POPULATIONAL STRUCTURE AND SPATIAL DISTRIBUTION OF Theobroma speciosum Willd. Ex Spreng IN NORTHERN OF MATO GROSSO STATE

摘要

Understanding the structure and spatial distribution of tree species is necessary to predict the spatial variation of successional, genetic and ecological processes of a forest ecosystem. The present study assessed the population structure and the spatial distribution of Theobroma speciosum (cacauí) in three urban forest fragments located at Alta Floresta (C/E Park with sampled area of 6.72 ha, J Park, with 3.92 ha and Zoobotanical Park with 15.84 ha of sampled area) and at Juruena National Park -PNJu (3.2 ha) in the North of Mato Grosso State. Three hundred and twenty-three individuals of Theobroma speciosum were sampled, 50 in the C/E Park (7.44 ind. ha -1 ), 32 in J Park (8.16 ind. ha -1 ), 76 in the Zoo-botanical Park (4.79 ind. ha -1 ) and 165 in PNJu (51.56 ind. ha -1 ). The lower density of individuals found in the urban parks may be associated with the fragmentation process, since there were no positive relationships of density and the number of individuals with the sampled area. Besides, the highest density was found at PNJu, which is a continuous forest in a conservation unit subjected to no recent human intervention. The urban forest fragments (except for the Zoo-botanical Park) have presented the smallest amount of individuals in the inferior diameter (0-5cm) and the lowest height classes (0-5m) when they were compared to the structure found at PNJu. Such difference must regard the smaller area of the C/E and J Parks and the consequent more intense edge effect that have affected forest regeneration. The distribution pattern of individuals in all populations was clumped. These results show that the species is susceptible to fragmentation due to isolation, since it presents self-incompatibility and limited zoochoric dispersion.