LATENT COMPETITION AND THE INDIVIDUAL EFFECT OF MICROCLIMATIC VARIABLES ON STEM TREE GROWTH IN THE CENTRAL AMAZON

Abstract

Background: The dynamics of the forest can be conditioned by microclimatic variation and competition for resources, which results in physiological changes that interfere with the pattern of species development. This study evaluated the individual effect of microclimatic variables and competitive status on stem diameter growth of terra-firme tree species in Central Amazonia. The individual stem growth of 33 trees of seven species was measured over four years. To quantify the level of competition of trees in relation to their respective competitors, a widely used distance-dependent competition index was correlated with the increase in tree diameter. For each competitor, the diameter (cm) and distance between the stems in relation to the target tree (m) and the crown diameter (m) were measured. 

Results: The individual growth pattern varied over time with an average of 0.15 mm month^-1 and precipitation and soil water content were the main factors responsible for growth in most species. Variation in vapor pressure deficit (VPD) (minimum and average) led to changes in diameter growth. The maximum VPD and temperature (minimum and maximum) did not influence the growth in diameter. There was no significant effect of the competition among trees on the increment in diameter, which was ascribed to the high population (latent competition).

Conclusion: These results indicate that changes associated with VPD can limit photosynthetic capacity, especially in drier periods and at higher temperatures. High tree density (338 stems/ha) in the Amazon creates a "latent competition" environment.  Limited resources affect all trees similarly, masking the impact of individual competitors.