North American Terrestrial Ecosystems

Terrestrial Ecosystems of North America

• Focus is on adaptations of common plants and animals for each biome, common members of food chains and webs, and limiting factors

North American Biomes:

• Arctic Tundra
• Boreal or Taiga
• Rocky Mountain Evergreen
• Pacific Coast Evergreen
• Northern Mixed
• Eastern Deciduous
• Coastal Plain Evergreen
• Mexican Montane
• Rain Forest/Selva
• Prairie
• Tropical Savanna
• Cool Desert
• Hot Desert
• Mediterranean Scrub

Tundra Characteristics

• One fifth of Earth's land surface is tundra, located next to icy zones in arctic regions encircling the North Pole down to Taiga
• Alpine Tundra is located at the top of mountains above the tree line
• Climate is extremely cold, ranging from -30°C to -40°C in the winter, with an average winter temperature of -34°C
• Annual precipitation is mostly snow, measuring six to ten inches (15 to 25 cm), making it desert-like
• Winds often reach speeds of 30 to 60 miles per hour (48 to 97 km/hr)
• During winter, there are only a few hours or less of sunlight, while in summer, there is sunlight almost 24 hours a day
• Ground surface is spongy and uneven due to freezing and thawing
• Plains of tundra are covered with snow, ice, and frozen soil most of the year (permafrost)
• Highest summer temperature is only about 10° С
• Short growth and reproduction season of 50 to 60 days
• Low biotic diversity, includes about 1700 varieties of plants and about 48 varieties of land mammals
• Simple vegetation structure, limited drainage, and energy/nutrients in the form of dead organic material result in large population oscillations

Tundra Plants

• Roughly 1,700 different kinds of plants are found there
• Tiny flowering plants (4 inches or less in height), grasses, lichens - crustose and foliose, sedges, and willows
• Plants are perennials, storing food from season to season and are adapted to strong winds and soil disturbances
• Plants are short and grouped together, form little cushions close to the ground, which is warmer, and carry out photosynthesis at low temperatures and light intensities
• Plants adapt to short growing seasons by reproducing asexually

Tundra Animals

• Primary consumers (Herbivores) – lemmings, insects, musk oxen, reindeer
• Secondary consumers (Carnivores) – snow owls, arctic foxes, polar bears
• Migratory birds - ravens, snow buntings, falcons, loons, sandpipers, terns, snow birds, and various species of gulls
• Insects: mosquitoes, flies, moths, grasshoppers, blackflies, and arctic bumble bees
• Fish: cod, flatfish, salmon, and trout
• Reptiles and amphibians are few or absent

Animal Adaptations in the Tundra

• Must adapt to extremely cold winters and breed/raise their young very quickly during the short summers
• Many bird species migrate south in the winter
• Many animals hibernate during the winter, constant immigration and emigration leads to constant oscillations in population

Detritus Eaters of the Tundra

• Bacteria, Nematodes

Environmental Importance of the Tundra

• Filters millions of liters of water and stores large amounts of carbon
• Permafrost layers store organic material and Scientists can extract ice cores to research CO2 concentrations over Earth's history
• Global warming lowers the thaw depth, inputting CO2 into the atmosphere when the peat and organic matter decays

Tundra Conservation Concerns

• Large scale extraction industries pertaining to oil, gas, and minerals such as uranium
• Experiencing pollution due to chemical waste, mining, and hydroelectric development
• Expansion of agriculture/livestock, vehicular traffic, and tourism increase degradation
• With global warming, 1/3 of soil-bound carbon may be found in this area.
• Melting permafrost releases large amounts of carbon into the atmosphere, increasing “Greenhouse Effect"
• Increasing erosion due to permafrost thaw and overgrazing
• Poaching occurs via hunting and fishing out of season, on protected land, or targeting endangered species
• Like deserts, the plant systems are fragile and the ground bears human traffic marks for years
• Tundra has short food chains and only a few species of animals, which creates a fragile ecosystem in which the balance can be upset greatly if a species is reduced or diseased, either by overhunting or predation

Role of Tundra in regulating Earth's climate

• Global warming is happening at twice the rate of more temperate regions of the Earth
• Affects the release or retention of greenhouse gases such as carbon dioxide and methane
• Methane is 20 times more efficient at trapping warmth than carbon dioxide
• Soil nutrients, plant type, and plant biomass could be affected by soil moisture changes and modify amounts and types of greenhouse gases
• Climate balance could tip not just in the Arctic, but throughout the world

Taiga Characteristics

• Second largest forest in the world, rings between Arctic and Deciduous Forests at 50 to 60 degrees North Latitude and at upper elevations of mountains
• Angle of incidence for incoming solar radiation is low so twilight lasts many hours
• Divided into short, moist, moderately warm summers and long, cold, dry winters
• Temperature greatly varies from summer to winter (between -65 to +70 degrees Fahrenheit)
• Variable precipitation: 6-40 in (15-100 cm) and Soils are thin because they were scraped by glaciers and very acidic because of decomposition of pine needles
• Absence of earth-churning invertebrates such as earthworms makes the soil hard and compact but fire is a major factor in maintaining the biome

Environmental importance of the Taiga

• Filters millions of liters of water, stores large amounts of carbon, produces oxygen, rebuilds soils/restores nutrients, and bogs and marshes provide habitats for large numbers of species

Types of Plants in the Taiga

• Conifers spruce, balsam fir, and pine are major producers
• Hemlock, cedar, redwood, junipers, fungi, lichens, and mosses are prominent
• Latitude and altitude influence species, berry-producing shrubs are critical for birds, mammals, and people

Plant Adaptations in the Taiga

• Trees have upside-down cone shapes for snow slides, while their branches are flexible to hold the great weights of snow without breaking
• Trees grow thin and close together to protect from cold and wind, needles are waxy to protect from freezing temperatures and needles are present year-round and are deep green to absorb maximum warmth from the sun
• Trees have thick bark that does not easily burn, protecting inner layers from heat and seeds are protected by cones

Types of Animals in the Taiga

• Millions of insects in the summer help to feed the migratory birds
• Up to 3 billion insect-eating birds breed each year

Animal Species in the Taiga

• Seed eaters like finches, sparrows, and omnivorous birds such as crows stay all year
• Crossbills has specialized bills for prying open cones and nuthatch break the cones open
• Herbivores: small mammals, snowshoe rabbits, red squirrels, voles, and lemmings
• Predators: Owls, wolves, lynx, bobcats, minks, wolverines, weasels, mink, otters, martens, fishers
• Large herbivores: Deer, elk, and moose
• Largest predators: Grizzlies, lynx, and mountain lions feed on weakened or young deer, elk, or moose

Animal Adaptations in the Taiga

• Birds migrate south and some animals go into hibernation during winter
• Others store extra fat layers on their bodies for winter and Some animals change diets with the season
• Lynx and snowshoe rabbits grow extra fur on the bottom of their feet to tread on snow easier, animals change fur color and coat thickness with the season, and live under snow in tunnels for the winter

Taiga Conservation Concerns

• Experiencing pollution, clear cutting, illegal logging, poaching, forest fires, mining and drilling
• Pollution = chemical waste, mining, hydroelectric development
• Clear cutting means trees are cut in large sections, leaving no protection for wildlife or soil, 2.5 million acres are harvested per year with 2/3 going for newspapers promotional mailings and catalogs
• Illegal logging = logging in national parks and other protected areas without government permission
• Poaching includes hunting and fishing out of season, on protected land, or targeting endangered species
• Forest Fires = unnatural ones are caused by careless humans and mining and drilling can destroy wildlife habitats

The Taiga's Role in Regulating Earth's Climate

• Stores large quantities of carbon stored as plant material on forest floor
• One cm of plant material can hold 2.5 tons of carbon per acre
• Taiga acts like a large refrigerator, preventing decomposition, which can put carbon dioxide into the atmosphere
• Heating up the taiga is causing litter to begin to decompose, an increase in forest fires, and an infestation of bark beetles, which is killing trees

Forests Characteristics

• Forest biome is a zone where predictable tree, plant, and animal communities exist
• Predictability results from the effects of climate, soil, the presence or lack of moisture, and other physical variables
• Trees dominate biome and act as major producer
• Forests make up one-third of Earth's land area, having a global climate-buffering capacity and are considered the most biotic communities existing
• Over two-thirds of the leaf area of land plants conduct photosynthesis
• About 70% of carbon present in living things can be found here, canopy affects other organism and niches, insects, and other animals are key web components
• Potential medicines and many thousands of unseen and undiscovered species are housed
• Human civilizations that have introduced deforestation, pollution, and industrial usage problems affect for types that depend upon climate and seasonal rainfall

Forest Types

• Tropical
• Temperate or Deciduous
• Boreal (taiga) or coniferous

Temperate or Deciduous Forests

• Close relative of the Taiga biome, found in areas with milder, shorter winter seasons
• Include maple, elm, oak, cedar, in addition to evergreens that shed their leaves in the fall
• Soil is richer than that of the boreal forests, featuring a larger assortment of forest floor plant life
• Forest canopy is thinner, allowing more light and heat to penetrate, permitting photosynthesis in the forest floor plants
• Survival of smaller, cold-blooded animals such as garter snakes, turtles, and a few amphibians depends on individual adaptations through hibernation or burrowing

Climate Characteristics of Deciduous Forests

• Temperature varies from -30° C to 30° C
• Average temperature is about 50 degrees Fahrenheit
• Precipitation (75-150 cm) is distributed evenly throughout the year
• Average rainfall is 30 to 60 inches a year
• Soil is fertile, enriched with decaying litter
• Moderately dense canopy allows light to penetrate, resulting in well-developed and richly diversified understory vegetation and stratification of animals
• Deciduous trees lose their leaves in fall with spectacular fall colors, and they grow back in spring

Layers of the Temperate Deciduous Forest

• Tree stratum (Canopy) - the tallest layer, 60 -100 feet high, with large oak, maple, beech, chestnut, hickory, elm, basswood, linden, walnut, or sweet gum trees
• Small tree (Sapling Layer or Understory) - short tree species and young trees
• Shrub layer - shrubs like rhododendrons, azaleas, mountain laurels, and huckleberries
• Herb layer - short plants and Ground layer (Forest Floor) - lichens, clubmosses, and true mosses

Deciduous Forest Biome Details

• Temperate Deciduous Forest biome has four seasons of winter, spring, summer, and fall, and Animals and plants have special adaptations to cope with these yearly changes
• Deciduous trees shed their leaves once a year at the approach of a cold or dry season and later grow new leaves (evergreens keep foliage throughout the year.)

Adaptations of Deciduous Forest

• Deciduous trees usually have broad leaves e.g., ash, beech, birch, maple, and oak
• Flora characterized by 3-4 tree species per square kilometer with species like oak, hickory, beech, hemlock, maple, basswood, cottonwood, elm, willow, and spring-flowering herbs that are lost annually
• In SUMMER broad green leaves help capture sunlight needed to make food through photosynthesis
• Falling temperatures cause the tree to cuts off the supply of water to the leaves, sealing off the area between the leaf stem and the tree trunk
• Leaves are unable to continue producing chlorophyll, causing them to change colors
• In winter, trees lose their leaves because they cannot protect them from freezing, which conserves water loss through transpiration (dried leaves continue to hang on the branches of some deciduous trees until the new leaves come out.)
• Before the leaves die, some of the food material they contain is drawn back into the twigs and branches, the temperatures of spring signal trees to grow leaves again

Deciduous Forest Animal Adaptations

• Must be able to cope with cold winters when food is in short supply through migration and hibernation
• Typical animals include squirrels, rabbits, skunks, birds, deer, mountain lions, bobcats, timber wolves, foxes, and black bears
• Great variety of birds migrate to warmer places where they can find food more easily
• Some mammals (e.g., bears) hibernate (inactive, sleeplike state to protect themselves against the cold and reduce their need for food.)
• Hibernating animal's body temperature is lower, heartbeat and breathing slows, needing little energy to stay alive and living off fat stored in its body, and can survive cold winter months
• Squirrels, chipmunks, and some jays often store large supplies of food (nuts and seeds) for use during the cold winters when food is scarce, with cold temperatures helping prevent the decomposition of the nuts and seed

Environmental Concerns with Deciduous Forests

• Many of the world's great tracts have experienced significant alteration through logging, agriculture, and urban development
• Industry adjacent to these forests may pollute air and water resources
• Species introduced to temperate deciduous forests by humans may become invasive and threaten native ecosystems

Defining Biodiversity

• Biodiversity- “variability among living organisms"
• Walter Rosen coined the term in 1985, representing the number of different organisms & their relative frequency in an ecosystem, variability of genus, of varieties, of species, of populations in different ecosystems, and finally relative abundance of species
• About 50 million species of plants, animals & microbes are estimated to exist in the world, but only 2 million are identified so far
• Crucial in sustainable resource utilization, Biological resources such as food, clothing, housing, fuel, medicine, and revenue

Importance of Biodiversity

• Different species with different traits in an environment can support different functions in the ecosystem
• Removing a species can impact all in the ecosystem due to interdependence
• Medicines that people rely on come from species existing in our bio diverse world
• Agriculture depends on these diverse landscapes
• Some species have cultural value to communities, maintenance of that is important
• Biodiversity has intrinsic benefit, and should be protected, as well as creates opportunities for eco tourism
• Declines in certain species will lead to increased health risks such as coral reefs and mangrove forest that can reduce storm surges and other hazards
• Green spaces will improve both mental and physical health

Levels of Biodiversity

• Genetic diversity: varies in the genetic make-up among individuals within a single species
• Species diversity: variety among the species or distinct types of living organisms found in different habitats of the planet
• Ecological diversity: variety of forests, deserts, grasslands, streams, lakes, oceans, wetlands, and other biological communities and Variations in the community that make up parts of the ecosystem

Types of Biodiversity

• Genetic, organismal, population, species, community, ecosystem, landscape, biogeographic, intraspecific, functional
• Different types can be observed in nature

Definitions for Types of Biodiversity

• Genetic: diversity in the alleles of a single gene
• Organismal: differences in morphology, anatomy, or behavior of organisms
• Population: variations observed in quantitative ecological parameters such as frequency, density, abundance
• Species: Measures the variation in species numbers at a particular habitat
• Community: among community composition of an ecosystem and variations in the ecological interactions
• Ecosystem: deals with the variations of interdependence of biotic and abiotic factors in the ecosystem
• Landscape: measures the species compositions in different landscapes
• Biogeographic: observed in geological and geographic history over a large period of time
• Intraspecific: in the genomic and phenotypic traits found within and among populations
• Functional: variety and range of functional traits within a biological community or ecosystem

Stability in Species versus Ecosystem

• Higher diversity = higher stability
• Need a minimum threshold of species diversity needed to maintain stability, in terms of environmental factors

Species Diversity Levels

• Alpha, beta, gamma

Species Diversity Levels, Defined

• Alpha: within habitat diversity, refers to a group of organisms interacting and competing for the same resources of that environment
• Beta: along transects & gradients, refers to spatial heterogeneity and organism response, is implied by low similarity, is a function of similarity index
• Gamma: Larger geographical unit

Alpha, Beta, and Gamma

• Alpha diversity - measured locally, at a single site
• Beta divesrity - measures the amount of change between to sides for along a gradient depending on variable of regions
• Gamma - similar to alpha, but only over a measured at a large scale, both also contribute to similar diversity

Measuring Biodiversity

• Measured using diversity indices by software programs like estimates
• Components of biodiversity are richness and evenness
• Richness= quantity
• Evenness= quality

Terms Regarding Measuring Biodiversity

• Richness = Number of groups of genetically or functionally related individuals
• Evenness = proportions of species or function groups

Terminology for Measurements

• Species richness: simplifies measure, divide number of species by that square route of number of individuals
• Species diversity: takes into account both number of species and dominance Formula
• • Shannon-Wiener index: measures entropy to see relationships

Components for Measuring

• Proportion of individuals in population
• Should only be used on random samples
• Measures the degree of order in the region = Diversity/evenness measure

Advantages and Disadvantages of Shannon-Wiener's Index

• All must be represented
• Easy to Calculate
• Sensitive to change

Simpson's Index

• Index=D D = Σn(n - 1)/N(N - 1) N = Total n = organism

Simpson's index, Ranges from one to zero if they are diverse •Simpson's Diversity Index = 1 – D •Simpsons Reciprocal Index = 1/D

• Aids in understanding
• Gives
• Community

Simpson Advantages

• Works well with small samples
• Doesn't -species
• Measures
• Sensitive
• Weighted towards most abundant species