Arboreal vegetation dynamics of the Estepa Seasonal Sabana in the Espinillo State Park

This study aim to evaluate the dynamics of the main tree species in a seasonal steppe savannah community, located in the Espinilho Park, Barra do Quaraí RS, throughout a period of eight years (2001-2009). From information on the dynamics, it is possible to assess changes in vegetation structure, based on mortality, recruitment and growth rates of its individuals. Permanent sample plots of 1 ha (100 x 100 m), divided into subunits of 100 m2 (10 x 10 m) were established for data collection. All trees with diameter at breast height (DBH) ≥ 10 cm were measured. Throughout the study period, 178 individuals from eight different species were recorded. The species Aspidosperma quebracho-blanco, Vachellia caven, Prosopis nigra and Prosopis affinis represent 82.58% of all individuals, which 54.49% comprise Prosopis genus only. Individuals were distributed in eight diameter classes, although 91.57% of them were from the first three diameter classes. An annual recruitment rate of 1.61% and a 0.70% mortality rate were observed. The average increase in DBH between the years 2001 and 2009 was 0.053 cm/year. The studied area showed a change in the dynamics with an annual recruitment rate greater than the mortality, indicating that the community is still growing.