【作者】 张忠华；

【导师】 倪健；

【作者基本信息】 华东师范大学 ， 生态学， 2011， 博士

【摘要】 贵州茂兰的喀斯特森林是一类特殊的森林生态系统,其顶极群落为常绿落叶阔叶混交林,是当今同纬度带上具有重要研究价值的非地带性植被。茂兰喀斯特森林生境类型特殊,物种组成丰富,群落结构复杂,从而为研究喀斯特地质背景下的生态学问题提供了理想场所。本研究在茂兰喀斯特森林国家级保护区，用DQL-1型森林罗盘仪建立两个1hm2 (100mx100m)样地(分别命名为P1和P2),并将每个样地划分为100个10m×10m的样方调查单元,对每个样方内所有DBH≥1cm的木本植物的种名、个体相对坐标、胸径和树高等进行了调查,采用优势度指数、O-ring统计、多样性指数、Godron稳定性测定、种间分离指数、地统计学以及TWINSPAN分类与DCCA排序等统计分析方法,对喀斯特森林生态系统的种群生态学与群落稳定性进行了系统分析,以期为西南喀斯特森林植被迅速恢复和生态重建提供重要的理论参考与科学依据。主要结论如下：1.茂兰喀斯特森林群落的总体特征P1样地生境异质性较高,岩石裸露率高达85%,坡度较大,土壤浅薄呈微碱性,样地内DBH≥lcm的木本植物共有199种,4281个独立个体,隶属于63科140属,主要以圆果化香、天峨槭、齿叶黄皮、紫弹朴、青冈、云贵鹅耳枥、短序荚蒾和皱叶海桐等物种占优势；P2样地包括东南和东北两个坡向,平均坡度30°,岩石裸露率为45%,土面相对较多,土壤为微酸性至中性。样地内共有木本植物有191种,3857个独立个体,隶属于58科121属。群落主要以西南米槠、细叶青冈、杨梅叶蚊母树、鹿角杜鹃、桂花、圆果化香、黄杞和云贵鹅耳枥等物种占优势。两个样地区系组成均以热带区系成分为主,反映了样地的热带亚热带性质。其物种组成以常绿成分为主,但落叶成分也占一定比例,说明了常绿落叶阔叶混交林是亚热带喀斯特森林群落的主体。两个群落的外貌主要由中小型革质、单叶为主的常绿中、小高位芽植物所决定。群落垂直结构复杂,成层现象明显,两个样地内所有木本植物径级分布呈倒“J”形,群落更新良好,处于稳定状态。2.茂兰喀斯特森林木本植物潜在关键种的确定和关键种的结构与空间格局采用物种叶特性和生活型两个功能性指标对物种进行了功能群划分,并在功能群框架下运用优势度指数法进行了关键种的确定。结果表明,除了常绿乔木功能群和落叶乔木功能群可能存在多个潜在关键种外,在常绿灌木功能群、常绿藤本功能群、落叶灌木功能群和落叶藤本功能群采用优势度指数法划分出的关键种较为明显。采用O-ring统计对样地中主要关键种进行结构和格局研究,发现大部分物种具有丰富的幼树储备,能够维持其良性的自我更新,呈稳定生长状态。两个喀斯特森林的主要关键种在大部分尺度上呈显著聚集分布,种间关联以负关联种对为主,正关联种对只有5对。结果表明,喀斯特森林生境的复杂性和异质性,特别是海拔和岩石裸露率的变化在决定喀斯特物种的空间分布格局和物种关联中扮演了重要角色。因此,主要关键种在高度异质资源位上的分化有助于促进喀斯特森林的多物种共存和群落的稳定性。3.茂兰喀斯特森林物种多样性与群落稳定性茂兰喀斯特森林物种组成丰富,其物种多样性指数较高。两个样地的物种多样性不仅具有尺度依赖性特征,同时也表现出较强的区域性分布特征,且这种区域性特征与取样尺度有关。物种多度的方差随着尺度的增加呈线性增加,而丰富度是单峰型的；物种丰富度和多度的变异系数则随空间尺度的增加而下降,生境异质性在茂兰喀斯特森林群落结构构建中起了很大作用。通过测定群落的稳定性指标,发现两个森林群落的交点坐标均非常接近于20/80的稳定交点,表明两个森林群落处于一个相对稳定的状态。两个样地具有较高的物种多样性,也在一定程度上体现了群落的稳定性。4.茂兰喀斯特森林群落的种间分离特征以建立的2块样地群落学调查数据为基础,借助ArcGIS软件的空间分析功能,判定每个个体的最近邻体植株的种类与距离。在此基础上,采用N×N最近邻体列联表及其截表的方法,应用Pielou的分离指数量化了2块样地中各43个树种(多度≥20)的种间分离状况。两种喀斯特森林群落类型中物种均以随机毗邻种对占优势(P1和P2样地分别为60.91%和63.34%),正分离种对次之(分别为38.76%和35.66%),负分离种对极少(分别为0.33%和1.0%),这种种间分离特征表明种间竞争排除作用减弱,群落已趋于稳定,反映出该森林正处于相对稳定的顶极状态。根据种间分离情况以及物种对环境的适应方式,将两个样地各43个物种分别划分为3个生态种组,各组间物种的生态学特性以及对生境的偏好存在明显差异。种间的分离特征与喀斯特森林高度的生境异质性明显相关,分布在不同生境类型上的物种间大多呈现正分离,而具有相似生境要求或分布广泛的物种间易形成随机毗邻或负分离,这一特征为群落中多物种的稳定共存提供了更大的可能性。因此,以生境的高度分化为基础的种间关系可能是喀斯特森林多物种稳定共存的重要机制之一。5.喀斯特森林土壤养分的空间特征及植物营养元素含量分析利用经典统计学和地统计方法分析了茂兰两个1hm2喀斯特森林土壤养分的空间变异特征。结果表明,两个研究样地土壤养分含量总体较高,其中以P1样地含量最高。两个样地大部分养分指标都表现为中等程度变异。半方差分析发现两个样地土壤养分指标均具有良好的空间自相关性,土壤养分呈现差异显著的斑块状分布格局,不同的样地空间变异特征不同。地形、高异质性的微生境和植被是造成研究样地土壤养分格局差异的主要因素。其中,地形是造成两个样地土壤养分时空变异及其分布差异的重要影响因素。两个样地主要植物叶片营养元素表现为Ca>K>Mg,表明喀斯特地区植被具有明显的高钙特征。两个森林主要物种的叶片元素与土壤元素含量呈现一定的相关关系,表明植物营养元素含量的差异受土壤元素含量的影响。6.喀斯特森林植被梯度分析及环境解释利用TWINSPAN分类法,将两个喀斯特森林样地分别划分为4种群落类型。P1样地沿DCCA第一轴从左到右沿空间因子的增大,土壤主要养分逐渐降低,森林群落由具有一定耐荫的树种过渡到喜光耐旱树种为主的原生林。P2样地沿DCCA第一轴从左到右随海拔的上升,坡向逐渐由阳坡过渡到阴坡或半阴坡,岩石裸露率、土壤主要养分和pH逐渐降低,植物群落出现了由耐旱喜光的树种逐步向喜湿耐荫树种为主的原生林变化的格局。植被与环境关系的研究发现,生态位分化在喀斯特森林物种共存中扮演了重要的作用,从而保证了喀斯特森林群落的稳定性。更多还原

【Abstract】 Karst forest in Maolan of southeastern Guizhou is a specific forest ecosystem. The mixed evergreen and deciduous broadleaf forest is an azonal climax community in the karst area, which has the important research value in the field of azonal vegetation at the same latitude in China or even in the world. This forest has the specific habitat, complex community structure and rich biodiversity, providing an ideal place for ecological study under the karst geological background. The two 1 hm2 (100m×100m) plots were set up using the DQL-1 forest compass in Maolan National Nature Reserve. Each plot was divided into 100 contiguous 10m×1Om quadrats. All free-standing woody plants, including lianas and vines, with≥1 cm diameter at breast height (DBH) were investigated. The species names, relative location of each individual, DBH, height, crown width (the greatest diameter of the vertical projection of the crown in two directions, i.e. north-south or east-west), survival status (living or dead) and microhabitat (e.g. soil surface, rocky surface, rocky gully, rocky-soil surface, and rocky crevice) were recorded The paper analyzed the population ecology and community stability of karst forest using statistics method such as dominance index, diversity index, Godron method, O-ring statistics, the Pielou’s coefficient of segregation, Geostatistic, TWINSPAN and DCCA. These would provide important theoretical guide to quick vegetation recovery and ecological restoration in karst forest of southwestern China. The main results are as follows:1. The general characteristics of old-growth karst forests communities in MaolanThe species composition and population structure were investigated in karst old-growth forest in Maolan National Nature Reserve. The topography of P1 plot is complicated and heterogeneous. It is located in Dongge site on a steep southeast-facing slope, rock outcrops occur on almost the entire plot (ca.85%of the ground surface). The soils are slightly alkaline and shallow. There are 4281 genotype individuals, belonging to 199 species,140 genera and 65 families in P1 plot. There are mainly Platycarya longipes, Celtis biondii, Acer wangchii, Clausena dunniana, Cyclobalanopsis glauca, Carpinus pubescens, Viburnum brachybotryum and Pittosporum crispulum. In the P2 plot, two slopes facing the southeast and the northeast, respectively, are included. The topography is only gently sloping in the lower and higher altitudes, and rather moderate or steep at middle altitude. The mean slope is ca.30°. Relatively fewer outcrops occur in this plot, and the rocks occupy mainly in mid-lower part of the plot. The soils are slightly acidic to neutral and relatively thick. There are 3857 genotype individuals, belonging to 191 species,121 genera and 58 families in P2 plot. It is dominated by Castanopsis carlesii var. spinulosa, Cyclobalanopsis myrsinaefolia, Platycarya longipes, Distylium myricoides, Rhododendron latoucheae, Osmanthus fragrans, P.longipes, Engelhardtia roxburghiana and C. pubescens. Its floristic composition is mainly tropical floristic elements dominated in the community, reflecting the tropical and subtropical nature. The evergreen element in the two communities is dominant, but deciduous leaf element is also in a certain proportion, which indicates that the mixed evergreen-deciduous broad-leaved forests are the main climax community in Maolan karst region. Community physiognomy was characterized mainly by mixed evergreen and deciduous broadleaf mesophaenerophytes and microphanerophytes with small-sized, single, leathery leaves. The vertical structure of the forest is clear; there are three layers from the top of the canopy to the ground floor, two tree layers, one shrub layer and one herb layer. The structure of DBH size class of all species in the two plots generally appears reverse "J" shape, which indicates successful community regeneration. The spatial distribution patterns of six dominant species in the two plots are generally aggregated in different spatial scales and varied with the DBH size classes.2. Identification of the woody plant key-stone species and the structure and spatial pattern of the key species in karst forest of MaolanBased on investigation of two plots in a karst forest, we classified woody plant functional groups based on leaf trait and life form. Keystone species within each functional group were identified using a dominance index (DI). The result showed that identification of keystone species within evergreen shrub, evergreen liana, deciduous shrub and deciduous liana functional groups were clearer than within evergreen tree and deciduous tree functional groups.The O-ring statistics were used to characterize the spatial patterns and interspecific associations of main dominant tree species in two 1-ha old-growth karst forest plots in Maolan National Natural Reserve, southwestern China. We found that most of twelve key tree species in two forests were continuously regenerating populations. Nine species (Platycarya longipes, Acer wangchii, Clausena dunniana, Viburnum brachybotryum, Cyclobalanopsis glauca, Castanopsis carlesii var. spinulosa, Distylium myricoides, Rhododendron latoucheae and Platycarya longipes) exhibited significantly aggregations at the majority of scales while others (Celtis biondii, Cyclobalanopsis myrsinaefolia and Carpinus pubescens) showed a random distribution pattern at most scales. Negative association was a dominant pattern for most species pairs in the two plots, while positive associations were found at most scales for only five species pairs. Results also indicated that the two main factors of habitat complexity and heterogeneity-the elevation and rock-bareness rate-play important roles in determining spatial distribution patterns and interspecific associations of tree species in karst forests of Maolan. Thus, the observed spatial patterns among the twelve tree species are influenced by habitat heterogeneity in the context of karst topographical variations. The partitioning of habitat niches contributes to the promoting species coexistence and stability of communities in species-rich karst forests.3. Species diversity and community stabillity in Maolan ksrst forestKarst forest in Maolan has rich biodiversity and the two plots have higher diversity index. This study analyzes the effect of spatial scale on species abundance and richness in two 1-ha karst forest plot in the Maolan, southwest China. The result showed that species abundance and richness depend not only on spatial scales, but also on study area, and such a regional pattern was scale-dependent. Variance of the species abundance increased with increasing scale, while variance of the species richness was unimodal with increasing scale; the coefficient of variation of species abundance and richness decreased with increasing scale. Habitat heterogeneity played an important role in construction of forest community structure. Community stability of two karst forest was studied by using the Godron method. The cross points between the species proposition lines (x) and accumulation relative frequency lines (y) were located close to the stabilizing point (20/80), indicating a typical stability state of the two forest communities. Two plots with rich species diversity, to a certain extent, reflect also the stability of communities.4. Interspecific segregation of old-growth karst forests in MaolanThe distribution map of 43 trees with abundance≥20 individuals from two karst forest communities were drawn using the GIS software (ArcGIS). The nearest neighbors of each individual and the distances between every individual-neighbor pair were obtained by using ArcGIS’s extension module. The interspecific segregation in the multi-species community was then studied with a sub-table method of an N×N nearest-neighbor contingency table. The Pielou’s coefficient of segregation (S) was adopted to measure the segregated degree between two species. The results show that segregation relations between most of the species are random in two karst forests communities (60.91%and 63.34%, respectively). Some species pairs are positively segregated (38.76%and 35.66%, respectively) and a few pairs are negatively segregated (0.33%and 1.0%, respectively). Our results support the Pielou’s opinion that negative segregation is rare in old-growth plant communities. This showed that interspecific competitive exclusion is weakened between the species, and the two forests were at a stable climax stage. According to their adaptability to the environment and relationships between plants and environment, the 43 species from two forest plots were divided into three ecological species groups. The ecological characteristics and habitat preference of the species in each group showed significant differences. The results also indicated that interspecific segregation is closely related to habitat heterogeneity of karst terrain. Species pairs in different habitats mostly tend to be more positively segregated, but species with similar habitat preference or widely distributed are more likely to be random neighbor or negatively segregated. Therefore, interspecific relationship based on differentiation of habitat may be one of the important mechanisms of species coexistence in species-rich karst forest.5. Spatial heterogeneity of soil nutrients and nutrient element contents in plants in Maolan karst forestClassic statistics and geostatistic was used to study the spatial variability of soil nutrients in two karst forest in Maolan. The results showed that the quantity of soil nutrient are high both the plots, and the highest nutrient content was P1 plot. The most of soil nutrients showed moderate variation in both the plots. Analysis of semi-variograms revealed that soil nutrient content had good spatial autocorrelation in both the plots, clear patches with well continuum, but its spatial heterogeneity differed. Topography, high heterogeneity of micro-habitat and Vegetation were the main fators caused the differences of the spatial distribution patterns of soil nutrients in the Reserve, and topography was the important influencing factors on the spatial and temporal variability and distribution patterns of soil nutrients of the two karst forest plots. The element contents of plant of two plots are characterized as being of "Ca>K>Mg" type, indicating that the plants of karst area have the characteristic of high concentration of Ca. The obvious relationship was found between the plant elements and soil nutrient contents in two forests, indicating the nutrient contents in the plant was affected by the siol conditions, and meanwhile, is the result of long-term adaptive evolution in the special karst habitat.6. Gradient analysis and environmental interpretation of woody plant communities in Maolan karst forestThe two forest communities were classified into 4 eco-types, respectively, by TWINSPAN. In plot P1, along the first DCCA axis, the pattern of communities is from primary sub-climax forest with shade-tolerant plants towards primary climax forests with shade-intolerant and drought resistance plants, an increase of topography factors and a steady decline in major soil nutrients. In plot P2, along the first DCCA axis, the pattern of communities is from primary forest with shade-intolerant and drought resistance plants towards primary forests with shade-tolerant plants, accompanying a shift from sunny to shady or semi-shady slopes, an increase of elevation, a steady decline in the ratio of bare rocks in the ground cover and major soil nutrients. Through the study of relationships between vegetation and its environmental variables, niche differentiation mechanism may play a key role in maintenance of species diversity in Maolan karst forest, thus ensuring the stability of karst forest communities.更多还原