Mechanisms of Interference over Tree Establishment, Survival, and Growth.
This section describes different ways that a dense understory canopy can suppress regeneration. Because most studies fail to distinguish among these mechanisms, Muller (1969) proposed the term interference to describe the suppression of one species or layer on another species. In the following sections, the literature is briefly reviewed to evaluate the evidence for six different mechanisms of interference between the understory layer and co-occurring tree species. These mechanisms include: (1) resource competition, (2) allelopathy, (3) physically impeding seedling germination and growth, (4) through modifications of interspecific interactions (see figure at right). We suggest that the most efficient and cost-effective remediation of the deleterious effects of these recalcitrant understory layers will require a greater understanding of how these layers alter patterns of forest regeneration and succession.
- Resource Competition : In forested systems, perhaps the most prominent interference mechanism exerted by a recalcitrant understory layer would be direct competition for above- and below-ground resources.
- Allelopathy : This section discusses the potential effects of the phenomenon called allelopathy: i.e., the inhibition of growth or survivorship of one plant species by chemicals produced by another species.
- Seed Predation : This section discusses how a dense understory layer can increase the activity of small mammals, thereby increasing the rate and impact of seed and seedling predation.
- Litter Accumulation : A thick litter layer typically reduces plant species diversity and density through a wide variety of direct and indirect mechanisms.
- Mechanical Interference : A dense understory layer can reduce tree seedling regeneration via non-competitive, physical interference.
- The Relationship Between Mechanisms of Interference and Phenology : This section discusses how the intensity and duration of any particular interference mechanism can vary temporally as a result of the species' life history, whether evergreen, deciduous, or monocarpic.
Encyclopedia ID: p3102
