Ecology - Chapter 2
Large geographic regions characterized by the community (particularly the predominant vegetation) in the region, and the adaptations of the plants and animals to a specific climate.
Whittaker's system is an oversimplification of reality for multiple reasons
- there are not sharp graidents from one system to another
- Soils can play a role in the type of system that can survive—for instance poor soil quality may not allow a forest to exist in a region otherwise able to support one.
- Humans have greatly altered systems.
Northern Hemisphere - Spring Quinox
as the equator faces the sun and the next hemisphere has autumnal equinox
Southern Hemisphere - Autumnal Equinox
as the equator faces the sun and the spring equinox happens in the next hemisphere
Northern Hemisphere - Summer
As it tilts toward the sun and the next hemisphere has winter as...
Southern Hemisphere - Winter
As it tilts away from the sun and the next hemisphere has summer
Northern Hemisphere - Winter
as it tilts away from the sun and the next hemisphere has summer
Southern Hemisphere - Summer
as it tilts toward the sun and the next hemisphere has winter
Northern Hemisphere - Autumnal Equinox
as equator faces the sun and the next hemisphere has spring equinox
Southern Hemisphere - Spring Equinox
as the equatr faces the sun and the next hemisphere has autumnal equinox
More Light Energy is absorbed and reflected by the atmosphere
therefore less light energy reaches earth's surface
Atmospheric Circulation is driven by
Differential heating of the Earth's surface along with the fact that hot air rises and cool air sinks
occurring without loss or gain of heat
heat absorbed or released during a phase transition
(current vapor pressure/saturation vapor pressure) x 100
Dew Point Temperature
the temperature at which the air will become saturated with water, resulting in the formation of dew—cold air can hold less moisture than warm air.
Solid to Liquid
Liquid to Gas
Gas to Liquid
Liquid to Solid
Solid to Gas
Gas to Solid
__ the first to propose a simple model of atmospheric circulation
a phenomenon that causes fluids, like water and air, to curve as they travel across or above the Earth's surface
Polar Cell - above 60N
Polar high - sparse precipitation in all seasons
Artic Tundra, Taiga
Ferrel Cell - 30o - 60o N
Subpolar low- ample precipitation in all seasons
Winter wet, summer dry
Temperate Deciduous forest and grasslands
Hadley Cell - 0-30N
Subtropical High - dry in all seasons
Summer wet, winter dry
Equatorial low - (ITCZ) Abundant precipitation in all seasons
Tropical Rain Forests ( on the equator), Tropical Deciduous Forest, Desert
Hadley Cell - 30S - 0
Equatorial low - (ITCZ) Abundant precipitation in all seasons
Summer wet, winter dry
Subtropical high - dry in all seasons
desert, tropical deciduous forest
Ferrel Cell - 60-30S
Winter wet, summer dry
Subpolar low - ample precipitation in all seasons
Polar Cell - below 60S
Polar high - sparse precipitation in all seasons
Due to the Coriolis Effect, winds are always deflected...
right in the Northern Hemisphere
left in the Southern Hemisphere
*relative to there direction
When wind hits a mountain and is forced to rise over the mountain
Organic horizon, A horizon, B horizon, C Horizon
Upper Layer contains loose, somewhat fragmented plant litter. Litter in lower layer is highly fragmented.
loose and partly decayed organic matter
Mineral soil mixed with some organic matter. Clay, iron, aluminum, silicats, and soluble organic matter are gradually leached from this horizon
Mineral matter mxied with some humus
Zone of Eluviation and Leaching
Depositional Horizon. Materials leached from A horizon are deposited in this horizon. Depositis may form distinct banding patterns
Accumulation of clay, iron, and aluminium from above
Weathered parent material. This horizon may include many rock fragments. It often lies on bedrock.
Partially altered parent material
Unweathered parent material
decomposed organic matter found in soil. It is generally aerobic for part of the year, dark brown or black and is mixed by soil organisms (e.g., earthworms) to lower layers.
the transportation of dissolved or suspended material within the soil by the movement (percolation) of water through the soil.
the draining of soluble materials (e.g., chemicals and minerals from soil by percolating water—especially rainwater).
an area of land made up of limestone
What level of ecological inquiry does a biome entail
At what latitude is the northern/southern boundary of the tropics?
Why is. the tropic zone defined by the 30Latittude
The earth is tilted on its axis by that number of degrees
The Dew point is described as
the temp at which air will become saturated with water
the point at which relative humidity is 100%
As air moves south from the equator it will be traveling to the east faster than the land and thus
This is the depositional horizon of soil. These deposits can create distinct bands
Water Climate Diagram shows
- mean monthly temperature as given on the left axis
- mean monthly precipitation
- mean minimum temp for the is above freezing
- mean minimum temp for the month is below freezing
- average minimum temp. for the min temp is above freezing
- dry conditions
Tropical Rainforests - Geography
Most occur within 10o latitude of equator. However, outside of this equatorial band, rainforests can be found in Central America, Mexico, southeastern Brazil, eastern Madagascar, southern India and northeastern Australia
Tropical Rainforests - Climate
- There is generally very little temperature variation between months. Temperatures average around 25-27oC
- Annual rainfall ranges between 2,000 - 4,000 mm; rainfall is generally evenly distributed - there is not a wet and dry season.
Tropical Rainforests - Soils
The heavy rainfall leaches soil nutrients. Often nutrients are found in the forest’s biomass (epiphytes)
- soils are often very acidic, thin, and low in organic content
- Insects on the forest floor rapidly shred plant litter, and fungi and bacteria break the plant litter down further making it available for living plants to absorb.
- Fungal mycorrhizae form mutualistic relationships with plants, which help them gather nutrients.
- Harbor staple foods and medicines for world's human populations - 25% of all prescription drugs derived from these
Tropical Rainforest - Biology
- Trees add a vertical dimension to the forest, allowing plants and animals to specialize in different sections of the forest canopy.
- Rainforests have extremely high diversity. 1 ha of rainforest (about 2.5 acres) can have 300 species of trees.
- A single rainforest tree can host thousands of species of insects—many partitioning the canopy by specializing in different strata.
- Symbiotic relationships and mimicry are replete in rainforests
Four Distinct strate representing zones of different vegetation in Tropical Rainforest
Canopy, Subcanopy, Understory, Ground Layer
Tropical Dry (Deciduous) Forest - Geography
- Tropical dry forests are usually located between 10o - 25o latitude
- they are found in the Americas, Africa and Asia/Australia
Tropical Dry Forest - Climate
- more seasonal than tropical rainforest, with distinct rainy and dry seasons. Rainy seasons can last for 5-6 months, with dry seasons lasting 6-7 months.
- Although warm throughout the year, there is slightly more of a temperature change throughout the year in tropical dry as compared to tropical rain forests.
Tropical Dry Forest - Soils
- generally richer in nutrients (less acidic than tropical rain forests and richer in nutrients), but vulnerable to erosion due to torrential rains that come at the end of the dry season.
Tropical Dry Forest - Biology
- The biology of this biome is affected by abiotic factors—particularly climate. For instance, in wetter forests, up to 50% of the trees may be evergreens, whereas in drier forests, all tree will be deciduous.
- Forest canopy height is influenced by the amount of rain—with the highest canopies associated with the greatest rainfall.
- Many animals including insects, mammals and birds may migrate from tropical dry to tropical rainforests.
Tropical Dry Forest - Human Influences
- Untouched tropical dry forests are almost nonexistent—this is particularly due to the fact that the soil is more conducive to converting to farmland than tropical rainforests.
- Loss of dry forests has resulted in a lot of endemic species—species only found in specific localized dry forest habitat.
Tropical Savanna - Geography
- Most occur north and south of tropical dry forests within 10o - 20o of the equator.
- In Africa, they are expansive spanning almost the entire width of the continent from the Atlantic Ocean to the Red Sea, just south of the Sahara Desert.
- In South America, they are found in Columbia, Venezuela, and south-central Brazil. They are also found in much of Northern Australia.
Tropical Savanna - Climate
- Climate alternates between wet/dry seasons (drier than tropical dry forests).
- Rain occurs during the summer, generally in a short, very intense burst.
- Drought associated with dry season leads to lightning-caused wildfires.
- The fires kill trees, (particularly saplings). Grass will quickly resprout, which helps maintain the savannah's structure—you should understand how “succession” is related here.
- Some savannahs can receive as much rainfall as dry forests. What prevents the trees from growing in these areas is the quality of the soil.
Tropical Savanna - Soils
- some savannas are maintained by fire, due to an extended dry season (these are called climatic savannas).
- Some savannahs receive enough rainfall to support trees, but the soil conditions prevent trees from growing (these are called edaphic savannas)
- This often occurs because the soil can become water-logged with water during the wet season, which results in low oxygen in the soil, preventing tree roots from surviving.
- In drier areas, these types of soils help to hold enough moisture to allow grass to grow, where a desert would otherwise occur.
Tropical Savanna - Biology
- The flora is dominated by different species of grasses—the types of grass depend on the amount of rainfall and type of soil.
- There are a few trees on the savanna. Flora on the savanna are well adapted to fire. Termites play a significant role in increasing soil nutrients locally, which helps support trees in the habitat.
- Most animals found in the savanna are migratory, moving with the seasons following rainfall.
- Animals partition the habitat, even eating different sections of grass, so as to not compete with each other.
Tropical Savanna - Human Influences
- Humans can trace their evolution to the savanna environment. Early humans hunted in these biomes, and later used the habitat for agriculture.
- However, population growth is putting extreme pressure on these habitats today, and this creates conflict, as domesticated animals are much easier target to predators in this biome. There are groups working to help locals make a living, while preserving the predators that call the savanna home.
Desert - Geography
- Major bands at 30o N and 30o S latitude. This corresponds to the region of the Hadley cells where warm dry air descends after rising from the equatorial belt.
- Deserts occupy about 20% of earth’s land surface.·Some deserts exist due to mountains, which create rain shadows as moist air rises on one side of the range (orographic lifting).
- Some deserts occur along continental coasts, where there is significant warming by the sun, but currents continually bring cool water from more southern climates.
- The Namib of southwestern Africa is an example of this type of desert.
- Water loss usually exceeds precipitation.
Desert - Soil
- often extremely low in organic matter (often called lithosols—i.e., stone or mineral soil).
*Animals can greatly influence local soil nutrient content. For instance, in the American Southwest, kangaroo rats can greatly increase nutrient content of soil by creating burrows—they bring seeds into these burrows, and their waste acts as fertilizer.
- In deserts that do not drain well after rain , the water evaporates leaving dissolved minerals behind. This increases the salinity of the soil.·When soils become more saline, it is even more difficult for plants to absorb water from the soil.
As desert soils age they often form a hardpan of calcium carbonate called caliche. In general, the older the desert the thicker the caliche layer.
Desert - Biology
- Plant cover ranges from sparse to absent.
- Plants have a range of adaptations to the dry conditions.
- For instance, the spines of a cactus are actually leaves. The spines protect the plant and reduce water loss.
- Some plants only produce leaves after it rains, and then drop them when the rain stops.
- Some plants remain dormant in the soil as seeds, only sprouting when it rains.
- Animal abundance (number of individuals per species) is low, but biodiversity (number of different types of species) may be high.
- Animals exhibit strong behavioral adaptations to the heat.
Mediterranean Woodland and Shrubland - Geography
- Occur in all continents except Antarctica.
- Most extensive around the Mediterranean Sea.
- Also found in North America (California to Northern Mexico); central Chile, southern Australia and southern Africa
Mediterranean Woodland and Shrubland - Climate
·Climate cool and moist in fall, winter, and spring, but can be hot and dry in summer.
Mediterranean Woodland and Shrubland - Soils
-Fragile soils (subject to erosion, particularly after fires and overuse by humans) with moderate fertility.
Mediterranean Woodland and Shrubland - Biology
- Trees and shrubs typically evergreen.
- Fire-resistant plants due to fire regime.
- Long history of human intrusion.
- Cleared for agriculture.
Temperate Grassland - Geography
- Extremely widespread distribution in both the central United States and Eurasia
- In the United States, before settlers moved in, the “prairies”of the Great Plains extended from southern Canada to the Gulf of Mexico, and from the front range of the Rocky Mountains in the west, almost all the way to the Mississippi River in the east.
- The map below shows where the grasslands occurred before settlers converted the habitat to agriculture. The different shading indicates different types of grasses
- In Eurasia, they form a band from eastern Europe to eastern China
Temperate Grassland - Climate
- Annual rainfall 300 - 1,000 mm. Different species of grasses are adapted to live in areas of different levels of rainfall.
- Periodic droughts are common—you may have learned about the dustbowl of the 1930’s. What keeps agriculture going today in the prairies is not rainfall, but groundwater.
Temperate Grassland - Soils
- Soils tend to be extremely nutrient rich and deep. This is due to a combination of factors, including the deep root systems of the grasses, and the animals (including bison and prairie dogs) that added their fertilizer to the soil.
- After the dust bowl period, a lot of the soil’s nutrients were washed away. They are often maintained today by artificial fertilizers.
Temperate Grassland - Biology
- Like tropical grasslands, periodic drought and hot summer temperatures encourage fire. This prevents trees from taking hold. Thus plants herbaceous—plants without woody stems·Thus trees and shrubs are restricted to riparian zones (margins rivers)
- In addition to grasses, eudicot wildflowers are common.·In drier areas short grass species dominate (often only 5 cm in height). In wetter areas tall grass species dominate—getting up to 200 cm tall.
- The iconic animal species of the great plains is the bison. It is estimated that before Columbus arrived, there were 30 million bison roaming the great plains.
Temperate Forest (Old Growth) - Geography
- Majority lie between 40o and 50o latitude but can be found as far south as 30o.
- Temperate forests once covered huge swaths of North America and Eurasia.
Temperate Forest - Climate
- Rainfall averages between 650 - 3,000 mm.
- Temperatures are “temperate”—literally means not tropical and not polar.
- In colder areas, or areas where the summer is drier conifers tend to dominate.
- In milder areas, or areas with more summer rainfall, deciduous hardwood trees dominate
Temperate Forest - Soils
- Soils are usually fertile—particularly in deciduous forests, whose trees drop their leaves in the fall, producing a rich soils.
- Coniferous forests can have rich soils also, but due to the tannins in their needles, the soil tends to be more acidic.
- The forest floor is home to many insects that shred plant material along fungus and bacteria that recycle the nutrients back into the soil
Temperate Forest - Biology
- Species richness (number of different species) is generally much lower in temperate forests than in tropical forests, but the biomass production can be very high—even as high as tropical rainforests.
- Temperate forests are vertically stratified as in tropical forests.
- The redwood forests and “temperate rainforests” of the Pacific Northwest are famous examples of these habitats
Temperate Forest - Human Influences
Many major human population centers and agriculture now stand where old growth forests once existed.
Boreal Forest (Taiga) - Geography
- Confined to the Northern Hemisphere in a band between 50-65oN latitude.
- The area covered by these forests is huge ~ 11% of earth’s land area.
- To the south of these forests is either temperate forests or temperate grasslands. To the north is tundra.
- The altitude of mountains can create favorable habitat further south. For instance, boreal forests follow the Rocky Mountains south.
Boreal Forest (Taiga) - Soil
- Because these forests are dominated by evergreen conifers, the needles create an acidic soil.
- The cold temperatures prevents rapid decomposition of the plant matter, resulting in thin, acidic soils that are low in fertility.
Boreal Forest (Taiga) - Climate
- Winters are long—generally longer than 6 months long, and very cold. Summers are short.
- Temperatures can swing from -70oC in the winter to 30oC in the summer.
- Precipitation ranges from about 200 to 600 mm. But low winter temperatures and long winters means there is not a lot of evaporation and drought is infrequent.
Boreal Forest (Taiga) - Biology
- Generally dominated by evergreen conifers such as spruce and fir. Larch trees (a deciduous conifer) dominates in extreme Siberian climates. There are few herbaceous plants, but shrubs such as blueberry and juniper are common.
- Large herbivorous mammals are common migratory caribou (winter), moose, bison. Predators such as wolves, black and grizzly bears are also common.
- In addition to the large mammals noted above, smaller mammals such as lynx, snowshoe hare, porcupines and red squirrels also live in boreal forests.
- smaller mammals such as lynx, snowshoe hare, porcupines and red squirrels also live in boreal forests.
- Many tropical birds migrate to these forests in the summer months.
- Historically, low levels of human intrusion.
Arctic Tundra - Geography
- Covers most of lands north of Arctic Circle—i.e., north of 60o. If you go north of the tundra, in most locations you will find the Arctic Sea.
Arctic Tundra - Climate
- typically cold and dry with short summers—shorter than the boreal forests.
- Rainfall averages between 200 - 600 mm each year, so it is very dry. But the cold temperatures ensure that precipitation exceeds evaporation
Arctic Tundra - Soil
- Because of the low temperatures and short summers, decomposition rates are low—so deposits of peat and humus accumulate over time.
- Surface layers of soil thaw each summer, but just beneath the surface, the soil is permanently frozen. This permanently frozen soil is appropriately called permafrost.
- When surface soil thaws in the spring and summer, if it is on a slope, the wet soil will begin to slide over the frozen permafrost below, down the slope. This process is called solifluction.
- Tundra soil often has a unique polygonal pattern that is created by continual freezing and thawing which brings stones to the surface.
Arctic Tundra - Biology
- The habitat is too cold for trees and woody shrubs. It is dominated by herbaceous plants, especially grasses, and sedges. In addition moss and lichen are very common.
- Caribou, reindeer, musk ox, bear and wolves are common in the tundra (caribou migrate to the tundra from the boreal forests during the short tundra summer).
- Small mammals (arctic foxes, weasels, lemmings and ground squirrels are common)
- There are native birds, such as the snowy owl, and lots of migratory birds fly north for the short summer.
- Insect diversity is low, but mosquitoes and fly populations explode during the summer.
- Human intrusion historically low but increasing as resources become scarce—particularly for oil exploration.
Mountains: Islands in the Sky - Geography
- Built by geological processes and thus concentrated in belts of geological activity.
Mountains: Islands in the Sky - Climate
Climate changes with elevation and latitude. It can also change depending on which side of the mountain you are on (remember orographic lifting and rain shadows!)
Mountains: Islands in the Sky - Soils
- Steep topography means soils are generally well-drained and thin—of course, rainfall combined with slope can easily result in erosion.
- Wind can result in the accumulation of organic material in cracks and crevices of a mountain slope.
Mountains: Islands in the Sky - Biology
- Flora and fauna change with elevation—changes in altitude can mimic changes in latitude.
- Thus, mountain ranges can provide a variety of biomes in a relatively small geographic range due to the change in elevation and the resultant change in temperature and precipitation.
Large scale weather variation—the Walter climate diagrams describe the macroclimate
Small scale weather variation (measured over kilometers, meters or even centimeters).
In the Northern Hemisphere, the shaded areas are
on the north-facing side (northern aspect);
in the Southern Hemisphere the shadded areas are
the south-facing slope (southern aspect) faces away from the equator and is more shaded.
Microclimates - Vegetation
- Vegetation shades the landscape creating microclimates—in a desert, a few meters is the difference between hellish heat, and a moderately warm day!
Darker colors absorb more visible light, lighter color reflects it
Boulders / Burrows
Create shaded, cooler environments.
- Water can absorb lots of heat without large temperature changes.
* It takes 1 cal to heat 1 cm3 of water 1o C.It only takes 0.0003 cal to heat 1 cm3 of air 1o C! So it takes 3000 times more energy to heat or cool the same amount of water as air
Latent Heat of Evaporation
- It takes 580 cal (from the environment—cooling the air) to evaporate 1 g of water. Conversely 580 cal is released to the air (heating the air) as 1 g of gaseous water condenses into liquid water.
Latent Heat of Fusion
1g of water gives off 80 cal as it freezes and removes 80 cal to freeze
In an old growth temperate forest, soils will tend to be more acidic in:
The thawing of surface soil in the tundra can result in surface soil sliding over deeper frozen soil. This is called..
Solifluction " soil fluctuation"
Which of the following is an example of the statement "changes in altitude can mimic changes in latitude" /
Boreal forests found in the Rocky Mountain
If Earth's climate is warming, which of the following would be predicted to relative to mountains:
Biota altitudes zones should shift up (to higher altitude)
What happens to local air temperature when water evaporates
it cools off
All of the following are true except
- In a cold desert, evaporation only exceeds precipitation during the summer
- Solifluction is common on slpoped terrain during the summer in the tundra
- Taiga boreal forests are dominated by a few species of conifer trees and have thin, acidic soils
- Epiphytes play an important role in nutrient storage in tropical rain forests
Trees shed their leaves during the dry season of a temperate deciduous forest
Where on earth would you predict the sun would be directly overhead (overhead sun light rays coming in perpendicular to the ground) on March 21 or September 21?
If a body of air has a temperature of 30oC at sea level what will that same body of air's temperature be if it rises to 2500m altitude?
for every 1000m we lose 10 sea
orographic lifting will cause air to rise and cool on one side of a mountain, and will subsequently descend down the other side. What type of biome might this happen
Which of these answers best explains these data?
As one move further North or South from the equator, sunlight strikes the earth at a greater angle than it does closer to the equator
What is the role of the taiga (boreal forest) biome in the graph below?
Photosynthesis fixes enormous amounts of CO2 during the Northern Hemisphere summer causing seasonal drops in atmospheric CO2.
heat that is absorbed or released during a phase transition is called:
Strictly above 60oN latitude which of the following terrestrial biomes is most likely to be found?
Which of the following are logically or likely true about this system based on these data?
Succulent plant that use crassulacean acid metabolism (CAM) are likely very common in this biome
Which of the following regions is most responsible for Earth's large scale atmospheric patterns?
0-30 degrees N/S latitudes