Linking climate, annual growth and competition in a Mediterranean forest: Pinus pinea in the Spanish Northern Plateau

Climate Change Impacts on Pinus pinea L. Silvicultural System for Cone Production and Ways to Contour Those Impacts: A Review Complemented with Data from Permanent Plots

“…This objective can be achieved by maintaining a reduced or non-existent competition between individuals, by decreasing the density at stand installation and by periodically reducing density to incrementally increase the growth surface potentially available to each individual [15], through a thinning regime implementation [6], allowing a convenient ratio tree height/diameter, competition for water resources and damage risk by extraordinary events or by disturbances such as fire reduction.…”

“…Competition determines the limitation or regulation of the access of a subject tree to limited resources-light, water, or nutrients-due to neighboring effects [6]. Thinning forest stands regulates intra-specific and interspecific competition [6], increase the availability of water and nutrients for each remaining tree, thus promoting diameter at breast height [36,88,[97][98][99][100][101][102][103][104][105][106][107] and crown [88,106,108] growth. A higher diameter at breast height [36] or crown diameter [109] has a positive effect upon cone production.…”

“…However, such impact is substantially lower in umbrella pine stands for cone production, since stand densities and crown cover are low, the last often smaller than 50%. In order to reduce the impact on soil carbon by removing trees at the end of rotation, the next tree regeneration can be partly assured after the last thinning, using naturally regenerated trees as seedlings [6], so that the soil is never cleared of tree vegetation (a practice used for example at Leiria pine forest [167]). If needed, after the last thinning tree regeneration can be complemented with some planted trees.…”

“…Spanish natural stands are mostly located in four regions: Northern Plateau, Central Range, West Andalusia, and Catalonia, with most of the natural umbrella pine stands being managed for the production of both timber and pine nuts [5]. The first region is the most studied region in Spain concerning umbrella pine development and cone production [4,6]. It is characterized by an average altitude between 700 and 850 m and a Continental Mediterranean Climate, with very cold winters (average annual temperature 11.7-13.7 • C, minimum absolute temperature below −10 • C), often snowings, and very hot summers and very low rainfall (average annual rainfall: 440 mm, ranging from 220 to 620 mm), and summer drought (average rainfall of 54 mm between July-September) [6,7], which can negatively influence cone production even in the absence of inter-tree competition.…”

“…Other authors consider that winter and spring rainfall is crucial in explaining the variability in tree growth [12]. Calama et al [6] consider that the total rainfall occurring between October of the previous year to September of the current growth year, as well as the mean temperature in May and June, are the main climatic factors driving secondary growth in Pinus pinea, Mutke et al [13] found a highly significant correlation between June rainfall and shoot length and between flower bearing in the next year and current needle and branch diameter growth.…”