TREE AUTOECOLOGY

TOPIC CHAPTER IN KIMMINS

Solar radiation 7

Temperature 8

Wind 9

Water 10

Nutrients (and soils) 5 and 11

Fire 12

THREE OBJECTIVES FOR EACH TOPIC:

1. To understand the variation in the availability of each resource. How does availability vary spatially and temporally?

2. To know the general significance of the resource to the plant. How does variation in the quantity or intensity of the resource affect plant growth and survival?

3. How are plants adapted to different levels of the resource? How are plants adapted to obtain enough of a particular resource or to tolerate excessive amounts or intensities of a resource?

--THE CONCEPT OF ENVIRONMENT--

1. Approaches to the analysis of a plant's environment.

a. The holocoenotic approach and the concept of "site"

b. The factorial approach

2. Concept of critical factors

Whenever an environmental factor (resource) approaches a threshold for the growth, survival, and/or reproduction of a plant, its relative effect on the plant is "critical."

PLANT RESOURCES AND THE USE OF THE CONCEPT OF THE OPERATIONAL ENVIRONMENT

General resources required by plants are: light, heat, carbon dioxide, oxygen,

water, and mineral nutrients

The analysis of the influence of variations in these resources is best achieved by applying a factorial approach such as the concept of the operational environment.

The Operational Environment

Definition: The operational environment of a plant includes the environmental factors which directly impinge upon a plant. This concept allows us to factor or breakdown much broader concepts such as Aclimate@ or Asoil@ into numerous factors which may be critical to the growth, survival or reproduction of a plant. Although most of these factors are interdependent (e.g. solar radiation affects air temperature), they may be measured separately.

In the field, the factors of the operational environment serve as a checklist to remind you which aspects of the plant=s environment may be critically affecting that plant at a particular site.

I. Abiotic factors (i.e. physical-chemical factors)

A. Mainly climatic factors

1. Solar radiation

2. Air temperature

3. Atmospheric gases and particulate matter

4. Atmospheric humidity

5. Mechanical force (for example, wind)*

B. Mainly edaphic factors (i.e. soil-related)

1. Soil moisture available to plant roots

2. Soil temperature

3. Soil chemicals in liquid and solid phases

4. Soil gases

II. Biotic factors

1. Symbionts

2. Pathogens

3. Herbivores

4. Direct human action

How can the concept of the operational environment (a factorial approach) be reconciled with the holocoenotic concept of the environment?

Should competition or fire be included as a factor in the operational environment?

Definition of competition in the context of the operational environment:

Competition is the modification of one plant's operational environment by a second plant so that the operational environment becomes less favorable to the growth, survival and/or reproduction of a second plant. This definition stresses the mechanisms by which competition occurs.