Linkages between Climate, Radial Growth and Defoliation in Abies pinsapo Forests from Southern Spain

Rafael Navarro-Cerrillo,Carlos Rodríguez-Vallejo,Guillermo Palacios-Rodríguez,Rubén Manzanedo,J Camarero,Antonio Gazol

doi:10.3390/f11091002

Rafael Navarro-Cerrillo, Carlos Rodríguez-Vallejo + Show 4 more

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https://doi.org/10.3390/f11091002

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Abstract

Systematic forest networks of health monitoring have been established to follow changes in tree vigor and mortality. These networks often lack long-term growth data, but they could be complemented with tree ring data, since both defoliation and radial growth are proxies of changes in tree vigor. For instance, a severe water shortage should reduce growth and increase tree defoliation in drought-prone areas. However, the effects of climatic stress and drought on growth and defoliation could also depend on tree age. To address these issues, we compared growth and defoliation data with recent climate variability and drought severity in Abies pinsapo old and young trees sampled in Southern Spain, where a systematic health network (Andalucía Permanent Plot Network) was established. Our aims were: (i) to assess the growth sensitivity of old and young A. pinsapo trees and (ii) to test if relative changes in radial growth were related with recent defoliation, for instance, after severe droughts. We also computed the resilience indices to quantify how old and young trees recovered growth after recent droughts. Wet-cool conditions during the prior autumn and the current early summer improved the growth of old trees, whereas late-spring wet conditions enhanced the growth of young trees. Old trees were more sensitive to wet and sunny conditions in the early summer than young trees. Old and young trees were more responsive to the Standardized Precipitation-Evapotranspiration Index drought index of June–July and July–August calculated at short (one–three months) and mid (three–six months) time scales, respectively. Old trees presented a higher resistance to a severe drought in 1995 than young trees. A positive association was found between stand defoliation and relative growth. Combining monitoring and tree ring networks is useful for the detection of early warning signals of dieback in similar drought-prone forests.

Highlights

IntroductionBiotic and abiotic stressors (climatic events, insect outbreaks or fungal leaf diseases) have increased during the last decades, leading to changes in tree ring growth responses [1]
Biotic and abiotic stressors have increased during the last decades, leading to changes in tree ring growth responses [1]
We found a marked decrease in the basal area increment (BAI) during two principal droughts

Summary

Introduction

Biotic and abiotic stressors (climatic events, insect outbreaks or fungal leaf diseases) have increased during the last decades, leading to changes in tree ring growth responses [1]. ICP Forests plots characterize tree conditions by descriptors, including defoliation (e.g., leaf deficit relative to a so-called reference tree), among others [4], in an attempt to integrate the physiological mechanisms by which biotic and abiotic stressors affect tree vigor and are translated into radial growth variations, this process is complex [5,6]. It is unclear how coupled are defoliation and growth, because this relationship may be speciesand site-dependent and co-vary with other climatic parameters and physiological responses [7]. The negative impact of drought events on tree growth and the sensitivity of some tree species to current and previous unfavorable climatic conditions is well-established [9]

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