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1.

Introduction   

This article explores the possibility of including multiple spatial scales into a mixed model for predicting the density of human-caused fire ignitions in Catalonia (North-East Spain).  相似文献   

2.

• Introduction  

The abandonment of rural areas has led to an increase of the fire-prone European gorse (Ulex europaeus L.) communities in some regions, where prescribed burning is a technique applied to control them. Understanding flammability changes after treatments is crucial for the sustainable use of fire.  相似文献   

3.

• Introduction   

Laricio pine (Pinus nigra J.F. Arn. ssp. laricio (Poiret) Maire var Corsicana Hyl.) is a form of black pine endemic to Corsica, that may now be under threat due to current fire regimes and competition with maritime pine (Pinus pinaster Aiton).  相似文献   

4.

Background   

The potential of forest to regenerate after harvesting is a key element for sustainability of the ecosystem. For semi-arid tropical savanna environments, managing resprouts after tree cutting is ideally suited because of the natural ability of many indigenous species to regenerate vegetatively. Regeneration in this ecosystem is, however, prone to many disturbance factors such as fire and grazing by livestock.  相似文献   

5.

? Context

The Mediterranean Basin is a fire-prone area. Pinus halepensis Mill. is a naturally growing conifer which is frequently used for reforestation and restoration as it displays some degree of adaption to fire. One of the traits conferring tolerance to fire is the frequent presence of serotinous cones that are thought to protect seeds from fire damage.

? Aim

We checked for the physiological responses of seeds to different intensities of fire and related them to the degree of serotiny of the cones.

? Methods

Germination percentage, mean germination rate and enzymatic activity (??-amylase and protease) were recorded for seeds burned either free or enclosed in cones. We included as experimental factors the following: fire intensity, serotiny and time during which seeds were stored in cones after harvesting and germination stage.

? Results

Burned seeds (released and enclosed) developed in serotinous cones exhibited higher heat insulation. In released seeds, germination was decreasing according to increasing fire intensity, although we found differences depending on site, serotiny and time stored after harvesting. The enzymatic activity was also found to be related to serotiny and fire intensity.

? Conclusion

Serotiny is an adaptive trait increasing the tolerance to fire which should be promoted in natural and restored populations.  相似文献   

6.

Context

After wildfire, surviving trees are of major ecological importance as they can help in the post-fire regeneration process. Although these trees may be damaged, they may also benefit from reduced fuel hazard and competition. However, little is known about the long-term growth response of surviving trees.

Aims

This study aims to explain short- to long-term variations in the postfire growth of surviving black pines in an area burnt in 1994, focusing on levels of fire severity and tree sizes.

Methods

Relative basal area increments were used to detect time-course variations in postfire radial tree growth depending on fire severity. Linear mixed-effects models were used to describe the factors affecting postfire ring growth.

Results

In the short term, fire caused stronger reduction in growth in small trees with increasing bole char height. However, as time since fire increased, a positive effect of fire on growth due to reduced competition counteracted the short-term fire impacts. Indeed, small surviving trees demonstrated a surge in growth 15 years after the fire.

Conclusion

It was concluded that reduced competition might offset the short-term negative effects of fire in surviving black pines.  相似文献   

7.

Context

Density management diagrams (DMDs) are useful for designing, displaying and evaluating alternative density management regimes for a given stand-level management objective. The inclusion of variables related to crown fire potential within DMDs has not previously been considered.

Aims

The aim of this study was to include isolines of variables related to crown fire initiation and spread in DMDs to enable identification of stand structures associated with different types of wildfire.

Methods

Biometric and fuel data from maritime pine (Pinus pinaster Ait.) stands in NW Spain were used to construct DMDs. Different surface and crown fire behaviour models were used together to estimate crown fire potential.

Results

The crown fire potential varied greatly throughout development of the maritime pine stands. Low stands were more prone to crowning. The type of crown fire was mainly determined by stand density.

Conclusion

The DMDs developed can be used to identify relationships between stand structure and crown fire potential, thus enabling the design of thinning schedules aimed at reducing the likelihood of crowning.  相似文献   

8.

Introduction   

Trees in two compartments of the mixed deciduous forest Draved Forest have been monitored regularly for 50 years.  相似文献   

9.

• Context   

In July 2005, a wildfire occurred in windthrown spruce forests in High Tatra Mountains and damaged roughly 229 ha of previously clear-cut area.  相似文献   

10.

• Context  

In January 2008, a freeze in southern China, unprecedented in 50 years, severely affected local subtropical coniferous plantations.  相似文献   

11.

• Introduction   

Accurate estimation of aboveground biomass is essential to better understand the carbon cycle in forest ecosystems.  相似文献   

12.
13.
14.

Introduction   

Wood quality is an important criterion in the selection of superior genotypes when breeding for solid wood.  相似文献   

15.

Introduction   

Extrapolating plot data to broader spatial scales depends largely on environmental heterogeneity.  相似文献   

16.

Key message

In the African rim of the Western Mediterranean Basin, cork oak forests and pine plantations coexist. Under similar fire regimes, cork oak forest is more resilient in terms of habitat structure (canopy, understory, and complexity of vegetation strata) than pine plantation. By contrast, both woodland types show similar resilience in plant species composition. Resilience in habitat structure varies between the two woodland types because of the resprouting and seeding strategies of cork oak and pine species, respectively. These differences can be relevant for the conservation of biodiversity of forested ecosystems in a future scenario of increased fire frequency and scale in the Mediterranean basin.

Context

Wildfires have major impacts on ecosystems globally. In fire-prone regions, plant species have developed adaptive traits (resprouting and seeding) to survive and persist due to long evolutionary coexistence with fire. In the African rim of the Western Mediterranean Basin, cork oak forest and pine plantation are the most frequently burnt woodlands. Both species have different strategies to respond fire: cork oak is a resprouter while pines are mostly seeders.

Aims

We have examined the hypothesis that pine plantations are less resilient in habitat structure (canopy, understory, diversity of vegetation strata) and plant composition than cork oak woodlands.

Methods

The habitat structure and plant species composition were measured in 30 burnt and 30 unburnt 700-m transects at 12 burnt sites from north-western Africa, where the two forest types can coexist. Habitat structure and plant species composition were compared between burnt and unburnt transects from cork oak and pine plantation woodlands with generalized linear mixed models and general linear models.

Results

The results showed significant interaction effect of fire and forest type, since cork oak forest was more resilient to fire than was pine plantation in habitat structure. By contrast, both forest types were resilient to fire in the composition of the plant communities, i.e., plant composition prior to fire did not change afterwards.

Conclusion

The higher structural resilience of cork oak forest compared to pine plantation is related to the resprouting and seeding strategies, respectively, of the dominant tree species. Differences in the responses to fire need to be considered in conservation planning for the maintenance of the Mediterranean biodiversity in a future scenario of changes in fire regime.
  相似文献   

17.
Fire histories contribute important information to contemporary fire planning, however, our knowledge is not comprehensive geographically. We evaluated the influence of topography on fire history patterns in two contrasting landscapes within the Santa Catalina Mountains of southeastern Arizona. Multiple fire-scarred trees from randomly selected 2-ha plots were used to develop plot composite mean fire intervals (PCMFIs) within the Butterfly Peak (BP) and Rose Canyon (RC) landscapes. BP is dominated by steep, northerly aspects and presence of potential fire spread barriers (exposed rock bluffs and scree slopes). RC is dominated by more gentle and southerly aspects with relatively few fire barriers. Within each landscape, PCMFIs did not differ significantly between aspect classes from A.D. 1748 to 1910 (BP: p = 0.73 and RC: p = 0.57). Pooled PCMFIs in the gentler RC landscape were, however, significantly shorter (p < 0.001) than in the steeper BP landscape. The frequency of relatively widespread fires (i.e., number of fire years when ≥2 plots scarred) was similar between landscapes, but fires in the gentler RC landscape were significantly larger (p = 0.033). The higher frequency of large fires (i.e., fires that burned >75% of the landscape) in RC resulted in more area burned over time and shorter fire intervals at individual plots. Conversely, smaller fires in the dissected BP landscape resulted in less area burned and longer periods between fires at individual plots. The different topographies in the two landscapes likely result in different wind intensities, fuel moistures, and fuel/vegetation types—and consequently, different historical fire spread patterns. Our conclusion is that fire history patterns are not influenced primarily by stand-scale topography, but rather by the topographic characteristics of the broader, surrounding landscape.  相似文献   

18.

• Introduction   

One current explanation for worldwide drought-induced tree mortality states that reduced photosynthesis and continued respiration lead to carbon depletion and eventually to carbon starvation.  相似文献   

19.

• Background   

Among forest management practices, forest tree species substitution influences biogeochemical cycles and soil interactions rapidly (decades) and significantly.  相似文献   

20.
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