【作者】 徐侠；

【导师】 阮宏华；

【作者基本信息】 南京林业大学 ， 生态学， 2008， 硕士

【摘要】 在全球碳循环研究当中,土壤碳的变化是最复杂、最具不确定性的部分。由于土壤-大气之间CO₂的流量巨大,土壤碳库的微小变化可能显著影响到大气中CO₂浓度的变化,并进一步影响全球气候变化。而活性有机碳是土壤中最具有活性的那部分土壤碳,虽然它只占土壤有机碳总量的较小部分,但其周转非常迅速,可以在土壤全碳变化之前反映土壤微小的变化、直接参与土壤生物化学转化过程,因而对土壤碳库的平衡具有重要意义。因此,对山地土壤活性有机碳的研究除了揭示区域森林土壤碳循环规律外,并可推及于森林水平地带性土壤的碳循环,为准确预测未来全球气候变化趋势提供依据和数据。空间变异对生态系统过程的影响是目前生态学研究中的重要主题之一,山地区域海拔梯度的变化为研究生态系统过程的空间异质性提供了良好条件。本研究试验地选在福建省武夷山国家自然保护区,该区年均气温12-18℃,年均相对湿度82%-85%,年均雾日100 d以上,年均降水量2000 mm左右。典型的地带性森林类型为常绿阔叶林群落,植被垂直带谱分布完整,自然资源丰富。沿海拔依次分布有常绿阔叶林（EBF）、针叶林（CF）、亚高山矮林（SDF）以及高山草甸（AM）。为了阐明土壤活性有机碳时空变化的机理及其与主要影响因子的关系,进一步揭示不同海拔土壤碳动态及其对未来全球气候变化的响应,在以上4个植物群落内随机布置样地,从2006年4月到2007年1月,测定了土壤有效碳（MAC）、微生物量碳（MBC）、易氧化碳（ROC）、水溶性有机碳（WSOC）及其影响因子,如土壤总有机碳、总氮、凋落物量、细根生物量、土壤温、湿度等。结果表明:有效碳、微生物量碳、易氧化碳和水溶性有机碳四种活性有机碳在各样地及土层的空间变化趋势均为:随高度的上升而增加,随土层的加深而减小。高山草甸土壤中的活性有机碳显著高于其他三个林分。有效碳的周转速率K值表明:有效碳的分解速度随着海拔的上升和土层的加深而下降。有效碳等四种活性有机碳和土壤总有机碳、总氮、细根生物量、凋落物量、土壤湿度间达到显著或极显著的正相关:与土壤温度、土壤呼吸间达到显著或极显著的负相关;此外,水溶性有机碳和土壤全硫显著正相关,与pH值显著负相关。有效碳等四种活性有机碳两两间的相关性均达到极显著的正相关,其中有效碳和微生物量碳的相关性最好,R²达到0.942。各活性有机碳占土壤全碳的比例从大到小依次为:ROC＞MAC＞MBC＞WSOC。有效碳和微生物量碳的季节动态为:夏季＞春季＞秋季＞冬季。土壤湿度的季节变化对有效碳和微生物量碳的季节变化有很大的影响,相关性达到极显著水平;而土壤温度对有效碳有显著影响,对微生物量碳的影响不显著。细根生物量和凋落物量的季节变化对有效碳和微生物量的季节变化影响不显著。但在一个季节中,细根生物量和凋落物量是以上四种活性有机碳的重要影响因子,相关性显著。土壤活性有机碳的分解是一个复杂的生物学过程,时空变异大,受多种因素的影响。由于土壤有效碳还没有统一的定义和测定方法,如何评价目前所测定的土壤有效碳含量特征在生态系统碳循环或区域碳平衡中的作用和意义还有待于进一步研究。更多还原

【Abstract】 In global carbon cycling,the variation of soil carbon is the most complex and uncertain part.The slight changes in soil carbon pool may greatly affect the concentration of CO₂ in the atmosphere because of the huge flux between soil and atmosphere.Though soil labile organic carbon only takes up a small portion of organic carbon,it is the most active fraction with rapid turnover rate,which could pre-indicate the slight variations of the soil than the total organic carbon could,it also directly participate in soil biochemical processes.Thus,it greatly affects the balancing of carbon cycling.Therefore,study on the content and distribution of labile organic carbon at mountainous area is of great importance in indicating the discipline of soil carbon cycling of a certain region and forecasting the trend of global climate change.The effect of spatial variations to the processes in ecosystems is one of the major topics of ecological study at present,and the variations along the elevation in mountainous area provide good conditions to study the spatial heterogeneity of ecosystems.Thus,the experimental sites were set in the Wuyi Mountain National Reserve Area,where annually average temperature,relative humidity,fog days, precipitation,are 12-18℃,82%-85%,more than 100 days,and about 2000 millimeters,respectively.The typically regional forest is evergreen broad-leaf forest and the natural resources are very rich.The forest types along the elevation gradient are:evergreen broad-leaf forest（EBF）,coniferous forest（CF）,sub-alpine dwarf forest（SDF）,alpine meadow（AM）,respectively.Experimental sites were randomly set in the four vegetation communities in order to examine the temporal and spatial variations of soil labile organic carbon（SLOC）and its main regulating factors,so as to indicate the response of soil carbon along the elevation gradient to global climate change.From April 2006 to January 2007,microbially available carbon（MAC）,microbial biomass carbon（MBC）,readily oxidation carbon（ROC）, water-soluble organic carbon（WSOC）together with several regulating factors,such as total organic carbon（TOC）,total nitrogen（TN）,litterfall biomass（LFB）,fine root biomass（FRB）,soil temperature and moisture were measured.The results indicated that:Spatial variations of MAC,MBC,ROC,WSOC increased with the elevation gradient,and decreased with the soil layer.The amount of labile organic carbon in AM was significantly greater than those in the other three communities.The turnover rate（κ）of MAC indicated that the decomposition speed of MAC decreased with the elevation gradient and the soil layer.Soil labile organic carbon（MAC,MBC,ROC,WSOC）correlated positively with total organic carbon,total nitrogen,FRB,LFB,soil moisture,and negatively with soil temperature and moisture,soil respiration.Moreover,WSOC correlated positively with total sulfur,and negatively with pH value.The four kinds of labile carbon correlated positively with each other,and the best correlation was between MAC and MBC（R²=0.942）.The ratio order of the four kinds of labile carbon to TOC was:ROC＞MAC＞MBC＞WSOC.Seasonal variations of MAC and MBC were:summer＞spring＞fall＞winter.The variations of MAC and MBC were significantly affected by seasonal variations of soil moisture;soil temperature greatly affected MAC but not MBC.The variations of MAC and MBC were not apparently influenced by the variations of FRB and LFB. In one season,however,the four kinds of labile carbon correlated positively with FRB and LFB.The decomposition of SLOC is a complex biological process and is regulated by many factors.Because there is no specific definition and measurement for SLOC, how to evaluate the function and significance of measured labile organic carbon in terrestrial ecosystem’s carbon cycling and regional carbon balancing still needs a further study.更多还原