Revising the biome concept for understanding and predicting global change impacts

Abstract

Biomes are globally distributed, structurally and functionally similar vegetation units defined without reference to plant species composition. The boundaries between biomes are presumed to correspond with species turnover and changes in biogeochemical cycling. Determining the controls of biome distributions is thus critical for anticipating global change impacts. Historically, climate and soils have been understood to adequately explain the global distribution of biomes. Convergent evolution and environmental filtering are assumed to be pervasive, ultimately resulting in deterministic patterns of vegetation structure and function in relation to prevailing environmental conditions. Recent studies have highlighted significant problems with this view of biomes. Firstly, systematic structural and functional divergence within biomes has been identified when comparing environmentally similar, yet floristically distinct regions. Secondly, climatic determinism is being further undermined by evidence suggesting multiple stable biome states are possible for some combinations of climatic drivers. We argue that biomes remain useful and necessary constructs for organizing our knowledge of how ecosystems function and for predicting how they might respond to change. However, biome concepts should acknowledge the limits to predictability from environmental conditions alone and the influence of historical processes on modern vegetation patterns. We discuss how direct mapping of plant structure and function, the incorporation of insights into biome evolution and a new generation of vegetation models will lead to improvements in the concept of what biomes are, where they occur, and efforts to predict their distribution.

The future distribution of the savannah biome: model-based and biogeographic contingency

“…This creates a challenge when attempting to model realized biome distributions, as model fit will be contingent upon historical events and initial conditions [58]. Regional differences in palaeoclimate and palaeovegetation as well as disturbance history will compound differences in the contemporary relationship between environmental conditions and vegetation patterns, in addition to regional differences due to floristics [59]. Using realistic, regionally appropriate initializations in DVMs can remedy this problem.…”

Ecological Responses to Climate Change at Biogeographical Boundaries

“…For this reason, the natural range boundaries of plants and sessile animals change relatively slowly. For instance, the contemporary biome distribution pattern in Africa does not reflect the actual current climate but historical conditions [47].…”

Resilience of tropical forest and savanna: bridging theory and observation

“…In theory, the concept reconciles seemingly opposing views on the environmental determinism vs. bistability debate for tropical ecosystems Veenendaal et al, 2015;Moncrieff et al, 2016). Namely, in a spatial context, the Maxwell convention implies predictable biome distributions based on environmental variables.…”

“…However, as the spatial scale decreases, the image becomes more complex, to the point that we are now: recognizing that forests and savannas can be alternative stable states under a range of conditions, which forces us to revise the classical paradigm of environmental determinism of the distribution of biomes (Hirota et al, 2011;Staver et al, 2011b;Murphy & Bowman, 2012;Moncrieff et al, 2016;chapter 3).…”

“…Therefore, in a bistable forest-savanna system, boundaries are difficult to predict based on external conditions (Moncrieff et al, 2016). Hence, bistability of forest and savanna on the one hand, and the climatic-deterministic explanation of forestsavanna distributions on the other, seem to represent two fundamentally incompatible views.…”