Richmond-Sierra Transect Field Trip, October 14, 2005
Goal: To observe how abiotic gradients, such as elevation, moisture, and temperature,
affect tree communities, students sampled tree diversity as they traveled along the western slope
of the Sierra Nevada.
The Field Trip: In order to observe how abiotic gradients affect tree communities,
we took a field trip up the western slope of the Sierra Nevada mountain range. Elevation, moisture,
and temperature all change along this gradient. We drove from Richmond High School to Donner Pass
and stopped at three sites of different elevations:
- Miner's Ravine County Park in Placer County, 400 feet above sea level
- Rollins Reservoir, 2200 feet above sea level
- Pacific Crest Trailhead at Boreal, 7200 feet above sea level
At each site, we recorded longitude and latitude using a global positioning system receiver.
We sampled trees along two 50 meter transects. Every 5 meters along the transect, we randomly
picked a tree to identify by spinning a disk with an arrow. We looked in the direction of the
arrow for the closest tree greater than 10 centimeters in diameter, only sampling an individual
tree once. This method allowed us to easily sample many trees in a very short period.
Mrs. Robinson and Rafi watch as students spin the arrow for tree selection.
At the end of data collection at each site, we tallied the numbers of species for the site and
discussed what we observed.
Findings: We found that the number of conifer species increased with elevation, and that
richness, or the total number of species, decreased with elevation.
At the low elevation site at Miner's Ravine County Park (400 feet), we found several species
of oaks (blue oak, valley oak, and interior live oak). Other broadleaf trees were also found,
such as cottonwoods and walnut. Ghost pines were the only conifers at this site.
Ricardo and Elizabeth use sampling techniques to document the findings at the lowest elevation.
Ryan shows Yoshi and Jasmin where to record the longitude and latitude in their field notes.
The mid-elevation site at Rollins Reservoir (2200 feet) was dominated by Douglas firs and
ponderosa pines. In addition, we found some black oaks, and whiteleaf manzanita.
Students join Ryan to tally the data collected at Rollins Reservoir.
The highest point was at Pacific Crest Trailhead at Boreal (7200 feet). We found many lodgepole
pines, red firs, and white firs here. During our visit, we observed lodgepole pine seeds spiraling
in the sun after being blown from their cones by the wind. Broadleaf trees were entirely absent
from our samples.
After classroom discussion and data analysis, we decided that we should sample more sites to
confirm the pattern we observed.
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2004-2005 RHS activities
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