Final Report - Center for Invasive Plant Management

observed in the IREEG protein fraction. Interestingly, the trade-offexperienced bv plant rootsystems between the production of fine roots and external ltyphal associations (Miller et al.1995) was not observed, For example. an increase in external AM hyphal length did not occurwhen fine root length decreased. Instead" both parameters seemed to decline together. Althoughmycorrhizal infections are generally considered beneficial, mycorhizal fungi can represent acarbon drain on plants (Allen 1991). ln tbct. it has been fcrund that some species r"rf arbuscularmycorrhizao can astilally reduce plant tolerance to drought (Allen and Boosalis 1983). By latesummer during the sampling period, both plant and fungus could have suffered from a carbondeficit due to the severe drought conditions experienced during the sampling period.10Correlations between glomalin tiactions and root parameters were only obsen'ed betweentlre IREEG fraction and all root length paran"teters. As previously mentioned, it is unclear horvthese operationally defined glomalin pools differ lrom each other. It has been suggested that theEEG and IREEG pools are more readily available in the soils, either by being the most recentlyl5deposited fractions (Wright and Upadhyahya 1998) or by being the rnost recently deconipasedfractions (Steinberg and Rillig 2003). It has been suggested that degradation of glomalin in thesoil also decreases its adsorption to soil particles (Steinberg and Rillig ?003).Plants produce more roots during certain times in a growing season due to environmental20 factors. During this active root production, plant roots release exudates that are a labile source ofcarbon tbr the soil microbial community, enhancing the environment fbr decomposers (saprobesand bacteria). Priha et al. (1998/1999) lound that two species of trees had a stimulative effect onsoil microbes. possibly due to the tree species having more roots and releasing more root14