Functional perspectives on tropical tree demography and forest dynamics

Abstract

Disentangling the processes that drive population, community and whole forest structure and dynamics is a challenge. It becomes a grand challenge in the tropics where there are a large number of species, small population sizes, less research infrastructure, and a relatively smaller number of researchers compared to the temperate zone. Tackling this grand challenge, we argue, requires detailed knowledge of the functioning of individuals and species. To this end, researchers frequently employ plant functional traits to study tree populations and communities. Here, we review this approach by first providing a basic background regarding the major trait axes generally of interest. We then discuss how these axes may be or have been applied from ecosystem to community and population studies. In doing so, we highlight where the functional trait research program has failed in tropical tree ecology and where it can be improved or strengthened. Finally, we provide a perspective regarding how functional trait and emerging 'omics approaches can be integrated to address large questions facing the field. Our intention throughout is to provide an entryway into this literature for an early career researcher rather than a comprehensive review of all possible studies that have taken place in tropical forests.

A Reframing of Trait–Demographic Rate Analyses for Ecology and Evolutionary Biology

“…First, while some have found moderately strong or strong relationships between traits and demographic performance, these studies have been the exception and not the rule. Indeed, most studies find surprisingly little variation in demography explained by commonly measured traits (Yang et al 2018;Worthy and Swenson 2019). Second, the empirical failure to routinely and robustly link functional traits to demographic rates and underappreciated conceptual connections have limited a synthesis between trait-based population and community ecology and evolutionary ecology (McGill et al 2006).…”

Testing for functional significance of traits: Effect of the light environment in tropical tree saplings

“…However, studies that found a moderate or strong trait-growth rate relationship are an exception (Swenson et al, 2020). In this sense, recent studies have concentrated efforts in understanding why weak relationships are frequent and defining standardized protocols for studies of trait-based community ecology (Caruso et al, 2020;Swenson et al, 2020;Worthy & Swenson, 2019;Yang et al, 2018). Some methodological aspects of sampling may affect the ability of traits to predict growth rates, such as 1) lack of environmental context, 2) use of nonfunctional traits, 3) approaches that do not contemplate phenotypic integration, and 4) neglect of intraspecific variation (Yang et al, 2018;Yang et al, 2020;Worthy & Swenson, 2019).…”

“…For example, in high-light environments, physiological traits related to photosynthetic nutrient use efficiency are highly related to growth (Guimarães et al, 2018), while in low-light environments, morphological traits related to light interception are highly related to growth (Liu et al, 2016). Studies that examine the effects of environmental contexts on trait-trait and trait-growth relationships are necessary, especially in tropical forests (Worthy & Swenson, 2019).…”

“…Most studies developed to date have focused on measuring soft traits due to an easy applicability and a lower required investment (Gibert et al, 2016;Worthy & Swenson, 2019;Yang et al, 2018).…”

Temporal trait plasticity and neighborhood crowding predict the growth of tropical trees

“…Averaging trait values of individuals across the species ignores individual level trait variation, limiting the ability of traits to predict individual growth rates (Liu et al 2016, Umaña et al 2018. Individuals traits may predict better the growth performance of individuals, as trait differences determine individuals' growth strategies (Yang et al 2018, Worthy & Swenson 2019.…”