朱先進,于貴瑞,王秋鳳,高艷妮,趙新全,韓士杰,閆俊華
(1. 中國科學院地理科學與資源研究所生態(tài)網(wǎng)絡觀測與模擬重點實驗室CERN綜合研究中心, 北京 100101; 2. 中國科學院大學, 北京 100049; 3. 中國科學院西北高原生物研究所, 西寧 810001; 4. 中國科學院沈陽應用生態(tài)研究所, 沈陽 110016; 5. 中國科學院華南植物園, 廣州 510650)
典型森林和草地生態(tài)系統(tǒng)呼吸各組分間的相互關系
朱先進1,2,于貴瑞1,*,王秋鳳1,高艷妮1,2,趙新全3,韓士杰4,閆俊華5
(1. 中國科學院地理科學與資源研究所生態(tài)網(wǎng)絡觀測與模擬重點實驗室CERN綜合研究中心, 北京 100101; 2. 中國科學院大學, 北京 100049; 3. 中國科學院西北高原生物研究所, 西寧 810001; 4. 中國科學院沈陽應用生態(tài)研究所, 沈陽 110016; 5. 中國科學院華南植物園, 廣州 510650)
生態(tài)系統(tǒng)呼吸是陸地生態(tài)系統(tǒng)碳收支的重要組成部分,分析其組分間的相互關系對理解生態(tài)系統(tǒng)呼吸過程和精確評價生態(tài)系統(tǒng)碳收支具有重要意義,也是當前碳循環(huán)研究工作的一大難點。利用ChinaFLUX的長白山溫帶針闊混交林(CBS),鼎湖山亞熱帶常綠闊葉林(DHS)和海北灌叢草甸(HBGC)3個典型生態(tài)系統(tǒng)的通量觀測數(shù)據(jù),分析了經驗統(tǒng)計方法在中國典型生態(tài)系統(tǒng)中的適用性及敏感性,揭示了生態(tài)系統(tǒng)呼吸各組分的動態(tài)變化特征及相互關系。結果表明:采用呼吸組分拆分方法所獲結果與理論推測及實測數(shù)據(jù)大致相同,拆分結果對凈初級生產力與總初級生產力比值(NPP/GPP)的變化較為敏感,NPP/GPP變化0.1時,自養(yǎng)呼吸在生態(tài)系統(tǒng)呼吸中的比例(Ra/RE)改變0.05。各生態(tài)系統(tǒng)中,生態(tài)系統(tǒng)呼吸及其組分在年內均表現(xiàn)出明顯的單峰型變化特征,在夏季生長旺盛的時節(jié)達到最大值。異養(yǎng)呼吸與生態(tài)系統(tǒng)呼吸的比值(Rh/RE)也具有明顯的季節(jié)變化,但在生態(tài)系統(tǒng)間表現(xiàn)出明顯差異,CBS和HBGC分別表現(xiàn)出先增大后減小和先減小后增大的變化趨勢,DHS則相對穩(wěn)定,在0.5附近波動, Ra/RE的季節(jié)動態(tài)與Rh/RE相反。在年總量上,HBGC主要通過異養(yǎng)呼吸向大氣排放CO2,異養(yǎng)呼吸占生態(tài)系統(tǒng)呼吸的60%,而CBS和DHS的自養(yǎng)呼吸和異養(yǎng)呼吸所占比重大致相似,異養(yǎng)呼吸占生態(tài)系統(tǒng)呼吸的49%。這說明,經驗統(tǒng)計學模型可以用來進行生態(tài)系統(tǒng)呼吸組分的拆分,進而可以為生態(tài)系統(tǒng)碳循環(huán)過程的精細研究提供參考數(shù)據(jù),但今后應加強NPP/GPP的測定,以提高生態(tài)系統(tǒng)呼吸拆分的精度。
陸地生態(tài)系統(tǒng);生態(tài)系統(tǒng)呼吸;渦度相關;碳通量;自養(yǎng)呼吸;異養(yǎng)呼吸
生態(tài)系統(tǒng)呼吸(RE)是碳循環(huán)的重要分量[1],與氣候變化間存在著正反饋效應[2- 3],不僅在當前全球碳收支中占有較大的比重,而且在未來還會呈現(xiàn)不斷增大的趨勢[4]。已有研究表明,全球的RE約為103 PgC a-1[5],占全球總初級生產力(GPP)總量(123 PgC a-1[6])的83.74%。
按照呼吸底物的不同,RE可分為自養(yǎng)呼吸(Ra)和異養(yǎng)呼吸(Rh)。其中,Ra是植物維持自身生命活動所必需的新陳代謝過程,又分為維持呼吸和生長呼吸。維持呼吸與溫度相關,隨著溫度的增加呈指數(shù)增加[7];生長呼吸與溫度沒有直接關系,但與GPP呈一定的比例[8]。Rh是殘存有機質分解并向大氣釋放CO2的過程[9],主要受土壤溫濕度和有機質含量的影響[10]。因而,影響RE組分的因素存在差異,拆分RE的各個組分、分析各組分間的相互關系有助于深入認識生態(tài)系統(tǒng)碳循環(huán)的過程機理,也可為陸地生態(tài)系統(tǒng)碳收支的精確評估提供理論依據(jù)。同時,Ra的變化對大氣CO2濃度具有重要影響[11],科學界迫切需要拆分和評估RE的各組分,為評價Ra對大氣CO2濃度變化的貢獻提供數(shù)據(jù)。
目前,拆分RE組分的方法有許多種。第1種是將箱式法與渦度相關系統(tǒng)觀測相結合,分別獲取土壤呼吸(Rs)和RE,實現(xiàn)RE組分的拆分[12- 14]。然而,基于箱式法獲取的Rs包含了Ra和Rh,對Rs進行拆分也是一項艱巨的工作。第2種是利用生物量調查法獲取生態(tài)系統(tǒng)凈初級生產力(NPP),結合渦度相關觀測結果估算Ra和Rh[15- 17],但生物量調查和渦度相關觀測的時間尺度不一致,并且生物量調查法耗費大量的人力物力,難以獲得持續(xù)的、高質量觀測數(shù)據(jù)。第3種是基于過程機理模型模擬Ra和Rh,但該方法所需參數(shù)較多,結果也受到模型設計者對RE過程理解程度的限制[10]。基于同位素分餾比也可以實現(xiàn)對RE組分的拆分[18- 19],但所需儀器設備非常昂貴。Schwalm等[20]提出了基于通量觀測數(shù)據(jù)的統(tǒng)計學拆分方法,并對其不確定性進行了分析。結果表明,該方法具有很好的穩(wěn)定性,不同參數(shù)方案間沒有明顯差異,這為利用通量觀測數(shù)據(jù)分析RE組分提供了新的技術途徑。
中國陸地生態(tài)系統(tǒng)通量觀測網(wǎng)絡(ChinaFLUX)自2002年建立以來,已積累了大量的觀測數(shù)據(jù),構建了學術界普遍認可的通量數(shù)據(jù)處理流程[21]。然而,現(xiàn)有通量數(shù)據(jù)處理僅將生態(tài)系統(tǒng)碳通量分解為GPP和RE,尚沒有拆分RE的組分。因此,本研究利用Schwalm等[20]分析方法,拆分并評價我國典型森林和草地生態(tài)系統(tǒng)的RE組分及其相互關系,進而闡明:(1)不同生態(tài)系統(tǒng)Ra和Rh的動態(tài)特征,(2)Rh/RE的年內動態(tài)變化特征,(3)不同生態(tài)系統(tǒng)間Ra和Rh年總量的差異。該研究可以為生態(tài)系統(tǒng)碳循環(huán)過程研究提供基礎數(shù)據(jù),也為通量數(shù)據(jù)處理過程中RE拆分方法的確定提供依據(jù)。
1.1 站點介紹
本研究選擇ChinaFLUX中3個陸地生態(tài)系統(tǒng)為研究對象,分別為:長白山溫帶針闊混交林(CBS)、鼎湖山亞熱帶常綠闊葉林(DHS)和海北高寒灌叢草甸(HBGC),各生態(tài)系統(tǒng)的基本信息如表1所示。
表1 研究站點基本信息
CBS:長白山溫帶針闊混交林Changbai Mountains temperate conifer and broadleaf mixed forest;HBGC:海北灌叢草甸Haibei alpine Shrub;DHS:鼎湖山亞熱帶常綠闊葉林Dinghu Mountains subtropical evergreen broadleaf forest
3個生態(tài)系統(tǒng)均利用開路式渦度相關系統(tǒng)(OPEC)進行生態(tài)系統(tǒng)碳水通量觀測,原始采樣頻率為10 Hz,通過數(shù)據(jù)采集器計算并儲存30 min的通量數(shù)據(jù)。同時觀測溫度、濕度、降水、輻射等氣象要素并計算30 min平均值儲存[21- 24]。此外,輔以靜態(tài)箱-氣相色譜法測定土壤呼吸,每隔7—10 d測定1次[25- 27]。
1.2 數(shù)據(jù)處理
1.2.1 通量數(shù)據(jù)處理
采用ChinaFLUX通用數(shù)據(jù)處理流程對30 min通量數(shù)據(jù)進行處理[21],包括三次坐標旋轉、WPL校正、儲存項計算及降水剔除、閾值剔除和方差剔除等,并根據(jù)Reichstein等[28]的方法確定夜間u*臨界值、實現(xiàn)夜間數(shù)據(jù)剔除、完成數(shù)據(jù)質量控制。利用非線性回歸方法對碳通量數(shù)據(jù)進行插補,并將碳通量拆分為GPP和RE。
1.2.2 自養(yǎng)呼吸和異養(yǎng)呼吸的拆分
本研究根據(jù)自養(yǎng)呼吸與生態(tài)系統(tǒng)呼吸的比值(Ra/RE)對RE進行拆分[20]。具體做法為:假設凈生態(tài)系統(tǒng)生產力(NEP)與RE的比值為θ,Ra/RE為β,則:
(1)
因而,根據(jù)式(1)可以得到β,即:
(2)
已有研究表明,NPP/GPP介于0.47—0.60之間[20],因而,β的范圍可以表示為:
(3)
在生態(tài)學研究中,Schwalm等[20]將Ra/RE或Rh/RE的最小值Ω設為0.10,并分析了Ω上下浮動0.05后的結果,他發(fā)現(xiàn)基于不同Ω得到的β沒有明顯差異,因而此處Ω設為0.10。
當β取最小值(0.10)時,θ=-0.75;當β取最大值(0.90)即Rh/RE取最小值(0.10)時,θ=0.70。因而,θlt;-0.75或者θgt;0.70時,公式(3)不再適用。當θ=-0.75時,βlower為0.10,βupper為0.13;當θ=0.70時,βlower為0.68,βupper為0.90。針對不同的θ值,設定不同的β范圍,具體范圍如表2所示。
表2 不同θ值下的β范圍
根據(jù)θ值,在β給定的范圍內隨機選取1000個數(shù)據(jù),取其平均值為β。夜間時,θ=-1,利用公式(3)無法獲取β值,因而將當日白天最后一個有效的β和次日最早一個有效的β進行線性內插的方法獲取夜間β。
最后,根據(jù)β值和RE計算Ra和Rh,即:
Ra=β×RE
Rh=(1-β)×RE
(4)
1.3 生態(tài)系統(tǒng)呼吸拆分結果的驗證
為了驗證該方法的合理性,利用靜態(tài)箱-氣相色譜法觀測的土壤呼吸(Rs)數(shù)據(jù)與本研究獲取的Rh進行對比。由于靜態(tài)箱-氣相色譜法的觀測時間是9:00—11:00,因此,Rh選用9:00—11:30的平均值。
1.4 數(shù)據(jù)統(tǒng)計
采用單因素方差分析法評價不同生態(tài)系統(tǒng)間RE組分的差異,采用線性回歸分析拆分結果與靜態(tài)箱-氣相色譜法所獲結果的差異。所有數(shù)據(jù)統(tǒng)計分析過程均在matlab7.7中進行。
2.1 生態(tài)系統(tǒng)呼吸及其組分的季節(jié)動態(tài)
生態(tài)系統(tǒng)碳通量具有明顯的季節(jié)變化特征[29- 31]。由于年際間生態(tài)系統(tǒng)的季節(jié)動態(tài)特征相似[32- 34],本文以2003年數(shù)據(jù)為例分析中國典型森林和草地生態(tài)系統(tǒng)碳通量的季節(jié)動態(tài)(圖1)。
圖1 2003年典型生態(tài)系統(tǒng)氣溫及碳通量的季節(jié)變化特征Fig.1 Seasonal dynamics of air temperature and carbon fluxes in typical ecosystems in 2003
氣溫(Ta)在3個典型生態(tài)系統(tǒng)均表現(xiàn)出單峰型變化(圖1),最大值出現(xiàn)在7月份前后,但不同生態(tài)系統(tǒng),其年內氣溫的變化幅度存在明顯差異,DHS常年保持較高的氣溫,北方兩個生態(tài)系統(tǒng)(CBS和HBGC)年內氣溫變幅較大。不同生態(tài)系統(tǒng),GPP的季節(jié)動態(tài)有所差異(圖1),北方生態(tài)系統(tǒng)(CBS和HBGC)表現(xiàn)出明顯的單峰型特點,但DHS的GPP在秋冬季節(jié)較高,在6—8月因溫度過高而略低,這與已有結果[23]相一致。NEP的季節(jié)動態(tài)與GPP相似(圖1),但峰值出現(xiàn)時間較GPP略有提前。
3個生態(tài)系統(tǒng)的RE均表現(xiàn)出明顯的單峰型變化,峰值均出現(xiàn)在7—8月份(圖1),與氣溫的季節(jié)動態(tài)(圖1)相似,這是因為,生態(tài)系統(tǒng)尺度上,氣溫的波動決定了RE的季節(jié)動態(tài)[35]。生態(tài)系統(tǒng)間,最大呼吸速率存在差異,CBS可以達到9.20 gC m-2d-1,DHS和HBGC明顯小于CBS,均不足4 gC m-2d-1。這主要是生產力的差異引起的,生產力與RE存在著密切的耦合關系[35- 37]。
與RE的動態(tài)特征相似,Ra和Rh也表現(xiàn)出單峰型的季節(jié)動態(tài)(圖1),峰值出現(xiàn)的時間也與RE相似,峰值大小約為RE峰值的一半。
2.2 生態(tài)系統(tǒng)呼吸組分與生態(tài)系統(tǒng)呼吸比值(Rh/RE和Ra/RE)的季節(jié)動態(tài)
異養(yǎng)呼吸與生態(tài)系統(tǒng)呼吸的比值(Rh/RE)表現(xiàn)出明顯的季節(jié)波動,但在生態(tài)系統(tǒng)間表現(xiàn)出不同的變化特征(圖2)。
Rh/RE在CBS表現(xiàn)為年初和年末略低、生長季開始和結束時略有增加的趨勢,在生長旺盛時節(jié)大致維持在0.5左右,DHS全年均在0.5附近波動。與兩個森林生態(tài)系統(tǒng)的變化趨勢不同,Rh/RE在HBGC表現(xiàn)出明顯的單峰型動態(tài),非生長季可以達到0.9,隨著生長季的開始,Rh/RE逐漸降低,并在生長旺季達到0.5左右的最小值,隨著生長季的結束,異養(yǎng)呼吸占據(jù)主導,Rh/RE又開始增大。
自養(yǎng)呼吸與生態(tài)系統(tǒng)呼吸的比值(Ra/RE)表現(xiàn)出與Rh/RE相反的季節(jié)變化趨勢。
圖2 2003年三個典型生態(tài)系統(tǒng)的生態(tài)系統(tǒng)呼吸組分在生態(tài)系統(tǒng)呼吸中所占比例(Rh/RE, Ra/RE)的季節(jié)動態(tài)特征Fig.2 Seasonal dynamics of the ratio of autotrophic respiration and heterotrophic respiration to ecosystem respiration (Ra/RE, Rh/RE) in typical ecosystems in 2003
2.3 生態(tài)系統(tǒng)呼吸及其組分的年總量
生態(tài)系統(tǒng)呼吸的組分反映了生態(tài)系統(tǒng)消耗碳量的不同途徑。中國3個典型生態(tài)系統(tǒng)的RE及其組分的年總量如表3所示。
生態(tài)系統(tǒng)間,RE、Ra和Rh均存在顯著差異,均表現(xiàn)為CBS最高,DHS居中,HBGC最低。生態(tài)系統(tǒng)間Rh/RE的差異表現(xiàn)為:兩個森林生態(tài)系統(tǒng)(CBS和DHS)間沒有明顯差別,約為0.49,但顯著小于HBGC的0.60。Ra/RE表現(xiàn)出相反的特征,即HBGC的數(shù)值為0.40,明顯小于CBS和DHS的0.51。
表3 典型生態(tài)系統(tǒng)的生態(tài)系統(tǒng)呼吸及其組分的年總量
表中數(shù)據(jù)為2003—2005年的平均值,括號內數(shù)值為2003—2005年的標準差
3.1 生態(tài)系統(tǒng)呼吸拆分結果的不確定性
本研究采用的方法是Schwalm等[20]對加拿大森林RE進行研究時提出的,目前尚沒有在其他生態(tài)系統(tǒng)中應用。但相對于其他研究方法,本方法結構簡單、可操作性強并具有一定的生態(tài)學理論基礎。
理論上來說,當NPP/GPP保持恒定的比值時,Ra/RE隨著NEP/RE的增加而增大,即隨著NEP/RE的增加,RE中的Rh組分降低,從圖2可知,Ra/RE的變化與NEP的變化有相似的規(guī)律,這證實了該方法在理論上是可行的。
在理論分析的基礎上,用靜態(tài)箱-氣相色譜法觀測的Rs與本研究中拆分得到的Rh作對比(圖3),以驗證該方法的拆分效果。
從圖3可以看出,在CBS,Rh與Rs的比值為0.34(圖3),這在之前研究結果[38- 39]的范圍內,并與東北林區(qū)其他研究[40]相似。在DHS和HBGC,Rh與Rs間沒有明顯的關系。這是因為,在CBS,利用箱式法觀測的Rs是生態(tài)系統(tǒng)呼吸的一部分(圖3),可以反映RE的動態(tài),但在DHS和HBGC,箱式法觀測到的Rs幾乎與該時段的RE相一致,這可能是由箱式法本身觀測的誤差引起的。
進一步整理了已發(fā)表文獻的NPP數(shù)據(jù),結合渦度相關觀測的碳通量結果,估算RE及其組分年總量間的相互關系。在CBS,張娜等[41]模擬發(fā)現(xiàn),1995年該生態(tài)系統(tǒng)Ra/RE高達0.82,高于本研究結果(表3),這可能是他們估算的NEP過高及NPP偏小導致的,NEP值高達392 gC m-2a-1[41],比渦度相關觀測結果[34]高54%。在DHS,2003—2004年的NPP為970 gC m-2a-1[42],結合Yu等[34]的結果可以看到,這兩年該生態(tài)系統(tǒng)的Ra/RE為52.33%,與本研究結果(表3)相似。
雖然Piao等[11]總結已有研究結果[1, 43- 44]發(fā)現(xiàn),Ra與GPP的比值雖然表現(xiàn)出隨著溫度的增加先降低后增大,但具有較大的變異性,基于本研究的方法,CBS、DHS、HBGC的Ra/GPP分別為0.40、0.31、0.35,也在Piao等[11]的范圍之內。
因而,本研究所用方法具有簡便易行、無需額外測定即可準確拆分RE,這為分析碳收支組分及其影響因素提供了可能,可以在生態(tài)系統(tǒng)碳循環(huán)研究中應用。
3.2 生態(tài)系統(tǒng)呼吸拆分結果對NPP/GPP的敏感性
本研究將NPP/GPP的值設為0.47—0.60,但Litton等[43]整理文獻數(shù)據(jù)發(fā)現(xiàn),NPP/GPP變異很大,最小甚至可能低于0.20。因而有必要進一步分析NPP/GPP的變化對RE組分拆分的影響。
此處設定兩個方案,即將NPP/GPP(θ)的上下限(0.47—0.60)分別下調0.10(方案I)和上調0.10(方案II),相應的RE/NEP(β)的臨界比值發(fā)生改變(表4)。
表4 不同處理方案下θ值下的β范圍
基于不同數(shù)據(jù)處理方案獲得了生態(tài)系統(tǒng)呼吸組分相互關系的季節(jié)動態(tài)(圖4),Ra/RE及Rh/RE的季節(jié)動態(tài)與圖2沒有明顯差異,說明不同NPP/GPP的變化不會對Ra/RE及Rh/RE的季節(jié)動態(tài)產生明顯影響。
圖4 2003年不同NPP/GPP的典型生態(tài)系統(tǒng)的生態(tài)系統(tǒng)呼吸組分在生態(tài)系統(tǒng)呼吸中所占比例(Rh/RE, Ra/RE)的季節(jié)動態(tài)特征Fig.4 Seasonal dynamics of the ratio of autotrophic respiration and heterotrophic respiration to ecosystem respiration (Ra/RE, Rh/RE) in typical ecosystems in 2003 with different NPP/GPP
不同數(shù)據(jù)處理方案下,生態(tài)系統(tǒng)呼吸組分在生態(tài)系統(tǒng)呼吸中所占的比例發(fā)生一定的波動(表5),NPP/GPP每改變0.1,Ra/RE變化0.05,Ra/RE隨著NPP/GPP的增加而降低。
表5不同數(shù)據(jù)處理方案生態(tài)系統(tǒng)呼吸組分在生態(tài)系統(tǒng)呼吸中所占比例
Table5Theratioofautotrophicrespirationandheterotrophicrespirationtoecosystemrespiration(Ra/RE, Rh/RE)underdifferentdatatreatments
處理Treatment自養(yǎng)呼吸與生態(tài)系統(tǒng)呼吸的比值Ra/RE長白山CBS鼎湖山DHS海北灌叢HBGC異養(yǎng)呼吸與生態(tài)系統(tǒng)呼吸的比值Rh/RE長白山CBS鼎湖山DHS海北灌叢HBGC本研究Thisstudy0.51(0.01)0.51(0.01)0.40(0.00)0.49(0.01)0.49(0.01)0.60(0.01)方案ⅠTreatmentⅠ0.56(0.01)0.55(0.01)0.43(0.01)0.44(0.01)0.45(0.02)0.57(0.01)方案ⅡTreatmentⅡ0.46(0.01)0.45(0.01)0.36(0.00)0.54(0.01)0.55(0.02)0.64(0.00)
表中數(shù)據(jù)為2003—2005年的平均值,括號內數(shù)值為觀測期間的標準差
生態(tài)系統(tǒng)間,不管NPP/GPP發(fā)生何種變化,HBGC的Ra/RE均小于CBS和DHS,并且該值始終小于0.5,因而HBGC的生態(tài)系統(tǒng)呼吸以異養(yǎng)呼吸為主。隨著NPP/GPP的變化,CBS和DHS中Ra/RE在0.5上下浮動,表明森林生態(tài)系統(tǒng)中自養(yǎng)和異養(yǎng)呼吸所占的比例大致相似。
可見,NPP/GPP影響著RE組分拆分,生物量調查獲取的NPP將為生態(tài)系統(tǒng)碳通量組分的拆分提供重要基礎數(shù)據(jù)。
3.3 生態(tài)系統(tǒng)呼吸各組分間的相互關系
在季節(jié)動態(tài)上,Ra/RE隨著NEP的增加有增大的趨勢[20],表明隨著植物生長的開始,生態(tài)系統(tǒng)在不斷固碳的基礎上通過自養(yǎng)呼吸向外排放的碳量也在增加。這是因為Ra中的維持呼吸與溫度相關,隨著溫度的增加呈指數(shù)增加[7];生長呼吸與溫度沒有直接關系,但與GPP呈一定的比例關系[8];而Rh受土壤溫濕度和有機質含量的影響。因此,在生長季開始后,隨著GPP和氣溫的增大,Ra增加速度快于Rh,導致Ra/RE開始增加。
生態(tài)系統(tǒng)之間,Ra年總量與RE年總量的比值也明顯不同,森林生態(tài)系統(tǒng)明顯高于草地生態(tài)系統(tǒng),表明森林生態(tài)系統(tǒng)Ra所占比例高于草地生態(tài)系統(tǒng),與Schwalm等[20]的結果相同。這是因為,森林生態(tài)系統(tǒng)具有較高的NEP,NEP/RE也較高,導致Ra/RE高。比較中國與加拿大森林生態(tài)系統(tǒng)間[20]的Ra/RE的差異可以發(fā)現(xiàn),中國森林生態(tài)系統(tǒng)的Ra/RE明顯高于加拿大森林生態(tài)系統(tǒng),這也是由中國森林生態(tài)系統(tǒng)中NEP/RE高于加拿大所決定的。
基于ChinaFLUX3個陸地生態(tài)系統(tǒng)(CBS:長白山溫帶混交林,DHS:鼎湖山亞熱帶常綠闊葉林,HBGC:海北高寒灌叢草甸)的渦度相關觀測數(shù)據(jù),利用統(tǒng)計分析方法拆分了RE組分,分析了該方法在中國陸地生態(tài)系統(tǒng)的適用性及對NPP/GPP的敏感性,闡明了RE組分的動態(tài)特征及其相互關系。結果表明:基于渦度相關觀測數(shù)據(jù)及NPP/GPP的比值,可以準確拆分中國典型生態(tài)系統(tǒng)的RE,但該方法對NPP/GPP較為敏感。3個生態(tài)系統(tǒng)中,RE及其組分年內均表現(xiàn)出單峰型的變化,在生長旺盛時節(jié)(7月份)達到最大值。異養(yǎng)呼吸在生態(tài)系統(tǒng)呼吸中所占的比例(Rh/RE)表現(xiàn)出明顯的季節(jié)變化,CBS表現(xiàn)出先增大后減小的季節(jié)特征,DHS則常年維持為0.5左右,HBGC表現(xiàn)出先降低后增大的特點。年總量上,Rh/RE因生態(tài)系統(tǒng)的不同而不同,CBS和DHS兩個森林生態(tài)系統(tǒng)的自養(yǎng)和異養(yǎng)呼吸大致相當,HBGC的碳排放則主要通過異養(yǎng)呼吸來實現(xiàn)。該方法可以拆分RE組分,進而為生態(tài)系統(tǒng)碳循環(huán)的過程研究提供參考數(shù)據(jù),但今后應加強NPP/GPP的測定,以提高生態(tài)系統(tǒng)呼吸拆分的精度。
Referrences:
[1] Luyssaert S, Inglima I, Jung M, Richardson A D, Reichsteins M, Papale D, Piao S L, Schulzes E D, Wingate L, Matteucci G, Aragao L, Aubinet M, Beers C, Bernhoffer C, Black K G, Bonal D, Bonnefond J M, Chambers J, Ciais P, Cook B, Davis K J, Dolman A J, Gielen B, Goulden M, Grace J, Granier A, Grelle A, Griffis T, Grunwald T, Guidolotti G, Hanson P J, Harding R, Hollinger D Y, Hutyra L R, Kolar P, Kruijt B, Kutsch W, Lagergren F, Laurila T, Law B E, Le Maire G, Lindroth A, Loustau D, Malhi Y, Mateus J, Migliavacca M, Misson L, Montagnani L, Moncrieff J, Moors E, Munger J W, Nikinmaa E, Ollinger S V, Pita G, Rebmann C, Roupsard O, Saigusa N, Sanz M J, Seufert G, Sierra C, Smith M L, Tang J, Valentini R, Vesala T, Janssens I A. CO2balance of boreal, temperate, and tropical forests derived from a global database. Global Change Biology, 2007, 13(12): 2509- 2537.
[2] Davidson E A, Janssens I A, Luo Y Q. On the variability of respiration in terrestrial ecosystems: moving beyond Q10. Global Change Biology, 2006, 12(2): 154- 164.
[3] Houghton R A, Davidson E A, Woodwell G M. Missing sinks, feedbacks, and understanding the role of terrestrial ecosystems in the global carbon balance. Global Biogeochemical Cycles, 1998, 12(1): 25- 34.
[4] Cox P M, Betts R A, Jones C D, Spall S A, Totterdell I J. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature, 2000, 408(6809): 184- 187.
[5] Yuan W P, Luo Y Q, Li X L, Liu S G, Yu G R, Zhou T, Bahn M, Black A, Desai A R, Cescatti A, Marcolla B, Jacobs C, Chen J Q, Aurela M, Bernhofer C, Gielen B, Bohrer G, Cook D R, Dragoni D, Dunn A L, Gianelle D, Grünwald T, Ibrom A, Leclerc M Y, Lindroth A, Liu H P, Marchesini L B, Montagnani L, Pita G, Rodeghiero M, Rodrigues A, Starr G, Stoy P C. Redefinition and global estimation of basal ecosystem respiration rate. Global Biogeochemical Cycles, 2011, 25: GB4002, doi: 10.1029/2011gb004150.
[6] Beer C, Reichstein M, Tomelleri E, Ciais P, Jung M, Carvalhais N, Rodenbeck C, Arain M A, Baldocchi D, Bonan G B, Bondeau A, Cescatti A, Lasslop G, Lindroth A, Lomas M, Luyssaert S, Margolis H, Oleson K W, Roupsard O, Veenendaal E, Viovy N, Williams C, Woodward F I, Papale D. Terrestrial gross carbon dioxide uptake: global distribution and covariation with climate. Science, 2010, 329(5993): 834- 838.
[7] Ryan M G. A simple method for estimating gross carbon budgets for vegetation in forest ecosystems. Tree Physiology, 1991, 9(1/2): 255- 266.
[8] Chen J M, Liu J, Cihlar J, Goulden M L. Daily canopy photosynthesis model through temporal and spatial scaling for remote sensing applications. Ecological Modelling, 1999, 124(2/3): 99- 119.
[9] Trumbore S. Carbon respired by terrestrial ecosystems-recent progress and challenges. Global Change Biology, 2006, 12(2): 141- 153.
[10] Yu G R. Scientific Frontier on Human Activities and Ecosystem Changes. Beijing: Higher Education Press, 2009.
[11] Piao S L, Luyssaert S, Ciais P, Janssens I A, Chen A P, Cao C, Fang J Y, Friedlingstein P, Luo Y Q, Wang S P. Forest annual carbon cost: a global-scale analysis of autotrophic respiration. Ecology, 2010, 91(3): 652- 661.
[12] Irvine J, Law B E, Martin J G, Vickers D. Interannual variation in soil CO2efflux and the response of root respiration to climate and canopy gas exchange in mature ponderosa pine. Global Change Biology, 2008, 14(12): 2848- 2859.
[13] Nagy Z, Pintér K, Pavelka M, Darenová E, Balogh J. Carbon fluxes of surfaces vs. ecosystems: advantages of measuring eddy covariance and soil respiration simultaneously in dry grassland ecosystems. Biogeosciences, 2011, 8(9): 2523- 2534.
[14] Griffis T J, Black T A, Gaumont-Guay D, Drewitt G B, Nesic Z, Barr A G, Morgenstern K, Kljun N. Seasonal variation and partitioning of ecosystem respiration in a southern boreal aspen forest. Agricultural and Forest Meteorology, 2004, 125(3/4): 207- 223.
[15] Law B E, Thornton P E, Irvine J, Anthoni P M, Van Tuyl S. Carbon storage and fluxes in ponderosa pine forests at different developmental stages. Global Change Biology, 2001, 7(7): 755- 777.
[16] Luyssaert S, Reichstein M, Schulze E D, Janssens I A, Law B E, Papale D, Dragoni D, Goulden M L, Granier A, Kutsch W L, Linder S, Matteucci G, Moors E, Munger J W, Pilegaard K, Saunders M, Falge E M. Toward a consistency cross-check of eddy covariance flux-based and biometric estimates of ecosystem carbon balance. Global Biogeochemical Cycles, 2009, 23: GB3009, doi: 10.1029/2008gb003377.
[17] Tan Z H, Zhang Y P, Yu G R, Sha L Q, Tang J W, Deng X B, Song Q H. Carbon balance of a primary tropical seasonal rain forest. Journal of Geophysical Research, 2010, 115: D00H26, doi: 10.1029/2009jd012913.
[18] Riveros-Iregui D A, Hu J, Burns S P, Bowling D R, Monson R K. An interannual assessment of the relationship between the stable carbon isotopic composition of ecosystem respiration and climate in a high-elevation subalpine forest. Journal of Geophysical Research, 2011, 116: G02005, doi: 10.1029/2010jg001556.
[19] Schuur E A G, Trumbore S E. Partitioning sources of soil respiration in boreal black spruce forest using radiocarbon. Global Change Biology, 2006, 12(2): 165- 176.
[20] Schwalm C R, Black T A, Morgenstern K, Humphreys E R. A method for deriving net primary productivity and component respiratory fluxes from tower-based eddy covariance data: a case study using a 17-year data record from a Douglas-fir chronosequence. Global Change Biology, 2007, 13(2): 370- 385.
[21] Yu G R, Fu Y L, Sun X M, Wen X F, Zhang L M. Recent progress and future directions of ChinaFLUX. Science in China Series D: Earth Sciences, 2006, 49(Suppl II): 1- 23.
[22] Zhang J H, Yu G R, Han S J, Guan D X, Sun X M. Seasonal and annual variation of CO2flux above a broad-leaved Korean pine mixed forest. Science in China Series D: Earth Sciences, 2006, 49(Suppl II): 63- 73.
[23] Wang C L, Yu G R, Zhou G Y, Yan J H, Zhang L M, Wang X, Tang X L, Sun X M. CO2flux evaluation over the evergreen coniferous and broad-leaved mixed forest in Dinghushan, China. Science in China Series D: Earth Sciences, 2006, 49(Suppl II): 127- 138.
[24] Li Y N, Sun X M, Zhao X Q, Zhao L, Xu S X, Gu S, Zhang G F, Yu G R. Seasonal variations and mechanism for environmental control of NEE of CO2concerning thePotentillafruticosain alpine shrub meadow of Qinghai-Tibet Plateau. Science in China Series D: Earth Sciences, 2006, 49(Suppl II): 174- 185.
[25] Zheng Z M, Yu G R, Sun X M, Cao G M, Wang Y S, Du M Y, Li J, Li Y N. Comparison of eddy covariance and static chamber/gas chromatogram methods in measuring ecosystem respiration. Chinese Journal of Applied Ecology, 2008, 19(2): 290- 298.
[26] Lin L S, Han S J, Wang Y S, Gu Z J. Soil CO2flux in several typical forests of Mt. Changbai. Chinese Journal of Ecology, 2004, 23(5): 42- 45.
[27] Zhang D Q, Sun X M, Zhou G Y, Yan J H, Wang Y S, Liu S Z, Zhou C Y, Liu J X, Tang X L, Li J, Zhang Q M. Seasonal dynamics of soil CO2effluxes with responses to environmental factors in lower subtropical forests of China. Science in China Series D: Earth Sciences, 2006, 49(Suppl II): 139- 149.
[28] Reichstein M, Falge E, Baldocchi D, Papale D, Aubinet M, Berbigier P, Bernhofer C, Buchmann N, Gilmanov T, Granier A, Grunwald T, Havrankova K, Ilvesniemi H, Janous D, Knohl A, Laurila T, Lohila A, Loustau D, Matteucci G, Meyers T, Miglietta F, Ourcival J M, Pumpanen J, Rambal S, Rotenberg E, Sanz M, Tenhunen J, Seufert G, Vaccari F, Vesala T, Yakir D, Valentini R. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology, 2005, 11(9): 1424- 1439.
[29] Law B E, Williams M, Anthoni P M, Baldocchi D D, Unsworth M H. Measuring and modelling seasonal variation of carbon dioxide and water vapour exchange of aPinusponderosaforest subject to soil water deficit. Global Change Biology, 2000, 6(6): 613- 630.
[30] Valentini R, Gamon J A, Field C B. Ecosystem ags-exchange in a California grassland-seasonal patterns and implications for scaling. Ecology, 1995, 76(6): 1940- 1952.
[31] Guan D X, Wu J B, Zhao X S, Han S J, Yu G R, Sun X M, Jin C J. CO2fluxes over an old, temperate mixed forest in northeastern China. Agricultural and Forest Meteorology, 2006, 137(3/4): 138- 149.
[32] Barr A G, Black T A, Hogg E H, Griffis T J, Morgenstern K, Kljun N, Theede A, Nesic Z. Climatic controls on the carbon and water balances of a boreal aspen forest, 1994—2003. Global Change Biology, 2007, 13(3): 561- 576.
[33] Polley H W, Frank A B, Sanabria J, Phillips R L. Interannual variability in carbon dioxide fluxes and flux-climate relationships on grazed and ungrazed northern mixed-grass prairie. Global Change Biology, 2008, 14(7): 1620- 1632.
[34] Yu G R, Zhang L M, Sun X M, Fu Y L, Wen X F, Wang Q F, Li S G, Ren C Y, Song X, Liu Y F, Han S J, Yan J H. Environmental controls over carbon exchange of three forest ecosystems in eastern China. Global Change Biology, 2008, 14(11): 2555- 2571.
[35] Wen X F, Wang H M, Wang J L, Yu G R, Sun X M. Ecosystem carbon exchanges of a subtropical evergreen coniferous plantation subjected to seasonal drought, 2003—2007. Biogeosciences, 2010, 7(1): 357- 369.
[36] Wang X C, Wang C K, Yu G R. Spatio-temporal patterns of forest carbon dioxide exchange based on global eddy covariance measurements. Science in China Series D: Earth Sciences, 2008, 51(8): 1129- 1143.
[37] Lasslop G, Reichstein M, Detto M, Richardson A D, Baldocchi D D. Comment on Vickers et al.: self-correlation between assimilation and respiration resulting from flux partitioning of eddy-covariance CO2fluxes. Agricultural and Forest Meteorology, 2010, 150(2): 312- 314.
[38] Subke J A, Inglima I, Francesca Cotrufo M. Trends and methodological impacts in soil CO2efflux partitioning: a metaanalytical review. Global Change Biology, 2006, 12(6): 921- 943.
[39] Zhan X Y, Yu G R, Zheng Z M, Wang Q F. Carbon emission and spatial pattern of soil respiration of terrestrial ecosystems in China: based on geostatistic estimation of flux measurement. Progress in Geography, 2012, 31(1): 97- 108.
[40] Wang C K, Yang J Y. Rhizospheric and heterotrophic components of soil respiration in six Chinese temperate forests. Global Change Biology, 2007, 13(1): 123- 131.
[41] Zhang N, Yu G R, Zhao S D, Yu Z L. Carbon budget of ecosystem in Changbai Mountain natural reserve. Environmental Science, 2003, 24(1): 24- 32.
[42] Yan J H, Wang Y P, Zhou G Y, Zhang D Q. Estimates of soil respiration and net primary production of three forests at different succession stages in South China. Global Change Biology, 2006, 12(5): 810- 821.
[43] Litton C M, Raich J W, Ryan M G. Carbon allocation in forest ecosystems. Global Change Biology, 2007, 13(10): 2089- 2109.
[44] DeLucia E H, Drake J E, Thomas R B, Gonzalez-Meler M. Forest carbon use efficiency: is respiration a constant fraction of gross primary production?. Global Change Biology, 2007, 13(6): 1157- 1167.
[10] 于貴瑞. 人類活動與生態(tài)系統(tǒng)變化的前沿科學問題. 北京: 高等教育出版社, 2009.
[25] 鄭澤梅, 于貴瑞, 孫曉敏, 曹廣民, 王躍思, 杜明遠, 李俊, 李英年. 渦度相關法和靜態(tài)箱/氣相色譜法在生態(tài)系統(tǒng)呼吸觀測中的比較. 應用生態(tài)學報, 2008, 19(2): 290- 298.
[26] 林麗莎, 韓士杰, 王躍思, 谷志靜. 長白山四種林分土壤CO2釋放通量的研究. 生態(tài)學雜志, 2004, 23(5): 42- 45.
[39] 展小云, 于貴瑞, 鄭澤梅, 王秋鳳. 中國區(qū)域陸地生態(tài)系統(tǒng)土壤呼吸的碳排放及空間格局——基于通量觀測的地學統(tǒng)計評估. 地理科學進展, 2012, 31(1): 97- 108.
[41] 張娜, 于貴瑞, 趙士洞, 于振良. 長白山自然保護區(qū)生態(tài)系統(tǒng)碳平衡研究. 環(huán)境科學, 2003, 24(1): 24- 32.
Theinteractionbetweencomponentsofecosystemrespirationintypicalforestandgrasslandecosystems
ZHU Xianjin1,2, YU Guirui1, *, WANG Qiufeng1, GAO Yanni1,2, ZHAO Xinquan3, HAN Shijie4, YAN Junhua5
1SynthesisResearchCenterofCERN,KeyLaboratoryofEcosystemNetworkObservationandModeling,InstituteofGeographicSciencesandNaturalResourcesResearch,ChineseAcademyofSciences,Beijing100101,China2UniversityofChineseAcademyofSciences,Beijing100049,China3NorthwestPlateauInstituteofBiology,ChineseAcademyofSciences,Xining810001,China4InstituteofAppliedEcology,ChineseAcademyofSciences,Shenyang110016,China5SouthChinaBotanicalGarden,ChineseAcademyofSciences,Guangzhou510650,China
Ecosystem respiration (RE), the release of carbon from an ecosystem into the atmosphere, is a key component of the terrestrial ecosystem carbon budget and plays an important role in the global carbon balance. Analyzing the interaction between RE components is essential to understand RE and to accurately evaluate the ecosystem carbon budget. There are many methods for separating RE into autotrophic respiration (Ra) and heterotrophic respiration (Rh), but each approach has disadvantages. Large RE data have obtained through long-term eddy covariance measurements, while the interaction between Ra and Rh is poorly documented, which inhibits the accurate assessment of global carbon budget. In this study, we used an empirical statistical method to separate RE into its two components and to examine component relationships and seasonal dynamics at three ChinaFLUX sites: 1) Changbaishan temperate mixed forest (CBS); 2) Dinghushan subtropical evergreen broad-leaf forest (DHS); and 3) Haibei shrub meadow (HBGC). The applicability and sensitivity of this method in typical ecosystems of China were also evaluated. The method used in this study was based on the ratio of Ra to RE (Ra/RE). The range of Ra/RE was obtained by calculating two ratios: the ratio of RE to net ecosystem productivity (NEP) (RE/NEP) and that of net primary productivity (NPP) to gross primary productivity (GPP) (NPP/GPP). Within the range of Ra/RE, 1000 Ra/REs were randomly selected and the value of Ra/RE used in this study was set as the mean of the 1000 random Ra/REs. Ra and Rh were then calculated using Ra/RE and RE.
Our study showed that the RE separating method produced consistent results with those obtained through static chamber/gas chromatographic techniques at the same sites, as well as with biomass surveys and theoretical speculation. The interaction of RE components was sensitive to the variation of NPP/GPP: a ten-percent increase of NPP/GPP led to a five-percent decrease of Ra/RE. In all three ecosystems, RE and its components showed similar seasonal dynamics, with a single-peak pattern achieving its maximum midway through the growing season. The ratio of Rh to RE (Rh/RE) also showed different seasonal dynamic among the three ecosystems. In CBS, Rh/RE increased during the first half of the year, reached its peak during the growing season then decreased. However, Rh/RE in HBGC decreased during the first half of the year and increased again later in growing-season. In DHS, Rh/RE was relatively stable at approximately 0.5. Seasonal dynamics of Ra/RE were opposite to those in Rh/RE. The annual total Rh accounted for 60% of the RE in HBGC, suggesting that a large proportion of emitted carbon was released by Rh in this ecosystem. In CBS and DHS, Rh was only 49% of RE, indicating that the release of carbon through Ra and Rh was nearly the same in these two forest ecosystems. Results indicate that this statistical method, which requires detailed observations of NPP/GPP, can successfully separate RE into Rh and Ra and can provide necessary data for the detailed analysis of the ecosystem carbon cycle.
terrestrial ecosystem; ecosystem respiration; eddy covariance; carbon fluxes; autotrophic respiration; heterotrophic respiration
國家重點基礎研究發(fā)展規(guī)劃資助項目(2010CB833504); 國家自然科學基金資助項目(31061140359, 30590380); 中國科學院戰(zhàn)略性先導科技專項資助項目(XDA05050601)
2012- 07- 13;
2013- 06- 21
*通訊作者Corresponding author.E-mail: yugr@igsnrr.ac.cn
10.5846/stxb201207130988
朱先進,于貴瑞,王秋鳳,高艷妮,趙新全,韓士杰,閆俊華.典型森林和草地生態(tài)系統(tǒng)呼吸各組分間的相互關系.生態(tài)學報,2013,33(21):6925- 6934.
Zhu X J, Yu G R, Wang Q F, Gao Y N, Zhao X Q, Han S J, Yan J H.The interaction between components of ecosystem respiration in typical forest and grassland ecosystems.Acta Ecologica Sinica,2013,33(21):6925- 6934.