The aim of this work was to study vegetation groupings and their dynamics in
remnant of Subtropical Seasonal Forest, of nearly 560 ha, located at the Instruction
Field of Santa Maria, in Santa Maria municipality, RS. In the study area, 14 blocks of
20x100m were marked, distributed into four bands, distant 500m from each other.
Each block was divided into portions of 10mx10m, resulting in 280 portions, in which
was evaluated the adult vegetation, represented by individuals with CBH≥30cm.
Inside these blocks, 70 portions were raffled for evaluation of understory vegetation
(3,14cm≤CBH<30cm), seedling bank (h≥30cm and CBH<3,14cm) and seed rain. In
the 70 raffled portions, it was also evaluated the alternation degree, land slope and
the light intensity. The occurred changes in the forest shrubby-arboreal component
were studied based on the structure, ingress, mortality and increment (for the
seedling bank) during the period from 2008 to 2010. In a similar way, the seed rain
was monitored from October 2008 to October 2010, when the absolute density and
the seasonality of seed production were evaluated. In this study, the results were
presented in four chapters: the aim of the first one was to determine the grouping
analysis and the occurred changes in the floristic composition and vegetation
structure represented by CBH≥30 cm, being verified that the area presents two
characterized formations, mainly, by the forest conservation degree, named: -
Secondary Forest in Intermediate Stage (SFIS) of succession, represented by bigger
exploration in the past due to the easy access to the area; and – Secondary Forest in
Advanced Stage (SFAS) of succession, occurring in a forest area characterized by a
more accentuated slope, what made timber exploitation difficult, being therefore, in a
more advanced stage of succession. The second chapter dealt with the occurred
changes in the understory vegetation (3,14cm≤CBH<30cm) for the two floristic
groups observed in the grouping analysis. In the third chapter, it was presented the
natural regeneration dynamics, represented by the seedling bank (h≥30cm e
CBH<3,14cm) and the seed rain. Finally, in the fourth chapter, it was carried out a
general analysis of the most abundant species’ dynamics in each class of vegetation,
in the two observed groups in the forest. The results indicated some differences in
the floristic composition and vegetation dynamics, in each group. In one hand, the
SFIS presented the highest value of importance to the heliophilous species and the
highest dynamics, mainly, in the individual’s mortality. On the other hand, the SFAS
presented heliophilous and sciaphilous species as the most important as well as the
highest equilibrium in relation to ingress and mortality rates. The seed rain seemed
an efficient mechanism of natural regeneration and most of the observed species in
the forest’s arboreal vegetation presented production seasonality. In general, the
remnant of forest represents an important preservation area for the characteristic
species from Subtropical Seasonal Forest and its maintenance becomes important to
keep the quality of soil in the area besides of playing important environmental
services to the region.
