New article: Land-use changes as drivers of mountain pine expansion

Aitor Améztegui and Lluís Coll, from FiDBosc, recently got a paper published in Global Ecology and Biogeography about the patterns and drivers of mountain pine expansion in the Pyrenees.

The aim of this study was to assess the spatial patterns of forest expansion (encroachment and densification) for Mountain pine (Pinus uncinata Ram.) during the last 50 years in a whole mountain-range scale by the study of different topographic and socio-economic potential drivers in the current global-change context. Forest cover was obtained by image reclassification of more than 200 pairs of aerial photographs taken in 1956 and 2006, covering the whole distributional area of Mountain pine in the Catalan Pyrenees (NE Spain). This represents more than 80 municipalities and a total area of 6,018 km2. Encroachment and densification were determined according to changes in forest cover, and were expressed as binary variables on a 150x150m cell-size grid. We then used logistic regression to analyze the effects of several topographic and socio-economic variables on forest expansion.

In the period analyzed, Mountain pine increased its surface coverage by 8,898 hectares (an increase of more than 16%). Mean canopy cover rose from 31.0% in 1956 to 55.6% in 2006. Most of the expansion was found on north-facing slopes and at low altitudes. Socio-economic factors arose as major factors of Mountain pine expansion, as encroachment rates were higher at municipalities with greater population losses or weaker primary sector development.

Therefore, the spatial patterns of Mountain pine expansion highly matched the main patterns of land-use change in the Pyrenees, suggesting that land-use changes have played a more determinant role than climate in driving forest dynamics at landscape scale over the period studied. Further studies on forest expansion at regional scale should incorporate patterns of land-use changes to correctly interpret drivers of forest encroachment and densification.

Améztegui, A; Brotons, L; Coll, L. (2010). Land-use changes as major drivers of mountain pine (Pinus uncinata Ram.) expansion in the Pyrenees. Global Ecology and Biogeography 19 (5) : 632-641.

Celebradas las primeras jornadas técnicas del proyecto Interreg UNCI'PLUS

En el marco del proyecto europeo Interreg UNCI'PLUS, en cuya parte I se elaborará la "Guía de gestión del pino negro en los Pirineos orientales", se han celebrado recientemente dos jornadas de campo para el debate entre técnicos y especialistas sobre diferentes aspectos relativos a la gestión de las masas forestales dominadas por dicha especie. Los organizadores y principales entidades implicadas en el proyecto (Centre Tecnològic Forestal de Catalunya, Departament de Medi Ambient i Habitatge, Office National des Forêts, Parc Naturel Régional des Pyrénées Catalanes, Centre Régional de la Propriété Forestière y GEIE Forespir) debarieron durante estas dos jornadas tanto sobre la gestión de masas de vocación productora como de las de vocación silvopastoral, así como de lo relativo a la conservación de los recursos genéticos y paisajísticos en la gestión de los bosques de pino negro.

Más información en la nueva web del proyecto UNCI'PLUS

New article: Predicting understory maximum shrubs cover in Mediterranean forests

Predicting understory maximum shrubs cover using altitude and overstory basal area in different Mediterranean forests

In some areas of the Mediterranean basin where the understory stratum represents a critical fire hazard, managing the canopy cover to control the understory shrubby vegetation is an ecological alternative to the current mechanical management techniques. In this study, we determine the relationship between the overstory basal area and the cover of the understory shrubby vegetation for different dominant canopy species (Pinaceae and Fagaceae species) along a wide altitudinal gradient in the province of Catalonia (Spain). Analyses were conducted using data from the Spanish National Forest Inventory. At the regional scale, when all stands are analysed together, a strong negative relationship between mean shrub cover and site elevation was found. Among the Pinaceae species, we found fairly good relationships between stand basal area and the maximum development of the shrub stratum for species located at intermediate elevations (Pinus nigra, Pinus sylvestris). However, at the extremes of the elevation-climatic gradient (Pinus halepensis and Pinus uncinata stands), stand basal area explained very little of the shrub cover variation probably because microsite and topographic factors override its effect. Among the Fagaceae species, a negative relationship between basal area and the maximum development of the shrub stratum was found in Quercus humilis and Fagus sylvatica dominated stands but not in Quercus ilex. This can be due to the particular canopy structure and management history of Q. ilex stands. In conclusion, our study revealed a marked effect of the tree layer composition and the environment on the relationship between the development of the understory and overstory tree structure. More fine-grained studies are needed to provide forest managers with more detailed information about the relationship between these two forest strata.

Coll, L., Gonzalez-Olabarria, J.R. Mola-Yudego, B., Pukkala, T., Messier C. (2010) Predicting understory maximum shrubs cover using altitude and overstory basal area in different Mediterranean forests. European Journal of Forest Research. DOI 10.1007/s10342-010-0395-y.