【作者】 王卫斌；

【导师】 吴兆录；

【作者基本信息】 云南大学 ， 生态学， 2011， 博士

【摘要】 发展人工林已经成为中国林业发展的一个重要组成部分,既是保护天然林的重要措施,又作为一种增加森林资源有效的途径而成为中国所需木材的主要来源。大规模发展人工林会不会造成生态退化,需要开展翔实的基础研究提供评判依据。本研究选择典型的热带季节性雨林向山地季风常绿阔叶林过渡区的西双版纳北部普文试验林场为研究地点,以13年生西南桦人工群落为对象,并以地带性植被山地雨林和西南桦天然林作对照,使用野外样方调查、室内理化分析和数学统计等方法,从群落学特征、土壤理化性状、群落生物量与初级生产力、群落碳储存能力等方面进行对比研究,为科学回答发展人工林对土壤、物种多样性、生态系统功能的影响提供依据。通过研究得出以下结论：1)西南桦人工林的物种组成及外貌特征与次生裸地状况密切相关。在山地雨林采伐迹地上营造的西南桦人工林Ⅰ演替进展较快,有维管束植物109种,分属59科92属,其科属种数量组成明显高于在以黄牛木、余甘子、红水锦树等为优势种的次生林采伐迹地人工或天然更新的西南桦人工林Ⅱ(33科56属60种)和西南桦天然林(30科52属55种)。西南桦人工林Ⅰ与山地雨林的物种相似性系数为24.68%,外貌特征也具有一定的相似性,具有一定的演替趋同性。2)普文西南桦人工林植物区系热带北缘性质明显,为热带亚洲植物区系向东亚植物区系的过渡,随着演替进展西南桦人工群落热带分布成分具有增加趋势。普文西南桦人工群落以热带区系成分(2-5型)为主,热带性质明显,但无典型热带分布的科。随着西南桦人工林向地带性植被的演替进展,西南桦人工群落热带分布成分呈增加趋势,而温带成分逐渐减少。3)利用西南桦等先锋树种开展人工林造林,有利于群落及其结构和功能的快速恢复,并加速向地带性植被演替进程。由于发育时间较短,与地带性植被山地雨林比较,13年生西南桦人工林结构层次分化尚不明显,尤其是乔木层只有一层,为西南桦单优种。但灌木层、草本层和藤本植物却较为发达,且物种丰富度、多样性和均匀度指数也达到了较高水平,尤其是西南桦人工林Ⅰ已超过山地雨林。随着演替进展,西南桦人工林灌木层乔木幼树的发育,如西南桦人工林Ⅰ灌木层的披针叶楠、红梗润楠、短刺栲、刺栲、杯状栲、红果葱臭木、滇桂木莲、云树、高阿丁枫、滇谷木、南酸枣、思茅蒲桃等树种,将使西南桦人工林乔木层结构进一步分化,形成复层结构。与此同时,灌木层、草本层发育和凋落物层增加,促使人工群落物质循环和能量流动进一步加快,群落的物种组成日益丰富,生产力不断增加,群落功能也得以快速恢复,促进了群落演替。4)土壤的恢复与群落的进展演替相并行,不同采伐迹地更新的西南桦群落土壤理化性状存在较大差异,近自然的人工林经营方式有利于土壤恢复发育。西南桦人工林Ⅰ土壤(0-40cm)有机质、全氮、水解氮、全磷、速效磷、速效钾的含量分别达22.62 g.kg-1、40g.kg-1、243.87 g.kg-1、36.30 g.kg-1、0.56 g.kg-1、159.89g.kg-1,均显著高于或高于西南桦人工林Ⅱ和西南桦天然林。西南桦人工林Ⅰ表土层(0-20cm)容重和总孔隙度分别为1.235g.cm-3、52.381%,与西南桦人工林Ⅱ和西南桦天然林比较,表现出随群落结构复杂性和物种多样性增加土壤孔性状况逐渐变好的趋势,这说明了人工群落演替进展对土壤的孔性状况有较好的恢复作用。西南桦人工林Ⅰ表土层土壤砂粒、粗粉粒和细黏粒粒级分别为17.526%、22.136%和13.921%,与山地雨林的粒级比例和结构(25.704%、31.067%和24.948%)较为接近,进一步证明了群落对土壤的恢复作用随着演替进展而逐渐增强。5)随着西南桦群落演替进展,群落结构不断完善,土壤各养分之间的相关性随之增强。与山地雨林相比较,3种西南桦群落以西南桦人工林Ⅰ土壤养分之间的相关性最好。西南桦人工林Ⅰ的土壤养分之间的相关性除速效磷与其他养分之间的相关性稍差外(相关系数为0.285-0.581),其余土壤养分之间的相关系数均在0.5以上；西南桦人工林Ⅱ的土壤养分之间的相关性比西南桦人工林Ⅰ差,只有土壤有机质和全氮分别与其余养分之间显著相关,速效磷和速效钾分别与水解氮和全磷之间以及速效磷与速效钾之间都无显著相关关系；西南桦天然林土壤养分之间的相关性最差,土壤养分只有有机质与其他养分之间呈显著相关,其余指标之间虽然有部分有显著相关,但多数养分之间都不显著相关,甚至全磷与水解氮之间出现了负相关关系。6)有效态磷素的缺乏和酸性较强是影响西南桦群落林地土壤肥力的主要限制性因子,人工追施磷肥和改良土壤的酸碱度有利于加速西南桦群落的快速发育。3种西南桦群落有效磷含量低,仅为0.42mg-kg-1-1.07mg-kg-1,与全磷相差39.50-78.19倍；表土层土壤pH值为3.92-4.78,属强酸性土壤,磷素很快被土壤固定,导致速效磷长期处于严重贫瘠的状况,人工追施磷肥和改良土壤的酸碱度有利于加速西南桦群落的健康发育。7)西南桦群落恢复初期林,乔木层、灌木层和凋落物生物量随着演替进展呈快速增长趋势,草本层生物量呈下降趋势。随着乔木层单优种西南桦的快速生长和灌木层的发育,草本层生物量因林分郁闭度增加,呈下降趋势。8)西南桦人工林具有较高的生物量、净初级生产力和较强的固碳能力,开展抚育间伐有利于林分蓄积的持续增长,以提高西南桦人工林的生态效益。13年生西南桦人工林Ⅰ和西南桦人工林Ⅱ生物量分别为108.31t/hm2和83.62t/hm2,净初级生产力分别为19.99 t/hm2a和11.1t/hm2·a,年固碳量达3.87t/hm2和3.07 hm2,随着西南桦群落的快速发育,西南桦人工林林对光照和水肥的竞争更加强烈,适时地开展抚育间伐,将有利于林分蓄积的持续增长和结构优化。9)西南桦人工林表土层的物理性状在演替初期表现出先低后高的趋势,应加强西南桦人工林中幼林的抚育。在西南桦人工林演替初期,随着灌木层和草本层物种多样性与生物量增加,对养分需求的不断增加,导致表土层矿物质和有机质含量迅速下降,致使表土层容重增加和总孔隙度减少。加强对西南桦人工林中幼林的抚育,对人工植被和生物多样性的快速恢复是十分必要的。更多还原

【Abstract】 Presently in China, cultivation of artificial forests has become an important content in forestry development. Artificial forest cultivation is not only a necessary measure for protecting natural forests, but also an effective way to produce timber. What are the impacts the scaled artificial forests imposed on ecological environment? Detailed studies were urgently needed.This study choosing Puwen experimental forest farm located at north part of Xishuangbanna as study site, which is the transition from typical tropical seasonal rain forest to montane monsoon evergreen broad-leaved forest, the artificial community of 13 years old Betula alnoides was selected as the study target, taking zonal vegetation type montane rain forest and Betula alnoides natural secondary forest as the control, adopting the methodology including field plot sampling, laboratory experiments and statistical analysis, comparative study was conducted from community characteristics, soil physical and chemical properties, community biomass, net primary productivity and carbon storage. The main results and conclusions are as follows.1) Species composition and physical characteristics of Betula alnoides plantation were closely related with the site status before planting. The Betula alnoides plantation coded I (BAP1) established on the cutting blank of montane rain forest had abundant diversity of the species and fast succession progresses). Totally 109 species (belong to 59 families and 92 genera) of vascular plant were recorded, which significantly exceeded those of Betula alnoides plantation codedⅡ(BAP2) (60 vascular bundle species,33 families, and 56 genera) and Betula alnoides natural forest (BANP) (55 vascular bundle species,30 families, and 52 genera) established on secondary forest cutting blank. Moreover, very abundant species composition (61 species) of shrub layer of was recorded in BAP1. The plant species’Jaccard similarity coefficient of BAP1 and tropical montane rain forest (TMRF) was 24.68%, characterized similar morphology and convergent character to a certainty.2) In Betula alnoides community in Puwen of Xishuangbanna, the tropical elements were dominant, characterized by the transition from tropical Asia to east Asia. With the succession progress, the tropical distribution elements present increasing trend. Dominated by areal types 2-5, it was obvious that the flora of Betula alnoides plantation in Puwen is of tropical in nature, characterized by absence of representative tropical distributed families. With the succession progress, the tropical distribution elements present increasing trend while temperate distribution elements decreasing. 3) Choosing pioneer tree species such as Betula alnoides, is helpful for the quick restoration of both structure and function, and speeding up of succession to zonal vegetation type. Comparing with TMRF,13 years old Betula alnoides plantation did not show obvious layer differentiation, with only one tree layer of the species of Betula alnoides. However, the components of shrub layer, grass layer and lianas were all well developed, the species richness, diversity index and evenness index of BAP1 were higher than TMRF. As the succession progresses, the tree species presently in shrub layer such as Phoebe lanceolata, Machilus rufipes, Castanopsis echidnicarpa, Castanopsis hystrix, Castanopsis calathiformis, Dysoxylum binectariferum, Manglietia forrestii, Garcinia cowa, Altingia excels, Memecylom polyanthum, Choerospondias axillaries, Syzygium szemaoense, will further differentiate, promote the complication of structure and finally form multi-layer trees. Simultaneously, with the development of shrub, grass layer litter, the speed of matter cycle and energy flow in Betula alnoides plantation will further be increased, the function of community will be improved from both plant abundance and productivity, which is necessary for further community succession.4) Restoration of soil fertility was synchronous with the succession of plant community, the physical and chemical characteristics of soil in Betula alnoides communities established from different sites varied significantly. The basic indexes of Betula alnoides plantation coded I, namely organic matter, total N, valid N, total P, valid P, available K, were 22.62 g.kg-1、1.40 g.kg-1、243.87 g.kg-1、36.30 g.kg-1、0.56 g.kg-1、159.89 g.kg-1, these values were significantly higher than Betula alnoides II and natural Betula alnoides forest. The bulk density and general porosity of surface soil in Betula alnoides coded I plantation were 1.235 g.cm-3 and 52.381% respectively, which was better than BAP2 and BANF. In surface soil of Betula alnoides plantation coded I, the contents of sand, silt and clay were 17.526%,22.136% and 13.921% respectively, which were close to those of montane rain forest,25.704%,31.067% and 24.948% respectively.5) As the succession progressing and the improvement of community structure, the correlation between different soil nutrients became closer, and the soil fertility gained gradual recovery. Among all the three plant communities studied, BAP1 showed the best performance in nutrient correlation, except for the correlation between available P and other nutrients with the correlation coefficients ranged from 0.285 to 0.581. the correlation coefficients of other nutrients were higher than 0.5. As far as BAP2 was concerned, only organic matter and total N had significant correlation with other nutrients. The nutrient correlation of BANF was the poorest, only organic matter showed the significant correlation with other nutrients. 6) Insufficient available Phosphorous and too acid soil were two restriction factors to the soil fertility of Betula alnoides plantation. P application and soil pH improvement were propitious for quick development of community. The contents of available P of three studies Betula alnoides communities ranged from 0.42mg-kg-1—1.07mg·kg-1 only, while soil pH values were 3.92—4.78. Available Phosphorous was easily fixed by soil. P application and soil pH improvement were necessary to health development of Betula alnoides plantation.7) In the early stage, as the progress of succession, the biomass of tree layer, shrub layer and litter showed the tendency of rapid growth, while that of grass layer showed the tendency of decrease. With development of tree layer and shrub layer, the biomass of grass layer was decreased due to the enhancement of canopy density.8) Betula alnoides plantation had promising biomass, net primary productivity and carbon fixation capability, timely tending and thinning were benefit for sustained increase of volume, so as to increase the ecological benefit of Betula alnoides plantation. The biomass of BAP1 and BAP2 were 108.31t/hm2 and 83.62t/hm2 while the net primary productivity were 19.99 t/hm2·a and 11.1 t/hm2·a, and the annual carbon fixation were 3.87t/hm2 and 3.07 hm2 respectively. With the development of Betula alnoides plantation, competition among water, light, and fertilizer will be stronger. Tending and thinning were necessary to volume increasement and structure optimization.9) In the early stage of succession, the physical properties in surface soil layer showed the tendency of degradation first and then recovery, tending was a very critical measure in management of young Betula alnoides plantation.更多还原