Interspecific coordination and intraspecific plasticity of fine root traits in North American temperate tree species.

Cornelia M Tobner,Christian Messier,Alain Paquette

doi:10.3389/fpls.2013.00242

Cornelia M Tobner, Christian Messier + Show 1 more

Open Access

https://doi.org/10.3389/fpls.2013.00242

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Abstract

Fine roots play an important role in nutrient and water absorption and hence overall tree performance. However, current understanding of the ecological role of belowground traits lags considerably behind those of aboveground traits. In this study, we used data on specific root length (SRL), fine root diameter (D) and branching intensity (BI) of two datasets to examine interspecific trait coordination as well as intraspecific trait variation across ontogenetic stage and soil conditions (i.e., plasticity). The first dataset included saplings of 12 North American temperate tree species grown in monocultures in a common garden experiment to examine interspecific trait coordination. The second dataset included adult and juvenile individuals of four species (present in both datasets) co-occurring in natural forests on contrasting soils (i.e., humid organic, mesic, and xeric podzolic).The three fine root traits investigated were strongly coordinated, with high SRL being related to low D and high BI. Fine root traits and aboveground life-strategies (i.e., relative growth rate) were weakly coordinated and never significant. Intraspecific responses to changes in ontogenetic stage or soil conditions were trait dependent. SRL was significantly higher in juveniles compared to adults for Abies balsamea and Acer rubrum, but did not vary with soil condition. BI did not vary significantly with either ontogeny or soil conditions, while D was generally significantly lower in juveniles and higher in humid organic soils. D also had the least total variability most of which was due to changes in the environment (plasticity). This study brings support for the emerging evidence for interspecific root trait coordination in trees. It also indicates that intraspecific responses to both ontogeny and soil conditions are trait dependent and less concerted. D appears to be a better indicator of environmental change than SRL and BI.

Highlights

The search to understand the effects of species on ecosystem functioning has brought forward the functional role of various traits
We examined interspecific and intraspecific variation across contrasting soil conditions as well as with ontogenetic stages for specific root length (SRL), D and branching intensity (BI)
INTERSPECIFIC TRAIT COORDINATION (CG) In the common garden, fine root traits were highly coordinated across species, especially SRL3 and D3 (Table 2)

Summary

Introduction

The search to understand the effects of species on ecosystem functioning has brought forward the functional role of various traits. Fine root samples of different or even the same species may include varying numbers of root orders Fine root traits such as specific root length (SRL), diameter, root length density as well as nitrogen, lignin, non-structural carbohydrate, and cellulose concentrations have been found to systematically change with root order (Pregitzer et al, 2002; Guo et al, 2004; Wang et al, 2006). Such morphological and physical changes with root order translate into potentially large differences in functional properties such as water uptake (Rewald et al, 2011), respiration (Jia et al, 2011) or fine root mortality (Wells et al, 2002). This approach attempts to control for confounding factors, comparisons across studies are restricted due to varying numbers of root orders included (see for example Yu et al, 2007; Comas and Eissenstat, 2009; Alvarez-Uria and Körner, 2011; Chen et al, 2013)

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