Environment and past land use together predict functional diversity in a temperate forest

Abstract

Environment and human land use both shape forest composition. Abiotic conditions sift tree species from a regional pool via functional traits that influence species' suitability to the local environment. In addition, human land use can modify species distributions and change functional diversity of forests. However, it is unclear how environment and land use simultaneously shape functional diversity of tree communities. Land-use legacies are especially prominent in temperate forest landscapes that have been extensively modified by humans in the last few centuries. Across a 900-ha temperate deciduous forest in the northeastern United States, comprising a mosaic of different-aged stands due to past human land use, we used four key functional traits-maximum height, rooting depth, wood density, and seed mass-to examine how multiple environmental and land-use variables influenced species distributions and functional diversity. We sampled ~40,000 trees >8 cm DBH within 485 plots totaling 137 ha. Species within plots were more functionally similar than expected by chance when we estimated functional diversity using all traits together (multi-trait), and to a lesser degree, with each trait separately. Multi-trait functional diversity was most strongly correlated with distance from the perennial stream, elevation, slope, and forest age. Environmental and land-use predictors varied in their correlation with functional diversities of the four individual traits. Landscape-wide change in abundances of individual species also correlated with both environment and land-use variables, but magnitudes of trait-environment interactions were generally stronger than trait interactions with land use. These findings can be applied for restoration and assisted regeneration of human-modified temperate forests by using traits to predict which tree species would establish well in relation to land-use history, topography, and soil conditions.

Climate and habitat loss interactively restructure trait composition and covariance across a human-modified landscape

“…Trait-environment interactions: As expected, the four traits differed in their interaction with environmental variables to predict species distributions across the landscape (Krishnadas et al, 2018b), and traitenvironment interactions differed between fragments and contiguous forest (Table 1). Interestingly, models with elevation alone explained similar extents of variation in trait-mediated abundances as models with multiple environmental predictors (Table S1).…”

“…Fragments experience edge effects that alter the microclimate (De Frenne et al, 2019Zellweger et al, 2020) and forest-climate feedbacks that can enhance local climatic stress (Arroyo-Rodríguez et al, 2017;Laurance, 2004). Both processes can decouple the how different traits mediate community composition across macro-scale environmental gradients in fragments compared to contiguous forest (Fernandes Neto et al, 2019;Krishnadas et al, 2018b;Lebrija-Trejos et al, 2010;Poorter et al, 2019;Zirbel and Brudvig, 2020).…”

“…If selection along environmental gradients operates via individual traits, trait-environment correlations will be stronger for individual traits than multi-trait phenotypes in both contiguous forest and fragments (Butterfield and Suding, 2013;Krishnadas et al, 2018b). Alternatively, successful phenotypes may be determined by a combination of traits.…”

Climate shapes and shifts functional biodiversity in forests worldwide

“…Increasing the coverage and quality of community-wide datasets will strengthen analyses of trait-climate relationships by including other types of traits (e.g., physiological and phenological traits), a wider range of environmental factors (e.g., soil condition/nutrient composition, microclimate, disturbance), greater geographic coverage, and larger plots with more trait samples. In addition to the climatic conditions examined in this study, functional diversity could also be influenced by the history of local land use, management, or other forms of disturbance (39). Therefore, including information about site history may help increase the accuracy of trait-climate analyses.…”

Addressing trait selection patterns in temporary ponds in response to wildfire disturbance and seasonal succession

“…CATS regression analysis has been largely applied in plant communities (e.g. Baastrup-Spohr, Sand-Jensen, Nicolajsen, & Bruun, 2015;Janssen, Fuhr, Cateau, Nusillard, & Bouget, 2017;Krishnadas et al, 2018;Laughlin, Fulé, Huffman, Crouse, & Laliberté, 2011;Sonnier, Shipley, & Navas, 2010) and recently has been used in faunal communities (Bargmann et al, 2016;Harabiš & Dolný, 2018). Additionally, it has been used to assess the associated management strategies (Harabiš & Dolný, 2018) and to evaluate the impacts of disturbance on community assembly (Bargmann et al, 2016;Mouillot et al, 2013;Niu et al, 2016).…”