Environmental Engineering Reference
In-Depth Information
Figure 8.1.
Food web diagram illustrating how biodiversity can provide an important
ecosystem service, in this case, cost-effective, ecologically compatible forest regeneration.
Clear-cut harvesting of boreal forest often favors regeneration of aspen (plant on left).
This is because aspen competes with spruce (plant on right), as depicted by the solid
arrows between the plants, but aspen is the superior competitor, as depicted by arrow
thickness. Mitigating this using traditional forestry practices involves costly heavy
machinery that makes site conditions less favorable for aspen growth followed by plant-
ing nursery-grown spruce seedlings. An alternative, less costly approach is to recognize
that herbivores such as moose prefer to eat aspen, depicted by the consumer-resource
(+/-) arrows between moose and aspen. In this case, moose indirectly benefit spruce,
depicted by dotted arrow, by suppressing aspen growth and allowing the release of nat-
urally growing spruce seedlings. This represents an example in which enlisting species
diversity in several trophic levels of an ecosystem to cause a keystone predation effect
can be an effective management tool.
