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1.
Sonali Saha 《Ecography》2003,26(1):80-86
The regressive succession model hypothesizes tropical savanna-woodlands to be a degraded stage of primary deciduous forests. Species diversity, richness and evenness of woody species in savanna-woodlands, secondary deciduous forests and mature deciduous forests of central India were compared to test if the regressive succession explained pattern in species richness, diversity, functional diversity and basal area. At the plot scale (0.1 ha) secondary deciduous forests and savanna-woodlands had similar species diversity, a pattern not consistent with the regressive model of deciduous forest succession, and mature deciduous forests had greater species diversity and richness (p<0.05). When examined at a larger scale or community scale by pooling all plots within a community type, the trend in diversity persisted even with greater effort allocated to sampling of secondary deciduous forests. Species richness at the community scale was greatest in secondary deciduous forest as expected from species area relationship. The communities shared 28 woody species but the species composition was significantly different between the communities. I suggest that conservation of tropical deciduous forests based on regressive succession model is problematic.  相似文献   

2.
In this paper we tested the hypothesis that logging effects in the adult tree community reverberate upon the regeneration contingent. We examined the differences on the tree community between forest reserves and 10 year-old logged areas in the Yucatan Peninsula. We used a paired design in three independent sites to estimate the effects of logging on tree species richness, diversity, composition and structure. Analyses were conducted differentiating individuals of four diameter-size classes: 1–5, 5–10, 10–25, and >25 cm DBH. We found out that there were differential effects by size. Species richness in the smaller and larger diameter-size classes was significantly lower in logged areas. Floristic composition was also different between logged and unlogged areas, with a trend towards more secondary forest associated species and less primary forest associated species in logged areas, and a higher density of species represented by a single individual in unlogged reserves. In terms of structure, trees DBH <10 cm, lianas, and re-sprouting stumps were more abundant in logged areas. Our findings suggest that 10 years after logging, harvested areas show alterations in structure, and potentially a reduction in species richness. We suggest that to make timber extraction and forest conservation compatible at this site, it is necessary to gain a better understanding of the ecology and regeneration requirements of the less abundant species, and to assess whether current logging practices might hinder their permanence in the study area.  相似文献   

3.
Making generalizations about the impact of commercial selective logging on biodiversity has so far remained elusive. Species responses to logging depend on a number of factors, many of which have not been studied in detail. These factors may include the natural forest conditions (forest types) under which logging impacts are investigated; but this question has so far remained unexamined. In a large‐scale replicate study we aimed at clarifying the relationship between logging and forest types on leaf litter frogs. We contrast three distinct and naturally occurring forest types, including wet evergreen, moist evergreen and semi‐deciduous forests. Selectively logged sites were compared with primary forest sites for each forest type. We found that the response of frog communities to logging varies in different forest types. In the wet evergreen forest, richness was higher in logged forest than primary forest, while diversity measures were not different between logged and primary forest habitats. In the moist evergreen, richness and diversity were higher in selectively logged areas compared with primary forest habitats. In the semi‐deciduous, logged forests were characterized by drastic loss of forest specialists, reduced richness, and diversity. These results indicate that the net effect of logging varies with respect to forest type. Forest types that are characterized by adverse climatic conditions (i.e., low rainfall and protracted dry seasons) are more likely to produce negative effects on leaf litter anuran communities. For comparisons of the impact of logging on species to be effective, future research must endeavor to include details of forest type.  相似文献   

4.
Predicting the recovery processes in tree communities after logging is critical when developing conservation strategies. We assessed the patterns in tree communities in logged and primary forests in Kibale National Park, Uganda, representing 9‐ to 19‐year‐old clear‐cuts of former conifer plantations, 42‐ to 43‐year‐old logged forests and primary forests. Species density and diversity were lower and dominance higher in the 9‐ to 19‐year‐old forests compared to the 42‐ to 43‐year‐old forests or primary forests. The tree species density, diversity and dominance of 42‐ to 43‐year‐old forests did not differ significantly from primary forests. However, they had a lower stem density, and higher cover of Acanthus pubescens, a shrub known to arrest the succession in Kibale. The tree community compositions of 9‐ to 19‐year‐old, 42‐ to 43‐year‐old and primary forests differed from each other. A large group of tree species (21) were primary forest indicators, that is, they were either missing or relatively rare in logged forests. The results of this study show that even after four decades of natural recovery, logged Afrotropical forests can still be distinguished from primary forests in their tree community compositions, emphasizing the slow community recovery and the important role of primary forests when preserving the tree communities in tropical rainforests.  相似文献   

5.
Selective logging is one of the major drivers of tropical forest degradation, causing important shifts in species composition. Whether such changes modify interactions between species and the networks in which they are embedded remain fundamental questions to assess the ‘health’ and ecosystem functionality of logged forests. We focus on interactions between lianas and their tree hosts within primary and selectively logged forests in the biodiversity hotspot of Malaysian Borneo. We found that lianas were more abundant, had higher species richness, and different species compositions in logged than in primary forests. Logged forests showed heavier liana loads disparately affecting slow-growing tree species, which could exacerbate the loss of timber value and carbon storage already associated with logging. Moreover, simulation scenarios of host tree local species loss indicated that logging might decrease the robustness of liana–tree interaction networks if heavily infested trees (i.e. the most connected ones) were more likely to disappear. This effect is partially mitigated in the short term by the colonization of host trees by a greater diversity of liana species within logged forests, yet this might not compensate for the loss of preferred tree hosts in the long term. As a consequence, species interaction networks may show a lagged response to disturbance, which may trigger sudden collapses in species richness and ecosystem function in response to additional disturbances, representing a new type of ‘extinction debt’.  相似文献   

6.
K. S. Seshadri 《Biotropica》2014,46(5):615-623
Vast areas of tropical evergreen forests have been selectively logged in the past, and many areas continue to be logged. The impacts of such logging on amphibians are poorly understood. I examined the response of anuran communities to historical selective logging in a wet evergreen forest in south India. Anuran assemblages in unlogged forest were compared with assemblages in selectively logged forest. Forty 10 m × 10 m quadrats in forest, riparian zones, and streams of unlogged and selectively logged forests were searched at night for anurans. Species richness did not appear to be affected by logging. However, anuran density varied significantly and was 42 percent lower in selectively logged forests compared to unlogged forests. Anuran densities also varied significantly across microhabitats, with highest densities in streams of both selectively logged and unlogged forests. Patterns of niche overlap varied with selective logging as niche breadth either expanded, contracted, or remained neutral for different species. Ordination analysis explained 95 percent of the variation in species assemblage across selectively logged and unlogged forests. The assemblage in selectively logged forest was nested within unlogged forest. Among the habitat characteristics, litter thickness and water depth had the highest influence on the assemblage. This was followed by litter/water temperature, air temperature, and lastly relative humidity. It appears that species richness and composition of anurans in selectively logged forests is converging with unlogged forests, but the effects of historical logging seem to persist on anuran densities and their niche characteristics even ca 40 yr since logging ceased.  相似文献   

7.
Processes of forest regeneration in two unlogged areas and in three areas that were logged nearly 25 years ago were quantified in Kibale National Park, Uganda. For forests to recover from logging, one would predict recruitment and growth processes to be accelerated in logged areas relative to unlogged areas, facilitating increased recruitment of trees into the adult size classes. We examined this prediction first by determining the growth of 4733 trees over a 51 to 56 month period and found that growth rates in the most heavily logged area were consistently slower than in the two unlogged areas. In contrast, the lightly logged forest had similar growth rates to unlogged areas in the small size classes, but trees in the 30 to 50 cm DBH size cohort exhibited elevated growth rates relative to the unlogged areas. Mortality was highest in the heavily logged areas, with many deaths occurring when healthy trees were knocked over by neighboring treefalls. We found no difference in the density or species richness of seedlings in the logged and unlogged forests. The number of seedlings that emerged from the disturbed soil (seed bank+seed rain) and initially seed-free soil (seed rain) was greater in the logged forest than in the unlogged forest. However, sapling density was lower in the heavily logged areas, suggesting that there is a high level of seedling mortality in logged areas. We suggest that the level of canopy opening created during logging, the lack of aggressive colonizing tree species, elephant activity that is concentrated in logged areas, and an aggressive herb community, all combine to delay vegetation recovery in Kibale Forest.  相似文献   

8.
The carbon storage and conservation value of old-growth tropical forests is clear, but the value of logged forest is less certain. Here we analyse >100,000 observations of individuals from 11 taxonomic groups and >2,500 species, covering up to 19?years of post-logging regeneration, and quantify the impacts of logging on carbon storage and biodiversity within lowland dipterocarp forests of Sabah, Borneo. We estimate that forests lost ca. 53% of above-ground biomass as a result of logging but despite this high level of degradation, logged forest retained considerable conservation value: floral species richness was higher in logged forest than in primary forest and whilst faunal species richness was typically lower in logged forest, in most cases the difference between habitats was no greater than ca. 10%. Moreover, in most studies >90% of species recorded in primary forest were also present in logged forest, including species of conservation concern. During recovery, logged forest accumulated carbon at five times the rate of natural forest (1.4 and 0.28?Mg?C?ha?1?year?1, respectively). We conclude that allowing the continued regeneration of extensive areas of Borneo??s forest that have already been logged, and are at risk of conversion to other land uses, would provide a significant carbon store that is likely to increase over time. Protecting intact forest is critical for biodiversity conservation and climate change mitigation, but the contribution of logged forest to these twin goals should not be overlooked.  相似文献   

9.
Abstract:  The impact of logging on the relative abundance, species richness and community composition of four butterfly guilds (generalists, herb specialists, liana specialists and tree specialists) was assessed in differentially disturbed logging treatments located within the province of Central Kalimantan, Indonesian Borneo. Logging affected the overall butterfly composition by increasing the dominance of liana specialists at the expense of tree specialists and increasing the species richness of herb specialists and, to a lesser extent, generalists. There was no significant difference, however, in the species richness of liana specialists or tree specialists across logging treatments. The species composition of all guilds differed significantly among logging treatments with the greatest difference between unlogged forest and road sites with older and recently logged forest intermediate between these extremes. Our results indicate that logging has a disparate effect on abundance and species richness within each butterfly guild. We suggest that shifts in the dominance of butterfly guilds are due to large-scale logging-induced changes in vegetation, particularly in relation to liana abundance. The higher butterfly species richness in logged areas on the other hand is probably because of butterfly species associated with open areas entering the logged forest from roads or other large open areas.  相似文献   

10.
Tropical rainforests are subject to extensive degradation by commercial selective logging. Despite pervasive changes to forest structure, selectively logged forests represent vital refugia for global biodiversity. The ability of these forests to buffer temperature‐sensitive species from climate warming will be an important determinant of their future conservation value, although this topic remains largely unexplored. Thermal buffering potential is broadly determined by: (i) the difference between the “macroclimate” (climate at a local scale, m to ha) and the “microclimate” (climate at a fine‐scale, mm to m, that is distinct from the macroclimate); (ii) thermal stability of microclimates (e.g. variation in daily temperatures); and (iii) the availability of microclimates to organisms. We compared these metrics in undisturbed primary forest and intensively logged forest on Borneo, using thermal images to capture cool microclimates on the surface of the forest floor, and information from dataloggers placed inside deadwood, tree holes and leaf litter. Although major differences in forest structure remained 9–12 years after repeated selective logging, we found that logging activity had very little effect on thermal buffering, in terms of macroclimate and microclimate temperatures, and the overall availability of microclimates. For 1°C warming in the macroclimate, temperature inside deadwood, tree holes and leaf litter warmed slightly more in primary forest than in logged forest, but the effect amounted to <0.1°C difference between forest types. We therefore conclude that selectively logged forests are similar to primary forests in their potential for thermal buffering, and subsequent ability to retain temperature‐sensitive species under climate change. Selectively logged forests can play a crucial role in the long‐term maintenance of global biodiversity.  相似文献   

11.
Cleary DF 《Oecologia》2003,135(2):313-321
The impact of disturbance on species diversity may be related to the spatial scales over which it occurs. Here I assess the impact of logging and ENSO (El Niño Southern Oscillation) -induced burning and forest isolation on the species richness (477 species out of more than 28,000 individuals) and community composition of butterflies and butterfly guilds using small (0.9 ha) plots nested within large (450 ha) landscapes. The landscapes were located in three habitat classes: (1) continuous, unburned forest; (2) unburned isolates surrounded by burned forest; and (3) burned forest. Plots with different logging histories were sampled within the two unburned habitat classes, allowing for independent assessment of the two disturbance factors (logging and burning). Disturbance within habitat classes (logging) had a very different impact on butterfly diversity than disturbance among habitat classes (due to ENSO-induced burning and isolation). Logging increased species richness, increased evenness, and lowered dominance. Among guilds based on larval food plants, the species richness of tree and herb specialists was higher in logged areas but their abundance was lower. Both generalist species richness and abundance was higher in logged areas. Among habitat classes, species richness was lower in burned forest and isolates than continuous forest but there was no overall difference in evenness or dominance. Among guilds, generalist species richness was significantly lower in burned forest and isolates than continuous forest. Generalist abundance was also very low in the isolates. There was no difference among disturbance classes in herb specialist species richness but abundance was significantly higher in the isolates and burned forest than in continuous forest. Tree specialist species richness was lower in burned forest than continuous forest but did not differ between continuous forest and isolates.The scale of assessment proved important in estimating the impact of disturbance on species richness. Within disturbance classes, the difference in species richness between primary and logged forest was more pronounced at the smaller spatial scale. Among disturbance classes, the difference in species richness between continuous forest and isolates or burned forest was more pronounced at the larger spatial scale. The lower levels of species richness in ENSO-affected areas and at the larger (landscape) spatial scale indicate that future severe ENSO events may prove one of the most serious threats to extant biodiversity.  相似文献   

12.
Tropical forests across the world provide important habitats for a diverse number of conservation priority species, yet are under threat from a range of anthropogenic impacts including logging. This study aims to quantify mammalian biodiversity in unlogged and logged forests in the adjoining Tembat and Petuang Forest Reserves, Terengganu, on the East Coast of Peninsular Malaysia. Data was collected over a series of surveys using direct and indirect observation methods from 2008 to 2014. A total of 30 medium and large sized mammals species were identified, with 27 of those species found in unlogged forests and 22 species in logged forests. Carnivores encompassed 11 species from 67 observations representing 15% of the total number of observations. The family Felidae had the highest number of species (six species), followed by Hylobatidae, Cercopithecidae and Suidae with three species each. A total of 17 species contributed to more than 90% of the mammal community in the unlogged and logged forests, while six species were uncommon and only observed once during the entire survey. Species abundance in the unlogged forest was significantly greater than the logged forests, but the difference was not significant for species richness. This study provides critical baseline information on the impact of unlogged and logged forests and the identification of threatened species warrant the establishment of conservation measures such as anti-poaching patrol and ranger stations in the study area.  相似文献   

13.
We compared bird diversity and frequency in selection logged and unlogged forest to determine the effects of recent selection logging on avian biodiversity in a subtropical, moist evergreen forest. We used a combination of mist netting and fixed-radius point counts to assess bird communities in February and March 1993 in northwestern Belize. Vegetation structure and composition was similar in logged and unlogged forest. The 66 most common species occurred with statistically similar frequency in logged and unlogged forest although 13 species were two times more frequent in intact forest. Numbers of total bird species were similar between logging gaps and the logged forest matrix, and between the logged forest matrix and unlogged forests. A comparison of numbers of species in 26 guilds based on migration strategy, diet, foraging substrate, and height strata also showed them to be similar regardless of logging history. Our results differed from previous studies that reported lower bird species richness and abundance of individual species in logged tropical forests than in unlogged forest. The differences might be explained by the lower logging intensity and/or greater levels of natural disturbance in our study area compared to previous studies.  相似文献   

14.
We analyze forest structure, diversity, and dominance in three large-scale Amazonian forest dynamics plots located in Northwestern (Yasuni and Amacayacu) and central (Manaus) Amazonia, to evaluate their consistency with prevailing wisdom regarding geographic variation and the shape of species abundance distributions, and to assess the robustness of among-site patterns to plot area, minimum tree size, and treatment of morphospecies. We utilized data for 441,088 trees (DBH ≥1 cm) in three 25-ha forest dynamics plots. Manaus had significantly higher biomass and mean wood density than Yasuni and Amacayacu. At the 1-ha scale, species richness averaged 649 for trees ≥1 cm DBH, and was lower in Amacayacu than in Manaus or Yasuni; however, at the 25-ha scale the rankings shifted, with Yasuni < Amacayacu < Manaus. Within each site, Fisher’s alpha initially increased with plot area to 1–10 ha, and then showed divergent patterns at larger areas depending on the site and minimum size. Abundance distributions were better fit by lognormal than by logseries distributions. Results were robust to the treatment of morphospecies. Overall, regional patterns in Amazonian tree species diversity vary with the spatial scale of analysis and the minimum tree size. The minimum area to capture local diversity is 2 ha for trees ≥1 cm DBH, or 10 ha for trees ≥10 cm DBH. The underlying species abundance distribution for Amazonian tree communities is lognormal, consistent with the idea that the rarest species have not yet been sampled. Enhanced sampling intensity is needed to fill the still large voids we have in plant diversity in Amazon forests.  相似文献   

15.
Abstract. The effects of selective logging on tree diversity, changes in tree species composition and plant functional types were studied with the use of seven permanent plots in virgin and in logged forest. All plots were located in a lowland dipterocarp rain forest in East Kalimantan on the island of Borneo. Just after logging and during the following 20 yr tree diversity measured as Fishers’α was not significantly affected in logged forest plots. Temporal shifts in tree species composition were analysed with Principal Component Analysis (PCA). Logged forest plots had much larger changes over time than virgin forest plots. In the smallest diameter class, some logged forest plots showed a distinct trajectory in PCA space compared to virgin forest plots, while in larger diameter classes movement of logged plots in PCA space was random. This suggests that there is no predetermined community to which logged forest plots tend to shift when recovering from logging. We found a significant negative correlation between diameter increments and the species‐specific wood densities of tree species. Species‐specific wood density and potential tree height were used to assign species to five PFTs. As expected, logging increased the fraction of softwood stems in small diameter classes. In the largest diameter classes (≥ 50 cm DBH) a strong decrease of softwood emergent stems was found in logged forest plots. After more than 20 yr no recruitment was found of softwood emergent stems in selectively logged forest.  相似文献   

16.
Species richness and abundance are the two most important diversity variables. Species abundance is additive when aggregated across spatial scale, whereas species richness is non-additive. This study analyzes the effect of spatial scale and site on species abundance and richness in a 25-ha temperate forest plot in the Changbai Mountains, northeastern China. The result shows that species abundance and richness are not only dependent on spatial scales, but also dependent on site. Species abundance responds linearly to changes of spatial scale with no intersection in different sites of the study area. However, although species richness also increases with the increase of spatial scale, there are some intersections for the different sites, suggesting that a species-rich site does not always have a high value if the spatial scale is changed. In all, with respect to additive variables, it is relatively easy to extrapolate them from one spatial scale to another spatial scale, as they and the spatial scale usually form a linear relationship. In contrast, non-additive variables are difficult to extrapolate across spatial scales, because they often respond nonlinearly to spatial scale changes. In order to extrapolate these non-additive variables across spatial scales, it is necessary to estimate the relationships between them and spatial scales. As a result, extrapolation of information among spatial scales may be possible, but very difficult, especially for non-additive variables. Because the 25-ha Changbai plot is very small compared to the extent of the world temperate forests, and the vegetation is a relatively uniform type, more such studies in other ecosystems are needed before theories and generalization about scaling effects can be formulated.  相似文献   

17.
Aim The effects of logging and habitat degradation on the richness and abundance of small mammals in Asian rain forests are largely unknown. This work compares the species richness, dominance and evenness of small non‐volant mammals between logged and unlogged forests, and assesses whether assemblage variability (β‐diversity) is similar between forest types. Location Southeast Asia, northern Borneo (Sabah, Malaysia), Sunda‐shelf. Methods We surveyed species‐rich assemblages of small non‐volant mammals in three unlogged and three logged forests for 2 years. At each forest site, we sampled a permanently marked transect and two additional sites in three trapping sessions. All analyses were performed at both levels to include the effects of local abundances and point estimates, separately from the relative abundances of species on a more regional scale. Results We trapped a total of 1218 individuals of 28 species. Eleven common species accounted for 95% of all captures. Species richness and diversity were significantly higher in unlogged forest (27 species) than in logged forest (17 species). This was mainly attributable to the smaller number of rarely recorded species in logged forest (five compared with 16 in unlogged forest, with a total of fewer than 10 captures). However, all common species were present in both logged and unlogged forests, and our analyses revealed similar patterns of dominance, evenness and fluctuations in abundance. Hence overall assemblage composition in multivariate space did not differ greatly between forest types. Assemblages of Muridae and Tupaiidae showed similar population fluctuations in space and time, indicating that the ecology of these taxa may be partially driven by the same environmental factors. Main conclusions Although species were distributed patchily within sites, analyses at local and regional scales revealed similar patterns in diversity and assemblage variability, suggesting that effects of forest modification did not differ extensively locally and regionally, but had a profound effect on rare species. Our results emphasize the importance and conservation value of logged forest stands that are able to hold a large proportion of the small mammals also found in unlogged forests. Rare and more specialized species are more vulnerable to forest degradation than commonly caught species, resulting in the complete loss, or a decrease in numbers, of certain groups, such as arboreal small mammals and Viverridae.  相似文献   

18.
Vascular epiphytes represent a highly diverse element of tropical rain forests, but they depend strongly on the structure and taxonomic composition of their tree communities. For conservation planning, it is therefore critical to understand the effect of host tree characteristics on epiphyte species richness in natural and anthropogenically transformed vegetation. Our study compares the effect of human land‐use on epiphyte diversity based on 220 study plots in a lowland rain forest and an Andean cloud forest in western Ecuador. We evaluate the relevance of host tree size and taxonomic identity for epiphyte species richness in contiguous primary forests, forest fragments, isolated remnant trees (IRTs), and secondary forests. At both study sites, epiphyte diversity was highest in primary forests, and it was lowest on IRTs and in secondary forests. Epiphyte species numbers of forest fragments were significantly reduced compared with the contiguous primary forest at the lowland study site, but not in the cloud forest area. Host tree size was a core predictor among secondary forests, but it had less significance within other habitat types. Taxonomic identity of the host trees also explained up to 61 percent of the variation in epiphyte diversity, especially for IRTs. The structural and taxonomic composition of the tree community in anthropogenically transformed habitat types proved to be fundamental to epiphyte diversity. This highlights the importance of deliberate selection of tree species for reforestation in conservation programs and the possible negative effects of selective logging in primary forests. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .  相似文献   

19.
We examined the effect of selective logging and corresponding forest canopy loss on arboreal ant diversity in a tropical rainforest. Arboreal ants were collected from an unlogged forest plot and from forest plots selectively logged 14 years and 24 years earlier in Danum Valley, Sabah, Malaysia, using a canopy fogging method. Selective logging was associated with a significant decrease in canopy cover and an increase in understory vegetation density relative to unlogged forest. Our study showed that selective logging in primary forest might not dramatically decrease total species number and overall abundance of arboreal ants; however, it may influence the species composition and dominance structure of the ant community, accompanied by an increase in abundance of shrub‐layer species and trophobiotic species. In view of the results of this study, management techniques that minimize logging impact on understory vegetation structure are likely to help maintain the conservation value of logged forests for arboreal ants. Our results also suggest that accurate assessment of the impacts on biodiversity should not be based only on measurement of species number and overall abundance, but also on analysis of species composition and community structure.  相似文献   

20.
The avifauna 23 years after logging in Kibale National park, Uganda   总被引:4,自引:2,他引:2  
The bird fauna of logged and unlogged forest in Kibale National Park, western Uganda were studied and comparisons made. Species diversity and richness were higher in the logged areas. A single species, the Yellow-whiskered Greenbul Andropadus latirostris dominated in the logged compartment. However, the majority of individual birds found in the logged forest were generalist or forest-edge species. Over 84% of the forest interior specialist species that occurred in primary forest had recolonized or persisted in the logged forest; however, there were seven out of 48 understorey forest specialists that had not done so. Although there was moderate species overlap between the two habitats, the logged forest compartment had not fully recovered from logging after 23 years.  相似文献   

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