【作者】 杜红霞；

【导师】 刘增文；

【作者基本信息】 西北农林科技大学 ， 环境科学， 2006， 硕士

【摘要】 岷江上游地区是我国一个重要的大尺度、复合型生态过渡带,也是生态系统脆弱区,研究其森林生态系统C、N格局与动态,对人工林生态系统的稳定性、可持续性以及生物生产力的提高具有重要意义。本文通过建立固定林分标准地和干扰试验小区,在测算林分生物量和定期取样(植物和土壤)分析基础上,研究岷江上游四种典型人工林(连香树Cercidiphyllum japonicum、云南松Pinus yunnanensis、糙皮桦Betula utilis和云杉Picea asperata)生态系统C、N格局、凋落叶C、N释放及养分N生物循环特征。另外,通过对林地人为施加C源(蔗糖)和N源(硝酸铵)来进行干扰,对森林生态系统的C、N动态变化规律进行定位跟踪研究。取得的主要结果和结论如下:1.森林生态系统C、N格局(1)林木干材N含量最低,叶最高。同一林木N分布格局:连香树:叶>根>枝>皮>干;糙皮桦、云南松和云杉规律一致,即叶>枝>根>皮>干。不同林地林木各器官N累积有很大差异。林木各器官中C含量相差不大,干中稍高。同一林木C分布格局:连香树:干>枝>根>叶>皮;云南松:干>叶>果>枝>根>皮;糙皮桦:叶>根>干>枝>皮;云杉:皮>干>叶>枝>根。林地枯落物中C、N含量显著低于活立木。(2)不同森林生态系统N总贮量大小顺序为:云南松8694.12 kg/hm2、云杉7461.72 kg/hm2、连香树6043.50 kg/hm2、糙皮桦5075.64 kg/hm2,其中林木层占4.74%-10.74%,枯落物层占0.14%-0.69%,土壤N贮量占88.57%-94.58%。不同森林生态系统有机C总贮量大小顺序为:云杉155.447t/hm2、云南松135.171 t/hm2、连香树118.486 t/hm2、糙皮桦112.293t/hm2,其中林木层占37.75%-51.18%,枯落物层占0.42%-3.6%,土壤层占46.70%-61.83%。2.森林生态系统的N循环动态四种典型人工林N循环表现出归还量大于存留量。由循环系数和周转期可知,糙皮桦林地N元素归还快,循环强度大。由利用系数可知,针叶林(云南松和云杉)对N元素利用率比阔叶林(连香树和糙皮桦)高。四种人工林群落吸收系数和归还系数都相对较小,其林木N的吸收和归还对土壤N库影响不大。3.森林凋落叶分解过程中C、N释放动态林地凋落叶在分解初期干重损失最快。由凋落叶失重率、分解速率常数及其分解过程中C、N释放量规律可以得出,糙皮桦凋落叶分解最快,其次为连香树、云杉、云南松。在分解整个过程中,C元素处于单调净释放状态,且随时间的延续而增加;N释放量除云杉林地在240d内是负值外,其他三种林地均为正值,呈现释放状态。更多还原

【Abstract】 The upper areas of Minjiang River are a great important yardstick in our country, compounding type ecological intermediate zone, it is the fragile district of an ecosystem too. Studying its forest ecosystem C and N pattern and dynamics has profound important to the stability、constant and biological productivity of the artificial forests ecosystem. According to setting up fixed standard area and disturbance experimental plots, and based on calculating the forests biomass and analyzing fixed sample (plant and soil),this paper studied four kinds of typical artificial forests(Cercidiphyllum japonicum, Pinus yunnanensis, Picea asperata, Betula utilis) ecosystem C and N allocation, C、N releasing of litter-fall and nutrient N circulation biological characteristic of the upper reach of Minjing River. In addition, through exerting C source (cane sugar ) and N source (NH4NO3) to artificial disturbance forest, we studied forest ecosystem C and N dynamic change regularity. The main result and conclusion are as follows:1. Allocation of C and N in Forest ecosystem(1)N element content in stems is the lowest, the leaves’ is the highest. The forest N is distributed pattern: C.japonicum: leaves>roots >branches>barks> stems; P.yunnanensis and P.asperata have unanimous regularity, namely leaves>branches>roots>barks>stems; B.utilis: leaves >branches>roots>barks>stems. Different forests organ N Allocation was great diversity. C content is close among organs; it is relatively a bit higher in stems. The forest C allocation is: C.japonicum: stems> bran ches>roots>leaves>barks; P.yunnanensis: stems>Leaves>fruits >branches>roots >barks; B.utilis: leaves>roots>stems>branches>barks; P.asperata: barks> stems>leaves>branches>roots. Compared mass loss in the forest with living tree, C and N contents in leaves,branches and barks reduced very notably.(2)The order of total organic N storage of forest ecosystems was: P.yunnanensis 8694.12 kg/hm2, P.asperata7461.72 kg/hm2, C.japonicum 6043.50 kg/hm2, B.utilis 5075.64 kg/hm2. In general, tree layer accounts for 4.74%-10.74% of total N storage in the forest, mass loss layer of proportions is very small, it is only 0.14%-0.69%, the soil layer accounts for更多还原