Trait–environment relationships remain strong despite 50 years of trait compositional change in temperate forests

Abstract

Temperate North American forest communities have changed considerably in response to logging, fragmentation, herbivory, and other global change factors. Significant changes in the structure and composition of seemingly undisturbed Wisconsin forest communities have occurred over the past 50 years, including widespread declines in alpha and beta species diversity. To investigate how shifts in species composition have affected distributions of plant functional traits, we first compiled extensive data on understory plant species traits. We then computed community-weighted trait means and functional diversity metrics for communities in both the 1950s and 2000s. We examined how trait values and diversity varied across environmental gradients and among Wisconsin's four main ecoregions. Trait means and diversity values reflect conspicuous gradients in species composition, soils, and climatic conditions. Over the past 50 years, values of most traits have changed as communities shifted toward species with higher leaf nutrient levels and specific leaf area, particularly in the southern ecoregions. Trait richness and diversity have declined, particularly in historically species- and trait-rich unglaciated southwestern Wisconsin. Reductions in within-site trait diversity may be diminishing the ability of these forest communities to resist or resiliently respond to shifts in environmental conditions. Despite changes in trait and community composition, trait-environment relationships measured directly via fourth-corner analysis remain strong for most plant traits. Nevertheless, accelerating ecological change (including climate change) could outstrip the ability of plant species and traits to match their environment, particularly in more fragmented landscapes.

Environmental filtering structures tree functional traits combination and lineages across space in tropical tree assemblages

“…However, at all spatial scales (10 × 10 m, 20 × 20 m, and 50 × 50 m), perhaps unexpectedly, we found that species with a large seed mass preferred the resource-rich part of the plot, while small-seeded species were distributed in the nutrient-limited part of the plot. A similar report also showed that large seed mass associated with nutrient-rich environments 41 . In summary, variation in the soil resource availability at these scales shapes the distribution of functional traits in a tropical forest.…”

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

“…We determined the dispersal mode of our 26 most common quadrat species by referring to a plant traits database compiled from literature and field specimens (Amatangelo et al . ). The sapling (0·6 cm ≤ DBH <10 cm) and tree tallies were converted to plot‐level averages for hardwood and conifer sapling and overstory basal area (BA, m 2 ha −1 ).…”

Tracking lags in historical plant species’ shifts in relation to regional climate change

“…Life history traits and range characteristics served to predict extinction risk due to climate change in some regions (Pearson et al ., ), but these responses are complex and rarely generalize to predict range shifts across a broad range of taxa (Angert et al ., ). In studies resurveying multiple species across many sites, species’ traits can help to disentangle diverse drivers of ecological change (Leach & Givnish, ; Damschen et al ., ; Crimmins et al ., ; Soudzilovskaia et al ., ; Amatangelo et al ., ; Savage & Vellend, ). It is thus reasonable to suppose that traits might help explain the complex responses of individual species to climate change.…”