Response of Salix nigra [Marsh.] cuttings to horizontal asymmetry in soil saturation


The objective of this research was to determine if localized morphological and physiological responses of Salix nigra [Marsh.] would reflect heterogeneous soil conditions, and if these changes would alter functioning at the whole-plant level. This experiment utilized split-root rhizotrons with two separate chambers, allowing for half of the root system of each plant to be flooded while the other half was allowed to drain. Plants from these heterogeneous treatments (F/D) were compared to plants in which the entire root system was flooded (F/F) or drained (D/D). Data on soil Eh, leaf area, and photosynthesis were recorded weekly. In situ root analysis compared pre- and post-treatment visible root surface area, root length, tortuosity (τ), fractal dimension (DF), and fractal lacunarity (Λ). Soil in the chambers of the F/F became anoxic by day seven, and remained so for the remainder of the study. Chambers of the D/D treatment and the F/D treatment remained oxic, regardless of whether or not the individual chamber was flooded, indicating that partial root system aeration may enhance amelioration of anoxic or reducing conditions. For the measures related to photosynthetic activity, only net photosynthesis demonstrated an overall treatment effect. Generally, root length and DF increased in response to flooding treatments, whereas Λ decreased. τ demonstrated an interactive effect wherein changes in roots within an individual chamber depended upon the flooding condition of the neighboring chamber. DF was found to be highly sensitive to flooding, even if the flooding did not result in measurable soil reduction. Overall these results indicate that S. nigra may demonstrate unique morphological responses to heterogeneity in soil saturation, but localized amelioration of anoxia, rather than reallocation predominates under mildly reducing conditions. © 2012 Elsevier B.V.

Publication Title

Environmental and Experimental Botany