2 research outputs found
Drought and the interannual variability of stem growth in an aseasonal, everwet forest
Linking drought to the timing of physiological processes governing tree growth remains
one limitation in forecasting climate change effects on tropical trees. Using
dendrometers, we measured fine-scale
growth for 96 trees of 25 species from 2013
to 2016 in an everwet forest in Puerto Rico. Rainfall over this time span varied,
including
an unusual, severe El Niño drought in 2015. We assessed how growing
season onset, median day, conclusion, and length varied with absolute growth rate
and tree size over time. Stem growth was seasonal, beginning in February, peaking in
July, and ending in November. Species growth rates varied between 0 and 8 mm/year
and correlated weakly with specific leaf area, leaf phosphorus, and leaf nitrogen, and
to a lesser degree with wood specific gravity and plant height. Drought and tree
growth were decoupled, and drought lengthened and increased variation in growing
season length. During the 2015 drought, many trees terminated growth early but did
not necessarily grow less. In the year following drought, trees grew more over a
shorter growing season, with many smaller trees showing a post-drought
increase in
growth. We attribute the increased growth of smaller trees to release from light limitation
as the canopy thinned because of the drought, and less inferred hydraulic
stress than larger trees during drought. Soil type accounted for interannual and interspecific
differences, with the finest Zarzal clays reducing tree growth. We conclude
that drought affects the phenological timing of tree growth and favors the post-drought
growth of smaller, sub-canopy
trees in this everwet forest