【作者】 潘辉；

【导师】 洪伟；

【作者基本信息】 福建农林大学 ， 森林培育学， 2008， 博士

【摘要】 相思树种是世界广泛引种的重要速生树种,在我国南方短周期工业原料林建设、林地可持续经营和丰富林木种质资源等方面具有重要的作用和地位。人工林凋落物养分归还是林分有机物产生的首要过程,养分的利用、循环和流动是有机物和土壤系统内部及其相互之间的枢纽,养分元素循环在维持人工林生态系统格局及形成最大生产力及生物量产出的过程中具有极其重要作用。鉴于有关相思人工林凋落物养分归还功能和碳平衡的研究缺乏系统性,相关报道亦较少。本研究选择位于福建省漳州市平和天马国有林场的6.5a生卷荚相思（Acaciaconcinnatai）、黑木相思（Acacia melanoxylon）和马占相思（Acacia mangiun）为研究对象,从2006年8月起,进行为期一年的生态定位研究,开展凋落物收集、凋落物分解和土壤表面CO₂释放量等数据采集等野外作业,并结合土壤和植株养分等室内分析,掌握相思人工林生物量分配格局,探讨相思人工林凋落物养分（N、P、K和C）的归还规律,评估相思人工林碳汇能力,为指导相思人工林科学经营管理和闽南山地的可持续经营提供科学依据,为我国应对未来的国际气候变化谈判提供基础数据。主要得出以下结论:（1）卷荚相思单株生物量最高,分别是黑木相思和马占相思单株生物量的1.34和1.59倍。3种相思单株各器官所占比例大小顺序均为树干＞树根＞树皮＞树枝＞树叶。卷荚相思林分生物量最大,明显高于黑木相思和马占相思。在林分生物量组成中,乔木层所占的比例均最大,在87.06%～91.11%之间,凋落物的贡献仅次于乔木层,在6.48%～6.97%之间;（2）卷荚相思、黑木相思和马占相思年凋落物量分别为6171.49、7338.28和6102.16kg·hm^-2,凋落叶在凋落物中占绝对优势,分别占总凋落物量的65.32%、83.71%和68.10%。3种相思人工林总凋落物量的月变化均呈双峰模式;（3）卷荚相思和马占相思凋落物的N、P的年归还量相近,但均显著低于黑木相思（p＜0.05）,与总凋落物量的大小顺序相似。而3种相思人工林K的年归还量大小排序表现为马占相思(22.28kg·hm^-2·a^-1)＞卷荚相思(19.96kg·hm^-2·a^-1)＞黑木相思(17.76kg·hm^-2·a^-1)。3种相思人工林凋落物的养分年归还量大小顺序均表现为:N＞K＞P。黑木相思凋落物碳的年归还量最大,分别是卷荚相思和马占相思的1.27和1.23倍。卷荚相思凋落物碳归还季节变化的大小顺序表现为秋季＞夏季＞冬季＞春季,黑木相思凋落物碳归还的季节变化表现为春、夏和秋三个季节凋落物碳的归还量较大,马占相思凋落物碳归还的季节变化表现为夏季和秋季有较大的归还量,在春季和冬季有较小的归还量。;（4）分解1a后凋落叶的干重残留率从小至大依次为马占相思、黑木相思、卷荚相思和木荷（Schima Superba）（当地的地带性植被木荷（作为对照））。与凋落叶相比,凋落枝在分解过程表现更为平稳,不过其分解动态与凋落叶相似。凋落枝分解1a后,它们干重残留率从小至大依次为马占相思、黑木相思、卷荚相思和木荷;（5）3种相思人工林和木荷凋落叶在分解过程中C、K浓度均表现为递减的趋势,P浓度则表现为递增趋势,而N浓度表现为无规则的波动,波动幅度不大;凋落枝在分解过程中除C表现为明显的下降趋势,N、P、K浓度的变化均远较凋落叶复杂,可能是由于器官的差异引起的;（6）3种相思人工林和木荷凋落叶和凋落枝在分解过程中的C、N均表现为明显的净释放。在所有林分中,马占相思凋落叶的K的释放量最大,而其凋落枝K释放量小,表现为净吸存。卷荚相思和木荷凋落叶、枝在分解过程中P的释放与分解时间相关性较弱,没有达到显著水平（p＜0.05）,甚至表现为净吸存。除了马占相思凋落枝外,各养分的释放速率的大小顺序为:k_K＞k_C＞k_N;（7）黑木相思凋落物C的释放量高于卷荚相思和马占相思。黑木相思凋落物N的释放量最高,而卷荚相思最低。3种相思人工林K释放量的大小顺序为:马占相思、卷荚相思和黑木相思。卷荚相思凋落物P则表现为净吸存,每年吸收0.45 kg·hm^-2,黑木相思和马占相思均表现为净释放,每年分别释放2.27kg·hm^-2和1.65 kg·hm^-2;（8）对凋落物的初始养分与土壤养分进行相关分析,发现土壤容重与凋落叶的初始养分存在负相关,土壤有机碳与凋落叶的初始养分正相关。凋落叶初始N含量与土壤全N、土壤水解性N以及土壤速效K存在正相关;凋落叶初始P与土壤全P存在紧密的正相关;初始钾含量与土壤全钾存在正相关,均达到显著水平（p＜0.05）。表明在一定程度上,土壤的养分水平决定了凋落叶的初始养分水平。凋落枝初始N、P含量与土壤表层全N和全P含量存在正相关,均达到显著水平（p＜0.05）;然而凋落枝初始K含量与土壤全K和速效钾含量表现为弱的负相关,可能由于植物生理功能的差异决定了凋落枝有较低的K初始含量;（9）选用凋落物质量指标和生境质量指标等14个与凋落物分解速率关系较为密切的变量,进行PCA分类排列。结果发现,对第一主成分贡献率最大的是初始N含量,其次为土壤有机碳、土壤水解性N、土壤全N含量、初始C/N、初始P含量和土壤有效K;对第二主成分贡献率最大的是初始K含量,其次为土壤全K含量、土壤全P含量、土壤C/N、土壤速效P和初始C含量;（10）3种相思人工林各器官的含碳量均在45%～50%之间。卷荚相思和黑木相思各器官碳贮量的大小顺序均为:树干＞树根＞树皮＞树枝＞树叶,马占相思则为树干＞树根＞树皮＞树叶＞树枝。卷荚相思、黑木相思和马占相思林下植被层平均的含碳量分别为42.29%、42.78%和41.26%,明显低于其乔木层相应组分的碳含量。卷荚相思、黑木相思和马占相思枯枝落叶层碳贮量分别为2.27t·hm^-2、1.61t·hm^-2和1.63t·hm^-2。卷荚相思、黑木相思和马占相思生态系统碳贮量分别为93.63t·hm^-2、109.50t·hm^-2和77.37t·hm^-2;（11）在3种相思人工林和木荷林中,其土壤呼吸、无根土壤呼吸和根呼吸的季节动态与土壤温度的季节动态变化基本一致,呈明显的单峰曲线;而枯枝落叶层呼吸季节变化较为复杂,不过总体上仍表现为夏季较高而冬季较低;（12）在3种相思人工林和木荷林中,土壤呼吸α值的大小顺序为黑木相思、卷荚相思、木荷和马占相思。土壤呼吸的Q₁₀值的大小顺序为马占相思、卷荚相思、木荷和黑木相思;3种相思人工林和木荷林在冬季基本上表现为最小的残差值,在春季表现出较大的负残差值,而在秋季表现出较大的正残差值。在黑木相思林和木荷林其根呼吸的温度敏感系数Q₁₀值高于其它组分呼吸;而在卷荚相思和马占相思林其根呼吸的温度敏感系数Q₁₀值则明显低于其它组分呼吸;（13）对凋落物的月输入量与土壤呼吸速率进行相关性分析,发现它分别能解释卷荚相思、黑木相思和马占相思土壤呼吸速率变化的47.91%、36.57%和29.69%;而对降雨量与土壤呼吸速率进行相关分析,发现降雨量对土壤呼吸速率的贡献相当有限（均小于20%）;（14）木荷林土壤呼吸的年释放量最小,分别是卷荚相思、黑木相思和马占相思林的68.66%、88.63%和73.44%。卷荚相思、黑木相思和马占相思无根土壤呼吸的年释放量分别为5.21、5.05和5.24tC·ha^-1·a^-1,它们之间差异不显著（p＞0.05）,但均显著高于木荷林。木荷林根呼吸的年释放量最大,分别是卷荚相思、黑木相思和马占相思的1.47、1.51和1.23倍。卷荚相思林有最大的凋落物呼吸年释放量,明显高于其它林分;（15）卷荚相思、黑木相思和马占相思人工林C年净吸存量分别为14.01,10.31和11.57t·hm^-2·a^-1,其中乔木层C年积累量分别为4.98、4.06和3.03t·hm^-2·a^-1,枯落物C年归还量分别为8.63、6.08和7.48t·hm^-2·a^-1。不同林分碳年净吸存量中林分生物量的C年积累量和枯落物C年归还量分别约占40%和60%。卷荚相思、黑木相思和马占相思人工林净生态系统生产量分别为4.46,3.62和3.59t·hm^-2·a^-1,均表现为“碳汇功能”,相当于每年可从大气中分别固定CO₂ 16.36、13.27和13.15t·hm^-2·a^-1。更多还原

【Abstract】 Acacia spp.is an important fast-growing tree and has been introduced all over the world.It plays vital roles on the forests construction of short-period industrial raw material,sustainable forest management and germplasm resources of forest trees in South China.The nutrient return from litter layers is the initial process of organics production in the forest.Nutrient utilization,recycling and flowing was the hub between the organic matter and the soil system interior.The circulation of nutrient elements significantly maintains the ecosystem pattern and forms the considerable productivity and biomass outputs.However,the study on functions of nutrient returns from litter layers and carbon balance has been rarely reported.The location of research was chose at Dongxi work area of Tianma national forest station in Zhangzhou,Fujian,from August 2006 for one year.Three tree species including Acacia concinnatai,Acacia melanoxylon and Acacia mangiun were chose as the treatments and the subtropical species Schima Superba as the control.Our field work covers litter collection,litter decomposition experiment and CO₂ release from soil surface,the plants and soil nutrient were analyzed as well.Our purposes were studying the allocation patterns of biomass of Acacia spp.,exploring the rules of nutrient recycling including C、N、P、K returns from litter layers and assessing carbon source/sink status in Acacia plantations.This research provides the scientific foundation for guiding scientific management of Acacia plantations and sustainable management on Minnan mountainous region and basic database for dealing with future climate negotiations of our country.The conclusions were as follows:（1）The highest individual plant biomass was found in Acacia concinnatai which was 1.34 and 1.59 times as heavy as Acacia melanoxylon and Acacia mangiun,respectively.The order of organ proportion for each plant was stems＞root＞the bark＞branch＞leaf.Significantly higher stand biomass was found in Acacia concinnatai than in Acacia melanoxylon and Acacia mangiun species.In the composition of stand biomass,higher proportion was found in tree layers（87.06%～91.11%）as compared litter layers（6.48%～6.97%）.（2）The annual litter-fall of Acacia concinnatai,Acacia melanoxylon and Acacia mangiun were 6171.49, 7338.28 and 6102.16 kg·hm^-2,respectively.Of these,the percentages of leaf litter of Acacia concinnatai,Acacia melanoxylon and Acacia mangiun were 65.32%,83.71%and 68.10%,respectively.The monthly dynamics of total litter-fall showed the double-peak modes.（3）The annual nitrogen and phosphorus returns from litter layers of Acacia concinnatai and Acacia mangiun were similar,but they were significantly（p＜0.05）lower than that of Acacia melanoxylon.The order of annual potassium returns from litter layers were Acacia mangiun(22.28 kg·hm^-2a^-1)＞Acacia concinnata i(19.96 kg·hm^-2a^-1)＞Acacia melanoxylon(17.76 kg·hm^-2a^-1).The order of annual nutrient returns from litter layers were nitrogen（N）＞potassium（K）＞phosphorus（P）.The highest carbon returns was found in Acacia melanoxylon than in Acacia concinnatai（1.27 times）and Acacia mangiun（1.23times）.The seasonal changes of carbon returns from litter layers in Acacia concinnatai were autumn＞summer＞winter＞spring;Similar higher carbon returns were found in Acacia melanoxylon between spring,summer and autumn than in winter.Higher carbon returns in Acacia mangiun were found on summer and the autumn than that in spring and winter.（4）The residue rates of dry weight of leaf litter and litter branches were Acacia mangiun＞Acacia melanoxylon＞Acacia concinnatai＞Schima Superba by decomposing for one year.The decomposition process of litter branches was more stable than that of leaf litter,but decomposition dynamics were similar to leaf litter.（5）The concentration of carbon（C）and potassium（K）from leaf litter decreased with the litter decomposed, whereas phosphorus concentration increased.The nitrogenous concentration represented ruleless fluctuation with indistinct amplitude.The change of other nutrient concentrations（such as nitrogen、phosphorus and potassium） were complexity except that carbon concentration decreased during the decomposition process owing to discrepancy of plant organs.（6）Obviously net release amount of carbon and nitrogen were found from leaf litter and litter branch during decomposition process.However,net absorption of the potassium release was showed in Acacia mangiun with higher in leaf litter and lower in litter branches.There was not significant（p＜0.05）relativity between release amount of phosphorus and decomposition time for Schima superba and Acacia concinnatai,even represented net sequestration.Except for Acacia mangiun’s litter branch,the order of nutrient release rate was k_K＞k_C＞k_N.（7）The carbon release of Acacia melanoxylon was higher than that of Acacia concinnatai and Acacia mangiun.The highest nitrogen release amount was found in Acacia melanoxylon,but lowest was found in Acacia concinnatai.The order of potassium release amount was Acacia mangiun＞Acacia concinnatai＞Acacia melanoxylon.The annual phosphorous absorption in Acacia concinnatai was about 0.45 kg·hm^-2,while net phosphorous release of Acacia melanoxylon and Acacia mangiun were 2.27 kg·hm^-2and 1.65 kg·hm^-2,respectively.（8）There was negative correlation between initial nutrient of litter and the soil nutrient,but positive correlation was found between soil organic carbon and initial nutrient of leaf fitter.The initial nitrogen content of leaf litter was significantly positive correlation with soil total nitrogen content,soil hydrolysable nitrogen and soil available potassium.The initial potassium content of leaf litter was significantly positively related to soil total potassium.Thus,the soil nutrient level has influenced on the initial nutrient level of defoliation.The initial N and P content in litter branches was significantly（p＜0.05）positively related to those in the surface soil.However,there was negative correlation between K content of branches,total K content in soil and available K possibly because the different physiological functions of plants induced the lower K content in branches.（9）Fourteen quality indices of litter and habitats were chose to analyze the decomposition rate using PCA classification.The results showed that the principal component was the initial N content that was followed by soil organic carbon,soil hydrolysis N,total soil N content,the ratio of C/N,the initial P content and soil available K. The second mian component was the initial K content which was followed by total K content and P content in soil, the ratio of C/N in soil,the available P in soil and the initial C content from litters.（10）The percentage of carbon content of each organ was about 45%～50%for the three Acacia plants.The order of carbon content of the Acacia concinnatai and the Acacia melanoxylon were the trunk＞the root＞the bark＞the branch＞the leave and carbon percentage in Acacia mangiun was the trunk＞the tree root＞the bark＞the leaf＞the branch.The average carbon contents in understory forest of the Acacia concinnatai,the Acacia melanoxylon and the Acacia mangiun were 42.29%,42.78%and 41.26%,respectively,which was obviously lower than those in tree layer.The carbon storage of litter in the Acacia concinnatai,the Acacia melanoxylon and the Acacia mangiun were 2.27t·hm^-2,1.61t·hm^-2and 1.63t·hm^-2,respectively.The carbon storage of the Acacia concinnatai,the Acacia melanoxylon and the Acacia mangiun in ecosystem was 93.63 t·hm^-2,109.50 t·hm^-2and 77.37 t·hm^-2;respectively.（11）The seasonal changes of soil respiration,non-root soil respiration and root respiration were consistent with the soil temperature with a single peak.However,the seasonal changes of litter respiration were complex, which higher in summer and lower in winter.（12）The order of a value of soil respiration was Acacia melanoxylon,Acacia melanoxylon,Schima superba and Acacia mangiun.The order of Q₁₀value of soil respiration was Acacia mangiun,Acacia melanoxylon, Schima superba and Acacia melanoxylon.The lowest residuals were found in the Schima superba forest and Acacia trees in winter,but negative residual was found in spring and positive in autumn.For Schima superba and Acacia melanoxylon,the temperature sensitive coefficient Q₁₀was higher in root respiration than that of other components.For the Acacia melanoxylon and Acacia mangiun,the temperature sensitive coefficient Q₁₀was lower in root respiration than that of other components.（13）The soil respiration velocity in the Acacia melanoxylon,Acacia melanoxylon,and Acacia mangiun was 47.91%,36.57%and 29.69%,respectively,using the relevant analysis between litters and soil respiration.The contribution rate of rainfall was less than 20%to the soil respiration using the relevant analysis.（14）The annual release amount of soil respiration was lowest in the schima superba,which was 68.66%, 88.63%and 73.44%to Acacia melanoxylon,Acacia melanoxylon,and Acacia mangiun,respectively.The annual soil respiration of non-root in Acacia melanoxylon,Acacia melanoxylon,and Acacia mangiun was 5.21,5.05 and 5.24tC·ha^-1·a^-1,respectively.The annual release amount of root respiration was highest in the schima superba, which was 1.47,1.51 and 1.23 times to Acacia melanoxylon,Acacia melanoxylon and Acacia mangiun, respectively.Higher litter respiration was found in Acacia melanoxylon than the other stands.（15）The annual net storage amount of carbon in the Acacia melanoxylon,Acacia melanoxylon and Acacia mangiun was 14.01,10.31 and 11.57t·hm^-2·a^-1,respectively,Of these,the C storage amount in the tree layer was 4.98,4.06 and 3.03 t·hm^-2·a^-2,respectively,and the annual C returns amount in litters was 8.63,6.08 and 7.48 t·hm^-2·a^-1,respectively.The annual C accumulation was about 40%and C return was about 60%.The net biomass productions of Acacia melanoxylon,Acacia melanoxylon,and Acacia mangiun in ecosystem were 4.46,3.62 and 3.59 t·hm^-2·a^-1,which was called "carbon sequestration functions".It means equal to fix CO₂ 16.36,13.27 and 13.15 t·hm^-2.a^-1every year for Acacia melanoxylon,Acacia melanoxylon and Acacia mangiun,respectively.更多还原