♻️AP Environmental Science
1. Temperate deciduous forests are characterized by trees that lose their leaves seasonally, creating a layer of leaf litter on the forest floor. Decomposers such as bacteria, fungi, and detritivores break down this organic matter, releasing nutrients back into the soil. The rate of decomposition affects nutrient availability for primary producers.
Describe one characteristic of temperate deciduous forest biomes related to seasonal temperature variation.
Based on the information provided, explain how decomposers contribute to nutrient cycling in the forest ecosystem.
Figure 1. Percent of Original Leaf Litter Mass Remaining Over Time at Three Temperatures (10°C, 20°C, 30°C)
Based on the data in Figure 1, identify the percent of original leaf litter mass remaining after 6 months at 20°C.
Based on the data in Figure 1, describe the relationship between temperature and the rate of leaf litter decomposition.
Figure 2. Soil Nitrogen Concentration (mg/kg) at Increasing Distances from a Stream
Scientists hypothesized that soil nitrogen concentration would be highest near the stream because water transports nitrogen from upland areas. Describe one way that the data in Figure 2 support this hypothesis.
Detritivore biodiversity is important for efficient decomposition. A group of students investigated factors affecting invertebrate diversity in leaf litter. They selected two study sites in a local forest: a mature forest section and a recently logged area. The students collected leaf litter samples by placing 10 randomly located sampling frames (0.25 m² each) at each site. They carefully sorted through the leaf litter and identified all invertebrate species present to determine species richness.
Identify a likely scientific question for the students' investigation of invertebrate diversity.
Identify the independent variable in the students' investigation.
Site | Millipedes | Earthworms | Beetles | Springtails | Mites | Centipedes |
|---|---|---|---|---|---|---|
Mature forest | X | X | X | X | X | X |
Recently logged area | X | X |
The data from the student investigation of invertebrate diversity are shown in the following table. An 'X' in the table indicates that the species was present at that site.
Explain why the invertebrate community in the mature forest would be more resilient to environmental stress, such as drought, than the invertebrate community in the recently logged area.
Explain how decomposition rates in the recently logged area might differ from those in the mature forest based on the invertebrate diversity data.
Describe one reason why energy transfer between trophic levels is inefficient. In terrestrial ecosystems, energy flows from primary producers through multiple trophic levels. Only approximately 10% of energy is transferred from one trophic level to the next.
