Plant Adaptive Tactics

External Factors  Stress – phenomena which limit photosynthetic production and growth.  Disturbance – factors causing partial or total destruction of plant

Four permutations  High stress - high disturbance  Low stress - low disturbance  High stress - low disturbance  Low stress - high disturbance

Low stress - low disturbance  Competitors – Ability: function of area, activity and distribution in space and time of the plant surfaces through which resources are absorbed.  General Features of Competitors: – Phenology – Plasticity

Features of a competitor  - Storage organs  - Height  - Lateral spread  - Phenology  - Growth rate  - Response to stress  - Response to damage

High stress - Low disturbance  Stress tolerators  Low plasticity – Growth generally occurs intermittently.  Most important responses are physiological, not morphogenetic.  Symbiosis - Ectotrophic mycorrhizas  Slow growth  Resistance to predation

High disturbance - Low stress  Ruderals  Tendency toward annual or short lived perennial habit  Capacity for high rates of dry matter production  Flowers at early stage of development - seed ripening may be extremely rapid  Often death follows seed production

Relationship to r- and K-selected types  r-selected: – generally considered to have short life expectancy and large reproductive effort.  K-selected: – long life-expectancy and proportion of energy and resources devoted to reproduction is small. Heavy investment in “care of young.”

Spectrum

Triangular ordination

Examples Annual herbsPeren. herbs/ferns Trees & Shrubs Biennial herbs LichensBryophytes AnnualsbiennialsPerennial herbs & ferns Trees & shrubslichensbryophytes

Cacti

Birch and Aspen

Forest climax

Bog plants

Tundra truck tracks

Agave