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The aim of the study was to assess the effects of competition at both stand and tree levels on climate tree-growth relationships of 414 Abies alba and 243 Fagus sylvatica trees growing in 2 contrasting ecological conditions (north- and south-facing) under mountainous continental climate (mean altitude: 886 m). Stand level competition was considered through three stand basal area (SBA) modalities (Low: 32 m(2)/ha, Medium: 41 and High: 49) while tree level competition was assessed through three social statuses (SST, Dominant, Codominant and Suppressed trees). A strong specific response to climate was pointed out with different key periods; growth of Abies being mainly driven by previous and current late summer temperatures, while that of Fagus was controlled by April and June ones. No obvious difference between facing sides was evidenced. Competition at stand level prevailed on competition at tree level. In Low and Medium SBA, trees exhibited similar responses to climate whatever their social statuses. On the opposite, sensitivity to summer drought increased with dominancy in high SBA. Inter-specific differences and consequences for forest management are discussed. (C) 2014 Elsevier B.V. All rights reserved.

We investigated whether timing and rate of growth are related to the life strategies and fitness of three conifer species. Intraannual dynamics of wood formation, shoot elongation and needle phenology were monitored over 3 years in five Norway spruces (Picea abies (L.) Karst.), five Scots pines ( Pinus sylvestris L.) and five silver firs ( Abies alba Mill.) grown intermixed. For the three species, the growing season (delimited by cambial activity onset and cessation) lasted about 4 months, while the whole process of wood formation lasted 5–6 months. Needle unfolding and shoot elongation followed the onset of cambial activity and lasted only one-third of the season. Pines exhibited an ‘extensive strategy’ of cambial activity, with long durations but low growth rates, while firs and spruces adopted an ‘intensive strategy’ with shorter durations but higher growth rates. We estimated that about 75% of the annual radial increment variability was attributable to the rate of cell production, and only 25% to its duration. Cambial activity rates culminated at the same time for the three species, whereas shoot elongation reached its maximal rate earlier in pines. Results show that species-specific life strategies are recognizable through func tional traits of intra-annual growth dynamics. The opposition between Scots pine extensive strategy and silver fir and Norway spruce intensive strategy supports the theory that pioneer species are greater resource expenders and develop riskier life strategies to capture resources, while shade-tolerant species utilize resources more efficiently and develop safer life strate gies. Despite different strategies, synchronicity of the maximal rates of cambial activity suggests a strong functional convergence between co-existing conifer species, resulting in head-on competition for resources.

Analysis of the selection cutting treatments applied We describe the structure of uneven-aged silver-fir stands with a growing stock in which large diameter classes initially had an excessive representation. Silvicultural treatments were applied to correct diameter distribution trends towards a regular structure. The initial state of the forest revealed a high density in mature individuals, but no regeneration problems were detected, neither mechanical stability difficulties, in any of the stands. The selective cutting treatments concentrated mainly on trees over the 30-cm diameter class, but all diameter classes were treated. As a result of these silvicultural management actions the polewood layer was released from vertical competition. Yet, stand structure is far from irregular, which precludes to consider these stands in an equilibrium state. Se describe, en una zona de la vertiente norte de los Pirineos españoles, la estructura dasocrática de rodales irregulares de abeto excesivamente capitalizados en existencias volumétricas, así como la naturaleza de las intervenciones de entresaca que se les aplican al objeto de contrarrestar la tendencia hacia una indeseable uniformidad de la masa. La situación inicial revela una elevada espesura, con importantes excedentes de individuos pertenecientes a las clases diamétricas de madera gruesa, y que conduce a formas selvícolas tipológicas en avanzado proceso de regularización. Empero, la estabilidad mecánica de los pies se manifiesta alejada de sus umbrales críticos en todos los estratos, y la capacidad de regeneración del sistema resulta aceptable. El tratamiento de entresaca realizado, cuya severidad se centró fundamentalmente sobre los pies de diámetro superior a 30 cm, mantiene todavía una situación de espesura excesiva que impide la adscripción de los rodales a estructuras equilibradas, pero ha permitido la liberación de la competencia vertical de los pies en edad de latizal.