Resilience of European larch (<Emphasis Type="Italic">Larix decidua</Emphasis> Mill.) forests to wildfires in the western Alps

European larch is a dominant species in the subalpine belt of the western Alps. Despite recent increases in wildfire activity in this region, fire ecology of European larch is poorly understood compared to other larch species around the world. This study aims to assess whether European larch forests are resilient to fires, and to find out the factors that drive such resilience. We assessed the recovery of larch forests along a gradient of fire severity (low, moderate, high) based on the abundance and dominance of post-fire larch regeneration. We established 200 plots distributed among burned larch forests in nine wildfires that occurred between 1973 and 2007 in the western Alps. We included variables regarding topography, climate, fire severity, fire legacies, ground cover, grazing intensity, and time since fire. To evaluate potential drivers of larch recruitment, we applied generalized linear mixed models (GLMM) and random forests (RF). Larch regeneration was much more abundant and dominant in the moderate- and high-severity fire classes than in the low-severity class. More than half of the plots in the moderate- and high-severity classes were classified as resilient, i.e., post-fire larch regeneration was enough to recover a larch stand. GLMM and RF produced complementary results: fire severity and legacies, such as snags, canopy cover and distance to seed source, were crucial factors explaining post-fire larch recruitment. This study shows that fire has a positive effect on larch regeneration, and we conclude that European larch forests are highly resilient to mixed-severity fires in the western Alps.     

The influence of mountain pine beetle outbreaks and drought on severe wildfires in northwestern Colorado and southern Wyoming: A look at the past century

Outbreaks of bark beetles and drought both lead to concerns about increased fire risk, but the relative importance of these two factors is the subject of much debate. We examined how mountain pine beetle (MPB) outbreaks and drought have contributed to the fire regime of lodgepole pine forests in northwestern Colorado and adjacent areas of southern Wyoming over the past century. We used dendroecological methods to reconstruct the pre-fire history of MPB outbreaks in twenty lodgepole pine stands that had burned between 1939 and 2006 and in 20 nearby lodgepole pine stands that were otherwise similar but that had not burned. Our data represent c. 80% of all large fires that had occurred in lodgepole pine forests in this study area over the past century. We also compared Palmer Drought Severity Index (PDSI) and actual evapotranspiration (AET) values between fire years and non-fire years. Burned stands were no more likely to have been affected by outbreak prior to fires than were nearby unburned stands. However, PDSI and AET values were both lower during fire years than during non-fire years. This work indicates that climate has been more important than outbreaks to the fire regime of lodgepole pine forests in this region over the past century. Indeed, we found no detectable increase in the occurrence of high-severity fires following MPB outbreaks. Dry conditions, rather than changes in fuels associated with outbreaks, appear to be most limiting to the occurrence of severe fires in these forests.     

The ecology of mixed severity fire regimes in Washington, Oregon, and Northern California

Forests characterized by mixed-severity fires occupy a broad moisture gradient between lower elevation forests typified by low-severity fires and higher elevation forests in which high-severity, stand replacing fires are the norm. Mixed-severity forest types are poorly documented and little understood but likely occupy significant areas in the western United States. By definition, mixed-severity types have high beta diversity at meso-scales, encompassing patches of both high and low severity and gradients in between. Studies of mixed-severity types reveal complex landscapes in which patch sizes follow a power law distribution with many small and few large patches. Forest types characterized by mixed severity can be classified according to the modal proportion of high to low severity patches, which increases from relatively dry to relatively mesic site conditions. Mixed-severity regimes are produced by interactions between top-down forcing by climate and bottom-up shaping by topography and the flammability of vegetation, although specific effects may vary widely across the region, especially the relation between aspect and fire severity. History is important in shaping fire behavior in mixed-severity landscapes, as patterns laid down by previous fires can play a significant role in shaping future fires. Like low-severity forests in the western United States, many dry mixed-severity types experienced significant increases in stand density during the 20th century, threatening forest health and biodiversity, however not all understory development in mixed-severity forests increases the threat of severe wild fires. In general, current landscapes have been homogenized, reducing beta diversity and increasing the probability of large fires and insect outbreaks. Further loss of old, fire tolerant trees is of particular concern, but understory diversity has been reduced as well. High stand densities on relatively dry sites increase water use and therefore susceptibility to drought and insect outbreaks, exacerbating a trend of increasing regional drying. The need to restore beta diversity while protecting habitat for closed-forest specialists such as the northern spotted owl call for landscape-level approaches to ecological restoration.     

Thermal characteristics of amphibian microhabitats in a fire-disturbed landscape

Disturbance has long been a central issue in amphibian conservation, often regarding negative effects of logging or other forest management activities, but some amphibians seem to prefer disturbed habitats. After documenting increased use of recently burned forests by boreal toads (Bufo boreas), we hypothesized that burned habitats provided improved thermal opportunities in terrestrial habitats. We tested this hypothesis by conducting a radio telemetry study of habitat use (reported previously) and by using physical models that simulated the temperature of adult toads. We deployed 108 physical models in and adjacent to a 1-year old burn using a fully-replicated design with three burn severities (unburned, partial, high severity) and four microhabitats (open surface, under vegetation, under log, in burrow). Model temperatures were compared to a range of preferred temperatures in published studies. We found 70% more observations within the preferred temperature range of B. boreas in forests burned with high severity than in unburned areas. Burned forest was warmer than unburned forest across all microhabitats, but the largest relative difference was in burrows, which averaged 3 °C warmer in high-severity burn areas and remained warmer though the night. More than twice as many observations were within the preferred temperature range in high-severity burrows than in unburned burrows. Areas burned with high severity were still warmer than unburned forest 3 years after the fire. Habitat use of toads during the concurrent radio telemetry study matched that predicted by the physical models. These results suggest there are fitness-linked benefits to toads using burned habitats, such as increased growth, fertility, and possibly disease resistance. However, increased soil temperatures that result from wildfire may be detrimental to other amphibian species that prefer cooler temperatures and stable environments. More broadly, our data illustrate the use of physical models to measure and interpret changes that amphibians may experience from disturbance, and highlight the need for research linking vital rates such as growth and survival to disturbance.     

Factors influencing the formation of unburned forest islands within the perimeter of a large forest fire

Large forest fires have recently increased in frequency and severity in many ecosystems. Due to the heterogeneity in fuels, weather and topography, these large fires tend to form unburned islands of vegetation. This study focuses on a large forest fire that occurred in north-eastern Spain in 1998, which left large areas of unburned vegetation within its perimeter. Based on a satellite post-fire severity map we searched for the relative influence of biotic and abiotic factors leading to unburned island formation. We divided the area of the fire into individual units we called “slopes” which were meant to separate the differential microclimatic effects of contrasted aspects. The number of unburned islands and their areas were related to 12 variables that influence their formation (i.e. land cover composition, aspect, steepness, forest structure, two landscape indices and weather variables). We hypothesized that unburned vegetation islands would concentrate on northern aspects, in less flammable forests (i.e. broadleaf species) and higher fragmentation to interrupt the advance of fire. While north and western aspects did have a higher presence of unburned vegetation islands, our study suggests greater presence of islands in slopes that are larger (i.e. more continuous areas with relatively homogeneous aspect), with greater proportions of forest cover, with higher wood volumes and with lower proportions of broadleaf species. Climate also played a role, with relative humidity and wind speed positively and negatively correlated to island formation, respectively. Unburned vegetation was more frequent on slopes with lower diversity of land covers and higher dominance of one land cover in the slope. Since slopes with only one land cover (i.e. forests) had more islands than slopes with multiple cover types, we infer that under severe meteorological conditions, fragmented forests can be more affected by wind and by water stress, thus burning more readily than forests that are protected from this edge phenomenon. These results would reinforce forest management strategies that avoid linear features (fire-lines and fire-breaks), to enhance fuel treatments that focus on areas and minimize fragmentation.     

A predictive model of burn severity based on 20-year satellite-inferred burn severity data in a large southwestern US wilderness area

We describe and then model satellite-inferred severe (stand-replacing) fire occurrence relative to topography (elevation, aspect, slope, solar radiation, Heat Load Index, wetness and measures of topographic ruggedness) using data from 114 fires > 40 ha in area that occurred between 1984 and 2004 in the Gila Wilderness and surrounding Gila National Forest. Severe fire occurred more frequently at higher elevations and on north-facing, steep slopes and at locally wet, cool sites, which suggests that moisture limitations on productivity in the southwestern US interact with topography to influence vegetation density and fuel production that in turn influence burn severity. We use the Random Forest algorithm and a stratified random sample of burn severity pixels with corresponding pixels from 15 topographic layers as predictor variables to build an empirical model predicting the probability of occurrence for severe burns across the entire 1.4 million ha study area. Our model correctly classified severity with a classification accuracy of 79.5% when burn severity pixels were classified as severe vs. not severe (two classes). Because our model was derived from data sampled across many fires over a 20-year period, it represents average probability of severe fire occurrence and is unlikely to predict burn severity for individual fire events. However, we believe it has potential as a tool for planning fuel treatment projects, in management of actively burning fires, and for better understanding of landscape-scale burn severity patterns.     

Fire Occurrence Environments in Pinus pumila Forests

In recent years, many serious forest fires occurred in precious Pinus pumila forests in Daxing'anling Mountains of Heilongjiang Province and Inner Mongolia. But up to now, there is still a lack of proper understanding of fire occurrence environments in P. pumila forests. In present paper, we investigated and studied the fire occurrence environments. The results showed that fires in P. pumila forests had their own special fire environments. Abundant fuel, drought weather, dry thunder and high altitude terrai...     

Stand structure, fuel loads, and fire behavior in riparian and upland forests, Sierra Nevada Mountains, USA; a comparison of current and reconstructed conditions

Fire plays an important role in shaping many Sierran coniferous forests, but longer fire return intervals and reductions in area burned have altered forest conditions. Productive, mesic riparian forests can accumulate high stem densities and fuel loads, making them susceptible to high-severity fire. Fuels treatments applied to upland forests, however, are often excluded from riparian areas due to concerns about degrading streamside and aquatic habitat and water quality. Objectives of this study were to compare stand structure, fuel loads, and potential fire behavior between adjacent riparian and upland forests under current and reconstructed active-fire regime conditions. Current fuel loads, tree diameters, heights, and height to live crown were measured in 36 paired riparian and upland plots. Historic estimates of these metrics were reconstructed using equations derived from fuel accumulation rates, current tree data, and increment cores. Fire behavior variables were modeled using Forest Vegetation Simulator Fire/Fuels Extension.Riparian forests were significantly more fire prone under current than reconstructed conditions, with greater basal area (BA) (means are 87 vs. 29 m²/ha), stand density (635 vs. 208 stems/ha), snag volume (37 vs. 2 m³/ha), duff loads (69 vs. 3 Mg/ha), total fuel loads (93 vs. 28 Mg/ha), canopy bulk density (CBD) (0.12 vs. 0.04 kg/m³), surface flame length (0.6 vs. 0.4 m), crown flame length (0.9 vs. 0.4 m), probability of torching (0.45 vs. 0.03), predicted mortality (31% vs. 17% BA), and lower torching (20 vs. 176 km/h) and crowning indices (28 vs. 62 km/h). Upland forests were also significantly more fire prone under current than reconstructed conditions, yet changes in fuels and potential fire behavior were not as large. Under current conditions, riparian forests were significantly more fire prone than upland forests, with greater stand density (635 vs. 401 stems/ha), probability of torching (0.45 vs. 0.22), predicted mortality (31% vs. 16% BA), and lower quadratic mean diameter (46 vs. 55 cm), canopy base height (6.7 vs. 9.4 m), and frequency of fire tolerant species (13% vs. 36% BA). Reconstructed riparian and upland forests were not significantly different. Our reconstruction results suggest that historic fuels and forest structure may not have differed significantly between many riparian and upland forests, consistent with earlier research suggesting similar historic fire return intervals. Under current conditions, however, modeled severity is much greater in riparian forests, suggesting forest habitat and ecosystem function may be more severely impacted by wildfire than in upland forests.     

Bird communities following high-severity fire: Response to single and repeat fires in a mixed-evergreen forest,Oregon, USA

Fire is a widespread natural disturbance agent in most conifer-dominated forests. In light of climate change and the effects of fire exclusion, single and repeated high-severity (stand-replacement) fires have become prominent land management issues. We studied bird communities using point counting in the Klamath-Siskiyou ecoregion of Oregon, USA at various points in time after one or two high-severity fires. Time points included 2 and 3 years after a single fire, 17 and 18 years after a single fire, 2 and 3 years after a repeat fire (15 year interval between fires), and >100 years since stand-replacement fire (mature/old-growth forest). Avian species richness did not differ significantly among habitats. Bird density was highest 17 and 18 years after fire, lowest 2 years after fire, and intermediate in repeat burns and unburned forest. Bird community composition varied significantly with habitat type (A = 0.24, P < 0.0001) with two distinct gradients in species composition relating to tree structure (live to dead) and shrub stature. Using indicator species analysis, repeat burns were characterized by shrub-nesting and ground-foraging bird species while unburned mature forests were characterized by conifer-nesting and foliage-gleaning species. Bird density was not related to snag basal area but was positively related to shrub height. Contrary to expectations, repeated high-severity fire did not reduce species richness, and bird densities were greater in repeat burns than in once-burned habitats. Broad-leaved hardwoods and shrubs appear to play a major role in structuring avian communities in the Klamath-Siskiyou region. In light of these results, extended periods of early seral broadleaf dominance and short-interval high-severity fires may be important to the conservation of avian biodiversity.     

Coarse woody debris and canopy cover in an old-growth Jeffrey pine-mixed conifer forest from the Sierra San Pedro Martir, Mexico

The cultural practices associated with Euro-American settlement in the United States have altered forest structure and ultimately changed fundamental ecosystem processes. Coarse woody debris (CWD) and canopy cover are recognized as having great importance for many wildlife species and ecological processes. Little information is available from forests on historical levels of canopy cover and CWD before European settlement. A great deal of uncertainty exists concerning the long-term role of fire and the dynamics of CWD, especially in forests that once experienced frequent, low-moderate intensity fire regimes. The objective of this study was to quantify CWD and forest canopy cover in an area where harvesting has never occurred and limited fire suppression began in the 1970s. This study was done in Jeffrey pine-mixed conifer forests in the Sierra San Pedro Martir (SSPM) in northwestern Mexico. Canopy cover, canopy closure, and CWD were sampled on a grid of plots. Average canopy cover was 26.8%, average canopy closure was 40.1%. A total of 102 CWD pieces were measured, and nearly half of the plots (45.7%) had no CWD present. Average CWD density, percent cover, volume, and weight were 108 pieces ha⁻¹, 1.5%, 47.5 m³ ha⁻¹, and 15.7 tonnes ha⁻¹, respectively. All of the CWD sampled were in the later stages of decay. Less than average values for CWD density, percent cover, volume, and weight were recorded in 57%, 64%, 67%, and 69% of the plots, respectively. CWD dynamics in forests that experience frequent, low-moderate intensity fires are fundamentally different than those having long-interval, high-severity fires. There was a large amount of variability in all CWD and forest canopy cover measurements taken from Jeffrey pine-mixed conifer forests in the SSPM. Spatial heterogeneity in forest structure should be included in the desired conditions of xeric, pine-dominated forests in the United States that once experienced frequent, low-moderate intensity fire regimes. It should be noted that heterogeneity by itself may not lead to sustainable forests unless that heterogeneity includes stand structures that are resistant/resilient to high-severity fire, drought, insects, and disease.     

Real versus perceived conflicts between restoration of ponderosa pine forests and conservation of the Mexican spotted owl

Progress in implementing ecosystem approaches to conservation and restoration is slowed by legitimate concerns about the effects of such approaches on individual imperiled species. The perceived conflict between the restoration of fire-excluded forests and concomitant reduction of dense fuels and high-severity wildfire, versus the recovery of endangered species, has led to a policy ambiguity that has slowed on-the-ground action at a time when active management is urgently needed, both for ecosystem restoration and species conservation. The Mexican spotted owl (Strix occidentalis lucida) in the southwestern U.S.A. is emblematic of this perceived conflict, with numerous appeals and lawsuits focused on the species and vast acres of forest managed with habitat quality for this species in mind. We use spatial analysis across large landscapes in Arizona to examine potential conflicts between the desire to reduce the likelihood of uncharacteristically severe wildfire and restore native fire regimes, and the concurrent desire and legal mandate to manage forests for the recovery of the owl. Our spatially explicit analysis indicates that real conflicts between these management objectives exist, but that locations where conflicts might inhibit active forest management represent less than 1/3 of the 811,000 ha study region. Furthermore, within the areas where conflicts might be expected, the majority of the forest could be managed in ways that would reduce fire hazard without eliminating owl habitat. Finally, management treatments that emphasize ecosystem restoration might improve the suitability of large areas of forest habitat in the southwest that is currently unsuitable for owls. These results demonstrate that even where policy conflicts exist, their magnitude has been overstated. Active restoration of dry forests from which fire has been excluded is compatible in many areas with conservation and recovery of the owl. Identifying and prioritizing areas to meet the dual goals of ecosystem restoration and imperiled species conservation require a broad spatial approach that is analytically feasible but currently underutilized. Working together, conservation biologists, restoration ecologists, and forest managers can employ landscape-level spatial analysis to identify appropriate areas for management attention, identify suitable management practices, and explore the predicted consequences of alternative management scenarios on forests, fire ecology, and the fate of sensitive species of conservation concern.     

Evaluating the efficiency of the Dong model in determining fire vulnerability in Iran's Zagros forests

Recent fires in Iran's Zagros forests have inflicted heavy,extensive losses to the environment,forests,villages,and forest inhabitants,resulting in a huge financial loss to the country.With the increasing risk of fire and the resulting losses,it has become ever more necessary to design and develop efficient fire control and prediction procedures.The present study utilizes the Dong model to develop a map of areas vulnerable to fire in the Zarivar lake forests as a representative sample of Zagros forests.The model uses as its inputs some of the most significant factors(such as vegetation,physiographic features,and the human component) that affect the fire occurrence and spread.Having assigned weights to each factor based on the model,all maps were overlapped in the ArcMap and then the region was divided into five zones.The results showed that 74% of the region was located in three classes:highly vulnerable,vulnerable,and medially vulnerable.To validate the proposed zoning map it was compared with a map based on real data obtained from previous fires.The results showed that 81% of fire incidents were located in highly vulnerable,vulnerable and medially vulnerable zones.Furthermore,the findings indicated a medium to a high degree of fire vulnerability in Zarivar Lake forests.     

Chapter 12. A Wildfire and Emissions Policy Model for the Boise National Forest

Summary

We utilized the Boise National Forest's Hazard/Risk model, along with fire history records and fire behavior models, to estimate the current and anticipated levels of large wildfires and associated greenhouse gas and particulate emissions based on the forest condition and wildfire regime on the BNF. The model indicated that the forests at greatest risk of large, intense wildfires are the dense pondero-sa pine-Douglas-fir forests that make up over 1.1 million acres on the forest. We conclude that without an aggressive treatment program to reduce large areas of contiguous heavy fuel loadings the forest will be burned at an annual average rate of about 7.5% of the remaining at-risk forest. Using recent fire data to develop average patterns of intensity in wildfires within this forest type, we estimate that emissions will average around 1 million tons of carbon (C) per year over the next 20 years as the bulk of the ponderosa pine forests are burned. An aggressive treatment program featuring the removal of fuels where necessary, and prescribed fire as a means of re-introducing fire to these ecosystems, would result in a 30-50 percent reduction in the average annual wildfire experienced in the dense ponderosa pine forests, a 14-35% decrease in the average annual C emissions, and a 10-31% decrease in particulate emissions. We argue that the most effective way to curb emissions is with an aggressive treatment program linked to a landscape-based ecosystem management plan. This would have the effect of breaking up large contiguous landscape patterns so that fires become more patchy and diverse in their environmental impact, resulting in significantly reduced emissions as well as improved landscape diversity.     

Fire history and fire–climate relationships along a fire regime gradient in the Santa Fe Municipal Watershed, NM, USA

The Santa Fe municipal watershed provides up to 40% of the city's water and is at high risk of a stand-replacing fire that could threaten the water resource and cause severe ecological damage. Restoration and crown fire hazard reduction in the ponderosa pine (PP) forest is in progress, but the historic role of crown fire in the mixed-conifer/aspen (MC) and spruce-dominated forests is unknown but necessary to guide management here and in similar forests throughout the southwestern United States. The objective of our study was to use dendroecological techniques to reconstruct fire history and fire–climate relationships along an elevation, forest type, and fire regime gradient in the Santa Fe River watershed and provide historical ecological data to guide management. We combined systematic (gridded) sampling of forest age structure with targeted sampling of fire scars, tree-ring growth changes/injuries, and death dates to reconstruct fire occurrence and severity in the 7016 ha study area (elevation 2330–3650 m). Fire scars from 141 trees (at 41 plots) and age structure of 438 trees (from 26 transects) were used to reconstruct 110 unique fire years (1296–2008). The majority (79.0%) of fires burned during the late spring/early summer. Widespread fires that scarred more than 25% of the recording trees were more frequent in PP (mean fire interval (MFI)_25% = 20.8 years) compared to the MC forest (31.6 years). Only 24% of the fires in PP were recorded in the MC forest, but these accounted for a large percent of all MC fires (69%). Fire occurrence was associated with anomalously wet (and usually El Niño) years preceding anomalously dry (and usually La Niña) years both in PP and in the MC forest. Fire in the MC occurred during more severe drought (mean summer Palmer Drought Severity Index; PDSI = −2.59), compared to the adjacent PP forest (PDSI = −1.03). The last fire in the spruce forest (1685) was largely stand-replacing (1200 ha, 93% of sampled area), recorded as fire scars at 68% of plots throughout the MC and PP forests, and burned during a severe, regional drought (PDSI = −6.92). The drought–fire relationship reconstructed in all forest types suggests that if droughts become more frequent and severe, as predicted, the probability of large, severe fire occurrence will increase.     

Herbaceous species diversity in relation to fire severity in Zagros oak forests,Iran

Zagros forests are mainly covered byQuercus brantii L. coppices and oak sprout clumps occupy the forest area like patches. We investigated post-fire herbaceous diversity in the first growing season after fire. For this purpose neighboring burned and unburned areas were selected with the same plant species and ecological conditions. The data were collected from areas subjected to different fire severities. Overall 6 treatments were considered with respect to fire severity and the mi-crosites of inside and outside of oak sprout clumps including： unburned inside and outside of sprout clumps （Ni and No）, inside of sprout clumps that burned with high fire severity （H）, inside of sprout clumps that burned with moderate fire severity （M）, outside of sprout clumps that burned with low fire severity （OH and OM）. Different herbaceous com-position was observed in the unburned inside and outside of oak sprout clumps. The species diversity and richness were increased in treatments burned with low and moderate fire severity. However, in treatment burned with high fire severity （H）, herbaceous cover was reduced, even-ness was increased, and richness and diversity were not significantly changed. We concluded that besides the microsites conditions in forest, fire severity is an inseparable part of the ecological effect of fire on her-baceous composition.     

Effects of fuel treatments on carbon-disturbance relationships in forests of the northern Rocky Mountains

Fuel treatments alter conditions in forested stands at the time of the treatment and subsequently. Fuel treatments reduce on-site carbon and also change the fire potential and expected outcome of future wildfires, including their carbon emissions. We simulated effects of fuel treatments on 140 stands representing seven major habitat type groups of the northern Rocky Mountains using the Fire and Fuels Extension to the Forest Vegetation Simulator (FFE-FVS). Changes in forest carbon due to mechanical fuel treatment (thinning from below to reduce ladder fuels) and prescribed fire were explored, as well as changes in expected fire behavior and effects of subsequent wildfire. Results indicated that fuel treatments decreased fire severity and crown fire occurrence and reduced subsequent wildfire emissions, but did not increase post-wildfire carbon stored on-site. Conversely, untreated stands had greater wildfire emissions but stored more carbon.     

Forest Fire Risk Zone Modeling Using Logistic Regression and GIS: An Iranian Case Study

Forest fires are an important environmental concern worldwide, affecting the soil, forests and human lives. During the process of burning, soil nutrients are depleted and the soil is subsequently more vulnerable to erosion. Nowadays it is necessary to identify the factors influencing the occurrence of fire and fire hazard areas, in order to minimize the frequency of fire and avert damage. Logistic regression was used to study the forest fire risk and identify the most influential factors in the occurrence of forest fires. Climatic variables (temperature and annual precipitation), human factors (distance from streams and farmland) and physiography (land slope and elevation) were considered and their correlation with the occurrence of fires investigated. Results of model validation and sensitivity of various areas to fire were examined with the ROC coefficient and Hosmer–Lemeshow test. The estimated coefficients for the independent variables indicated that the probability of occurrence of fire is negatively related to land slope, site elevation and distance from farmlands, but is positively related to amount of annual precipitation.     

Individual-based analysis of tree establishment and forest stand development within 25?years after wind throw

Wind throw is a common disturbance in forest ecosystems. Because many forests are intensively used our knowledge on forest dynamics after such disturbances is limited. In the Bavarian Forest National Park/Germany after the wind throw event in summer 1983, we started our long-term observation in nearly natural Norway spruce forests within 5-year intervals up to 2010. A part of the affected stands was cleared, while another part was left untouched for natural development. Here, we focused on the tree species regeneration, using an individual-based approach. We expected that tree species regeneration in both management types would follow different succession pathways. Indeed, we found different regeneration characteristics, depending on whether the area had been cleared or left unmanaged. For example, for the target species Norway spruce, a chronic regeneration during the first two decades with low numbers, but a high survival rate of individuals, and for the pioneer species birch, pulse regeneration with high numbers of individuals only at the beginning and high individual loss during the following years occurred. Unmanaged and cleared wind throw areas, respectively, offer different quantities of micro-sites: the pit and mound structure as mineral soil disturbance was limited to less than 1/4 in the untouched area, whereas there was mineral soil disturbance more or less everywhere on the cleared parts. Type and intensity of disturbance allow a wide range of succession pathways after wind throw, based on the fundamental processes of germination and competition. Therefore, for protection area management as well as for forest management, the human activity immediately after the event is crucial. Because each management impact will change the succession pathway fundamentally any impact has to be omitted in protection areas with the main goal of natural vegetation succession. Also in managed forests abdication of any impact on small areas may improve the natural structures and biodiversity of forests.     

Forest Fires and Prevention Strategies in Northwestern Region of China

The paper described the natural conditions and forest types in Northwestern Region of China. Most forests in the region are distributed in subalpine areas. It is important to protect the existent forests in the region for maintaining ecological balance. According to the statistics results of 1991~2000, the paper analyzes the forest fires distribution and fire severity. Annually the numbers of forest fires range from 52 to 240. The incidence rate of forest fires in Northwestern Region is under 0.33 per ten thousand ha. There are 0.67-64.4 ha burned area per ten thousand ha forest. The main reasons for forest fires lie in the dry weather conditions, many firebrands, and high fuel loading. The strategies of fire management in the region are to stress the fire education in forest regions, strength the firebrands' management, emphasize the fuel management, and improve the fire monitoring and fire control ability.