Local range boundaries vs. large‐scale trade‐offs: climatic and competitive constraints on tree growth

Abstract

Species often respond to human‐caused climate change by shifting where they occur on the landscape. To anticipate these shifts, we need to understand the forces that determine where species currently occur. We tested whether a long‐hypothesised trade‐off between climate and competitive constraints explains where tree species grow on mountain slopes. Using tree rings, we reconstructed growth sensitivity to climate and competition in range centre and range margin tree populations in three climatically distinct regions. We found that climate often constrains growth at environmentally harsh elevational range boundaries, and that climatic and competitive constraints trade‐off at large spatial scales. However, there was less evidence that competition consistently constrained growth at benign elevational range boundaries; thus, local‐scale climate‐competition trade‐offs were infrequent. Our work underscores the difficulty of predicting local‐scale range dynamics, but suggests that the constraints on tree performance at a large‐scale (e.g. latitudinal) may be predicted from ecological theory.

Widespread drought‐induced tree mortality at dry range edges indicates that climate stress exceeds species' compensating mechanisms

“…As a caveat, we note that some of the studies in our meta‐analysis examined local/regional range limits, rather than the full geographic range. However, examining population responses along a moisture gradient can be fruitful for understanding biotic and abiotic factors controlling biogeographic boundaries (Anderegg & HilleRisLambers, ). Furthermore, our results were robust when considering only those studies that examined large‐scale or full species ranges (Figure S2).…”

Continental‐scale tree‐ring‐based projection of Douglas‐fir growth: Testing the limits of space‐for‐time substitution

“…carbon sequestration, climate sensitivity, Douglas-fir, forest inventory, growth projection, mixed-effects model, tree growth, tree ring to interannual climate variation trend in opposite directions across the environmental gradient from the forest interior to the forest edge (see also Anderegg & HilleRisLambers, 2019;Knapp, Ciais, & Smith, 2017), a prediction that we illustrate in Figure 1. An important caveat, however, is that SFTS relies on the assumption that the process(es) giving rise to spatial variation are the same as those giving rise to temporal variation.…”

“…Indeed, ecological niche theory suggests that organismal performance (e.g., growth) should vary in a predictable fashion, decreasing continuously from the niche optimum to its edge (Hutchinson, 1978; Maguire, 1973). In a now classic figure in dendrochronology, Fritts, Smith, Cardis, and Budelsky (1965, their figure 2) went one step further in describing predictable variation in tree‐ring widths: average ring width and ring‐width sensitivity to interannual climate variation trend in opposite directions across the environmental gradient from the forest interior to the forest edge (see also Anderegg & HilleRisLambers, 2019; Knapp, Ciais, & Smith, 2017), a prediction that we illustrate in Figure 1. An important caveat, however, is that SFTS relies on the assumption that the process(es) giving rise to spatial variation are the same as those giving rise to temporal variation.…”

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

“…This hypothesis is a major tenet of biogeography and has been subsumed in various definitions of the niche in ecology (Brown, Stevens, & Kaufmnan, ; Connell, ; Dobzhansky, ; MacArthur, ). It has undergone a recent resurgence given its potential to better understand the impacts of global change on species distributions (Anderegg & HilleRisLambers, ; Dvorský, Macek, Kopecký, Wild, & Doležal, ; Louthan, Doak, & Angert, ; Normand et al, ).…”

“…This hypothesis is a major tenet of biogeography and has been subsumed in various definitions of the niche in ecology (Brown, Stevens, & Kaufmnan, 1996;Connell, 1961;Dobzhansky, 1950;MacArthur, 1984). It has undergone a recent resurgence given its potential to better understand the impacts of global change on species distributions (Anderegg & HilleRisLambers, 2019;Dvorský, Macek, Kopecký, Wild, & Doležal, 2017;Louthan, Doak, & Angert, 2015;Normand et al, 2009). However, after more than a century of theoretical and empirical groundwork, there is little consensus on the extent to which abiotic and biotic factors (see Box 1 for definitions) determine range limits and how this varies by distributional edge position (Alexander, Diez, Usinowicz, & Hart, 2018;Godsoe, Jankowski, Holt, & Gravel, 2018;Louthan et al, 2015).…”