Pollination and phenology of flowers in the canopy of two contrasting rain forest types in Amazonia,Colombia

The main objective of this investigation was to study the pollination characteristics of two types of Amazonian rain forest at plant community level. Seasonally inundated forest was compared with upland (tierra firme) forest. The study focused on plant species in the canopy. The pollination spectra show that in both forests most canopy trees and lianas are pollinated by small bees, large bees, butterflies or by small, relatively unspecialized insects. In the upland forest small bees are the most important pollinators (32% of all species of trees and lianas are pollinated by them), whereas large bees are predominant in the floodplain (22%). Other pollinators, like hummingbirds, bats, moths, and beetles are less common (>10%), but always somewhat more important in the flood plain than in the upland forest. Bees are the most common pollinators of epiphytes. In the flood plain forest, flies are also important as epiphyte pollinators (19%), whereas in the upland forest hummingbirds pollinate more epiphytes. The phenological patterns are quite similar in both the upland and the flood plain. We found a peak in flowering in the transition period between the wet and the dry season. Flowering activity was lowest during the wet season. Differentiation in sexual systems was correlated with life form. Dioecy and monoecy were found mostly among tree species. Most species of all life forms though were hermaphroditic. No difference with respect to the relative importance of sexual systems was found between the two forest types.     

Exploring the relationship between canopy height and terrestrial plant diversity

A relatively small number of broad-scale patterns describe the distribution of biodiversity across the earth. All of them explore biodiversity focusing on a mono or bi-dimensional space. Conversely, the volume of the forests is rarely considered. In the present work, we tested a global correlation between vascular plant species richness (S) and average forest canopy height (H), the latter regarded as a proxy of volume, using the NASA product of Global Forest Canopy Height map and the global map of plant species diversity. We found a significant correlation between H and S both at global and macro-climate scales, with strongest confidence in the tropics. Hence, two different regression models were compared and discussed to provide a possible pattern of the H–S relation. We suggested that the volume of forest ecosystems should be considered in ecological studies as well as in planning and managing natural sites, although in this first attempt, we cannot definitively prove our hypothesis. Again, high-resolution spatial data could be highly important to confirm the H–S relation, even at different scales.     

林冠截留与大气降水关系的数学模型

本文依据实测数据及有关资料,对林冠截留进行了深入细致的分析,并以物理化学中溶液吸附理论引伸出的上升-饱和函数关系曲线为类比,提出了一组关于林内雨量率、截留率、截留量与大气降水关系的新的数学模型。模型中的3个参数μm、P_o、k水文学意义明确,拟合效果较好,对深入研究林冠截留具有一定现实意义。 林内雨量率公式: 林冠截留率公式: 林冠截留量公式:     

森林冠层昆虫多样性研究方法

森林冠层是森林昆虫栖息、取食、避敌的重要生境,其中生活着十分丰富的昆虫物种。但由于乔木树体高大,冠层难于接近,在很大程度上限制了冠层昆虫多样性的研究。冠层昆虫类群结构的划分和冠层昆虫取样技术也是冠层昆虫多样性研究的重要基础。文章综述当前冠层接近和冠层昆虫抽样技术的最新进展,并评述冠层昆虫类群结构划分的方法。     

Contrasting relationships between species diversity and genetic diversity in natural and disturbed forest tree communities

? This study aimed to reveal species-genetic diversity correlations (SGDCs) and their underlying mechanisms in natural and disturbed forests. ? A community survey and molecular analyses were carried out to compare species diversity (SD), the genetic diversity of the dominant tree species Euptelea pleiospermum (GD), the altitudinal patterns of SD and GD, SGDC, genetic differentiation (F(ST) ), community divergence (F(ST) -C), effective population size (N(e) ), and recent migration rate between mountain riparian forests along the Yandu (natural) and Nan (disturbed) rivers. ? In natural forests, both SD and GD showed a unimodal altitudinal pattern and GD was positively correlated with SD, whereas a unimodal pattern and positive SGDC were not found in the disturbed forests. SD and F(ST) at the natural sites were higher than those at the disturbed sites. However, there were no significant differences in GD, F(ST) -C, N(e) or recent migration rate between the natural and disturbed sites. ? A correlation between the patterns of SD and GD along a geographical gradient (e.g. altitude) is an important driver of positive SGDC. The absence of positive SGDC in the disturbed forests may result from reduced SD but unaffected GD, indicating nonparallel changes in SD and GD. This study furthermore cautions against generalizations about changes in SD and GD following disturbance.     

Leaf trait plasticity in six forest tree species of central Amazonia

Tropical rainforest trees adjust leaf traits during ontogeny to cope with changes in the physical environment and maximize their carbon uptake. The aim of this study was to determine the plasticity index (P_I) of leaf traits in understory and canopy leaves of six Amazonian tree species. In four of the six species the P_I of leaf traits varied within species, and in four of the ten leaf traits assessed, the P_I differed between species. The greatest P_I values were found for stomatal density (D_s) and CO₂-saturated photosynthesis, and the lowest ones were found for stomatal size, and leaf thickness. Despite the differences in P_I values within species, the mean P_I was similar in all the six species. As the saplings grow toward the canopy, the strategy to increase carbon uptake involves increasing D_s and leaf nitrogen and reducing stomatal size.     

天然次生林和4种人工林树冠层蚂蚁功能多样性研究

为了探讨不同类型林地中树冠层蚂蚁功能多样性的变化,本研究采用树栖蚂蚁陷阱法调查云南省绿春县天然次生林和4种人工林的树冠层蚂蚁群落,并调查了植物多样性及植物垂直密度变化。测定54种蚂蚁的头长、头宽、胸长和后足腿节长,并计算和比较了不同类型样地间的功能丰富度、功能均匀度和功能离散度的差异。结果表明:(1)不同类型林地间树冠层蚂蚁的功能丰富度指数(FR_ic)有显著差异,紫胶林和紫胶林-玉米混农林显著高于桉树林、天然次生林和橡胶林,同时橡胶林显著高于桉树林;不同类型林地间树冠层蚂蚁的功能均匀度指数(FE_ve)有显著差异,天然次生林和紫胶林显著高于桉树林。不同类型林地间树冠层蚂蚁的功能离散度指数(FD_iv)有显著差异,桉树林、橡胶林和紫胶林显著高于紫胶林-玉米混农林,且橡胶林显著高于天然次生林。(2)树冠层蚂蚁功能均匀度随枯落物盖度的增加而升高;功能离散度随枯落物盖度、草本植物盖度和>300 cm处的垂直密度的增加而升高。不同林地类型中紫胶林的树冠层蚂蚁功能多样性相对较高,而这其中枯落物盖度、草本植物盖度和>300 cm处的垂直密度等环境因素起到一定积极的作用,因此对人工林进行合理的管护有利于生态系统功能的实现和保护。     

Abundance and diversity of Homoptera in the canopy of a tropical forest

Abstract. 1. A series of samples of Homoptera was obtained by fogging the canopy of Luehea seemannii trees in tropical forest in the Panama Canal Zone at three different times of the year.
2. The peak of abundance occurs around July (at least 11.8 individuals/m²), in the early wet season, at a time when most of the trees in the forest, including Luehea are producing new leaves.
3. Minimum abundance occurs in March (at least 3.5 individuals/m²), in the late dry season.
4. The samples obtained are some 35% richer in species per given number of individuals than light trap samples taken simultaneously in a similar forest some 6 km away from the present sampling site.
5. The data show that the effect of intensive light trapping on the populations of Homoptera in the forest is virtually negligible.
6. For a given sample size the tropical samples are many times richer in species than samples from temperate areas.     

Niche versus chance and tree diversity in forest gaps

Studies that are unprecedented in scale, detail or approach show that niche partitioning contributes less, and chance events more, than expected to maintaining tree species richness via gap dynamics in tropical and temperate forests. Some tree species are differentially adapted for regeneration in different gap microenvironments. However, the stochastic availability of gaps, and limited recruitment of juveniles, mean that gaps are filled mostly by chance occupants rather than by best adapted species. This chance survival can slow competitive exclusion and maintain tree diversity. Gap dynamics do not explain the latitudinal gradient in tree richness.     

Species richness and distribution of understorey bryophytes in different forest types in Colombian Amazonia

Abstract

The first bryophyte survey results from Colombian Amazonia are presented. Bryophyte species, differentiated into mosses and liverworts, and further into four life-form classes, were sampled in 0.1-ha plots. These plots were distributed over four landscape units in the middle Caquetá area: floodplains, swamps, terra firme forests and white-sand areas. The total numbers of bryophyte species in the units were 50, 45, 45 and 32, respectively. The plots in floodplains and swamps were richer in moss species than the terra firme and white-sand plots, suggesting that coexistence of many moss species is favoured by high humidity. Moss species with fan life-forms preferred floodplains. On the other hand, liverwort species richness was highest in white-sand plots, which suggests that light incidence controls liverwort species-richness, perhaps more than humidity. All plots from the floodplain of the Caquetá River differed remarkably in species composition (of both mosses and liverworts) from the other landscape units. This may be due to the unique properties of this varzea system where, during yearly flooding events, soil, dead logs and stems are covered with a fresh layer of nutrient-rich fine silt, enhancing the surface for colonization and improving the conditions for productive bryophyte growth compared with elsewhere in the middle Caquetá area.     

天童森林植被的群落稳定性与物种多样性关系的研究

本文依据天童森林群落样地的数据,分析了群落稳定性与物种多样性的关系。结果表明不能单纯以物种多样性的高低来判断某具体群落的稳定性,使用群落各层次的物种多样性指数和群落优势种群的年龄结构来衡量群落的稳定性较为合适     

Herbivorous insect species in the tree canopy of a relict South African forest

Abstract.

• 1 The herbivorous insects on twelve species of evergreen broadleafed trees were repeatedly sampled over a period of 11 months in a small relict forest on the east coast of South Africa. This extraordinarily speciose forest patch has an unusually high proportion of endemic tree species, some of which are extremely rare.
• 2 The insect herbivore fauna (number of species) seems to be markedly depauperate compared to that reported on native, broadleafed trees from other parts of the world. Some possible reasons for this are discussed.
• 3 The total number of herbivorous insect species on each tree species was strongly correlated with the local relative abundance of the host plant species.
• 4 There was no relationship between the total number of insect herbivore species on each tree species and the relative taxonomic isolation of the trees. The proportion of seemingly unique (= specialist) herbivorous insect species (i.e. those that occurred on one tree species only) was greatest on taxonomically isolated trees.
• 5 A fundamental deficiency in the interpretation of the data in this study, and of many other similar studies that report on the number of insect species on plants, is discussed, namely the lack of clarity on the closeness of the association between individual insect herbivore species and their respective host plants.

     

Study on canopy disturbance regime and mechanism of tree species diversity maintenance in the lower subtropical evergreen broad-leaved forest,South China

ABSTRACT

The canopy disturbance, the gap environment, gap regeneration and maintenance of tree species diversity in the lower subtropical evergreen broad-leaved forest (LSEBF) of South China were studied in this paper. The most common manner of gap formation in the forest was by stem breakage. Most gaps were formed by two gap makers. The sizes of most expanded gaps (EG) and canopy gaps (CG) were in the range of 100 – 300 m² and 50 – 100 m², respectively. The ecological factors in gaps were analysed on the basis of contrasting measurement of the microclimatic regimes in gaps of different sizes and in non-gap stands. Tree species in the LSEBF were classified into 5 ecological species groups on the bases of their changes in order of importance values in gaps and in non-gap stands. Most of the species reached their peak of regeneration density around the gap sizes of 100 m² and 500 m². The curves of regeneration density vs. gap age for major species revealed two types. Regeneration densities of most species, and species diversity indices in gaps were greater than those in non-gap stands.     

Macrofungal diversity and ecology in four Irish forest types

The macrofungal communities of Irish native tree species (ash and oak) and exotic tree species (Scots pine and Sitka spruce) forests were examined through the collection of sporocarps over 3 yr. Sampling of 27 plots revealed 186 species of macrofungi, including 10 species new to Ireland. The species richness of non-native Sitka spruce and Scots pine forests was similar to that of native oak forests. However, specific communities of macrofungi existed in each of the forest types as confirmed by non-metric multidimensional scaling and multi-response permutation procedure. Indicator species analysis was used to identify macrofungi which are indicative of the four forest types. The oak community lacked certain species/genera known to be distinctive of oak woods in Britain, possibly due to low inoculum availability as a result of historic removal of Ireland’s oak forests. Our results indicate that, while being similar to native forests in species richness, non-native forests of Sitka spruce and Scots pine in Ireland harbour many fungal species which are not typical of native forests, particularly members of the genus Cortinarius.     

On the relationship between sample plot size and beta diversity in boreal coniferous forests

Nested sample plots of three sizes (16, 1, and 1/16 sq. m) from three different studies of Norwegian coniferous forests have been subjected to DCA ordination using the same choice of options. At each sample plot size, species quantities are recorded as frequency in 16 subplots. Beta diversity, measured as length of the first DCA axis, invariably increased upon lowering of sample plot size. The same applied to the eigenvalues of the axes. This is explained as a consequence of the weakening of structure in the data matrices when the fine-grained patterns of the vegetation are emphasized.     

Deposition and canopy exchange processes in central-German beech forests differing in tree species diversity

Atmospheric deposition is an important nutrient input to forests. The chemical composition of the rainfall is altered by the forest canopy due to interception and canopy exchange. Bulk deposition and stand deposition (throughfall plus stemflow) of Na⁺, Cl^?, K⁺, Ca²⁺, Mg²⁺, PO ₄ ^3? , SO ₄ ^2? , H⁺, Mn²⁺, Al³⁺, Fe²⁺, NH ₄ ⁺ , NO ₃ ^? and N_org were measured in nine deciduous forest plots with different tree species diversity in central Germany. Interception deposition and canopy exchange rates were calculated with a canopy budget model. The investigated forest plots were pure beech (Fagus sylvatica L.) plots, three-species plots (Fagus sylvatica, Tilia cordata Mill. or T. platyphyllos Scop. and Fraxinus excelsior L.) and five-species plots (Fagus sylvatica, T. cordata or T. platyphyllos, Fraxinus excelsior, Acer platanoides L., A. pseudoplatanus L. or A. campestre L. and Carpinus betulus L.). The interception deposition of all ions was highest in pure beech plots and was negatively related to the Shannon index. The stand deposition of K⁺, Ca²⁺, Mg²⁺ and PO ₄ ^3? was higher in mixed species plots than in pure beech plots due to higher canopy leaching rates in the mixed species plots. The acid input to the canopy and to the soil was higher in pure beech plots than in mixed species plots. The high canopy leaching rates of Mn²⁺ in pure beech plots indicated differences in soil properties between the plot types. Indeed, pH, effective cation exchange capacity and base saturation were lower in pure beech plots. This may have contributed to the lower leaching rates of K⁺, Ca²⁺ and Mg²⁺ compared to the mixed species plots. However, foliar analyses indicated differences in the ion status among the tree species, which may additionally have influenced canopy exchange. In conclusion, the nutrient input to the soil resulting from deposition and canopy leaching was higher in mixed species plots than in pure beech plots, whereas the acid input was highest in pure beech plots.     

Fire frequency and tree canopy structure influence plant species diversity in a forest-grassland ecotone

Disturbances and environmental heterogeneity are two factors thought to influence plant species diversity, but their effects are still poorly understood in many ecosystems. We surveyed understory vegetation and measured tree canopy cover on permanent plots spanning an experimental fire frequency gradient to test fire frequency and tree canopy effects on plant species richness and community heterogeneity within a mosaic of grassland, oak savanna, oak woodland, and forest communities. Species richness was assessed for all vascular plant species and for three plant functional groups: grasses, forbs, and woody plants. Understory species richness and community heterogeneity were maximized at biennial fire frequencies, consistent with predictions of the intermediate disturbance hypothesis. However, overstory tree species richness was highest in unburned units and declined with increasing fire frequency. Maximum species richness was observed in unburned units for woody species, with biennial fires for forbs, and with near-annual fires for grasses. Savannas and woodlands with intermediate and spatially variable tree canopy cover had greater species richness and community heterogeneity than old-field grasslands or closed-canopy forests. Functional group species richness was positively correlated with functional group cover. Our results suggest that annual to biennial fire frequencies prevent shrubs and trees from competitively excluding grasses and prairie forbs, while spatially variable shading from overstory trees reduces grass dominance and provides a wider range of habitat conditions. Hence, high species richness in savannas is due to both high sample point species richness and high community heterogeneity among sample points, which are maintained by intermediate fire frequencies and variable tree canopy cover.     

Assessing the scale-specific importance of niches and other spatial processes on beta diversity: a case study from a temperate forest

Niche processes and other spatial processes, such as dispersal, may simultaneously control beta diversity, yet their relative importance may shift across spatial and temporal scales. Although disentangling the relative importance of these processes has been a continuing methodological challenge, recent developments in multi-scale spatial and temporal modeling can now help ecologists estimate their scale-specific contributions. Here we present a statistical approach to (1) detect the presence of a space–time interaction on community composition and (2) estimate the scale-specific importance of environmental and spatial factors on beta diversity. To illustrate the applicability of this approach, we use a case study from a temperate forest understory where tree seedling abundances were monitored during a 9-year period at 40 permanent plots. We found no significant space–time interaction on tree seedling composition, which means that the spatial abundance patterns did not vary over the study period. However, for a given year the relative importance of niche processes and other spatial processes was found to be scale-specific. Tree seedling abundances were primarily controlled by a broad-scale environmental gradient, but within the confines of this gradient the finer scale patchiness was largely due to other spatial processes. This case study illustrates that these two sets of processes are not mutually exclusive and can affect abundance patterns in a scale-dependent manner. More importantly, the use of our methodology for future empirical studies should help in the merging of niche and neutral perspectives on beta diversity, an obvious next step for community ecology. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Intermediary disturbance increases tree diversity in riverine forest of southern Brazil

Floods are frequently associated with disturbance in structuring riverine forests and they lead to environmental heterogeneity over space and time. We evaluated the distribution of tree species, ecological groups, species richness and diversity from the point bar to the slope of a riverside forest in southern Brazil (Lat. 30°01′S, Long. 52°47′W) to analyze the effects of flooding on soil properties and forest structure. A plot of 50 × 200 m divided in five contiguous transects of 10 × 200 m parallel to the river was installed, where we measured all the individual trees with pbh ≥ 15 cm. A detailed topographical and soil survey was carried out across the plot and indicated significant differences in organic matter and most mineral nutrients through the topographical gradient. The 1,229 surveyed individuals belonged to 72 species and 35 families. We used Partial CCA and Species Indicator Analysis to observe the spatial distribution of species. Both analyses showed that species distribution was strongly related to the flooding gradient, soil properties and also by space and pure spatial structuring of species and environmental variables (spatial autocorrelation), although a large part of variation remains unexplained. The ecological groups of forest stratification, plant dispersal and requirements for germination indicated slight differences among frequently, occasional and non-flooded transects. Species richness and diversity were higher at intermediate elevations and were associated to the increased spatial–temporal environmental heterogeneity. Across the plot, the direct influence of flooding on tree species distribution created a vegetation zonation that is determined by predicted ecological traits.