The Natural Environment - Chapter 20

Biogeographic Realms

geographic region where a group of plant and animal species evolved and traditionally has been used as a basis for establishing terrestrial ecoregions.

Biogeography

study of distribution b/w organisms and their environment and among the various ecosystems in biosphere

Ecotone

•A boundary transition zone between adjoining ecosystems

Terrestrial Ecosystems

•A terrestrial ecosystem is an association of plants and animals, and their abiotic environment. •A biome is a large terrestrial ecosystem, characterized by specific plants and animals. •Each biome is named for its dominant vegetation. •We can generalize into six broad biomes: forest, savanna, grassland, shrubland, desert, and tundra.

Earth's Physical Systems Impact on Vegetation:

•Energy patterns •Atmospheric composition •Temperature and winds •Precipitation quantity, quality, and seasonal timing •Soils and nutrients •Chemical pathways •Geomorphic processes •Disturbances

6 Major Groups of Terrestrial Vegetation

•Forest, Savanna, Grassland, Shrubland, Desert, Tundra

Midlatitude Grasslands

•Midlatitude grasslands (tall grass and short grass) are the most modified by human activity. •These "breadbaskets" regions produce grain, soybeans, and livestock. •mollisols*** •temp- temperate continental regimes •water- soil moisture use/recharge is balanced; irrigation, dry farming sometimes used

Temperate Rain Forest

•The lush forests in wet, humid regions •broadleaf and needle leaf trees, epiphytes, huge ferns, and thick undergrowth •occurring along middle to high-latitude west coasts •water: large surplus and runoff •mild summer and winter (for latitude)

Earth's Major Terrestrial Biomes

•Tropical Rain Forest •Tropical Seasonal Forest and Scrub •Tropical Savanna •Midlatitude Broadleaf and Mixed Forest •Boreal and Montane Forest •Temperate Rain Forest •Mediterranean Shrubland •Midlatitude Grassland •Warm Desert & Semidesert •Cold Desert & Semidesert •Arctic and Alpine Tundra •Polar Deserts

Tropical Savanna

•Tropical savanna is large expanse of grassland interrupted by trees and shrubs. •It is a transitional biome between the tropical forests and desert. •Tropical savannas receive precipitation when the ITCZ is overhead, and rest of the year are under dry condition due to subtropical high pressure cells. •Fires occur annually through the biome.

Warm Desert & Semidesert

•basic ground w succulents, cacti, dry shrubs •arid •highest temps on earth •water: chronic deficits; irregular precipitation

Tropical Rain Forest

•covers earth's equatorial region •always warm •evergreen broadleaf trees; canopies thick and rich w life •surplus water all year •infertile soils

Biome

•large, stable, terrestrial or aquatic ecosystem classified according to the predominant vegetation type and the adaptations of particular organisms to that environment •carry the name of the dominant vegetation because it is the most easily identified feature.

Midlatitude Broadleaf & Mixed Forest

•mixed/deciduous broadleaf, needleleaf; lose leaves in winter •temperate with cold season •water: seasonal pattern w summer max precit/potet

Polar Desert

•mosses, lichens •permafrost •cold, dry •water- n/a

Boreal forest/northern needle leaf forest/Montane Forest

•needle leaf conifers •montane- high altitude •short summer, cold winter •moist soil

Mediterranean Shrubland

•occupies temperate regions that have dry summers •The dominant shrubs are low-growing and able to withstand hot-summer drought and recover after fires. •Most shrubs average a meter or two in height •hot dry summer, cool winter •water: summer deficit, winter surplus

Cold Desert & Semidesert

•short grass, dry shrubs •semiarid steppe •precip less than 1/2 potential

Tropical Seasonal Forest & Scrub

•transition b/w rain forest and grassland •dense undergrowth •temp: variable, always warm •water: seasonal surpluses and deficits

Arctic & Alpine Tundra

•treeless, alpine grass meadows, shrubs; slow growing, easily disturbed •only 2-3 months above freezing •The arctic tundra biome is located in the extreme northern area of North America and Russia, bordering the Arctic Ocean and generally north of the 10°C isotherm for the warmest month. •Alpine in lower latitudes; above treelike •water- n/a most of year, poor drainage