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1.
Climbers play different roles in forest biology and ecology and are the first to be eliminated during forest clearing but little is known about the species composition, distribution and relationship with tree species of this group of plants of tropical forest. This study thus investigated the species composition, abundance and tree relationship of climbers along altitudinal gradient in four 0.06 ha plots in a secondary forest at Ile‐Ife, Nigeria. All trees ≥10 cm g.b.h were examined for the presence of climbers in the plots. There were 49 climber species consisting of 35 liana and fourteen vine species distributed over 41 genera and 28 families in the forest. Lianas contributed 34% and vines 13.7% of the plant species in the forest. Climber basal area, density, number of species, genera and families increased with altitude. Forty‐two per cent (42%) of the trees in the forest carried climbers. There was significant positive correlation (P ≤ 0.05) between girth sizes of host trees of 31–50 cm with the girths of climbers on them indicating that trees of these girth sizes are highly susceptible to climber infestation. Tree species host density and size are important factors in determining the presence of climbers on a tree.  相似文献   

2.
Questions: Which factors best predict the probability of elephant and frost damage in Kalahari sand woodland savanna? What is the association between tree mortality and the disturbance regime? Location: Western Zimbabwe. Methods: Elephant and frost damage, topkill, and whole‐plant mortality were quantified in ten common tree species in a Kalahari sand savanna in Zimbabwe. Individual trees were tagged in 20 plots and monitored over a two‐year period. A model selection approach was used to test the association between the probability of damage and size, prior damage, and neighbourhood effects, and to investigate the effect of damage on mortality. Results: Elephant damage differed strongly among species, and was not influenced by neighbourhood effects or prior disturbance. Frost damage also varied across species, and declined as a function of stem size and neighbourhood tree cover, and ‐ against expectations ‐ prior disturbance. Topkill increased as a function of elephant and frost damage, but was lower in previously damaged than in undamaged trees. Conclusions: Frost and elephant damage are influenced by community composition, and frost damage is also correlated with community structure and prior disturbance. Frost is an important and generally overlooked disturbance agent in southern African woodlands, where it may play a key role in association with other disturbance factors ‐ such as elephant herbivory ‐ that reduce woodland canopy cover.  相似文献   

3.
We studied the relationships between size, growth, and survival for two functional groups, the persistent canopy and understory dominant tree species in a tropical gallery forest in Southeastern Brazil. In 28 plots of 10?×?30?m we tagged, identified, and measured the diameter of all trees with diameter at ground level ??5?cm in 1993/1994, 1998, and 2004. We choose the three dominant canopy species (Protium spruceanum, Copaifera langsdorffii, and Pera glabrata) and two dominant understory species (Ixora brevifolia and Trichilia emarginata) for the comparisons. We assessed the relationship between previous growth rates and mortality, variation in growth and mortality rates among size classes, and temporal correlations in growth rates. Trees (whole community) with null or negative growth had a higher mortality, although this effect was not significant for individual species. Growth patterns were consistent along consecutive periods of evaluation for canopy species, but not for understory species. Canopy species had higher and more variable growth rates than understory species, which we attribute to greater access to light at the canopy level and also to a wider range of light conditions experienced during growth. Canopy species and one understory species, T. emarginata, showed accelerated growth as they became larger. Mortality rates were higher for the smallest trees for the community overall and for P. spruceanum.  相似文献   

4.
Question: How does typhoon‐related disturbance (more specifically, disturbance in the understorey due to tree‐fall and branch‐fall) affect different species mortality rates in a vertically well‐structured forest community? Location: Cool‐temperate, old‐growth forest in the Daisen Forest Reserve, Japan. Methods: We investigated the canopy dynamics and mortality rate trends of trees ≥5 cm diameter at breast height in a 4‐ha study plot, and analysed the effects of tree diameter and spatial structure on the mortality risks for major tree species in the understorey. Results: Significant differences were found in the mortality rates and proportions of injured dead stems between census periods, which were more pronounced in the understorey than in the canopy. Acer micranthum, which showed increased mortality during typhoon disturbance periods, had a clumped distribution. In contrast, Acer japonicum and Viburnum furcatum, which showed similar mortality rates between census periods, had a loosely clumped spatial distribution and a negative association with canopy trees, respectively. In the understorey stems of Acanthopanax sciadophylloides and Fagus crenata, whose spatial distribution patterns depended on canopy gaps, significant increases in mortality rates were observed only during severe typhoon‐related disturbance periods. Conclusions: The sensitivity of trees to typhoon‐related canopy disturbance is more pronounced in the lower layers of vertically structured forest communities. Differences in mortality patterns generated through the combined effects of spatial variation in disturbance regime and species‐specific spatial distribution patterns (spatial aggregation, association with canopy trees, and canopy gap dependency) contribute to the co‐existence of understorey species in forest communities that are subject to typhoon‐related disturbance.  相似文献   

5.
不同生境和森林内薇甘菊的生存与危害状况   总被引:86,自引:3,他引:86  
对薇甘菊(Mikania micrantha H.B.K)在不同生境下生长状况及其对其它植物的危害程度的研究表明,这种热带杂草是喜光、好湿的。薇甘菊伴生物种以藤本植物居多。其中葛藤和五爪金龙出现的频度最大。薇甘菊及其伴生种通过攀爬树冠,形成盖幕作用而对其它植物造成危害。在森林内薇甘菊危害的对象主要是低矮的乔木对高大乔木影响不大。  相似文献   

6.
Question: In a southern temperate rain forest, we addressed three questions: (1) Does the abundance of climbing plants increase with light availability? (2) Do host tree species differ in their susceptibility to vine infestation? (3) How does the relationship between host tree trunk diameter and relative abundance of vines vary with their climbing mechanism? Location: Two sites in the temperate evergreen rain forest of southern Chile: Puyehue (40°39′S, 72°09′W; 350 m a.s.l.) and Pastahue (42°22′S, 73°49′W; 285 m a.s.l.). Methods: We sampled vines in 60 25‐m2 plots, with 20 plots in each of three light environments: mature forest, forest edges and canopy gaps. In each plot, for every tree ≥1.50‐m tall of any diameter we counted and identified all climbing plant individuals at a height of 1.30 m. We also counted, measured (trunk diameter at 1.30 m) and identified all these trees, and determined prevalence of vine infestation for each tree species. Results: Light availability in forest plots did not affect vine abundance when the number and size of host trees was taken into account. Overall, vine abundance increased with host tree trunk diameter. Tree species did not differ in the prevalence of vine infestation. The relative abundance of stem twiners and adhesive climbers decreased and increased with trunk diameter, respectively. The densities of stem twiners and adhesive climbers were negatively correlated across the forest. Conclusion: We provide further evidence that the pattern of vine abundance is independent of light availability in southern temperate rain forests, in contrast to results commonly reported for tropical rain forests. We also show that support suitability across the forest varies with the mechanism by which vines climb, probably due in part to biomechanical constraints and in part to vine interspecific competition, a virtually unexplored ecological factor.  相似文献   

7.
Liana is a life form that possesses high importance in many Neotropical forests. Density of climbers apparently increases with the intervention rate (e.g. logging). The aim of this work is to characterize the structure, floristic composition and soils of a sector classified as Liana Forest (LF). We identified an LF sector in a not-logged area; three 1 ha square plots were measured (individuals ≥ 10 cm dbh, “diameter at breast height”). In each plot, we evaluate four 100 m2 square understory subplots (all spermatophyta individuals < 10 cm dbh). LF has a low canopy ( < 15 m) and is dominated by Alexa imperatricis and Pentaclethra macroloba. Basal area (20.4 m2ha? 1) and diversity (H′ = 2.6) are lower than other surrounding plots. Understory is dominated by gnarled climbers, and the most important are Cheiloclinium hippocrateoides and Bauhinia scala-simiae. Soil is extremely acidic, with very low fertility but is similar to neighboring places. We conclude that LF was neither originated by edaphic restrictions nor logging; LF probably suffered a hurricane wind that fell down most of the canopy trees, thick individuals of climber species also disappeared, and the current successional stage favors a recovery dominated with thin individuals of this life form.  相似文献   

8.
Vetaas  Ole R. 《Plant Ecology》1997,132(1):29-38
Non-epiphytic species richness was studied in different disturbance classes within a Quercus semecarpifolia forest. Nine disturbance classes were defined according to the degree of biomass removal (lopping) and their spatial mixture. Six of these were observed in the study area. The species were divided into three functional groups: climbers, phanerophytes, and field-layer plants. The primary aim was to test if there is an elevated species richness under an intermediate disturbed canopy for (i) all vascular plants, (ii) lianas, (iii) phanerophytes and (iv) field-layer species. The richness of the different plant groups and all species were fitted against the disturbance gradient by means of Generalized Linear Models (GLM). Other environmental variables such as altitude, potential solar radiation, light intensity, canopy cover and soil parameters were also evaluated as predictors. Disturbance classes, canopy cover and light intensity were combined into a new variable, disturbance-complex, using Principal Component Analyses.Phanerophytes did not respond to any variable. Climbers were mostly related to pH and canopy cover, and were the only group related to altitude, nitrogen and loss-on-ignition. Herbaceous plants and total species richness showed a unimodal response to disturbance classes and the complex disturbance gradient, which supports the intermediate disturbance hypothesis. Relative radiation and slope also supported a unimodal response in herbaceous plants, but disturbance had a significant additional contribution to this pattern. The most significant predictor for these two groups was pH. The responses to organic carbon and phosphorus were not significant for any of the subsets.The results indicate that a small-scale lopping regime will enhance species richness of vascular plants; only a few species in the intermediate disturbed forest are weedy ruderals. In such a situation, the conservation policy may accept small-scale human impact as part of the forest landscape.  相似文献   

9.
We aimed to determine which factors explain the relative abundances of climbing plants in a tropical sandy coastal plant community, locally called restinga, in SE-Brazil, where facilitation is an important mechanism controlling shrub and tree diversity. The factors examined were: associations with host trees and shrubs, environmental conditions, associations with herbs and space. We surveyed a total of 84 vegetation patches within two hectares of open restinga vegetation. Climbers, trees, shrubs and herbs were sampled using an adapted cover pin frame approach. Partial constrained ordination (pRDA) was used to partition the variation of climber species relative abundances into four sources: trees and shrubs relative abundances, herb species relative abundances, environmental variables (patch architecture and size), and the spatial coordinates. Linear models were used to model the relationship of climber diversity as a function of the environmental factors. A total of 12 climber species belonging to 5 families were recorded. Associations between climber species with subordinate trees and shrubs were the major determinants of climber presence in these vegetation patches. The support for growth created by these trees and shrubs had a secondary role in explaining these patterns. We found no relationship between tree dominance and climber species dominance in each patch. However, most climbers were associated with subordinate shrubs. Trellis availability at the first stratum was related to greater climber diversity suggesting that subordinate trees and shrubs may be crucial to promote climber diversity in this plant community. Space and associations with herbs had a minor contribution to overall variation. While 15 years of research in the site associated local floristic diversity to dominant trees, our results demonstrate that climber diversity in this community is governed by interactions with subordinate host woody species related to the environmental support for growth created by such trees and shrubs.  相似文献   

10.
Gene dispersal and clonality are important aspects of plant evolution affecting the spatial genetic structure (SGS) and the long‐term survival of species. In the tropics these parameters have mostly been investigated in trees and some herbs, but rarely in climbers which frequently: (1) show clonal growth leading to a patchy distribution pattern similar to that of understory herbs; and (2) flower in the canopy where they may have access to long‐distance dispersal like canopy trees. We thus hypothesize for climbers an intermediate genetic structure between herbs and trees. The study aims at assessing breeding system and spatial extent of clonality and gene dispersal in Haumania danckelmaniana (Marantaceae), a common climber in the tropical rain forests from western Central Africa. In eastern Cameroon, 330 ramets were sampled at three spatial scales and genotyped at seven microsatellite loci. Clonality was moderate (clonal extend: 15–25 m, clonal diversity 0.4–0.65) indicating the importance of recruitment from seeds at this locality. The low inbreeding (FIS) suggested predominant outcrossing. The rate of decay of the relatedness between individuals with distance indicated limited gene dispersal distance (σ= 9–50 m, neighborhood sizes Nb = 23–67) in accordance with narrowly gravity dispersed seeds and restricted pollen transfer distance in densely flowering populations. The marked SGS (Sp = 0.011–0.026) was similar to that reported in tropical trees, but might increase with augmented clonality as in many herbs, especially under more severe disturbance regimes.  相似文献   

11.
浅谈官山自然保护区的攀缘植物资源   总被引:1,自引:0,他引:1  
在野外实地调查,标本采集,标本鉴定和文献资料整理的基础上,对官山自然保护区的攀缘植物资源进行研究.目前共有攀缘植物34科,81属,138种(包括变种).按照其用途将这些植物划分为药用、观赏、食用、纤维、化工原料、油料、香料、饲料等8种类型.  相似文献   

12.
Summary This study examines the role of canopy trees in the formation and maintenance of different herb microhabitats in a mixed mesophytic forest stand. Herb abundance and reproductive success were recorded in 54 circular plots under seven species of canopy trees and in 15 circular control plots>2 m from any tree. Soil moisture, soil nutrient levels, litter depth, and light intensity were measured in a subset of these plots. Ordination of plots by both herb relative abundance and by reproductive success of common species indicated that herb assemblages under most canopy tree species were similar to those away from trees. However, herb assemblages under Fagus grandifolia trees differed moderately from the others while plots under Quercus alba trees supported significantly different herb assemblages. Analyses of variance revealed that several herb species occurred at significantly closer mean distance to the base of Q. alba or Fagus trees or at higher densities under these tree species. Soils around Q. alba trees had significantly higher concentrations of calcium and sulfate ions, and higher pH than plots under other tree species and control plots. This correlated closely with Q. alba stemflow which had higher concentrations of calcium and sulfate ions and lower concentrations of hydrogen ions than stemflow from other trees at this site. The slightly lower soil pH near the base of Fagus trees may have been related to the high volumes of stemflow produced by this species. Stepwise regression showed significant correlations between abundances of five common herb species and soil nutrient patterns. Maintenance of spatial heterogeneity in forest floor resources by the presence of different species of canopy trees may therefore be important in the maintenance of diversity in these understory herb communities.  相似文献   

13.
Tropical mangrove forests are characterized by clear zonation along a tidal gradient, and it has been supposed that the zonation is primarily controlled by soil factors. However, effects of disturbance on mangrove forests are still not well understood and may play an important role on the vegetation patterns and forest dynamics in some forest formations. In this study, the pattern of disturbance regime and its effects on regeneration of tropical mangrove forests along a tidal gradient were investigated in Ranong, Thailand. We established one or two 0.5 ha plots in four vegetation zones, i.e. Sonneratia albaAvicennia alba zone, Rhizophora apiculata zone, Ra – Bruguiera gymnorrhiza zone, Ceriops tagalXylocarpus spp. zone. Gap size (percentage gap area to total study area and individual gap size) was the largest in Sa–Aa zone which is located on the most seaward fringe, and it declined from seaward to inland. Canopy trees of S. alba and A. alba had stunted trunks and showed low tree density. On the contrary, canopy dominants in the other three inland zones, e.g. R. apiculata, B. gymnorrhiza, and Xylocarpus spp., had slender trunks and showed high tree density. Accordingly, differences in disturbance regime among the four zones were resulted from the forest structural features of each zone. Disturbance regime matched with regeneration strategies of canopy dominants. Seedlings and saplings of S. alba and A. alba, which need sunny condition for their growth, were abundant in gaps than in understorey. By contrast, R. apiculata, B. gymnorrhiza, and Xylocarpus spp., which can tolerate less light than S. alba and A. alba, had greater seedling and sapling density under closed canopy than gaps. Many large gaps may enhance the abundance of S. alba and A. alba in Sa–Aa zone, and a few small gaps may prevent the light demanding species to establish and grow in the other inland zones. Correspondence of disturbance regime and regeneration strategies (e.g. light requirement) of canopy dominants may contribute to the maintenance of the present species composition in each of the vegetation zones.  相似文献   

14.
Comparative photosynthesis of three gap phase successional tree species   总被引:2,自引:1,他引:1  
Summary Photosynthesis was measured in situ on trees growing in an open, gap-like site and under a closed canopy. Photosynthetic responses also were monitored on trees grown in the laboratory under either a high or low light regime or on those trees transferred from a low to a high light regime. All three species studied, Liriodendron tulipifera, Acer rubrum and Cornus florida, were able to acclimate to a high light environment as evidenced by their higher photosynthetic rates. This acclimation was achieved by an increase in transfer conductance and was ultimately due to changes in leaf anatomy. Species avoided photo-bleaching primarily by changes in leaf orientation and canopy structure. Species-specific physiological responses to high light intensity may account for each species' known growth response following canopy opening.Study was partially funded by a grant in aid of research from Sigma Xi  相似文献   

15.
For trees in tropical forests, competition for light is thought to be a central process that offers opportunities for niche differentiation through light gradient partitioning. In previous studies, a canopy index based on three-dimensional canopy census data has been shown to be a good predictor of species-specific demographic rates across the entire tree community on Barro Colorado Island, Panama, and has allowed quantifying between-species variation in light response. However, almost all other forest census plots lack data on the canopy structure. Hence, this study aims at assessing whether position-based neighborhood competition indices can replace information from canopy census data and produce similar estimates of the interspecific variation of light responses. We used inventory data from the census plot at Barro Colorado Island and calculated neighborhood competition indices with varying relative effects of the size and distance of neighboring trees. Among these indices, we selected the one that was most strongly correlated with the canopy index. We then compared outcomes of hierarchical Bayesian models for species-specific recruitment and growth rates including either the canopy index or the selected neighborhood competition index as predictor. Mean posterior estimates of light response parameters were highly correlated between models (r>0.85) and indicated that most species regenerate and grow better in higher light. Both light estimation approaches consistently found that the interspecific variation of light response was larger for recruitment than for growth rates. However, the classification of species into different groups of light response, e.g. weaker than linear (decelerating) vs. stronger than linear (accelerating) differed between approaches. These results imply that while the classification into light response groups might be biased when using neighborhood competition indices, they may be useful for determining species rankings and between-species variation of light response and therefore enable large comparative studies between different forest census plots.  相似文献   

16.
In the Atlantic Montane Rain Forest of south-eastern Brazil, a field study was carried out to describe the forest disturbance regime, analyse canopy gap composition and evaluate the influence of habitat parameters on gap tree species composition. We characterized canopy gaps considering the group of variables as follows: area, type and number of tree/branch falls, topographic position, soil coverage and surrounding canopy trees. Gap composition was assessed at species level by measuring all individuals inside gaps higher than one meter. Mean gap area of the 42 canopy gaps analysed was 71.9 ± 9.0 m2 (mean ± SE). Out of the studied gaps, 35.7% were created by uprooted and by snapped trees, 16.7% by dead-standing trees and 11.9% by the fall of large branches. The disturbance regime was characterized by gap openings predominantly smaller than 150 m2 and by spatial patterning related to topography. Ridges had smaller gaps and higher proportions of gaps created by branch falls; slopes had bigger gaps generally created by uprooting events. The more abundant and frequent species were shade tolerant and the more species-rich families found inside gaps did not differ from the forest as a whole. Pioneer species were rare and restricted to medium and large size classes. The Indicator Species Analysis and the Canonical Correspondence Analysis indicated gap area, topography and the percentage of soil cover by the genera Calathea and Ctenanthe were the predominant variables correlated with woody species distribution. So, topography emerged as an important issue not only to the gap disturbance regime, but also to gap colonization. In respect to the influence of gap processes on the Atlantic Montane Rain Forest regeneration, our results support the view that canopy gap events may not be working as promoters of community wide floristic shifts.  相似文献   

17.
Habitat loss and fragmentation can negatively impact the persistence of dispersal-limited lichen species with narrow niches. Rapid change in microclimate due to canopy dieback exposes species to additional stressors that may limit their capacity to survive and colonize. We studied the importance of old trees as micro-refuges and microclimate stability in maintaining lichen survival and diversity. The study was situated in mountain Norway spruce (Picea abies) forests of the Gorgany Mountains of the Ukrainian Carpathian mountain belt. Lichens were collected on 13 circular study plots (1000 m2). Dendrochronological methods were used to reconstruct age structure and maximum disturbance event history. A linear mixed effects model and general additive models were used to explain patterns and variability of lichens based on stand age and disturbance history for each plot. Tree age was the strongest variable influencing lichen diversity and composition. Recent (<80 years ago) severely disturbed plots were colonized only by the most common species, however, old trees (>200 years old) that survived the disturbances served as microrefuges for the habitat-specialized and/or dispersal limited species, thus epiphytic lichen biodiversity was markedly higher on those plots in comparison to plots without any old trees. Most species were able to survive microclimatic change after disturbances, or recolonize disturbed patches from surrounding old-growth forests. We concluded that the survival of old trees after disturbances could maintain and/or recover large portions of epiphytic lichen biodiversity even in altered microclimates.  相似文献   

18.
Aim Species richness has been observed to increase with productivity at large spatial scales, though the strength of this relationship varies among functional groups. In forests, canopy trees shade understorey plants, and for this reason we hypothesize that species richness of canopy trees will depend on macroclimate, while species richness of shorter growth forms will additionally be affected by shading from the canopy. In this study we test for differences in species richness–productivity relationships (SRPRs) among growth forms (canopy trees, shrubs, herbaceous species) in small forest plots. Location We analysed 231 plots ranging from 34.0° to 48.3° N latitude and from 75.0° to 124.2° W longitude in the United States. Methods We analysed data collected by the USDA Forest Inventory and Analysis program for plant species richness partitioned into different growth forms, in small plots. We used actual evapotranspiration as a macroclimatic estimate of regional productivity and calculated the area of light‐blocking tissue in the immediate area surrounding plots for an estimate of the intensity of local shading. We estimated and compared SRPRs for different partitions of the species richness dataset using generalized linear models and we incorporated the possible indirect effects of shading using a structural equation model. Results Canopy tree species richness increased strongly with regional productivity, while local shading primarily explained the variation in herbaceous plant richness. Shrub species richness was related to both regional productivity and local shading. Main conclusions The relationship between total forest plant species richness and productivity at large scales belies strong effects of local interactions. Counter to the pattern for overall richness, we found that understorey herbaceous plant species richness does not respond to regional productivity gradients, and instead is strongly influenced by canopy density, while shrub species richness is under multivariate control.  相似文献   

19.
Questions: Do growth forms and vascular plant richness follow similar patterns along an altitudinal gradient? What are the driving mechanisms that structure richness patterns at the landscape scale? Location: Southwest Ethiopian highlands. Methods: Floristic and environmental data were collected from 74 plots, each covering 400 m2. The plots were distributed along altitudinal gradients. Boosted regression trees were used to derive the patterns of richness distribution along altitudinal gradients. Results: Total vascular plant richness did not show any strong response to altitude. Contrasting patterns of richness were observed for several growth forms. Woody, graminoid and climber species richness showed a unimodal structure. However, each of these morphological groups had a peak of richness at different altitudes: graminoid species attained maximum importance at a lower elevations, followed by climbers and finally woody species at higher elevations. Fern species richness increased monotonically towards higher altitudes, but herbaceous richness had a dented structure at mid‐altitudes. Soil sand fraction, silt, slope and organic matter were found to contribute a considerable amount of the predicted variance of richness for total vascular plants and growth forms. Main Conclusions: Hump‐shaped species richness patterns were observed for several growth forms. A mid‐altitudinal richness peak was the result of a combination of climate‐related water–energy dynamics, species–area relationships and local environmental factors, which have direct effects on plant physiological performance. However, altitude represents the composite gradient of several environmental variables that were interrelated. Thus, considering multiple gradients would provide a better picture of richness and the potential mechanisms responsible for the distribution of biodiversity in high‐mountain regions of the tropics.  相似文献   

20.
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