Stomatal parameters (stomatal density, stomatal index and stomatal
conductance) have been widely used to study vegetation response to long-term
CO2 change, mostly in the Northern Hemisphere. We tested
the applicability of the methods and interpretations to Australian desert
vegetation, by using Eremophila deserti A.Cunn.
(Myoporaceae) leaves. Subfossil samples dated at 7500 years before present and
3700 years before present from Leporillus species
(stick-nest rat) middens from the Flinders Ranges were compared with herbarium
and modern samples from the area. Stomatal density and stomatal conductance
are problematic in their application to this species, probably because of the
effect of the moisture regime on epidermal cell size. Stomatal index, which
takes some account of independent variations in cell size, did allow the
differentiation of long-term trends. In contrast to most other studies, these
trends show an increase in stomatal index with increasing
CO2, particularly over the last century. From 7500
years before present until about 1950, it is unclear whether
CO2 was the most influential among a complex set of
factors including different aspects of the moisture regime. In recent decades,
the influence of CO2, as demonstrated statistically,
accounts for most but not all the observed variation.
Stomatal parameters in nine species of Corchorus (Tiliaceae)
