DENDROECOLOGY OF Sebastiania commersoniana (Baill.) L.B. Sm. & Downs AND Hovenia dulcis Thunb. IN A DEGRADED AREA IN ALLUVIAL MIXED OMBROPHILOUS FOREST, SOUTHERN BRASIL

ABSTRACT

In a forest remnant of the Alluvial Mixed Rain Forest impacted by crude oil spill in the district of Araucaria in Paraná, Brazil, we conducted a dendroecological study of Sebastiania commersoniana (Baill.) L.B.Sm. & Downs (Euphorbiaceae) and the exotic species Hovenia dulcis Thunb. (Rhamnaceae). The study objectives were to evaluate the effect of the flooding area by dyke construction as way to decontamination petroleum and the meteorological factors in the tree diameter growth of both species. Wood samples were collected using increment borer, from two conditions, both on hydromorphic soils (Haplic Gleisol), but at two sites differing in the depth of the water table: SHT - temporary water saturation (Sebastiania commersoniana n=12; Hovenia dulcis n= 10) and SHP - Permanent water saturation (Sebastiania commersoniana n=6; Hovenia dulcis n= 0). Radial time series were developed and correlated with the meteorological data from the region. Results show that individuals of native species at both soil conditions experienced similar inter-annual growth patterns with decreasing trend over the years; differently individuals of exotic species, with increase of increment over the years. Individuals of SHP condition had lower rates of growth after the year of the spill, which shows that the flooding of the area by construction of dykes as attempt to decontaminate, affected the growth of individuals. The construction of dykes as attempt to decontaminate the area affected de individual growth. Precipitation showed a direct link with tree growth, only at sites with temporary water saturation. Moreover, minimum air temperature is a factor limiting the growth of Sebastiania commersoniana, showing that high temperatures stimulate growth, particularly at the early stages of the growth period while warmer months may depress the growth. Hovenia dulcis showed no significant correlation with temperature, but precipitation arises as crucial factor for growth, but the effect of soil saturation in the subsequent months may limit tree growth.

Keywords:
environmental contamination; dendrochronology; exotic species