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1.
Forest and land fires are a recurrent phenomena in Indonesia and little progress has been made in reducing their occurrence. The mineral and peat fire in 2015 burnt 2.6 million hectares, mostly in the provinces of Riau, South Sumatra, Jambi, Central Kalimantan, West Kalimantan and Papua, and costed USD16.1 billion as estimated by the World Bank in 2015. Although only 30% of the fire was on peatland area, it had a much higher impact than that on mineral land because of its fire density. Fires in Indonesia are caused by human both individually or collectively. Indonesian President Joko Widodo has committed to reducing fire during his term of office. Government actions have focused on fire suppression, biophysical and technological issues such as canal blocking and an early warning system. Significant actions on the underlying causes of fires such as providing economy incentives for land preparation without burning are rare. We conducted a political economy study of fire and haze to provide policy makers with an understanding of the economic, social and political causes of forest and land fires. The study focused on four districts in Riau Province, which experienced fires and forest transition to palm oil plantations. We collected social, policy and economy data from survey in ex post fire sites and carried out focus group discussions with the key stakeholders. We implemented value chain and social network analyses to the collected data. We found a diversity of actors were involved and gaining benefits from fires. We found that farmer group organizers obtained enormous benefits, as much as USD486 per hectare. These actors influence decision-making processes through their patronage network for their own interests. The networks provide power, support, protection and access to various resources. To effectively reduce fire, governments need to disempower these farmer group organizers through law and policy.  相似文献   

2.
The sampling method is described which is used for the sampling of plant species richness and cover in a monitoring project on forest ecosystems in Tuscany (named MONITO). Species richness is sampled through a nested plot design, with plot size ranging from 1 to 2500 m2, whereas species abundance is estimated in 100 m2 plots. This sampling design is simple to install and to manage through time. Species diversity can be monitored not just at one single spatial scale but at many scales, and species–area relations can also be calculated. The analyses of the data that were collected produced the first available data on species richness in relation to plot size for Tuscan forest ecosystems, indeed for any Italian forests. The Arrhenius Power function and the General Root models showed the best fit. Turkey oak (Quercus cerris) woods located on slightly acidic soil were found to be the forest ecosystems with the highest species richness, confirming and quantifying well-established floristic-phytosociological knowledge. Habitat heterogeneity, measured by plot floristic resemblance, showed how the Turkey oak woods were the most heterogeneous at the smaller spatial scales, but not at larger ones.  相似文献   

3.
The frequency and intensity of salvage logging has recently increased in burned forests of the Canadian boreal so that post-fire areas make up a significant annual share of all harvested forest land in some years. However, little is known about how this practice affects re-establishment of animal and plant communities that already have been strongly altered by the fire. We pitfall-trapped carabid beetles (Coleoptera, Carabidae) for two consecutive years following a large-scale boreal wildfire (276,000 ha) in burned mixed-wood forests of 12 landscape units (2.5 km × 2.5 km each). These units included four salvage treatments, each replicated three times: control (no salvaging), low (ca. 20–30% of merchantable mixed-wood removed), moderate (40–50%) and high salvage intensity (60–70%). We established 16 sampling sites in each unit: on the control landscapes, all 16 sites were in un-logged stands; in low-salvage units, 4 out of 16 sites were in salvaged areas; in moderate- and high-salvage units, 8 and 12 out of 16 sites, respectively, were in salvaged areas. Salvage logging positively affected carabid species richness. However, there was an overall salvage-caused decrease in the abundance of many common forest-dwelling carabids, and an increase in the abundance of disturbance or open-habitat specialists. Interestingly, the effects of salvage logging on the total catch and several abundant forest species (e.g., Calosoma frigidum, Harpalus laevipes, Pterostichus punctatissimus, P. adstrictus and Platynus decentis) appeared to be more important at the landscape level (the four landscape treatments) than at the level of sampling sites (site logged versus not). We suggest that this observation resulted from ambiguous site-level responses to salvage that collectively contributed to the (mostly negative) significant responses at the landscape level. Effects of fire severity (estimates based on tree survival) on carabids were species-specific; however, the impact of this measure was most often significant at the site, and not at the landscape, level. A Multivariate Regression Tree revealed that fire severity and the overall (pre-fire) amount of mixed-wood forest on the landscape were significant determinants of assemblage structure, with the local effects of fire severity being strongest.  相似文献   

4.
Turvo Park in the Alto Uruguay River region of the State of Rio Grande do Sul is the last intact remnant of the Seasonally Deciduous Forest in southern Brazil. This forest once covered large parts of southern Brazil but it is now reduced to less than 3% of its original size due to intensive logging caused by its exceptional richness in tree species with commercial timber value. The current study presents results on the diversity of timber species inventored in Turvo Park and in a number of small and scattered forest remnants in its vicinity. All timber plants with DBH ≥5 cm were included in the forest inventory on 540 sampling points, established using the point-centred quarter method. On average, 313 plants ha−1 were recorded, belonging to 57 different species from 25 families. Timber species of commercial value represented 64% of all woody species and 36% of all woody plants. Nectandra megapotamica and Apuleia leiocarpa were the main dominant species. Twenty percent of all plants showed a DBH greater than 40 cm, representing 67% of the total log volume. Differences in species diversity and plant density among the forest remnants were detected. The few forest remnants represent an enormous richness of timber species, being the maintainers and propagule repository for all the biodiversity of that ecosystem. A knowledge-based forest management plan is therefore required to secure their vital role in forest enrichment programs or in projects aiming at recovering abandoned and degraded areas, and in breeding programs for the timber production improvement.  相似文献   

5.
We studied how variations in fire severity and the degree of cutting before burning affected soil invertebrates in a Pinus sylvestris forest in central Sweden. A varied depth of burn in the mor layer was obtained by exclusion of rain and addition of fuel in small plots (1 m×2 m) in clear-cut, selectively cut and uncut part of the forest before large-scale prescribed burning took place. Soil samples were taken from the plots immediately before, the day after, and two months after the fire. The overall mortality of invertebrates depended on the proportion of organic soil consumed by the fire, and for individual taxa it ranged between 59 and 100%. Invertebrates that lived deeper in soil suffered lesser mortality than those in the vegetation and litter layers did. Greater mobility in soil (Staphylinidae) or a thick cuticle (Oribatediae, Elateridae) may have contributed to the higher survival observed in these taxa. The beetles Atomaria pulchra (Cryptophagidae), Corticaria rubripes (Lathridiidae), and other fire-favoured insects colonised the burned forest the very day the fire burned. These species preferred the hard-burned plots and the uncut stand for colonisation. Sixty days after the fire, the abundance of invertebrates was lower in the burned cut stands compared to the burned uncut stand. The species composition of beetles in the burned stands was then characterised by a few very abundant fire-favoured species.  相似文献   

6.
Species accumulation curves were used to study relationships between herpetofaunal richness and habitat characteristics on four watersheds in Arkansas that differed markedly with respect to management intensity. Selected habitat characteristics were estimated for stands containing the sample points and within buffers with radii of 250, 500 m, and 1 km surrounding the sample points. Richness of all three herpetofaunal groups (amphibians, reptiles, and all herpetofauna) was greater in hardwood forests than in pine or mixed pine–hardwood. For all three groups, the youngest forest age class had the most species. For amphibians and total herpetofauna, richness declined as stand ages increased. Reptiles had the highest richness at sample points with the lowest class of stand basal area (BA), whereas amphibians were richest at points having the highest BA. In contrast to expectations, there was no effect of distance from water on richness of any taxa; however, we may have had incomplete data on the spatial distribution of small ponds outside the sample plots because they were not recorded in the GIS data. Results for distance to roads were ambiguous, but with more separation of compared curves as more plots were sampled, a positive influence of road proximity was suggested. There was a positive effect of buffer age diversity at the 250 m scale for all three herpetofaunal groups, but less so at scales >250 m except for amphibians, which also showed a positive effect at the 1 km scale. The two most intensively managed watersheds had higher species richness than the two less intensively managed watersheds for reptiles, amphibians, and both groups combined. In this study landscape, where urban and agricultural influences were minimal, we did not observe negative impacts of forest management and associated activities, and local habitat heterogeneity created by silviculture often had a positive effect on herpetofaunal species richness.  相似文献   

7.
From 1989 to 2003, a widespread outbreak of spruce beetles (Dendroctonus rufipennis) in the Copper River Basin, Alaska, infested over 275,000 ha of forests in the region. During 1997 and 1998, we measured forest vegetation structure and composition on one hundred and thirty-six 20-m × 20-m plots to assess both the immediate stand and landscape level effects of the spruce beetle infestation. A photo-interpreted vegetation and infestation map was produced using color-infrared aerial photography at a scale of 1:40,000. We used linear regression to quantify the effects of the outbreak on forest structure and composition. White spruce (Picea glauca) canopy cover and basal area of medium-to-large trees [≥15 cm diameter-at-breast height (1.3 m, dbh)] were reduced linearly as the number of trees attacked by spruce beetles increased. Black spruce (Picea mariana) and small diameter white spruce (<15 cm dbh) were infrequently attacked and killed by spruce beetles. This selective attack of mature white spruce reduced structural complexity of stands to earlier stages of succession and caused mixed tree species stands to lose their white spruce and become more homogeneous in overstory composition. Using the resulting regressions, we developed a transition matrix to describe changes in vegetation types under varying levels of spruce beetle infestations, and applied the model to the vegetation map. Prior to the outbreak, our study area was composed primarily of stands of mixed white and black spruce (29% of area) and pure white spruce (25%). However, the selective attack on white spruce caused many of these stands to transition to black spruce dominated stands (73% increase in area) or shrublands (26% increase in area). The post-infestation landscape was thereby composed of more even distributions of shrubland and white, black, and mixed spruce communities (17–22% of study area). Changes in the cover and composition of understory vegetation were less evident in this study. However, stands with the highest mortality due to spruce beetles had the lowest densities of white spruce seedlings suggesting a longer forest regeneration time without an increase in seedling germination, growth, or survival.  相似文献   

8.
In three different plant communities growing in Mediterranean old fields we studied the short-term changes in soil nitrogen availability that occur after the fire. Two of these communities were grasslands with great capacity of resprouting and contrasted N availability, one dominated by Brachypodium retusum, and the second one dominated by B. retusum and the N fixing shrub Genista scorpius. The third community was an obligate seeder community (shrubland) with low N availability and was dominated by Rosmarinus officinalis. We selected six plots for each type of vegetation and therefore performed 18 experimental fires. During fires we measured temperatures at the soil surface. Maximum temperature recorded during fire and time–temperature integral were used as indexes of fire severity. During the 6 months following fires we measured Net N mineralization and plant uptake by field incubations using the resin-core technique in paired burnt and control plots.Fire severity increased with plant biomass. In grasslands heating of the soil surface increased with plant biomass up to a limit of 1 kg m−2 of above-ground biomass. For high biomass a large proportion of heat released during fire was probably transmitted to the atmosphere or to the deeper soil horizons. The increase of soil mineral N was larger in fires of greater severity. Most mineral nitrogen released to the soil during fire was ammonia. Increases of ammonia post-fire depends on the temperatures measured on the soil surface while increases of the less volatile N form (nitrate) were related to the amount of burnt biomass and were highly dependent on the type of vegetation.The amount of nitrogen released to soil during fire represented a small proportion of the N mineralized during the 6 months following fire and thus the amount of nitrogen mineralized per unit of N released during fire was very different across the different types of vegetation. In grasslands fire induced changes in N mineralization decreased as fire severity increased. In contrast, in shrublands we observed the opposite trend. Differences in potentially mineralizable and in net mineralization N between unburnt grasslands and shrublands could account for this fact. Despite the depression in nitrification that we observed in grasslands between 40 and 80 days after the fire, high nitrate concentration in the soil during that period increased N leaching in burnt plots. No plant uptake was detected at that time. In grasslands the onset of plant uptake in burnt plots was delayed as compared to control. Cumulative changes in N did not depend on the burnt biomass in grassland communities, but it did in the seeder community. On the contrary, soil temperatures measured during fires related to changes in N observed in grasslands but not in the seeder community. It appears therefore, that post-fire N mineralization and leaching in grasslands may have been driven by the changes induced by heating the soil surface while in shrublands it may have been driven by the quantity of ash deposited on the soil surface.  相似文献   

9.
We implemented a fire risk assessment framework that combines spatially-explicit burn probabilities, post-fire mortality models and public auction timber prices, to estimate expected economic losses from wildfires in 155 black pine stands covering about 450 ha in the Juslapeña Valley of central Navarra, northern Spain. A logit fire occurrence model was generated from observed historic fires to provide required fire ignition input data. Wildfire likelihood and intensity were estimated by modeling 50,000 fires with the minimum travel time algorithm (MTT) at 30 m resolution under 97th percentile fire weather conditions. Post-fire tree mortality due to burning fire intensity at different successional stages ranged from 0.67% in the latest stages to 9.22% in the earliest. Stands showed a wide range of potential economic losses, and intermediate successional stage stands presented the highest values, with about 124 € ha− 1 on average. A fire risk map of the target areas was provided for forest management and risk mitigation purposes at the individual stand level. The approach proposed in this work has a wide potential for decision support, policy making and risk mitigation in southern European commercial conifer forests where large wildfires are the main natural hazard.  相似文献   

10.
Prescribed burning is used in many fire-prone ecosystems for wildfire mitigation and conservation of biodiversity. However, there is limited information about how biota responds to long-term fire management, especially at a whole-of-community level. We studied community responses to different fire interval sequences resulting from planned and unplanned fires in Mediterranean-climate ecosystems in the Warren bioregion of south-west Western Australia (SWA) to determine the resilience of the biota to contrasting fire regimes. Fire history data were used to identify contrasting fire interval sequences in forest and shrubland communities for the period 1972-2004. We surveyed vascular plants, ants, beetles, vertebrates and macrofungi at 30 sites to investigate community-level responses to consecutive short (SS: ≤5 years), consecutive long (LL: ≥10 years), one very long (VL: 30 years), or mixed/moderate (M: 6-9 years) fire interval(s). All sites had a common time-since-fire of ∼4 years at the commencement of sampling which was conducted over two years. Species richness and composition differed between forest and shrubland communities, but the influence of fire interval sequences on taxonomic groups was minimal and difficult to detect. There was weak evidence of compositional differences between SS and LL/VL regimes for plants, ants, beetles and macrofungi but no difference between these regimes and the intermediate disturbance M-regime. These results demonstrate the resilience of the biota in open forests and shrublands of SWA to contrasting fire interval sequences over the past 30 years. We conclude that occasional short (3-5 years) intervals between fires are unlikely to have a persistent effect on community composition, though maintaining a regime of short or long intervals may alter species composition and/or abundance. We suggest that variability in fire intervals is important for long-term conservation of the biota. For the Warren Region, prescribed burning at an intermediate level of disturbance and incorporating variability in interval length is recommended to achieve the dual objectives of wildfire mitigation and biodiversity conservation.  相似文献   

11.
The quantitative liana inventories made in five peninsular Indian independent forest sites, distributed in the Western Ghats, Eastern Ghats and on the Coromandel coast, were examined particularly with reference to site altitude and forest stature. Liana diversity totaled 148 species in 101 genera of 47 families, in a total sample of 47 ha. The coefficient of variability in species distribution among the five sites was used to identify an oligarchy in liana species by taking 55 abundant species from the species pool. Ordination analysis, based on presence–absence as well as relative density of liana species indicated a geographical differentiation among the five sites in both the ordinations with respect to site altitude. Liana density (stems>1.6 cm diameter) decreased with increasing altitude, whereas richness was highest at intermediate elevations. The mean liana density across the forest sites showed a weak negative correlation with forest stature. The lianas encountered in the five study sites fell under six climber types, of which twining was the chief climbing mechanism, both in terms of species diversity and density, and tendril climbers were more abundant in dry evergreen forests than in the wet evergreen forests. In liana diaspore dispersal modes, the majority of evergreen forest species possessed animal dispersal guilds, whereas wind-dispersal was prevalent in semi-evergreen and dry evergreen forests.  相似文献   

12.
Remote ponderosa pine (Pinus ponderosa) forests on the North Rim of Grand Canyon National Park, Arizona, USA provide valuable examples of reference conditions due to their relatively uninterrupted fire regimes, limited grazing history, and protection from logging. Wildfire is an important disturbance agent in upland forests of the Interior West, yet repeated measurements taken before and after lightning-ignited fires are rare. In 1999, a low-severity Wildland Fire Use fire burned 156 ha on Fire Point, a peninsula dominated by old-growth ponderosa pines, which had not burned for at least 76 years. We measured understory plant community and forest floor characteristics in 1998 (1 year before the fire) and 2001 (2 years after the fire) at this site and at nearby reference sites that did not burn in 1999 but have had continuing fire regimes throughout the past century. After the wildfire, the plant community at Fire Point shifted toward higher compositional similarity with the reference sites. Analysis of functional group composition indicated that this change was due primarily to an increase in annual and biennial forbs. Gayophytum diffusum, Polygonum douglasii, Chenopodium spp., Solidago spp., Elymus elymoides, Calochortus nuttallii, Hesperostipa comata, and Lotus spp. were indicative of forests influenced by recent fires. Species richness, plant cover, plant layer density and plant diversity were significantly lower at Fire Point than at the reference sites, possibly due to long-term fire exclusion, but the fire did not increase the rate of change in these variables after 2 years. Few exotic species were present at any site. Forest floor depths at Fire Point were reduced to depths similar to the reference sites, primarily due to consumption of the duff layer. There was a significant inverse relationship between the ratio of duff:litter and species richness. Compared to fire-excluded forests, old-growth ponderosa pine forests influenced by low-intensity surface fires generally have greater plant species richness (especially annual forbs) and lighter fuel loads. This study supports the continued application of the Wildland Fire Use strategy in old-growth montane forests to maintain and improve forest health by altering understory species composition and reducing fuel loads.  相似文献   

13.
The presence of over 429,000 ha of forest with spruce (Picea spp.) recently killed by spruce beetles (Dendroctonus rufipennis) on the Kenai Peninsula has raised the specter of catastrophic wildfire. Dendrochronological evidence indicated that spruce beetle outbreaks occurred on average every 50 years in these forests. We used 121 radiocarbon-dated soil charcoal samples collected from throw mounds of recently blown over trees to reconstruct the regional fire history for the last ca. 2500 years and found no relation between fire activity and past spruce beetle outbreaks. Soil charcoal data suggest that upland forests of white (Picea glauca) and Lutz (Picea x lutzii) spruce have not on average burned for 600 years (time-since-fire range 90 to ∼1500 years, at 22 sites) and that the mean fire interval was 400–600 years. It would thus appear that 10 or more spruce beetle outbreaks can occur for every cycle of fire in these forests. We caution, however, that a trend of warmer summers coupled with an increasing human population and associated sources of ignitions may create a greater fire risk in all fuel types than was present during the time period covered by our study. We suggest that forest management focus on creating fuel breaks between valued human infrastructure and all types of forest fuels, both green and dead.  相似文献   

14.
To examine the relationship between forest succession following fire and the composition of bird communities, we investigated the vegetation structure, bird population density, foraging behavior and guild structure in bamboo grasslands (11 years since the last fire), pine savanna (41 years), pine woodland (58 years), old-growth hemlock forest (never burned), and old-growth spruce forest (never burned) in the Tatachia area of central Taiwan. Canopy height, total foliage cover, tree density, total basal area of tree, total basal area of snags, foliage height diversity, and tree species richness all increased with successional age. However, shrub cover peaked in intermediate successional stages. The vertical profile of foliage cover was more diverse in later successional forests, which had more breeding bird species and ecological guilds. All the breeding bird species recorded in early and intermediate stages were also found distributed in the late successional forests. Because Taiwan has high precipitation and humidity, and most forest fires in Taiwan are caused by human activities, forest fires and large areas of early successional vegetation were probably rare in the mountain areas of Taiwan prior to the arrival of humans. Therefore, bird species have not had enough time to adapt to areas with early or intermediate successional vegetation. Moreover, late successional forests host all the major plant species found in the early and intermediate stages and have higher foliage height diversity index, which was positively correlated with the bird species richness and bird species diversity index in this study. As a result, all breeding bird species and guilds in the area can be found in late successional forests. Efforts for conserving avian diversity in Taiwan should focus on protecting the remaining native old-growth forests.  相似文献   

15.
Understanding both historic and current fire regimes is indispensable to sustainable forest landscape management. In this paper, we use a spatially explicit landscape simulation model, LANDIS, to simulate historic and current fire regimes in the Great Xing’an Mountains, in northeastern China. We analyzed fire frequency, fire size, fire intensity, and spatial pattern of burnt patches. Our simulated results show that fire frequency under the current fire scenario is lower than under the historic fire scenario; total area burnt is larger with lower fire intensity under the historic fire scenario, and smaller with higher fire intensity under the current fire scenario. We also found most areas were burned by high intensity fires under the current fire scenario, but by low to moderate fires under the historic fire scenario. Burnt patches exhibit a different pattern between the two simulation scenarios. Large patches burnt by high intensity class fires dominate the landscape under the current fire scenario, and under historic fire scenario, patches burnt by low to moderate fire intensity fires have relatively larger size than those burnt by high intensity fires. Based on these simulated results, we suggest that prescribed burning or coarse woody debris reduction should be incorporated into forest management plans in this region, especially on north-facing slopes. Tree planting may be a better management option on these severely burned areas whereas prescribed burning after small area selective cutting, retaining dispersed seed trees, may be a sound forest management alternative in areas except for the severely burned patches.  相似文献   

16.
Forest structure and floristic composition were studied in a series of 0.5 ha natural forest plots at four sites near Porto Trombetas in Pará State, Brazil, 11–12 years after being subjected to differing levels of above-ground biomass harvest and removal. In addition to undisturbed control plots, experimental treatments included: removal of most trees ≥45 cm DBH (low intensity harvest); removal of trees <20 and ≥60 cm DBH (moderate intensity harvest); clear-cutting (100% above-ground biomass removal). Post-harvest basal area growth generally increased with harvest intensity, and total basal areas for trees ≥5 cm DBH were, at the time of our study, 60% (in the clear-cut) to about 80% of those in the control plots. Biomass harvests stimulated recruitment and growth of residual trees, particularly in the smaller diameter classes, but had little effect on species richness for small trees, seedlings, vine, herbs, and grasses. Species richness for trees ≥15 cm DBH was greater in the control and low-intensity (74–75 species) than in the moderate intensity (47 species) and clear-cut (26 species) treatment plots. While the tree flora within all harvest treatments was broadly similar to the undisturbed (control) plots and included similar numbers of species of the major plant families typical of the surrounding forests, the more intensive harvest treatments, especially the clear-cut, were dominated by a higher proportion of short-lived, early successional tree species.  相似文献   

17.
Following disturbances, early-seral stages of forests provide a variety of structures. Whether this variety is a short-term phenomenon or influences forest succession for several decades or even longer is not known. We tested the hypotheses that after spruce dieback caused by bark beetles, a high spatial heterogeneity of stand structures will persist within stands and among stands even in advanced early-seral stages and that species taxonomical and functional diversity measures will reflect this heterogeneity. We used a chronosequence of unmanaged forests in the Berchtesgaden National Park (Germany) consisting of mature undisturbed spruce stands (control), stands belonging to an initial early-seral stage (~3 years after disturbance) and stands in an advanced early-seral stage (~20 years after disturbance). We analysed diversity and heterogeneity of these forest stands including stand structure, species density, species composition and functional–phylogenetic diversity of vascular plants, wood-inhabiting fungi and saproxylic beetles within plots, among plots of the same successional stage and among stages. Stands of the advanced early-seral stage were characterized by a high spatial heterogeneity of structural attributes, such as crown cover, regeneration density and spatial distribution of trees. Among-plot taxonomic beta diversity was highest in the advanced early-seral stage for beetles, but lowest for fungi, while beta diversity of plants among plots remained unchanged during succession. The mosaic of successional stages initiated by bark beetles increased the gamma diversity of the study area, especially for fungi and beetles. Our findings support the hypothesis that structural heterogeneity continues for at least two decades at stand and landscape scales and that species turnover among successional stages is a major mechanism for gamma diversity in forests after bark beetle disturbance.  相似文献   

18.
Species can persist in a landscape with recurrent disturbances either through local survival or by dispersing to sites of a preferred successional stage. This study investigated in what extent forest floor dwelling land snails survived forest fires and clear-cutting. Snail fauna in LFH (litter, fermenting litter and humus) samples below retained aspen trees in disturbed areas were compared with samples under scattered aspens in adjacent forests by extracting snails from LFH samples below five aspens in several stands of each type (five forest fires, six clear-cuts, and seven undisturbed forests). LFH samples from burnt sites had a higher pH than from forests, but on average a lower abundance of individual snails (11 vs. 30 in 0.5 l LFH) and 50% lower species density (3 vs. 6 species). The abundances and species densities in the clear-cuts were less affected. There was generally a positive relationship between pH and both species density and abundance in all the stand types. Burning apparently depleted the snail fauna considerably and some species may be dependent on dispersal if they are to recover within the burnt area, while the snail assemblages at clear-cuts did not differ significantly in species composition from adjacent forests. The positive relationship between pH and snail prevalence on the burnt sites raises questions regarding the pre- and post-fire spatial variation in pH (and available minerals) within and among stands and how it relates to snail survival rates and their capacity to track suitable places after the disturbance. Retained aspens at clear-cuts seem to harbour a forest like land snail fauna.  相似文献   

19.
We examined patterns of variation in richness, diversity, and composition of understory vascular plant communities in mixedwood boreal forests of varying composition (broadleaf, mixedwood, conifer) in Alberta, Canada, before and for 2 years following variable-retention harvesting (clearcut, 20 and 75% dispersed green tree retention, control). Broadleaf-dominated forests differed from mixedwood or conifer-dominated forests in that they had greater canopy cover, litter depth, soil nitrogen, warmer soils, as well as greater shrub cover, herb and shrub richness and diversity (plot scale). In contrast, conifer, and to a lesser extent mixedwood, forest had greater β diversity than broadleaf forest. Overall, mixedwood and conifer forests were similar to one another, both differed from broadleaf forest. Several species were found to be significant indicators of broadleaf forest but most of these also occurred in the other forest types. Understory composition was related to canopy composition and edaphic conditions. Variable-retention harvesting had little effect on understory cover, richness, or diversity but resulted in reduced richness and β diversity at a larger scale. The clearcut and 20% treatments affected composition in all forest types. Early successional species and those common in disturbed sites were indicators of harvesting while evergreen, shade-tolerant understory herbs were indicators of the control forest and 75% retention harvest. We conclude that it is important to maintain a range of variation in canopy composition of mixedwood forests in order to conserve the associated understory communities. The presence of conifers in these forests has a particularly important influence on understory communities. The threshold for a lifeboat effect of variable-retention harvesting is between 20 and 75% retention. Examination of richness and β diversity at a variety of scales can provide interesting information on effects of harvesting on spatial reorganization and homogenization of understory plant communities.  相似文献   

20.
Forest fires are influenced by several factors,including forest location, species type, age and density,date of fire occurrence, temperatures, and wind speeds,among others. This study investigates the quantitative effects of these factors on the degree of forest fire disaster using nonparametric statistical methods to provide a theoretical basis and data support for forest fire management.Data on forest fire damage from 1969 to 2013 was analyzed. The results indicate that different forest locations and types, fire occurrence dates, temperatures, and wind speeds were statistically significant. The eastern regions of the study area experienced the highest fire occurrence,accounting for 85.0% of the total number of fires as well as the largest average forested area burned. April, May, and October had more frequent fires than other months,accounting for 78.9%, while September had the most extensive forested area burned(63.08 ha) and burnt area(106.34 ha). Hardwood mixed forest and oak forest had more frequent fires, accounting for 31.9% and 26.0%,respectively. Hardwood-conifer mixed forest had the most forested area burned(50.18 ha) and burnt area(65.09 ha).Temperatures, wind speeds, and their interaction had significant impacts on forested area burned and area burnt.  相似文献   

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