Competition (Ch. 10) Ken Jennings: my hero! 74 wins (2004) $2.52 million
Target-neighborhood experiment Remove around “target” shrub Target monitored (water status) Result: little intraspecific comp. both sp. great Larrea-Ambrosia comp. Danger…
Danger for removal experiments: Apparent competition Herbivore effects mimic competition Ex: Herbivore eats A and B Remove A, herbivore leaves, Interaction b/w A & B
Other points 1) Herbivory influences competition Ex, chalk grassland (England) Lab studies: grass better competitor. How forbs persist? Rabbits (“killer rabbits?”) Plant Ecology Theatre!
Other points Rabbits prefer grass (help forbs) Twist: Myxomatosis decimated rabbits 1950s—forbs declined Rare butterflies (ex, marsh fritillary) declined The marsh fritillary
Other points 2) Disturbance timing on competition species 1 numbers No disturbance time
Other points Can allow coexistence Frequent disturbances numbers species 1 species 2 time
Other points 3) Phenology can affect competition Ex, lab study Germinate same time: sp. 2 Sp. 2 germinate 2 wk earlier: sp. 1
Allelopathy Allelopathy: chemical May be Allelopathy: chemicals added to env.
Plants “leaky” Many ways rainwater leaches volatiles Root decay
Examples Ex, Salvia (sage): coastal sage scrub (CA) Leaves release cineole & camphor camphor
Examples Chemicals inhibit germination & growth annuals “Bare zones” camphor
Examples Ex, Juglans nigra (black walnut) Roots: juglone
Examples Ex, Ceratiola ericoides (beach rosemary) Sandy soils
Examples Ex, Ceratiola ericoides (beach rosemary) Releases ceratiolin
Allelopathy: Problems with proof Need to: #3 hard! Allelopathy proof difficult
Allelopathy: Problems with proof Other factors: herbivory Cages:
Weeds and allelopathy Ex, Centaurea maculosa (spotted knapweed) Invasive exotic
Weed example Ex, Centaurea maculosa (spotted knapweed) Releases catechin catechin
Ch. 10: Positive plant-plant interactions
Facilitation Facilitation: + effect ( Commensalism: Some epiphytes
Commensalism Nurse plant effect (+,0) Saguaro plant nurse……
Commensalism Nurse plant effect (+,0) Ex, Saguaro cactus (Carnegiea gigantea)
Commensalism Seedlings under Palo Verde trees Provides:
Commensalism Ex, Marsh elder (Iva frutescens: salt marsh) Juncus roemerianus shading decreases evaporation:
Commensalism Can help exotics Ex, chenopod shrubland
Mutualism (+,+) interaction: pollination, seed dispersal, N-fixation….
Mutualism Ex, root grafts connect
Mutualism Radioactive tracers Roots Danger!
Mutualism Danger: Disease
Lichens Mutualism (+,+) Lichen: fungus
Lichen Together: