Fine root attributes of endomycorrhizal woody plants and the application of endomycorrhizae to urban horticulture

Woody plants are a vital component of natural and human-dominated environments. Their fine roots play a key role in soil resource acquisition as well as carbon and nutrient cycling. The endomycorrhiza is a highly-evolved symbiosis between specialized soil fungi and the fine roots of woody plants. The effects of mycorrhization on fine root attributes may have significant implications in both natural and managed ecosystems.; Minirhizotrons were used to assess the fine root attributes of endomycorrhizal woody plants. The experiment was conducted at the Musser Fruit Research Center near Clemson, SC using Freeman maple (Acer x freemanii ), trident maple (Acer buergerianum), sweetbay magnolia (Magnolia virginiana), and star magnolia (Magnolia stellata). Clear butyrate minirhizotrons were installed beneath each tree at transplant in May 2002. An endomycorrhizal inoculant was applied to half of the plants and roots were videotaped at 2- to 4-week intervals during the following year.; Inoculation enhanced mycorrhizal colonization in all species (except star magnolia), but had no effect on above-ground growth or foliar nutrition. Inoculation generally decreased fine root production and mortality during the year following transplant. In addition, inoculated sweetbay magnolias experienced significantly less root branching than controls. Median root lifespan of non-inoculated controls ranged from 230 to 315 days across the four species. Enhanced mycorrhization had species-specific effects on fine root longevity and the timing of cortex pigmentation.; Soil disturbance may negatively affect mycorrhizal abundance and infectivity. Soil inoculum potential and mycorrhization of red maple (Acer rubrum ) were assessed in forested and developed landscapes near Clemson, SC in June 2004. Mycorrhizal colonization was significantly greater in forest red maples than in landscape red maples (22% vs. 3%); conversely, the inoculum potential of landscape soils was more than twice that of forest soils. Soil inoculum potential and mycorrhizal colonization were not significantly correlated. Soil pH and extractable phosphorus content were substantially lower in forest soils. Soil pH was negatively correlated with mycorrhizal colonization across both sites, suggesting that red maples may exert control on colonization in response to acidity-related phosphorus availability.; Mycorrhizal inoculants are available commercially and may improve plant growth and survival in urban horticultural applications. Commercial mycorrhizal inoculants were evaluated in a series of greenhouse experiments in Clemson, SC using corn (Zea mays), sorghum (Sorghum bicolor ), sweetbay magnolia, and trident maple. In corn and sorghum, mean mycorrhizal colonization associated with the commercial inoculants ranged from 0 to 45%. In most instances, product-related colonization did not exceed 5%. In contrast, a lab-cultured inoculant of similar composition yielded mean colonization of 38 to 61%. Despite the near absence of colonization, product-inoculated plants experienced substantial growth enhancements, suggesting the presence of nonmycorrhizal growth promoters in the commercial products. In sweetbay magnolia and trident maple, both control and inoculated plants were mycorrhizal, and application of commercial inoculants did not improve colonization or plant growth.