Community‐weighted means and functional dispersion of plant functional traits along environmental gradients on Mount Kilimanjaro

Abstract

Question: How do community-weighted means of traits (CWM) and functional dispersion (FDis), a measure of trait variability, change in response to gradients of temperature, precipitation, soil nutrients, and disturbance? Is the decrease in trait similarity between plots continuous or discontinuous? Is species turnover between plots linked to trait turnover? Location: Mount Kilimanjaro, Tanzania, Africa. Accepted ArticleThis article is protected by copyright. All rights reserved.Methods: Sixty plots were established in twelve major vegetation types on Mount Kilimanjaro, covering large gradients of temperature, precipitation, soil nutrients, and anthropogenic disturbance representing the dominant ecosystems in East Africa. Environmental data, plant abundances, and plant traits were recorded for each plot. Trait CWM and FDis were related to environmental factors with partial least squares regressions. Trait similarity between pairs of plots was assessed with a null-model approach.Results: Both CWM and FDis of most traits responded strongly to environmental factors, particularly to precipitation and disturbance. FDis of traits associated with growth and reproduction mostly increased with temperature and precipitation, and decreased with disturbance. Pairwise plot comparisons revealed an inverse relationship of trait similarity with differences in temperature, precipitation, and anthropogenic disturbance, respectively. However, changes in similarity were often discontinuous rather than continuous. Several vegetation types differed strongly in species composition but not in traits. Conclusions:Trait dispersion indicating functional niches increased with productivity and temperature. Conversely, low-productivity conditions were characterized by trait convergence.Discontinuous changes in trait similarity between plots suggested tipping points at which trait expressions change strongly to adjust to environmental conditions. Large sections of the temperature gradient were characterized by species turnover with only minor changes in traits, indicating that the functional composition may be resilient against gradual environmental changes until a tipping point is reached.

Trait patterns of epiphytes compared to other plant life‐forms along a tropical elevation gradient

“…The CWM of traits were expected to vary along the elevation gradient, as it comprises large differences in temperature and precipitation, among others (Schellenberger Costa et al., ). While elevation and (above‐canopy) temperature are directly linked via an adiabatic lapse rate of 0.5°C * 100 m −1 (Hemp, ), precipitation is only one factor influencing water availability, besides seasonality, soil water retention capability and evaporation (Moles et al., ; Oki & Kanae, ).…”

“…The strong differences in the contribution of taxonomic levels to overall variance in trait expressions reflected the complex phylogenetic composition of the communities in our study system. While the nearly complete absence of trees in a number of plant orders moved most plant height variance towards the order level, the response of plants to soil nutrients at the individual level (Hedwall, Bergh, & Brunet, ) and the heterogeneity of the soils on the mountain slopes (Schellenberger Costa et al., ) likely lead to a strong within‐species variance component in leaf N and P mass .…”

“…The CWM of traits were expected to vary along the elevation gradient, as it comprises large differences in temperature and precipitation, among others (Schellenberger Costa et al, 2017).…”

Spatial patterns and determinants of trait dispersion in freshwater fish assemblages across Europe

“…On the contrary, degraded systems present higher trait dispersion than unimpacted bird communities (Bregman et al, 2015). Thus, one might expect that human-related land use is likely to affect trait dispersion, especially the dispersion patterns of beta traits, although the intensity of the influence might depend on the type of disturbance and on the trait considered (Schellenberger Costa et al, 2017).…”

Temporal intraspecific trait variability drives responses of functional diversity to interannual aridity variation in grasslands

“…The latter component can be expressed by various indices, among which Rao's quadratic entropy (Botta-Dukat, 2005), functional dispersion (Laliberté & Legendre, 2010), and functional divergence (Villéger, Mason, & Mouillot, 2008) are widely used. Both the mean and dispersion of traits are influenced by environmental factors such as climate, land-use regime, or biotic interactions (Carmona, Mason, Azcarate, & Peco, 2015;Pescador, Sierra-Almeida, Torres, & Escudero, 2016;Schellenberger Costa et al, 2017). Environmental filters restrict the range of traits (Díaz, Cabido, & Casanoves, 1998), and a limiting similarity of coexisting species may occur due to fine-scale niche partitioning (Cornwell & Ackerly, 2009;Muscarella & Uriarte, 2016).…”