The effects of soil type, fertilization, and mycorrhizal inoculation on paper birch (Betula papyrifera) in a simulated urban setting

This poster was constructed for the OARDC graduate student poster competition in April, 2006 by Nathan M. KleczewskiUrban trees are routinely planted in soils that are not conducive to their overall health. The application of mineral fertilizers to urban soils improves tree growth rates; however, fertilization may decrease associations with ectomycorrhizal fungi (EMF). Commercial products containing EMF are marketed as an alternative to fertilization, suggesting that native EMF are not able to establish themselves in urban soils. These products are assumed to improve the mycorrhizal status of the trees, but this assumption is often based on circumstantial evidence at best and flawed experiments in many cases. The long term effects of these products on native EMF communities and urban tree health remain unknown. We are exploring the effects of soil type, fertility, and inoculation with a commercial EMF product on native EMF communities, growth, and stress tolerance in Betula papyrifera in a simulated urban setting. Preliminary results from this multi-year study indicate that native MF may rapidly establish in urban soils and reach levels comparable to topsoil treatments. Inoculation of trees with commercial mycorrhizal inoculant resulted in increased root : shoot ratios; however, no EMF from this product were detected in the field. Data obtained from greenhouse bioassays on paper birch seedlings support field data. Information gained in subsequent years will clarify the roles of EMF on the health and stress tolerance of trees in the urban forest.Ohio Nursery and Landscape Association in addition to other funds appropriated to the Ohio Agriculture and Research Development Center (OARDC

Responses of paper birch (Betula papyrifera) to fertilization and amendment with a commercial mycorrhizal inoculant in two contrasting soil types.

The poor soil structure and fertility characteristic of urban soils are known to decrease the growth and survival rates of urban trees. Trees planted in such soils are more prone to damage by drought, flooding, and other stresses. It is believed that amending urban soils with ectomycorrhizal fungi (EMF), i.e. fungi that form one of several mutualistic associations with tree roots, improves tree growth and survival and decreases the need for soil fertilization and management. We tested a commercial mycorrhizal inoculant in nutrient and structure deficient subsoil, with and without fertilization, for effects on physiological traits and drought tolerance of paper birch (Betula papyrifera). Results were contrasted to those from equivalent treatments imposed on trees growing in nutrient and structure rich field topsoil. Measurements of photosynthesis, growth rates, total phenolics, and EMF abundance and diversity were made. Data obtained from small experiments conducted under laboratory light banks showed that the mycorrhizal inoculant promoted growth of paper birch seedlings while improving EMF colonization rates. In contrast, a larger greenhouse study showed no effects of the mycorrhizal inoculant on growth, productivity, or drought tolerance of seedlings. Although ectomycorrhizae were present on greenhouse seedlings, fungi present in the mycorrhizal inoculant did not form them; rather, they apparently were formed with fungi naturally present in the soil. In conclusion, the preponderance of the data suggests that treatment of trees with commercial mycorrhizal inoculants may not be as beneficial to urban trees growing in poor soil conditions as improving soil composition and structure