Effects of forest successional status on microenvironmental conditions,diversity, and distribution of filmy fern species in a temperate rainforest

The vertical distribution of Hymenophyllaceae species has been related to microenvironmental variations around host trees. We addressed the questions: Do the vertical microenvironmental conditions within forest stands of differing successional statuses vary significantly? Does the diversity of Hymenophyllaceae species differ between forest successional statuses? Are the vertical distribution and diversity of Hymenophyllaceae species related more to humidity or light availability? Are there any interspecific differences in the desiccation tolerance of these species which can be related to their vertical distribution? We characterized the microhabitat conditions (vapor pressure deficit [VPD], air relative humidity [RH], and light availability [PAR]) and the vertical distribution of Hymenophyllaceae species in host trees, in both a secondary forest and an old‐growth temperate rainforest in Chile. Chlorophyll fluorescence was used to monitor the integrity of the photosynthetic apparatus during desiccation experiments. The stand basal area, tree height, and leaf area index were all significantly greater in the old‐growth forest stands, but VPD, RH, and PAR showed no significant differences between the two forests. Both successional statuses showed the same amount of filmy fern species in terms of both abundance and diversity. In both successional statuses VPD and RH decreased while PAR increased with the height of the hosts. Regardless of the forest's age, abundance and diversity of filmy ferns were greater in microsites of greater humidity and less light availability. Desiccation tolerance differed significantly among Hymenophyllaceae species. The distribution pattern could be better explained by the specific microenvironmental requirements and desiccation tolerance rather than the forest's successional status.     

Community structure of land flatworms (Platyhelminthes, Terricola): comparisons between Araucaria and Atlantic forest in Southern Brazil

Abstract. Land flatworms (Platyhelminthes: Terricola) are sensitive to environmental changes and might be used as biological indicators of the degree of disturbance of their habitats. Nevertheless, studies on the structure of land flatworm communities are rare. In the present study, we investigated the terrestrial flatworm communities in two types of ombrophilous forest, Atlantic forest and Araucaria forest, aiming to answer the following questions: (1) Is the community structure of the two types of ombrophilous forest different? (2) Are there differences, regarding community structure, among distinct fragments of Araucaria forest? (3) Are there indicators of edge effects in these communities? The study site, the National Park of Aparados da Serra, is mainly covered, at high altitudes, by fragments of Araucaria forest immersed in a matrix of open areas (grasslands) and, in low altitudes, by a continuous Atlantic forest. We conducted monthly surveys in the two types of forest with three replications per forest type over a period of 2 years. Results indicated that: (1) community structure is clearly distinct between the two types of forest, as well as among fragments of the Araucaria forest; (2) there are no apparent edge effects; (3) the diversity indices of the two types of ombrophilous forest are not significantly different (Atlantic forest—H′=2.87, Araucaria forest—H′=2.55; p>0.05); and (4) there are significant differences in diversity indices between two fragments of Araucaria forest (H′=2.92 and 2.47; p<0.001). The following factors could affect community structure: type of vegetation, degree of human disturbance, and abiotic factors, such as pH and temperature.     

西双版纳热带山地雨林群落乔木树种多样性研究

根据块样地资料对西双版纳热带山地雨林树种多样性特征进行了分析.结果表明,在2 500m²的样地上,随着起测胸径递增,各样地乔木个体数和树种丰富度均表现为依次递减;低海拔带上(850～1000 m)的山地雨林(1、2号样地)的各指数值无一定变化规律,较高海拔带上(1200～2000 m)的山地雨林(3～6号样地)的Shannon-Wiener指数和Simpson指数均表现为依次递减,而Pielou均匀度指数则呈依次递增的趋势.较高海拔带上的山地雨林在较小乔木起测胸径(≥2 cm、≥5 cm、≥10 cm)的树种丰富度、多样性和均匀度指数均要明显大于低海拔带上的山地雨林,而两者在较大乔木起测胸径(≥20 cm、≥30 cm、≥50 cm)的各指数值无明显差异.随着取样面积的递增,各样地树种丰富度、多样性和均匀度指数在取样面积递增到2 000m²处均已趋于平缓.     

Ecophysiology and genetic diversity in species of the bamboo Chusquea in the high Andes,Venezuela

ABSTRACT

Background: Woody bamboos of the genus Chusquea grow along a broad range of elevations in the Venezuelan Andes. Their growth-form and density vary along the cloud forest – páramo gradient. In this article, we related ecophysiological traits and population genetic diversity information to explain the distribution of growth-form patterns of Chusquea in the Merida Andes, Venezuela.

Aims: We quantified differences in the ecophysiological response and genetic diversity of scandent cloud forest and shrub-like páramo bamboos of the genus Chusquea, taking in account the differences in their flowering patterns, growth-form and habitat.

Methods: We related low temperature resistance, water relations and leaf gas exchange variables to the growth-form, habitat, flowering patterns and genetic diversity in species of Chusquea. The genetic diversity study was based on Inter Sequence Simple Repeats and Random Amplified Polymorphic DNA markers analysis of cloud forest and páramo populations.

Results: Scandent cloud forest and shrub-like páramo species of Chusquea had a very similar ecophysiological response for all the variables analysed during wet and dry seasons and were capable of enduring freezing temperatures through moderate supercooling. Species associated with the cloud forest – páramo gradient maintained low stomatal conductance and transpiration rates that favoured high leaf water potentials, without limiting photosynthetic rates. Shrub-like bamboos growing above the continuous forest line had a small decline in net photosynthesis rates, associated with an increase in water use efficiency. Both scandent and shrub-like bamboos had a remarkably high genetic diversity, comparable to non-clonal species.

Conclusions: Species of Chusquea in the Venezuelan Andes are a physiologically relatively homogeneous group across a broad elevation gradient. Population genetic diversity appears to be more related with their flowering pattern and habitat conditions than with their growth form.     

Ecosystem recovery in terra firme forests after cutting and burning: a comparison on species richness, floristic composition and forest structure in the Jaú National Park, Amazonia

Six hectares, three in a primary forest and three in a 40 year old secondary forest were inventoried for all trees with Diameter at Breast Height (DNH) of 10 cm or greater in a terra firme forest 200 km north-east of Manaus, central Amazonia in order to compare the difference between structure, species richness and floristic composition. Both species richness and tree density were significantly higher in the upland forest than in the secondary forest. The forest structure pattern analysed (DBH, basal area and estimated dry biomass) did not differ significantly between the two forest types. Similarity indices at species level were only 14%. In the 3 ha of primary forest the number of species varied from 137 to 159, the number of individuals from 639 to 713, total basal area from 32.8 to 40.2 m² and estimate total of above-ground dry biomass (AGBM) from 405 to 560 tons per ha. In the 3 ha of secondary forest, the number of species varied from 86 to 90, the number of individuals from 611 to 653, total basal area from 28.8 to 39.9 m² and estimated total AGBM from 340 to 586 tons per ha. Family Importance Value (FIV) is the sum of relative density, dominance and richness of a family. The most important families in relation to FIV were Burseraceae, Chrysobalanaceae, Lecythidaceae, Myristicaceae, Bombacaceae, Fabaceae and Mimosaceae in the 3 ha of primary forest, while Burseraceae, Lecythidaceae, Sapotaceae, Arecaceae and Cecropiaceae were the most important families in the 3 ha of secondary forest. Importance Value Index (IVI) is the sum of relative density, dominance and frequency of a species. Alexa grandiflora (Caesalpiniaceae), Sckronema micranthum (Bombacaceae) and Pourouma guianensis (Cecropiaceae) were the most important species in relation IVI, in the primary forest, while Eschweilera grandiflora (Lecythidaceae), Protium apiculatum (Burseraceae) and Bertholletia excelsa (Lecythidaceae) were the most important species in the secondary forest. We conclude that species richness was significandy different between the two forests, but that forest structure patterns analysed in this study (DBH, basal area and dry biomass) were similar. This demonstrates that 40 years was sufficient time for the secondary forest to recover the original structure of the primary forest, but not the original species richness. The low species similarity between the two forests indicates that the floristic composition was quite distinct and that the mixture of primary forest and disturbed forest has led to an increase in total species diversity.     

3. THE BIRDS OF LADYSMITH,NATAL

Catry, P., Araújo, A., Cruz, C., Pinheiro, A., Poças, M., Nadum, J., Armelin, M.&; Pereira, J.R. 1999. Are mist-nets suitable for rapid habitat evaluations in the tropics? Results from a study in Guyinea-Bissau. Ostrich 70(2) 134–137

There is an increasing need for rapid habitat evaluations, in the tropics, for conservation purposes. Biodiversity is often assessed by studying relatively well known groups, such as birds. But even birds can be difficult to watch and identify in tropical habitats. Mist-netting is relatively free of observer bias, and allows sampling effort to be standardised. We sampled birds by mist-netting in seven wooded habitats, covering a wide range of levels of anthropogenic disturbance, in the Cufada region, Guinea Bissau. Capture rates, species diversity (as estimated by rarefaction) and originality of the bird communities appeared to be higher in disturbed habitats. Primary forest had the lowest capture rate and the lowest diversity index. Originality was also very low in primary forest. We discuss several possible causes for these patterns and argue that surveys based exclusively on mist-netting can be severely misleading, when comparing bird communities in different habitats.     

Differential survival among life stages contributes to co‐dominance of Abies mariesii and Abies veitchii in a sub‐alpine old‐growth forest

Questions: Are there interspecific differences in mortality and recruitment rates across life stages between two shade‐tolerant dominant trees in a sub‐alpine old‐growth forest? Do such differences in demography contribute to the coexistence and co‐dominance of the two species? Location: Sub‐alpine, old‐growth forest on Mt. Ontake, central Honshu, Japan. Methods: From 1980 to 2005, we recorded DBH and status (alive or dead) of all Abies mariesii and A. veitchii individuals (DBH ≥ 5 cm) in a 0.44‐ha plot. Based on this 25 year census, we quantified mortality and recruitment rates of the two species in three life stages (small tree, 5 cm ≤ DBH < 10 cm; subcanopy tree, 10 cm ≤ DBH < 20 cm; canopy tree, DBH ≥ 20 cm). Results: Significant interspecific differences in mortality and recruitment rates were observed in both the small tree and sub‐canopy tree stages. In this forest, saplings (< 5 cm DBH) are mostly buried by snow‐pack during winter. As a consequence, saplings of A. mariesii, which is snow and shade tolerant, show higher rates of recruitment into the small tree stage than do those of A. veitchii. Above the snow‐pack, trees must tolerate dry, cold temperatures. A. veitchii, which can more readily endure such climate conditions, showed lower mortality rate at the subcanopy stage and a higher recruitment rate into the canopy tree stage. This differential mortality and recruitment among life‐stages determines relative dominance of the two species in the canopy. Conclusion: Differential growth conditions along a vertical gradient in this old forest determine survival of the two species prior to reaching the canopy, and consequently allow co‐dominance at the canopy stage.     

湖南德夯河谷特殊生境典型植物群落特征研究

对德夯河谷特殊生境区典型植物群落的研究表明:1)不同群落物种的组成、结构和多样性均存在较大差异,常绿落叶阔叶混交林的物种最多,达74种;常绿落叶阔叶林的乔木种类最为丰富,有20种;次生竹林的物种多样性指数最高,Shannon-Wiener指数和均匀度分别为6.70、3.83;2)科层次上,各群落内热带分布科数量明显高于温带分布科;属层次上,温带分布成分进一步发展,各个群落内均以温带性质为主.除自然生境条件的差异外,人类不同强度的干扰可能是造成各群落特征变化的主要原因.     

Species diversity,susceptibility to disturbance and tree population dynamics in tropical rain forest

Abstract. In 1964 a census of all trees > 9.7 cm diameter at breast height (DBH) was conducted on 22 plots totalling 13.2 ha in lowland tropical evergreen rain forest on Kolombangara, Solomon Islands. Over the following 30 yr (1964–1994), populations of all individuals > 4.85 cm DBH of the 12 most common tree species and amounts of disturbance have been monitored on a declining number of these plots (in 1994, nine plots totalling 5.4 ha were still being recorded). Between November 1967 and April 1970, Kolombangara was struck by four cyclones, although only two of these caused substantial amounts of damage to the canopy structure. Multivariate analysis has identified six forest types on Kolombangara (Greig-Smith et al. 1967). The species richness and diversity of trees in the 1964 census, turnover rates of the populations monitored over 1964–1975, and the amount of disturbance sustained during a cyclone in 1970, were all positively correlated across five of the forest types. The sixth forest type was a consistent outlier in these analyses and is believed to have been seriously disturbed by humans about a century ago. The floristics, turnover and disturbance data support Connell's intermediate disturbance hypothesis. The most species-rich forest types contained a higher proportion of fast-growing individuals and species that are early-successional and which have low density timber. Properties of these species rendered them more susceptible to damage when struck by the 1970 cyclone. They showed higher turnover rates because disturbance-dependent species are also characterised by higher mortality and recruitment rates. Thus, periodic cyclones appear to favour the maintenance of differences in species diversity and composition between forest types.     

Woody plant communities of isolated Afromontane cloud forests in Taita Hills,Kenya

In the Taita Hills in southern Kenya, remnants of the original Afromontane forest vegetation are restricted to isolated mountain peaks. To assess the level of degradation and the need for forest restoration, we examined how forest plant communities and their indicator species vary between and within remnant patches of cloud forest. We used ordinal abundance data to compare plant communities in eight forest fragments. We also analyzed data on the diversity and abundance of trees in 57 0.1 ha plots to compare tree communities within and between the largest two of these fragments, Ngangao (120 ha) and Mbololo (220 ha). The extant vegetation of the Taita Hills at landscape scale consists of secondary moist montane to intermediate montane forest. There was a high species dissimilarity between fragments (69%). Variation in species composition coincided with an abiotic gradient related to elevation. At plot level, secondary successional species and species of forest edges were most abundant and most frequent. Inferred clusters of plots almost entirely coincided with the two forest fragments. Indicator species associated with forest margins and gaps were more frequent in the smaller of the two forest fragments, while indicators for the larger fragment were more typical for less disturbed moist forest. Abiotic site variability but also different levels of disturbance determine site-specific variants of the montane forest. Conservation efforts should not only focus on maintaining forest quantity (size), but also on forest quality (species composition). Late-successional rainforest species are underrepresented in the woody plant communities of the Taita Hills and assisting restoration of viable populations of cloud forest climax tree species is urgently needed.     

Cloud forest dynamics in the Mexican neotropics during the last 1300 years

Key questions for understanding the resilience and variability of Mexican Neotropical cloud forest assemblages in current and future climate change include: How have human disturbances and climate change affected the dynamics of the cloud forest assemblage? What are the predominant processes responsible for its present day composition and distribution? Are the current conservation strategies for the cloud forest in accordance with preserving its natural variability through time? In this study, the temporal dynamics of the cloud forest in west‐central Mexico over the last ～1300 years were reconstructed using palaeoecological techniques. These included analyses of fossil pollen, microfossil charcoal, and sediment geochemistry. Results indicated that a cloud forest assemblage has been the predominant vegetation type in this region over the last ～1300 years. During this time, however, there have been changes in the vegetation with an apparent expansion of cloud forest from ～832 to 620 cal years bp and a decline from 1200 to 832 cal years bp . Climate change (intervals of aridity) and human disturbances through anthropogenic burning appear to have been the main factors influencing the dynamics of this cloud forest. The spatial heterogeneity reported for high‐altitude forests in this region, in concert with high beta diversity, appears to be a manifestation of the high temporal variability in species composition for these forests. Greater turnover in cloud forest taxa occurred during intervals of increased humidity and is probably representative of a higher temporal competition for resources among the cloud forest taxa. The present results support the current protection scheme for cloud forests in west‐central Mexico where areas are kept in exclusion zones to avoid timber extraction, grazing, and agriculture; this will maintain diversity within these forests, even if there are only a few individuals per species, and enable the forests to retain some resilience to current and future climate change.     

Forest characteristics and population structure of Glyptostrobus pensilis,a globally endangered relict species of southeastern China

The Chinese water pine Glyptostrobus pensilis is the sole surviving species of the genus Glyptostrobus. It is endemic to southern China, central Vietnam, and eastern Laos, and today it is nearly extinct in the wild. Forest community characteristics and population structure of G. pensilis in China have remained un-known up to now. We investigated six swamp forest stands and analyzed their forest community characteristics (i.e. vertical stratification, species composition, and diversity) and population structure, including the frequency distribution of DBH (diameter at breast height) and age-classes as found in Fujian Province, southeastern China. The vertical stratifications of all the forest stands were rather simple. The remaining wild specimens ranged from roughly 15 to some 357 years for an average of ca. 85 years, with only a few individuals less than 20 years old. Compared with the stands and populations of G. pensilis in Vietnam, the taxonomic compositions of the stands in the two regions were different, except for the dominant species-G. pensilis. The Shannon-Wiener index showed the overstory of each stand had much lower diversity (0.26 on average) in Fujian Province than that (1.97 on average) in Vietnam, whereas the diversity indices were about the same (around 2.41) for the understories in the two regions. Furthermore, we discovered 18 G. pensilis seedlings at the study sites in Fujian Province. This discovery demonstrates that G. pensilis regeneration is extremely poor and its populations are declining, although these populations are rela-tively healthier than those in Vietnam.     

Comparative demographic analysis in contrasting environments of Magnolia dealbata: an endangered species from Mexico

The study of population regulation and demography in natural habitats is critical for the conservation of rare and endangered species. We address the impact of cattle exclusion on the demographics of Magnolia dealbata (Magnoliaceae), an endangered species according to IUCN and Federal Mexican laws. Sixteen permanent plots were established, eight of which were enclosed to livestock, in the mountain cloud forest in Coyopolan, Mexico, which has the largest population of M. deadlbata. Censuses of the plots were undertaken annually during three annual cycles to record seed number, recruitment, mortality, and growth (defined as length and diameter at breast height). The effects of two treatments (with and without livestock exclusion) on the dynamics of M. dealbata were investigated using transition matrix models and life table response experiment (LTRE) analysis. Contrary to expectations, there was no significant effect of cattle exclusion on population growth rates (λ). Furthermore, the λ, estimated from the mean transition matrix for both treatments was greater than one. The transitions with the highest elasticity values were similar between the two treatments, while reproductive stage contributed more to differences in population growth rate and were less variable than the non-reproductive stage. LTRE analysis showed that treatment differences had little effect on λ. Livestock exclusion appears to lead more to differences in the arrangement of the values of the transition matrix than to the rate of population growth for M. dealbata.     

大兴安岭呼中地区3种林分的群落特征、物种多样性差异及其耦合关系

准确理解天然林林分群落特征及其与物种多样性耦合关系是提升天然林管理、达到多样性保护的关键。选择大兴安岭呼中地区典型落叶松林、杂木林、白桦落叶松林为研究对象,分别对乔木层、灌木层和草本层特征(高度、胸径、冠幅、盖度等)进行调查并计算丰富度指数、多样性指数和均匀度指数,旨在探究林分间差异及其耦合关系变化。结果表明:(1)乔木层的树高、枝下高表现出杂木林落叶松林白桦落叶松(P0.05);落叶松林的胸径比白桦落叶松林和杂木林的高出6%和11%;灌木层的高度、盖度、地径、冠幅和草本层多度、盖度、高度在森林类型间均未表现出显著差异。(2)3个森林类型的乔、灌、草丰富度指数R、Shannon-Wiener指数及Simpson指数均表现出杂木林最大,乔木层和草本层呈相同规律,即杂木林白桦落叶松林落叶松林,而灌木层表现出杂木林落叶松林白桦落叶松林;白桦落叶松林和杂木林的乔木层均匀度Pielou指数和Alatalo指数约为落叶松林的3倍左右,而在灌木层和草本层在森林类型间差异不显著(P0.05)。(3)典范对应分析(CCA)结果表明林分群落特征和生物多样性关系存在明显森林类型间差异。总体表现为灌木特征(冠幅、地径)、草本层特征(盖度、多度和高度)对多样性均有较大影响;白桦落叶松林和杂木林的胸径对多样性影响明显,而落叶松林的乔木高度(树高、枝下高)对多样性影响较大。杂木林随着灌木盖度、草本高度的增加,草本物种多样性降低、乔木多和灌木物种多样性增加;而落叶松林相同的多样性变化多伴随草本高度增加、多度和盖度变小。灌木层物种多样性增加多与乔木和草本物种多样性降低相伴随,在杂木林中同时伴随着乔木胸径和草本的盖度、多度增大、灌木冠幅变小,而白桦落叶松林则伴随灌木冠幅和草本多度盖度的减小。以上结果表明,林分群落特征与物种多样性存在耦合关系,上述解耦合结果为通过维持良好森林结构、多样性保护具有实践意义。     

塔河源荒漠河岸林群落物种组成、结构与植物区系特征

为了更好地了解荒漠河岸林植被动态与生物多样性维持机制,于塔里木河干流源头荒漠河岸林内建立6个1 hm 2样地,对群落物种组成、数量特征和空间格局等进行综合分析。结果表明,塔河源荒漠河岸林群落结构简单、物种多样性低,共有物种12科15属16种,杨柳科重要值最大(28. 97%),是群落优势建群科。取样面积在0. 04 hm 2时,包括了87. 5%的物种;样地内稀有种和偶见种均占所有物种的12. 5%。植物区系贫乏,单种科、属多,温带成分占绝对优势,古地中海成分也占有重要地位,具典型温带区系性质。样地内 DBH ≥ 1 cm 的活木本个体有2497株,灰胡杨多度占92. 95%,胸高断面积和重要值最大,在群落中占绝对优势地位。群落内科、属、种的数量随植株高度级的增加而减少,垂直结构层次分明,由乔木层、灌木层和草本层构成。样地内所有树种平均胸径15. 57 cm,径级与高度级结构均呈偏正态分布,缺乏高度≤ 2 m的个体,群落更新不良。优势种灰胡杨、胡杨径级结构均呈单峰型,其中胡杨幼树出现断层,灰胡杨幼苗向幼树发展过程中死亡率极高(92. 56%),均为衰退型种群。两个优势种空间格局呈聚集分布,不同生境下随径级增大空间分布格局变化不同;且两个优势种在空间上相互排斥而占据不同生境,暗示着种间竞争与生境异质性是影响荒漠河岸林物种空间分布格局和物种共存的重要因素。     

塔河源荒漠河岸林群落物种组成、结构与植物区系特征

为了更好地了解荒漠河岸林植被动态与生物多样性维持机制,于塔里木河干流源头荒漠河岸林内建立6个1 hm²样地,对群落物种组成、数量特征和空间格局等进行综合分析。结果表明,塔河源荒漠河岸林群落结构简单、物种多样性低,共有物种12科15属16种,杨柳科重要值最大（28.97%）,是群落优势建群科。取样面积在0.04 hm²时,包括了87.5%的物种;样地内稀有种和偶见种均占所有物种的12.5%。植物区系贫乏,单种科、属多,温带成分占绝对优势,古地中海成分也占有重要地位,具典型温带区系性质。样地内DBH ≥ 1 cm的活木本个体有2497株,灰胡杨多度占92.95%,胸高断面积和重要值最大,在群落中占绝对优势地位。群落内科、属、种的数量随植株高度级的增加而减少,垂直结构层次分明,由乔木层、灌木层和草本层构成。样地内所有树种平均胸径15.57 cm,径级与高度级结构均呈偏正态分布,缺乏高度≤ 2 m的个体,群落更新不良。优势种灰胡杨、胡杨径级结构均呈单峰型,其中胡杨幼树出现断层,灰胡杨幼苗向幼树发展过程中死亡率极高（92.56%）,均为衰退型种群。两个优势种空间格局呈聚集分布,不同生境下随径级增大空间分布格局变化不同;且两个优势种在空间上相互排斥而占据不同生境,暗示着种间竞争与生境异质性是影响荒漠河岸林物种空间分布格局和物种共存的重要因素。     

Diversity Patterns in the Flora of the Campo-Ma’an Rain Forest, Cameroon: Do Tree Species Tell it All?

This study describes diversity patterns in the flora of the Campo-Ma’an rain forest, in south Cameroon. In this area, the structure and composition of the forests change progressively from the coastal forest on sandy shorelines through the lowland evergreen forest rich in Caesalpinioideae with Calpocalyx heitzii and Sacoglottis gabonensis, to the submontane forest at higher elevations and the mixed evergreen and semi-deciduous forest in the drier Ma’an area. We tested whether there is a correlation between tree species diversity and diversity of other growth forms such as shrubs, herbs, and lianas in order to understand if, in the context of African tropical rain forest, tree species diversity mirrors the diversity of other life forms or strata. Are forests that are rich in tree species also rich in other life forms? To answer this question, we analysed the family and species level floristic richness and diversity of the various growth forms and forest strata within 145 plots recorded in 6 main vegetation types. A comparison of the diversity within forest layers and within growth forms was done using General Linear Models. The results showed that tree species accounted for 46% of the total number of vascular plant species with DBH ≥1 cm, shrubs/small trees 39%, climbers 14% and herbs less than 1%. Only 22% of the diversity of shrubs and lianas could be explained by the diversity of large and medium sized trees, and less than 1% of herb diversity was explained by tree diversity. The shrub layer was by far the most species rich, with both a higher number of species per plot, and a higher Shannon diversity index, than the tree and the herb layer. More than 82% of tree species, 90% of shrubs, 78% of lianas and 70% of herbaceous species were recorded in the shrub layer. Moreover, shrubs contributed for 38% of the 114 strict and narrow endemic plant species recorded in the area, herbs 29%, trees only 20% and climbers 11%. These results indicate that the diversity of trees might not always reflect the overall diversity of the forest in the Campo-Ma’an area, and therefore it may not be a good indicator for the diversity of shrubs and herbaceous species. Furthermore, this suggests that biodiversity surveys based solely on large and medium sized tree species (DBH ≥0cm) are not an adequate method for the assessment of plant diversity because other growth form such as shrubs, climbers and herbs are under-represented. Therefore, inventory design based on small plots of 0.1 ha, in which all vascular plants with DBH ≥1 cm are recorded, is a more appropriate sampling method for biodiversity assessments than surveys based solely on large and medium sized tree species.     

Phylogenetic relationships in family Magnoliaceae inferred from ndhF sequences

The ndhF sequences of 99 taxa, representing all sections in extant Magnoliaceae, were analyzed to address phylogenetic questions in the family. Magnolia macrophylla and M. dealbata, North American species of Magnolia section Rytidospermum, are placed at the base in the subfamily Magnolioideae although its supporting value is low. In the remaining taxa, several distinctive lineages are recognized: (1) Magnolia, the biggest genus in the family, is not monophyletic; (2) Michelia, including section Maingola of Magnolia subgenus Magnolia, is closely related with Elmerrillia and sections Alcimandra and Aromadendron of Magnolia subgenus Magnolia; (3) the associates of Michelia are grouped with Magnolia subgenus Yulania and section Gynopodium of Magnolia subgenus Magnolia; (4) Pachylarnax forms a clade with sections Manglietiastrum and Gynopodium of Magnolia; (5) a well-supported Manglietia clade is recognized; (6) Caribbean species of section Theorhodon of Magnolia subgenus Magnolia, which are section Splendentes sensu Vázquez-Garcia, are closely allied with New World members of Magnolia subgenus Talauma; and (7) section Rytidospermum of Magnolia subgenus Magnolia and subgenus Talauma are polyphyletic. The separated clades in the molecular tree are considerably different from traditional taxonomic dispositions in the family. The molecular data strongly suggest that a taxonomic realignment of infrafamilial delimitations and compositions should be considered.     

Effects of size,neighbors, and site condition on tree growth in a subtropical evergreen and deciduous broad‐leaved mixed forest,China

Successful growth of a tree is the result of combined effects of biotic and abiotic factors. It is important to understand how biotic and abiotic factors affect changes in forest structure and dynamics under environmental fluctuations. In this study, we explored the effects of initial size [diameter at breast height (DBH)], neighborhood competition, and site condition on tree growth, based on a 3‐year monitoring of tree growth rate in a permanent plot (120 × 80 m) of montane Fagus engleriana–Cyclobalanopsis multiervis mixed forest on Mt. Shennongjia, China. We measured DBH increments every 6 months from October 2011 to October 2014 by field‐made dendrometers and calculated the mean annual growth rate over the 3 years for each individual tree. We also measured and calculated twelve soil properties and five topographic variables for 384 grids of 5 × 5 m. We defined two distance‐dependent neighborhood competition indices with and without considerations of phylogenetic relatedness between trees and tested for significant differences in growth rates among functional groups. On average, trees in this mixed montane forest grew 0.07 cm year^?1 in DBH. Deciduous, canopy, and early‐successional species grew faster than evergreen, small‐statured, and late‐successional species, respectively. Growth rates increased with initial DBH, but were not significantly related to neighborhood competition and site condition for overall trees. Phylogenetic relatedness between trees did not influence the neighborhood competition. Different factors were found to influence tree growth rates of different functional groups: Initial DBH was the dominant factor for all tree groups; neighborhood competition within 5 m radius decreased growth rates of evergreen trees; and site condition tended to be more related to growth rates of fast‐growing trees (deciduous, canopy, pioneer, and early‐successional species) than the slow‐growing trees (evergreen, understory, and late‐successional species).     

川西亚高山森林不同恢复途径物种组成和群落结构动态变化

川西亚高山森林作为西南林区主体,是长江上游的生态屏障,该区域植被恢复方式主要为人工恢复和自然恢复,比较不同恢复方式下森林的物种组成和群落结构动态变化,对于川西亚高山森林恢复与重建有重要的意义,可以为制定合理的森林管理策略提供科学依据。基于茂县山地生态系统定位研究站不同恢复模式形成的的华山松人工林、油松人工林和自然恢复的次生林野外调查数据,分析了2005-2020年乔、灌、草三个层次的群落结构特征和多样性。结果表明:(1)不同恢复途径下,乔木层物种数都呈现增加趋势,华山松人工林、油松人工林、自然恢复的次生林乔木层物种数分别增加了11种、7种、8种;(2)华山松人工林中华山松重要值从48.06%降低到31.1%,乡土阔叶树种四川蜡瓣花进入乔木层,2020年重要值增大至21.62%,油松人工林中油松重要值逐渐降低,从43.59%降至29.76%;自然恢复的次生林中,乡土树种锐齿槲栎逐渐成为第一优势种,2020年重要值增至19.9%。(3) 华山松人工林、油松人工林和自然恢复的次生林中,温带区系成分分别占总属数的71.43%,80.77%和84%,温带区系特征明显。(4)华山松人工林和油松人工林乔木层径级结构均为偏正态分布;而自然恢复的次生林径级分布呈倒"J"形,以小径级个体为主。(5)不同林型的乔木层高度在15年间呈现增加的趋势,具体表现为油松人工林>华山松人工林>自然恢复的次生林。(6)乔木层Shannon-wiener指数和 Simpson指数均表现为自然恢复的次生林显著大于两个人工林,丰富度指数和均匀度指数表现为油松人工林最大;灌木层4个多样性指数均表现为油松人工林最大;草本层的丰富度指数、Shannon-wiener 指数和 Simpson 指数均表现为油松人工林较大,均匀度指数没有显著差异。结论:人工林恢复速度大于自然恢复的次生林,但自然恢复的次生林更新能力更强,且更有利于多样性的保存。两个人工林逐渐由常绿针叶林演替为以常绿针叶树为主的针阔混交林,自然恢复的次生林演替为以常绿阔叶树为主的针阔混交林。