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

Spatial and temporal heterogeneity effects on seedling growth and establishment in four Quercus species
mass to leaf area. Because LMA depends on both the particular species and incident
light (Aranda et al., 2004; Poorter et al., 2009), linear regressions between LMA and
light availability (Global Site Factor, GSF) were calculated for each species in order to
obtain accurate estimates of LMA in relation to GSF (r 2 > 0.40). LMA and the leaf area
estimates were used to calculate leaf dry mass per seedling.
At the end of the growth season (July 2007), dead seedlings were harvested for
calculation of stem and leaf dry weight. No significant differences in spring aerial
seedling biomass were found between surviving seedlings after summer and dead
seedlings. Therefore, seedling biomass of dead seedlings could be assumed as
representative of the population. In those seedlings measured on both sampling dates
(beginning and end of the growth season) stems relative growth rate (RGR t ) and
aboveground relative growth rate (RGR a ) was calculated as:
(1) RGR = (lnM 2 – lnM 1 ) / t ,
were M 1 and M 2 were biomass (aboveground or stems) at the beginning and at the
end of the growing season, respectively, and t is the time interval between the two
measurements. Aerial leaf mass fraction (LMF a ) was calculated at the end of the
growth season (t 2 ) as:
(2) LMF a = M l / M t ,
were M l was leaf mass and M t was total aboveground biomass, both estimated at t 2 .
Environmental variables (light availability, soil moisture and herb production)
were measured at each node. For simplicity, herb prodution was named as
“environmental variable” because it was studied as an external factor that may
influence seedling growth and establishment. Light availability was estimated via the
Global Site Factor (GSF) (Rich, 198), using hemispherical photographs taken with a
Coolpix camera fitted with an FC E8 fisheye lens, both from Nikon (Tokyo, Japan), in
the spring of 2007. Photograhps were processed with the software Hemiview Canopy
Analysis v. 2.1 (Delta‐T, Cambridge, UK). Soil moisture was measured as the volumetric
content of water at each sampling point on a monthly basis from February to
September 2007. Measurements were made with a TDR (Model 100, Spectrum
Technologies, Inc., Plainfield, IL, USA) fitted with 20 cm long rods ─by exception, the
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