题目 1 · Design an Investigation
10 分Researchers studied the effectiveness of different riparian buffer zone restoration methods along a river bordering agricultural fields in the Midwestern United States. Three distinct 100-meter riparian zones were established and monitored over a 15-year period:
- Zone 1 (Natural Regeneration): The streamside bank was left unmanaged, allowing native and non-native pioneer plants to colonize naturally without intervention.
- Zone 2 (Engineered Agroforestry): The streamside bank was graded, amended with compost, and actively planted with a multi-layered strip of deep-rooted native hardwood trees, shrubs, and perennial prairie grasses.
- Zone 3 (Control / No Buffer): Traditional agricultural farming was maintained with row crops planted directly up to the stream edge.
Researchers recorded the mean nitrate (\(\text{NO}_3^-\)) concentration in shallow groundwater entering the stream from each zone over time. The results are shown in the table below.
### Mean Nitrate Concentration in Shallow Groundwater (mg/L)
| Years After Establishment | Zone 1: Natural Regeneration (mg/L) | Zone 2: Engineered Agroforestry (mg/L) | Zone 3: No Buffer / Control (mg/L) |
| :--- | :--- | :--- | :--- |
| Year 1 | 28.5 | 27.8 | 29.1 |
| Year 5 | 21.0 | 12.4 | 28.9 |
| Year 10 | 14.2 | 6.1 | 29.5 |
| Year 15 | 8.5 | 3.2 | 30.0 |
(a) Based on the data in the table, identify the mean nitrate concentration in groundwater entering the stream in Zone 2 ten years after establishment.
(b) Based on the data in the table, describe the relationship between the age of the buffer zone and the mean nitrate concentration in groundwater for Zone 1.
(c) Researchers hypothesized that active planting of mixed woody and perennial vegetation (engineered agroforestry) reduces nitrate concentrations entering waterways more rapidly than passive natural regeneration. Using the data in the table, make a claim that supports or refutes this hypothesis.
(d) Describe one ecosystem service, other than water filtration/nutrient uptake, provided by riparian buffer zones.
(e) Explain how the rate of nitrate removal by plant uptake in the riparian buffers would be altered during winter in a temperate deciduous forest biome compared to the summer months.
---
To evaluate how soil compaction from farm equipment influences surface runoff and soil erosion, students set up a field simulation. They marked three identical \(2\text{ m} \times 2\text{ m}\) plots on a uniform 5% slope with the same loam soil type:
- Plot A (High Compaction): Driven over repeatedly with heavy tractor tires.
- Plot B (Moderate Compaction): Compacted only by human foot traffic.
- Plot C (Uncompacted): Tilled and loosened, with no machinery or foot traffic.
Each plot received 60 liters of water evenly sprinkled over a 30-minute period. Runoff water from the downslope edge of each plot was captured in collection buckets, and the total volume of runoff and total suspended solids (TSS) were measured.
(f) Identify the scientific question for the students' investigation.
(g) Identify the independent variable in the experiment.
(h) Explain how the results of the experiment would likely be altered if all three plots were planted with a dense cover crop of clover prior to testing.
---
Runoff from agricultural lands can severely impact nearby aquatic ecosystems.
(i) Describe one ecological impact on aquatic organisms that can result from increased turbidity caused by agricultural soil erosion.
(j) Describe one agricultural management practice, other than establishing riparian buffers, that farmers can use to reduce soil erosion and nutrient runoff into nearby waterways.
- Zone 1 (Natural Regeneration): The streamside bank was left unmanaged, allowing native and non-native pioneer plants to colonize naturally without intervention.
- Zone 2 (Engineered Agroforestry): The streamside bank was graded, amended with compost, and actively planted with a multi-layered strip of deep-rooted native hardwood trees, shrubs, and perennial prairie grasses.
- Zone 3 (Control / No Buffer): Traditional agricultural farming was maintained with row crops planted directly up to the stream edge.
Researchers recorded the mean nitrate (\(\text{NO}_3^-\)) concentration in shallow groundwater entering the stream from each zone over time. The results are shown in the table below.
### Mean Nitrate Concentration in Shallow Groundwater (mg/L)
| Years After Establishment | Zone 1: Natural Regeneration (mg/L) | Zone 2: Engineered Agroforestry (mg/L) | Zone 3: No Buffer / Control (mg/L) |
| :--- | :--- | :--- | :--- |
| Year 1 | 28.5 | 27.8 | 29.1 |
| Year 5 | 21.0 | 12.4 | 28.9 |
| Year 10 | 14.2 | 6.1 | 29.5 |
| Year 15 | 8.5 | 3.2 | 30.0 |
(a) Based on the data in the table, identify the mean nitrate concentration in groundwater entering the stream in Zone 2 ten years after establishment.
(b) Based on the data in the table, describe the relationship between the age of the buffer zone and the mean nitrate concentration in groundwater for Zone 1.
(c) Researchers hypothesized that active planting of mixed woody and perennial vegetation (engineered agroforestry) reduces nitrate concentrations entering waterways more rapidly than passive natural regeneration. Using the data in the table, make a claim that supports or refutes this hypothesis.
(d) Describe one ecosystem service, other than water filtration/nutrient uptake, provided by riparian buffer zones.
(e) Explain how the rate of nitrate removal by plant uptake in the riparian buffers would be altered during winter in a temperate deciduous forest biome compared to the summer months.
---
To evaluate how soil compaction from farm equipment influences surface runoff and soil erosion, students set up a field simulation. They marked three identical \(2\text{ m} \times 2\text{ m}\) plots on a uniform 5% slope with the same loam soil type:
- Plot A (High Compaction): Driven over repeatedly with heavy tractor tires.
- Plot B (Moderate Compaction): Compacted only by human foot traffic.
- Plot C (Uncompacted): Tilled and loosened, with no machinery or foot traffic.
Each plot received 60 liters of water evenly sprinkled over a 30-minute period. Runoff water from the downslope edge of each plot was captured in collection buckets, and the total volume of runoff and total suspended solids (TSS) were measured.
(f) Identify the scientific question for the students' investigation.
(g) Identify the independent variable in the experiment.
(h) Explain how the results of the experiment would likely be altered if all three plots were planted with a dense cover crop of clover prior to testing.
---
Runoff from agricultural lands can severely impact nearby aquatic ecosystems.
(i) Describe one ecological impact on aquatic organisms that can result from increased turbidity caused by agricultural soil erosion.
(j) Describe one agricultural management practice, other than establishing riparian buffers, that farmers can use to reduce soil erosion and nutrient runoff into nearby waterways.
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解题
Part (a)
From the table, at Year 10, Zone 2 (Engineered Agroforestry) has a mean nitrate concentration of \(6.1\text{ mg/L}\).
Part (b)
There is an inverse (negative) relationship between the age of the natural regeneration buffer zone and nitrate concentration: as time progresses from Year 1 to Year 15, the nitrate concentration steadily declines from \(28.5\text{ mg/L}\) down to \(8.5\text{ mg/L}\).
Part (c)
The claim supports the hypothesis. By Year 5, Zone 2 lowered nitrate levels to \(12.4\text{ mg/L}\) compared to \(21.0\text{ mg/L}\) in Zone 1. By Year 15, Zone 2 achieved a level of \(3.2\text{ mg/L}\), which is less than half of Zone 1's \(8.5\text{ mg/L}\), showing that active engineered agroforestry accelerates nutrient reduction compared to natural succession alone.
Part (d)
Riparian buffer zones provide numerous ecosystem services beyond water filtration:
- Supporting/Habitat: Provide wildlife habitat, nesting sites, and migratory corridors.
- Regulating: Tree roots stabilize stream banks, reducing channel erosion; canopy shade lowers water temperatures, maintaining higher dissolved oxygen levels.
- Cultural: Aesthetic value and recreational fishing/birdwatching.
Part (e)
In a temperate deciduous forest biome, deciduous plants shed their leaves and enter a state of dormancy during winter. In this dormant state, transpiration and active nutrient uptake by root systems cease or drop significantly compared to peak growing conditions in summer, thereby reducing the rate of nitrate removal from groundwater.
Part (f)
A correctly phrased scientific question relates the independent variable (degree of soil compaction) to the dependent variable (runoff volume or sediment/TSS collected). For example: "How does the level of soil compaction affect the amount of surface runoff produced during precipitation?"
Part (g)
The independent variable is the level of soil compaction (or the treatment method applied to the soil plots: high, moderate, or uncompacted).
Part (h)
Growing a dense cover crop would reduce both the total volume of runoff and the amount of suspended sediment (TSS) collected. Plant foliage intercepts falling raindrops to minimize soil detachment, and extensive root networks improve soil structure and macroporosity, facilitating greater infiltration of water into the soil column.
Part (i)
Elevated turbidity reduces sunlight penetration through the water column, which decreases photosynthetic rates of submerged aquatic plants and phytoplankton. Additionally, suspended sediment particles can clog the gills of fish and aquatic invertebrates, reducing respiration efficiency, or settle out and smother benthic fish spawning beds/gravel habitats.
Part (j)
Practices include:
- No-till or conservation tillage: Leaves crop residue on soil surface, protecting against wind/water erosion and preserving root channels for infiltration.
- Contour plowing: Plowing perpendicular to the slope to create ridges that slow runoff water and prevent channel formation.
- Terracing: Creating stepped flat platforms on steep slopes to reduce runoff velocity.
- Cover cropping: Planting crops like rye or clover during fallow periods to maintain soil cover and bind soil particles.
From the table, at Year 10, Zone 2 (Engineered Agroforestry) has a mean nitrate concentration of \(6.1\text{ mg/L}\).
Part (b)
There is an inverse (negative) relationship between the age of the natural regeneration buffer zone and nitrate concentration: as time progresses from Year 1 to Year 15, the nitrate concentration steadily declines from \(28.5\text{ mg/L}\) down to \(8.5\text{ mg/L}\).
Part (c)
The claim supports the hypothesis. By Year 5, Zone 2 lowered nitrate levels to \(12.4\text{ mg/L}\) compared to \(21.0\text{ mg/L}\) in Zone 1. By Year 15, Zone 2 achieved a level of \(3.2\text{ mg/L}\), which is less than half of Zone 1's \(8.5\text{ mg/L}\), showing that active engineered agroforestry accelerates nutrient reduction compared to natural succession alone.
Part (d)
Riparian buffer zones provide numerous ecosystem services beyond water filtration:
- Supporting/Habitat: Provide wildlife habitat, nesting sites, and migratory corridors.
- Regulating: Tree roots stabilize stream banks, reducing channel erosion; canopy shade lowers water temperatures, maintaining higher dissolved oxygen levels.
- Cultural: Aesthetic value and recreational fishing/birdwatching.
Part (e)
In a temperate deciduous forest biome, deciduous plants shed their leaves and enter a state of dormancy during winter. In this dormant state, transpiration and active nutrient uptake by root systems cease or drop significantly compared to peak growing conditions in summer, thereby reducing the rate of nitrate removal from groundwater.
Part (f)
A correctly phrased scientific question relates the independent variable (degree of soil compaction) to the dependent variable (runoff volume or sediment/TSS collected). For example: "How does the level of soil compaction affect the amount of surface runoff produced during precipitation?"
Part (g)
The independent variable is the level of soil compaction (or the treatment method applied to the soil plots: high, moderate, or uncompacted).
Part (h)
Growing a dense cover crop would reduce both the total volume of runoff and the amount of suspended sediment (TSS) collected. Plant foliage intercepts falling raindrops to minimize soil detachment, and extensive root networks improve soil structure and macroporosity, facilitating greater infiltration of water into the soil column.
Part (i)
Elevated turbidity reduces sunlight penetration through the water column, which decreases photosynthetic rates of submerged aquatic plants and phytoplankton. Additionally, suspended sediment particles can clog the gills of fish and aquatic invertebrates, reducing respiration efficiency, or settle out and smother benthic fish spawning beds/gravel habitats.
Part (j)
Practices include:
- No-till or conservation tillage: Leaves crop residue on soil surface, protecting against wind/water erosion and preserving root channels for infiltration.
- Contour plowing: Plowing perpendicular to the slope to create ridges that slow runoff water and prevent channel formation.
- Terracing: Creating stepped flat platforms on steep slopes to reduce runoff velocity.
- Cover cropping: Planting crops like rye or clover during fallow periods to maintain soil cover and bind soil particles.
评分标准
Question 1: Design an Investigation (10 points total)
(a) 1 point
- Accept \(6.1\text{ mg/L}\) (or \(6.1\)).
(b) 1 point
Accept one of the following:
- As the age of the buffer increases, the mean nitrate concentration decreases.
- There is an inverse/negative relationship between buffer age and nitrate concentration.
(c) 1 point
- State that the hypothesis is supported AND cite relevant data comparing Zone 2 to Zone 1 over time (e.g., Zone 2 reached \(12.4\text{ mg/L}\) at Year 5 vs. \(21.0\text{ mg/L}\) in Zone 1 / Zone 2 reached \(3.2\text{ mg/L}\) at Year 15 compared to \(8.5\text{ mg/L}\) in Zone 1).
(d) 1 point
Accept one of the following:
- Provides wildlife habitat / nesting sites / migratory corridors.
- Stabilizes river banks / prevents bank erosion with root systems.
- Shading from tree canopy cools stream temperatures / increases dissolved oxygen capacity.
- Flood control / attenuates floodwaters.
- Recreational / aesthetic opportunities.
(e) 1 point
Accept one of the following:
- Nitrate uptake would decrease/be slower in winter because deciduous plants drop their leaves/enter dormancy, resulting in reduced metabolic activity/transpiration/nutrient absorption compared to summer.
- Nitrate uptake is lower in winter because freezing/colder temperatures slow down microbial denitrification and root metabolic rates.
(f) 1 point
Accept a testable scientific question connecting compaction to runoff/erosion, such as:
- Does soil compaction affect the volume/amount of surface runoff?
- How does the level of soil compaction affect sediment erosion/total suspended solids in runoff?
(g) 1 point
Accept one of the following:
- The level/degree of soil compaction.
- Plot treatment type (high compaction vs. moderate vs. uncompacted).
(h) 1 point
Accept an explanation connecting cover crops to reduced runoff/increased infiltration:
- Runoff volume (and/or sediment) would decrease because plant roots loosen soil/create channels that increase water infiltration.
- Plant roots hold soil in place and foliage slows runoff water, reducing erosion and runoff volume.
(i) 1 point
Accept one of the following:
- Reduces sunlight penetration, decreasing photosynthesis in submerged aquatic vegetation/algae.
- Suspended sediment clogs fish/invertebrate gills, impairing respiration.
- Settling sediment smothers fish eggs/benthic macroinvertebrate spawning habitats.
- Increases water temperature (darker particles absorb heat), decreasing dissolved oxygen.
(j) 1 point
Accept one of the following:
- No-till agriculture / conservation tillage.
- Contour plowing / planting along topographic contours.
- Terracing on slopes.
- Planting cover crops during the off-season.
- Crop rotation / strip cropping / intercropping.
- Precision fertilizer application / split fertilizer application.
(a) 1 point
- Accept \(6.1\text{ mg/L}\) (or \(6.1\)).
(b) 1 point
Accept one of the following:
- As the age of the buffer increases, the mean nitrate concentration decreases.
- There is an inverse/negative relationship between buffer age and nitrate concentration.
(c) 1 point
- State that the hypothesis is supported AND cite relevant data comparing Zone 2 to Zone 1 over time (e.g., Zone 2 reached \(12.4\text{ mg/L}\) at Year 5 vs. \(21.0\text{ mg/L}\) in Zone 1 / Zone 2 reached \(3.2\text{ mg/L}\) at Year 15 compared to \(8.5\text{ mg/L}\) in Zone 1).
(d) 1 point
Accept one of the following:
- Provides wildlife habitat / nesting sites / migratory corridors.
- Stabilizes river banks / prevents bank erosion with root systems.
- Shading from tree canopy cools stream temperatures / increases dissolved oxygen capacity.
- Flood control / attenuates floodwaters.
- Recreational / aesthetic opportunities.
(e) 1 point
Accept one of the following:
- Nitrate uptake would decrease/be slower in winter because deciduous plants drop their leaves/enter dormancy, resulting in reduced metabolic activity/transpiration/nutrient absorption compared to summer.
- Nitrate uptake is lower in winter because freezing/colder temperatures slow down microbial denitrification and root metabolic rates.
(f) 1 point
Accept a testable scientific question connecting compaction to runoff/erosion, such as:
- Does soil compaction affect the volume/amount of surface runoff?
- How does the level of soil compaction affect sediment erosion/total suspended solids in runoff?
(g) 1 point
Accept one of the following:
- The level/degree of soil compaction.
- Plot treatment type (high compaction vs. moderate vs. uncompacted).
(h) 1 point
Accept an explanation connecting cover crops to reduced runoff/increased infiltration:
- Runoff volume (and/or sediment) would decrease because plant roots loosen soil/create channels that increase water infiltration.
- Plant roots hold soil in place and foliage slows runoff water, reducing erosion and runoff volume.
(i) 1 point
Accept one of the following:
- Reduces sunlight penetration, decreasing photosynthesis in submerged aquatic vegetation/algae.
- Suspended sediment clogs fish/invertebrate gills, impairing respiration.
- Settling sediment smothers fish eggs/benthic macroinvertebrate spawning habitats.
- Increases water temperature (darker particles absorb heat), decreasing dissolved oxygen.
(j) 1 point
Accept one of the following:
- No-till agriculture / conservation tillage.
- Contour plowing / planting along topographic contours.
- Terracing on slopes.
- Planting cover crops during the off-season.
- Crop rotation / strip cropping / intercropping.
- Precision fertilizer application / split fertilizer application.