Root traits across environmental gradients in Mediterranean woody communities: are they aligned along the root economics spectrum?
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Background and aims
Root traits play a critical role in plant resource-use strategies and ecosystem functioning, but there is great controversy regarding their identity and functionality in different dimensions of belowground functional variation. Here, we explored the level of covariation among a suite of key root traits (i.e. specific root length, root dry matter content, diameter and density) as well as between them and two aboveground traits related with plant function (leaf nutrient concentration and specific leaf area). We also evaluated whether these patterns of trait covariation were consistent at different spatial scales and organisational levels.
We collected fine root (< 2 mm) samples of 534 individuals (of 80 woody species) along a wide regional range of environmental conditions in southern Spain.
In general, strong correlations among most of the root morphological traits were found, supporting the existence of a ‘root economics spectrum’, as well as between root traits and the aboveground traits. However, root diameter was not completely aligned along this ecological axis, supporting the idea of a multidimensional spectrum of root traits. The main syndrome of root trait covariation was consistent at the different spatial scales and organisational levels. Soil nutrients and water availability were the main drivers of root trait variation.
Our results indicate that root trait variation is primarily aligned along a leading dimension related to resource economics. However, the distinct pattern of root diameter may indicate a multidimensionality of belowground traits that needs to be explored in greater depth.
KeywordsGrowth rate LMA Nutrients Root diameter Root tissue density SLA Specific root length Water availability
Specific root length (root length per unit of root dry mass)
Specific root area (root area per unit of root dry mass)
Root dry matter content (root dry mass per unit of water-saturated fresh mass)
Root tissue mass density (root dry mass per root volume)
This study was funded by the Spanish MEC coordinated project DIVERBOS (CGL2011-30285-C02-01 and C02-02), ECO-MEDIT (CGL2014-53236-R), RESTECO (CGL2014-52858-R), ECOMETAS (CGL2014-53840-REDT), the Life + Biodehesa Project (11/BIO/ES/000726) and European FEDER funds. We thank to Catherine Roumet the comments on this paper. Thanks are due to Emilio Retamosa and Vicky Schwarzer from the Cabo de Gata Natural Park, for field assistance and plant classification, and to the staff of IRNAS’s Analytical Service for chemical analyses of soil and plants. The N and C concentration of the leaves were obtained from the SCAI of University of Cordoba. Dr. David Walker revised the English.
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