Climatic extremes improve predictions of spatial patterns of tree species

Abstract

Understanding niche evolution, dynamics, and the response of species to climate change requires knowledge of the determinants of the environmental niche and species range limits. Mean values of climatic variables are often used in such analyses. In contrast, the increasing frequency of climate extremes suggests the importance of understanding their additional influence on range limits. Here, we assess how measures representing climate extremes (i.e., interannual variability in climate parameters) explain and predict spatial patterns of 11 tree species in Switzerland. We find clear, although comparably small, improvement (؉20% in adjusted D 2 , ؉8% and ؉3% in cross-validated True Skill Statistic and area under the receiver operating characteristics curve values) in models that use measures of extremes in addition to means. The primary effect of including information on climate extremes is a correction of local overprediction and underprediction. Our results demonstrate that measures of climate extremes are important for understanding the climatic limits of tree species and assessing species niche characteristics. The inclusion of climate variability likely will improve models of species range limits under future conditions, where changes in mean climate and increased variability are expected.climate change ͉ ecological niche ͉ generalized additive model ͉ geographic range ͉ species distribution models T he understanding of the principles and mechanisms that shape distribution patterns has long been a focus in biogeographical, ecological, and evolutionary research. The ecological niche concept, coined and initially developed by Grinnell (1), is the foundation for our understanding of the processes that shape the geographical distributions of species (2). Conceptual clarifications with regards to using the concept for the explanation of species ranges have been presented by several authors (3, 4). Climatic variables are often used to predict biogeographical patterns (5), and considerable effort has been put into improving methods to describe the response of species along climate gradients (6-8). These methods of species distribution or niche modeling are frequently used for conservation management (9-12), prediction of the likely effects of global change (13-16), and, increasingly, assessment of niche characteristics in the study of niche evolution (17)(18)(19)(20). These studies in general use monthly or annual climatic means to analyze species distribution patterns. To date, little attention has been paid to the question of how climatic extremes, i.e., the long-term, interannual variation around mean values, could help to explain species distributions. There are two major reasons that highlight the importance of including climatic variability in niche analyses and models. First, ongoing climate change not only affects means but also extremes (21). Second, niche evolution often results in changes of the stress tolerance of evolving clades (22, 23). Thus, both adaptation and possible future response of species to c...

A spatial and temporal drought risk assessment of three major tree species in Britain using probabilistic climate change projections

“…Epistemic uncertainty as a limited knowledge about tree species response to extreme drought remains high compared with better knowledge about average drought impacts in British conditions. A recent study by Zimmermann et al (2009) highlighted the need for information about climate extremes that can improve our understanding of species limits and support robust estimations of species distributions. Extreme droughts are more damaging, affect forest productivity (Ciais et al 2005), and are projected to become more frequent in the future (Meehl and Tebaldi 2004).…”

Climate change impacts and adaptation in forest management: a review

“…Current forecasting approaches that produce future climate averages may make it difficult to detect non-linear ecosystem dynamics, or threshold effects, that could trigger abrupt ecosystem change (Campbell et al 2009). Zimmermann et al (2009) found that predictions of spatial patterns of tree species in Switzerland were improved by incorporating measures of extremes in addition to means in SDMs.…”

Raznolikost i strukturiranost hrvatskih kontinentalnih i alpsko-dinarskih populacija bijele johe (Alnus incana /L./ Moench subsp. incana); geografska i okolišna izolacija kao uzrok fenotipske divergencije

“…To evaluate the correlation between multicharacter differences among populations, a Mantel test (Mantel 1967) was performed on the matrices of Euclidean distances. First, the correlations among all 19 WorldClim bioclimatic variables and topographic variables for all presence points were calculated to exclude the highly correlated ones, whilst keeping the variables useful in predicting the distribution limits of trees, such as climatic averages and extremes (Zimmermann et al 2009;Temunović et al 2012). We computed and tested the correlations between: (1) the matrix of the geographical distances between pairs of populations and the matrix of morphological differences among populations -"isolation by distance" (Wright 1943); and (2) the matrix of environmental distances and the matrix of morphological differences among populations -"isolation by environmental distance" (Mendez et al 2010).…”