Ecosystems and their place in the study of Ecology
Arthur Tansley: defined the Ecosystem concept and
term, founded the British Ecological Society, founded the
Journal of Ecology, first Chairman of the British Nature
Conservncy (Forbearer of Natural England).
Ecosystem –“the more fundamental conception is, as it
seems to me, the whole system (in the sense of physics),
including not only the organism-complex, but also the
whole complex of physical factors forming what we call
the environment of the biomethe habitat factors in the
widest sense. Though, the organisms may claim our
primary interest, when we are trying to think
fundamentally, we cannot separate them from their
special environment with which they form one physical
system.”
Eugene Odum: wrote the first ecology textbook (Father
of Modern Ecology) & linked humans to ecosystems.
Ecosystem –”Any unit that includes all of the organisms(ie:
the "community") in a given area interacting with the
physical environment so that a flow of energy leads to
clearly defined trophic structure, biotic diversity, and
material cycles (ie: exchange of materials between living
and nonliving parts) within the system is an ecosystem.”
Ecosystem components: Biological communities
(Primary producers, decomposers & detritivores,
herbivores, carnivores, parasites) linked to pools of dead
, organic matter, physiochemical environment. Emphasis on
function not species.
Core Ecosystem research areas: fluxes,
transformations and interactions of energy and matter
within an ecosystem, energy budgets and factors that
control energy transfer, carrying capacity (management
and harvest) & restoration.
Ecosystem productivity
Energy flow in ecosystems: an open system in which
energy is captured and used within the ecosystem and
ultimately lost to heat. Productivity is the rate of energy
capture and conversion to chemical bonds.
Biomass = biological material derived from living or
decomposing organisms (not just plant-based material).
Biomass is composed of carbon-based molecules
containing hydrogen, oxygen, often nitrogen and small
quantities of alkali, alkaline earth and heavy metals
(metals are small in relative quantity but critical in many
functional molecules e.g. magnesium in chlorophyll).
Primary productivity = the rate at which solar/ chemical
energy is captured and converted to chemical bonds by
photosynthesis or chemosynthesis. Primary productivity is
the available energy in an ecosystem. It is not necessarily
correlated with the standing crop (amount of biomass
present at a particular time). There are 2 types of primary
productivity:
Gross Primary Productivity (GPP) = the rate at which
energy is captured and assimilated by producers in an
area (e.g. Joules per square meter). This includes the use