Alpine climate alters the relationships between leaf and root morphological traits but not chemical traits

Abstract

Leaves and fine roots are among the most important and dynamic components of terrestrial ecosystems. To what extent plants synchronize their resource capture strategies above- and belowground remains uncertain. Existing results of trait relationships between leaf and root showed great inconsistency, which may be partly due to the differences in abiotic environmental conditions such as climate and soil. Moreover, there is currently little evidence on whether and how the stringent environments of high-altitude alpine ecosystems alter the coordination between above- and belowground. Here we measured six sets of analogous traits for both leaves and fine roots of 139 species collected from Tibetan alpine grassland and Mongolian temperate grassland. N, P and N:P ratio of leaves and fine roots were positively correlated, independent of biogeographic regions, phylogenetic affiliation or climate. In contrast, leaves and fine roots seem to regulate morphological traits more independently. The specific leaf area (SLA)-specific root length (SRL) correlation shifted from negative at sites under low temperature to positive at warmer sites. The cold climate of alpine regions may impose different constraints on shoots and roots, selecting simultaneously for high SLA leaves for rapid C assimilation during the short growing season, but low SRL roots with high physical robustness to withstand soil freezing. In addition, there might be more community heterogeneity in cold soils, resulting in multidirectional strategies of root in resource acquisition. Thus our results demonstrated that alpine climate alters the relationships between leaf and root morphological but not chemical traits.

Complex trait relationships between leaves and absorptive roots: Coordination in tissue N concentration but divergence in morphology

“…Similar to our results, previous studies also pointed out that there are independent strategies between above‐ and belowground plant morphology (Craine et al., 2005; Geng et al., 2014; Tjoelker et al., 2005). Several hypotheses have been put forward to explain this phenomenon.…”

“…Second, above‐ and belowground morphological traits may vary independently or even in opposite directions as a way to adapt to the multiple environmental gradients (Craine et al., 2005; Geng et al., 2014). Results of Geng et al.…”

“…Some stoichiometric studies have shown that the leaf and root N (Craine, Lee, Bond, Williams, & Johnson, 2005; Liu et al., 2010; Valverde‐Barrantes, Smemo, & Blackwood, 2015) and P concentrations (Geng, Wang, Jin, Liu, & He, 2014; Holdaway, Richardson, Dickie, Peltzer, & Coomes, 2011; Kerkhoff et al., 2006) are positively correlated, providing support for the nutrient portion of the plant economics spectrum hypothesis. However, among morphological traits, results of trait relationships are mixed and dependent on spatial scale, geographical region, and plant growth form (Craine et al., 2005; Geng et al., 2014; Holdaway et al., 2011).…”

“…Some stoichiometric studies have shown that the leaf and root N (Craine, Lee, Bond, Williams, & Johnson, 2005; Liu et al., 2010; Valverde‐Barrantes, Smemo, & Blackwood, 2015) and P concentrations (Geng, Wang, Jin, Liu, & He, 2014; Holdaway, Richardson, Dickie, Peltzer, & Coomes, 2011; Kerkhoff et al., 2006) are positively correlated, providing support for the nutrient portion of the plant economics spectrum hypothesis. However, among morphological traits, results of trait relationships are mixed and dependent on spatial scale, geographical region, and plant growth form (Craine et al., 2005; Geng et al., 2014; Holdaway et al., 2011). For example, the reported specific leaf area–specific root length (SLA–SRL) relationship varied from positive (Liu et al., 2010; Withington, Reich, Oleksyn, & Eissenstat, 2006) to negative (Li & Bao, 2015), nonsignificant (Chen et al., 2013; Tjoelker, Craine, Wedin, Reich, & Tilman, 2005; Valverde‐Barrantes et al., 2015), or an environment‐dependent relationship (Geng et al., 2014; Holdaway et al., 2011).…”

“…Thus, we predict that relationships between leaf and absorptive root morphological traits may depend on plant phylogeny, and this possible coordination would disappear after adjusting for phylogenetic relatedness. Also, the possible morphological linkage between above‐ and belowground organs may differ between woody and nonwoody plant species because of the difference in their root branch systems (Geng et al., 2014; Roumet et al., 2016). …”