Download Ecology Lecture 2: Life on Land - Soil and Terrestrial Biomes - Prof. Brent Blair and more Study notes Ecology and Environment in PDF only on Docsity!
Today’s Outline Ecology (BIOL 250) Lecture 2: Life on Land Announcements The light resource The soil Resource Soil horizons Soil profile Importance of light and soil Terrestrial Biomes
Light Availability
Light Availability Soil : Foundation of Terrestrial
Biomes
Soil is a complex mixture of living and non- living material. Classification based on vertical layering (soil horizons), texture and chemical properties. Profile provides a snapshot of soil structure in a constant state of flux.
Soil Horizons
O horizon: Organic Layer freshly fallen organic material - most superficial layer. A horizon: Mixture of minerals, clay, silt and sand. B horizon: Clay, humus, and other materials leached from A horizon - often contains plant roots. C horizon: Weathered parent material. Soil Profile vs Soil Horizons
Soil Texture
Soil Texture: The proportion of different sized soil particles. Gravel: Particles greater than 2.0 mm. Sand: Particles between .05 - 2.0 mm Silt: Particles between .002 - .05 mm Clay: Particles less than .002mm
But why are soil types, light,
(& rainfall) important?
Predicts what the land may be used for (i.e., human uses the land may have) Influences what type of vegetation will be present Influences the quantity and diversity of vegetation
TERRESTRIAL BIOMES
Biomes - Areas sharing similar climate, topographic and soil conditions, and roughly comparable communities. Temperature and precipitation are among the most important determinants in biome distribution. Most terrestrial biomes are identified by the dominant plants of their communities.
Biomes
Climate Diagrams Tropical Rainforests
Location within 10o^ latitude of equator Little temperature variation between months. Annual rainfall of 2,000 - 4,000 mm relatively evenly distributed. Harbor staple foods and medicines for world’s human populations - increasingly exploited.
Temperate Forest
Majority lie between 40o^ and 50o^ latitude Rainfall averages 650 - 3,000 mm. Fertile soils Long growing seasons dominated by deciduous plants. Short growing seasons dominated by conifers. Biomass production can be very high. Eastern half of US was covered with broad leaf deciduous forest when European settlers arrived. Much of that was harvested a century ago for timber. Now large areas have re-grown and are again approaching old-growth status.
Temperate Forest
Temperate Grassland
widespread distribution Annual rainfall 300 - 1,000 mm. Experience periodic droughts. Soils tend extremely nutrient rich and deep. Thoroughly dominated by herbaceous vegetation. Large roaming ungulates. Bison vs. cattle
Tundra
Covers most of lands north of Arctic Circle Very short growing season, with cold harsh winters. 200 - 600 mm precipitation. Low decomposition rates. Supports substantial numbers of native mammals. Human intrusion historically low, but increasing as resources become scarce. Typically frozen! But…
Dispersers of Guanacaste Seeds
Janzen studied natural history of tropical dry forests in Costa Rica to aid restoration efforts. Guanacaste tree ( E. cyclocarpum ) has no current dependable dispersers Last native dispersers went extinct 10,000 years ago.
- Cattle and horses (exotics) now act as dispersers.
