Plant Ecology 101 in 5 minutes
Bruce Barbour, RCE Environmental Program Leader
Time
Other species don’t necessarily operate on the same time scale as we do. Their survival
mechanisms often involve time intervals that make them hard for us to perceive.
Catastrophe
Catastrophes are infrequent but of great significance to the survival of species. The
prosperity of a species may depend upon catastrophic events that control it’s competitors or
provide food. Ie. fire, flood, epizootic. etc.
Succession and Climax
Classic plant ecology describes an orderly progression of species that colonize and then
yield to others over time following disturbance or catastrophe. This chain of succession
culminates in a stable, efficient, and usually diverse community of plants, animals and microorganisms called the climax ecosystem. This view of ecology is pretty much abandoned now.
Energy Flow
Most of the interactions in an ecosystem can be understood if examined from the
standpoint of energy transfers, losses, accumulation and leakiness or efficiency. All the cycles of
predator and prey, growth and decay, balance and imbalance are largely understandable as the
movement of energy in the system. Put another way energy, in the form of carbon, flows through
ecosystems from producers (plants, algae) to consumers (predators, herbivores) to decomposers;
there is inefficiency at each transfer – much of the energy goes off as heat, and only about 10%
of the energy at one level turns into biomass at the next.
Nutrient Flow
What can’t be explained by energy flow probably can be by nutrients. Important point is
that energy flows whereas nutrients cycle .
Niche
The set of parameters or environmental conditions a species need to live or the conditions
outside of which it cannot survive. Typically temperature, water, food, reproductive needs, etc.
Specialists and Generalists
Generalists is the term given to species whose evolution has adapted them to survive
under changing circumstances. They are usually adaptable with respect to energy and nutrient
needs. They are the colonizers who are the first to move in after catastrophe occurs. They are the
survivors and wanderers of the world. The price of their adaptability is that, as a group in a
system, they are not very efficient at using the scarce resources of energy and nutrients. Given a
stable environment generalists will evolve into specialists.
Specialists are the residents of stable ecosystems. Their specialization is their unique
adaptation to a narrow niche. It allows them to extract energy and nutrients not available to more
generalized species and thus out compete them. As a group communities of specialists constitute
very efficient and stable ecosystems. Often inter species dependence is part of specialization and
this creates the complex set of relationships that characterizes a mature, diverse and efficient
ecosystem.