Abstract:
We studied factors that restrict colonization of
grassland by Quercus durata Jeps., an oak commonly found in
chaparral on serpentine soils. The study site contained a chaparral/
grassland border that had been stable for at least 50 years.
Monitoring of acorns planted in the chaparral understory and
grassland revealed that, although initial seedling emergence was
similar in the different sites, seedling survival was much higher
in the chaparral. No seedling in the open grassland survived
beyond the third year of the study, while 25 percent in the
chaparral understory were still alive at the end of 6 years. The
differences in survival could not be explained by differences in
animal activity and herbivory. Rather, the high solar radiation
load on seedlings in the grassland appeared to play a major role
in mortality. Experimental shading of seedlings in the grassland
with light shade cloth increased seedling survival.
