Final Report - Center for Invasive Plant Management

and root colonization (e.g., Gay et al. 1982, Anderson et al. 1984, Johnson et al. 1991, Sandersand Fitter T992, and Mullen and Schmidt 1993), studies examining the seasonality of AMFextraradical hyphae and their exuded products are sparse. Although fungal spore production androot colonization are important for elucidating fungal life histories (Hart and Reader 20QZ),neither of these characteristics directly relate to ecosystem function. Conversely, extraradicalhyphae and their products, such as glomalin. can be directly related to ecosystem processes, e.g.by virtue of their contributions to soil aggregate stability (Jastrow and Miller 1997, Wright andUpadhvahya 1998). More specifically, AMF contribute to soil aggregation through the hyphalentanglement process, assisting in soil aggregate formation (Jastrow and Miller 1997), and10through the production of extracellular polyrneric compounds on hyphal surfaces, which can sorbto inorganic materials, helping to stabilize soil aggregates (Jastrow and Miller 1997). As anexample, extraradical hyphae of AMF produce glomalin" a glycoprotein that is highly correlatedw-ith the percentage of water-stable aggregates (WSA) in soil (Wright and Upadhyahya 1998,Rillig et al. 2001)l5To our knowledge, only two studies have examined the seasonality of extraradicalhyphae in the field, and only one of these studies examined hyphae from a natural system. Kabiret al. (1997) examined the seasonal changes ofextraradical and intraradical arbuscularmycorrhizal hyphae affected by tillage and fertilization in an agricultural soil over a growing20 season (n=4). Abundance of AN{ hyphae fluctuated significantly within a growing season, withlowest hlphal densities found in the spring. Seasonal variation in mycorrhizal root colonizationfollowed corn plant development. increasing up to silking and decreasing thereafter. Miller et al(1995) examined external hyphal production and its relation to gross root morphology (specific