SPATIAL DISTRIBUTION, COMPOSITION AND STRUCTURE OF A THORNSCRUB IN NORTHEASTERN MÉXICO

Abstract

In this study we describe the forest structure using the tree spatial distribution in a Tamaulipan thornscrub (MET) area. We utilized a nearest neighbor approximation and computed the aggregation index (R), uniform angle index (W), segregation index (S), species mingling (Mi), diameter differentiation (Ti) and dominance (Ui), in order to provide information that can be used in ecological restoration. Our study was located in an area of MET without vegetation removal and no record of productive activity at least in 28 years. For the forest inventory we stablished four squared plots of 1600 m2 (40 x 40 m) in which every tree and shrub (d0.10 ≥ 5cm) were located and determined species scientific name; besides, we measured the crown diameter (m), total height (m), distance (m) and azimuth to the center of each plot. The main results were, for aggregation index R₁ = 0.76, R₂ = 0.43, R₃ = 0.50 and R₄ = 0.83; uniform angle index Wi₁ = 0.57 ± 0.20, Wi₂ = 0.61 ± 0.24, Wi₃ = 0.59 ± 0.23 and Wi₄ = 0.52 ± 0.20; segregation index S₁ = 0.24, S₂ = 0.68, S₃ = 0.66 and S₄ = 0.04; species mingling Mi₁ = 0.73 ± 0.24, Mi₂ = 0.47 ± 0.35, Mi₃ = 0.52 ± 0.34 and Mi₄ = 0.84 ± 0; diameter differentiation Ti_1,3,4 = 0.49 ± 0.35 and Ti₂ = 0.48 ± 0.36; and diameter dominance U₁ = 0.32 ± 0.15, U₂ = 0.20 ± 0.13, U₃ = 0.24 ± 0.14 and U₄ = 0.22 ± 0.12. Hence, results based on aggregation and segregation indices show a random distribution in plots 1 and 4, and a clumped distribution in plots 2 and 3. According to the uniform angle index, we can conclude that this area has a regular distribution in all plots. The analysis of species mingling showed interspecific competition in plots 1 and 4, while in plots 2 and 3 there is an intraspecific competition. Finally, the diametric dominance and differentiation showed homogeneous distribution in all plots. Based on these results, we recommend that the plot 4 can be taken as a reference site because it showed special characteristics that could be replicated on degraded lands.