Biomes and Soils

Grade Adjustments

• Final grades on Canvas may be adjusted upwards by 1-3% based on participation (e.g., attending work parties).
• The adjusted grade will be entered directly into the registrar system, and students will only see the final letter grade.
• Even small increases in the grade percentage gets bumped up.

Course Topics: Biomes and Soils

• Biomes and soils are applications of concepts already discussed in the course.
• The goal is to integrate prior knowledge to understand climate envelopes (biomes) and soil types.
• The course provides a foundation for upper-division environmental studies classes focused on soils and biogeography.

Understanding Biomes

• A biome is a climate envelope (temperature and precipitation patterns over 30-year periods) that supports specific vegetation communities.
• Knowledge of global winds, orographic lifting, and pressure systems helps explain the distribution of biomes.
• For the final exam, expect map-based questions identifying expected biomes or soil orders based on geographic location and climate factors.

Biomes and Climate

• Biomes are influenced by climate.
• Climate zones (Kerpin climate system) align with biome distribution.
• Temperature and precipitation patterns determine biome locations.

Definition of Biomes

• Biomes are large-scale ecosystems with uniform vegetation primarily driven by temperature and precipitation.
• Variations in temperature (cold to hot) and precipitation (dry to wet) result in major global biomes.
• Different classification systems exist, but the key biomes discussed in the course will be highlighted.
• Examples include tropical rainforests and others.

Biome Characteristics

• Each biome will be examined in terms of location and the processes that create it.
• Locations dominated by low pressure systems may experience a correlation to rainy conditions and potentially wet biomes.
• Latitude influences temperature and the presence of colder biomes.

Climographs

• Climographs show precipitation (bars) and temperature (line) for a biome.
• Temperature range indicates latitude, continentality, or marine effects.
• Timing of warmest/coldest months indicates northern/southern hemisphere location.
• Precipitation patterns reflect high/low pressure systems and global winds.

Tropical Rainforests

• Tropical rainforests are warm and wet biomes found near the Equator.
• Characterized by multi-story canopies, high species diversity, and productivity due to solar energy and rainfall.
• The climograph has warm temperatures year-round and abundant rainfall.
• Locations are equatorial or have wind patterns bringing warm, wet air onshore.

Tropical Seasonal Forests

• Tropical seasonal forests are warm biomes near the Equator but with seasonal precipitation.
• These biomes shows a seasonal surge in precipitation.
• The short rainfall creates different vegetation communities.
• Climograph: warm temperatures, a wet season, and a dry season.
• The wet season is due to the influence of the ITCZ.
• The dry season occurs as the ITCZ moves away from the location during the year.

Tropical Savannahs

• Tropical savannahs are warm biomes with arid conditions.
• Located where the ITCZ is less influential.
• Significant moisture deficit.
• Landscape: grasses rather than tall trees.
• Climograph: warm, with low rainfall especially in summer.
• Influenced by high pressure near the Tropic of Cancer and Capricorn.

Mediterranean Biomes

• Mediterranean biomes have moderate temperatures and dry conditions.
• Locations tend to be near the ocean.
• Temperature regimes are moderated due to proximity to the water.
• Southern California and the Mediterranean region are examples of this biome.

Deserts

• Deserts are the driest biomes, receiving less than 12 inches of precipitation annually.
• Large temperature ranges are expected due to dryness.
• Located near zones of high pressure (Tropic of Cancer and Capricorn) or in rain shadow areas.
• The Atacama Desert is next to the Pacific Ocean due to wind patterns, topography (Andes), and a cold ocean current.

Temperate Grasslands

• Temperate grasslands are heavily modified for agriculture due to fertile soils and favorable climate.
• Locations include the breadbaskets of the world.
• Continental, somewhat arid environments.
• Climograph: temperature range indicates a continental climate.

Temperate Rainforests

• Temperate rainforests are cool and wet biomes.
• Located in mid-latitudes, often near the zone of low pressure (55-60 degrees north and south), which is where Bellingham is located.
• West Coast orientation due to the westerly winds with rain.
• Locations have ample rainfall in winter due to the subpolar low.
• Summer conditions are drier due to high pressure moving north.
• Geographic setup: Mid-latitude location along the coast on the west coast of a continent.

Tundra

• Tundra is a cold, dry environment found at high latitudes or high elevations.
• Significant limiting factors: Temperatures below freezing for part of the year and general dryness restricts vegetation.
• Vegetation: sparsely vegetated landscape, small roots and shrubs close to the ground.
• Southern tip of South America has tundra due to high elevation and cold ocean water.

Soils

• Soils are the interface between bare bedrock and life.
• Natural bodies consisting of layers (horizons).
• Made up of mineral material and organic matter.
• Soils evolve over time. The starting condition is bedrock weathering and accumulating organic matter. Over time soils will form as they evolve, making them completely different than the starting material.

Soil Horizons

• Soils develop distinct layers or horizons.
• Soil horizons:
  • O horizon: Organic layer, composed of decomposed organic matter. It's deeply rich in organic matter and is dark brown.
  • A horizon: Topsoil, area of plant activity. It provides access to the most nutrients.
  • E horizon: Zone of eluviation.
  • B horizon: Subsoil, accumulation of materials from upper layers. Clay rich with not much organic matter.
  • C horizon: Parent material that is not chemically altered.
  • Regolith: Unweathered bedrock.
• Soil formation is influenced by organic inputs, climate, topography, etc.

Soil Orders

• There are 14 soil orders in the upper level of the soil calssification system.
• Seven soil orders are linked to biomes in this course.
• Soil orders are connected and related to vegetation and the climate envelope.

Andesoles

• Volcanic soils formed on volcanic ash or cinders.
• Less than 1% of global soils, but important along the Pacific Rim, including in the PNW.
• Important soil type for coffee production in South America.
• There is good presence of andesoles along the Pacific Crest because of all the volcanic activities.

Aridisols

• Arid=dry soils, where soil moisture is a significant limiting factor.
• Maps onto dry environments.

Molossols

• Mid-latitude grassland soils that are highly nutrient-rich and productive.
• Present in spades in the US around a quarter of all US soil.
• Willamette Valley and Palouse in Oregon and Washington.
• Molossols have deep o and a horizons.

Oxisols

• Tropical rain forest soils on old environments.
• Highly weathered and leached, fairly nutrient-poor.
• Vegetation drops organic matter which is quick to decompose.
• Nutrients are taken up by plant roots and do not accumulate in the soil.
• Fragile if disturbed; have a few years of productivity left in them after clearing forests.

Spodosols

• The temperate rainforest soil.
• Cool, wet and acidic climate along with acidic inputs.
• These are the PNW forest soils.
• Defining characteristic: E horizon is a characteristically modeled, white-looking horizon.

Entisols

• Young soils without distinct horizons.
• Found in areas with disturbance, like landslides or floodplains.
• Form slowly; USDA estimates an inch of soil takes 100-500 years to form.
• Also found in extreme environments which hinder soil development.
• Can also occur anywhere that's has super dry conditions.

Gelisols

• Soil of the tundra biome.
• Cold and dry environment; limiting horizonation due to cold temperatures.
• Alaska is underlain by these soils.
• One telltale sign of them is that cracked surface.