【作者】 康敏明；

【导师】 达良俊；

【作者基本信息】 华东师范大学 ， 生态学， 2010， 博士

【摘要】 常绿阔叶林是我国东部地带性自然植被,但长期的人为干扰导致面积日益减少,处于严重受损退化状态。并且由于干扰方式、程度各不相同,导致退化类型多样。因此,为了控制退化,加快恢复,急需阐明不同干扰下,受损常绿阔叶林恢复过程和机制。本研究采用实验生态学方法,于2003年10月在浙江天童国家森林公园以米槠-木荷群落为对象,模拟区域不同干扰,以4种方式进行采伐:①在样地Ⅰ中对高度大于8m,DBH大于5cm的大树进行择伐;②在样地Ⅱ中将地上植物全部清除,保留枯枝落叶层;③在样地Ⅲ中:清除地上全部植物,并清除枯枝落叶层和表土层(0-10cm);④在样地Ⅳ中仅清除下木层和草本层,保留大树。本文在前人研究的基础上,继续对群落物种组成、群落结构、生境因子进行定位追踪调查(2006-2008年),以期归纳总结植物群落恢复初期(5年)的恢复动态过程,判明其恢复格局。并从主要树种迁居方式、生长格局、繁殖策略方面,结合叶性状、构型等多层次,对恢复初期主要树种的生态适应策略的探讨,以期解析植被恢复的驱动力、限制因子,从而阐明恢复初期格局的形成机制,为受损常绿阔叶林的恢复提供理论依据。主要结论如下:(1)不同干扰下植物群落物种丰富度在恢复5年内均迅速增加,并高于干扰前顶级群落的数量。前期表现为破坏严重的样地中呈现指数增长,第3年达到高峰,并出现拐点。5年后干扰轻的样地中物种数最高。(2)不同干扰样地内生活型组成改变显著。恢复1年以一年生、多年生草本为主,木本植物以落叶阔叶树种为主,而且随着干扰程度的增加而增加。随着恢复进展,群落分层逐渐形成,落叶树种优势度下降,常绿树种增加。至恢复5年,清除了植被,甚至去除了表土的样地上落叶阔叶树——南酸枣(Choerospondiasaxiliaris)和檫木(Sassafras tzumu)已高达6.5-7m。(3)在前人研究的基础上,根据物种在恢复过程中出现和消失的情况,把各物种分为:维持种、消失种、迁入种和一过性物种。同时研究了不同干扰样地内木本植物种子散布方式和更新类型,得出强度干扰样地内恢复初期风力传播种子较多,常绿萌枝更新比例最高。常绿树种强大的萌枝能力,使得在受损群落恢复初期即出现顶级树种。(4)对恢复初期不同程度干扰样地内光、空气和土壤温湿度、土壤化学性质的测定,以及植物群落恢复初期格局,可将受损常绿阔叶林恢复划分为四种恢复类型。①更新促进型(样地Ⅰ),去除乔木层后光照的增加使得林下米槠、石栎等常绿阔叶树种得到释压而迅速生长。②更新抑制型(样地Ⅳ),林下植被的去除导致耐荫蕨类的大量繁殖,并占有很大优势,阻碍了木本植物的更新和生长。③演替进展型(样地Ⅱ),充足的光照,丰富的外来种源、原有物种的萌枝库、土壤种子库以及良好的土壤条件,使得群落迅速进入次生演替过程。④演替迟滞型(样地Ⅲ),枯枝落叶层和表土层的去除导致种子库的破坏以及土壤养分的贫瘠,从而抑制了部分先锋物种的定居,或生长、繁殖,物种丰富度低于其他样地,且恢复速率明显落后于样地Ⅱ。受损常绿阔叶林恢复初期四种不同恢复格局的出现,为本地区存在“多途径演替”假说提供了成因论方面的佐证。(5)对恢复过程中的两大种组:迁入种和维持种中7个主要树种(迁入种中选择落叶的山鸡椒(Litsea cubeba)、檫木和南酸枣,维持种以常绿的木荷(Schimasuperba)、石栎(Lithocarpus glaber)、米槠(Castanopsis carlesii)和栲树(Castanopsisfargesii)为研究对象)的数量动态、空间分布格局,以及高生长轨迹的测定,得出干扰生境中以落叶树种为主的迁入种分布范围的扩大和种群数量的增加均大于常绿树种,且与种子重量和传播方式有关;对以常绿树种为主的维持种而言,干扰后种群大小主要取决于干扰前种群大小和萌枝能力。迁入种早期生长速率大于维持种。(6)在恢复初期高生长速率是占据优势的重要途径,对恢复初期7个主要树种叶性状(包括最大净光合速率、比叶面积、叶氮磷含量)和构型的测定和分析,以期从树种转化光能以及获取光能两方面对树种的生长速率进行解释。结果表明:以落叶树种为主的迁入种具有高光转化能力,并对枝系结构的投入较低,具有简单的枝系结构、扁平的树冠,而将资源投资于枝条的生长,即采取高获取低消耗的积极型生存策略,是对光照充分环境长期适应的结果,这保证落叶树种在恢复初期的竞争优势。以常绿树种为主的维持种具有低的光转化能力,并对枝系结构的投入较高,具有复杂的枝系结构、宽厚的树冠,而对枝条生长的投资较少,即采取低获取高消耗的保守型生存策略,是对郁闭环境长期适应的结果,这使得其在恢复初期高生长速率较低,但是常绿树种成为后期优势种和林内伴生种的手段。(7)干扰强度和方式的不同导致资源可利用率的变化,从而对植物叶性状和构型产生影响。其中,光照和土壤养分是主要的环境因子。在干扰轻的郁闭生境中,植物最大光合速率较低,植物倾向于形成大而薄的叶片、低分枝率、较小枝叶倾角、短枝条、平展的树冠以扩大截收光照的面积并减少自身维持的消耗,从而形成矮小的植株。随着干扰程度的增加,光照强度的增加,使得植物最大光合速率增加,同时形成小而厚的叶片,增加叶倾角以防止强光伤害。植株密度是影响植物构型的另一主要因素。在清除植被的干扰样地中,由于高的植株密度使得树种形成较高的分枝率、大枝倾角、长枝条、窄小的树冠,以快速生长而摆脱受压状态。植物叶性状和构型与干扰样地恢复格局相对应,有效的解释了植被恢复机制。(8)对各干扰样地中长期发展预测,得出清除植被并去表土的干扰样地可能将比仅清除植被的干扰样地更早进入顶级群落阶段。这可能是由于土壤的贫瘠导致落叶树种高生长较为缓慢,而常绿萌生植株由于丰富的地下碳水化合物、矿物质营养的积累,保证其快速生长,从而可跨越常绿落叶混交林阶段而直接进入常绿阔叶林阶段。更多还原

【Abstract】 Evergreen broad-leaved forest （EBLF） is a zonal forest ecosystem of Eastern China. Under the long-term, frequent disturbance of human activities, most of EBLF have been deteriorated to many degradation types, such as secondary forests, secondary shrub communities, and shrub-grassland, even to bare lands. It is very important to learn the restoration process and mechanism of EBLF following different disturbance levels.The study site is located in Tiantong National Forest Park （TNFP, 29°53’N, 121°39’E）, Zhejiang Province, Eastern China, several kilometers inland from the East China Sea. Five 20 m×20 m plots, at 260m above sea level, with a 25-30°slope, were established within TNFP, in October, 2003. The main composition of the community was evergreen broad-leaved species of Fagaceae, Camellia, and Symplocaceae and was dominated by Schima superba, Castanopsis carlesii and Lithocarpus glaber. Four plots were disturbed by diversity treatments according to the common natural or artificial disturbance types of this area, and the other was free of disturbances. The four treatments were: PlotⅠ, removal of the aboveground canopy trees over 8 m, to simulate canopy gaps caused by selective logging or a typhoon; PlotⅡ, removal of vegetation that simulated clear-cutting; PlotⅢ, removal of vegetation, litter and the topsoil （0-10 cm） layer to represented landslides or mining disturbances; PlotⅣ, removal of the understorey vegetation below 8 m, which is standard forestry management practice. PlotⅤwas left undisturbed.Long-term monitoring investigations of floristic composition, community structures, and habitat factors were carried out sequentially （2006-2008） to clarify the restoration pattern and dynamics of vegetation in different degradation plots. From the invading, growing and regenerating stage, combining leaf traits and crown architecture of main woody species, the restoration mechanism of destroyed EBLF was tempted to discuss.The main results as follows:（1） Species richness of disturbed plots increased sharply during the 5 years after disturbance and was higher than the richness of the pre-disturbance plot. The richness increased exponentially in the early stage, reached the summit in the 3^rd year after disturbance, and followed the inflexion. The richness was higher in the plot with light disturbance.（2） The life-form was changed significantly in disturbed plots. The annual and perennial herb dominated in the 1^st year after disturbance. Wood species was maily composed of deciduous broad-leaved trees, whose numbers increased along disturbance levels. As the process of restoration, the stratification was formed with the decreasing domination of deciduous broad-leaved species and increasing domination of evergreen broad-leaved species. In the 5^th year after disturbance, Choerospondias axiliaris and Sassafras tzumu in the plot removal of vegetation and even removal litter and the topsoil reached the height of 6.4 and 7 m respectively.（3） On the base of previous research, according to the appearance and disappearanceof species, we divided the species in each destroyed plot into 4 species groups, residual species, disappeared species, invading species and once-appeared species. In the early stage of restoration, the species in heavy disturbed plots were mainly dispersed by wind, and the ratio of resprouting individual of evergreen broad-leaved trees was the highest. Due to the strong ability of resprouting, the climax sepceis appeared in the early stage of restoration.（4） According to the photosynthetic photon flux density, air and soil temperature and moisture, soil chemistry characteristics, and the restoration pattern following different disturbance levels, the destroyed plots could be divided to 4 types. 1)Accelerated regeneration （plotⅠ）, the evergreen broad-leaved species and shrub species understory grew rapidly after the remove of canopy layer. 2)Restrained regeneration （plot IV）, the remove of understory leaded to the regeneration of fern, but its predominance restrained the regeneration and growth of woody plants. 3)Progressive succession （plotⅡ）, perfect soil and light condition, abundant seed resources, resprouting and soil seed bank accelerated the succession. 4)Delayed succession （plotⅢ）, poor soil nutrient and destroyed soil seed bank limited some pioneer species distribution and growth, the restoration rate of vegetation was slowly. The 4 restoration types proved the multi-approach succession in this region.（5） The number dynamic, spatial distribution, and height-growth trajectories of 7 main tree species of the main species group, invading species and residual species, were studied to discuss mechanisms of pattern and dynamics of the initial stage of restoration. The invading species included decidous broad-leaved Litsea cubeba, Sassafras tzumu and Choerospondias axiliaris. The residual species included evergreen broad-leaved Schima superba, Lithocarpus glaber, Castanopsis carlesii and Castanopsis fargesii. The results shown that, the distribution and number of invading species were higher than residual species, which were related with seed mass and dispersal type. For residual species, the population deponded on the pre-disturbed population and the resprouting ability. The height gowth of invading species was higher than residual species.（6） Fast height growth was an important aspect of the dominantion at the early stage of restoration. Therefore, leaf traits （including the the maximum of net photosynthesis based on area （Amax）, specific leaf area （SLA）, leaf nitrogen and phosphor content （N, P）） and crown architecture of 7 main species were analysed to explain the height growth pattern via the light transform and capture. The results shown that, the decidous invading species had high ability of light transformation, and simple crown architecture, flat-shaped crown with low investment, while high invested in the branch growth. The acclimation to strong light condition ensured the dominance of deciduous broad-leaved species at the early stage of restoration. The evergreen residual species had low ability of light transformation, and complex crow architecture, deep crown with high investment, while low invested in the branch growth. The acclimation to shade condition made the slow height growth of evergreen broad-leaved species at the early stage of restoration, but it was the powerful instrument to become the dominant species or the understory companion species at the late stage of restoration.（7） The intensity and type of disturbance caused the change of resource availability, which affected the leaf trait and crown architecture. Light and soil nutrition were the main environmental fators. In light disturbed plot with shade condition, plant owned low Amax, large and thin leaflet, low bifurcation ratio, small branch and leaf angle to horizon, short branch and flat crown to enlarge photosynthetic area and cut down consume of self-maintenance, then forming the short individual. Along the disturbance level, light increased, and plant had higher Amax, small and thick leaflet and large branch and leaf angle to horizon, which benefited the fast growth and self-protection under strong light. Individual density was another factor affecting the crown architecture. In the plot of vegetation removal, the high individual density caused the higher bifurcation ratio, the larger branch angle to horizon, longer branch length and narrow crown, which benefited growing fast and increasing competitiveness for light. The correspondence of leaf trait, crown architecture and restoration type explained effectively the mechanism of restoration.（8） The middle-long term prediction of the future trajectory of each destroyed community shown that, the plot removal of vegetation, litter and the topsoil would enter the climax stage early than the plot only removal of vegetation. It might because the poor soil caused the slow growth of deciduous broad-leaved species, while the powerful accumulation of nutrition of the resprouting individual of evergreen broad-leaved species ensured the fast growth. It would make the destroyed vegetation span the deciduous and evergreen broad-leaved forest.更多还原