Overstorey and understorey structure and dynamics in restoration forests

Author(s)

Flaviana Maluf de Souza

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2000-10-20
• Advisor: João Luís Ferreira Batista

Abstract

Overstorey and understorey structure and dynamics were studied in 10,9 and 5-year-old mixed native species reforestation area at Companhia Energética do Estado de São Paulo (CESP) reservoir margins. The study areas were planted using two different plantation strategies. In 9 and 5-year-old forests, the proportion of pioneer trees was about 50 %, while in 10-year-old forest it was 20 %. For the overstorey study (stem circunference at breast height &#8805; 15 cm), circunference at breast height, heigth and a crown position index were measured in 900 m2 permanent plots. For the understorey study (woody regeneration &#8805; 50 cm in height and stem circunference at breast height < 15 cm) six 1-m radius subplots were established in each overstorey plot, and all woody plant species were counted and identified. Canopy and herbaceous densities were determined using a vertical densitometer, in which cover presence/absence was assessed in points along transects. For the dynamics study, all the parameters were evaluated one year later. Shannon diversity (H') and eveness (J) indexes found for 10, 9 and 5-year-old forests were 3.03/0.84, 2.45/0.71 and 2.18/0.66, respectively. The mean basal area and height in 9-year-old overstorey were greater than 10-year-old forest. Greater mortality values for pioneer tree species and greater recruitment for early, late secondary and climax species, respectively, were observed in all sites, according to secondary succession theory. Herbaceous vegetation (Panicum maximum L.) persistence was related to the canopy opening in the dry season, varying with the degree of leaf shedding of some species. Woody regeneration density values were 6,500 individuals/ha in 10- year-old forest and 3,450 individuals/ha in 9-year-old forest. At the 5-year-old forest, no regenerating individuals were found in the first survey. From all tree species found in the regeneration survey, just one (Bastardiopsis densiflora (Hook et Arn.) Hassl.) seemed to have arrived from forest fragments or emerged from the soil seed bank. The proportion of trees of different ecological guilds in the restoration forests influenced the forest structure and dynamics. The 10-year-old site was the most similar to the natural forest (AU)