Biomes, Climate Change, and Biogeochemical Cycles: Ecology and Earth Systems

Climate conditions that determine a biome

average annual temperature, precipitation

Biomes organized by temperature

tropical rainforest, tropical seasonal forest/savanna, subtropical desert, temperate rainforest, temperate seasonal forest, woodland/shrubland, temperate grassland/cold desert, boreal forest (taiga), tundra

Biomes organized by precipitation

tropical rainforest, temperate rainforest, tropical seasonal forest/savanna, temperate seasonal forest, woodland/shrubland, temperate grassland/cold desert, boreal forest (taiga), tundra, subtropical desert

biomes shift in location

Example of biomes shifting as a result of climate changes = warming climate will shift boreal forests further north as tundra permafrost soil melts & lower latitudes become too warm for aspen & spruce

littoral zone

the area near the shoreline of a body of water, where sunlight penetrates to the bottom and allows aquatic plants to grow

limnetic zone

open and well-lit, no photosynthesis

profundal zone

too deep for sunlight, no photosynthesis

benthic zone

murky bottom, nutrient-rich sediments

wetland

area with soil submerged/saturated in water for at least part of the year, but shallow enough for emergent plants

coastal plane estuary

valleys with gentle sloping, depth increases toward mouth

tectonic estuary

created when the sea fills a hole or basin that's formed from sinking land

bar-built estuary

formed when sandbars build up along the coastline and partially cut off the waters behind them from the sea

fjord estuary

narrow with steep sides, usually straight and long, found in areas that glaciers have covered

photic zone

area in ocean where sunlight can reach (photosynthesis)

aphotic zone

area too deep for sunlight

resource partitioning

different species using the same resource in different ways to reduce competition

temporal partitioning

using a resource at different times

example of temporal partitioning

wolves and coyotes hunting at different times of day

spatial partitioning

using different areas of a shared habitat

example of spatial partitioning

two bird species might occupy different heights on the same tree, one at the top and one at the bottom

edge effect

the changes in population or community structures that occur at the boundary of two or more habitats

tundra

Coldest biome, low precipitation, permafrost, short growing season, mosses, lichens, migratory animals

taiga (boreal forest)

Cold, dense coniferous trees, acidic soil, long winters, short summers

temperate deciduous forest

Four seasons, moderate precipitation, deciduous trees, fertile soil

temperate rainforest

Mild temperatures, high rainfall, coniferous trees, somewhat nutrient-poor soil

grasslands (savanna and temperate)

Dominated by grasses, distinct wet and dry seasons (savanna) or cold winters and warm summers (temperate), fertile soil

desert (subtropical and others)

Very hot and dry, low rainfall, sparse vegetation, adapted plants (cacti)

chaparral (woodland/shrubland)

Hot, dry summers, mild, wet winters, fire-adapted plants

carbon cycle

movement of molecules that contain carbon (carbon dioxide, glucose, CH4/methane)

steps of carbon cycle

photosynthesis, cellular respiration, burial/decomposition, direct exchange, combustion

burial/decomposition

some carbon can be buried in the soil or ocean floor and decompose

direct exchange

CO2 in atmosphere and CO2 dissolved in water are constantly exchanged

Imbalance

an imbalance in which reservoirs or sinks are storing carbon

Combustion

human extraction of fossil fuels brings carbon to Earth's surface, where it can be combusted

Carbon sink

a carbon reservoir that stores more carbon than it releases

Example of carbon sinks

Ocean (algae, sediments) and forests, (plants, soil)

Cellular respiration

done by plants/animals to release stored energy, uses oxygen to break glucose down and release energy/CO2

Burial

over long periods of time, pressure of water compresses CO2-containing sediments on the ocean floor into sedimentary stone (limestone, sandstone)

Stages of nitrogen cycle

nitrification, nitrogen fixation, assimilation, ammonification, denitrification

Major reservoir of nitrogen

atmosphere

Nitrogen fixation

process of N2 gas being converted into biologically available (usable by plants) NH3 (ammonia) or NO3 (nitrate)

Two types of fixation

bacterial and synthetic fixation

Bacterial fixation

certain bacteria that live in the soil, or in symbiotic relationship with plant root nodules convert N2 into ammonia NH3

Example of bacterial fixation

rhizobacteria live in root nodules of legumes (peas, beans) & fix N for them in return for amino acids from the plant

Synthetic fixation

humans combust fossil fuels to convert N2 gas into nitrate NO3

Example of synthetic fixation

nitrates are added to synthetic fertilizers like miracle grow and used in agriculture, lightening strike turns nitrogen gas into a solid, blue-green algae and bacteria turns nitrogen gas into a solid, bean plants extract nitrogen gas from the air, condensation

Nitrogen assimilation

plants/animals absorb nitrates by the roots

Nitrogen ammonification

decomposers like bacteria and fungi break down organic nitrogen compounds (like in dead plants and animals, or animal waste) into ammonia (NH3) or ammonium (NH4+)

Nitrogen nitrification

bacteria change ammonium to nitrates to be absorbed by plants

Nitrogen denitrification

a microbial process that converts nitrate (NO3-) in soil and water into gaseous forms of nitrogen (N2, N2O, and NO), ultimately releasing them into the atmosphere

Greenhouse gases

warms earth's climate. Produced by denitrification of nitrate in agricultural soils (especially when waterlogged/over-watered)

Ammonia volatilization

excess fertilizer use can lead to NH3 gas entering atmosphere

Effects of NH3 gas in the atmosphere

acid precipitation, respiratory irritation in animals, less nitrogen in soil for crops

Leaching

excess water washes dissolved nitrogen (mostly as nitrate) out of the soil, below the root zone, and potentially into groundwater.

Negative consequence of leaching

Nitrates runoff into local waters, causing algae blooms that block sun & kill other aquatic plants.

Eutrophication

Excess nutrients that algae growth caused by too much nitrogen/phosphorus.

Process of eutrophication

Fertilizer runoff or human/animal waste contamination → too much nitrogen and phosphorus → algae growth → algae bloom covers water surface and blocks sunlight, killing plants below → algae eventually die off, bacteria that break down dead algae use up O2 in water → lower O2 levels in water kills aquatic animals (especially fish) → bacteria use up even more O2 to decompose dead animals.

Nitrogen reservoirs

All living things (plants, animals, microbes), soils, and aquatic ecosystems.

Processes that help move nitrogen

Nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

Human impact on nitrogen cycle

Fertilizer use, fossil fuel burning, raising livestock, and wastewater runoff.

Areas with higher levels of NO₂

Industrialized and urban areas (like cities and regions with heavy traffic or factories) — because of combustion of fossil fuels and industrial emissions.

Effect of soil moisture on nitrogen cycle

Too wet increases denitrification (N₂O released, a greenhouse gas), too dry slows microbial processes like nitrification and decomposition.

How humans produce usable nitrogen

Production of synthetic fertilizers, burning fossil fuels, livestock waste.

Effect of plant health on nitrogen cycle

Healthy plants take up more nitrogen (keeping it in the cycle); unhealthy plants reduce uptake, leaving more nitrogen in soil and water.

Mineralization

The process where microbes decompose organic nitrogen in dead organisms and waste into inorganic ammonium (NH₄⁺).

Higher sea levels effect on nitrogen cycle

Flooding can move nitrogen into coastal waters, fueling eutrophication.

Lower sea levels effect on nitrogen cycle

Reduces nitrogen transport to oceans, may alter coastal ecosystems.

Stages of phosphorus cycle

Weathering, assimilation, sedimentation/geographical uplift.

Phosphorus weathering

Wind/rain break down rock/phosphate (PO4-3), which is released and dissolved into water. Rainwater carries phosphate into nearby soils & bodies of water.

Phosphorus assimilation

Phosphorus is absorbed into animals and plants.

Phosphorus sedimentation

Phosphate doesn't dissolve very well, most of it forms solid bits of phosphate that fall into the bottom as sediment.

Phosphorus geological uplift

Tectonic plate collision forcing up rock layers that form mountains, phosphorus cycle can start over again with weathering.

Need for phosphorus

All organisms need phosphorus for DNA, ATP, bone & tooth enamel in some animals.

Phosphorus from synthetic sources

Synthetic fertilizers containing phosphates are added to lawns/agricultural fields and the runoff carries it into nearby bodies of water.

Transpiration

Process plants use to draw groundwater from roots up to leaves. Low water potential in leaf.

Evapotranspiration

Amount of water that enters atmosphere from transpiration & evaporation combined.

Primary Productivity

Rate that solar energy is converted into organic compounds via photosynthesis over a unit of time.

Net Primary Productivity (NPP)

The amount of energy (biomass) leftover for consumers after plants have used some for respiration.

Respiration loss (RL)

Plants use up some of the energy they generate via photosynthesis by doing cellular respiration (movement, internal transportation, etc.).

Gross Primary Productivity (GPP)

The total amount of sun energy (light) that plants capture and convert to energy (glucose) through photosynthesis.

Ecological Efficiency

Portion of incoming solar energy that is captured by plants & converted into biomass (NPP or food available for consumers).