The results of the Forest Resources Assessment 2000 carried out by FAO are synthetically presented and discussed. The world forest coverage is estimated equal to 38.6 million km 2 . The comparison of the estimates from the period 1990-2000 with those from the period 1980-1990 points out a certain general deceleration of the rate of net deforestation, that currently involves around 9 million hectares every year. However, the annua1 loss of tropical forests is still very large, while temperate and borea1 forests are in expansion. Overall, FRA2000 produced a relevant effort to compensate the existing technical, institutional and financial constraints and shortcomings for monitoring the world forest resources. The need to increase the quality and the frequency of forest surveys, both at national and international levels, s t a stands as a major issue to cope with.

http://ojs.aisf.it/index.php/ifm/article/download/774/738

Valutazione delle risorse forestali a livello globale

Part I. Introduction: 1. Mediterranean-type climate (MTC) ecosystems and fire 2. Fire and the fire regime framework 3. Fire related plant traits Part II. Regional Patterns: 4. Fire in the Mediterranean basin 5. Fire in California 6. Fire in Chile 7. Fire in the Cape region of South Africa 8. Fire in southern Australia Part III. Comparative Ecology, Evolution and Management: 9. Fire-adaptive trait evolution 10. Fire and the origins of Mediterranean-type vegetation 11. Plant diversity and fire 12. Alien species and fire 13. Fire management of Mediterranean landscapes 14. Climate, fire and geology in the convergence of Mediterranean-type climate ecosystems References Index.

/pdf/fire-in-mediterranean-ecosystems-ecology-evolution-and-2wv8dufrqn.pdf

Fire in Mediterranean Ecosystems: Ecology, Evolution and Management

Combining NDVI and surface temperature for the estimation of live fuel moisture content in forest fire danger rating

In many parts of Europe, close-to-nature silviculture (CNS) has been widely advocated as being the best approach for managing forests to cope with future climate change. In this review, we identify and evaluate six principles for enhancing the adaptive capacity of European temperate forests in a changing climate: (1) increase tree species richness, (2) increase structural diversity, (3) maintain and increase genetic variation within tree species, (4) increase resistance of individual trees to biotic and abiotic stress, (5) replace high-risk stands and (6) keep average growing stocks low. We use these principles to examine how three CNS systems (single-tree selection, group selection and shelterwood) serve adaptation strategies. Many attributes of CNS can increase the adaptive capacity of European temperate forests to a changing climate. CNS promotes structural diversity and tree resistance to stressors, and growing stocks can be kept at low levels. However, some deficiencies exist in relation to the adaptation principles of increasing tree species richness, maintaining and increasing genetic variation, and replacing high-risk stands. To address these shortcomings, CNS should make increased use of a range of regeneration methods, in order to promote light-demanding tree species, non-native species and non-local provenances.

https://hal.archives-ouvertes.fr/hal-01143040/document

Suitability of close-to-nature silviculture for adapting temperate European forests to climate change

Aim

It has been suggested that on a global scale, fire activity changes along the productivity/aridity gradient following a humped relationship, i.e. the intermediate fire–productivity hypothesis. This relation should be driven by differing relative roles of the main fire drivers (weather and fuel) along the productivity gradient. However, the full intermediate fire–productivity model across all world ecosystems remains to be validated.



Location

The entire globe, excluding Antarctica.



Methods

To test the intermediate fire–productivity hypothesis, we use the world ecoregions as a spatial unit and, for each ecoregion, we compiled remotely sensed fire activity, climate, biomass and productivity information. The regression coefficient between monthly MODIS fire activity and monthly maximum temperature in each ecoregion was considered an indicator of the sensitivity of fire to high temperatures in the ecoregion. We used linear and generalized additive models to test for the linear and humped relationships.



Results

Fire occurs in most ecoregions. Fire activity peaked in tropical grasslands and savannas, and significantly decreased towards the extremes of the productivity gradient. Both the sensitivity of fire to high temperatures and above-ground biomass increased monotonically with productivity. In other words, fire activity in low-productivity ecosystems is not driven by warm periods and is limited by low biomass; in contrast, in high-productivity ecosystems fire is more sensitive to high temperatures, and in these ecosystems, the available biomass for fires is high.



Main conclusion

The results support the intermediate fire–productivity model on a global scale and suggest that climatic warming may affect fire activity differently depending on the productivity of the region. Fire regimes in productive regions are vulnerable to warming (drought-driven fire regime changes), while in low-productivity regions fire activity is more vulnerable to fuel changes (fuel-driven fire regime changes).

/pdf/the-global-fire-productivity-relationship-532f9fao6o.pdf

The global fire–productivity relationship

The time-to-ignition of various dominant Mediterranean forest fuels was measured during laboratory tests, in order to develop a relative flammability classification and determine the moisture of extinction of these fuels. The tests were performed with an ignition apparatus manufactured according to the ISO standards (ISO 5657-1986E) and under a wide gradient of fuel moisture contents, ranging from air-dry to fresh foliage. Moisture content was the single most significant factor that affected fuel flammability. Regression models were developed between the time-to-ignition and the moisture content values of all the fuels tested, and subsequently, were used for the relative flammability ranking of these fuels. Fuel moisture of extinction was assessed to have a threshold value ranging from 40% to more than 140% o.d.w. for the species tested. The flammability ranking of natural fuels can be useful in fuel hazard assessment and fire danger rating, thus facilitating the judicial fire management planning in wildlands and at the rural-urban interface.

Flammability Assessment of Mediterranean Forest Fuels

The Fire Weather Index module of the Canadian Forest Fire Danger Rating System (CFFDRS) was evaluated during two consecutive fire seasons in the Mediterranean environment of Crete, Greece. The Duff Moisture Code (DMC), the Drought Code (DC), the Buildup Index (BUI) and the Fire Weather Index (FWI) were highly correlated to fire occurrence but only moderately to area burned. Logistic regression was applied in order to classify the FWI values into fire danger classes appropriate for the Mediterranean environments, as follows: 0–38 Low, 39–48 Moderate, 49–59 High, > 60 Extreme. The new classification was necessary because the existing Canadian fire danger classes were found inapt for the dry and extremely fire prone eastern Mediterranean climate of Crete. After the modification, the fluctuation of the FWI values predicted more successfully the days of high fire risk, as proved by the actual fire occurrence. High correlation was found between measured litter (L layer) moisture values and those predicted by the Fine Fuel Moisture Code (FFMC). The use of an equilibrium duff moisture content value lower than 20% in Mediterranean environments, would probably improve the Duff Moisture Code (DMC) predictions. The Drought Code (DC) was poorly correlated to the upper soil moisture content. Overall, the FWI demonstrated several aptitudes related to its potential use as a meteorological fire danger rating index in Mediterranean regions. However, long–term studies are necessary to determine the precise range of each fire danger class according to fire occurrence data. Copyright © 2010 Royal Meteorological Society

Evaluation of the Canadian fire weather index system in an eastern Mediterranean environment

The Mediterranean vegetation types of Greece were classified into typical fuel models by measuring the following fuel parameters in 181 representative natural fuel complexes: 1-h, 10-h, 100-h and 1000-h fuel loads; foliage load; litter load and depth; total fuel load; average height and soil cover of the herbaceous, small shrub (up to 0.5 m) and tall shrub (0.5-3.0 m) vegetation layers. The data set was statistically analysed by a two-stage clustering procedure that produced seven distinct fuel models: two for evergreen-sclerophyllous shrublands (maquis), one for kermes oak shrublands, two for phrygana, one for grasslands and one for the litter layer of Mediterranean pine forests. The indicative range (upper and lower limit) of potential fire behavior for every fuel model was calculated with the BEHAVE fire behavior prediction system, using as inputs the specific fuel parameter values of every model. The shrubland fuel models resulted in fires with high intensity and rate of spread, while the phrygana and grassland models in fast fires of medium to low intensity. The litter layer of the pine forests provided the least severe burning conditions.

Mediterranean fuel models and potential fire behaviour in Greece.

An increasing trend and a statistically significant positive correlation between wildfire occurrence, area burned and drought (as expressed by the Standardized Precipitation Index, SPI) have been observed all over Greece, during the period 1961–1997. In the more humid and colder regions (Northern and Western Greece) the number of fires and area burned were positively correlated to both summer (SPI6_October) and annual drought (SPI12_September), whereas in the relatively more dry and hot regions (Southern and Central Greece) the number of fires and area burned were correlated only to summer drought. In 1978, Greece entered a period of prolonged drought, possibly as a result of the global climatic change. Data analysis of the period 1978–1997 revealed a statistically significant increase in the mean annual number of fires, the area burned and the summer and annual drought episodes in the relatively more humid and colder regions (Northern and Western) of Greece (which in the past were characterized by less fires and area burned) compared to the more dry and hot regions (Southern and Eastern Greece), which always presented high fire activity. Additionally, analyzing the two sub-periods (1961–1977, 1978–1997) separately, drought was significantly correlated only to fire occurrence during the years 1961–1977, whereas during 1978–1997 drought was significantly correlated mainly to area burned. It became obvious that drought episodes, although they are not solely responsible for fire occurrence and area burned, they exert an increasingly significant impact on wildfire activity in Greece.

Impact of drought on wildland fires in Greece: implications of climatic change?

Canopy fuel characteristics that influence the initiation and spread of crown fires were measured in representative Aleppo pine (Pinus halepensis Mill.) stands in Greece. Vertical distribution profiles of canopy fuel load, canopy base height and canopy bulk density are presented. Aleppo pine canopy fuels are characterized by low canopy base height (3.0–6.5 m), while available canopy fuel load (0.96–1.80 kg/m2) and canopy bulk density (0.09–0.22 kg/m3) values are similar to other conifers worldwide. Crown fire behavior (probability of crown fire initiation, crown fire type, rate of spread, fireline intensity and flame length) in Aleppo pine stands with various understory fuel types was simulated with the most updated crown fire models. The probability of crown fire initiation was high even under moderate burning conditions, mainly due to the low canopy base height and the heavy surface fuel load. Passive crown fires resulted mostly in uneven aged stands, while even aged stands gave high intensity active crown fires. Assessment of canopy fuel characteristics and potential crown fire behavior can be useful in fuel management and fire suppression planning.

/pdf/canopy-fuel-characteristics-and-potential-crown-fire-1bqk248w49.pdf

A. P. Dimitrakopoulos

Papers

Flammability Assessment of Mediterranean Forest Fuels

Evaluation of the Canadian fire weather index system in an eastern Mediterranean environment

Mediterranean fuel models and potential fire behaviour in Greece.

Impact of drought on wildland fires in Greece: implications of climatic change?

Canopy fuel characteristics and potential crown fire behavior in Aleppo pine ( Pinus halepensis Mill.) forests