Rooting big and deep rapidly: the ecological roots of pine species distribution in southern Europe

Abstract

Root properties can influence plant drought resistance, and consequently plant species distribution. Root structure strongly varies across biomes partly as a result of phylogeny. However, whether the spatial distribution of phylogenetically close plant species is linked to differences in root properties remains unclear. We examined whether root properties mediate the strong correlation between summer drought intensity and the spatial segregation of pine species native to southern Europe. For this, we compared the seedling root growth and structure of five ecologically distinct pine species grown in 360L rhizotrons for 19 months under typical hot and dry Mediterranean conditions. We studied the mountain and boreo-alpine pines Pinus sylvestris and Pinus nigra, and the Mediterranean pines Pinus pinaster, Pinus pinea and Pinus halepensis. Mediterranean pines formed deep roots faster than mountain pines, their shoots and roots grew faster and had higher root growth, especially P. halepensis, at low air temperature. By the end of the study, Mediterranean pines had larger root systems than mountain pines. Neither distribution of root mass with depth nor root-to-shoot mass ratio varied significantly among species. Across species, minimal annual rainfall to which species are exposed in their range related negatively to root growth but positively to specific root length and the time needed for roots to reach a depth of 40 cm. This study highlights the importance of root growth as a driver of pine distribution in southern Europe and suggests that rapidly producing a large, deep root system may be a key attribute for pines to colonize dry Mediterranean locations.

Production and turnover of mycorrhizal soil mycelium relate to variation in drought conditions in Mediterranean Pinus pinaster, Pinus sylvestris and Quercus ilex forests

“…thrives in mid-altitude Mediterranean areas characterised by hot and dry summers and less frequent frosts during the winter. Mediterranean P. pinaster grows roots faster and develops larger root systems than P. sylvestris, contributing to its greater capacity to colonise drier Mediterranean sites (Andivia et al, 2019). Indeed, forests dominated by P. sylvestris have suffered frequent episodes of droughtinduced dieback in its southernmost peripheral population (Galiano et al, 2010), whereas Mediterranean P. pinaster forests at the southern distribution limit have demonstrated a high plasticity in their growth responses to drought (Caminero et al, 2018).…”

Root distribution according to phenology in plantain cultivars (Musa AAB), Ecuador

“…It has also been observed that the root characteristics vary widely among plant species and these differences are due, in part, to adaptations to environmental conditions of plant habitats (ANDIVIA et al, 2019). On the other hand, species segregation along aridity and temperature gradients could be driven by differences in root architecture and growth (FRESCHET et al, 2017).…”

Ground-penetrating Radar as Phenotyping Tool for Characterizing Intraspecific Variability in Root Traits of Pinus Halepensis

“…Pinus pinaster, P. halepensis) (Andivia et al 2019). This variability correlates with the species' ecological niches and the intensity of drought stress present in their environments (Andivia et al 2019). However, there is still a lack of information on the variability of functional root traits at the intraspeci c level, which determines the e ciency of water acquisition by trees (Kirfel et al 2017).…”

“…Indeed, there is strong evidence for genetic variability among populations originating from distinct environments to tolerate water stress, which involves traits such as water-use e ciency (Voltas et al 2008), wood anatomy (Esteban et al 2010), biomass allocation (Chambel et al 2007), or use of water sources (Voltas et al 2015). Deeper and more developed root systems might also be related to the ability of Aleppo pine to cope with water de cit (Andivia et al 2019;Voltas et al 2015). As a result, root morphology may be a key characteristic to understand water use strategies and, consequently, drought resistance mechanisms in this species.…”