♻️AP Environmental Science
1. A temperate deciduous forest ecosystem in Pennsylvania contains multiple trophic levels. Oak trees are the dominant producers, converting solar energy through photosynthesis. Primary consumers include herbivorous insects such as caterpillars, which are consumed by insectivorous birds (secondary consumers). Hawks and owls serve as tertiary consumers by preying on smaller birds and mammals.
Energy Available at Each Trophic Level in Forest Ecosystem
Trophic Level | Energy Available (kcal/m²/year) |
|---|---|
Producers (plants) | 20,000 |
Primary consumers (herbivorous insects) | 2,000 |
Secondary consumers (insectivorous birds) | 200 |
Tertiary consumers (hawks and owls) | 20 |
Describe one way that producers in this forest ecosystem acquire and convert solar energy.
Based on the information in the data table, explain why there is less energy available at higher trophic levels in this forest ecosystem.
Based on the data in the table, identify the amount of energy available to secondary consumers.
Figure 2. Monthly Carbon Dioxide Uptake Rate by Forest Canopy (positive values indicate net uptake; negative values indicate net release).
Based on the data in Figure 2, describe the trend in carbon dioxide uptake by the forest canopy from April through October.
Scientists hypothesized that the forest acts as a carbon sink during the growing season. Describe one way the data in Figure 2 support this hypothesis.
Figure 1. Leaf Litter Mass and Soil Nitrogen Concentration at Different Distances from Stream (dual y-axes).
Decomposition Rates of Leaf Litter in Two Forest Sites
Site | Initial Mass (g) | Final Mass After 6 Months (g) | Percent Mass Remaining |
|---|---|---|---|
Site 1 (near stream) | 100 | 35 | 35% |
Site 2 (away from stream) | 100 | 58 | 58% |
Decomposition is a critical process in nutrient cycling. A group of students wanted to investigate factors that affect the rate of leaf litter decomposition in the forest. They selected two sites: Site 1 near the stream and Site 2 located 80 meters away from the stream. At each site, students placed 100 grams of freshly fallen oak leaves in mesh bags that allowed decomposers to access the leaves. After 6 months, they collected the bags, dried the remaining leaf material, and measured the final mass.
Identify the independent variable in the students' investigation.
Using Figure 1, identify one environmental factor that the students should have kept constant between the two sites to ensure a valid comparison.
The data from the student investigation on decomposition rates are shown in the table above.
Explain why the decomposition rate was faster at Site 1 (near the stream) compared to Site 2 (away from the stream).
Explain how the faster decomposition rate near the stream affects the nitrogen cycle in that area of the forest.
Describe one effect that prolonged drought conditions could have on the rate of decomposition in this forest ecosystem. Climate change is causing shifts in precipitation patterns in temperate forests.
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