ESS Topic 2.5 - Zonation and Succession

Zonation

Changes in community composition along an environmental gradient (like altitude and distance from water)

Examples of Zonation

Mountains: vegetation shifts from forests to alpine meadows ro bare rocks

Seashores: Tidal zones with distinct species like barnacles and mussels

Intertidal Zonation

Wave action, salinity, temperature, and submersion (time of exposure to open air) are abiotic factors that organisms have to adapt to to live in the environment. (watch the video on slide 7 maybe)

Montane Zonation

Different altitudes goin down a mountain call for different communities of agriculture and livestock in the different altitudinal zones. Temperature and oxygen availability are the major abiotic factors determining the zones. Ultraviolet radiation could also be a factor

Ocean Zonation

Going down into the ocean from the sand, will find different zones. Major abiotic factors seen are light availability, pressure, temperature, and salinity

Littoral Zonation

Going down into a lack from the ground there will be changes is soil humidity, oxygen availability (for the roots), and as one enters the lake, light availability and temperature will change

Tidal Deltas

Rivers near the sea will be different around the world, like mangroves are found in tropical and sub-tropical areas. Some abiotic factors to note in deltas are the degree of submersion, salinity, variability of salinity, temperature, oxygen availability during submersion, and wave/water velocity

How to measure zonation

use transects to study biotic and abiotic factors along the gradient , uses a kite diagram to visualize species distribution

Application of data

fieldwork, place quadrats along the transect to record species and conditions

Succession

the natural, gradual changes in communities in an area over time

Primary Succession

Has an environment start from zero, meaning there is no soil or organisms that exist

Example of Primary Succession

Islands made from underwater volcanoes will only have rock on them, lichen will grow on the rocks and break down the rocks, the lichen will die adding nutrients to the newly developed soil which will allow plants to start growing

Pioneer Species

The first species to populate this newly developed area, travel y wind or water, break down rocks to soil, die, and allow plants to grow

Example of a Pioneer Species

Lichen, breaks up rocks

Step 1 to Primary Succession

Start with bare rock

Step 2 to Primary Succession

Pioneer species such as lichen start to grow

Step 3 to Primary Succession

As pioneer species die soil creation occurs. Plants can grow in this new soil

Step 4 to Primary Succession

As more plants die, they decompose creating fertile soil. Maturing plants thrive and new plant communities grow

Secondary Succession

more common and includes the series of changes that occur in an area where the soil had been disturbed (usually by a natural disaster), by where an ecosystem still exists

Step 1 to Secondary Succession

An event occurs to disturb the soil (like fire, farming, logging)

Step 2 to Secondary Succession

In a short period of time, grasses and tree seedling repopulate the soil

Step 3 to Secondary Succession

As trees begin to grow they crowd out many low-growing plants

Step 4 to Secondary Succession

Eventually a mature tree community becomes established

Climax Community

the stable balance of all organisms within a community, will remain stable unless a disaster occurs and the cycle of succession has to start all over again

Sere

The sequence of vegetation types which occur in primary succession

Xerosere

Ecological succession that occurs in dry environments. Like deserts and rocky areas

Hyrdosere

Ecological succession that occurs in wet environments. Like lakes, ponds, and wetlands

Lithosere

Ecological succession that occurs on barren rock surfaces. Like lava flows, glaciated areas, and landslides

Biotic Factors Influencing Succession

Birds contribute to soil enrichment via pooping (guano), aiding nutrient cycling

Abiotic Factors Influencing Succession

Proximity to the ocean brings seeds and organic debris

Succession is Temporal

Zonation is Spacial

Changes Over Time in Succession

Productivity increases, species richness grows (biodiversity), and depth and nutrient cycling in soil improves

Importance of Ecosystem Resilience and Stability

Enhances ecosystem resilience to disturbances and promotes long-term stability

Human Impacts on Ecosystem Resilience and Stability

Activities like deforestation reduce resilience by decreasing biodiversity

Pioneer Stage

Energy flow is simple and low efficiency, gross productivity is low, net productivity is relatively high, species diversity is low, soil depth is shallow

Early Successional Stage

Energy flow has an increased efficiency, gross productivity is high, net productivity is high, species diversity is low to moderate, soil depth has increased

Mid Successional Stage

energy flow is more complex, gross productivity is high, net productivity is high, species diversity is moderate, soil depth has increased depth with organic matter accumulation

Late Successional Stage (Climax)

energy flow most complex and efficient, gross productivity us high, net productivity is low, species diversity is high, soil depth is deepest with rich organic layer

Climatic and Geological Factors Shaping Succession

Steep slopes limit soil formation

Biotic Influences Shaping Succession

Wolves in Yellowstone reshaping trophic cascades

Early Productivity Patterns during Succession

Low GP (harsh conditions) High NP (biomass builds)

Late Productivity Patterns during Succession

High GP and Larger consumers; NP ≈ 0 in climax communities.

r-strategists and K-strategists in Succession

these species have reproductive strategies that are better adapted to pioneer and climax communities

r-strategists

many offspring and shorter lifespan

K-strategists

fewer offspring and longer lifespan

Plagioclimax

human activities halt of redirect succession (like grazing and forest management)

Diverted seres

Sometimes the natural sequence of succession is halted or diverted by some external factor which influences the vegetation structure or community composition

Fire

environmental constraints are applied by grazing animals and by fire, resulting in stable grassland communities maintained by heavy grazing pressure or regular fires

Grass vs. Shrubs and Trees

Grasses are fire-resistant and can recover faster than shrubs or trees, regulate fires help maintain grasslands by preventing shrub and tree encroachment

Impact of Herbivores

close cropping by herbivores removes fire-prone long grass, this absence allows unpalatable shrubs to dominate in some areas