|What's natural today may not be the norm in an
atmospherically altered future. If greenhouse gases affect
only certain tree species or clones, selection may favor the
tolerant ones, thereby changing the makeup of our forests.
microenvironment inside a stand affects the survival rates not
only of seedlings, but also of many other forest organisms.
Replacing one tree species or growth pattern with another could
change basic processes such as evaporation, transpiration, and
variations in diurnal temperature and humidity. Canopies
that are more or less dense will change the way light penetrates,
affecting how warm, cool, moist, or dry the forest floor is.
This will in turn affect surface-dwelling birds, mammals,
amphibians, insects, and even the below-ground microbial
To get a handle on the combined within-stand effects of
high CO2 and ozone on forest microclimates, researchers
are measuring the micrometeorology inside and outside individual
rings at the Forest-Atmosphere Carbon Transfer and Storage
(FACTS-II) Aspen FACE Experiment being conducted in northern
Wisconsin. By studying small-scale boundary layer processes,
scientists hope to make inferences about forest conditions under
increased greenhouse gas concentrations.
A micrometeorological monitoring network has been set up
to measure a variety of near-surface atmospheric and below-ground
variables that are critical for describing the dynamics of
Meteorological conditions are measured in five locations at the
Aspen FACE site: in four of the twelve rings [diagrammed
above] and at an ambient tower [below].
||Meteorological measurements in rings 1.2 (CO2
fumigation), 2.1 (Control), 3.3 (O3 fumigation),
and 3.4 (CO2 and O3 fumigation) at the
Aspen FACE site were gradually phased in during 1998, while
the ambient tower measurements were phased in during the
winter and spring of 1999. This data is available in
XLS (Microsoft Excel) format:
||The monthly averages of many of the meteorological
variables have been graphed: