Ecology: Community Structure & Ecosystem Services David Mellor, PhD Citizen Science Coordinator Virginia Master Naturalists

Overview of Ecology Definition and Scope Energy and Food Webs Nutrient Cycles Population Dynamics Ecological Interactions Community Structure Ecosystem Services Human Impacts

Community Structure Species Diversity Keystone Species Disturbance Succession

Species Diversity Species Richness – The number of species in an ecosystem Relative Abundance – The amount of a species in a given ecosystem Species Diversity – Considers BOTH richness and abundance – There are many ways to measure diversity

Richness Higher (3 species) Lower (1 species)

Species Diversity Species Richness – The number of species in an ecosystem Relative Abundance – The amount of a species in a given ecosystem Species Diversity – Considers BOTH richness and abundance – There are many ways to measure diversity

Abundance Higher Low

Species Diversity Species Richness – The number of species in an ecosystem Relative Abundance – The amount of a species in a given ecosystem Species Diversity – Considers BOTH richness and abundance – There are many ways to measure diversity

High Richness, Low Abundance

High Abundance, Low Richness

Keystone Species An organism whose role in the environment is “critical.” Species Dominance – Role of organisms in an environment may not be directly related to the number of individuals e.g. Numerous understory trees may play less of a role than a few canopy species that determine light levels.

Disturbance and Stability Stability – The tendency of a community to reach and maintain an equilibrium, or relatively constant condition, in the face of disturbance Community resilience – The ability of a community to persist in the face of disturbance

Disturbance

Ecological Succession The change in community composition over time. – Primary succession: creating a new ecosystem, such as after a volcanic eruption creates new land – Secondary succession: community change in an existing habitat. – Pioneer species: Early to inhabit a new community – Seral stage: Each stage of the succession process, may last months to decades – Climax community: A mature community that no longer exhibits change in species composition

Ecological Succession The change in community composition over time. – Primary succession: creating a new ecosystem, such as after a volcanic eruption creates new land – Secondary succession: community change in an existing habitat. – Pioneer species: Early to inhabit a new community – Seral stage: Each stage of the succession process, may last months to decades – Climax community: A mature community that no longer exhibits change in species composition

Ecological Succession The change in community composition over time. – Primary succession: creating a new ecosystem, such as after a volcanic eruption creates new land – Secondary succession: community change in an existing habitat. – Pioneer species: Early to inhabit a new community – Seral stage: Each stage of the succession process, may last months to decades – Climax community: A mature community that no longer exhibits change in species composition

Ecological Succession The change in community composition over time. – Primary succession: creating a new ecosystem, such as after a volcanic eruption creates new land – Secondary succession: community change in an existing habitat. – Pioneer species: Early to inhabit a new community – Seral stage: Each stage of the succession process, may last months to decades – Climax community: A mature community that no longer exhibits change in species composition

Ecological Succession The change in community composition over time. – Primary succession: creating a new ecosystem, such as after a volcanic eruption creates new land – Secondary succession: community change in an existing habitat. – Pioneer species: Early to inhabit a new community – Seral stage: Each stage of the succession process, may last months to decades – Climax community: A mature community that no longer exhibits change in species composition

Ecological Succession The change in community composition over time. – Primary succession: creating a new ecosystem, such as after a volcanic eruption creates new land – Secondary succession: community change in an existing habitat. – Pioneer species: Early to inhabit a new community – Seral stage: Each stage of the succession process, may last months to decades – Climax community: A mature community that no longer exhibits change in species composition

Ecological Succession Disturbance (e.g. abandoned farm) Annual plants (“weeds”) Perennial weeds and grasses Woody Shrubs Young pine forest Mature hardwood forest Time

Succession

Intermediate Disturbance Hypothesis Frequency of Disturbance Events Biodiversity

Question Why does a community change over time following a disturbance?

Ecosystem Services An ecosystem process that leads to a service from which humans benefit.

Ecosystem Services ProcessServicesBenefits NitrificationConverting Ammonia or Nitrite to Nitrate or Atmospheric Nitrogen Clean Drinking Water DecompositionUsing non-living organic matter for energy Removing disease- spreading matter, Soil creation PollinationGrowth of fruit or reproduction of useful plants Fruit, nuts, timber, seeds PhotosynthesisCapturing carbon dioxide, creating sugars Food production, Carbon capture, Breathable air

Some ecosystem services could be replaced by humans. – Wastewater treatment plants All ecosystem goods and services have a value. – How much money are the food resources worth? – How much is our soil worth? – How much money do we spend on recreation in the outdoors? Ecosystem Services

Some ecosystem services could be replaced by humans. – Wastewater treatment plants All ecosystem goods and services have a value. – How much money are the food resources worth? – How much is our soil worth? – How much money do we spend on recreation in the outdoors? Ecosystem Services

Included estimates of 17 services: Regulating gasses, climate, water; soil formation, nutrient cycling, waste treatment, pollination, food production, raw materials, recreation, etc.

Ecosystem Services $16 - $54 trillion per year (World GDP = $18 trillion)

(Costanza et. al., 1997) US Dollars per Hectare per Year

Worksheet Describe an ecosystem service that occurs in an natural area near your home.