cm土壤溫度存在顯著負相關(guān)(<0.05),僅1990s排水沼澤生態(tài)系統(tǒng)CH4排放通量與水位存在顯著線性正相關(guān)(<0.05,表1).

表1 沼澤生態(tài)系統(tǒng)CO2和CH4排放通量與溫度和水位的相互關(guān)系

CK: 天然沼澤; D90s: 1990s排水沼澤; D70s: 1970s排水沼澤.

3 討論

3.1 與其他研究的沼澤地CO2和CH4排放通量的比較

本研究沼澤CO2[96~1329mg CO2/(m2×h)]和CH4排放通量[-0.04~17.43mg CH4/(m2×h)]與其他研究范圍吻合[CO2排放通量:14~1050mg CO2/(m2×h), CH4排放通量:-0.02~86.78mg CO2/(m2×h),表2],不過有研究表明,北方排水泥炭地生態(tài)系統(tǒng)CO2排放通量峰值高達3310mg CO2/(m2×h)[33].然而,泥炭地排水多集中在溫帶和寒溫帶沼澤區(qū)域,這些實驗研究表明,沼澤地排水后,水位的降低,CO2排放通量增加達30%~380%[16,33,36-37],這與本研究增加的比例吻合(200%和330%).而CH4排放通量降低達60%~ 98%[16,36,38]或轉(zhuǎn)為大氣CH4吸收匯[13,38-39],這也與本研究降低的比例吻合(90%和100%)(表2).

表2 不同區(qū)域沼澤濕地CO2和CH4排放通量

3.2 水位和溫度對沼澤地CO2和CH4排放通量的影響

據(jù)研究報道,沼澤地CO2和CH4排放通量主要受水位和溫度的影響[4,16,36-37].沼澤地排水,降低了沼澤地水位深度,2014年生長季5~9月上旬期間,1990s排水沼澤水位低于地表之下60cm深度,1970s排水沼澤水位低于地表之下100cm,沼澤水位的降低,將增加了空氣進入下層土壤,加速土壤有機質(zhì)分解,增加土壤呼吸通量(CO2排放通量).另外,沼澤水位下降,土壤暴露于太陽輻射下,土壤溫度增加,土壤微生物活性增強,進而提高土壤呼吸,增大了土壤呼吸通量[40].這可從本研究沼澤地CO2排放通量與5cm土壤溫度均存在顯著線性相關(guān)得到證實,與其他研究的北方沼澤的結(jié)論吻合[16,36-37,41].沼澤地排水降低了CH4排放通量[16,38,42],這是由于沼澤地釋放到大氣中的CH4是由產(chǎn)甲烷菌在嚴格厭氧條件下產(chǎn)生的[24,43],沼澤地在CH4產(chǎn)生量很低的情況下,還需經(jīng)過甲烷氧化菌氧化CH4,從而減少CH4排放通量[14].因此,水位在調(diào)控沼澤CH4排放通量的過程中發(fā)揮關(guān)鍵性作用[43-44].在水位較高條件下,隨著氣溫增加,沼澤土壤溫度增加,植被生產(chǎn)力也逐漸增加,從而增強產(chǎn)甲烷菌活性和產(chǎn)CH4量,通常加速CH4生成和大量CH4釋放[22,44],這就是沼澤地CH4排放通量常與土壤溫度存在顯著線性正相關(guān)和在夏季7月或8月觀測到峰值的原因[22,44].反之,沼澤水位降低后,CH4排放通量與土壤溫度存在顯著負相關(guān)或不相關(guān)[42,44].這是由于當(dāng)沼澤受到干擾后,沼澤CH4產(chǎn)生和釋放過程的環(huán)境因子(水位、溫度和植被類型)發(fā)生了改變[45],導(dǎo)致沼澤CH4排放通量與環(huán)境因子之間的關(guān)系趨向復(fù)雜[46],很難再使用沼澤CH4排放通量與環(huán)境因子(水位或地溫)之間的關(guān)系定量化[45].因此,人為干擾(如森林沼澤采伐、沼澤排水)改變了原先沼澤CH4排放通量與土壤溫度或與水位的相互關(guān)系[46-47],這可能是1990s排水沼澤CH4排放通量與水位存在正相關(guān),1970s排水沼澤CH4排放通量與土壤溫度存在負相關(guān)的原因.

3.3 沼澤地排水對C匯功能和溫室效應(yīng)的影響

綜述以上結(jié)果,沼澤排水增加CO2排放通量,但降低CH4排放通量.本研究表明,排水沼澤地C排放通量較天然沼澤顯著增加了180%和300%,這可能降低沼澤作為大氣的C匯強度,從而降低沼澤土壤碳儲量.這種推測驗證了本團隊曾研究的若爾蓋高寒沼澤排水導(dǎo)致土壤有機碳儲量降低了349.7t C/hm2的結(jié)論[48],這說明沼澤排水通過顯著增加C排放通量,降低了土壤碳儲量,使得沼澤地從大氣C吸收匯轉(zhuǎn)為大氣C排放源,隨后降低碳匯功能.但據(jù)Renou-Wilson等[49]研究表明排水的雨養(yǎng)型泥炭地還濕后,并加強管理,已使得泥炭地轉(zhuǎn)變?yōu)樘紖R.因此,在今后的沼澤地管理中,要避免沼澤地排水的管理方式,從而通過項目工程加緊堵塞沼澤排水溝,不斷抬升沼澤地下水位,減少溫室氣體排放,從而增強沼澤固碳功能.

在全球氣候變暖的背景下,可能降低沼澤水位,并增加土壤溫度.據(jù)若爾蓋高寒區(qū)域近50年的氣候變化(1957~2011年)表明,該區(qū)域降水量以每年-0.978mm的速率減少,氣溫和潛在蒸發(fā)量卻以每年0.029℃和0.755mm的速率增加[50],該區(qū)域?qū)⒖赡苴呌跉夂蜃兣兏?可能降低該地區(qū)沼澤水位和增加土壤溫度,從而將影響溫室氣體排放通量[51].因此,根據(jù)本研究結(jié)論,未來將增加天然沼澤、排水沼澤CO2排放通量,但對于天然沼澤來說,可能增加CH4排放通量,也可能降低CH4排放通量,從而存在不確定性;反而對于排水沼澤,一定會降低CH4排放通量.根據(jù)IPCC第五次評估報告,CH4單分子(摩爾)的溫室效應(yīng)跨過100年時間是CO2的34倍[1];再根據(jù)Ding等[26]預(yù)算若爾蓋高寒沼澤生長季CH4排放量以165d計算,基于這兩個數(shù)值和本研究的生長季沼澤生態(tài)系統(tǒng)CO2和CH4排放通量平均值,估算1990s和1970s排水沼澤溫室氣體CO2當(dāng)量(分別為61和88mol CO2/m2)較天然沼澤(20mol CO2/m2)增加了200%和335%,這種大量的溫室氣體CO2排放到大氣中,將加速該區(qū)域氣候變暖.如果不加以人類干擾控制沼澤地的破壞活動和恢復(fù)退化的沼澤地,最終會使得這種氣候變化進入到一種惡性循環(huán)中.

4 結(jié)論

4.1 若爾蓋高寒沼澤地排水,顯著增加了CO2排放通量,但降低了CH4排放通量,甚至1970s排水沼澤地轉(zhuǎn)為大氣CH4吸收匯.綜合考慮生態(tài)系統(tǒng)C排放通量,沼澤地排水顯著增加了C排放通量達180%~ 300%.

4.2 3種沼澤地(天然沼澤地、1990s和1970s排水沼澤地)CO2排放通量與5cm土壤溫度均存在正相關(guān),僅1990s排水沼澤地CO2排放通量與水位存在顯著負相關(guān).天然沼澤地CH4排放通量與土壤溫度(5,20,45cm)存在顯著正相關(guān),而1970s排水沼澤地CH4排放通量與土壤溫度(20,45cm)存在顯著負相關(guān),僅1990s排水沼澤地CH4排放通量與水位存在顯著正相關(guān).

4.3 若爾蓋高寒區(qū)域的氣候變化可能導(dǎo)致沼澤地溫室氣體CO2和CH4的排放存在不確定.2種排水沼澤地溫室氣體CO2當(dāng)量(含CH4折算)比未排水沼澤地增加了200%和335%,這種人類活動(如沼澤地排水)可能加劇該區(qū)域氣候變暖.

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Effects of drainage on the CO2and CH4emission fluxes in the Zoigê Plateau Marsh.

ZHOU Wen-chang1,2, CUI Li-juan1,3*, WANG Yi-fei1,3, LI Wei1,3, KANG Xiao-ming1,3

(1.Beijing Key Laboratory of Wetland Services and Restoration, Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China；2.Hubei Academy of Forestry, Wuhan 430075, China；3.Sichuan Zoigê Wetland Ecosystem Research Station, Ruoergai 624500, China)., 2019,39(7)：3040~3047

The CO2and CH4emission fluxes in the Zoigê Plateau Marsh were monitored by using the dark static chamber and Fast Greenhouse Gas Analyzer at three typical sampling sites (natural marsh, drainage marshes in the 1990s and 1970s) from May to October in 2014. The results showed that the drainage increased the soil temperature (5, 20 and 45cm depth) and reduced the water level. The ecosystem CO2emission fluxes of the drained marshes in 1990s [(680±329) mg CO2/(m2×h)] and 1970s [(973±234) mg CO2/(m2×h)] were 200% and 330% higher than that in the natural marsh. While, the ecosystem CH4emission fluxes of the drained marshes in 1990s [(0.78±0.52) mg CH4/(m2×h)] and 1970s [(-0.01±0.02) mg CH4/(m2×h)] were 90% and 100% lower than that in the natural marsh, respectively. Taking into consideration of both CO2and CH4emission fluxes, the ecosystem carbon (C) emission fluxes of the drained marshes in 1990s [(186±89) mg C/(m2×h)] and 1970s [(265±64) mg C/(m2×h)] were 180% and 300% higher than that in the natural marsh. Besides, there was a significant positive correlation between the ecosystem CO2emission fluxes and the soil temperature of 5cm depth in the three typical sampling sites. Whereas, there was an obvious negative correlation between the ecosystem CO2emission flux and the water level in the 1990s drained marsh. In addition, the ecosystem CH4emission flux in the natural marsh was notably positively correlated with the soil temperatures at 5, 20 and 45cm depth. However, the ecosystem CH4emission flux in the 1970s drained marsh was remarkably negatively correlated with the soil temperatures at 20 and 45cm depth. Meanwhile, we also found that there was a significant positive relation between the ecosystem CH4emission flux in the 1990s drained marsh and the water level. This research suggested that the marsh drainage could significantly increase the ecosystem C emission flux from the soil into the atmosphere in the Zoigê Plateau Marsh, subsequently decrease the soil C sink function, and further enhance the regional climate warming.

drainage；CO2emission flux；CH4emission flux；greenhouse gas；Zoigê Plateau Marsh

X53

A

1000-6923(2019)07-3040-08

周文昌(1983-),貴州鎮(zhèn)遠人,助理研究員,博士,主要研究方向為濕地生態(tài)學(xué).發(fā)表論文20余篇.

2018-12-01

國家重點研發(fā)計劃項目(2016YFC0501804);中央級公益性科研院所基本科研業(yè)務(wù)費專項(CAFYBB2017QB009);國家林業(yè)局公益行業(yè)科研專項項目(201204201)

* 責(zé)任作者, 研究員, lkyclj@126.com