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In search of ecological advantages : Mycorrhizal facilitation of big huckleberry Vaccinium membranaceum (Doug.) Public Deposited

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  • Temperate evergreen forests of the Pacific Northwest support big huckleberries (Vaccinium membranaceum) despite their nutrient impoverished soils. Acquisition of nitrogen and phosphorous are the major nutrients limiting V. membranaceum. The plant’s access to these resources is linked to their mycorrhizal symbiosis. To learn more about the symbionts of eriaceous plants in temperate evergreen forests, this study focuses on new methods to quantify mycorrhizal facilitation, and a search for correlations between level of infection and soil qualities. Quantifying enzyme activity differentiates active hyphae from inactive or senescing hyphae, in contrast to conventional microscopy techniques. Because ericoid mycorrhizae are the primary contributors of phosphorus to V. membranaceum, phosphatase assays were used as a rapid method to quantify mycorrhizal infection. These tests suggest that phosphatase assays may not be as satisfactory as other enzyme assays to indicate mycorrhizal facilitation because they do not correlate well with physical infection values found by microscopy. This observation could be the result of: 1.) variation within seasonal activity of the ericoid symbiont, 2.) unknown phosphatase contributions from dark septate endophytes, 3.) a miscalculation of enzyme standard curves, or 4.) a combination of the three factors. The infection of roots by dark septate endophytes was correlated with both the total available phophorus and organic phosphorus. An increase in root size was positively correlated with increased organic matter and total nitrogen (also interpreted as an absence of smaller hair-roots). Implications of these results regarding variation in nutrient availability throughout a year and over time (decades) are discussed.
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