Abstract
The subtropical riverine forests present a variation in soil water availability throughout the year, following precipitation seasonality. The objective of this work was to evaluate the responses of Cordia americana to different light intensities combined with soil flooding. Seedlings were acclimated to light treatments, with full sun and shade conditions. Sun and shade plants were subjected to soil flooding during periods of 10 (short) and 30 (longer) days. After 10 days, flooded plants had a higher root dry mass accumulation and soluble sugars content, regardless of the light condition. Shade plants presented higher shoot soluble sugars content in relation to the sun plants. After 30 days, a higher shoot soluble sugar content was observed in sun and shade flooded plants. In addition, a higher root soluble sugar content was also observed in sun plants under flood. Periods of short flooding, characterized in subtropical forests as from 5 to 15 days, favor the growth of shade plants and the roots sugar accumulation, fact that can explain the species distribution. However, long periods of flooding may be associated with light environment plasticity, suggesting that the sun plants present a higher flooding tolerance, directly associated with the ability to maintain the sugar content.
Highlights
Changes in the rainfall seasonality and fluctuations of the water column in riparian forests result in a specific forest structure - with plants tolerant to conditions which they are exposed - associated with periods of drought or flood (ParolinThe flood events occurring in riverine forests generate different impacts on arboreal populations distributed in these areas, including morphological, anatomical and physiological changes (Kozlowski 2002)
The composition of tree species in riparian forests may be associated with the light environment and flooding intensity (Poorter 2001, Arieira et al 2016), and the satisfactory growth of some species in environments with low or high light associated to species plasticity depends on quick adjustment of their biomass allocation and physiological traits (Valladares and Niinemets 2008, Gaburro et al 2015)
The species of study, Cordia americana (L.) Gottschling & J.S.Mill. is a tree of the family Boraginaceae, with occurrence restricted to areas rarely or not flood in subtropical riverine forests (Budke et al 2010) and classified as early secondary and shade tolerant species (Villagra et al 2013a)
Summary
Changes in the rainfall seasonality and fluctuations of the water column in riparian forests result in a specific forest structure - with plants tolerant to conditions which they are exposed - associated with periods of drought or flood (ParolinThe flood events occurring in riverine forests generate different impacts on arboreal populations distributed in these areas, including morphological, anatomical and physiological changes (Kozlowski 2002). In riverine forests, the light may act as an environmental filter by selecting certain species and functional groups, setting a mosaic of occurrence of different tree species depending on the irradiance penetration more than on the frequency and flooding intensities (Valladares et al 2008, Giehl and Jarenkow 2008). The aim of this study is to determine variables indicative of flooding and light plasticity in C. americana by evaluating the pattern of soluble sugars accumulation and morphophysiological traits in response to changes in light environment and soil flooding. The hypothesis tested in this study is based on the occurrence of C. americana in the understory in riparian forest fragments indicating that the plants acclimated to shade will show faster growth and higher soluble sugars accumulation in relation to sun plants in situations of flooding, and these differences are more pronounced after a long period of flooding
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