Mortality, recruitment and growth of the tree communities in three forest formations at the Panga Ecological Station over ten years (1997-2007)

Abstract

The area evaluated in this study was a continuous stretch comprising three vegetation formations: gallery forest, semideciduous seasonal forest and cerradão (woodland savanna). The aim of this study was to examine the tree community dynamics in a forest gradient-from gallery forest to cerradão-at Panga Ecological Station, in the city of Uberlandia, located in the state of Minas Gerais, Brazil. The study was based on data from a previous inventory of the continuous forest conducted in 211 permanent 10 × 10 m sample plots in eight parallel transect running perpendicular to Panga Creek. Trees with a diameter at breast height ≥ 4.77 cm were sampled in 1997, 2002 and 2007. With the exception of the cerradão, there was a net reduction in tree density over the studied period of ten years, because mortality rates were higher than the recruitment rates. The basal area increased during the period of the study, especially at cerradão. The mean mortality rate in the studied area was 2.64%.yr , respectively. In general, mortality rates and recruitment rates have increased during the two successive periods of measurement and showed an imbalance in favor of mortality for the semideciduous seasonal forest and the gallery forest. This fact, added to the low density and high basal area, suggest that there was a process of thinning in the tree community. However, at cerradão, there was an imbalance in favor of recruitment, with a consequent increase in density and basal area, indicating that the cerradão is in a construction phase, which was further favored by a decrease in the occurrence of fire and other anthropogenic disturbances. When the turnover rates are taken into consideration, the global dynamics of the study area over the ten years evaluated can be expressed as cerradão > semideciduous seasonal forest > gallery forest.

Post-fire dynamics of the woody vegetation of a savanna forest (Cerradão) in the Cerrado-Amazon transition zone

“…In the present case, then, the savanna forest may still be at an "initial" stage of the silvigenetic cycle, characterized by positive net changes in density, for example (see Marimon et al 2006;Machado & Oliveira-Filho 2010;Oliveira et al 2014). This may also be related to the hyperdynamics typical of the forests of this region ) and the high density of large pioneer species with a short life cycle, such as Tachigali vulgaris.…”

“…As the forest formations in the study region -the Amazon-Cerrado transition zone -are encroaching the savanna formations (Marimon et al 2006), the community will tend to accumulate biomass. An increase in basal area of the savanna forest of the study area would thus be expected Marimon et al 2014;Oliveira et al 2014).…”

Woody encroachment and its consequences on hydrological processes in the savannah

“…[30,33]). Fire suppression or decreasing fire frequency have been reported as the main explanation for woody encroachment in Cerrado vegetation across Brazil [29][30][31][32][33]64], with frequent fires, regardless of season, been shown to reduce woody biomass [65]. Changes over time in density and TBA in our study differed: TBA increased in the cerradão plots at similar rates as those of the cerrado stricto sensu, but density stabilized around 2000 ind ha 21 , corresponding to a basal area around 23 m 2 ha 21 , and after that, mortality equalled recruitment, resulting in no significant changes in density over 5 years.…”

Estrutura Da Comunidade Arbórea E Características Edáficas De Um Fragmento Urbano

“…No entanto, florestas ocorrentes em gradientes de fertilidade, inundações periódicas e declividade do solo podem aumentar a heterogeneidade local (CARDOSO; SCHIAVINI, 2002) e possuir mais do que 1500 indivíduos (RODRIGUEZ-SOUZA et al, 2015). Cerradões, por exemplo, tendem a possuir maior adensamento de indivíduos, enquanto que florestas estacionais tendem a ter maior quantidade de árvores de maior porte, o que reduz a densidade por hectare (OLIVEIRA et al, 2014).…”