Do common ectomycorrhizal networks play a role in dampening competition amongst conifer species? Wallace, Cory
Niche theory predicts that the coexistence of species is the result of dissimilar demands on the resources available in their ecosystem. This is contradictory, however, to the observation that species with similar needs and even individuals of the same species often live in close proximity to one another. Common mycorrhizal networks (CMNs) have been proposed as a possible explanation of this phenomenon via their ability to acquire and transfer nutrients between plants. To test this hypothesis, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and ponderosa pine (Pinus ponderosa C. Lawson) seedlings were grown in autoclaved and non-autoclaved soil. Seeds were sown in a grid formation to keep density consistent and the plants were allowed to grow for 34 weeks. To assess resource allocation and the effects of competition, Gini coefficients were calculated for height, basal diameter, dry shoot biomass, and dry root biomass. Gini coefficients tended to be lower in non-autoclaved than autoclaved pots for three out of four variables measured for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), but differences were not statistically significant. There appears to be some evidence that CMNs affect intraspecific competition among Douglas-fir.
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