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The relative importance of soil depth for Aleppo pine (Pinus halepensis Mill.) resilience in face of the increasing aridity induced by climate change

Abstract:

Most of Spanish forests are currently growing under water deficit conditions. Climate change projections indicate an increase of water deficit stress upon Aleppo pine (Pinus halepensis Mill.) forests. Thus, soil water holding capacity and its availability for trees are important traits to consider when modeling forest responses to climate change and the effective soil volume for trees is closely related to their maximum rooting depth. In this work we evaluate the evolution over the 21th century of P. halepensis Spanish plots under climate change conditions and at two maximum rooting depths. We conclude that, under moderate climate change conditions, the fertilizing effect of an increasing atmospheric CO2 concentration would result on higher productivity, increased carbon sink capacity and higher resilience of P. halepensis forests. Conversely, under severe climate change scenario conditions, the CO2 fertilizing effect would be counterbalanced by the negative effects of increasing aridity. We show that the positive effect of an increased soil depth decreases under major climatic constraints (high temperature and low precipitation). However, we also obtained that it decreases under favorable conditions (mild temperatures 15 °C > T > 19 °C, and precipitation > 520 mm·year-1). We explain that fact because, as precipitation becomes less restrictive, photosynthesis is more linked to seasonal precipitation patterns than soil water storage capacity.