A plant economics spectrum in Mediterranean forests along environmental gradients: is there coordination among leaf, stem and root traits?

Abstract

Questions: Is there any evidence of coordination among leaf, stem and root traits, and thereby of the existence of a plant economics spectrum at the species and community level in Mediterranean forests? Are these traits related to plant size and seed mass?Location: Mediterranean forests and shrublands, Sierra Morena mountains, C ordoba, southern Spain. Methods:We selected nine woody plant communities along a natural local gradient of soil water and nutrient availability. We measured key leaf, stem, root and whole-plant traits for 38 dominant woody plant species. The variation across species of 15 functional traits (of the leaf, stem and root) was analysed and coordination among them was tested. We explored the relationships between these traits (hereafter 'resource-use traits' due to their close association with the acquisition-conservation trade-off) and plant height and seed mass. Finally, we compared results at species level with those calculated at community level, considering community-weighted means (CWMs). Results:We found a significant coordination between traits belonging to different plant organs, and propose the existence of a plant economics spectrum in Mediterranean forests along the environmental gradient. However, weaker relationships were found within groups of species under similar environmental conditions. We did not find the expected orthogonal relationships between plant height, seed mass and resource-use traits. Relationships among functional traits were stronger at the community level than at the species level.Conclusions: This study reveals a high degree of functional coordination between traits belonging to different plant organs at both species and community level, and suggests the existence of a plant economics spectrum across 38 Mediterranean woody plant species. However, this general trend of functional coordination between organs became weaker or disappeared when considering restricted groups of species belonging to environmentally similar sites (e.g. dry vs wet sites), suggesting that the diversification of strategies within communities is not related to the economics spectrum at a lower spatial scale. Interestingly, the high degree of coordination between resource-use traits and seed mass at the community level seems to support the tolerance-fecundity model, which predicts an inverse relationship between fecundity and stress tolerance.

Coordination and Determinants of Leaf Community Economics Spectrum for Canopy Trees and Shrubs in a Temperate Forest in Northeastern China

“…This result might be caused by different adaptations of shrubs and trees to environmental gradients, and we gave some explanations below. Our results (located in the continental monsoon climate zone) were consistent with those found by previous studies, which were primarily conducted in the Mediterranean climate zones [18][19][20]26]. This consistency across different climate zones and growth forms strengthened the evidence of widely existing leaf community economics spectrum.…”

“…The strong coordination of LES traits at the community level indicated the existence of a leaf community economics spectrum across trees and shrubs, which could be one part of plant community economics spectrum [18,19]. In addition, we found that the relationships of LES traits at both community levels were stronger than species level.…”

“…Upscaling the coordination of LES traits from within-species, among-species to the community level is an important step to allow us to predict how communities are constructed along an environmental gradient and respond to climate change. Previous studies have found stronger correlations among some functional traits at the community level than at the species level, and these community-level trait values were influenced by environmental factors such as soil nutrients and water content [17][18][19][20]. However, the determinants (e.g., environmental factors) of inter-correlated LES traits at the community level still require additional efforts due to their significant implications on the mechanisms of community assembly [17,21].…”

“…Although some new insights have been gained by relating certain LES traits (e.g., SLA) at the community level to environmental factors [16,17], the coordination of community-LES traits (i.e., mean values of species traits weighted by their relative abundance in a community; also can be called a 'leaf community economics spectrum' as a part of the 'plant community economics spectrum' [18]) have received little attention (but see [18,19]). Upscaling the coordination of LES traits from within-species, among-species to the community level is an important step to allow us to predict how communities are constructed along an environmental gradient and respond to climate change.…”

Decomposing functional trait associations in a Chinese subtropical forest

“…The relatively strong correlations between the only stem trait, wood density (WD), and the three leaf traits N green , LMA and LHL suggest that the observed trait syndromes can be extended to a leaf-stem economics. Such a trait coordination across organs is supported by many [48–53] studies, although there are exceptions [12, 46, 54, 55]. Reich [56] has argued that such a coordinated change in traits reflects a whole-plant strategy of “fast” vs. “slow” growth.…”