Ecosystems Module 2

Ecosystem

a set of all orgs within a space and the totality of all interactions of these orgs with one another and the physical enviro

ecosystems are central to what…

ecology is

what is missing in the definition of ecosystem in terms of geography

“within a space'“ indicates a spatial relationship but no indication of what the space is

• no beginning or end

• no boundaries

physical enviro examples

soil, water, rocks, sunlight, atmosphere

• central to the life of org

what does the physical enviro represent to them?

energy (sunlight), availability of mineral (nitrogen, carbon, magnesium, etc) from rocks or soil or breeding

types of system

• open system

• closed system

open system

exchanges both energy and matter with surroundings

• could be one or the other as well

• infinite source of energy (solar radiation)

open system example

everglades

• energy comes from sun

• feeding plants

• heat with atmosphere

• thunderstorms and evaporation

• exchanges of materials from north to south florida to ocean

closed system

energy and matter are not exchanged with the surrounding environment

• one or other or both

• energy can be left out if infinite and matter is more important

closed system example

not many on surface of earth

• planet itself can be

  • don’t lose matter to rest of universe as well

why are most systems open

• dispersal

• exchanges of energy and matter

reductionism

breaking apart complex phenomenon into simpler constituent parts of ease of analysis

what does reductionism mean in ecology

examining relationships among orgs and their enviro one at a time

• fish in lake worth to restoration with sea grass and mangroves

  • how do they respond to the project

• subset of orgs

holism

studying the entire phenomenon as a complete whole

• whole may be greater than the sum of its parts

  • not taking into account as much as should be

what is a result of holism

synergism

super-organism

• part of a larger whole

• organs

• classical idea

diff ways of studying ecosystem

• reductionism

• holism

which way to study ecosystem is better

• reductionism is more frequent in research on ecosystems

• holistic is way more expensive , time consuming, and need more labor than we have available

ecosystem processes (function)

chemical or biological activities/events that link orgs to their environment

examples of ecosystem process

• macro-scale models

  • nutrient cycling

  • energy cycling

  • water cycling

• specific processes (sub-parts of cycle)

  • production, decomposition, consumption, deposition, etc

nitrogen cycle

• nitrogen into soil

  • dry or wet deposition

  • bacteria takes it out of air

• fixed into ammonia

• converted into nitrites and nitrates

• plant assimilation

• consumption

• defecation, death, decomposition, ammonification

• denitrifying bacteria

ecosystems function …

• create these cycles

• orgs to interact with each other

• orgs to interact with physical enviro

how can ecosystems be quantified

• biomass

• productivity

biomass

weight (wet or dry) per unit area of the total living biological material can also be broken down by community or taxonomic group in an area

production

amount of biomass, organic matter per area, that accumulates over a given time

what factors does production depend on

• moisture

• nutrient availability

• temperature

• growing season length

how can production be broken down

• primary production - primary (photosynthetic)

• net primary production - production of primary producers minus the energy used for metabolic activity

• secondary production - consumer production

what ecosystem is highest in NPP

tropical rainforest (terrestrial)

swamps and marshes (aquatic)

coral reef and algal bed (aquatic)

trophic level

the place in the food chain that an org occupies. an ecosystem in its essential form is about the transfer and cycling of nutrients and energy

why is biomass in each higher trophic level less than lower levels

only about 10% of energy is transferred up

• less indivs and sp at higher trophic levels

trophic cascade

an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling

• top down control

trophic cascade example

yellowstone wolves

• removal by government

• reintroduced

• scaring and eating elk

  • not eating everything

• beavers came back bc they were scared of elk

food web

interaction among org in an eco based on which sp are consuming other sp including sp from trophic structure

biodiversity

degree of variation of life in a system, can incorporate genetic, habitat, and sp diversity ( age-class, life history, life form, functional group, ecosystem, landscape diversity)

main aspects of diversity

• genetic

• habitat

• species

genetic diversity

the variety of info stored in gene pool

habitat diversity

number of habitats in a given area

species diversity

number of sp in a given area (sp richness)

• the more sp the more stable the eco

  • not always true rule

why is biodiversity important to eco stability

the greater variety of primary producers and prey sp can provide a more solid base on which trophic level org persis

shannon diversity index

• s = # of sp

• pi = proportion of indiv in a community belonging to sp i

alpha

diversity within a particular area or eco, and is usually expressed by a number of sp (ex. sp richness) in that eco

beta

change in sp diversity between two compared eco (ex. total number of sp unique to the eco being compared)

gamma

overall diversity for the diff ecosystems within a region

common eco paramters

• structure - vertical arrangement of veg. and soils

• composition - sp. present and abundance, often lumped with structure (measured in diversity usually)

• pattern - horizontal arrangement (part of eco structure)

• heterogeneity - composite of 1-3 and the variability over space and time

• function - perform basic processes (ex. water, energy, nutrients, etc)