Large-scale determinants of diversity across Spanish forest habitats: accounting for model uncertainty in compositional and structural indicators

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2011Author
Martin Queller, Emilia Maria
Torras, O.
Solana, J.
Alberdi Asensi, Iciar
Saura Martínez de Toda, Santiago
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An integral understanding of forest biodiversity requires the exploration of the many aspects it comprises and of the numerous potential determinants of their distribution. The landscape ecological approach provides a necessary complement
to conventional local studies that focus on individual plots
or forest ownerships. However, most previous landscape studies
used equally-sized cells as units of analysis to identify the factors affecting forest biodiversity distribution. Stratification
of the analysis by habitats with a relatively homogeneous forest composition might be more adequate to capture the
underlying patterns associated to the formation and development of a particular ensemble of interacting forest species.
Here we used a landscape perspective in order to improve our understanding on the influence of large-scale explanatory
factors on forest biodiversity indicators in Spanish habitats, covering a wide latitudinal and altitudinal range. We considered
six forest biodiversity indicators estimated from more than 30,000 field plots in the Spanish national forest inventory,
distributed in 213 forest habitats over 16 Spanish provinces. We explored biodiversity response to various environmental
(climate and topography) and landscape configuration (fragmentation and shape complexity) variables through multiple
linear regression models (built and assessed through the Akaike Information Criterion). In particular, we took into account
the inherent model uncertainty when dealing with a complex and large set of variables, and considered different plausible
models and their probability of being the best candidate for the observed data. Our results showed that compositional
indicators (species richness and diversity) were mostly explained by environmental factors. Models for structural indicators
(standing deadwood and stand complexity) had the worst fits and selection uncertainties, but did show significant
associations with some configuration metrics. In general, biodiversity increased in habitats covering wider topographic
ranges and comprising forest patches with more complex shapes. Patterns in other relationships varied between indicators
(e.g. species richness vs. diversity), or even were opposed (trees vs. shrubs). Our study (1) allowed deepening the
understanding of biodiversity patterns in a large set of Spanish forest habitats and (2) highlighted the increasing complexity
of identifying common landscape conditions favouring forest biodiversity as the range of analysed biodiversity aspects
is widened beyond the more commonly assessed species richness indicators.
Is part of
Forest Systems, 2011, vol. 20, núm. 1, p. 151-164Collections
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