Possible changes in spatial distribution of walnut (Juglans regia L.) in Europe under warming climate

Sonia Paź-Dyderska,Andrzej M Jagodziński,Marcin K Dyderski

doi:10.1007/s10113-020-01745-z

Abstract

Juglans regia L. is a species of great importance for environmental management due to attractive wood and nutritious fruits, but also high invasive potential. Thus, uncertainties connected with its range shift are essential for environmental management. We aimed to predict the future climatic optimum of J. regia in Europe under changing climate, to assess the most important climatic factors that determine its potential distribution, and to compare the results obtained among three different global circulation models (GCMs). We used distribution data from the Global Biodiversity Information Facility and completed it with data from the literature. Using the MaxEnt algorithm, we prepared a species distribution model for the years 2061–2080 using 19 bioclimatic variables. We applied three emission scenarios, expressed by representative concentration pathways (RCPs): RCP2.6, RCP4.5, and RCP8.5 and three GCMs: HadGEM2-ES, IPSL-CM5A-LR, and MPI-SM-LR. Our study predicted northward shift of the species, with simultaneous distribution loss at the southern edge of the current range, driven by increasing climate seasonality. Temperature seasonality and temperature annual range were the predictors of highest importance. General trends are common for the projections presented, but the variability of our projections among the GCMs or RCPs applied (predicted range will contract from 17.4 to 84.6% of the current distribution area) shows that caution should be maintained while managing J. regia populations. Adaptive measures should focus on maintaining genetic resources and assisted migration at the southern range edge, due to range contraction. Simultaneously, at the northern edge of the range, J. regia turns into an invasive species, which may need risk assessments and control of unintended spread.

Highlights

Climate is one of the most important factors determining species ranges (Pearson and Dawson 2003; Hickler et al 2012; Scheffers et al 2016)
We aimed to (1) predict the future climatic optimum of J. regia in Europe based on climatic data, (2) assess the most important climatic factors that determine the potential distribution of the species studied, and (3) compare the results obtained among three different global circulation models (GCMs) used
We used MaxEnt modeling, as this procedure is widely used in species distribution modeling and it is robust to real absence data, which can influence model outcome settings (Phillips et al 2006, 2017; Elith et al 2011)

Summary

Introduction

Climate is one of the most important factors determining species ranges (Pearson and Dawson 2003; Hickler et al 2012; Scheffers et al 2016). From the physiological point of view, higher CO2 concentration increases the efficiency of photosynthesis C3 species, which is the most widespread in transitional climates (Kozlowski and Pallardy 1997) and accelerates biomass production (Hobbie and Chapin 1998; Liberloo et al 2006). Reg Environ Change (2021) 21: 18 predict increase of primary production and annual volume increments of trees, or even increased drought resistance (Lindner et al 2014). This effect will quickly subside due to increased evapotranspiration. Dynamic decreases of favorable conditions, intensified by catastrophic winds, extensive fires, or insect outbreaks (Seidl et al 2014), can lead to decline of number of species and growth of prices of wood used to make paper and furniture or fruits at the same time (Hertin et al 2003), as well as to decrease economic value of forests (Hanewinkel et al 2013)

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