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Although the strong relationship between vegetation and climatic factors is widely accepted, other landscape composition and configuration characteristics could be significantly related with vegetation diversity patterns at different scales. Variation partitioning was conducted in order to analyse to what degree forest landscape structure, compared to other spatial and environmental factors, explained forest tree species richness in 278 UTM 10 9 10 km cells in the Mediterranean region of Catalonia (NE Spain). Tree species richness variation was decomposed through linear regression into three groups of explanatory variables: forest landscape (composition and configuration), environmental (topography and climate) and spatial variables. Additionally, the forest landscape characteristics which significantly contributed to explain richness variation were identified through a multiple regression model. About 60% of tree species richness variation was explained by the whole set of variables, while their joint effects explained nearly 28%. Forest landscape variables were those with a greater pure explanatory power for tree species richness (about 15% of total variation), much larger than the pure effect of environmental or spatial variables (about 2% each). Forest canopy cover, forest area and land cover diversity were the most significant composition variables in the regression model. Landscape configuration metrics had a minor effect on forest tree species richness, with the exception of some shape complexity indices, as indicators of land use intensity and edge effects. Our results highlight the importance of considering the forest landscape structure in order to understand the distribution of vegetation diversity in strongly human-modified regions like the Mediterranean.

Major changes in Mediterranean forests have occurred in recent decades, mainly as a result of the abandonment of traditional activities and population decline in rural areas. In this study, we analyzed the short-term (11-year) evolution of forests in the region of Catalonia (NE Spain) and the role of management, by comparing seven biodiversity indicators estimated from 7,664 plots from the Second and Third Spanish National Forest Inventory. We evaluated the changes in unmanaged and managed stands with different silvicultural treatments, and considered the effect of stand density and land ownership on these dynamics. We found a general naturalization and maturation of forests and an increase in all of the biodiversity indicators investigated during the study period, with the increments being greater in unmanaged than in managed plots. Some types of silvicultural treatments, such as selection cutting or thinning, were shown to be compatible with an increase in the analyzed indicators, and thus were more adequate for a multifunctional management that considers forest production together with the maintenance or improvement of the diversity of forest communities. The increases in shrub species richness and in the number of large-diameter trees after silvicultural treatments were more prominent in dense stands. Private lands presented greater short-term increases than public forests in all biodiversity indicators, except for large-diameter trees. From these results, we concluded that the application of silvicultural treatments can be a key tool to shape and maintain diverse and healthy forest structures in the context of socioeconomic and environmental changes in the Mediterranean region, which may induce potentially excessive densification and homogenization of some forest stands and landscapes.

There is an increasing need to develop efficient methods for characterising and monitoring forest biodiversity. A landscape scale approach and assessment can provide complementary and valuable information in this respect, by considering patterns and processes that operate at broad scales and influence different aspects of forest biodiversity. Here we analysed the relationships between six forest biodiversity indicators (related to the tree and shrub layers and estimated from a large set of field plots from the Third Spanish National Forest Inventory) and landscape structure, environmental and management variables at a 10 x 10 km scale in the region of Catalonia (NE Spain) through the variation partitioning method. The tree layer indicators were those most predictable from the set of explanatory variables considered, and up to 77.2 % of total variation was explained for tree species richness. Landscape variables were much more relevant to explain biodiversity patterns than environmental and spatial factors, and landscape composition outperformed the predictive capacity of configuration metrics. Management had a weak but positive effect on the tree layer indicators, while the amount of early successional forest was negatively associated to the tree layer indicators but positively to those of the shrub stratum. Our results highlight the need to (1) concentrate field sampling efforts in those indicators that are less predictable from the landscape scale, such as those related to rare species with a high conservation value, and to (2) incorporate landscape structure variables for forest biodiversity assessments in the Mediterranean, where a landscape management approach may be particularly suited to allow the adaptation of forest biodiversity to the ongoing landscape dynamics related to broad-scale processes such as rural land abandonment or climate change.Key words: forest biodiversity indicators, landscape configuration metrics, silvicultural treatments, variation partitioning. Resumen Efectos de la estructura del paisaje, variables ambientales, y gestión forestal en indicadores de biodiversidad estimados a partir de parcelas de inventario forestal en Cataluña (NE España)Dentro de la creciente necesidad de desarrollar métodos eficientes para caracterizar y monitorizar la biodiversidad forestal, una perspectiva de paisaje puede proporcionar información valiosa y complementaria al considerar patrones y procesos que operan en escalas amplias y que influyen en diferentes aspectos de la biodiversidad de nuestros bosques. Aquí se analizan las relaciones entre seis indicadores de biodiversidad forestal (relacionados con el estrato arbóreo y arbustivo y estimados a partir de un amplio conjunto de parcelas de campo del Tercer Inventario Forestal Nacional) y variables de estructura del paisaje, ambientales y de gestión a una escala de 10 x 10 km en Cataluña (NE España) mediante el método de partición de la variación. Los indicadores del estrato arbóreo resultaron ser los más predecibles mediante el conjunto de variab...

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