2005-2006 Richmond High School

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

Mrs. Robinson and Rafi watch as students spin the arrow for tree selection.
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.

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.

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.
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.

Students join Ryan to tally the data collected at Rollins Reservoir.
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.

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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