Integrating alpha,beta, and phylogenetic diversity to understand anuran fauna along environmental gradients of tropical forests in western Ecuador

The study of current distribution patterns of amphibian species in South America is of particular interest in areas such as evolutionary ecology and conservation biology. These patterns could be playing an important role in biological interactions, population size, and connectivity, and potential extinction risk in amphibians. Here, we tested the effects of spatial and environmental factors on the variation, turnover, and phylogenetic diversity of anuran amphibian species in tropical forests of western Ecuador. Data for presence/absence of 101 species of 34 genera and 10 families registered in 12 sites (nested in four biogeographic units) were obtained through fieldwork, museum collections, and literature records. We examined the influence of geographical, altitudinal, temperature, and precipitation distances on differences in anuran composition between sites. We found significant positive correlations among all of these variables with anuran distribution. The greatest alpha diversity (species richness) was found in the Equatorial Chocó biogeographic unit. Equatorial Pacific biogeographic unit could act as a transition zone between the Equatorial Chocó and Equatorial Tumbes. The western Andes (Western Cordillera biogeographic unit) was the most dissimilar and exhibited a higher species turnover rate than the other biogeographic units. Our results suggest that precipitation and elevation play a key role in maintaining the diversity of amphibian species in western Ecuador.     

Taxonomic and structural similarities in soil oribatid communities

We examined the taxonomic and structural concordance between oribatid mite communities at different sites from around the world using meta-analysis. The study explored similarities in the taxonomie composition and species abundance distributions among oribatid mite communities using 25 published species lists from Africa, Australia, Europe. Japan. Malaysia, New Zealand and the United States, The final data set contained 253 genera from 97 families in 43 superfamilies, A second data set, which included only studies where trees were present at the sites, contained 234 genera, 93 families and 41 superfamilies. Composition was analysed at taxonomic levels higher than species. Only two families and four superfamilies were present in > 90% of all studies. Two genera, six families and seven superfamilies were found in all sites with trees. Common families were different among habitats suggesting that habitat preferences may be expressed at the family level. There were very strong relationships between oribatid mite species richness and richness at higher taxonomic levels with r² values for regression relationships > 0.8. Few species at a site were from the same genus, family or superfamily. Species abundance distributions were remarkably consistent between studies with the three most dominant species each constituting > 10% of the oribatid individuals. Overall, similar factors may determine the relative proportions of soil-dwelling oribatid species at a site.     

Macroecology of Aquatic Insects: A Quantitative Analysis of Taxonomic Richness and Composition in the Andes Mountains of Northern Ecuador

To determine the spatial dynamics of Neotropical lotic insect species, specimens were collected from 41 streams on the eastern and western flanks of the Andes Mountains in Ecuador. We examined the manner in which taxonomic richness and composition differed with elevation, latitude, and versant. Statistical analyses were limited to 5 families (Ephemeroptera: Baetidae, Leptohyphidae, Oligoneuriidae; Heteroptera: Naucoridae; Coleoptera: Elmidae), comprising 32 genera and 85 species, for which identifications or morphospecies assignments were reliable. Assessment of taxonomic diversity was based on the richness of genera and species at each site. In addition, each site was characterized by species richness within each of 4 families with more than 10 species. The effects of versant and transect on composition and structure were family‐specific. Mean site differences between versants in elmid richness at generic and specific levels depended on transect. Only baetid richness was affected by versant and transect in a consistent manner. Variation among sites in composition based on all genera and species was captured using multidimensional scaling (MDS). Subsequent MANOVAs based on scores from MDS axes revealed that differences between versants were much stronger in the southern transect, although transects differed from each other at specific and generic levels. A Jaccard's similarity matrix was computed for each family to reflect the spatial organization of taxonomic composition. Mesogeographic patterns of species composition for each of the four families were correlated (Mantel analysis) at both the regional level and at the level of the entire study area. At the regional level, the only pair of families to exhibit correlated patterns of species composition was elmids and naucorids in the southwestern region. The pattern of species composition for each family was correlated with the patterns for one or more other families at the level of the entire study area. Thus, spatial dynamics of species composition was similar for the families examined, suggesting that the Andes exert a consistent influence on species distributions within families, regardless of ordinal affiliation. At a local scale, however, the way in which taxonomic composition changed with latitude and versant was family‐specific. Mayflies, the most vagile of the taxa studied, had the highest percentage of species overlap between versants. Of three genera of Naucoridae collected, species of Ambrysus, of probable Mexican origin, were found only on the eastern versant, corroborating other evidence that the genus is recent in South America. Moreover, dispersion by Ambrysus across the Andes Mountains may not have occurred, as it has for Cryphocricos and Limnocoris, which are of probable South American origin.     

Revisiting Patterns of Tree Species Composition and their Driving Forces in the Atlantic Forests of Southeastern Brazil

The elucidation of phytogeographic patterns and their drivers in biodiversity hotspots is essential to the study of ecology and the conservation of these areas. In 2000, an important study by Oliveira‐Filho and Fontes led to changes in the paradigms that define our understanding of the Atlantic Forest (Brazil). Here, our aim was to revisit this study using a more comprehensive set of environmental predictors, an updated and much larger tree species dataset and checklist, and more refined data analyses. We performed exploratory and confirmatory analyses, including the modeling of the spatial components with Moran's Eigenvector Maps, using data from 483 sites in southeastern Brazil, which encompass a total of 3546 species and 33 geo‐climatic variables. We observed strong floristic similarities between rain‐ and seasonal forests and a species distribution continuum across the main gradients. The environmental and spatial variables were significantly correlated with floristic patterns, and we demonstrated that the tree flora of the seasonal forests should no longer be considered a simple subset of the rain forest flora. The findings of the original paper were not only confirmed but we also unveiled additional, important phytogeographic patterns. We also reinforced the main conclusion of the paper that the Atlantic Forest concept must encompass all of the forest types east of the dry corridor in South America, a designation of utmost importance for the conservation of this biodiversity hotspot.     

Floristic Characteristics of the Karkamis Dam Reservoir Area and its Surroundings (Gaziantep-Sanliurfa: Turkey)

The natural flora of Karkamis Dam lake area and its surroundings was studied in 2000 and 2001 before the dam construction was completed. During the floristic surveys, 464 species of 279 genera belonging to 70 families were recorded. The number of endemic species is 14. The phytogeographic elements are represented in the study as follows; Irano-Turanian 104 (18.2%), Mediterranean 66 (11.5%), Euro-Siberian 7 (1.2%), Cosmopolitan 9 (1.5%), Sharo-Arabian 1 (0.1%). The phytogeographic region of 383 taxa (67.1%) is unknown, or multiregional. The spectrum of the basic life forms is as follows; Therophytes 50.0%, Hemicryptophytes 33.4%, Phanerophytes 5.2%, Geophytes 5.2%, Chamaephytes 4.3% and Hydrophytes 1.9%. According to the IUCN Red List Categories, 28 threatened plant species were identified in the study area.     

云南地区种子植物多样性分布格局和多样性分化特点研究

利用大尺度的植物分布信息结合地理信息系统和数理统计分析,探讨了云南种子植物多样性的地理分布格局和多样性分化特点。结果表明,从科到属和种,植物多样性和区系分化强度的数据集离散程度均呈递增趋势。相对属和种而言,科的多样性的空间分异和高值区域并不明显,这可能与科、属、种所代表的不同地质历史时期有关;南部地区属和种的多样性明显高于除滇西北以外的大部分地区。种的多样性分布中心主要集中在滇西北地区、云南南部地区、哀牢山、无量山地区和昆明地区,这可能与生境异质性和热量条件有关。相对科而言,属的区系分化强度的空间分异更为明显,并与物种多样性的分布格局比较接近,暗示着植物多样性与区系分化之间的密切联系。相对科而言,属的区系分化中心高值区域更为明显。总体上,云南地区植物多样性的分布格局及其分化可能与其生境、热量条件和地质历史有关。     

Woody flora as a predictor of vascular plant richness: An insight in Italy

A key problem in quantifying biodiversity is whether it is possible to infer the overall diversity using suitable data subsets. The aim of this article, based on the updated data on the native woody flora of Italy, is to evaluate the reliability of such data as a predictor of vascular plant richness at a medium scale represented by the 20 administrative regions. Woody taxa were divided in trees, shrubs and lianas. We used stepwise multiple regression and principal component analysis to analyse the correlation between environmental heterogeneity, vascular plant units (species and subspecies) richness and woody units’ richness. Woody flora of Italy consists of 61 families, 133 genera, 469 species and 509 units. Shrubs constitute 74% of the woody flora, trees and lianas of 23% and 3%, respectively. Both stepwise multiple regression analysis and two principal component analyses strongly suggest that woody units, and trees in particular, are correlated with total vascular plant richness, at all hierarchical taxonomical levels. The environmental heterogeneity has been demonstrated to be much more important than the area for the biodiversity of Italian regions. Woody flora, as a surrogate of total flora, is extremely useful for rapid assessments of overall vascular plant diversity that may be exploited for monitoring purposes.     

中国两栖、爬行动物更新名录

本文在2015年发表的爬行动物名录及同年《中国两栖类信息系统》发布的两栖动物名录的基础上, 通过整理新发表的分类学研究及先前名录遗漏的部分早期文献, 更新了截至2019年底中国现生本土两栖、爬行动物物种名录。2015-2019年间, 中国两栖动物新记录1科, 新描述2属, 恢复1属有效性, 新记录1属, 新描述或恢复有效种74种, 新增国家纪录18种; 另6属、8种的有效性未得到近年研究证据支持(在此视为次定同物异名而未做收录, 后同)。同期, 中国爬行动物新恢复5科, 新描述1亚科, 新描述1属, 恢复3属有效性, 新记录3属, 新描述、恢复或提升有效种43个, 新增国家纪录10种; 另有5属、4种的有效性未得到近年研究证据支持, 并移除1属、4种在我国的分布纪录。此外, 通过整理2015年前文献, 爬行动物增补3属, 提升3亚种至种级地位, 增补国家新纪录3种, 另有3属、2种的有效性未得到近年研究证据支持, 同时移除1种在我国的分布纪录。综上, 截至2019年底, 我国共记录现生本土两栖动物3目13科62属515种(蚓螈目1科1属1种, 有尾目3科14属82种, 无尾目9科47属431种), 爬行动物3目35科135属511种(鳄形目1科1属1种, 龟鳖目6科18属34种, 有鳞目蛇亚目18科73属265种、蜥蜴亚目10科43属211种)。此外, 本文还对先前名录中部分爬行动物的中文名提出了修改建议, 建议恢复部分物种的惯用中文名。2015-2019年, 新物种及新纪录已知物种数量占现两栖、爬行动物物种总数的17.1%和10.2%。近年来, 我国发表的两栖、爬行动物新物种和已知物种的新纪录数量持续增加, 分类体系也在研究中不断完善, 建议今后及时地进行阶段性总结, 同时对存在的问题提出讨论, 以推动中国两栖、爬行动物分类学研究工作的进一步开展。     

海州湾及邻近海域冬季鱼类群落结构及其与环境因子的关系

根据2011年冬季在海州湾及邻近海域进行的渔业资源底拖网和环境调查数据,应用物种多样性指数和多元分析等方法,对该海域鱼类种类组成、多样性和群落结构及其与环境因子的关系进行了研究.结果表明: 该海域冬季捕获鱼类共60种,隶属于10目34科51属,以暖温性和暖水性底层鱼类为主.站位间物种丰富度指数介于1.14～2.84,多样性指数介于1.08～2.64,均匀度指数介于0.41～0.83之间.经聚类分析和非度量多维标度(MDS)分析,该海域鱼类群落在空间上可分为站位组Ⅰ(35° N以北水域站位)、站位组Ⅱ(靠近湾顶的近岸水域站位)和站位组Ⅲ(35° N以南水域站位).鱼类群落种类组成在站位组间及两两间的比较均差异极显著(R=0.45～0.91).典范对应分析表明,底层水温、水深和表层盐度是影响海州湾及邻近海域冬季鱼类群落结构的主要环境因子.     

Evolution of the Mitochondrial Cytochrome Oxidase II Gene in Collembola

The sequence of the mitochondrial COII gene has been widely used to estimate phylogenetic relationships at different taxomonic levels across insects. We investigated the molecular evolution of the COII gene and its usefulness for reconstructing phylogenetic relationships within and among four collembolan families. The collembolan COII gene showed the lowest A + T content of all insects so far examined, confirming that the well-known A + T bias in insect mitochondrial genes tends to increase from the basal to apical orders. Fifty-seven percent of all nucleotide positions were variable and most of the third codon positions appeared free to vary. Values of genetic distance between congeneric species and between families were remarkably high; in some cases the latter were higher than divergence values between other orders of insects. The remarkably high divergence levels observed here provide evidence that collembolan taxa are quite old; divergence levels among collembolan families equaled or exceeded divergences among pterygote insect orders. Once the saturated third-codon positions (which violated stationarity of base frequencies) were removed, the COII sequences contained phylogenetic information, but the extent of that information was overestimated by parsimony methods relative to likelihood methods. In the phylogenetic analysis, consistent statistical support was obtained for the monophyly of all four genera examined, but relationships among genera/families were not well supported. Within the genus Orchesella, relationships were well resolved and agreed with allozyme data. Within the genus Isotomurus, although three pairs of populations were consistently identified, these appeared to have arisen in a burst of evolution from an earlier ancestor. Isotomurus italicus always appeared as basal and I. palustris appeared to harbor a cryptic species, corroborating allozyme data. Received: 12 January 1996 / Accepted: 10 August 1996     

Conservation of Portuguese red-listed bryophytes species in Portugal: Promoting a shift in perspective on climate changes

Knowledge of bryophyte diversity can be an important tool for identifying overall biodiversity hotspots. The distribution of red-listed species is an essential data for biodiversity conservation actions, and the assessment of species' response to climate change scenarios is also a key tool in future conservation strategies. In this study, we examine the response of four phytogeographic assemblages of all Portuguese red-listed bryophytes whose distributions are well documented in Portugal. The red-listed species were selected based on their vulnerability as listed in the new Atlas and Red Data book of Portuguese bryophytes according to the IUCN criteria. The main purpose of this study is to develop predictive distributions of threatened bryophytes grouped according to phytogeographic trends aiming to conserve this bryoflora in future. This is achieved by the identification of relationships between specimens' distributions and environmental ecologically meaningful data, which is known to influence different phytogeographic assemblages. Significant differences were found in all distribution models based on future climate scenarios. Several variables play a vital role in the species' distribution models in present and future environmental conditions.     

The lizard assemblage from Seasonally Dry Tropical Forest enclaves in the Cerrado biome, Brazil, and its association with the Pleistocenic Arc

Aim  To determine if the distributions of lizard species from Seasonally Dry Tropical Forest (SDTF) enclaves within the Cerrado biome in central Brazil are associated with the Tropical Seasonal Forests Region, a recently proposed phytogeographic unit of South America, corroborating the existence of a Pleistocenic Arc of SDTFs.
Location  SDTF remnants in the Paranã River valley, municipality of São Domingos, Goiás, Brazil.
Methods  Lizards were extensively sampled using haphazard sampling, funnel traps, and pitfall traps with drift fences during four expeditions. The composition of the SDTF lizard assemblage was compared with those from other South American phytogeographic regions (Caatinga, Cerrado, Chaco, Llanos, and the dry forests of Colombia and Bolivia), based on the literature and our own unpublished data.
Results  The SDTF lizard assemblage contained 20 species, including 11 species with extensive distributions among the regions considered, seven species shared exclusively with Cerrado localities, a single species shared exclusively with other SDTFs, and one endemic species. The presence of Lygodactylus klugei (Smith, Martin & Swain, 1977), presumably endemic to the Pleistocenic Arc formed by the Tropical Seasonal Forests Region, considerably extends the known distribution of this species, suggesting historical connections between Caatinga and Cerrado SDTF enclaves.
Main conclusions  The composition of the lizard assemblage in Cerrado SDTF enclaves seems to corroborate the recent proposal that the SDTF should be recognized as a phytogeographic unit (or dominium). The presence of disjunct populations and endemic species highlights the urgency of considering the uniqueness of the Paranã River valley SDTFs and the importance of its conservation.     

Conservation planning and viability: problems associated with identifying priority sites in Swaziland using species list data

Conservation planning assessments based on species atlas data are known to select planning units containing ecotones because these areas are relatively species‐rich. However, this richness is often dependent on the presence of adjoining core habitat, so populations within these ecotones might not be viable. This suggests that atlas data may also fail to distinguish between planning units that are highly transformed by agriculture or urbanization with those from neighbouring untransformed units. These highly transformed units could also be identified as priority sites, based solely on the presence of species that require adjoining habitat patches to persist. This potential problem was investigated using bird and mammal atlas data from Swaziland and a landcover map and found that: (i) there was no correlation between planning unit species richness and proportion of natural landcover for both taxa; (ii) the priority areas that were identified for both birds and mammals were no less transformed than if the units had been chosen at random and (iii) an approach that aimed to meet conservation targets and minimize transformation levels failed to identify more viable priority areas. This third result probably arose because 4.8% of the bird species and 22% of the mammal species were recorded in only one planning unit, reducing the opportunity to choose between units when aiming to represent each species. Therefore, it is suggested that using species lists to design protected area networks at a fine spatial scale may not conserve species effectively unless population viability data are explicitly included in the analysis.     

环境因子对橡胶林林下植物多样性的影响

2021年因海南热带雨林国家公园的建立,园内部分人工林停止经营进入次生自然演替状态,使其林下植物较往年更为丰盛,亟待研究。为了摸清人工林的次生自然演替状态及其对环境的适应策略,在海南热带雨林公园橡胶林中设置390个10 m×10 m的样方,在对海南岛公园内植被分布进行全面调查的基础上,研究该区域林下植物组成以及植物群落特征与环境因子的关系。结果表明,(1)维管束植物共有123科455属808种,其中蕨类植物共有21科31属62种、裸子植物3科3属4种、被子植物有99科421属742种(含单子叶植物15科69属120种、双子叶植物84科352属622种);(2)通过对研究区域的植物物种多样性指数与环境因子之间进行RDA分析,共解释橡胶林下物种多样性指数的18.5％。通过蒙特卡罗随机置换检验,有8个环境因素对橡胶林下物种多样性的解释量达到显著水平（P<0.05）,为最干季度平均温度、最湿季度平均温度、平均气温日较差,而混交、胸径、海拔、年降水量和最干季度降水量的影响极为显著（P<0.01）。研究表明,林下植物的多样性受多种环境因素的相互作用影响。其中,温度和降水是综合影响林下植物多样性的关键因素,高温、高湿和干旱等因素对橡胶林下植物多样性产生不利影响。此外,海拔的水热条件也是影响林下植物多样性的重要因素。同时,人工林的状态,如胸径、混交也对林下植物多样性产生重要影响。     

The influence of species pools and local processes on the community structure: a test case with woody plant communities in China's mountains

Understanding how patterns of biodiversity vary among taxonomic levels can provide insights into the mechanisms that regulate the assembly of ecological communities. In this study, we examined the scale and environmental dependence of the relationship between number of species and number of genera/families in woody plant communities to investigate the influences of species pool and local ecological processes on the taxonomic structures of local communities. The data we used are based on a large number of forest plots collected across the eastern part of China and the globe. The results showed that the ratio of the number of genera/families:species and the taxonomic exponents, i.e. the exponents of the genus/family–species relationship, were generally lower than null expectations based on the regional species pool, suggesting that abiotic filtering (e.g. environmental filtering and dispersal limitation) is more important than interspecific competition in shaping local communities. The extent of species pool and the area sampled for local communities both influenced our ability to infer whether local ecological processes were important. In particular, the deviation of the taxonomic ratios and exponents between empirical and null patterns increased as the extent of species pool increased, and the taxonomic exponents declined as area of the local community increased, due partly to the reduced effect of interspecific competition. We conclude that regional species pools and local processes both influenced the taxonomic structure of local woody plant communities, but their effects vary substantially among spatial scales.     

江西九连山常绿阔叶林群落区系特征分析

采用群落生态学的方法对九连山常绿阔叶林的区系组成进行了分析。样地调查结果表明,群落内种类丰富,种子植物共有144科379属647种,其中裸子植物有6科8属9种,单子叶植物21科77属116种,双子叶植物117科294属522种。九连山常绿阔叶林群落的主要表征科为壳斗科、樟科、冬青科、蔷薇科、厚皮香科、山茶科、茜草科、桑科、大戟科等,且多为热带或亚热带科。从样地科的分布型统计看,热带、亚热带与温带成分属的比例为100∶62.8。从属的分布型统计看,有205属热带、亚热带地理分布类型;131属温带地理分布类型,35属世界广布类型和8属中国特有分布类型;热带、亚热带与温带成分的属比例为100∶63.9。九连山常绿阔叶林群落的标志种及其区系组成均较好地反映了本地区热带、亚热带区系成分的组合特征,对于九连山自然保护区天然常绿阔叶林的保护与发展具有重要的参考价值。     

Beta diversity and taxonomic sufficiency: Do higher‐level taxa reflect heterogeneity in species composition?

Aim Virtually all studies exploring the use of taxonomic surrogates in assessing patterns of diversity have focused on clear shifts in the location of samples in multivariate space. The potential use of coarser levels of taxonomic resolution to detect patterns of variability in multivariate space, corresponding to β‐diversity in the case of presence/absence data, remains unexplored. Here we considered five ecological data sets of highly diverse marine molluscan assemblages to test the hypothesis that patterns in compositional heterogeneity would be maintained at coarser levels of taxonomic resolution. Location Italy, Norway, New Zealand and the Arctic. Methods We used multivariate dispersion based on the Jaccard resemblance measure of presence/absence data as a measure of β‐diversity to test the null hypothesis that patterns of heterogeneity in species composition for molluscs would be maintained at coarser levels of taxonomic resolution. Tests to compare β‐diversities among groups (based on distances to centroids and using 9999 permutations) were carried out separately for each of five data sets at the species level and then for each of genus, family, order and class levels. Results Differences in multivariate dispersion at the species level (heterogeneity in the identities of species) were maintained for genera and for families, but not at coarser levels of taxonomic resolution (order or class). These results were consistent across all data sets, despite differences in their spatial scale and extent, geographical location, environmental and habitat features (benthic soft sediments, rocky reefs or kelp holdfasts). Main conclusions These results suggest that either genera or families may be used as effective taxonomic surrogates to detect spatial differences in β‐diversity for molluscs. The use of surrogates can provide considerable sampling efficiencies for biodiversity assessments. We consider, however, that a degree of caution and more work is needed, as heterogeneity at the species level may not be reflected by taxonomic surrogates at smaller spatial scales.     

中国西部干旱地区啮齿动物多样性分布格局

在系统整理我国西部干旱地区啮齿动物的分布资料,获得物种分布范围的基础上,应用GIS软件,基于等面积栅格系统,研究啮齿动物的等级多样性,探讨啮齿动物物种的区域分化特征。结果表明,祁连山地和北塔山、伊犁天山、阿拉套山和阿尔泰山地,以及贺兰山地等处的啮齿动物的属数最高;塔里木盆地中心和藏北高原的属数最低。阿尔泰山南麓、伊犁天山和东祁连山地的啮齿动物科数最多;塔里木盆地中心和藏北高原的科数较少。在青藏高原的周边,寒漠与温性荒漠、荒漠与山地、高原与盆地、荒漠与草原、山地与草原等景观的交界处,多样性指数较高。蒙新荒漠区的啮齿动物的属科数比相对较高,青藏高原的属科数比值较低,但青藏高原的种属数比值相对较高,而且GF指数亦较高。     

安徽合肥大蜀山维管植物区系地理成分研究

在野外调查和标本采集的基础上,对合肥大蜀山植物区系基本组成和科属地理成分进行了分析,并与邻近山地植物区系进行了R/T比值的比较。统计共有维管束植物120科、315属、508种（含种下等级）,其中蕨类植物10科、13属、14种,裸子植物7科、19属、47种,被子植物103科、283属、447种。壳斗科、松科、榆科、槭树科、椴树科和豆科等是该区系的主要表征科,构成了其各森林类型的主要树种组成。种子植物区系成分属的水平上可划分为14个类型,温带成分占有较高比例,热带种类丰富,北温带分布最多（23·81%）,其次为泛热带分布（18·52%）,表现出向北亚热带植物区系明显过渡的特征。中国特有成分较为缺乏。落叶阔叶林仍是该区相对稳定的森林植被类型。与其他山地植物区系R/T比值的比较表明,其热带性质大于安徽鹞落坪和皇藏峪,小于南京幕府山和滁州琅琊山,与南京紫金山和牛首山较为接近。     

关帝山云杉次生林活立木和枯立木的数量特征与分布格局

本研究以山西关帝山庞泉沟自然保护区4 hm²云杉次生林样地2010年和2015年两次调查数据为基础,从物种组成、径级结构、空间格局,以及不同径级活立木与枯立木的空间关联性、枯立木不同径级间的相互关联性4个方面,分析5年间活立木与枯立木的数量特征、分布格局及相互关联性。结果表明: 样地内2010年胸径(DBH)≥1 cm的活立木共有25811株,隶属于11科22属30种,所有个体径级分布呈倒“L”型,个体数量随着径级增大呈断层式减少; 2010—2015年5年间形成枯立木共2145株,涉及5科10属12种,以5～10 cm径级分布为主。在0～50 m尺度上,活立木与枯立木在空间分布上具有一定相似性,表明枯立木的空间格局在一定程度上受活立木空间格局限制。各径级活立木与枯立木空间关联分析表明,随着样地内树木个体径级的增大,对空间资源竞争的加剧可能是导致枯立木产生的主要原因。随着枯立木径级的增大,活立木与枯立木的空间关联性不同程度的减弱,表明环境可能成为大径级枯立木形成的关键因素。从枯立木内部看,5 cm≤DBH<20 cm枯立木与DBH<5 cm枯立木、10 cm≤DBH<20 cm枯立木与5 cm≤DBH<10 cm枯立木、DBH≥20 cm枯立木与5 cm≤DBH<20 cm枯立木整体上都表现为显著正相关,说明枯立木会对后续活立木枯死产生影响。