Exploring Global Biomes and the Impact of Disturbances on Biodiversity
Sources of Complexity in Ecology
- Variability: Graphical presentation and statistics
- Integrative: Interactions among numerous variables
- Contingency: Sequence of events matters
These sources are interconnected.
Branches of Ecology
- Ecology: Study of where things live, “oikos”
- Physiological Ecology: Organismal level
- Population Ecology: Species level
- Community Ecology: Study of the distribution, abundance, and interactions of co-existing populations
Evolution and Phylogeny
- Evolution: Study of change in the genetic composition of a population during successive generations; can result in the appearance of new species. The major mechanism is natural selection.
- Phylogeny: Study of the historical relationships among species
Biodiversity
- Taxonomy: Classification, identification, and naming of organisms
- Phylogenetic: Study of evolutionary relatedness among groups of species
- Species Richness: Counting the number of species
- Genetic Diversity: Within a species
The Tropics and Solar Radiation
- Tropics: Experience the greatest input in solar radiation.
- Near the equator, solar radiation travels a short distance through the atmosphere and strikes a small surface area; the sun’s energy is spread out over a small area.
Global Air Circulation Patterns
- 6 total major convection cycles, 3 on each side
- At the equator, there is a lot of solar energy coming in.
- Latitudes are north to south.
- As air is warmed, it gets less dense and rises.
- The spin of the Earth causes friction on some air masses – Coriolis Effect.
- As air rises, it gets cooler and forms condensation.
- Air moves from high to low-pressure areas.
- The Earth’s rotation deflects the air movement to create global wind patterns.
- Always name wind from where it came from (example: westerlies came from the west).
- When we cut down forests, we change the weather.
Ocean Currents
- Redistributes heat, influences the distribution of nutrients
- Gyre: Spin-like current
- Causes garbage patches in the ocean
- Movement from the equator brings hot water which then cools at higher latitudes.
- Wind going parallel to the coast will cause surface current to flow away from the coast which then causes water from higher depths to rise.
- Fisheries use the tracking of these to help their business.
Coastal Habitats
- Kelp forests and mangroves are found around the world.
- Mangroves are better about trapping nutrients.
Seasonality
- Summer Solstice: Midday sunlight strikes Earth more directly in the Northern Hemisphere—the Sun is higher in the sky and casts smaller shadows.
- Winter Solstice: The opposite of the summer solstice
- Seasonality is determined by Earth’s tilted axis of rotation and its annual passage around the sun.
- Equinoxes: Day length in the tropics is exactly 12 hours.
Factors That Affect the Local Environment
- Large bodies of water (reduces temperature swings) – high specific heat of water
- Topography: Hills and slopes, mountains and rain shadow
- Aspect: Direction slope is facing and how it affects moisture and temperature
- Angle of Slope: Affects drainage
- Altitude
- Bedrock: Type determines the type and composition of soil which determines plant species in an area
Large Bodies of Water
- Warm air over the land rises and moves over water, cool air sinks over water and is blown back over land.
- At night, the cycle reverses.
- At dawn and dusk is when the shift happens.
- Temperature ranges in the Southern Hemisphere are smaller than those of the Northern Hemisphere.
- More water in the Southern Hemisphere, which has a more stable temperature
Mountains
- Basin: A large flat area
- Rain Shadow: Coastal water is carried in and hits the mountains on the windward side.
- Aspect
- North-facing slope: Less solar radiation, cooler, less evapotranspiration
- South-facing slope: More solar radiation, warmer, dryer, greater evapotranspiration
- Only for the Northern Hemisphere
- Altitude
- Lower Montane Zone: Highest temperature, lowest precipitation
- Montane Zone
- Subalpine Zone
- Alpine Zone
- For every 1km increase in elevation, you decrease the temperature by 3.6 degrees Fahrenheit, the same as going 700 miles north.
- Bedrock: Affects the habitat that is grown
- Endemic Plants: Found only in one specific region
The Physical Environment and Biological Systems
- Variations in the physical environment underlie the diversity of biological systems.
- The physical environment ultimately determines where organisms live (distribution).
- The physical (abiotic) environment varies widely over the Earth’s surface.
- Spatial and temporal variation
- Diverse, mosaic of habitats
Distribution of Major Terrestrial Biomes
- Largely determined by temperature and mean precipitation
Tropical Rainforests
- Hot, little variation in temperature throughout the year
- Average precipitation is on average 200 cm per year
- Usually, a dry and wet season, but not a huge change between them
- Usually located near the equator
- Infertile soil but high species richness
- Only the top surface of the soil has nutrients in it.
- Greater than 50% of the world’s terrestrial species can be found in tropical rainforests.
- Most nutrients are in the living biomass.
- Intense competition for light, water, nutrients
- In one hectare, there will be between 40 and 300 species of trees.
- 1500 species of butterflies per square mile
- During this lecture, we will lose 3 species from the tropics.
Savannas and Tropical Seasonal Forests
- Found a bit north and south of the tropics
- A bit of seasonality in temperature
- Very distinct wet and dry seasons
- Less rain on average than the tropics
- More fertile but can still be nutrient-poor
- Bedrock is so far away.
- Dominant Vegetation: Mix of grass and forbs
- Forbs: All non-woody plants besides grass
- Increase in grass, decrease in trees as you move further away from the equator
- Home of large herbivores – giraffes, kangaroos
- Occasional fires are used for maintenance – adapted for this and seasonal drought.
Temperate Woodlands and Scrublands
- When it is hot, it’s dry.
- Found in the Mediterranean coast, South Africa, California
- Lots of endemics in this region
- Mild, wet winter
- Adaptation to fire and seasonal drought
Desert
- Very low precipitation
- Seasonal variation in temperature can depend on the location of where they’re located.
- 25-degree N and S latitude
- High sand content in soil, infertile, low water-holding capacity
- Plant-life is sparse and low to the ground
- Succulents: Cacti
- Might be a tiny bit of a rainy season – causes a flush of wildflowers
Temperate Grassland
- Dominated by grasses
- Located farther north and south of the equator
- Large temperature range – hot summers and cold winters
- Soil is deep and fertile.
- Farms are usually placed here.
Temperate Deciduous Forests
- Average temperature is a little bit lower.
- Average precipitation is a bit higher.
- Water is frozen in some portions of the year.
- Lots of plants lose their leaves.
- Soil is relatively rich.
- Dominant Vegetation: Trees – oaks, maples, birches
- Much of the area is being logged.
Boreal Forests – Taiga, Northern Coniferous
- Higher in latitude
- Average precipitation is quite low.
- Temperature varies seasonally.
- Very long summer days, long winter nights
- Low diversity in tree species
- Largest terrestrial biome
- Little understory vegetation
Tundra
- Northern limits of plant growth
- Open, boggy community
- Little rain
- Temperature range is mostly below freezing.
- Soil: Permafrost – ground is frozen within a meter of the surface (infertile)
- Perennial shrubs, flowers, mosses, lichens
Aquatic Biomes – Largest Part of the Biosphere
- Pelagic Zone: Open water
- Benthic Zone: Layer at the bottom of the ocean or a lake
- Many aquatic biomes are physically and chemically stratified.
- Layering has to do with where you are in regards to the surface.
- Photic Zone: Close to the top of the water, light reaches
- Layering with respect to pressure and nutrients
- Lakes
- Oligotrophic: Clear, lacks some nutrients
- Eutrophic: Too much of one nutrient, forms a deoxygenated zone
- Wetlands: Inundated by waters at least some of the time – Among the most productive biomes
- Estuaries: Transition area between river and sea
- Coral Reefs
- Low nutrients in the water column but are high in biodiversity
- Shallow and deep sea
- Intertidal Zones: Periodically submerged and exposed, changes in physical conditions
- Ocean Pelagic Zone: Covers approximately 70% of the world’s surfaces
- Marine Benthic Zone: Very high pressures
Biodiversity
- The number of species – about 1.9 million known, named species living today
- Undiscovered species numbers vary greatly.
- Genetic variation within a population
- Genetic variation across populations
- Ecosystem diversity
Biodiversity: Known and Estimated
- Mammals: 5,487 known, 5,500 estimated
- Birds: 9,990 known, 10,000 estimated
- Insects: 1 million known, 5 million estimated
- Vascular Plants: 281,621 known, 368,050 estimated
- Bacteria and Archaea: 7,643 known, 1 million estimated
- We are currently in the age of discovery with new technology and a great motivation to make sure species don’t go extinct without science knowing.
- In 2016, 17,000 species were discovered.
- Half were insects.
- 25% of all known amphibians have been discovered in the last 10 years.
- 86% of terrestrial and 91% of marine species have yet to be discovered.
- Mekong River Watershed
- Between 1997-2007, over 1,000 new species have been discovered and described.
- About 2 species a week
- 519 plants, 279 fish, 88 frogs, 88 spiders, 46 lizards, 22 snakes, 15 mammals
Conservation Diplomacy
- In some regions of the world, conflict and politics make it difficult to study biodiversity.
- 80% of armed clashes in the last 50 years have been in areas of high biodiversity.
- New species discoveries likely to happen in Cuba
- Wilderness buffers between countries can lead to further dialogue and peace.
- Peru/Ecuador border
Values of Biodiversity
- Aesthetic value
- Ecosystem integrity
- Economic value – ecosystem services to people are worth trillions of dollars worldwide.
Spatial Scales of Disturbances
- Disturbance: A relatively discrete event in time that removes organisms or otherwise disrupts the community by influencing the availability of space or food resources, or by changing the physical environment.
- Small Disturbances (less than 1000 hectares)
- Secondary successions
- Medium Disturbances (1000 hectares to millions of hectares)
- Primary succession
- Dynamic equilibrium
- Large Disturbances (continents to global)
- Mass extinctions
- Speciation
Small Disturbances
- Secondary Succession: Starts with a disturbance that removes most of the vegetation
- Differs from primary succession because it does not start from bare ground.
- Forest clearing through logging
- The process by which the biological community of a given site changes over time (usually following a disturbance)
- Species composition changes over time.
- Pioneer/early-successional species: Better dispersal
- These species are eventually replaced by late-successional species (more competitive).
- If no disturbance, climax species come to dominate.
- Each organism not only responds to the environment but also modifies it and, in doing so, becomes part of the broader environment itself.
- At a larger spatial scale, all species can coexist, despite even a high frequency or severity of disturbances.
- Spatial heterogeneity
- A mosaic of patches recovering from different levels of disturbance that occurred at different times in the past
- Patches of differing sizes and ages provide a wide variety of environmental conditions.
- Each patch is occupied by species adapted to its niche.
- Shifting Mosaic: Add a temporal component to the spatial model above
Primary Succession
- Harsh abiotic conditions, initial species develop soil