Evidence of Differences in Covariation Among Root Traits Across Plant Growth Forms, Mycorrhizal Types, and Biomes

Abstract

Fine roots play an important role in plant ecological strategies, adaptation to environmental constraints, and ecosystem functions. Covariation among root traits influence the physiological and ecological processes of plants and ecosystems. Root trait covariation in multiple dimensions at the global scale has been broadly discussed. How fine-root traits covary at the regional scale and whether the covariation is generalizable across plant growth forms, mycorrhizal types, and biomes are largely unknown. Here, we collected six key traits – namely root diameter (RD), specific root length (SRL), root tissue density (RTD), root C content (RCC), root N content (RNC), and root C:N ratio (RCN) – of first- and second-order roots of 306 species from 94 sampling sites across China. We examined the covariation in root traits among different plant growth forms, mycorrhizal types, and biomes using the phylogenetic principal component analysis (pPCA). Three independent dimensions of the covariation in root traits were identified, accounting for 39.0, 26.1, and 20.2% of the total variation, respectively. The first dimension was represented by SRL, RNC, RTD, and RCN, which was in line with the root economics spectrum (RES). The second dimension described a negative relationship between RD and SRL, and the third dimension was represented by RCC. These three main principal components were mainly influenced by biome and mycorrhizal type. Herbaceous and ectomycorrhizal species showed a more consistent pattern with the RES, in which RD, RTD, and RCN were negatively correlated with SRL and RNC within the first axis compared with woody and arbuscular mycorrhizal species, respectively. Our results highlight the roles of plant growth form, mycorrhizal type, and biome in shaping root trait covariation, suggesting that root trait relationships in specific regions may not be generalized from global-scale analyses.

Phenotypic variability in the US upland cotton core set for root traits and water use efficiency at the late reproductive stage

“…Since WUE was not correlated with water use but was positively correlated with shoot weight, it could be that root traits that improve nutrient absorption to synthesize more shoot dry matter might be positively correlated with WUE. Our results are supported by previous reports on the multifaceted role of fine roots in plant resource acquisition, net primary production, and adaptation to environmental changes (An et al., 2022; Diaz et al., 2004; McCormack et al., 2014, 2015). According to the root economics spectrum (RES) hypothesis, roots with an acquisitive strategy are characterized by a thin diameter (i.e., fine roots) (An et al., 2022).…”

“…Our results are supported by previous reports on the multifaceted role of fine roots in plant resource acquisition, net primary production, and adaptation to environmental changes (An et al., 2022; Diaz et al., 2004; McCormack et al., 2014, 2015). According to the root economics spectrum (RES) hypothesis, roots with an acquisitive strategy are characterized by a thin diameter (i.e., fine roots) (An et al., 2022). Taken together, our results emphasize the importance of fine roots in enhancing the WUE of cotton.…”

Are absorptive root traits good predictors of ecosystem functioning? A test in a natural temperate forest

“…More details of these traits can be seen in Table S2. Previous studies have found that RCN was closely related to root tissue density (RTD) at both the species and community level (Wang et al ., 2018; An et al ., 2022). Therefore, to analogize with leaf traits, we considered RCN here instead of RTD, even which is the more commonly used RES trait.…”

Root Respiration–Trait Relationships Are Influenced by Leaf Habit in Tropical Plants

“…Notably, only plants with arbuscular mycorrhizal associations were examined in this study due to the tropical woody plants are dominated by arbuscular mycorrhizal species [54,55]. However, root resource acquisition strategies are also influenced by mycorrhizal type [23,56]. Mycorrhizal type can impact the relationships between fine root chemical (e.g., RNC) or morphological (e.g., SRL) traits and root respiration [57].…”

“…How root systems impact plant growth and ecosystem processes is closely tied to the interplay among fine root chemical, morphological, and physiological traits [3]. Although root respiration shapes nutrient acquisition and plays a vital role in the RES [18,19], previous studies testing the RES hypothesis predominantly focused only on chemical and morphological traits, given the relative difficulty of measuring respiration [20][21][22][23]. But there are also several studies in grassland, temperate forest, and subtropical forest ecosystems that incorporate root respiration into the RES.…”