Como a massa foliar específica pode determinar as taxas de crescimento relativo de espécies arbóreas tropicais no início do desenvolvimento das plantas?
Amorim, João Francisco Ribeiro de Campos
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Changes in land use through deforestation and forest degradation have resulted in great losses of biodiversity and ecosystem functions and services and recognition of the importance of forests has resulted in several actions for their restoration. Plant growth rates can be strongly related to the leaf area per dry mass unit (SLA) which reflects the photosynthetic capacity per leaf area unit. However, other crown attributes such as the projection area of the crown, the surface area of the crown and the number of leaves can contribute to the photosynthetic capacity of the plants and thus influence the growth rates. The objective of this study is to evaluate the influence of SLA and the attributes of the crown on the growth rates of the plants of eleven tropical tree species reintroduced in a degraded area. For each species, five individuals were marked for growth monitoring over a year, measuring the total number of leaves, three crown measures (height, largest diameter of the crown and the orthogonal diameter to the largest diameter). From each individual, two expanded leaves were collected to estimate the SLA. The leaves were photographed, to estimate the leaf area, and weighed (fresh mass), and then left in the greenhouse, to estimate the dry mass. SLA is the ratio of the leaf area to the dry mass. Five models were evaluated to determine the influence of crown attributes on the relationship between SLA and the growth rates in height of the plants: (I) - considering only the SLA; (II) - AMF × SLA; (III) - CPA × SLA; (IV) - CSA × SLA and (V) - SM. The choice of models was made according to the corrected Akaike criterion. Model III, the relationship between RGR and SLA x CPA, was the one that best explained the growth rate of individuals, followed by model IV, showing that the larger the leaf area, the crown projection area and the crown surface area, the higher the relative growth rate of the species. In addition, model V showed that large seed plants produce small CPA and CSA, compromising the RGR.
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