Elevational change in woody tissue CO2 efflux in a tropical mountain rain forest in southern Ecuador
Alexandra Zach (1, 2), Viviana Horna (1) and Christoph Leuschner (1)
1. Plant Ecology, Albrecht-von-Haller Institute for Plant Sciences, University of Göttingen, Untere Karspüle 2, 37073 Göttingen,
Germany / 2. Corresponding author () / Received September 19, 2006; accepted June 25, 2007; published online October 15, 2007
Summary
Much uncertainty exists about the magnitude of woody tissue respiration and its environmental control in highly diverse tropical
moist forests. In a tropical mountain rain forest in southern Ecuador, we measured the apparent diurnal gas exchange of stems
and coarse roots (diameter 1–4 cm) of trees from representative families along an elevational transect with plots at 1050,
1890 and 3050 m a.s.l. Mean air temperatures were 20.8, 17.2 and 10.6 °C, respectively. Stem and root CO2 efflux of 13 to 21 trees per stand from dominant families were investigated with an open gas exchange system while stand
microclimate was continuously monitored. Substantial variation in respiratory activity among and within species was found
at all sites. Mean daily CO2 release rates from stems declined 6.6-fold from 1.38 µmol m–2 s–1 at 1050 m to 0.21 µmol m–2 s–1 at 3050 m. Mean daily CO2 release from coarse roots decreased from 0.35 to 0.20 µmol m–2 s–1 with altitude, but the differences were not significant. There was, thus, a remarkable shift from a high ratio of stem to
coarse root respiration rates at the lowest elevation to an apparent equivalence of stem and coarse root CO2 efflux rates at the highest elevation. We conclude that stem respiration, but not root respiration, greatly decreases with
elevation in this transect, coinciding with a substantial decrease in relative stem diameter increment and a large increase
in fine and coarse root biomass production with elevation.
Keywords:
altitudinal transect, coarse root respiration, infrared gas analysis, stem respiration, temperature dependence.
