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N來(lái)為維持其生長(zhǎng)活動(dòng),因此其分解往往滯后[17]。凋落物分解過(guò)程中,某些材料可在數(shù)年后才可觀(guān)察到氮的釋放,而前期總有氮量的凈增加,氮積累階段約為2 年或失重率達(dá)50%的時(shí)間[17]。因此,對(duì)土壤N2O釋放的觀(guān)測(cè)應(yīng)該考慮其植被凋落物特性,如果測(cè)定時(shí)間過(guò)短,可能對(duì)地表N2O通量估計(jì)帶來(lái)很大的誤差。圖1 針葉林和果園土壤N2O通量日變化Fig. 1 Diurnal variations of N2O flux in pine plantation and orchardBS: Bare soil. SL: Soil with litter3 結(jié)論(1)針葉林和果園土壤為大氣N2O的源。地表N2O通量日變化規(guī)律不明顯,日變化中最大通量和最小通量出現(xiàn)的時(shí)間也沒(méi)有明顯的規(guī)律。(2)溫度對(duì)地表N2O通量日變化無(wú)明顯影響。降雨對(duì)地表N2O通量有較大的影響,雨季地表N2O通量大于旱季。(3)不同土地利用方式對(duì)地表N2O通量有較大影響,果園地表N2O通量較針葉林大。總的來(lái)看,沒(méi)有發(fā)現(xiàn)凋落物對(duì)地表N2O通量有明顯影響,可能凋落物對(duì)地表N2O的釋放具有滯后效應(yīng),原因有待進(jìn)一步探討。致謝:鶴山站林永標(biāo)和饒興權(quán)等老師及其他同學(xué)對(duì)本實(shí)驗(yàn)給予了很大的幫助,特此致謝!參考文獻(xiàn):[1] Houghton J T, Ding Y, Griggs D J, et al. IPCC. Climate Change 2001: The Scientific Basis: Contribution of Working GroupⅠto the Third Assessment Report of the International Panel on Climate Change[M]. Cambridge, UK: Cambridge University Press, 2001.[2] BOUWNAN A F. Soils and the Greenhouse Effect[M]. Chichester: John Wiley and Sons, 1990.[3] HOUGHTON J T, CALLANDERr B A, VARNEY S K. IPCC. Climate Change 1992: Greenhouse gases and aerosols: The Supplementary Report to the IPCC Scientific Assessment [M]. Cambridge, UK: Cambridge University Press, 1992.[4] 申衛(wèi)軍, 彭少麟, 周?chē)?guó)逸, 等. 馬占相思(Acacia mangium ) 與濕地松(Pinus elliotii) 人工林枯落物層的水文生態(tài)功能[J]. 生態(tài)學(xué)報(bào), 2001, 21(5):846850.Shen Weijun, Peng Shaolin, Zhou , et al. Ecohydrological functions of litter in manmade Acacia Mangium and Pinus elliotii plantations[J]. Acat Ecologica Sinica, 2001, 21(5): 846850.[5] 趙平, 曾小平, 彭少麟. 南亞熱帶丘陵區(qū)龍眼和象草的葉片氣孔氣體交換的研究[J]. 廣西植物, 2001, 21(1):8186. Zhao Ping, Zeng Xiaoping, Peng Shaolin. Stomatal gas exchange in leaves of Dimocarpus longan and Pennisetum pur pureum in southern subtropical hilly land[J]. Guihaia, 2001, 21(1):8186. [6] 劉惠, 趙平. 華南丘陵區(qū)典型土地利用類(lèi)型土壤呼吸日變化[J]. 生態(tài)環(huán)境, 2008(1): 249255.Liu Hui, Zhao Ping. Diurnal variations of soil respiration of typical landuse types in a Hilly Area of South China[J]. Ecology and Environment, 2008(