Seasonal Fungal Biomass Dynamics In An Interior Alaskan Paper Birch (Betula Papyrifera Marsh) And Quaking Aspen (Populus Tremuloides Michx.) Stand And Effects Of Long-Term Fertilization (Fungi, Mycology, Mushrooms, Ecosystem(S))

Abstract

Standing crop fungal biomass was measured at bi-weekly intervals for two successive field seasons in contiguous, 50 year old stands of quaking aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh) and in contiguous stands of aspen and birch undergoing long-term fertilization by yearly application of inorganic nitrogen, phosphorus and potassium fertilizers. Soil temperature and moisture were monitored throughout the study. Principal goals were: (1) to delineate seasonal fluctuations in fungal biomass in the forest floor and mineral soils of aspen and birch vegetation sites considered representative of upland, interior Alaskan hardwood taiga; (2) to determine if biomass fluctuations were correlated with fluctuations in soil microclimate; (3) to determine if differences in fungal biomass were correlated with dominant overstory vegetation; i.e. differences in primary or secondary site substrate (resource) quality; (4) to determine if long-term (nine years) application of inorganic fertilizers altered overall standing crop fungal biomass in the two vegetation types studied; and (5) to determine if soil bulk density or microclimate were influenced by vegetation type or fertilization. Results show that seasonal biomass for both control and fertilized sites was closely correlated with soil moisture and exhibited little or negative correlation with soil temperature. Unamended aspen soils supported significantly greater fungal biomass than birch soils due to increased soil moisture, a more favorable chemical environment and production of organic matter more conducive to growth of soil fungi. Fertilization significantly decreased fungal biomass in aspen soils indicating the long-term treatment with inorganic fertilizers could be detrimental to mineral cycling in this forest type. Fertilization significantly increased fungal biomass in birch soils due to increased soil organic matter content and increased soil moisture. Hyphae of basidiomycetes was significantly decreased by fertilization in both vegetation types suggesting that basidiomycetes involved in saprotrophic decomposition and/or mycorrhizal associations were adversely affected by fertilization. The effects of vegetation type and fertilization on soil temperature, moisture and bulk density are discussed.