STEM-GROWTH PERIODICITY OF TREES IN A TROPICAL WET FOREST OF COSTA-RICA

Five of the 8 species studied in a well-drained habitat showed periodic behavior. Their seasonality was mainly annual, but 2 of 4 Pentaclethra macroloba had semiannual rhythms. The periodic trees were well synchronized with one another and with the climatic cycle. All exhibited growth cessations that were associated with the drier portion of the year. Each of the 2 semiannual Pentaclethra underwent an additional interruption during the wet season. All trees monitored in a swamp displayed intermittent stem growth. Only 1 or possibly 2 trees (both Pentaclethra) had annual periods. The remainder showed cycles that were either longer or shorter than a year. The Pentaclethra were fairly well synchronized with one another and with the drier time of year. Cambial activity of the synchronized trees was inversely related to day length, insolation angle and air temperature at both sites. -from Authors