Changes in tree density and species composition in a protected Trachypogon savanna, Venezuela

Changes were recorded in population and species density of a 3-ha permanent Trachypogon savanna plot, protected against fire and cattle grazing for 16 yr (1961-1977). This savanna is a grassland (mainly Trachypogon species), with scattered trees and groves. Under protection it is gradually changing into a denser arboreal community; trees in the grassland and in the groves increased 14.6- and 3.7-fold, respectively. In places, ironstone outcrops limit woody plant invasion and prevent the whole area from developing into a savanna woodland. Experimental explosions (using dynamite) in the ironstone outcrop led to the growth of trees in soil pockets formed in the artificial fissures.