Field use of ³²P to measure phosphate uptake by birch mycorrhizas

Abstract

SUMMARYwas used to determine phosphorus uptake by diflFerent mycorrhizas of birch in the field. Time of year and location of the application of ^^P were the dominant variables influencing uptake into the canopy. There was evidence of differential uptake by the three mycorrhizal types selected. Where Hebeloma mycorrhizas were more frequent, a significantly greater rate of phosphorus uptake per unit leaf weight occurred than where Laccaria or Lactarius were more frequent. The method shows potential for field evaluation of efficiency of nutrient uptake by mycorrhizas, although a number of factors need to be taken into account in determining uptake. In locating areas for ^^P injection, it was found that the distribution of mycorrhizal types on roots did not always reflect the distribution of the corresponding fruitbodies.

Vegetation and Soil Environment Influence the Spatial Distribution of Root-Associated Fungi in a Mature Beech-Maple Forest

“…One of the most abundant genera in this study, Tomentella, did not appear to be positively or negatively correlated with P o . Although labile P i was rather high in our study and labile P o is available to plants only after mineralization to P i (6), different ECM species may have different abilities to capture P i (15,21) and many ECM fungi also vary in their abilities to produce extracellular enzymes that liberate nutrients, such as N and P, from organic matter and detritus (7,8,16,60). Differences in FIG.…”

Nutrient Limitation in Soils Exhibiting Differing Nitrogen Availabilities: What Lies Beyond Nitrogen Saturation?

“…If, as appears to be the case at our study sites, a forested ecosystem shifts from N to P limitation, then the initial response might include changes in resource allocation by plants that preferentially improve the acquisition, or retention, of P. These changes could include an increased activity of rootassociated phosphatase (Vance et al 2003), a greater production of organic acids in root exudates (Marshner 1995), a shift in the type (or diversity) of mycorrhizal fungi that colonize plant roots in a way that increases P acquisition (Dighton et al 1990, Dighton and Coleman 1992, Baxter and Dighton 2001, and a greater efficiency of P resorption from leaves prior to senescence (McGroddy et al 2004). If, as appears to be the case at our study sites, a forested ecosystem shifts from N to P limitation, then the initial response might include changes in resource allocation by plants that preferentially improve the acquisition, or retention, of P. These changes could include an increased activity of rootassociated phosphatase (Vance et al 2003), a greater production of organic acids in root exudates (Marshner 1995), a shift in the type (or diversity) of mycorrhizal fungi that colonize plant roots in a way that increases P acquisition (Dighton et al 1990, Dighton and Coleman 1992, Baxter and Dighton 2001, and a greater efficiency of P resorption from leaves prior to senescence (McGroddy et al 2004).…”

Response of Mycorrhizal Diversity to Current Climatic Changes

“…Alfisols that have been grasslands and then converted to intensive agriculture continue to be occupied by AM associations [327]. Forested Alfisols, however, have mostly occupancy by ECM [328][329][330][331][332].…”