González-Sanchis, M., Ruiz-Pérez, G., Del Campo, A. D., Garcia-Prats, A., Francés, F., & Lull, C. (2019). Managing low productive forests at catchment scale: considering water, biomass and fire risk to achieve economic feasibility. Journal of environmental management, 231, 653-665.

Semi-arid forests are water limited environments considered as low-productive. As a result, these forests usually end up unmanaged and abandoned, with the subsequent wild fire risk increasing, water yield decreasing and a general diminishing of the forest resilience. Hydrological-oriented silviculture could be a useful alternative that increases management possibilities by combining forest productivity and water yield. However, the slight water yield increase after forest management together with the low forest productivity, could make this option insufficient for semi-arid forests, and other goods and services should be included and quantified. In this sense, the present study analyzes to what extent semi-arid forest management for water yield results effective and profitable at catchment scale, and how does it improve when it is combined with other benefits such as biomass production and fire risk diminishing. To that end, the effects of forest management of semi-arid Aleppo pine post-fire regeneration stands are analyzed in terms of water yield (TETIS-VEG model), fire risk (KDBY index and FARSITE) and biomass production, at catchment scale. Regarding to water yield, the results confirmed the slight effect of forest management on its increase (average increase of 0.27 ± 0.29 mm yr−1), at the same time that highlighted the role of the upper catchment area as an important water contributor. The management produced 4161.6 Mg of biomass, and decreased in 27±17% and 25.6 ± 14.1% the fire risk and fire propagation, respectively. Finally, a simple economic estimation of the management profitability is carried out by means of comparing the Benefit/Cost ratio of the managed and unmanaged scenarios. Both scenarios were always above the unity when just considering water as benefit, although the unmanaged scenario produced a higher ratio, as no management costs are expended. Contrarily, when wildfire was also included into the evaluation, the situation is overturned for wildfires equal or higher than 1.5 day duration, where the forest management is shown as the most convenient alternative.

Del Campo, A. D., González-Sanchis, M., Molina, A. J., García-Prats, A., Ceacero, C. J., & Bautista, I. (2019). Effectiveness of water-oriented thinning in two semiarid forests: The redistribution of increased net rainfall into soil water, drainage and runoff. Forest Ecology and Management, 438, 163-175.

Water is the key element that modulates the provision of goods and services together with global/climate stressors affecting semiarid forests. In this sense, there is a need to improve the understanding and quantification of forest and water relationships as affected by forest management. This work addresses this issue by comparing net rainfall (Pn) redistribution into different belowground hydrological processes (BHP) in two forest types after a thinning treatment: a holm oak coppice (HU) and a post-fire Aleppo pine regeneration (CAL). The relative contribution (RI) of forest structure, antecedent soil moisture (θst), rainfall and meteorological conditions on the BHP was assessed through boosted regression trees models. In both sites, the RI of the forest structure itself was limited (<10%). However, θst, which clearly increased significantly with thinning, received an average RI of 29%. Surface and subsurface lateral flows showed values <1% of gross rainfall (Pg) in either site and were not significantly affected by thinning. On the other hand, soil moisture and drainage were affected by the thinning treatment, although with different extent depending on the site: in the drier site (CAL), the increased Pn in the thinning was mainly allocated into increased soil water content, with very limited improvement in drainage (<10 mm/year); in contrast, in the wetter continental site of HU, drainage to deeper soil layers was the most remarkable effect of thinning (50 mm/year higher than in control), given the higher θst and hence the lower soil water storage available. Thinning also improved the response of BHP during drought, making these processes more elastic and less vulnerable to climatic extremes. The results presented here complement those previously reported on rainfall partitioning in these sites and all together provide a comprehensive understanding of the short-term effect (3–4 years) of water-oriented silviculture in Quercus ilex and Pinus halepensis low-biomass semiarid forests. Questions such as the long-term effects of thinning remain open for these ecosystems.

Del Campo, A. D., Segura-Orenga, G., Ceacero, C. J., González-Sanchis, M., Molina, A. J., Reyna, S., & Hermoso, J. (2020). Reforesting drylands under novel climates with extreme drought filters: The importance of trait-based species selection. Forest Ecology and Management, 467, 118156.

Having regard to the substantial world-scale forest restoration needs, the efforts must be done efficiently, which necessarily forces to consider the adaptation of new forests to the extremes arising from climate change. In this context, species selection strategies should enhance long-term functional resilience in the face of novel environmental scenarios. The use of plant functional traits for selecting species under climate change might be advantageous over more traditional taxon-based criteria as an adaptive forestry management strategy. In this work, we studied which functional traits (across species) have played a relevant role on field performance and fitness in a multi-species reforestation trial in a Mediterranean dryland affected by an extreme drought event. Different traits both from the individual plant and from the species were studied in seven species both at the short and the mid-term (10 years). The relative importance (RI) or contribution of the different traits to plantation performance was assessed through boosted regression tree models. The results showed that, under favorable climatic conditions, mean survival was above 70% and individual plant functional traits held up to 60% of importance on such value. The impact of species functional traits was low in this case (less than 18%) pointing out that all the species were performing within their niche at this point. However, after the driest year on record, the role of the latter on survival rose up to 53% of RI and survival sharply decreased to 33%, with some species showing negligible survival rate (<10%). The dynamic response of stomata and xylem resistance to cavitation, together with rooting depth, were the main traits (species traits) identified in successful performance facing the extreme environmental factors. Thus, trait-oriented approach to select species represent a key tool in the implementation of new and successful forest restoration strategies to design resistant and resilient ecosystems adapted to the climate change challenges.