Transcript assimilation at trophic level n

Ecosystem Ecology
Basic ecosystem - nutrient cycling in red, energy flow in grey
Basic Energy Flow
Basic Energy Flow
Energy Flow Expanded
Energy Flow in Different Ecosystems
Transfer Efficiency
10% Rule for Transfer Efficiency
Consumption Efficiency
• CE = food ingested/food produced
• How much of prey population that consumer
eats
• For herbivores – 5% in forests, 25% in
grasslands, 50% in phytoplankton ecosystems
• For vertebrate predators – up to 50-100%
vertebrate prey; 5% invertebrate prey
• For invertebrate predators – 25% invertebrate
prey
Assimilation Efficiency
• AE = food assimilated/food ingested
• How much of prey eaten is digested
• AE usually low for herbivores,
microbivores, detritivores – 20-50%
• AE usually high for carnivores – 80%
Production Efficiency
• PE = new biomass produced/food assimilated
• How much of prey digested is converted to
consumer biomass and used in reproduction –
rest is lost as respiratory heat
• PE high for invertebrates – 30-40%
• Intermediate for ectotherm vertebrates – 1020%
• Low for endotherm vertebrates – 1-2%
For Example – Caterpillar Efficiency
Efficiency of Energy Transfer
(Production Efficiency)
E = P/(P + R)
where
E = efficiency
P = net production
R = respiration
• Some representative
efficiency values are as
follows:
• birds 1.3%
• small mammals 1.5%
• large mammals 3.1%
• fish 10.0%
• herbivorous insects 39%
• carnivorous insects 56%
• detritivore insects 47%
Lindeman’s Efficiency
• LE = assimilation at trophic level n
assimilation at trophic level n – 1
LE examines efficiency of transfer between
trophic levels – often assumed to be 10%
but…is actually more complex
Light Absorption
Lindeman’s Efficiencies
Decomposition
Decomposition
• Role in ecosystems – decomposition is gradual
disintegration of dead organic matter and is
brought about by both physical and biological
agents
• decomposers - organisms which convert organic
elements to inorganic form - mostly bacteria and
fungi
• detritivores - animals that consume dead organic
matter
• only decomposers can break down complex
organic material releasing nutrients to soil - other
organisms can do limited breakdown, but not
enough to efficiently recycle nutrients
Resources for decomposers
and detritivores
• not just dead bodies of plants and animals, but also shed
dead body parts such as skin cells (food for mites on
humans), feathers, horns, leaves, twigs
• loss of cells from root caps creates rhizosphere which is
resource rich place for soil bacteria
• plant tissues are leaky and release soluble sugars and
nitrogen compounds on leaf surface creating rich
environment for bacteria and fungi on leaves called
phyllosphere
Rhizosphere
Rhizosphere
Bacterial Cells in White, Green, Red
Phyllosphere
Phyllosphere
Phyllosphere – Bacteria from
Leaf Impressions on Plate
Donor Control
• Decomposers and detritivores live in world where
resource supply is donor controlled - the donor
controls density (population size) of the recipient,
but the reverse does not happen - there is no direct
feedback between consumer population and
resource
• In contrast, plants and predators do exert a direct
effect on their resources because they reduce
amount of resources (population size of the prey)
in the environment
Basic Energy Flow
Important Terms for Decomposition Cycle
• Immobilization - inorganic nutrient element
is incorporated into organic form, usually
through the growth of green plants - thus
not available to other plants
• Mineralization - conversion of elements
from organic to inorganic form by
decomposition
Decomposition of Leaves
Decomposers
And
Detritivores
Detritivore Microfauna
Nematodes
Rotifers
Detritivore Mesofauna
Mites
Springtails
Macro-fauna - African dung beetle
Otzi the Iceman
African white-backed vulture
African vultures – Masai Mara
Burying
Beetles
Earthworms
Earthworm casts recycle organic matter in soil
Nightcrawlers are new to North America
Composting
Compost Pile Food Web
Soil Food Web Microbes