Drought Sensitiveness on Forest Growth in Peninsular Spain and the Balearic Islands

Marina Peña-Gallardo,Edurne Martínez Del Castillo,Ahmed El Kenawy,Fernando Silla,Mar Génova,Santiago Beguería-Portugés,Montserrat Ribas Matamoros,Álvaro Camisón,Vicente Rozas,Andrea Hevia,Antonio Gazol,Klemen Novak,Emília Gutiérrez ,Ignacio García‐González ,Raúl Sánchez‐Salguero ,Gabriel Sangüesa‐Barreda ,Martín De Luis ,José Miguel Olano ,Juan Carlos Linares ,Sergio M Vicente‐Serrano ,Luis Alberto Longares ,J Julio Camarero ,Fernando Domínguez‐Castro ,Pedro Antonio Tíscar ,J Diego Galván

doi:10.3390/f9090524

Abstract

Drought is one of the key natural hazards impacting net primary production and tree growth in forest ecosystems. Nonetheless, tree species show different responses to drought events, which make it difficult to adopt fixed tools for monitoring drought impacts under contrasting environmental and climatic conditions. In this study, we assess the response of forest growth and a satellite proxy of the net primary production (NPP) to drought in peninsular Spain and the Balearic Islands, a region characterized by complex climatological, topographical, and environmental characteristics. Herein, we employed three different indicators based on in situ measurements and satellite image-derived vegetation information (i.e., tree-ring width, maximum annual greenness, and an indicator of NPP). We used seven different climate drought indices to assess drought impacts on the tree variables analyzed. The selected drought indices include four versions of the Palmer Drought Severity Index (PDSI, Palmer Hydrological Drought Index (PHDI), Z-index, and Palmer Modified Drought Index (PMDI)) and three multi-scalar indices (Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Precipitation Index (SPI), and Standardized Precipitation Drought Index (SPDI)). Our results suggest that—irrespective of drought index and tree species—tree-ring width shows a stronger response to interannual variability of drought, compared to the greenness and the NPP. In comparison to other drought indices (e.g., PDSI), and our results demonstrate that multi-scalar drought indices (e.g., SPI, SPEI) are more advantageous in monitoring drought impacts on tree-ring growth, maximum greenness, and NPP. This finding suggests that multi-scalar indices are more appropriate for monitoring and modelling forest drought in peninsular Spain and the Balearic Islands.

Highlights

Drought is a major hydroclimatic hazard that is difficult to quantify, analyze, monitor and, mitigate [1]
The net primary production (NPP) depends on the fraction of photosynthetically active radiation (FPAR) absorbed by the canopy [74]
We found that multi-scalar drought indices metrics and tree growth to water shortage

Summary

Introduction

Drought is a major hydroclimatic hazard that is difficult to quantify, analyze, monitor and, mitigate [1]. This is because drought has a complex nature, given that it is the result of the synergy among a wide range of variables (e.g., precipitation, temperature, land use, human activities, etc.). Assessing the impacts of drought on natural and human environments can vary among regions and systems depending on their response and vulnerability. Local environmental and climatic conditions can complicate further the response of forests to drought [13,14]. Assessing forest response to drought is a challenging task, as species [15], and even individuals [16], differ in their sensitivity to this phenomenon. Spatial variability in climatic and topographic conditions adds a finer grain to drought pattern predictions

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