【作者】 石培礼；

【导师】 李文华；

【作者基本信息】 中国科学院（自然资源综合考察委员会） ， 生态学， 1999， 博士

【摘要】 亚高山林线是一个显著的生态交错带,是监测和研究全球气候变化的最佳地段,在全球变化研究中具有重要的理论价值。植被生态学途径是揭示生态交错带生态过程及其与气候变化关系的基础,本研究以四川卧龙巴郎山岷江冷杉林线和长白山岳桦林线为研究对象,采用交错带生态梯度样带调查和重点地段典型抽样、定性和定量相结合的方法进行野外数据采集,同时收集研究区前人的研究成果和面上资料进行综合分析。在研究手段上,采用种群统计和植被生态学数量方法进行定量化研究。在重点解剖研究区和对比分析的基础之上,总结出亚高山林线交错带的生态学特征和分布格局。主要研究结果如下:中国亚高山林线植物区系十分丰富,云冷杉、落叶松、桦木、高山栎、圆柏、柏木都是亚高山林线树木的重要组成成分。青藏高原隆升和环境变迁是山地暗针叶林树种分化和特化的动力,高原的东南部是世界林线树种物种多样性最高的地区。亚高山林线植物区系主要由北温带和世界广布成分组成,林线植物区系具有典型的温带性质。青藏高原亚高山林线的三维地带性分布符合数学模式:H=exp( a + bx +cy + dxy + ex2 + fy2),在热量指标中,7月均温是亚高山林线分布的主导限制因子。青藏高原亚高山林线的水热条件属于Thornthwaite气候系统的寒冻潮湿型。植被数量方法是生态交错带定量判定的重要手段,游动分割窗技术和植被变异侧面图是交错带数量判定的两种有效方法。游动分割窗距离系数分布图的波峰和峰宽对生态交错带的位置和宽度有很好的指示性,植被变异侧面图还能指示林线环境的异质性。林线交错带是群落结构发生急剧变化的地段。林分的密度、高度和胸径都出现显著降低,群落层片结构趋于简单,草本植物组成趋于复杂,是相邻群落相互混杂和渗透的结果。林线交错带树木是增长种群,这是维持林线稳定和增长的基础。树木生长对林线交错带恶劣生境反应敏感,亚高山林线是山地垂直带上树木生长出现急剧降低的过渡带,也是生长型发生迅速变化的地段,在繁殖适应方面表现出多种适应途径。林缘具有明显的边缘效应,表现为较高的群落生态多样性。林线交错带是物种多样性较丰富的区间;同时,林线环境异质性较高,物种替代迅速,也出现β多样性的高峰。林缘形状对交错带物种多样性有较大的影响,凸型和直线型林缘的α多样性低于凹型林缘,但β多样性较高。凸型和直线型林缘物种更替较快,而凹型林缘物种替代较慢。林隙干扰是岷江冷杉林线交错带树木定居和森林更新的动力,林线交错带树木的死亡和定居对过去气候变化较为敏感,分别与过去气候变化的冷谷和暖期相对应。岷江冷杉林线是较为稳定的。长白山林线交错带的林缘形状对岳桦更新格局和向苔原入侵有重要影响。在凹型林缘外更有利于岳桦幼树向苔原的入侵和定居,林缘形状对木本植物入侵苔原具有强有力的控制作用。林缘形状引起的“凹凸逆转”的生态效应可能是岳桦林线缓慢上升的一种机制。最后,基于青藏高原近几十年来气候变化的趋势,探讨了未来气候变化情景下青藏高原亚高山林线分布高度的变化。青藏高原林线在未来气候情景下变动的幅度为150~600m,林线上升的幅度自西向东逐渐降低。更多还原

【Abstract】 Subalpine timberline is an apparent ecotone which controlled by climate. Various ecologistssuggested that timberline may be used for the detection of global climatic change . So it is of greatimportance in studying response of timberline ecotone to climate change. Vegetation ecology isthe basic approach to reveal the interrelation between ecological process of ecotone and itsresponse to climate change. This study is conducted on timberline of Abies faxoniana in BalangMountain, Wolong Natural Reserve of Sichuan province and that of Betula ermanii in ChangbaiMountain of Jilin province. By using the methods of transect survey and typical sampling of theecological gradient across timberline ecotone, in combined with qualitative and quantitativemethods to collect the field data, simultaneously the past research results and regional vegetationmaterials are also used for comprehensive analysis. The methodologies of population demographyand quantitative vegetation ecology were adopted for the analysis of the survey data. On the basisof comparison of results of research sites in Balang Mountain and Changbai Mountain, theecological characteristics and distribution pattern of timberline ecotone are summarized. The mainresults of the research are as follows:The species composition of trees in timberline are abundant. Spruce-fir, larch, birch, Quercus,Juniperus and alpine cypress are the main species at timberline. The uplifting and environmentalchange of Qinghai-Xizang Plateau are the motives which lead to the differentiation andspecialization of subalpine coniferous species. The timberline species are of great diversity in thesoutheast part of the plateau. The flora at timberline ecotone, mainly consisting of NorthTemperate and Cosmopolitan distribution type, are of typical temperate feature.The distribution of timberline in the Qinghai-Xizang Plateau coincides with three dimensionalzonation model: H=exp( a + bx +cy + dxy + ex2 + fy2). Among the thermal indices, the averagetemperature in warmest month is the main restrictive factor for timberline distribution. Thehydro-thermal conditions at timberline ecotone is categorized as frost-humid type.Quantitative vegetation ecology is the important means for identifying ecotone. Movingsplit-window (MSW) and vegetation differential profiles (VDP) are two effective methods todetermine ecotone. The peaks and their widths of the MSW distance functions are sensitiveindicators of the locations of ecotone and its ranges. The VDP can also show the environmentalheterogeneity of timberline ecotone.Timberline is a sharp ecotone that the community structure changes drastically. The density,mean height and diameter of stands decrease remarkably. The synusia structure tend to besimplified and the herbaceous species composition tends to be complicated. The herbs are mixtureand infiltration of adjacent communities. The size class of trees at the timberline ecotone presentsan increasing population age structure. This is the basis for stability and increase of timberline.Tree growth is sensitive and susceptible to unfavorable environment. Subalpine is the zone inwhich tree growth decreases sharply and growth form change swiftly. The trees are on multipleadaptation strategies in respect of reproduction.The boundary of timberline ecotone presents apparent edge effect which is reflected by highecological diversity at ecotone in the communities along the transect. Timberline is in the peakarea of either species diversity or β diversity. The boundary form plays a great role on the diversityat timberline in Changbai Mountain. The α diversity in convex and straight boundary is lower thanthat of concave, while the β of the former two boundary forms are higher than that of the latter one.The species turnover rates are more rapid in convex and straight boundaries, while that of concaveboundary is much slower.Gap disturbance is the driving force for tree establishment and forest regeneration at Abiesfaxoniana timberline. The death and establishment process at timberline ecotone are sensitive topast climate change featuring with peak periods of tree death and regeneration in cold period andwarm period respectively. The timberline of Abies faxoniana in Balang Mountain is stable. InChangbai Mountain, the boundary forms at timberline have great impact on seedlingsestablish-ment pattern and colonization in tundra. The concave boundaries are more favorable forseedlings establishment. Boundary form exert powerful control over the colonization of birch totundra. The “concave-convex reversal” of boundary forms may be the possible mechanism oftimberline rise.Finally, based on climate change tendency in recent decades in the Qinghai-Xizang Plateau,the climate change scenarios in the plateau are designed. The response of timberline to climatechange is analyzed and the vertical rise range of 150-600m is predicted. The rise range oftimberline has a tendency of decrease from west to east in southeast plateau.更多还原