Biomes: Global Patterns of Life

Outline Terrestrial Biomes Marine Ecosystems Open Ocean Shallow Coasts Freshwater Ecosystems Lakes Wetlands Human Disturbance

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

Deserts Characterized by low moisture levels and precipitation that is infrequent and unpredictable from year to year. Wide daily and seasonal temperature fluctuations. Soils are easily disturbed by human activities, and slow to recover. Plants exhibit water conservation characteristics.

Deserts

Grasslands Communities of grasses, seasonal herbaceous flowering plants, and open savannas. Few trees due to inadequate rainfall. Large daily and seasonal temperature fluctuations. Frequent grass fires. Historic grazing by roaming herds of large ungulates.

Grasslands

Tundra Treeless, temperatures are below freezing most of the year, only small hardy vegetation survives. Very short growing season, with cold harsh winters. Damage slow to heal. Arctic Tundra exhibits low productivity, diversity and resilience. Alpine Tundra receives intense solar radiation, hot daytime summer ground temperatures, and potential droughts.

Tundra

Conifer Forests Cone-Bearing Plants reduce water loss by evolving thin, needle-like evergreen leaves with thick waxy coating. Can survive harsh winters or extended droughts and accomplish photosynthesis even under poor conditions. Fire often plays role in maintenance.

Conifer Forests Boreal Forest - Northern Conifer Forest Broad band of mixed coniferous and deciduous trees between 45° and 60° N latitude. Moist and cool climate with abundant streams and wetlands. Taiga - Northernmost edge of boreal forest Species-poor. Harsh climate limits productivity and resilience. Produce large peat bogs.

Boreal Forest

Conifer Forests Temperate Rainforest Wettest portion of coniferous forests of Pacific Northwest. Mild temperatures, and very abundant precipitation. (>250 cm) Canopy condensation is major form of precipitation.

Broad-Leaved Deciduous Forest Temperate regions support lush summer plant growth when water is plentiful. Deciduous leaves an adaptation to freezing temperatures. 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 Deciduous Forests

Mediterranean Characterized by warm, dry summers and cool, moist winters. Fires are a major factor in plant succession. Referred to as chaparral in California. Biodiversity hotspot. Referred to as thorn scrub in Africa. Landscape dominated by acacias and other spiny plants.

Tropical Moist Forests Humid tropical regions support one of most complex and biologically rich biomes. Ample rainfall and uniform temperatures. Cloud Forests - High mountains where fog and mist keep vegetation continually wet.

Tropical Moist Forests Tropical Rainforests - More than 200 cm annual rainfall with warm-hot temperatures year-round. 90% nutrients tied up in living organisms. Rapid decomposition and nutrient cycling. Thin soil cannot support continued cropping, and cannot resist erosion.

Tropical Rainforests

Tropical Seasonal Forests Semi-evergreen and partly deciduous forests tending toward open woodlands and grassy savannas. Characterized by distinct wet and dry seasons with hot temperatures year-round

MARINE ECOSYSTEMS Saltwater ecosystems cover vastly more total area and contain much greater volume of water than all freshwater bodies combined. Oceans hold bulk of world’s water. Aquatic ecosystems are influenced by local characteristics of climate, soil, and resident communities, and also by adjacent terrestrial ecosystems.

Critical Characteristics Dissolved Substances Suspended Matter Depth Temperature Flow Rate Bottom Characteristics Internal Convective Currents Connectivity to Other Aquatic Ecosystems

Marine Ecosystems Vertical stratification is an important aspect of many aquatic ecosystems. Organisms tend to form distinctive vertical sub-communities. Benthic - Bottom sub-community. Low oxygen levels. Pelagic - Water column

Light Penetration

Shallow Coasts Coral Reefs - Accumulated calcareous skeletons of colonial organisms (coral). Depth limited by light penetration. Among most endangered communities. Mangrove trees grow in salt water. Occur along calm, shallow, tropical coastlines.

Tidal Environments Estuaries - Bays or semi-enclosed bodies of brackish water that form where rivers enter the ocean. Usually carry rich sediments. Fan-shaped sediment deposit (delta) formed on shallow continental shelves.

Barrier Islands Barrier Islands - Low, narrow, sandy islands that form offshore from a coastline. Protect inland shores from surf. Prized for human development. Loss of vegetation triggers erosion.

FRESHWATER ECOSYSTEMS Lakes Freshwater lakes have distinct vertical zones. Epilimnion Hypolimnion Benthos Thermocline - Distinctive temperature transition zone that separates warm upper layer and deeper cold layer.

Wetlands Land surface is saturated or covered with water at least part of the year. Swamps - Wetlands with trees. Marshes - Wetlands without trees. Bogs and Fens - Waterlogged soils that tend to accumulate peat. Water usually shallow enough to allow full sunlight penetration. Trap and filter water, and store runoff.

Wetlands

HUMAN DISTURBANCE By some estimates, humans preempt about 40% of net terrestrial primary productivity. Temperate broad-leaved deciduous forests are the most completely human-dominated biome. Tundra and Arctic Deserts are the least disturbed. About half of all original wetlands in the US have been degraded over the past 250 years.

Human Disturbance

Summary Terrestrial Biomes Marine Ecosystems Open Ocean Shallow Coasts Freshwater Ecosystems Lakes Wetlands Human Disturbance