Structure and Regeneration Patterns of Pinus nigra subsp. salzmannii Natural Forests: A Basic Knowledge for Adaptive Management in a Changing Climate

Abstract

Abstract:Since climate change projections contain many uncertainties and are normally unable to predict the direction and magnitude of change at the small scale needed by forest managers, some understanding about the functioning of the target forest should be obtained before a robust management strategy can be applied. Structure and regeneration patterns are related to key ecosystem processes which, on the other hand, can be modified by silvicultural treatments. In this research, the structure and recruitment dynamics of two stands with different histories of management were investigated in the southern limit of the range of Pinus nigra subsp. salzmannii (Southeast Spain). We described forest structure and facilitation effects by forest canopies and nurse shrubs, and quantified the processes affecting each stage of regeneration (dispersed seed, first year seedling and second year seedling) in different microhabitats. Forest structure was more complex in the stand scarcely influenced by human activities. Juniperus communis shrubs seemed to facilitate the establishment of tree saplings. Most seedlings died of desiccation during their first summer. At best, 190 out of 10,000 emerged seedlings survived the first summer. In light of these results, the possibilities of applying close-to-nature forestry in the study forests and other aspects of silviculture under a frame of adaptive forest management are discussed. OPEN ACCESSForests 2011, 2 1014

Large-Scale Regeneration Patterns of Pinus nigra Subsp. salzmannii: Poor Evidence of Increasing Facilitation Across a Drought Gradient

“…Other studies have mentioned precipitation as a factor positively correlated with significant increases in recruitment success [42,50]. The regeneration pattern observed at a regional scale in this study is then consistent with results from small-scale studies, which identified drought as the main cause of seedling mortality in rock-free P. nigra stands [6,9,27]. Consequently, summer drought might be the major limiting factor of recruitment throughout the species distribution area.…”

“…These findings suggest that cover from the tree canopy is a large-scale habitat condition of the P. nigra regeneration niche, similar to climate or soil conditions. The observation that young P. nigra trees benefit from the special abiotic conditions beneath tree canopies suggests the existence of facilitative interactions between seedlings and canopy trees [6]. Indeed, Spanish foresters have been largely aware of the shade tolerance of P. nigra seedlings, and of the importance of tree cover for P. nigra regeneration [51,53], but this study offers insights into the nature of such facilitative interaction.…”

“…Seedlings are highly vulnerable to drought stress, and Mediterranean-type ecosystems are characterized by a sharp seasonality of rainfall and temperature, with hot-dry summers [4]. Consequently, seedling mortality is found to be exacerbated both during the summer season and in open areas, where high irradiance increases evaporative demands and further reduces soil-water availability [5][6][7][8]. Studies focused on the recruitment dynamics of Mediterranean tree species have found increasing seedling mortality during the summer, compared with other periods of the year, and in open areas, compared with sites located under the canopy of woody plants [9,10].…”

“…salzmannii Dunal (Franco) (P. nigra hereafter) is a Mediterranean mountain pine, commonly harvested [28], and its forests are included in the European Union list of natural habitats requiring specific conservation measures. Several small-scale studies have shown that P. nigra regeneration frequently fails under natural conditions, particularly in open microhabitats, but it is unknown whether such lack of regeneration is a common pattern at the regional scale [6,9,27]. The species is widely distributed along the eastern mountain ranges of the Iberian Peninsula.…”

Monitoring Post Disturbance Forest Regeneration with Hierarchical Object-Based Image Analysis

“…Climate change is impacting post-disturbance regeneration rates [52]. The method demonstrated here captures the spatial patterns of post-disturbance regeneration of forests, a basic knowledge parameters for adaptive management to landscape stewardship under climate change [53].…”