Human impacts drive forest structure and diversity. Insights from Mediterranean mountain forest dominated by Abies pinsapo (Boiss.)

Abstract

Environmental factors and land-use are likely interacting to drive forest structure and species diversity, making it difficult to disentangle their separate impacts. Both components influence the resilience and stability of mountain forests in the Mediterranean Basin, since secular land-use has shaped stands structure and forests dynamics are constrained to the environment. Approaches covering environmental factors and contrasting land-uses are still needed to understand their implications on forest dynamics. We investigated patterns of environmental variables, stand structure and biodiversity in forest dominated by Abies pinsapo for 61 stands over their whole range. In addition, since land-use by local inhabitant could be a key factor, logging intensity was quantified by stumps basal area and recent land-use history was investigated. Partial redundancy analysis (pRDA) was conducted to assess to which degree the structural attributes are related to environmental characteristics and/or the land-use in the main A. pinsapo forests. Environmental characteristics accounted for 13% of the total variance, while the contrasting land-use (Spain vs. Morocco) and the stumps basal area, as indicator of human logging, accounted for 23% of the total variance. Trees species diversity was near 5 times higher in Moroccan stands than in stands from south Spain. According to recent human logging, Spanish stands have been strictly protected, but Moroccan stands showed widespread axe-logging by local inhabitant over the smaller tree sizes. Our results suggest that the preservation of a minor perturbation regimen by local populations enhance and help to preserve the whole biodiversity of this relict habitat.

Spatial Distribution and Volume of Dead Wood in Unmanaged Caspian Beech (Fagus orientalis) Forests from Northern Iran

“…Recently, uneven-aged forest stands have received increasing attention [1][2][3][4]. Unmanaged forests are remnants of natural ecosystems, providing a basis for nature-based forest management, i.e., to use natural forest ecosystems as a model and to guide forest management [2].…”

Changes in the structure and composition of two Pinus nigra subsp. salzmannii forests over a century of different silvicultural treatments

“…Indeed, the relative contribution of SMA almost doubled the contribution of the considered environmental variables in explaining structural variability. Other researchers have also supported the potential of land-use to profoundly change the structure of Mediterranean forests (Linares et al, 2010;Plieninger et al, 2003). These findings were expected, because structure is the outcome of a demographic process and, whilst silvicultural treatments easily determine the mortality rate of tree populations, their influence on seedling establishment is less clear in Mediterranean forests, due to the overwhelming impact of summer drought, and not light availability, on plant recruitment (Tíscar, 2007).…”

Regeneration of Abies pinsapo within gaps created by Heterobasidion annosum-induced tree mortality in southern Spain

“…The Weibull shape parameters reported for A. pinsapo showed an exponential distribution in gaps and a positively skewed distribution in closed-canopy sites. This indicates the existence of abundant young individuals and very good regeneration status, particularly within gaps (Linares & Carreira 2009, Linares et al 2010b, 2011b. The forest structure of A. pinsapo forests resembles that of uneven-age or multicohort-disturbed forests, whose regeneration comes in pulses when favorable climatic conditions occur or when regeneration sites and prolific seed crops are available (Oliver & Larson 1996).…”