In what form is moisture available?
How does substratum moisture vary?
- The soil/substratum can be saturated when water that does not seep into or run off the surface fills all inter-particle spaces.
- In contrast, soil can be completely dry, with no water available to plants or animals.
- In a temperate forest, the soil is rarely dry, but will fluctuate between saturation and lesser levels of soil moisture.
Why is substratum moisture biologically important?
- All plants and animals in the temperate forest need water for survival. Animals without a protective outer layer could lose water through evaporation from the organism's surface. Severe dehydration can affect enzyme activity within cells and body organs, and ultimately lead to death.
- Gas exchange in invertebrates requires moist surfaces (oxygen diffuses in while carbon dioxide diffuses out). However, the ability to effectively exchange gases becomes limited in saturated soils.
- Organisms in the temperate forest have adaptations (anatomical features) to reduce water loss.
How do animals respond to variation in substratum moisture?
- Direction: Invertebrates may choose and/or move to substrata with suitable moisture. Under stressful low moisture conditions their movement may be erratic or limited.
- Rate of movement: Depending on the mode of movement, surplus surface moisture may make it more difficult to move (e.g. insects) or enable more rapid movement (e.g. snails).
To learn more:
Freeman S, Harrington M, Sharp J. 2014. Biological science. 2nd Canadian ed. Toronto: Pearson.
Smith TM, Smith RL, Waters I. 2014. Elements of ecology. Canadian ed. Toronto: Pearson.
Note: Any edition of the above books or other biology and/or ecology textbooks could be useful.
Freeman S, Harrington M, Sharp J. 2014. Biological science. 2nd Canadian ed. Toronto: Pearson.
Smith TM, Smith RL, Waters I. 2014. Elements of ecology. Canadian ed. Toronto: Pearson.
Note: Any edition of the above books or other biology and/or ecology textbooks could be useful.