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Tree Age Mediates Plant-Soil Relationships
The relationships between growth and soil are mediated by plant age. Stem growth and wood anatomy of 9-year-old trees and 2-year-old saplings of Enterolobium contortisiliquum, “tamboril” growing in eutrophic and oligotrophic soils were compared. Soil conditions have influenced the growth and variations in wood anatomical features.
Environmental conditions influence the biological processes involved in plant development, thus affecting the final growth. Variations in secondary growth of woody plants can be an answer to gradients in resource availability. Identifying the influence of environmental conditions in wood structure and function of trees growing under different conditions is of particular interest because environment directly affects xylem cell differentiation, i.e. enlargement and secondary wall thickening, and, consequently, the efficiency of water and nutrient transport from roots to leaves .
Studies of plant-soil relationships can gain more insights when comparing individuals of different ages since structure and function of the conducting system in plants change during ontogeny. The nutrient acquisition depends on the age and size of the individuals . Thus, investigations of anatomical traits of the xylem could explain why trees of different ages develop different strategies for nutrient acquisition .
Enterolobium contortisiliquum (Vell.) Morong (Fabaceae), known as tamboril, timboúva, orelha-de-negro, and pacará earpod tree, is a tree species spreading in various regions of Brazil , such as Caatinga, Cerrado, and Atlantic Forest, and exhibits a good adaptation to different conditions. Because of its fast growth, this species can be used to facilitate the natural regeneration of woody shrubs in reforestation and for phytoremediation of oil-contaminated soils . Previous observations have detected that tamboril trees growing in eutrophic and clay soil reached a larger stem diameter than those in oligotrophic and sandy soil (personal communication V. L. Engel). Due to the importance of this species for the recovery of degraded areas and abandoned agricultural lands, it is necessary to understand its biological strategies in response to soil restrictions.
In this study, we analyzed stem growth and wood anatomy of tamboril by comparing 9-year-old trees and 2-year-old saplings (Figure 1), growing in eutrophic and oligotrophic soils from areas of semi-deciduous seasonal forest, nearby Botucatu (22°52’32” S and 48°26’46” W), São Paulo State, Brazil. These areas belong to a geographic region of the Cerrado Domain . We expected that the influence of soil type on tree growth reflects changes in wood anatomical features.
Taking all into consideration, this review presents the relationships between growth and soil in tamboril. Also, it summarizes the wood anatomical variations in response to soil conditions where the plant grew. In addition, we discussed how the responses to soil type are mediated by tree age.