Soils and Waters Exam 3 Review

Spatial and Temporal Scales

Streams are not stationary as they move substrate everyday and change as they interact with the environment

• Stream segment: 50,000 years (1000 m)

• Segment system: 500 years (100 m)

• Reach system: 50 years (10 m)

• Pool/Riffle system: 5 years (1 m)

• Microhabitat system: 0.5 year (0.1 m)

Stream Components

Run: Strong velocity with no turbulence, straight area

Riffle: Turbulent flow (surface water has rapids), formed by heavy substrate

Pool: Deep water with low velocity, formed by substrate erosion around bends

Forces that drive stream migration

• Erosion

  • Hydraulic action: Sediment loosened by flowing water

  • Solution: Geologic material dissolved gradually

  • Abrasion: Bedrock weather by force of sediment load

• Velocity

  • Slower water can settle sediment faster while fast water erodes in the other direction

Sediment Load

Any substance moved by a stream.

• Total Dissolved Solids (TDS): Ions, salts (do not directly impact stream morphology)

• Total Suspended Solids (TSS): Silts, clay (build meandering and deep channels)

• Bedload: Gravel and sand is pushed at the bottom of a stream (can form riffles and shape the channel bed)

  • Occurs when flow is at/near bankful

Floodplain functions

Responsible for flood mitigation, storage, sediment deposition, nutrient removal, and habitat

Bankfull functions

Responsible for channel reshaping (occurs ever 1.5 years)

Stream functions

Purify water, flood mitigation, breeding habitat, water supply, power production, groundwater regeration

Human impact on stream functions

Trapping natural sediment from being transported with dams and reservoirs, discharge overloading streams with nutrients, decreasing groundwater recharge with urbanization, stream destabilization and further erosion with agriculture and deforestation

River Continuum Concept

Demonstrates the progression of orders in a stream and the different organisms in these orders as well as food, organic matter, and light penetration

Lake Types

Glacial lake, kettle lake, volcanic lake, rift lake, oxbow lake, and impoundments

Glacial Lake

Depressions filled by meltwater

• Great lakes contain 20% of glacial freshwater

Kettle Lakes

Ice buried in the glacial outwash melt from receding and filling the depression

Volcanic Lakes

Rimmed basins formed by subsidence after eruptions

• Filled by rain

Rift Lakes

Tectonic activity produces fissures/crevasses that fill with water

• Deep, low surface area

• Lake Baikal

Oxbow Lakes

Formed by river migration

Impoundment Lakes

Lakes formed by dams (reservoirs)

Lake Hydrology

Drainage Lake: Surface inflow / outflow

Seepage Lake: Fed by groundwater / precipitation

Lake Trophic Status

Oligotrophic: Low nutrients + primary production = high clarity

Mesotrophic: Moderate nutrients + primary production = clarity

Eutrophic: High nutrients + primary production = low clarity

Lake Zones

Euophotic: Depth to which light penetrates

Littoral: Near shore, sunlight reaches sediments

Limnetic: Deep, open water away from shore

Benthic: Bottom sediments

Lake Layers

Epilimnion: Shallow, low density, goof light penetration (warmer water)

Metalimnion: Rapidly changing temp. that has a variation with depth (thermocline)

Hypolimnion: Deep, high density, little or no light penetration (colder)

Thermocline

Prevents mixing between Epilimnion and Hypolimnion

Stratification

Temperature in deep lakes are dimictic, meaning they have two turnover events per year in the spring and fall which replenishes the water column with O2 which can further impact trophic levels

• Oligotrophic: DO remains near saturation

• Eutrophic: DO depleted in hypolimnion because of decomposition

• Summer: High DO on the surface, lower DO in the deeper waters due to temperature and density

• In the fall and spring, DO levels are even (isothermal)

Wetlands

Transitional land between terrestrial and aquatic ecosystems that maintains saturation over 2 consecutive weeks in the last 5 / 9 years

• Found in every climate / continent besides Antarctica

  • Makes up 30% of NA boreal forests

  • 6% of surface area in US

Wetland Properties

• Hydric Soils: Formed in low oxygen conditions by repeated wetting

• Hydrophytic Vegetation: Water-tolerant plants adapted to growing in low oxygen conditions

• Water-Carbon Storage: Slower water movements, groundwater recharge, reduced erosion, and prevention of decomposition

• Nutrient removal: Sediment settlement removes P, denitrification removes N (wetland plants can remove both through uptake)

Wetland indicators

Hydrology

• Standing water, sediment deposits, saturation, water marks, tree buttresses (expanding trunk)

Hydric Soils

• Color < 2, reduced iron (gray), organic matter, hydrogen surface (rotten egg smell), redoximorphic features (changes in aerobic and and anaerobic condition inidcator)

Wetland functions

Wetlands provide biological habitat, structure for breeding nesting, and foraging, nutrients for fish and feeding areas, create plant diversity, safe zones for amphibians

Wetland management in the US

Wetlands have been historically seen as a nuisance and many have been drained

• 58,500 acres of wetlands lost per year through 1986-1997

• Bolstered by urban development, agriculture, silviculture, and rural development

Soil importance

Soil is important because it is a foundation for all life on earth in the way it supports plant growth, soil organisms (habitat), engineering, recycles nutrients, and creates a water supply

• Without soil we would not have food, shelter, clothing, water, or medicine

Soil composition

50% solid (45% mineral and 5% organic)

50% pore space

Why is soil organic matter important?

It plays a crucial role in physical, chemical, biological functions

• Can automatically improve plant performance and function

• Carbon in soil supports plants + atmosphere

• Amount of SOM can impact pH, binding, structural stability (roots), water retention, and temperature

Soil texture

Relative particle sizes in mineral fraction expressed as a soil texture

• Impacts hydraulic properties and further impacts organism abundance + activity

• Sand: 0.02 - 2.0mm

• Silt: 0.002 - 0.2 mm

• Clay: < 0.002 mm

Soil profile

Layers formed due to the interactions between the soil forming factors

• Surface soil differs from parent material because of weathering + organisms

Bedrock: Unweathered parent material

Regolith: Soil profile, everything about bedrock

Solum: Active layers of soil (A, B, E horizons)

Soil horizons

D: Organic matter - cannot develop without it

A (topsoil): Minerals mixed with organic matter (dark brown)

E: Weathered and leached layer (eluvation) (grey-muted/dull)

• Dependent on precipitation

B (subsoil): Minimal organic matter, weather minerals + clay + iron (illuviation) (bright colors because of accumulation)

• Dependent on leaching from upper horizons

C: partially weather parent material

Soil horizon development

Movement of materials through illuviation and eluviation or plant uptake and erosion, materials (leaves and dead plants) adding to the soil surface, and material weathering