The drainages chosen for the willow leaf beetle study all support long
term populations of C. aeneicollis. Some drainages run east-west
while other run north-south. All originate in high alpine habitats well
above treeline. The map (in prep.) illustrates the orientation and elevation
gradient for the 4 major drainages surveyed in the study.
Salix Foliage Air Temperature, Relative Humidity, and
Precipitation. The physiological temperature for small-bodied
exotherms such as willow leaf beetles is nearly always at or above the
ambient air temperature, with solar radiation as an additional heating
factor in some situations. In order to analyze and predict the effects
of elevation, air temperature, and climate change on the willow beetle
system, we needed to monitor air temperatures and precipitation in the
approrpiate microhabitats at the various study sites. This has been accomplished
using data sets derived from different monitoring efforts:
- 1981-present precipitation data and standard air temperatures
Air temperatures and snow accumulations (precipitation) have been monitored
since the early 1980's in Big Pine Creek, Bishop Creek (South Lake and
Sawmill stations), Rock Creek (Rock Creek Lake) and many other areas
in the Eastern Sierra. These data are available from the California
Data Exchange Center (CDEC) at the web site Locator
tool for finding weather stations and data (California Department of
Water Resources) The map function at site can be used to locate
the dozens of stations in the Owens Valley and in the Eastern Sierra,
and to retrieve data as far back as 1902. In many cases precipitation
data is available as well. The historical data is presented along with
the long term average for the site, which makes it relatively easy to
fill in missing values by extrapolation from adjacent sites. In this
way a continuous record of precipiation has been generated for the South
Lake site (see South Lake precip excel
file).
- 1998-present Salix foliage air temperatures In 1998
we began deploying air temperature dataloggers at sites spanning the
beetles' distribution in several drainages (see excel file for a catalog
of logger sites). Coin-sized temperature loggers were placed in
Salix foliage about 1/3 of the distance inside the crown of foliage,
which was .5 to 1.5 m above ground depending on the site. Loggers were
shaded from direct sunlight by suspending them inside white plastic
cups hanging from a small branch. Loggers were programmed to record
temperature on an hourly basis. Data has been downloaded once or twice
annually to create continuous folaige air temperature records, and dataloggers
replaced as needed. Raw data files have been archived in the WMRS data
center, and a synopsis of the data is available in excel format for
Big
Pine Creek, Bishop
Creek, and Rock
Creek. A close examination of the logger data also reveals the time
of snow burial and snow melt for the logger each winter, dates which
have been recorded in a separate file (see South
Lake precip. excel file).
- To date, we have not measured Relative Humidity at
the study sites. However, given the strong association between Chrysomela
species and mesic habitats, this is probably an important variable to
measure. We hope to employ temp/RH dataloggers in future deployments.
C. aeneicollis abundance survey results We
have carefully resurveyed the same sites several times each year since
1998. The basic protocol is to relocate survey sites using GPS, and then
to make two 5 minute counts, using a handheld counter. Adults, larvae,
pupae, and new adults are counted separately. Data are recorded in an
excel file (not yet available here). |