EVPP 110 Lecture
Instructor: Dr. Largen Fall 2003

Climate and Biomes

• Ecosystem
• concept
• physical and biological components of environment are considered as single, interactive system
• defined as
• group of interacting species along with their physical environment
• similar physical environments lead to
• evolution of organisms similar in form and function
• similar ecosystems
• known as "rule of climatic similarity"
• basis of concept of biome
• type of ecosystem
• plant and animal community that covers large geographic areas

• Biomes
• major communities of organisms that
• have characteristic appearance
• distributed over wide geographic area
• defined largely by regional variations in climate
• strong relationship between climate and life suggests that
• if we know climate of an area
• we can predict what biome will be there
• knowing biome means knowing
• approximate biomass
• approximate productivity
• dominant types of organisms
• distribution of biomes
• is dependant on climate

• Climate
• a region’s average atmospheric or weather conditions over a long period of time
• results from interaction of
• physical features of earth
• two key physical factors
• amount of solar heat
• global atmospheric circulation
• determined by
• two main climatic factors
• precipitation
• temperature

• why are there variations in earth’s climate?
• different parts of earth receive different amounts of energy from sun
• uneven heating of earth’s surface due
• spherical shape
• seasonal variations because of earth’s tilt on axis
• variations in amount of energy received from sun
• responsible for
• major climatic differences on earth
• diversity in earth’s biomes

• why are tropics warmer?
• earth is sphere
• mid portions receive more energy (more direct rays) from sun than others on a per unit area basis
• tropics are warmest
• receive more sun energy per unit area
• poles are coldest
• receive less sun energy per unit area

• Two main climatic factors
• precipitation
• temperature

• precipitation
• plays vital role because
• all organisms require water
• on land, water is often scarce
• important aspects
• total amount per year
• form in which it arrives
• seasonal distribution
• affects ecosystem productivity
• ­ precipitation = ­ productivity
• generally low
• near 30° N & S latitude
• dry, descending air masses produce deserts
• all great deserts of world lie near 30° N or S latitude
• in interiors of large continents
• due to great distance from sea (ultimate source of most moisture)
• other deserts lie at continental interiors
• generally higher
• where air is rising & cooling
• releasing moisture it contains
• ability to hold moisture ¯ as temperature ¯
• near equator, most significantly
• produces tropical rainforests
• at 60° N & S latitude, to lesser extent
• produces temperate deciduous, northern coniferous, temperate rain, coastal coniferous forests
• rain shadow effect
• reduction in rainfall on side of mountains facing away from prevailing winds
• occurs most significantly in context of coastal mountain ranges
• warm, moist air in prevailing onshore winds encounter mountains
• air is forced to rise
• as air rises, ability to hold moisture ¯
• moisture leaves air as precipitation (rain, snow)
• ­ precipitation on windward slope
• air descends leeward slope
• starts out as dry mass
• having lost moisture on windward slope
• is warmed as it descended
• moisture-holding capacity increases
• inhibits precipitation
• examples
• Sierra Nevada Mountains of CA
• eastern sides much drier than western sides
• vegetation very different

• temperature
• plays vital role because
• most organisms adapted to live within relatively narrow range of temperatures
• won’t survive if temperatures are significantly warmer or colder
• example, growing season of plants influenced by temperature
• affects ecosystem productivity
• ­ temperature = ­ productivity
• affected by
• latitude
• tropical latitudes
• temperate latitudes
• elevation
• tropical latitudes
• temperatures higher
• receives more sunlight per unit area
• highest mean global temperatures occur near equator
• no seasons in tropics
• little variation in mean monthly temperature in tropical ecosystems
• temperate latitudes
• temperatures decrease
• as you move from equator toward temperate latitudes
• receives less sunlight per unit area
• seasons occur
• producing significant seasonal variations in temperature

• temperature
• affected by elevation
• decreases with increases in elevation
• at a given latitude
• normally, air temperature decreases ~6.5° C/1000m increase in elevation
• decreases with increases in elevation and latitude
• higher elevations and latitudes become progressively colder
• Temperature ¯ with ­ elevation and ­ latitude
• ecological consequences
• ­ in elevation produce similar changes in ecosystems as do ­ in latitude
• in North America, 1000m ­ in elevation results in temperature ¯ ~ to that of an 800 km ­ in latitude
• this is why "timberline" (elevation above which trees don’t grow) occurs at progressively lower elevations as one moves farther from equator
• Biomes
• terrestrial climax communities with wide geographic distribution
• concept is useful for describing in broad terms
• general structure of the ecosystem
• types of niches present
• of same type from different areas will exhibit variations in exact species present
• affected by two nonbiological factors
• temperature
• precipitation

• major biomes of the world
• desert
• grassland
• savanna
• Mediterranean shrublands
• tropical dry forest
• tropical rainforest
• temperate deciduous forest
• northern confierous forest (taiga or boreal forest)
• tundra