Species- and community-level patterns in fine root traits along a 120 000-year soil chronosequence in temperate rain forest

Abstract

1. Below-ground plant functional traits regulate plant-soil interactions and may therefore strongly influence ecosystem responses to global change. Despite this, knowledge of how fine-root functional traits vary among plant species and along environmental gradients has lagged far behind our understanding of above-ground traits. 2. We measured species-and community-level root and leaf trait responses for 50 temperate rain forest species from 28 families of ferns, woody and herbaceous angiosperms and conifers, along a soil chronosequence in New Zealand that exhibits a strong gradient in soil nutrient availability. Relationships among species traits (both above-and below-ground) and their distribution along the chronosequence were tested using phylogenetic generalized least-squares regression to account for plant relatedness. 3. Distinctive root trait syndromes were observed; they were closely linked to species' distribution along the chronosequence. Species growing in the strongly P-limited late stages of the chronosequence had relatively high specific root length (SRL), thin root diameter, high root tissue density, high levels of root branching and low root nutrient concentrations compared to intermediate stages.Species on the youngest site also had high SRL, but had low root tissue density, thick root diameter and high root nutrient concentrations. 4. Species root and leaf nutrient concentrations were positively correlated, reflecting the strong underlying gradient in soil fertility. In contrast, the relationship between SRL and SLA was more complex; there was a weak positive correlation between SRL and SLA, but this conflicted with stronger patterns of increasing SRL and declining SLA with increasing site age. 5. Community-averaged trait values calculated using presence ⁄ absence data showed similar trends to the species-level patterns. In contrast, community averages calculated using species abundanceweighted data showed weaker relationships with site age, particularly for morphological traits. This suggests that much of the variation in morphological traits between sites was driven by shifts in the presence of subordinate or 'rare' species rather than by changes in the dominant species. 6. Synthesis. Our study demonstrates co-ordinated species-and community-level changes in root traits along a soil chronosequence. These results highlight the influence of soil nutrition on plant functional traits and contribute to our understanding of the drivers of community assembly in a changing environment.

Fine-root trait plasticity of beech (Fagus sylvatica) and spruce (Picea abies) forests on two contrasting soils

“…On the one hand, following the resource economics hypothesis (Grime 1977;Craine 2009), poor soils select for species with thick fine-roots that live long, so that valuable plant resources are conserved (Eissenstat and Yanai 1997;Aerts and Chapin 2000;Wahl and Ryser 2000;Pérez-Ramos et al 2012;Reich 2014); such relationships between fine-root traits and the soil environment might also exist within species. A contrasting hypothesis, however, predicts thinner fine-roots on poor soils, because these roots grow fast and can more efficiently exploit the soil for resources (Eissenstat 1992;Ryser and Lambers 1995;Eissenstat and Yanai 1997;Ostonen et al 2007b;Holdaway et al 2011;Prieto et al 2015). Both hypotheses have been corroborated and refuted with empirical data (e.g.…”

Invariant allometric scaling of nitrogen and phosphorus in leaves, stems, and fine roots of woody plants along an altitudinal gradient

“…Previous studies demonstrated that leaf N and P variation reflected environmental conditions more than plant intrinsic characteristics, such as genotype (Ågren and Weih 2012) and taxonomy (Zhang et al 2012). Although root nutrient concentrations were tightly associated with root diameter (Gordon and Jackson 2000), hierarchical branching and architecture (Iversen 2014;, they were also responsive indicators of soil nutrient availability Holdaway et al 2011) and climate at global and regional scale (Chen et al 2013;Yuan et al 2011). By contrast, stem which responsible for supporting and nutrient and water transport differed significantly in its construction costs among plant growth forms.…”

How does pedogenesis drive plant diversity?

“…Therefore, partitioning of P could become important for coexistence in retrogressive ecosystems where P is limiting [20]. However, no study has yet quantified the importance of these mechanisms in driving diversity patterns during long-term pedogenesis, although there is growing interest in shifts in the belowground traits of plants and plant functional diversity along soil chronosequences [27].…”