Competition-interaction landscapes for the joint response of forests to climate change

Abstract

The recent global increase in forest mortality episodes could not have been predicted from current vegetation models that are calibrated to regional climate data. Physiological studies show that mortality results from interactions between climate and competition at the individual scale. Models of forest response to climate do not include interactions because they are hard to estimate and require long-term observations on individual trees obtained at frequent (annual) intervals. Interactions involve multiple tree responses that can only be quantified if these responses are estimated as a joint distribution. A new approach provides estimates of climate–competition interactions in two critical ways, (i) among individuals, as a joint distribution of responses to combinations of inputs, such as resources and climate, and (ii) within individuals, due to allocation requirements that control outputs, such as demographic rates. Application to 20 years of data from climate and competition gradients shows that interactions control forest responses, and their omission from models leads to inaccurate predictions. Species most vulnerable to increasing aridity are not those that show the largest growth response to precipitation, but rather depend on interactions with the local resource environment. This first assessment of regional species vulnerability that is based on the scale at which climate operates, individual trees competing for carbon and water, supports predictions of potential savannification in the southeastern US.

Half-century evidence from western Canada shows forest dynamics are primarily driven by competition followed by climate

“…Third, it is not too late to make proactive policies to facilitate the mitigation of climate change for sustainable management of forest ecosystems. For making management planning or policy decision, it is important to keep in mind that competition and climate change are not independent but interlocked processes that together affect species distribution (41) and demographic performance (19). It is certain that competition for resources will become more severe as the availability of resources (e.g., soil and water) becomes more variable and less predictable as the climate continues to change (25).…”

“…Climate at the regional or global scale is often presumed to be responsible for these changes (5)(6)(7)(8)(9)(10)(11)(12)(13)(14), with surprisingly little attention being paid to the possible effects of endogenous processes despite the fact that competition is often an important force driving stand dynamics and succession (15)(16)(17)(18). How climate change and competition interplay to affect the long-term change of demographic rates and what are their relative contributions to the change are unanswered questions (19,20).…”

Vulnerability of Commercial Tree Species to Water Stress in Logged Forests of the Guiana Shield

“…Recently, [17] showed that the response of wood production to anthropogenic climate change not only depends on the physiological responses of individual trees, but is also highly contingent on whether forests adjust in composition and structure. Indeed, some studies have shown that mortality results from interactions between climate and competition on an individual scale [18], but competition is hard to estimate [19,20] and is consequently seldom included in models of forest response to climate change.…”

“…Studies about the possible interactions between climate and logging on forest dynamics are hampered by data availability [18]. The intervals between censuses are often long [37], and climatic variables need to be aggregated over these long periods, erasing exceptionally wet or dry seasons' effects.…”

Macroscale intraspecific variation and environmental heterogeneity: analysis of cold and warm zone abundance, mortality, and regeneration distributions of four eastern US tree species

“…These models do, however, make large parametric assumptions imposed by the joint distribution of parameters, predictors, and responses, and has its own strengths and limitations that are beyond the scope of the present study (Clark et al. 2014). …”