【作者】 商侃侃；

【导师】 达良俊；

【作者基本信息】 华东师范大学 ， 生态学， 2011， 博士

【摘要】 中国东部亚热带地区是孑遗落叶阔叶树种的主要分布区之一,大量种类残存并长期共存,受到自然和人为干扰的影响,生存现状恶化,种群更新和群落维持能力差,深入研究区域内大量孑遗落叶阔叶树种的共存机制,有助于对孑遗落叶阔叶树种尤其是珍稀濒危种类的保育和恢复提供实践指导,丰富我国亚热带山地植物多样性及保护生态学理论研究。本论文从地形-植被关系入手,通过调查测定天目山自然保护区孑遗落叶阔叶群落的分布类型、生境特征、种类组成、群落结构和植物叶性状,揭示微地形上孑遗落叶阔叶树种及其群落的分异格局,从生境异质性、植物性状的响应、种间关系和种群更新格局四个方面,阐明微地形上孑遗落叶阔叶树种分异格局的成因及其维持机制。主要结论如下：(1)孑遗落叶阔叶群落的分布格局在微地形上存在分异群落聚类和特征分析结果表明,天目山孑遗落叶阔叶群落在微地形上存在分异,具有各自主要的分布类型,形成地形顶极群落。青钱柳分布的范围最广,在海拔高度600～800 m范围内的谷床和谷坡中优势度相对较大；枫香在海拔高度600 m以下的坡地上最为丰富,谷床中次之；而同属的高海拔替代种缺萼枫香则在海拔高度800 m以上的坡地、谷坡和顶坡上都有较大优势；蓝果树在海拔高度800 m以上的谷头凹地、坡地占据较大优势；香果树则仅在海拔高度800 m以上的谷床和谷头凹地中占优势；领春木则仅分布在海拔高度1000～1200 m以上的谷床中。与山地垂直带植被带群落相比,孑遗落叶阔叶群落的分布、种类组成、群落结构和物种多样性均存在差异,多占据在谷床、谷坡、谷坡凹地、顶坡和陡坡等微地形单元上,既填补了常绿阔叶林未能占据的生境空间,也进入到坡地上地带性植被的林窗中,构成斑块状镶嵌的山地植被格局。(2)海拔和微地形单元是决定孑遗落叶阔叶群落分异的主要因子通过CCA分析孑遗落叶阔叶群落与地形因子间关系,结果表明群落分布受海拔的影响最大,其次为微地形单元,坡度和坡向的影响较小。随着海拔升高,群落的种类组成发生了明显变化,低海拔优势种枫香被缺萼枫香、香果树、蓝果树等替代,适应冷凉气候条件的常绿伴生树种交让木替代了细叶青冈、小叶青冈,壳斗科落叶乔木短柄袍替代低海拔的麻栎。微地形单元具有自身的地表特征,形成不同的地表干扰体系,阻碍植被的演替进程。坡度是影响滑坡、土壤侵蚀的重要因素,也是不同微地形单元的重要特征,通过滑坡使部分种类可以首先占据干扰后的生境,为孑遗落叶阔叶树种提供种群更新和维持的机会。(3)孑遗落叶阔叶树种间及与其它树种间存在空间和时间上的生态位分化孑遗落叶阔叶树种为环境变化后的残存类群,其分布的地形条件和资源空间存在差异,形成了一种特殊的生境偏好,多分布在特殊的不稳定生境中。香果树、领春木集中分布在沟谷中,蓝果树、缺萼枫香主要分布在顶坡和坡地上,生态位宽度较窄,树种间生态位重叠值较小,存在明显的分异格局,体现了空间分布上物种间的排斥性,是长期适应不同的微环境、利用不同资源空间的结果。蓝果树、缺萼枫香、枫香、香果树等多数种类为长寿命的先锋种,在干扰后可与短寿命的先锋种一起侵入到裸地生境。如果立地长期稳定,当短寿命的先锋种如雷公鹅耳枥、化香树等逐渐消退后,长寿命的孑遗落叶阔叶树种便得以成为优势种,在两者种间关系上多呈显著负关联关系,表明其生态位存在显著差异,是物种在群落演替上实现生态位互补的表现。随着演替的进程,孑遗落叶阔叶树种如坡地上的蓝果树、缺萼枫香,也为耐荫的常绿树种提供了庇护的场所,由于具有较长的寿命和高大的个体,可以在常绿树种不断占据优势的情况下长期处于群落的超高层,实现与常绿树种的共存,种间关系上呈显著正相关关系,体现了种群在垂直空间上的生态位分化。(4)微地形上优势种采取不同的更新策略和类型维持其种群及群落孑遗落叶阔叶树种部分种类选择长距离的扩散,在适宜生境中间歇型更新,如青钱柳、缺萼枫香等。部分种类因生境限制,在不断干扰下,选择母树周围的间歇型更新,如领春木、香果树。在相对稳定的微地形单元上,如坡地上,通过种子更新占据生境后,蓝果树、枫香等孑遗落叶阔叶树种通过固有的萌枝能力迅速扩大种群,形成径级大小相似的多主干植株,迅速占据优势地位；在不稳定的微地形单元上,如谷床、谷坡中,香果树、领春木、枫香等孑遗落叶阔叶树种种子更新受限,植株受到干扰造成损伤,常有个体枯死,通过其极强的萌枝更新能力补充零星的幼苗更新以及干扰造成的个体损伤。在相对稳定的立地下,由单株或少量林冠个体枯死形成小林窗导致的逐树替代是群落更新的主要机制。本区域低海拔常绿阔叶林区域因受到强烈的人为活动和自然干扰影响,常绿阔叶林破坏严重,缺乏种源,致使枫香林下常绿树种稀少,枫香种群以不连续的间歇型更新以及较强的萌枝能力,在各微地形单元上长期占据优势地位。中海拔地区,相对稳定的坡地、顶坡、谷头凹地上,蓝果树、缺萼枫香、香果树种群更新呈间歇型,以先锋种形式侵入林窗,而林下的小叶青冈、长叶石栎更新旺盛,在没有大规模干扰的情况下,坡地和顶坡上将继续向以逆-J字型的小叶青冈、长叶石栎为优势种的群落发展,而孑遗落叶阔叶树种以其长寿命特征处于群落的超高层；同时,由于该区域地形变化复杂,坡度较陡,易发生滑坡形成小面积的林窗,蓝果树、缺萼枫香可凭其长距离扩散能力,占据新生境。低山常绿阔叶林区域的谷床、谷坡中,紫楠种群更新呈逆-J字型,处于发展期,将取代青钱柳成为优势种；而青钱柳种群更新呈间歇型,且幼苗远离母树,在频繁地冲刷下形成青钱柳群落的斑块状更新。在中海拔的谷床中,由于频繁的干扰,小叶青冈、长叶石栎种群多处于较小径级处,且有枯死现象,缺少大径级个体,频繁的干扰阻止了常绿顶极树种的发展；而香果树为长寿命的高大阳生乔木,种群更新呈间歇型,具有较强的萌枝能力,在群落中长期占据优势地位;领春木种群更新也呈间歇型,幼苗的更新依赖于频繁的地表扰动,幼树、中树的成活率较高,且该年龄段植株的萌枝率也比较高,使其种群在相当长的时期内得以维持。(5)叶性状相似的树种对微地形单元具有相似的响应孑遗落叶阔叶群落主要阔叶乔木树种的叶性状受到微地形单元的影响最大,微地形单元通过改变土壤的养分条件和干扰体系,影响了树种分布及其对环境的适应能力。在不同微地形单元上呈现不同的格局,谷床、谷坡上占优势树种多具有较大的叶面积和比叶面积,较低的干物质含量,高氮含量；谷头凹地、顶坡、坡地上占优势树种的叶性状格局则相反,叶面积和比叶面积较小,干物质含量高,氮含量低；从谷床到顶坡,叶面积、氮含量呈减小趋势,干物质含量呈增大趋势。聚类和PCA分析结果表明,34个树种可以划分具有相似叶性状的4大类型,常绿树种除交让木外,多为具有小叶面积和比叶面积、低氮含量、高干物质含量特征的一类,与孑遗落叶阔叶树种间存在差异,多为坡地上群落的主要伴生种或优势种；落叶种类多具有叶面积和比叶面积大,氮含量高,干物质含量低的特点,较适宜在沟谷地形中生存。孑遗落叶阔叶树种及其主要伴生树种间的叶性状格局存在差异,青钱柳与多数叶面积较大的落叶树种刺楸、天目木姜子、玉铃花、黄山木兰等具有相似的叶性状格局；枫香、香果树、领春木、灯台树、八角枫等具有比叶面积大,干物质含量低,氮含量高的特点；蓝果树、缺萼枫香、短毛椴、交让木划分为一类；常绿树种与雷公鹅耳枥、短柄袍、鸡爪槭等叶面积小的落叶树种的叶性状较为相似。基于叶性状特征划分的类型与其分布的生境之间具有很好的对应关系,形成了不同的植物群落。(6)孑遗落叶阔叶树种的生态种组基于以上研究,将孑遗落叶阔叶树种划分为基于分布以及更新、适应、竞争策略的生态种组,可以划分为两类：生境填充种：包括领春木、青钱柳、香果树,主要特征表现为：在干扰频繁的沟谷区域占据优势地位,填补地带性植被构成种未能占据的生境空间,种群更新依赖于频繁的干扰并呈间歇型,可通过极强的萌枝能力补充、维持种群,种间竞争能力较弱。林窗修复种：包括蓝果树、缺萼枫香、枫香等,主要特征表现为：在干扰周期长的坡地林窗中占据优势地位,通过种子繁殖和无性繁殖迅速扩大种群,种群更新能力弱,依赖于远离母株的间歇型更新维持区域种群,与地带性植被构成种多为正相关关系,通过垂直空间上的生态位分化而共生。更多还原

【Abstract】 The subtropical area of East China is one of the most important refugia for survivors of Tertiary relict flora, therefore contains large number of relict deciduous broad-leaved trees. The capabilities of population regeneration and community maintenance were reduced due to the natural and anthropogenic impact. Hence, the coexistence mechanism of relict deciduous broad-leaved trees in local area should be further studied to provide practical guidance for conservation and restoration of relict deciduous broad-leaved trees especially the rare and endangered species, and enrich the research on theory of mountain plant diversity and conservation ecology in the subtropical evergreen forests area of China.The distribution type, habitat characteristics, floristic composition, community structure and plant leaf traits of relict deciduous broad-leaved forests have been studied in this paper. It could reveal differentiation pattern of relict deciduous broad-leaved trees and communities along micro-topographic gradient. Furthermore, it would clarify the cause of differentiation pattern and their maintenance mechanism by the analysis of habitat heterogeneity, response of plant trait, inter-specific interaction and population regeneration pattern. The main conclusions are as follows:(1) Differentiation pattern of relict deciduous broad-leaved forest along micro-topographic gradient.The results of cluster analysis and characteristic depiction of communities indicated that spatial distribution of relict deciduous broad-leaved trees was different among micro-topographic units. They were dominated at each site and formed topographic climax community. Cyclocarya paliurus was widely distributed and dominated on river bed and valley slope between 600 to 800 m a.s.l.. The abundance and dominance of Liquidambar formosana was higher on sideslope and river bed below 800 m a.s.l.. Above 800 m a.s.l., L. acalycina was dominanted on sideslope, valley slope and crest slope, Nyssa sinensis was on head hollow and sideslope, and Emmenoptery henryi was on river bed and head hollow. Euptelea pleiospermum was only located on river bed between 1000 to 1200 m a.s.l.. Compared with the altitudal zonation of mountain vegetation, the spatial distribution, floristic composition, community structure and species diversity of relict deciduous broad-leaved forests were significantly different. They were mainly distributed on specific unstable habitat and supplied for bare habitat that evergreen broad-leaved forest was hardly occupied.(2) Altitude and micro-topographic units were the main factors that determed the community differentiation pattern.The result of CCA analysis indicated that the community distribution pattern was significantly affected by altitude and micro-topographic units. The effects of slope and aspect were not significant. The floristic compostion and dominant species changed significantly along the altitude. Low-altitude dominant species L. formosana was replaced by L. acalycina, E. henryi, N. sinensis at high altitude. The main companion species Cyclobalanopsis gracilis and Cyclobalanopsis myrsinifolia were replaced by Daphniphyllum macropodum, and Quercus acutissima was replaced by Quercus serrata var. brevipetiolata. Micro-topographic units have their own surface characteristics which contributed to different disturbance regimes. The disturbance regimes would hinder the process of vegetation succession. Slope was the most important factor that affects landslide and soil erosion, and an important characteristic of each micro-topographic unit as well. This could give the opportunity for population regeneration and maintenance of relict deciduous broad-leaved tree due to the landslide.(3) Niche differentiation among relict deciduous broad-leaved trees and other trees at spatial and temporal scales.The topographic characteristics and spatial distribution pattern of relict deciduous broad-leaved trees were different. They had a specific habitat preference and were mostly distributed at unstable habitat. E. henryi and E pleiospermum were located on valley habitat while N. sinensis and E. acalycina mainly located on crest slope and side slope. Their niche breadth was narrow and their niche overlap was smaller so that the differentiation pattern was significant. Hence, it reflected the exclusion of species spatial distribution, which resulted from species’long-term adaptation to micro-environment and utilization to different resources. N. sinensis, L. acalycina, L. formosana and E. henryi were a long-lived pioneer species. They could invade into the bare habitat after disturbance that accompanied with short-lived trees. If the habitat were long-term stable after once disturbance, long-lived relict deciduous broad-leaved trees would become dominant species when the short-lived pioneer species such as Carpinus viminea, Platycarya strobilacea disappeared gradually. The relationship among these different pioneer species was significantly negative. It indicated that their niche was a significant difference and represented the niche complement of species on the process of community succession. Besides, long-lived relict deciduous broad-leaved trees N. sinensis and L. acalycina would provide a shelter for evergreen trees during the process of community succession. They were coexisted with evergreen tree due to its tall stature and long life span. Their relationship appeared significant positive relationship. This reflected that the vertical niche differentiation between relict species and evergreen trees.(4) The persistence of population and community depend on different reproduction strategy and regeneration pattern at different micro-topographic unitsSome relict species such as C. paliurus and L. acalycina regenerated discontinuously at safe site via long-distance diffusion. And E. heryi and E. pleiospermum regenerated discontinuously around mature tree under frequent disturbance. After occupied by sexual regeneration, N. sinensis and L. formosana could regenerate and form multi-stems individuals by inherent sprouting ability at relative stable sites. At river bed and valley slope habitat, E. henryi and E. pleiospermum, L. formosana also could be recruited by strong sprouting ability due to sparse seedling and loss incurred by disturbance.At low altitude, evergreen broad-leaved forests were damaged seriously under natural and artificial disturbance so that there were few evergreen seedlings. Therefore, L. formosana would predominate for long-term at each micro-topographic unit by the sporadic regeneration and strong sprouting ability. At middle altitude, N. sinensis, L. acalycina, L. formosana and E. henryi were regenerated discontinuously while the regeneration type of C. gracilis and Lithocarpus harlandii displaced an inverse-J type on the relative stable habitat. The evergreen trees would predominate gradually and long-lived relict species only existed at emergent layer. And N. sinensis and L. acalycina also could occupy new habitat via long-distance diffusion when forest gaps were formed.At lower mountain evergreen broad-leaved forest area, the population of Phoebe sheareri was regenerated well and would replace the first dominant species on river bed and valley slope. However, C. paliurus could regenerate well at mosaic community level by virtue of sporadic regeneration far away from mature trees. On river bed at middle altitude, the size classes of dominant evergreen species C. gracilis and L. harlandii were smaller and some individuals died due to the frequent disturbance. E. henryi would predominate long-term by virtue to sporadic recruitment and strong sprouting ability. The regeneration of E. pleiospermum population depended on frequent disturbance and displaced a sporadic type. Furthermore, the survival rate and sprouting rate of saplings and young trees were higher. Thus E. pleiospermum population could persist for a long period.(5) The response of trees with similar leaf traits to micro-topographic units was unanimous.Micro-topographic units were the greatest factor that affects the leaf traits of main broad-leaved trees. It affected the distribution of tree and their adaption ability via changing the soil nutrition and disturbance regime. The leaf trait characteristics of dominant trees located on river bed and valley slope were larger leaf area and specific leaf area, lower leaf dry matter content, higher nitrogen content. And the dominant trees located on head hollow, crest slope and side slope have smaller leaf area and specific leaf area, higher leaf dry matter content, lower nitrogen content. From the river bed to crest slope, leaf area and nitrogen content showed a decreasing trend, while leaf dry matter content tended to increase.The results of cluster and PCA analysis showed that 34 trees can be classified into 4 types based on the similar leaf traits. Evergreen trees except for Daphniphyllum macropodum had the characteristics of lower leaf area, specific leaf area and nitrogen content, and high leaf dry matter content. They were mainly located on side slope and became the main companion species or dominant species. Deciduous trees mainly adapted on valley habitat and their leaf traits characteristics were larger leaf area, higher specific and nitrogen content and lower leaf dry matter content. C. paliurus has a similar leaf traits pattern with a large number of deciduous trees such as Kalopanax septemlobus, Litsea auriculata, Styrax obassius, Magnolia cylindrical. The leaf traits characteristics of L. formosana, E. henryi, E. pleiospermum, cornus controversum and Alangium chinense were also similar. N. sinensis, L. acalycina, Tilia breviradiata and D. macropodum were the third type. Evergreen tree and smaller leaf area deciduous trees such as Carpinus viminea, Quercus serrata var. brevipetiolata and Acer palmatum were the fourth type. There was a good correspondent relationship between the species group types based on leaf trait characters and their distribution patterns.(6) Ecological species group of relict deciduous broad-leaved tree in subtropical area of East China.The relict deciduous broad-leaved trees could be classified into two ecological species groups based on spatial distribution and strategy of regeneration, adaptation and competition.Type 1 was species that supplement for bare habitat, such as E. pleiospermum, C. paliurus, E. henryi and L. formosana. They were characterized by predominating on valley habitat with frequent disturbance, unimodal distribution type, strong vegetative reproduction ability, and lower interspecific competition.Type 2 was species that repairment for forest gap, such as N. sinensis, L. acalycina, L. formosana. They were characterized by predominating on side slope with long period disturbance, regenerated by sexual and vegetation reproduction, persisted by discontinuously regeneration that far away from mature trees, and the vertical niche differentiation with other trees.更多还原