Chapter 5Environmental Systems &

Ecosystem Ecology

The study of Earth’s Systems include Abiotic Systems, Biotic Systems, and the interactions between the two.

In the environmental sense, a System is composed of a series of components that interact following the Input of energy, matter, or information.

These systems use various Inputs (resources) to produce a result (or an Output).

In our bodies, examples of systems include our mental activities. Information is an input, our brain processes the information using what we have seen and learned during our lifetimes and thoughts are the Output of this system. Other body systems include the Central Nervous System, the Digestive System, the Respiratory System,…all interconnected.

Properties/Concepts that define systems:• Inputs - of Energy, Matter, Information• Throughputs – Processing of Inputs• Outputs – the Results• Negative Feedback Loops – slow the system• Positive Feedback Loops – speed up the

system• Time delay - usually not consistent• Outputs usually serve as Inputs for other

systems.

Consider streams as an example of a system – that changes from the mountains to the sea.

Very low gradient, low water energy, lower oxygen content, higher temperature, high biodiversity

Inputs Abiotic – • Water – direct runoff, contributions from

streams, rainfall• Temperature changes – the results of

varying amounts of sunlight, water depth, water energy, elevation

• Variations in water chemistry due to runoff & local rainfall, differences in sediment characteristics (rocky bottom vs. sandy bottom vs. muddy bottom)

InputsBiotic –

Differences in biota due to water chemistry, water depth, water energy, gradient, water temperature

Consider which organisms dwell permanently within the stream and which dwell temporarily.

Consider actions of Keystone Species – Beavers, Alligators,…to system

In an aquatic ecosystem, in consider-ation of the abiotic components – each species has its own Range of Tolerance for each input (nutrient). Under normal circumstances, organisms should be able to tolerate gradual changes in a nutrient. Figure 5.4 describes what happens when a particular nutrient (N) suddenly increases and/or another nutrient decreases independently or because of the N increase.

Throughputs Chemical Reactions that take place within

the stream and the Biological Life Cycles of all organisms within the stream.

These abiotic and biotic reactions are going to be largely affected by water temperature.

Higher temperatures – faster chemical reactions.

Higher temperatures – more biological activity w/in Range of Tolerance

Within Temperate Deciduous Forest biome – a Rotting Log sub-Ecosystem

The Rotting Log Ecosystem begins as:

1)A live tree blown down during a storm;

2)A dead tree that is blown down during a storm or collapses due to decay.

Abiotic inputs - Rainfall, temperature, sunlight vs. shade, elevation

Biotic inputs - Bacteria, termites, slugs, roaches, ants, animals that take shelter temporarily

As time passes, the fallen log is “invaded” by termites, centipedes, roaches, ants, worms, etc.. Warm temperatures and sufficient rainfall facilitate this biological activity.

With the gradual accumulation of debris falling from the log to the ground, a transition zone is created. When the log dries during drought, organisms can migrate into the soil, until moisture returns to the log.

Debris apron = transition zone between the rotted log and the soil

Examples of Fungi Decomposers – that live on dead or dying wood

Moisture facilitates fungal growth, as well as the unseen bacteria

Ecosystem Productivity depends upon the availability of necessary nutrients, which include:

Sunlight, Oxygen, Nitrogen, Phosphorous, Potassium, Sulfur,…

And of vital importance is Water and favorable temperatures. The most productive terrestrial ecosystems are in humid Tropical to Sub-tropical settings.

In a prior chapter, Landscape Ecology was described as the study of various ecosystems. In the study of a given area, the Landscape Ecologist would identify the ecosystems and sub-ecosystems as well as the boundaries between the systems (Ecotones). A mosaic is the distribution of different ecosystems over an area.

In Ecotones where there are interspersed fragmented, small ecosystem, Conservation Biologists can study the migration of individuals between the ecosystem patches.

In these Colorado mountains, there is a Mosaic of sub-ecosystems.

One of the issues studied by Ecologists is what happens with Habitat Fragmentation.

In the previous slide, prior to the clearing of the hardwood forest, there was a continuous ecosystem, which included some plants and animals which prefer the “center” of the forest. When the ecosystem was fragmented, that changed the conditions of the narrow strip of remaining forest. The light conditions have changed for remaining plants and trees, i.e., the get the low-angle “morning sun” that is new to them = the “Edge Effect”.

Secondary Succession “blurs” the boundary between grassy area and forest.

Biogeochemical Cycles/Nutrient Cycles

Hydrologic Cycle (Water Cycle) – The continual movement of water as it cycles through the Hydrosphere, Atmosphere, Lithosphere, and Biosphere.

The water that falls on the land surface through Precipitation enters the subsurface by Infiltration or remains as surface water through Runoff.

Recalling the Polarity of water and how it facilitates Cohesion (between water molecules) and promotes chemical reactions – as water moves, so move nutrients and pollutants.

In other words – the Water Cycle affects many other cycles, e.g., the Rock Cycle (by dissolving minerals and rocks), and any other element or compound that can be dissolved in water. It also affects the vitally important Carbon Cycle.

Consider the ways that we affect the Water Cycle when we –

1)Cut down forests, losing “Transpiration” which transmits moisture from plants to the atmosphere;

2)Build a dam across a river or build irrigation canals in a humid climate vs. an arid climate.

More evaporation in an arid climate.

14 Carbon Cycle & Various Sinks & Processes

Examples of the ways in which CO2 gas can enter the ocean is by:1)Dissolved CO2 gas being carried in rivers to the oceans or in melting icebergs.2)CO2 being exchanged between the atmosphere and the ocean surface.3)Respiration by aquatic animals and bacteria.4)Underwater volcanic eruptions and emissions from ocean-bottom vents.

Carbon is stored in the oceans as dissolved CO2 gas, organic compounds, Carbonate (CO2

=) and Bi-carbonate ions (HCO2

-).

Certain algae remove Calcium ions (Ca++) and Carbonate ions to form Calcite (CaCO3) for their internal structures – resulting in the “removal” of CO2 during the deposition of limestone.

Other ways Carbon is “stored” in the oceans:

1)Suspended organic matter.

2)Organic matter deposited as part on sedimentation, especially if not consumed by scavengers in deep (and or restricted) basins, such as the Gulf of Mexico.

The ways in which aquatic temperatures affect the Carbon Cycle

1) The colder the water is (including ocean water), the more CO2 gas can be stored. This is called the “Coca Cola Principle”. Inversely, as the water warms, CO2 gas rises and is released into the atmosphere. This slightly increases the pH of the water.

2) As the water warms, the algae that “produce” limestone become more active – if other conditions are favorable. There will probably be other organisms (molluscs, corals, bryozoa, etc.) that remove CaCO3 from the water for their exoskeletons.

Warm waters have more biodiversity than do cold waters. Also, having sunlight w/in the “photic zone” is important to the plants.

The Biodiversity of fossils in this limestone suggests shallow, warm water.

2 Ways in which humans affect the Nitrogen Cycle:

1) Automobile catalytic converters alter stable N2 gas to NOx gases – that when mixed with rainwater may produce nitric or nitrous acid.

2) Use of Nitrogen in fertilizers (incl. animal manure). If there is too much for soil bacteria & plants to use, nitrate & nitrite pollution can affect ground water and surface waters.

An example of how humans affect the Phosphorous Cycle:

Phosphorous is needed for the growth of grasses (for livestock) or crops.

When the livestock or crops are removed from the farm area, the phosphorous is removed and thus needs to be replenished before the next farm cycle.