ANIMAL INFLUENCES IN FOREST ECOLOGY

Some important roles of animals in forest ecology:

role of soil animals in decomposition

pollination by animals

seed dispersal by animal (endo- and epi-zoochores)

herbivory (the focus of the lecture)

HERBIVORY (including parasitism and seed predation)

Types of consumers of plants:

1. saprophytic microbes

2. parasitic microbes or plants

3. insect herbivores

4. large animal herbivores

Effects of large herbivore browsing on woody plants:

1. removal of photosynthetic plant parts

2. damage to growing points (alteration of growth form)

3. damage to cambium (deer, porcupine, etc.)

4. spread of pathogenic fungi, etc.

5. trampling of seedlings

6. indirect effects (changes in soil chemical and physical properties, changes in microenvironmental conditions, changes in competitive hierarchies).

ADAPTATIONS TO PREVENT OR RECOVER FROM HERBIVORE DAMAGE

1. Growth form and position of growing points

basal meristems of grasses (graminoids vs. forbs)

decurrent (vs. excurrent) growth form of some trees and shrubs

divaricating habit of some shrubs and trees

2. Texture and composition of plant surface

thorns, spines, prickles, sharp needle leaves

dimorphic leaf forms of juveniles vs. adults

3. Chemical properties of secondary compounds

oleoresins (e.g. pitching out of pine beetles)

tannins

4. Poor nutrient quality of foliage

5. Mutualistic interactions (e.g. protection of Acacia by ants)

6. Periodicity of seed crops

mast seeding (e.g. Fagus, bamboos)