Secondary forest floristic composition, structure, and spatial pattern in subtropical China

Secondary evergreen broadleaved forests are precious remnants for biodiversity conservation and templates for sustainable management of natural forests in subtropical China. Floristic composition, size structure, and spatial pattern of dominant tree species have been investigated for a subtropical secondary evergreen broadleaved forest in the Huitong Yingzuijie National Forest Reserve, Hunan, China. The location of all trees greater than 4 cm in diameter at breast height (DBH) were mapped within a 0.96-ha plot in which species, DBH, and total tree height were recorded. Ripley’s K(t) function was used to analyze spatial patterns and associations. The secondary forest consisted of 74 tree species and 1,596 stems per hectare. A reverse-J shaped DBH classes distribution was observed for all stems and trees of later seral species whereas trees of earlier successional species were distributed irregularly. Significant aggregated spatial patterns were observed for all trees within the forest and for conspecific trees of each dominant species. This result, and a repulsive spatial pattern for interspecific trees of Choerospondias axillaries and Cyclobalanopsis glauca against other dominant tree species, support segregation hypothesis. Contributions of seed dispersal, topographic heterogeneity, and competition to spatial patterns of conspecific trees vary depending on tree species. Attractive spatial pattern among interspecific trees of Liquidambar fortunei, Liquidambar formosana, and Pinus massoniana reflects stochastic colonization of pioneer tree species and a facilitation relationship. Although deciduous species are long-lived and persist over long successional processes, they will eventually be replaced by late seral evergreen species within the secondary forest if no disturbance events occur.     

Spatial distributions of tropical tree species in northern Vietnam under environmentally variable site conditions

Ecological interactions of species and thus their spatial pat- terns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that： environmental conditions were homo- geneous at plot 1 but heterogeneous at plot 2; in both plots, all six domi- nant species were aggregated at various scales up to 30 m, and tree spe- cies were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia （homogeneous plot） and D. sylvatica, S. wightianum （heterogeneous plot） showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-ConneU hypothesis. Overall, habitat het- erogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species.     

Spatial associations among tree species in a temperate forest community in North-western Spain

Analyzing spatial patterns in plant communities may provide insights in the importance of different processes for community assembly and dynamics. We applied techniques of spatial point pattern analysis to data from a fully mapped plot of a temperate forest community (Corylus avellana, Crataegus monogyna, Fagus sylvatica, Ilex aquifolium and Taxus baccata) in North-western Spain to conduct a community wide assessment of the type and frequency of intra and interspecific spatial association patterns. We first explored the overall intra and interspecific patterning, and then classified the types of association patterns at various neighbourhoods. By conditioning on the larger scale pattern we then explored small-scale (0–15 m) intraspecific and interspecific patterns. Association patterns varied from strong positive association at small scales to, as a by-product, repulsion at intermediate scales. Surprisingly, there were no negative associations at small scales, but trees were arranged in multi-species clumps, up to 2.5 m in diameter and comprising a few individuals. Ilex and Corylus, the understorey species, were frequently involved in the clumps, showing positive small-scale association with the other tree species. Our analyses highlighted that animal mediated seed dispersal, interspecific facilitation and perturbation processes may operate successively to shape tree distributional patterns, although their relative importance vary among species. Given the complexity of the patterns described and the current threats to some of the species studied, directed experiments in the field are needed to further elucidate some of the hypotheses derived.     

云冷杉红松林内优势种群的空间格局及种间关联性

【目的】以云冷杉红松林(Spruce-fir-Korean pine forest)为研究对象,探究林隙干扰后优势种群之间的关系。【方法】基于凉水国家级自然保护区外业调查的基本数据,利用点格局分析方法对优势种群的空间格局进行分析,利用χ2检验和联结系数AC两种方法对优势种群的种间关联性进行分析。【结果】1)红松Pinus koraiensis在空间尺度为0~1.9 m时呈现随机分布,在≥1.9 m时为聚集分布。臭冷杉Abies nephrolepis、白桦Betula platyphylla和红皮云杉Picea koraiensis在所有尺度上均表现为聚集分布,紫椴Tilia amurensis在尺度为0~35 m时呈现聚集分布,在>35 m时为随机分布。2)红松与臭冷杉在所有尺度上均为聚集分布,红松与其他优势种群多为离散分布,红松与其他优势种群的种间关联性表现为无关。臭冷杉与白桦、紫椴在空间格局上主要为聚集分布,种间关联性为极显著负相关,表现为强烈的竞争关系。臭冷杉与红皮云杉在小尺度表现为离散分布,大尺度上为随机分布,种间关联性为不显著的正相关,说明其间的依赖性不强。白桦、红皮云杉和紫椴3种优势种群之间的空间格局主要为聚集分布,红皮云杉与白桦、紫椴与红皮云杉之间的种间关联性为显著负相关,白桦与紫椴之间为显著正相关。【结论】2个树种中优势度较高的树种的胸径决定了其空间格局的聚集程度以及种间关联性的显著程度,即平均胸径大的树种与其他树种表现为空间上离散,平均胸径小的树种之间表现为空间上聚集。     

基于分层的典型中亚热带天然阔叶林林木竞争关系研究

[目的]通过分析不同林层林木之间的竞争情况,以期揭示林木间相互竞争的类型、林木受到的竞争压力与林木垂直分布之间的关系,为森林资源的保护与利用提供科学依据。[方法]在福建万木林自然保护区内设5块典型中亚热带天然阔叶林样地,采用Hegyi的竞争指数,按分层和不分层两种情形研究林木间的竞争强度。[结果]在1—5号样地,当取样半径超过4 m后,林木间的竞争强度随取样半径的增大而减小的趋势变缓,4 m是分析林木竞争的适宜半径;以4 m为半径分析林木间的竞争,发现有一半以上的组成树种只发生种间竞争,剩余同时发生种间和种内竞争的树种,其竞争木构成中数量占优势的普遍是与其相异的树种,且种间竞争强度普遍强于种内竞争;各样地的乔木层都可以划分出由高到低的3个林层,在平均水平,越高层的林木距离竞争木越远、在竞争木的组成中较矮小的第3林层林木数量也越多;越高层的林木,平均每株对象木与其全部竞争木之间的竞争压力越小。[结论]在调查的典型群落中,普遍发生的是种间竞争,而林木受到的竞争压力及其竞争木的组成都与它们的垂直分布关系密切,在森林资源保护和经营中应对垂直分布予以更多的关注;乔木层中的优势树种未发生激烈种间或种内竞争;可以发生激烈种间竞争的乔木树种有米槠、庆元冬青、少叶黄杞和杜英,不存在特定的竞争木与它们竞争,它们与竞争木相近、主要分布在第2或第3林层;种内竞争过于激烈的有山杜英、华杜英、山黄皮、野含笑和羊舌树,也主要分布在第2或第3林层。     

哀牢山湿性常绿阔叶林木质藤本植物的物种多样性及其与支柱木的关系

分别在哀牢山湿性常绿阔叶林沟谷和坡面调查了10个20m×50m的样地,研究哀牢山湿性常绿阔叶林木质藤本植物的物种多样性及其与支柱木的关系。结果表明:研究区共记录到DBH≥1cm的木质藤本植物402株(隶属于23种21属16科)和DBH≥10cm的林木1522株(隶属于47种30属15科);与其他亚热带森林比较,该森林中木质藤本植物物种较为丰富但多度较低;藤本植物的物种丰富度、密度和基面积在沟谷显著高于坡面,而林木的差异性不显著;木质藤本植物在支柱木上呈集群分布,并且不同种支柱木被藤本植物攀援的百分比间存在显著的差异(P0.001),说明藤本植物的攀援对支柱木具有选择性;云南越桔、薄叶马银花和景东冬青等树种因其树皮光滑而不易被藤本植物攀援,而腾冲栲、七裂槭、山矾和多花山矾等则易于被藤本植物攀援;大径级支柱木被藤本植物攀援的比率高于小径级支柱木;茎缠绕和钩刺攀援藤本的胸径与支柱木胸径极显著相关(P0.001),根攀援和卷须攀援藤本的胸径与支柱木胸径相关性不显著(P0.05)。     

Species spatial distributions in a warm-temperate deciduous broad-leaved forest in China

Spatial distribution is fundamental for understanding species coexistence mechanisms in forest communities.Here we comprehensively explored fine-scale spatial patterns of tree species in a secondary warm-temperate deciduous broad-leaved forest community in north China.Aggregated distribution patterns were predominant.Species functional traits had no significant effects on their spatial patterns.The aggregation intensity decreased with increasing DBH and abundance.The multivariate linear stepwise regression showed that abundance and maximum DBH were correlated with the aggregation intensity.Our results partially confirm that species attributes(abundance,DBH) and habitat heterogeneity may primarily contribute to spatial patterns and species coexistence in this secondary forest.     

冀北土石山区天然次生林山杨、白桦种群的空间分布格局

分析冀北土石山区典型天然次生阔叶林中的山杨、白桦种群的径级结构、空间分布格局及种内/种间的空间关联。结果表明:山杨、白桦均以中径木为主,林下缺乏可供更新的幼苗、幼树,种群呈现衰退趋势;山杨、白桦的全部个体在本研究尺度上呈聚集分布,随尺度的增大其聚集强度先增大后减小,并趋于随机分布;山杨、白桦种群随龄级增大,聚集强度减小,以幼树的聚集强度最大;不同生长阶段同种个体间的关联性随尺度的变化,出现正关联、负关联和相互独立的空间关系,以负关联为主;不同生长阶段的山杨和白桦种群间未出现正关联,大多数种对在本研究尺度上为负关联或者在大部分尺度上为负关联;山杨、白桦的种内/种间竞争激烈,群落整体结构不稳定,处于演替初期向中期过渡阶段。     

三尖杉所属群落优势乔木树种种间关系

采用样方调查法,对组成大岗山三尖杉所属群落的乔木树种进行调查.通过计算重要值确定三尖杉所属群落优势乔木树种,在此基础上,研究优势树种的总体联结性、两树种间的联结性和种间协变.结果表明:三尖杉所属群落内的15个优势乔木树种总体间存在显著正关联;两树种间具有显著正联结的种对是细枝柃-梾木、红楠-杉木,呈显著负联结的种对是石栎-杉木;三尖杉与其他优势乔木树种的联结性均未达到显著程度,细枝柃-鹿角杜鹃、细枝柃-梾木、细枝柃-三尖杉、梾木-紫楠、红楠-杉木、红楠-拟赤杨等6个种对表现出明显的正协变,鹿角杜鹃-柃木种对表现出明显的负协变;种对正协变的存在是由于这些物种对环境资源的利用具有相似性所致.     

Tree species exhibit complex patterns of distribution in bottomland hardwood forests

?Context

Understanding tree interactions requires an insight into their spatial distribution.

?Aims

We looked for presence and extent of tree intraspecific spatial point pattern (random, aggregated, or overdispersed) and interspecific spatial point pattern (independent, aggregated, or segregated).

?Methods

We established twelve 0.64-ha plots in natural bottomland hardwood stands in the southeastern USA.

?Results

Spatial point pattern analyses (Ripley’s K, L, and L ₁₂) indicated that, when species were combined, trees were frequently aggregated and less commonly overdispersed. Plots with larger trees were more likely to exhibit overdispersion, confirming a shift to this pattern as trees grow. The intraspecific pattern of cherrybark oak and water oak was either aggregated or random. Sweetgum was aggregated on all plots and always at smaller distances (less than 5 m) than the two oak species. Intraspecific overdispersion was very rare. Interspecific segregation among the two oak species was more commonly observed (six plots) than aggregation (one plot). Cherrybark oak and sweetgum were segregated at some scale on seven of the 12 plots and aggregated on only two plots.

?Conclusion

The results from the analyses suggest that strong interspecific competition may result in segregation of trees from different species, while weaker intraspecific competition may lead to aggregations of conspecifics.     

Evaluation of leaf display of evergreen broadleaved tree species and deciduous tree species in warm temperate conifer plantations

We investigated the sapling leaf display in the shade among trees of various leaf lifespans co-occurring under the canopy of a warm-temperate conifer plantation. We measured leaf-area ratio (aLAR) and morphological traits of saplings of evergreen broadleaved tree species and a deciduous tree species. Although we found large interspecific and intraspecific differences in aLAR even among saplings of similar size in the homogeneous light environment, we did not find a consistent trend in aLAR with leaf lifespan among the species. While deciduous trees annually produced a large leaf area, some evergreen broadleaved trees retained their leaves across years and had aLAR values as high as those of deciduous trees. Among leaf-level, shoot-level, and individual-level morphological traits, aLAR was positively correlated with current-year shoots mass per aboveground biomass in deciduous trees, and with the area of old leaves per aboveground mass in evergreen broadleaved trees. Thus, tree-to-tree variation in the degrees of annual shoot production and the accumulation of old leaves were responsible for the interspecific and intraspecific variations in aLAR.     

Spatial pattern dynamics among co-dominant populations in early secondary forests in Southwest China

The canopy of subtropical natural forests usually consists of several co-dominant populations(CDPs),which play a crucial role in forest structure,formation of the forest environment,and ecological function.However,little attention has been given to changes in spatial patterns in CDPs during natural succession.Cyclobalanopsis glauca(Thunb.)Oerst.,Quercus variabilis Blume,and Pinus yunnanensis var.tenuifolia W.C.Cheng Y.W.Law are canopy species that form CDPs in zonal forests along the Nanpan River in southwest China.We used the g(r) function and its bivariate distribution model,g_(12)(r),which is based on distances between pairs of points,to explore the dynamics of the three CDP species with respect to distribution patterns and spatial correlations in two secondary forests(one 30-year-old forest [30-YF] and one 57-year-old forest [57-YF]).The following key results were obtained:(1) there was a clumped pattern in the 30-YF,but the intensity of aggregation varied among populations and life stages.The distribution pattern gradually shifted to become random with longer succes sion time(i.e.,30-YF vs.57-YF),expansion of the observation scale(r=0-20 m),and at later life stages.(2) Aside from the mid-sized C.glauca trees and large P.yunnanensis trees,the trees repulsed each other at certain scales(r=0-2,5-6,11-12,14-16 m) in the 30-YF.Almost all of the life stages in the CDPs were independently correlated.This independent correlation was exacerbated by a longer succession time.(3) An increase in life stages and longer succession also promoted independent changes in intraspecific correlations.(4) Intraspecific correlations were stronger than interspecific correlations.Our results showed that reducing exclusive competition is essential to coexistence in CDPs.Inter-and intra-specific repulsion may occur at the same time,but intraspecific repulsion was the main driving force behind the random distributions and independent correlations.     

中国东北蛟河阔叶红松林主要树种种群结构与更新模式的研究(英文)

在对东北蛟河林场３２ｈ ｍ ２ 阔叶红松林每木调查的基础上,研究了阔叶红松林主要树木种群的径级结构,分析了阔叶红松林主要树种的更新模式及其机理．结果表明,阔叶红松林中不同树种的最大径级及其在不同径级中的株数分布不同,阔叶树种的最大径级大都低于针叶树种．根据不同树种按径级的株数分布特征,可将阔叶红松林中的主要树种分为四类．根据不同树种各径级的累计株数百分率曲线所拟合的方程,亦可将阔叶红松林中的主要树种划分为四种类型．以林木种群的径级结构为基础,文章阐述了树木径级结构的平衡性,分析了阔叶红松林主要树种的更新模式及其与自然干扰状况和不同时空尺度的关系,探讨了样地大小对阔叶红松林种群结构研究结果的影响．     

罕山国家级自然保护区大样地优势树种点格局分析

以罕山国家级自然保护区内森林动态监测大样地为研究对象,采用数量生态学的点格局分析法(Ripley’s K函数),对其优势种的组成及结构、空间分布格局进行分析。结果显示:样地内重要值排在前4位的乔木树种是黑桦(Betula dahurica)、山杨(Populus davidiana)、白桦(Betula platyphylla)和山荆子(Malus baccata),其相对多度之和为98.1%,相对显著度之和为99.68%,是构成样地内植物群落的骨架型乔木植物。样地内林木总径级结构呈近似的指数分布,幼龄期的个体数量最多,植物群落更新良好,属于增长型群落。白桦、黑桦和山杨在不同尺度下的空间分布格局基本都呈集群分布的形式,随尺度的增大,其聚集强度表现为先增大后减小的趋势。山荆子种群的空间分布格局随尺度增大呈现出聚集分布向随机分布转变的趋势。     

The Impact of Hardwood Line-Planting on Tree and Amphibian Diversity in a Secondary Subtropical Wet Forest of Southeast Puerto Rico

The impact on tree and amphibian diversity of line-planting of tropical hardwoods—mahogany (Swietenia macrophylla × S. mahagoni) and mahoe (Hibiscus elatus)—was studied in a secondary subtropical wet forest of Puerto Rico. Common coqui (Eleutherodactylus coqui) and melodious coqui (E. wightmanae) are the most frequent frog species; forest coqui (E. portoricensis) is less abundant. Although relative abundance means were slightly greater in the undisturbed forest and during the wet season, differences were not statistically significant suggesting that line-planting did not significantly affect amphibian diversity. The line-planted areas had a slightly higher, but not statistically significant diversity, richness, and evenness of tree species than the unplanted forest. Multi-response permutation procedure (MRPP) showed statistically significant community composition differences between line-planting and control plot trees (T = ?5.89, A = .86; p < .001). But mean similarity among plots in both the line-planted and control plots was relatively low at less than 50% of shared species, indicating high diversity of vegetation in the overall forest area. Canopy cover by tree species greater than 3 cm in dbh was much higher in the undisturbed forest but this difference may be reduced as the young line-planted hardwoods mature. Forest enrichment through line-planting of valuable timber species in secondary subtropical wet forest does not significantly affect tree diversity.     

Species-specific spatial structure,species coexistence and mortality pattern in natural,uneven-aged Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.)-dominated forest

Complexity of uneven-aged forests results from the heterogeneity of their structure reflected among others by the spatial pattern of their components. Forest structure is usually modified by various processes operating at different scales and time. Structure and processes are not independent, and both are important drivers of forest dynamics. The impact of natural processes on forest structure manifested in the specific spatial pattern of trees can be quantified by point pattern analysis applied to long-term repeatedly measured stem-mapped plots. Such studies are relatively scarce in the literature although they provide better insight into the mechanisms affecting forest dynamics. Our study is focused on the spatiotemporal analysis of the structure of mixed uneven-aged Scots pine-dominated forest located at the Kampinoski National Park (Poland). Univariate analysis showed that the initial pattern of all live trees was initially random and it shifted toward more uniform with forest aging. Spatial patterns of individual tree species varied from that stated for all forest community. We observed changes in spatial pattern of Scots pine and common oak from random toward more clumped (pine) or uniform (oak) pattern. In case of black alder and common birch, the initial aggregated pattern was maintained over the examined 14-year period of the forest succession. Bivariate analysis showed that the most common interspecific association between pairs of tree species was spatial segregation (pine vs. alder, alder vs. birch and oak vs. birch) followed by spatial independence (pine vs. oak and oak vs. alder). The positive association was stated only for pine and birch and only for certain spatial scales (> 5 m). Simultaneously, at small distances they showed reciprocal repulsion. Changes in spatial relationships between tree species were negligible over 14-year period of forest succession. Our results confirmed the density-dependent mortality process in the uneven-aged Scots pine-dominated forest over 14-year period of forest development. Our study showed that spatial interactions between individuals along with species-specific ecological requirements should be incorporated into realistic models of forest development, helping to manage the forest ecosystems toward their greater structural complexity.     

浑善达克沙地2种生境下榆树种群空间点格局

以浑善达克沙地固定沙丘与丘间低地2种生境下榆树种群为研究对象,采用点格局分析法对不同生长阶段榆树种群的空间分布格局及其空间关联性进行分析。结果表明:丘间低地种群整体在<10m的小尺度上呈现聚集分布,幼树和中龄树在大尺度上呈随机分布,而成熟树呈现聚集分布;各发育阶段间的空间关联主要表现在小尺度上,随着空间尺度的增加,空间关联性微弱;固定沙丘榆树种群均在小尺度上呈聚集分布,随尺度增大种群呈现随机分布趋势;中龄树和成熟树间在小尺度上呈正关联,各个发育阶段间在大尺度上空间关联性很小。     

Density dependence on tree survival in an old-growth temperate forest in northeastern China

? Density dependence is a major mechanism for shaping plant communities. However, its role in regulating diverse, mixed natural tree communities is less certain.

? In this study we investigated density-dependent effects in a large-scale (25 ha) old-growth temperate forest in northeastern China. Spatial patterns of neighborhood distribution in the plot were analyzed using various methods for inferring competition, including (1) pair correlation function to determine spatial patterns of pre-mortality and post-mortality and (2) neighborhood analysis of individuals to examine the extent to which tree survival is correlated with other covariates.

? Results showed that, for common species, 3 of 5 canopy species and 3 of 8 midstory and understory species were random in mortality. Negative density-dependent mortality was not found when trees reach 1 cm in DBH. There was no significant correlation for canopy species between tree survival and conspecific abundance, but largely positive correlations for midstory and understory species. In contrast, tree survival was found to negatively correlate with conspecific basal area for most species, indicating strong intraspecific competition. No strong interspecific density dependence was found in the forest.

     

亚热带多优势种森林群落演替现状评判研究

亚热带多优势种常绿阔叶林演替过程,依第１优势种的耐荫,喜湿特性,可划分为６个阶段;（１）针叶林阶段;（２）以针叶树为主的针阔混交林阶段;（３）以阳生性阔叶树为主的针阔混交林阶段;（４）以阳生性树种为主的绿阔叶林,当中生性树种在成为第１优势树种表明演替已进入顶极阶段,此后,又以优势树种人布格局为依据,将顶极阶段分为第５、第６阶段;（５）未发衣完善的顶极阶段;（６）发育完善的顶极阶段。据此,判定本文所     

Spatial structure of deciduous forest stands with contrasting human influence in northwest Spain

Five contrasting deciduous forest stands were studied to characterize the spatial structural variability in human-influenced forests. These stands are representative of cultural forest types widely represented in western Europe: one plantation, two coppices, one wood-pasture forest and one high forest stand. All stems with DBH > 5 cm were measured and mapped, and stem DBH distributions, spatial structure of DBH, spatial point patterns and spatial associations were analysed. Spatial autocorrelation for DBH was calculated with Moran’s I correlograms and semivariograms. Complete spatial randomness hypothesis for spatial point patterns, and both independence and random labelling hypotheses for spatial associations were analysed using Ripley’s K function. The results showed that tree sizes were conditioned by particular former management systems, which determined unimodal symmetric, positively skewed or compound DBH distributions. Spatial structure was more complex when human influence became reduced. Coppice stands showed clumped spatial patterns and independence among size classes, as a consequence of sexual and vegetative establishment of new stems in open areas. The largest clumping intensity was observed in the wood-pasture with an intermediate disturbance frequency and low inter-tree competition. The high forest stand displayed spatial traits consistent with the gap-dynamics paradigm, such as clumping of smaller trees, random arrangement of larger trees, negative association between juveniles and adults, and high structural heterogeneity. It can be expected that after cessation of human interference, coppices and wood-pastures would evolve to a more heterogeneous structure, probably with a higher habitat and species diversity.