Climate Change Impacts on the Distribution and Diversity of Major Tree Species in the Temperate Forests of Northern Iran

Regional Environmental Change (2019) 19:2711–2728 https://doi.org/10.1007/s10113-019-01578-5 ORIGINAL ARTICLE Climate change impacts on the distribution and diversity of major tree species in the temperate forests of Northern Iran Hamid Taleshi1 & Seyed Gholamali Jalali1 & Seyed Jalil Alavi1 & Seyed Mohsen Hosseini1 & Babak Naimi2,3 & Niklaus E Zimmermann4 Received: 22 May 2019 /Accepted: 18 October 2019 /Published online: 27 November 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract This study aimed to assess the impacts of climate change on the distribution of major tree species in the temperate forests of Northern Iran (also known as Hyrcanian forests). We analyzed the current distributions of the eleven major tree species using an ensemble approach involving five different species distribution models (generalized linear model, generalized additive model, generalized boosting model, classification tree analysis, and random forests) and generated the ensemble maps of the current and future distribution of each species. For the future, we used five general circulation models and two representative concentration pathways (RCPs). Finally, we mapped beta-diversity and changes in alpha-diversity of the tree species under climate change. Our analyses showed that generally, the climatically suitable habitats for most of the species tend to shift and shrink in the future. A shift in major trees boundaries will be expected both along an east-west gradient and along an altitudinal gradient under climate change scenarios. The results demonstrated that climate change is likely to exert a strong influence on beta-diversity and richness of the major tree species in northern forests of Iran. In total, beta-diversity of tree species will be higher in the central and eastern parts compared with the western areas under the climate change scenarios and the mid-elevations of the western Hyrcanian forests will likely experience the lowest beta-diversity through time, meaning that the impacts of climate change on these regions are minimal. The impacts of climate change on the distribution of major tree species in the Hyrcanian forests can be considered very severe and pose a high risk of loss in forest functions and services. Forest managers will encounter several uncertainties in the wood productions, plantation, restoration, and conservation plans due to climate change in the Hyrcanian forests. Keywords Beta-diversity . Ensemble models . Hyrcanian forests . Species distribution models . True turnover . Uncertainty Introduction Living organisms are the relevant components of eco- Communicated by Wolfgang Cramer systems, and their survival and functioning heavily de- Electronic supplementary material The online version of this article pend on climatic conditions (Woodward 1987). Keeping (https://doi.org/10.1007/s10113-019-01578-5) contains supplementary their balance with climate is necessary for the sustain- material, which is available to authorized users. ability and stability of global ecosystems (Khaine and Woo 2015). It is a focal premise of biogeography that * Seyed Jalil Alavi climate is one of the principal factors controlling the [email protected] natural distribution of plant species over large areas such as an ecoprovince or forest region (Guisan and 1 Department of Forestry, Faculty of Natural Resources and Marine Zimmermann 2000; Pearson and Dawson 2003;Rose Sciences, Tarbiat Modares University, Noor, Iran and Burton 2009). Understanding the mechanisms and 2 Ecosystem Management, Department of Environmental Systems impacts of climate on tree species is essential for suc- Science, ETH Zurich, 8092 Zurich, Switzerland cessful management and conservation of forest resources 3 Department for Migration and Immuno-ecology, Max Planck (Rose and Burton 2009). Institute for Ornithology, 78315 Radolfzell, Germany Climate change is one of the major challenges of our time. 4 Swiss Federal Research Institute WSL, Birmensdorf, Switzerland Warming of the climate system has been accelerated since 2712 H. Taleshi et al. 1950s, and many of the observed changes such as warming Forest managers need to adopt long-term management de- atmosphere and oceans, decreasing snow and ice, rising sea cisions while uncertainty about the impacts of climate change water levels, and increasing greenhouse gas concentrations is still large (Keenan 2012; Lindner et al. 2014). There are occur at unprecedented pace (IPCC 2014). In each of the last many sources of uncertainty including (a) climatic uncer- three decades, the surface temperature of earth has been con- tainties, arising from the different general circulation models sistently warmed compared with preceding decades since the (GCMs) and greenhouse gas emission scenarios, b uncertainty 1850s. The global mean of the combined land and ocean sur- arising from the sensitivity and response of forests, c algorith- face temperature reveals a warming of 0.85 °C over the period mic uncertainties, arising from the differences in simulation of 1880 to 2012 (IPCC 2014). Moreover, the data shows that models, and the inputs and parameters of models, and d biotic the last 30 years have been the warmest period in the last uncertainties, arising from the inappropriate assumptions of 1400 years in the Northern Hemisphere (IPCC 2014). the biology of a species (Lindner et al. 2014; Pacifici et al. The impacts of climate change on tree species can affect the 2015). Due to the inherent variability of the natural systems in sensitive balance within ecosystems (Vessella et al. 2017). space and time, models of natural systems, including SDMs, Future climate change can lead to shifts in the distribution inevitably include some degrees of uncertainty (Gould et al. and abundance of species (Ehrlén and Morris 2015; Thomas 2014). One of the main challenges of SDMs is the appropriate et al. 2004;Wangetal.2018), extinction of species popula- model selection among the wide variety of available models tions (Bestion et al. 2015; Keith et al. 2008;Thomasetal. (Buisson et al. 2010). Ensemble forecasting is an appropriate 2004), range shifts (Bellard et al. 2012; Chen et al. 2011; solution to quantify the variation originating from a range of Iverson and McKenzie 2013; Nenzén and Araújo 2011), phe- choices made during the modeling process (Araújo and New nological changes (Anenkhonov 2009; Merilä and Hendry 2007). An ensemble forecasting which ultimately combines 2014; Wolkovich et al. 2012), and physiological trait changes the predictions of different SDMs and GCMs can thus be used (Bozinovic and Pӧrtner 2015;Dillonetal.2010). In addition, to quantify uncertainties associated with model projections climate change can affect the distribution and composition of under climate change (Vieilledent et al. 2013). forests (Dunckel et al. 2017; Joshi et al. 2012;Wangetal. Global climate change has started to exert unavoidable 2013). Shifts in plant species, geographical distributions, and consequences in Iran. Analyses of the recent climate change range contractions with extinctions at the lower elevational show an increasing temperature trend in many synoptic and latitudinal limits can be the consequence of changes in weather stations of Iran (Azizi and Roshani 2008; Molavi- the normal patterns of temperature and humidity. These pat- Arabshahi et al. 2016). Given that Iranian forests already have terns of changes are among the prime expected impacts of been strongly affected by droughts, it can be clearly concluded projected future climate change (Koralewski et al. 2015; that the climate has been warming in the temperate forest Ladányi et al. 2015; Schwart 1993; Thuiller 2007; Zomer ecosystems of Northern Iran, the Hyrcanian forests (Attarod et al. 2015). et al. 2017; Jafari 2008; Molavi-Arabshahi et al. 2016). Species distribution models (SDMs) have been used wide- Despite many concerns about the impacts of climate change ly in biogeography to characterize the ecological niche of on biodiversity, its effects on plant and animal species in Iran plants and animals and to predict the geographical distribu- are unknown to date. Although in the recent years, many stud- tions of their habitats. Species distribution modeling is usually ies have investigated the impacts of climate change on the based on characterizing the statistical relationship between future distributions of trees species in different regions of the environmental variables and the occurrence or abundance of world (Benito Garzón et al. 2008; Chala et al. 2016;Iverson species (Guillera-Arroita et al. 2015; Guisan and and Prasad 2002;Koralewskietal.2015;Lengetal.2008; Zimmermann 2000; Hasui et al. 2017;Miller2010). SDMs Remya et al. 2015; Trisurat et al. 2011;Xuetal.2009; Zhang generate a probabilistic projection of the realized ecological et al. 2018), a very few studies addressed these issues in the niche for a species in a geographic space for a given period of forests of Iran. In a study by Haidarian Aghakhani et al. time (Guisan et al. 2017). They are widely used to project the (2017a) that investigated the redistribution of Amygdalus future distributions of organisms under climatic and land-use scoparia species under climate change using GLM, CTA, change scenarios (Bruneel et al. 2018; Chala et al. 2016; ANN, GBM, and RF in Chaharmahal and Bakhtiari province Enquist 2002;Khanumetal.2013;McKenneyetal.2007; in Iran, the results indicated that suitable habitats of Santos et al. 2015), assess invasion risk of exotic species A. scoparia will be decreased about

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