The Economics Spectrum Drives Root Trait Strategies in Mediterranean Vegetation

Extensive research efforts are devoted to understand fine root trait variation and to confirm the existence of a belowground root economics spectrum (RES) from acquisitive to conservative root strategies that is analogous to the leaf economics spectrum (LES). The economics spectrum implies a trade-off between maximizing resource acquisition and productivity or maximizing resource conservation and longevity; however, this theoretical framework still remains controversial for roots. We compiled a database of 320 Mediterranean woody and herbaceous species to critically assess if the classic economics spectrum theory can be broadly extended to roots. Fine roots displayed a wide diversity of forms and properties in Mediterranean vegetation, resulting in a multidimensional trait space. The main trend of variation in this multidimensional root space is analogous to the main axis of LES, while the second trend of variation is partially determined by an anatomical trade-off between tissue density and diameter. Specific root area (SRA) is the main trait explaining species distribution along the RES, regardless of the selected traits. We advocate for the need to unify and standardize the criteria and approaches used within the economics framework between leaves and roots, for the sake of theoretical consistency.

Root Structure and Function of Grapevine Rootstocks (Vitis) in Response io Salinity

Purpose Accessing freshwater resources becomes more complex in arid and semi-arid areas due to increased demands and declining water quality. Alternative water sources for agriculture such as saline and recycled water are currently being used. A better understanding of roots' response to irrigation with saline water is crucial for future agriculture in arid and semi-arid areas. Methods Three grapevine (Vitis) rootstocks were examined, and their roots' responses to salinity were studied. The rootstocks were planted in pots filled with sand and were grown in a commercial net house subjected to two salinity treatments: 10 mM and 30 mM NaCl (EC = 2 and 4 ds m-1, respectively). We measured root morphologic and anatomic properties at the end of the experiment. Results The specific root area increased in response to salinity due to reduced root tissue density. In addition, a reduction in the average root diameter also affected the specific root area by increasing the surface area to volume ratio. Plant biomass was allocated primarily to the shoot in all three rootstocks, reducing the root to shoot ratio. At the same time, the bottom part of the root zone was more affected by salinity. SO4 showed improved chloride and sodium exclusion, concomitant with a significant increase in its narrow roots' contribution to the surface area. Conclusion Narrow roots play a more prominent role in the acquisition of water and nutrients as salinity increases. Furthermore, a decrease in root tissue density and average diameter may contribute to salt exclusion from the roots.

Changes in Cupressus funebris and Cryptomeria fortunei Root Parameters in Landslides Caused by the Wenchuan Earthquake

Strong earthquakes (>7.0 Ms) critically change pedosphere, how the changed soils disturb tree root growth related to forest restoration is unclear globally. Therefore, a total of 15 plots were established in non-removed and landslide areas of Cupressus funebris and Cryptomeria fortunei plantations near northern section of fault belt of Wenchuan Earthquake (8.0 Ms) occurring in May 12, 2008, China. 112 and 114 small fine roots (≤2.0 mm in diameter) in all the plots were sampled in June and October of 2009. Mean tips length/length, area/ length, volume/length, mean tips length/biomass, specific root area and specific root length in 0.0–0.5, >0.5–1.0 and >1.0–2.0 mm diameters of roots were examined. This study revealed 1) root parameters did not respond to the landslide soils in the June, but did until the October, suggesting after many root tips and tiny roots die in winter, the roots lose sensitivity to a changing soil environment; 2) mean tips length/length and mean tips length/biomass decreased for Cupressus funebris, and increased for Cryptomeria fortunei as well as area/length and volume/length in the landslide soils, implying both species roots have different processes of forest restoration; 3) the smallest sized roots were more sensitive to the landslide soils than the other sized roots, which are better indicators for the forest restoration.

Does a fungal species drive ectomycorrhizal root traits in Alnus spp.?

Ectomycorrhizal (EcM) fungi contribute significantly to the shaping of short-root morphology, playing an important role in balancing the costs and benefits of root growth and nutrient uptake and exchange in boreal forests. We aimed to assess the effect of various EcM fungal taxa on root traits at seven sites dominated by grey alder, Alnus incana (L.) Moench, and black alder, Alnus glutinosa (L.) Gaertn. Mean root size, specific root length, specific root area, root tissue density, and root-tip frequency of EcM short roots were measured in EcM anatomotypes in relation to the effects of host species, soil moisture level, and nutrient status. Redundancy analysis revealed that anatomotype, alder species, site, and soil parameters (N, P, K, Ca, and Mg concentrations, pH, organic-matter content) accounted for 42.3% (p < 0.001) of the total variation in EcM root morphology. Variation decreased in the following order: anatomotypes (27.9%) > soil parameters and sites (19.9%) > alder species (5.1%). EcM fungus species had the primary influence on EcM short-root size. EcM roots of the dominant anatomotype, Alnicola spp., had the highest specific root length and specific root area in both alder species. Short-root morphology depends most strongly on the fungal taxa involved, which indicates that the type of mycobiont has an important influence on the functional properties of fine roots.