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1.
The extant and potential (seed bank) vegetation of a rare maritime holly forest on Fire Island, New York was described to assess whether treefall gaps act as a mechanism for the persistence of the species composition of this plant community over time. The Sunken Forest overstory is dominated by Ilex opaca, Amelanchier canadensis and Sassafras albidum. A survey of canopy gaps indicated canopy openings compose 11.3% of the land within the Sunken Forest (16 ha). The composition and density of the seed bank were described using the emergence method. Germination from soil samples placed in the greenhouse was monitored over 2 years. Sixteen species germinated with an average propagule density of 215±41 germinants per square metre. An early successional species (Rhus copallinum) dominated the seed bank, but the late-successional, shade-tolerant I. opaca was also present. Though only one species in the seed bank did not appear in the current vegetation, species abundance differed between vegetation strata. The mean cover and density of the ground-layer flora were higher beneath treefall gaps than closed canopy. Sapling density did not differ between the two canopy conditions, but the dominant species differed with A. canadensis occupying several closed canopy plots and P. serotina saplings appearing more often in gap plots. Most of the dominant canopy species are present in the seed bank and ground layer but are not present in the shrub and sapling layer, with the exception of A. canadensis. Current (2002) sapling density is lower than three decades ago for all species except P. serotina, which is now the dominant woody species in the Sunken Forest understory. The results of this study indicate that if the cause of the sapling reduction is lessened or removed, the characteristic species of the overstory of this unusual plant community may rebound and redevelop a sapling and shrub layer akin to that present before the increase in Odocoileus virginianus on the island.  相似文献   

2.
Forest succession can influence herbivore communities through changes in host availability, plant quality, microclimate, canopy structure complexity and predator abundance. It is not well known, however, if such influence is constant across years. Caterpillars have been reported to be particularly susceptible to changes in plant community composition across forest succession, as most species are specialists and rely on the presence of their hosts. Nevertheless, in the case of tropical dry forests, plant species have less defined successional boundaries than tropical wet forests, and hence herbivore communities should be able to persist across different successional stages. To test this prediction, caterpillar communities were surveyed during eight consecutive years in a tropical dry forest in four replicated successional stages in Chamela, Jalisco and Mexico. Lepidopteran species richness and diversity were equivalent in mature forests and early successional stages, but a distinctive caterpillar community was found for the recently abandoned pastures. Species composition tended to converge among all four successional stages during the span of eight years. Overall, our results highlight the importance of both primary and secondary forest for the conservation of caterpillar biodiversity at a landscape level. We also highlight the relevance of long‐term studies when assessing the influence of forest succession to account for across year variation in species interactions and climatic factors. Abstract in French is available with online material.  相似文献   

3.
林窗是森林更新演替的重要环节, 揭示林窗环境下功能性状变异来源及其相对贡献, 有助于阐明植物对林窗环境的响应。该研究以中亚热带格氏栲(Castanopsis kawakamii)天然林为对象, 设置9个不同大小的林窗样地, 运用方差分解探讨林窗、物种和个体对叶性状变异的相对贡献, 采用线性回归分析不同大小林窗下群落性状变化及种间和种内性状变异的重要性。研究发现: (1)格氏栲天然林林窗植物比叶面积、叶干物质含量、叶厚和叶绿素含量由种间性状变异主导, 叶氮含量由种内性状变异主导, 叶磷含量受林窗大小影响最大。(2)群落叶磷含量与林窗大小具有显著正相关关系, 土壤温度和水解氮含量对群落叶磷含量具有显著正效应, 土壤有效磷含量具有显著负效应。(3)沿林冠开放度的群落叶磷含量变化主要由种内性状变异引起, 优势种扮演着重要角色。结果表明, 格氏栲天然林林窗环境下植物功能性状仍以种间性状变异为主(平均41%), 但沿林窗环境梯度的群落性状变化主要源自种内性状变异, 通过植物表型可塑性响应环境改变, 优势种作用明显。  相似文献   

4.
重庆缙云山针阔混交林林隙树木更替规律研究   总被引:24,自引:1,他引:23       下载免费PDF全文
 研究了重庆缙云山大面积分布的亚热带次生性针阔混交林林隙树木更替规律,预测了该类型林林隙演替趋势。结果表明:马尾松(Pinus massoniana)种群表现出强烈的相互更替模式,四川大头茶(Gordonia acuminata)、四川山矾(Symplocos setchuanensis)等常绿阔叶树种自我更替与相互更替两种模式共存;林隙现实树木更替过程不能维持群落现有组成;Markov转移矩阵分析表明未来林冠层组成中马尾松种群将失去优势地位,整个群落将由针阔混交林向常绿阔叶林方向演替。  相似文献   

5.
Researchers studying forest edge effects in fragmented landscapes have begun to move beyond merely documenting changes along the edge itself to examining the dynamic influences that edges may have on processes in adjacent areas. One such "edge-mediated effect" is the influence that edges may have on canopy gap replacement processes within the forest interior by acting as seed sources for shade-intolerant plant species. In this paper, we coupled analyses of woody species composition in gap and non-gap areas within the interior of an Ohio hardwood forest with a simple cellular automata model of forest dynamics. Non-gap composition was primarily correlated with disturbance history and site conditions (topographic position and slope) while a comparable analysis using a 24-year time series of composition in gaps showed that gap composition was related most strongly to the proximity of edge communities for the first 10–15 years. However, after 15–20 years of gap succession, composition was correlated with essentially the same variables and to the same degree as non-gap vegetation, suggesting that the influence of edge proximity on interior stand dynamic processes was transient. These results were used to develop a simple mathematical model of stand dynamics that showed that losses of interior forest area may be much greater than typically predicted by core-area models, which do not consider dynamic, edge-mediated effects. Further, our findings suggest the importance of considering disturbance interval in mediating edge-interior relationships, particularly as it may interact with forest size and shape.  相似文献   

6.
Treefall gaps play an important role in tropical forest dynamics and in determining above-ground biomass (AGB). However, our understanding of gap disturbance regimes is largely based either on surveys of forest plots that are small relative to spatial variation in gap disturbance, or on satellite imagery, which cannot accurately detect small gaps. We used high-resolution light detection and ranging data from a 1500 ha forest in Panama to: (i) determine how gap disturbance parameters are influenced by study area size, and the criteria used to define gaps; and (ii) to evaluate how accurately previous ground-based canopy height sampling can determine the size and location of gaps. We found that plot-scale disturbance parameters frequently differed significantly from those measured at the landscape-level, and that canopy height thresholds used to define gaps strongly influenced the gap-size distribution, an important metric influencing AGB. Furthermore, simulated ground surveys of canopy height frequently misrepresented the true location of gaps, which may affect conclusions about how relatively small canopy gaps affect successional processes and contribute to the maintenance of diversity. Across site comparisons need to consider how gap definition, scale and spatial resolution affect characterizations of gap disturbance, and its inferred importance for carbon storage and community composition.  相似文献   

7.
Figueroa  Javier A. 《Plant Ecology》2003,166(2):227-240
Canopy gap and chilling requirements for seed germination were assessed in 61 and 44 species, respectively, in the temperate rain forest of southern Chile. Germination assays within canopy gap and understorey were carried out under natural conditions. Germination tests in cold stratified and non-stratified seeds were performed under laboratory conditions. Seeds were collected of common trees, shrubs, vines and perennial herbs of forests in southern Chile. Final percent germination was significantly enhanced under canopy gap conditions in 19 species, and significantly reduced in 11 species. Germination proved indifferent under gap vs. understorey conditions in half the species tested. Cold stratification affected germination in 11 species: significantly increasing final germination of four species, and significantly decreasing final percent germination of seven species. A Principal Components Analysis (PCA) was applied with the purpose of identifying groups of species with similar germination strategies. Four attributes were included in the PCA: final germination percentage in canopy gap, germination rate in the laboratory, and gap-and chilling-dependency indices (EGAP and STRAT, respectively). The first axis separated species mainly on EGAP variation while the second axis separated them mainly according to STRAT variation; the two axes together explaining 73% of the among-species variation. A small group of trees and vines germinating best in the understorey and neutral to chilling could clearly be distinguished from the remaining species analyzed. Multifactorial ANOVAs were used for evaluating the combined effect of successional status, seed mass, dispersal period, life form, phylogenetic categories, and dispersal syndrome on EGAP and STRAT variation. The EGAP value of secondary successional species proved significantly greater than that of primary successional species and species with endozoochorous seed dispersal were significantly less dependent on chilling (according to STRAT values) compared to species with mainly wind-dispersed seeds. The possible implications of these results for seedling establishment are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

8.
不同演替阶段鼢鼠土丘群落植物多样性变化研究   总被引:14,自引:2,他引:14  
用空间序列代替时间序列的方法对高寒草甸不同演替阶段高原鼢鼠土丘植物群落的物种组成和多样性变化进行了研究.结果表明,不同演替阶段鼠丘植物群落的物种组成及外貌特征与原生植被(对照)之间存在较大差异.在演替的早期阶段,r对策者如萼果香薷、灰绿藜、鹅绒委陵菜、细叶亚菊等演替先锋种在群落中占相对重要地位.随着演替的进展,k对策者如长毛风毛菊、垂穗披碱草、甘肃嵩草、线叶嵩草等在群落中的比例增加.α多样性分析表明,随着演替的进展,群落物种丰富度指数(O)显著增加,其排列顺序为:阶段1<阶段2<阶段3<阶段4<原生植被;均匀度指数(Pielou均匀度指数)的变化趋势与丰富度指数相同;多样性指数(Simpson指数D和Shannon-.Wiener指数H’)按群落的演替梯度呈增加趋势.卢多样性分析表明,阶段1与原生植被及阶段1与阶段4植物群落物种组成的相似系数最小,为0.18;阶段1与阶段2植物群落物种组成的相似系数最大,为0.62.同时,群落生活型功能群组成也随鼠丘的演替进展而发生变化,反映出不同演替阶段的鼠丘植物群落和微生境都发生了改变.  相似文献   

9.
采用典型样地法,以川西周公山柳杉人工林5种不同大小的林窗为研究对象,以林下非林窗为对照,研究了不同大小的林窗对柳杉人工林物种多样性的影响,同时分析了不同梯度林窗下林窗中心、林窗边缘、及林下群落的物种组成、物种多样性的变化情况。结果表明:(1)在所调查的18个样地231个样方中共记录到维管束植物141种,隶属于76科113属;随着林窗面积的增大,群落各层次的物种数呈现出先升高后降低的趋势,灌木层物种数在各林窗梯度上表现为林缘林下林窗中心,草本层物种数在各林窗梯度上表现为林缘林窗中心林下。(2)不同林窗优势种及其重要值不同,即在小林窗内,优势种为柳杉和野桐,其重要值之和高达0.292 3;在大林窗内,杉木及亮叶桦为群落优势物种,群落内出现大量其更新幼苗。(3)不同大小的林窗表现为灌木层物种丰富度指数(D)、Shannon-Wienner指数(H)、和Pielou均匀度指数(Jsw)值在400~450 m2面积的大林窗内达到一个均优水平,草本层物种的多样性在面积为100~150m2的小林窗内达到较高水平;不同梯度的林窗各层次群落D、H值整体表现为林缘林窗中心林下。研究认为:林窗的存在会改变群落物种组成,提高群落物种多样性水平,并且大林窗(400~450m2)更利于柳杉人工林林下树种更新及物种多样性的提高。  相似文献   

10.
Aims The community succession theory is much debated in ecology. We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions, among them: (i) During secondary succession, does the community composition converge towards one community state or multiple states depending on the initial colonization? (ii) Do mound communities located in different background communities exhibit different assembly trajectories?Methods In a sub-alpine meadow, we investigated a total of 80 mound communities at several successional stages in three different background communities resulting from different management histories and compared their changes in species composition. The distribution of plant communities over time was analyzed with quantitative classification and ordination methods. The co-occurrence patterns of species were evaluated at each successional stage, and the degree of convergence/divergence among communities was obtained by calculating two beta-diversity indices.Important findings During secondary succession, species richness of mound communities changed over time, and this change was dependent on the background community. Five life-form groups exhibited different dynamic patterns in species richness and plant cover. Community composition and the degree of species co-occurrence between communities increased over time since disturbance. There was much variation in species composition at earlier stages of succession, but communities on older mounds became more similar to each other and to their surrounding vegetation over the course of secondary succession. Post-disturbance succession of Zokor mound communities transitioned from 'multiple alternative states' to 'background-based deterministic community assembly' over time. Tradeoffs between competition and colonization, as well as the characteristics of different life-forms and mass effects within a limited species pool are the mechanisms responsible for convergence of mound communities.  相似文献   

11.
Ecologists have recently interpreted patterns of phylogenetic distance among coexisting species as indicative of processes affecting community assembly during forest succession. We investigated plant community phylogenetic structure along a successional gradient in New Guinean lowland rain forest. We surveyed all trees with diameter at breast height ≥ 5 cm in nineteen 0.25 ha plots representing younger secondary, older secondary, and primary forest. We estimated plant community phylogeny from rbcL gene sequences to quantify change in phylogenetic structure during succession. Mean phylogenetic distance among co‐occurring trees increased with total basal area per plot, a proxy for forest age. Significant phylogenetic clustering was detected in secondary forest whereas primary forest was significantly over‐dispersed relative to null expectations. We examined the sensitivity of these patterns to various methods of branch length estimation and phylogenetic uncertainty. Power to detect community phylogenetic patterns when equal branch lengths were assumed was weak in comparison to direct molecular and time‐calibrated measures of divergence. Inferred change during forest succession was also robust to phylogenetic uncertainty so long as temporal information was incorporated in estimates of divergence. The observed patterns are consistent with processes of environmental filtering during tropical forest succession giving way to other processes in primary forests including density‐dependence.  相似文献   

12.
Understanding the recovery dynamics of ecosystems presents a major challenge in the human-impacted tropics. We tested whether secondary forests follow equilibrium or non-equilibrium dynamics by evaluating community reassembly over time, across different successional stages, and among multiple life stages. Based on long-term and static data from six 1-ha plots in NE Costa Rica, we show that secondary forests are undergoing reassembly of canopy tree and palm species composition through the successful recruitment of seedlings, saplings, and young trees of mature forest species. Such patterns were observed over time within sites and across successional stages. Floristic reassembly in secondary forests showed a clear convergence with mature forest community composition, supporting an equilibrium model. This resilience stems from three key factors co-occurring locally: high abundance of generalist species in the regional flora, high levels of seed dispersal, and local presence of old-growth forest remnants.  相似文献   

13.
林窗作为森林群落中一种重要的干扰方式, 对林下物种构成有着重要的影响。开展林窗空间格局及其特征指数与林下植物多样性关系研究对于探讨林窗对林下生物多样性的影响有重要意义, 有助于进一步了解群落动态, 在物种多样性保护方面也具有指导作用。本研究在西双版纳热带雨林地区随机选取3块大小为1 ha的热带雨林为研究样地, 采用轻小型六旋翼无人机搭载Sony ILCE-A7r可见光传感器, 分别获取各个样地的高清数字影像, 结合数字表面高程模型以及各个样地的地形数据用以确定各样区的林窗分布格局, 并进一步提取出各林窗的景观格局指数。结合地面样方基础调查数据, 对各样地各林窗下植物多样性情况进行统计, 旨在分析热带雨林林窗空间分布格局以及林窗下植物多样性对各林窗空间格局特征的响应情况。研究表明, 西双版纳州热带雨林林窗呈大而分散的空间分布, 林窗空间格局特征指数如林窗形状复杂性指数、林窗面积都与林下植物多样性呈显著正相关关系。在面积小的林窗下, 较之林窗形状复杂性因子, 林窗面积大小对林下植物多样性影响更显著; 在面积达到一定程度后, 相对于面积因子, 林窗形状复杂性指数对林下植物多样性影响更显著, 各样地林窗皆趋于向各自所处样地顶极群落发展。  相似文献   

14.
In regenerating coastal dune forest, the canopy consists almost exclusively of a single species, Acacia karroo. When these trees die, they create large canopy gaps. If this promotes the persistence of pioneer species to the detriment of other forest species, then the end goal of a restored coastal dune forest may be unobtainable. We wished to ascertain whether tree species composition and richness differed significantly between canopy gaps and intact canopy, and across a gradient of gap sizes. In three known‐age regenerating coastal dune forest sites, we measured 146 gaps, the species responsible for gap creation, the species most likely to reach the canopy and the composition of adults, seedlings and saplings. We paired each gap with an adjacent plot of the same area that was entirely under intact canopy and sampled in the same way. Most species (15 of 23) had higher abundance in canopy gaps. The probability of self‐replacement was low for A. karroo even in the largest gaps. Despite this predominance of shade‐intolerant species, regenerating dune forest appears to be in the first phase of succession with ‘forest pioneers’ replacing the dominant canopy species. The nature of these species should lead to successful regeneration of dune forest.  相似文献   

15.
Question: Is tree regeneration in canopy gaps characterized by chance or predictable establishment. Location: Coastal scarp forests, Umzimvubu district, Eastern Cape Province, South Africa. Methods: Estimation of richness of gap‐filling species across canopy gaps of different size. Data are compared with regeneration under the canopy. Probability of self‐replacement of gap forming species is calculated. Results: Forest area under natural gap phase was 7.8%, caused mostly by windthrow (54%). The abundance and average size of gaps (87.8 m2) suggests that species diversity may be maintained by gap dynamics. However, only four of 53 gap‐filler species displayed gap size specialization and these were pioneer species. An additional 13 species were more common in larger gaps but there was no gradient in composition of gap‐filler species across gap size (p= 0.61). Probabilities of self‐replacement in a gap were low (< 0.3) and common canopy species were equally abundant in gaps and the understorey. Species composition in gaps showed no pattern of variation, i.e. was unpredictable, which suggests absence of a successional sequence within tree‐fall gaps. There was also only a slight increase in species richness in gaps at intermediate levels of disturbance. Conclusions: Coastal scarp forest appears not to comprise tightly co‐evolved, niche‐differentiated tree species. Unpredictable species composition in gaps may be a chance effect of recruitment limitation of species from the species pool. Chance establishment slows competitive exclusion and may maintain tree diversity in these forests. These data suggest that current levels (≤ 3 gaps per ha) of selective tree harvesting may not cause a reduction in species richness in this forest.  相似文献   

16.
Plant–soil interactions are increasingly recognized to play a major role in terrestrial ecosystems functioning. However, few studies to date have focused on slow dynamic ecosystems such as forests. As they are vertically stratified by multiple vegetation strata, canopy tree removal by thinning operations could alter forest plant community through tree canopy opening. Very little is known about cascading effects on soil biodiversity. We conducted a large‐scale, multi‐site assessment of collembolan assemblage response to long‐term canopy tree removal in sessile oak Quercus petraea temperate forests. A total of 33 experimental plots were studied covering a large gradient of canopy tree basal area, stand age and local abiotic contexts. Collembolan abundance strongly declined with canopy tree removal in early forest successional stage and this was mediated by negative effect of understory plant community composition changes, i.e. shift from moss and forb to tree seedling, fern, shrub and grass species. Negative effect of this composition shift on collembolan species richness was largely offset by positive effect of the increase in understory plant species richness. This gives support to both the plant mass‐ratio and functional diversity hypotheses. Collembolan functional groups had contrasting response patterns, which were mediated by different ecological factors. Epedaphic (r‐strategist) abundance and species richness increased with canopy tree removal in relation with the increase in understory plant species richness. In contrast, euedaphic (K‐strategist) abundance and species richness declined with canopy tree removal in early forest successional stage in relation with changes in understory plant community composition and species richness, as well as microclimatic conditions. Overall, our study provides experimental evidence that forest plant community can be a strong driver of collembolan assemblages. It also emphasizes the role of trees as foundation species of forest ecosystems that can shape soil biodiversity through their regulation of understory plant community and ecosystem abiotic conditions.  相似文献   

17.
Drone-based remote sensing is a promising new technology that combines the benefits of ground-based and satellite-derived forest monitoring by collecting fine-scale data over relatively large areas in a cost-effective manner. Here, we explore the potential of the GatorEye drone-lidar system to monitor tropical forest succession by canopy structural attributes including canopy height, spatial heterogeneity, gap fraction, leaf area density (LAD) vertical distribution, canopy Shannon index (an index of LAD), leaf area index (LAI), and understory LAI. We focus on these variables’ relationship to aboveground biomass (AGB) stocks and species diversity. In the Caribbean lowlands of northeastern Costa Rica, we analyze nine tropical forests stands (seven second-growth and two old-growth). Stands were relatively homogenous in terms of canopy height and spatial heterogeneity, but not in their gap fraction. Neither species density nor tree community Shannon diversity index was significantly correlated with the canopy Shannon index. Canopy height, LAI, and AGB did not show a clear pattern as a function of forest age. However, gap fraction and spatial heterogeneity increased with forest age, whereas understory LAI decreased with forest age. Canopy height was strongly correlated with AGB. The heterogeneous mosaic created by successional forest patches across human-managed tropical landscapes can now be better characterized. Drone-lidar systems offer the opportunity to improve assessment of forest recovery and develop general mechanistic carbon sequestration models that can be rapidly deployed to specific sites, an essential step for monitoring progress within the UN Decade on Ecosystem Restoration.  相似文献   

18.
林窗几何特征的测定方法   总被引:1,自引:0,他引:1  
林窗面积、形状及边界木高是决定林窗环境异质性的3个林窗几何特征,影响林窗内植物更新。林窗几何特征的快速测量方法是林窗研究的基础,测量方法可分为2类:基于地面实际测量的地面法和基于林窗林冠照片的相片法。地面法费时费力,受人为因素影响大,可测量林冠林窗和扩展林窗的面积,但不能测量林窗形状和边界木高。相片法具有简单、客观、可重复的优点,但仅适用于林冠林窗。相片法共有5种:"平面相片法"、"航片法"、"半球面影像法"、"双半球面影像法"和"改进的半球面影像法"。前3种测量方法只能测量林冠林窗面积;"改进的半球面影像法"可测量林冠林窗面积和形状,且精度高于前3种相片法,但所需参数最多;"双半球面影像法"可测量林窗面积、形状及边界木高这3个林窗几何特征,且精度较高,但拍摄要求较高。  相似文献   

19.
Predicting plant community responses to changing environmental conditions is a key element of forecasting and mitigating the effects of global change. Disturbance can play an important role in these dynamics, by initiating cycles of secondary succession and generating opportunities for communities of long‐lived organisms to reorganize in alternative configurations. This study used landscape‐scale variations in environmental conditions, stand structure, and disturbance from an extreme fire year in Alaska to examine how these factors affected successional trajectories in boreal forests dominated by black spruce. Because fire intervals in interior Alaska are typically too short to allow relay succession, the initial cohorts of seedlings that recruit after fire largely determine future canopy composition. Consequently, in a dynamically stable landscape, postfire tree seedling composition should resemble that of the prefire forest stands, with little net change in tree composition after fire. Seedling recruitment data from 90 burned stands indicated that postfire establishment of black spruce was strongly linked to environmental conditions and was highest at sites that were moist and had high densities of prefire spruce. Although deciduous broadleaf trees were absent from most prefire stands, deciduous trees recruited from seed at many sites and were most abundant at sites where the fires burned severely, consuming much of the surface organic layer. Comparison of pre‐ and postfire tree composition in the burned stands indicated that the expected trajectory of black spruce self‐replacement was typical only at moist sites that burned with low fire severity. At severely burned sites, deciduous trees dominated the postfire tree seedling community, suggesting these sites will follow alternative, deciduous‐dominated trajectories of succession. Increases in the severity of boreal fires with climate warming may catalyze shifts to an increasingly deciduous‐dominated landscape, substantially altering landscape dynamics and ecosystem services in this part of the boreal forest.  相似文献   

20.
通过对贵州省普定县喀斯特地区不同植被演替阶段群落的调查, 研究了植被演替过程中群落物种组成和群落结构的变化。结果表明, 该地区的植被主要处于5个演替阶段, 即次生乔木林、乔灌过渡林、藤刺灌丛、稀灌草丛以及火烧干扰后的蕨类植物群落。本次调查共记录到植物365种, 隶属89科218属。其中, 蕨类植物31种, 隶属14科23属; 种子植物334种, 隶属75科195属。物种分布较多的科主要有蔷薇科、菊科、禾本科、百合科、忍冬科、唇形科、莎草科、樟科、葡萄科和水龙骨科。随着正向演替的推进, 物种丰富度增加, 群落结构趋于复杂化。藤刺灌丛与乔灌过渡林群落层次不明显, 次生乔木林分层明显。从藤刺灌丛向次生乔木林演替的过程中, 小径级个体所占比例明显降低, 高于1.3 m植物的总密度、乔木密度和藤本密度都先升高后降低, 而灌木密度呈逐渐降低的趋势。对喀斯特地区植被的恢复提出了参考措施。  相似文献   

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