The establishment, drought tolerance, and weed suppression potential of multispecies sod
Stark, Jennifer Grace.
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Re-seeding is a frequently used technique to revegetate disturbed areas, but often leaves bare ground prone to weed invasion. Mixtures of drought tolerant or native species in sod could be used as an alternative to seed to provide rapid establishment of desirable plant communities that may potentially reduce weed emergence, survival, and productivity. Additionally, the reinforcement material required to aid transport of multispecies sod could further contribute to weed suppression and sod establishment. The objective of this study was to evaluate the weed suppression and establishment potential of multispecies sod. Three experiments were each subject to a water regime ranging from 2.54 cm of water/week to natural precipitation, and repeated over two/three years. In the first two experiments (A and B) Brassica napus (canola) was used as a surrogate weed species and sown either below the multispecies sod to represent weed seed bank, or above the multispecies sod to represent weed seed rain. In experiment A, B. napus was sown at six densities; while in experiment B reinforcement materials (nylon netting control, coconut-straw, jute, excelsior) were added below the sod and B. napus was sown at one density. B. napus suppression by multispecies sod, with or without reinforcement material, was evaluated by recording seedling emergence, survival and above-ground biomass. Multispecies sod, especially combined with reinforcement material, suppressed a large proportion of seedling emergence. The seedlings that did establish produced less vegetative and seed biomass as water decreased. In the second season of both experiments no seedlings survived to maturity. The establishment success of the multispecies sod was evaluated through repeated measures of percent sod cover over two/three years. The results suggested that the multispecies sod was able to establish and persist under natural precipitation. The third experiment evaluated the ability of multispecies sod to suppress Cirsium arvense (Canada thistle) vegetative propagules in two different habitat types, bare ground or multispecies sod, under high and low water treatments. More C. arvense shoots emerged in the bare ground, suggesting that multispecies sod could act as a buffer zone and reduce the vegetative spread of perennial weeds if used as a revegetation strategy.