Thinning intensity and growth response in SW-European Scots pine stands

Abstract

-The effect of different thinning intensities on growth and yield was studied in Pinus sylvestris L. stands at the south-western limit of its distribution area (Central Spain), using five long-term thinning trials. Data were analysed collectively considering several factors (trial, block, plot and period) as random effects. Total volume and volume increment decreased with thinning intensity, this loss being more significant in the case of moderate and heavy thinning. No difference was found among treatments for total basal area or the increment in basal area. The results revealed an optimum basal area (Assmann's definition) between 85 and 100% of the basal area in unthinned plots. Volume growth loss associated with heavy thinnings (reduction of 18% in volume increment) was smaller than that reported in Central and Northern European regions (greater than 25%). Height increment was not influenced by thinning, whereas dominant and quadratic mean diameter increments increased with the thinning intensity. The response of diameter growth to thinning was greater at younger ages (less than 50 y) and in medium-sized trees.thinning / Pinus sylvestris / growth / Mediterranean area / long-term trial Résumé -Intensité d'éclaircie et croissance dans des peuplements de pin sylvestre du sud ouest de l'Europe. L'effet de différentes intensités d'éclaircie sur la croissance et la production de peuplements de Pinus sylvestris L. a été étudié à la limite sud-ouest de sa zone de répartition (centre de l'Espagne), à partir de cinq essais d'éclaircie suivis à long terme. Les données ont été analysées collectivement en prenant en compte différents facteurs (essai, bloc, placeau et période) comme facteurs aléatoires. Le volume total et l'accroissement en volume diminuaient avec l'intensité d'éclaircie, cette perte devenant plus significative dans le cas d'éclaircies modérées et fortes. Aucune différence n'a été trouvée entre traitements pour la surface terrière totale ni pour sa vitesse d'accroissement. Les résultats révèlent un optimum de surface terrière (selon la définition d'Assmann) compris entre 85-100 % de la surface terrière des placeaux non éclaircis. Les pertes de croissance en volume associées aux éclaircies fortes (réduction de 18 %) étaient plus faibles que celles qui sont rapportées pour les régions du Centre et du Nord de l'Europe (supérieures à 25 %). L'accroissement en hauteur n'a pas été influencé par l'éclaircie alors que l'accroissement quadratique moyen en diamètre augmentait avec l'intensité d'éclaircie. La réponse en termes d'accroissement en diamètre à l'éclaircie a été plus forte pour les jeunes arbres (moins de 50 ans) et les arbres de taille moyenne.éclaircie / Pinus sylvestris / croissance / région méditerranéenne / essai à long terme

Modeling growth and yield of loblolly pinestands under intensive management

“…This can be explained by the fact that, in order to obtain a remaining stand of 400 trees per hectare, a greater amount of basal area must be removed from the higher productivity stands due to the larger size of the trees. Even though the basal area values for the thinned areas are close to those for the unthinned ones, the former most likely will not pass the latter, confirming the results obtained in several thinning studies carried out by Hasenauer et al (1997), Simard et al (2004), Río et al (2008), andSkovsgaard (2009). This statement can only be confirmed after the study plots undergo the first commercial thinning operation, allowing the modeling of post-thinning growth.…”

Influence of thinning intensity and canopy type on Scots pine stand and growth dynamics in a mixed managed forest

“…Primicia et al (2013) also found a weak and temporary effect of the first thinning on the tree ring width of dominant and codominant pines in the same study site. Although thinning from below in Scots pine stands appears to particularly enhance the growth of intermediate trees (Río et al, 2008), we observed that the biggest trees (DBH comprised between Q 50 and Q 100 ) were the most responsive ones to the first thinning. In the study site, the initial stand structure of Scots pine was greatly variable among plots (lower pine density with higher quadratic mean diameter, higher tree and stand volume in unthinned than in thinned plots).…”

“…In the thinned plots, the yield reduction by thinning is counteracted by the enhancement of individual tree growth, resulting in lower stand density but bigger tree size. However, a reduction in either stand or merchantable volume and stand growth has been frequently observed following moderate to very heavy thinning, although it was also absent after light thinning or in control plots in other Scots pine stands few years after thinning Mäkinen & Isomäki, 2004;Mäkinen et al, 2005;Río et al, 2008;Crecente-Campo et al, 2009). …”

“…Several studies have been focused on the effects of thinning on tree growth in Scots pine pure stands (e.g. Montero et al, 2001;Mäkinen & Isomäki, 2004;Mäkinen et al, 2005;Río et al, 2008;Crecente-Campo et al, 2009;Novak et al, 2011), but just few studies have tackled the same issue in mixed woodlands (e.g. Primicia et al, 2013).…”

Forest management and carbon sequestration in the Mediterranean region: A review

“…nc: off-site carbon stock was not reported by the authors 2004; Río et al, 2008b) and of carbon stocks in the Mediterranean region (Bravo-Oviedo et al, 2015;RuizPeinado et al, 2016).…”