Climate change forecasts increase the susceptibility of forest due to longer drier seasons. The adaptive management protocols have highlighted the reduction of the forest densification to improve their vulnerability to extreme climate events (i.g. drought). One of this sensitive woody species to climate change is the Abies pinsapo, a relic conifer tree endemic from the southern Spain. Previous works have shown changes in their trends because of the climate change action, being carried out experimental thinning management in their lowest distribution limit, in Sierra de las Nieves Natural Park (Malaga). Our objective is to evaluate the water improvements of thinned trees in terms of light availability by means of a shading treatment in those thinned trees. To do that we have evaluated the synergic effect of ecophysiology, metabolomics and transcriptomics in control, thinning and thinning+shading plots in wet and dry seasons for two years. The results showed strong differences between summer and spring seasons at the three studied levels. The water deficit shows a greater influence than light exposure in the ecophysiology and metabolomics tree response. And the transcriptomics suggested an improvement of thinned trees when light exposure was reduced. Our results support the necessity of adaptive forest management in order to improve the conservation status of A. pinsapo forest. The combination of different levels of tree response is paramount to understand and predict the tree physiology under water and light stress conditions.
Overall design: The study was carried out in natural stands of Abies pinsapo Boiss., a drought-sensitive fir, located near the lower elevation limit of the altitudinal species distribution range (Sierra de las Nieves Natural Park; 36°43′N, 4°57′W, 1200 m, aspect NW, slope ca. 40%). Abies pinsapo forests in the study area were subjected to intense grazing and logging by the inhabitants around the middle 20th century. During the second half of the 20th century until present times, these forests were protected whilst they underwent the abandonment of traditional uses. The suppression of the perturbation regime enhanced a regeneration process, which ended up in dense stands. An experimental thinning management was designed and performed in October 2004, attempting to enhance the stand structure diversity by reducing tree competition, increasing the equitability of size classes and randomizing tree spatial pattern. As our objective was to analyse the availability of light and water resources to A. pinsapo in this managed stands, we designed three field-treatments where we could study the effect of both factors separately: (i) plots with reduced tree density and therefore decreased intra-specific competition for water and light: “Thinning” treatment; (ii) trees in adjacent forest stands where such adaptive management practices were not applied (high competition for both light and water; “Control” treatment), and (iii) trees in the thinned plot which were covered by a mesh to simulate a light environment similar to that in “Control” plots (high competition for light+low competition for water; “Thinning + Shading” treatment). In this way, it has been possible to experimentally evaluate the improvement in the light environment perceived by remaining trees in thinned plots. We selected three circular plots with 100 m2 surface per treatment where all trees were identified (tree species; tree status: alive, dead, stump), tagged and mapped, and their DBH (diameter at breast height) was measured.
Less...