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Sterba H.,University of Natural Resources and Life Sciences, Vienna | Del Rio M.,Sistemas de Gestion | Del Rio M.,Sustainable Forest Management Research Institute UVa INIA | Brunner A.,Norwegian University of Life Sciences | Condes S.,Technical University of Madrid
Forest Systems

Aim of study: The aim of this paper is to compare differences in growth per hectare of species in pure and mixed stands as they result from different definitions of species proportions. Area of study: We used the data of the Spanish National Forest Inventory for Scots pine and beech mixtures in the province of Navarra and for Scots pine and Pyrenean oak mixtures in the Central mountain range and the North Iberic mountain range. Material and methods: Growth models were parameterized with the species growth related to its proportion as dependent variable, and dominant height, quadratic mean diameter, density, and species proportion as independent variables. As proportions we use once proportions by basal area or by stand density index and once these proportions considering the species specific maximum densities. Main results: In the pine-beech mixtures, where the maximum densities do not differ very much between species, the mixing effects are very similar, independent of species proportion definitions. In the pine – oak mixture, where the maximum densities in terms of basal area are very different, the equations using the proportions calculated without reference to the maximum densities, result in a distinct overestimation of the mixing effects on growth. Research highlights: When comparing growth per hectare of a species in a mixed stand with that of a pure stand, the species proportion must be described as a proportion by area considering the maximum density for the given species, wrong mixing effects could be introduced by inappropriate species proportion definitions. © 2014 Ministerio de Agricultura Pesca y Alimentacion. All rights reserved. Source

del Rio M.,Sistemas de Gestion | del Rio M.,Sustainable Forest Management Research Institute UVa INIA | Schutze G.,TU Munich | Pretzsch H.,TU Munich
Plant Biology

Facilitation, reduced competition or increased competition can arise in mixed stands and become essential to the performance of these stands when compared to pure stands. Facilitation and over-yielding are widely held to prevail on poor sites, whereas neutral interactions or competition, leading to under-yielding of mixed versus pure stands, can occur on fertile sites. While previous studies have focused on the spatial variation of mixing effects, we examine the temporal variation of facilitation and competition and its effect on growth. The study is based on tree ring measurement on cores from increment borings from 559 trees of Norway spruce (Picea abies [L.] Karst.), European beech (Fagus sylvatica [L.]) and sessile oak (Quercus petraea (Matt.) Liebl.) in southern Germany, half of which were in pure stands and half in adjacent mixed stands. Mean basal area growth indices were calculated from tree ring measurements for pure and mixed stands for every species and site. The temporal variation, with positive correlations between species-specific growth indices during periods of low growth and neutral or negative correlations during periods of high growth, is more distinct in mixed than in neighbouring pure stands. We provide evidence that years with low growth trigger over-yielding of trees in mixed as opposed to pure stands, while years with high growth lead to under-yielding. We discuss the relevance of the results in terms of advancing our understanding and modelling of mixed stands, extension of the stress gradient hypothesis, and the performance of mixed versus pure stands in the face of climate change. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands. Source

Sanchez-Gomez D.,Technical University of Madrid | Sanchez-Gomez D.,Sustainable Forest Management Research Institute UVa INIA | Majada J.,SERIDA | Alia R.,SERIDA | And 4 more authors.
Annals of Forest Science

Interpopulation variation in key functional traits of Pinus pinaster Ait. is well recognized. However, the relative importance of drought tolerance to explain this regional variation in the species remains elusive. Here, we raise the question whether water availability constitutes a likely driver of regional variation in biomass allocation, growth and morphological traits of ten populations that cover the distribution range of P. pinaster. We carried out an experiment where seedlings of five families per population were submitted to two contrasting watering treatments. The effects of water availability and population were significant for relative diameter and height growth rate, biomass allocation and number of lateral stems and dwarf shoots. Total dry mass significantly differed between watering treatments but it did not among populations. Populations could be clustered into four main groups. Root mass fraction explained most of the variation and significantly correlated to altitude but not to aridity.The geographical pattern of genetic variation found in morphology and biomass allocation did not translate into population differences in drought tolerance or phenotypic plasticity to water availability, indicating that water availability is not a likely driver of the regional variation observed in the studied traits of P. pinaster at the seedling stage. © 2010 INRA, EDP Sciences. Source

Del Rio M.,Japan Forestry and Forest Products Research Institute | Del Rio M.,Sustainable Forest Management Research Institute UVa INIA | Condes S.,Technical University of Madrid | Pretzsch H.,TU Munich
Forest Ecology and Management

In mixed stands, inter-specific competition can be lower than intra-specific competition when niche complementarity and/or facilitation between species prevail. These positive interactions can take place at belowground and/or aboveground levels. Belowground competition tends to be size symmetric while the aboveground competition is usually for light and almost always size-asymmetric. Interactions between forest tree species can be explored analyzing growth at tree level by comparing intra and inter-specific competition. At the same time, possible causes of niche complementarity can be inferred relating intra and inter-specific competition with the mode of competition, i.e. size-symmetric or size-asymmetric. The aim of this paper is to further our understanding of the interactions between species and to detect possible causes of competition reduction in mixed stands of beech (. Fagus sylvatica L.) with other species: pine-beech, oak-beech and fir-beech. To test whether species growth is better explained by size-symmetric and/or size-asymmetric competition, five different competition structures where included in basal area growth models fitted using data from the Spanish National Forest Inventory for the Pyrenees. These models considered either size-symmetry only (Reineke's stand density index, SDI), size-asymmetry only (SDI of large trees or SDI of small trees), or both combined. In order to assess the influence of the admixture, these indices were introduced in two different ways, one of which was to consider that trees of all species compete in a similar way, and the other was to split the stand density indices into intra- and inter-specific competition components. The results showed that in pine-beech mixtures, there is a slightly negative effect of beech on pine basal area growth while beech benefitted from the admixture of Scots pine this positive effect being greater as the proportion of pine trees in larger size classes increases. In oak-beech mixtures, beech growth was also positively influenced by the presence of oaks that were larger than the beech trees. The growth of oak, however, decreased when the proportion of beech in SDI increased, although the presence of beech in larger size classes promoted oak growth. Finally, in fir-beech mixtures, neither fir nor beech basal area growth were influenced by the presence of the other species. The results indicate that size-asymmetric is stronger than size-symmetric competition in these mixtures, highlighting the importance of light in competition. Positive species interactions in size-asymmetric competition involved a reduction of asymmetry in tree size-growth relationships. © 2014 Elsevier B.V. Source

Rodriguez-Garcia A.,Technical University of Madrid | Martin J.A.,Technical University of Madrid | Lopez R.,Technical University of Madrid | Mutke S.,Japan Forestry and Forest Products Research Institute | And 2 more authors.
Agricultural and Forest Meteorology

In the last five years, sharp increases in the price of natural resins, accompanied by technological advances directed toward mechanization, have made resin tapping a strategic activity for rural development and forest conservation. The resin industry demands more efficient tapping methods and forest management plans as a way to increase competitiveness in a global market. Understanding the effects of environmental conditions on resin yield, especially under the current scenario of climate change, is key to improving techniques and plans in the resin industry. This study aims to evaluate the intra- and inter-annual effects of climate conditions and soil water availability on resin yield in tapped Pinus pinaster stands. The individual resin yield of 26 tapped trees growing at two locations with different stand densities and soil characteristics was measured fortnightly during the tapping season (June to October) for four years. The study was complemented with an analysis of changes in xylem anatomy over the four years, with a focus on axial resin canal traits, including 12 non-tapped trees as controls. Intra-annual variation in resin yield was strongly correlated with temperature, solar radiation, potential evapotranspiration and water deficit. Inter-annual variation in resin yield and resin canal abundance were correlated with temperature and water deficit in spring, but above a certain threshold of cumulated water deficit in summer rainfall favored resin yield. Under adverse climate scenarios where resource optimization is desirable, a reduced tapping season during the warmest months (June-September) would be advisable, assuming a very small production loss. Similarly, in years with a rainy summer and/or dry spring, a slightly longer tapping season could be suggested, as resin yield increases after these events. © 2014 Elsevier B.V. Source

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