Establecimiento de cuatro especies de Quercus en el sur de la ...

Capítulo 4
all non‐destructive stem volume measurements were taken as described above.
Seedlings were placed in individual bags with moistened filter paper and kept in a
portable icebox until taken to the laboratory. Once in the laboratory, harvested
seedlings were oven‐dried at 70° C for a minimum of 48 hours, and subsequently
weighed to obtain dry mass of the stem fraction. Linear regressions between stem
volume and stem dry mass were calculated per species and sampling date (R 2 > 0.80),
and were used to estimate stem mass from the non‐destructive estimate of stem
volume (Pérez‐Ramos et al., 2010). A linear regression per species may suffice, since in
a previous nursery‐experiment using acorns from the same provenance we found no
differences in wood density across seedlings from different mothers within each
species (VGR unpublished data).
To estimate leaf mass from the non‐destructive measurements taken in the
field, leaves were harvested from an additional fifteen randomly‐selected seedlings
per mother tree at the end of the growing season (June 2007), since leaf traits are
known to be related to both species and incident light (Aranda et al., 2004; Poorter et
al., 2009), but might be as well influenced by mother tree (VGR unpublished data).
Measurements were taken from one expanded leaf at medium height on each
seedling. All leaves were scanned (HP Scan‐jet 6300c), oven‐dried at 70º C for a
minimum of 48 hours, and subsequently weighed to obtain dry mass. Leaf area for
each harvested leaf was calculated using image analysis software (Image Pro‐plus 4.5;
Media Cybernetics, Inc), and specific leaf area (SLA) was calculated dividing leaf area
by leaf dry mass. Average SLA values per mother tree and light category combination
were calculated from the harvested leaves (R 2 > 0.40). Leaf mass was calculated as
estimated leaf area divided by SLA.
Aboveground biomass at the end of the first growing season was calculated as
the sum of the estimated stem and leaf masses. Aerial leaf mass fraction (LMF a ) was
also calculated as the ratio between leaf mass and estimated aboveground biomass.
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