Ecology Trees Flashcards
The biosphere is the zone of life on Earth
It lies between:
The lithosphere—Earth’s surface crust and upper mantle
The troposphere—the lowest layer of the atmosphere
Tropical rainforests:
Between 10°N and 10°S
Abundant rainfall
High biomass, high diversity—about 50% of Earth’s species
Light is a key factor— plants must grow tall or adjust to low light.
Tropical seasonal forests:
North and south of the wet tropics
Wet and dry seasons
Shorter trees, deciduous in dry seasons, more grasses and shrubs
Fires promote establishment of savannas—grasses with intermixed trees and shrubs.
In Africa, large herbivores—wildebeests, zebras, elephants, and antelopes—also influence the balance of grass and trees.
Deserts:
At high pressure zones, 30° N and S
High temperatures, low moisture
Sparse vegetation and animal populations
Low water availability constrains plant abundance but diversity can be high.
Humans use deserts for agriculture and livestock grazing.
Agriculture depends on irrigation and results in soil salinization.
Long-term droughts and unsustainable grazing can result in desertification—loss of plant cover and soil erosion.
Temperate grasslands: midwest
Between 30° and 50° latitude
Warm, moist summers and cold, dry winters
Grasses dominate; maintained by frequent fires and large herbivores such as bison
High soil fertility
Most grasslands of central North America and Eurasia have been converted to agriculture.
In arid grasslands, grazing by domestic animals can exceed capacity for regrowth, leading to grassland degradation and desertification.
Irrigation in some areas causes salinization.
Temperate shrublands and woodlands: deciduous
Between 30° and 40° latitude
Evergreen shrubs and trees
Mediterranean-type climates—cool, wet winters and hot, dry summers
Evergreen leaves: plants can be active during cool, wet winters; lowers nutrient requirements—plants don’t have to make new leaves every year.
Sclerophyllous leaves deter herbivores and prevent wilting. - hard herbivores get energy
Fire is common and helps maintain the biome. Without regular fires at 30- to 40- year intervals, shrublands may be replaced by forests.
Some temperate shrublands have been converted to crops and vineyards, but the soils are nutrient-poor.
Urban development has reduced the biome (e.g., in southern California). More frequent fires reduce the ability of the vegetation to recover, and invasive grasses can move in.
Temperate deciduous forests: syracuse
30° to 50° N, on continental edges with enough rainfall for tree growth
Leaves are deciduous in winter - lose leaves every season
Oaks, maples, and beeches occur everywhere in this biome
Species diversity is lower than tropical rainforests
Temperate evergreen forests:
30° to 50° N and S, coastal, continental, and maritime zones
Temperate rainforests: high rainfall and mild winters; located on west coasts.
Lower diversity than tropical and deciduous forests
Leaves tend to be acidic, and soils nutrient-poor
Fertile: nutrients nitrogen and phosphorus
Temperate forests: human impact
Trees are used for wood and paper pulp, and these biomes have been logged extensively.
Very little old-growth temperate forest remains.
In some areas, trees have been replaced with non-native species in uniformly aged stands.
Suppression of fires in western North America has increased density of forest stands, resulting in more intense fires when they do occur, and increases spread of pathogens and insect pests
Boreal forests (Taiga):
50° to 65° N
Long, severe winters
Permafrost (soil that remains frozen year- round) prevents drainage and results in saturated soils
Trees are conifers—pines, spruces, larches—and birches
Cold, wet conditions limit decomposition in soils; soils have high levels of organic matter.
In summer droughts, forest fires can be set by lightning and can burn both trees and soil.
Peat bogs form in low- lying areas.
Tundra:
Above 65° latitude, mostly in the Arctic
Cold temperatures, low precipitation
Short summers with long days
Vegetation: sedges, forbs, grasses, low growing shrubs, lichens, and mosses
Widespread permafrost
Boreal forests: human impact
Boreal forests have not been as affected by human activities.
Logging and oil and gas development occur in some regions. Impacts will increase as energy demands increase.
Climate warming may increase soil decomposition rates, releasing stored carbon and increasing greenhouse gas concentrations.
Tundra: human impact
Human settlements are sparse; this biome has the largest pristine areas on Earth, but human influence is increasing as exploration and development of energy resources increases.
The Arctic has experienced significant climate change, with warming almost double the global average.
Hconv = Convective heat transfer
heat carried through water or air
Hcond = Conductive heat transfer
energy transferred molecule to molecule
