【作者】 程小琴；

【导师】 韩海荣；

【作者基本信息】 北京林业大学 ， 生态学， 2014， 博士

【摘要】 油松(Pinus tabulaeformis Carr.)具有良好的保持水土、涵养水源及改良土壤的作用,是太岳山地区最主要的造林树种之一,也是暖温带湿润半湿润气候区的地带性群落的建群种。本文以太岳山宋家沟油松人工林为研究对象,研究影响土壤有机碳储量及其分布格局,分析影响其变化的关键生态因子；对不同密度油松人工林采用土壤碳循环分室模型,研究密度调控对油松人工林土壤碳循环的影响,同时,从土壤碳平衡的差异性探讨生态系统管理对土壤碳储存动态的调控机理。主要研究结论如下：(1)油松人工林土壤有机碳含量在土壤剖面中随土层深度增加而减小。土壤有机碳平均含量随立地因子变化表现为：阴坡>阳坡；坡下>坡中>坡上。土壤有机碳平均含量随林龄的增加呈增加；随着林分密度增加而呈波动趋势。对土壤有机碳含量具有显著或极显著影响的因子有土壤容重、土壤含水量、土壤pH值和土壤全K含量。(2)油松人工林土壤总有机碳密度的变化范围在57.83～121.88t·hm-2,主要储存在0～30cm土壤中。对油松人工林土壤有机碳密度与立地因子、植被因子和土壤因子的进行多元线性回归分析表明,影响土壤有机碳密度的主要影响因子有坡度、坡位、林龄、凋落物现存量、年凋落量、土壤含水量、容重、土壤全K含量、土壤全N含量等。(3)油松人工林地上凋落物年凋落量随林分密度减小而减小,地下细根凋落物则相反。随着林分密度的减小,叶凋落物和细根的分解速度都加快。在分解过程中,叶凋落物和细根中不同养分元素含量的动态变化存在一定差异。细根比叶凋落物易分解,且细根中的营养元素也较容易释放。叶凋落物和细根养分元素归还量随林分密度减小呈波动变化。叶凋落物和细根N、P、K、C4种元素归还总量排序为C>N>P>K。细根在油松人工林C和养分循环中占重要地位。(4)油松人工林土壤呼吸速随林分密度减小而增加,且表现出明显的季节动态。土壤呼吸各组分随林分密度变化其变化幅度不同,且对土壤总呼吸的贡献率大小不同。土壤异养呼吸是土壤总呼吸的重要组成部分,占土壤总呼吸的70%以上。生长季土壤总呼吸通量随着密度减小而增加,其中土壤自养呼吸通量随着密度减小呈波动趋势,土壤异养呼吸通量随着密度减小而增加,CK、LT、MT和HT林分生长季土壤呼吸通量分别为426.923、464.500、500.936和519.938g C·m-2。土壤温湿度是影响土壤呼吸的重要影响因子。土壤总呼吸和土壤异养呼吸与土壤湿度呈显著线性相关,与土壤温度均呈显著指数相关。土壤异养呼吸对温度敏感性Q10高于土壤自养呼吸。土壤温湿度共同对土壤总呼吸和土壤异养呼吸的变化具有显著的影响。土壤湿度、活细根生物量、表层土壤有机碳含量、土壤温度这4个因子解释70%油松人工林土壤总呼吸的时空变异。(5)油松人工幼龄林土壤碳输入和输出均随着林分密度减小而增大。油松人工幼龄林各密度林分土壤年CO2的平衡值均为正值,随着林分密度的减小而增大。研究结果表明,对油松人工幼龄林进行不同强度密度调控,有益于土壤对大气CO2的截存,而适度(中度和强度)干扰后更有利于增强油松人工幼龄林的土壤碳汇作用。论文从立地因子、植被因子及土壤理化性状等多个方面探讨了影响土壤有机碳储量及分布格局的关键生态因子,并揭示密度调控对油松人工林土壤碳循环的影响,其结果对山西太岳山地区林业生产经营活动以及我国现阶段的森林土壤碳汇功能评价工作具有一定的借鉴意义和实际应用价值。更多还原

【Abstract】 Pinus tabulaeformis Carr., a prominent species in forest plantations of Shanxi Province, is a common species of coniferous in the cool temperate zone of North China and plays a very important role in soil and water conservation and improving soil fertility in North China Mountainous Districts. This paper studied the carbon storage and its environmental response in P. tabulaeformis plantation in Shanxi province in northern China. In addition, based on the data collected from short-term located observation, the absorption, storage and release rates of carbon in soil ecosystem of20-year-old P. tabulaeformis plantation with four stand denstidies were investigated. The main results of the research are as follows:(1) The soil organic carbon content of P. tabulaeformis plantations decreased with soil depth increasing. The change of average soil organic carbon content of different site conditions was:shady> sunny; foot of the slope> mesoslope> top of the slope. The average soil organic carbon content in lm soil horizon increased with stand age, but did not increased with stand density. The soil organic carbon content correlated with soil bulk density, soil moisture content, soil pH and soil total K contents and this correlation depended on soil depth.(2) Total soil organic carbon density of P. tabulaeformis plantations varied from57.83to121.88t·hm-2with nearly half part of soil organic carbon being present in the top30cm of soil. The soil organic carbon density correlated with slope, slope position, stand age, litterfall mass, the annual litter, soil moisture content, bulk density, soil total K content and soil total N content and this correlation also depended on soil depth.(3) The result showed that aboveground litterfall decreased with stand density, whereas belowground litterfall was the opposite. The decomposition rate of litterfall increased as stand density decreased. The total element returns amount had notable different among four density stand, having the order of CK>MT>HT>LT. The element returns of litter had the order of C>N>P>K. The release rates and dynamic changes of nutrient elements (N, P, K and C) between the leaf litters and fine root litters exists some differences. The decomposition of fine root litters is easier than that of leaf litters, and also the nutrient elements rease more easily in the formers than in the latter. The fine root annual decomposition amount contributes28.6%～40.8%to the total litter decomposition. Amount of N, P, K and C return to soil from fine roots was32.3%～48.5%,24.4%～39.5%,26.6%～40.7%and28.8%～52.6%of total return amount. Therefore, fine root decomposition play an important role in C and nutrients cycling,(4) We found that immediately following thinning treatments, soil respiration increased by8%～21%compared with the unthinned control plots during both growing seasons. There were significant differences in soil respiration and its components among the various treatments. Compared with Ra, Rh made the major contribution to Rs during the growing season at all sites. The relative proportion of Rh to Rs averaged71.6%～79.7%over the four stands. During the growing seasons, the soil respiration and its components were positively correlated with the soil moisture. Correlations between Rh and soil moisture were more significant than that of Ra and soil moisture. Meanwhile, a positive correlation was found between soil temperature and soil respiration and its components at all sites. Rh and Ra have been shown to respond differently to increasing temperature, exhibiting different levels of sensitivity to temperature (Q10). Fitted Q10values of Rh ranged from2.16to2.75in the various thinning intensities, with the highest Q10value in the control sites; Rh is more sensitive to temperature than Ra in all stands. The model with the best fitted temperature and moisture factors explained18.6%～44.3%of the variation in Rs, 66.7%～77.3%of the variation in Rh and30.2%～46.4%in Ra between the four thinning sites during both growing seasons. Overall, soil respiration is better predicted by soil moisture, soil organic C, live fine root biomass and soil temperature when data are pooled for all thinning treatments over the two growing seasons. The best regression model explained74.7%of the total variation in soil respiration over the different thinning intensities for the two sampling periods.(5) After a carbon balance formula was formulated, the dynamics and balance of carbon was studied in the soil of P. tabulaeformis plantations. Results showed that CO2budget value increase with the decrease of the stand density. It is concluded that the decrease stand density could contribute to carbon sequestration, but that moderate and higher disturb would enhance the C sequestration more significantly. The results of this study can be used to help understand how forest management of P. tabulaeformis plantations affects carbon sequestration in forest soils.The paper study on soil carbon pool and effects of tree density on soil carbon cycling of P. tabulaeformis plantations, the analysis and results have certain contribution and practical application values to the forestry managerial and production activities in the Taiyue Mountain area as well as the current forest soil carbon assessment in China.更多还原