Regeneração natural de uma floresta secundária sob manipulação de água e nutrientes no município de Castanhal, Pará.

Abstract

The objective of this síudy was evaluate the iirigation and of literfaü removai in seedlings in the ecological processes of growth, recruitment, mortaliíy and natural regeneration in a secondary forest in Northeastem Pará. The experiment used four randomized blocks each of which included a dry-season irrigation plol. literfall removai plot and control plot. The ecological processes of smalier plants than 1 cm of diameter and taller than 3 cm were accompanied through monthly mensurations in 4 subplots oflmxlm(l m2), distributed randomly within the central portions of each plot, totaling 48 subplots. The experiment was monitored over the period of one year {september/2001 to august/2002), after the installation of the treatments. Irrigation was only applied during the dry season (september at december/2001 and july and august/2002), while the literfall remova! proceeded throughout the entire year. To study natural regeneration dynamics in the studied treatments, we analyzed average rates of relative growth (TCR), recruitment (TI), mortality (TM) and natural regeneration (TRN). Results showed that TCR, TI and TRN were seasonal and strongly influenced by rainfall, while TM in literfall removai and control plots, presented a constant pattem over time. Irrigation in the dry season increased recruitment and decreased mortality of seedlings, however, during the rainy season the irrigated plots showed higher mortality and lower recruitment. Dead individuais were mostly found in the smallest size class (3-30 cm of height). This study revealed signiíicant dilierences in TRN among the treatments and in TCR, TI and TRN for the interaction between treatments and months.