North Tahoe Middle School took their science class outdoors last month to study sugar pines, the largest species of pine tree.

Sugar pines, well known for their exceptionally large cones, are being decimated in the Lake Tahoe area by bark beetles and a parasitic fungus known as White Pine Blister Rust. As part of their ecology course, the seventh graders worked with Headwaters Science Institute to design and conduct original experiments to learn more about why sugar pines are dying off and in what conditions they grow best.

The students planted naturally blister rust resistant sugar pine saplings around their school with Sierra Watershed Education Partnerships. A goal of the student-designed experiments was to discover the best places to plant sugar pine saplings to ensure their continued presence in the Lake Tahoe area.

---

---

Several groups of students were interested in what makes sugar pines susceptible to bark beetle infestation. They designed experiments to test how tree size, soil type, soil moisture, and tree species correlated with the number of bark beetle holes on a given tree. They found that larger trees with more visible sap on the bark had fewer bark beetle holes. These groups hypothesized that this correlation was because sap tastes bitter and may repel insects.

Larger trees might also be better at making sap during a drought than younger, smaller trees. The students also observed that fir trees around their school had much higher rates of bark beetle infestation than sugar pine trees.

---

---

Bearing in mind the big picture goal of learning the best places to plant sugar pine saplings, several groups collected data on soil nutrients, soil moisture, and sun requirements of trees in relation to their size and health. Their results indicated that sugar pines could grow in very dry soils and that most of the healthy sugar pines they found were growing in gently sloped areas with moderate amounts of sunlight.

Another group sought to answer the question of what the most common types of plants found near sugar pines were. White pine blister rust is unique in that it requires a secondary host species, in addition to sugar pines, to survive. The students hypothesized that they would find more gooseberry plants in close proximity to sugar pines because gooseberries are one of the more common secondary hosts used by the rust fungus. Although the group did find gooseberry plants, they discovered that several other plants, such as white thorn, squaw carpet, and manzanita, were more abundant near sugar pines.

After completing their experiments, students learned to graph their findings and create presentations highlighting their discoveries. At the end of this program, each group presented their projects to their peers gaining valuable public speaking experience.

Based on pre- and post-program assessments of students’ view of science, the number of individuals who reported feeling confident applying the scientific method increased by 24 percent.

This program and the impact it had was made possible in part by funds from the Rotary Club of Tahoe City.

Source: North Tahoe Middle School