Ectomycorrhizal fungal biomass in roots and uptake of P from apatite by Pinus sylvestris seedlings growing in forest soil with and without wood ash amendment

Abstract

Forest soil from an experimental Norway spruce forest with four levels of wood ash addition (0, 1, 3 and 6 tonnes ha(-1)) was used to inoculate pine (Pinus sylvestris) seedlings with indigenous ectomycorrhizal (EM) fungi. Uptake of 32P and 86Rb in a root bioassay was used to estimate the demand for P and K by seedlings grown in the different soils. Utilisation of P from apatite was tested in a laboratory system where uptake by the ectomycorrhizal mycelium was separated from uptake by roots. The demand for P and K in the seedlings was similar regardless of the ash treatment. Variation in EM levels, estimated as fungal biomass (ergosterol) in roots, was large in the different soils, but not related to ash addition. Uptake of P from apatite was, on average, 23% of total seedling P and was not related to EM levels. It was concluded that the improved P uptake from apatite by EM fungi found in earlier studies is probably not a general phenomenon among EM fungi. The small effect of ash addition on EM levels and P uptake suggests that addition of granulated wood ash is a forest management treatment that will have only minor influence on ectomycorrhizal symbiosis.

The phosphorus status of northern hardwoods differs by species but is unaffected by nitrogen fertilization

“…In particular, trees with endomycorrhizal associations, like sugar maple, may have limited ability to access mineral P compared to the other species in this study, all of which are ectomycorrhizal. If some ectomycorrhizae provide trees with P directly from mineral sources (Wallander et al 2005) or organic sources (Dighton 1983), then available soil P may underestimate the tree's actual P supply. Similarly phosphatase activity would overestimate actual demand.…”

“…Tree species are thought to influence P cycling through interspecific differences in root distribution, indirect pH effects on P solubility, phosphatase activity, and production of organic acids that chelate P-binding metals (e.g., aluminum) (reviewed by . Tree species may also influence P cycling through ecto-(but not endo-) mycorrhizae that directly access mineral forms of P like apatite, though this is poorly understood (Blum et al 2002;Wallander et al 2005). Effects of tree species on P cycling have been observed in both tropical and temperate forests dominated by dinitrogen fixers (Zou et al 1995), in pine stands of the southeastern US (Polyakova and Billor 2007) and subtropical evergreen forests (Kamei et al 2009).…”

Phosphorus uptake and availability and short-term seedling growth in three Ontario soils amended with ash and biochar

“…An alternative explanation is that responses were affected by initial nutrient concentrations or other aspects of soil chemistry in the three soils. For example, N-limited forest sites typically do not exhibit growth responses or increased foliar nutrient concentrations after ash addition because ash does not add N back to the soil (Jacobson et al 2004;Wallander et al 2005). However, the sandy-loam soil, in particular, is known to have excess N and to be P limited Thomas 2006, 2008), so it should thus be a strong candidate for positive responses to ash amendments, though that was not seen in this study.…”

“…Biochar and ash effects on P availability can also vary widely depending on the soil texture and the dominant plant species. Acidic soils typically have stronger responses to biochar than alkaline soils (Cui et al 2011;Biederman and Harpole 2013;Xu et al 2014) and ash amendment effects on P availability are strongest in P-limited soils (Wallander et al 2005). However, despite this variability, few studies have systematically compared effects in different soils planted with different species under the same amendment and growth conditions.…”

Simulating ectomycorrhiza in boreal forests: implementing ectomycorrhizal fungi model MYCOFON in CoupModel (v5)

“…5.1, Table A1b). The C supply is defined by a constant fraction of the root C gain and is leveled off by the function f (c fungiavail ) as soon as a defined value of soil-available total N is exceeded, i.e., in the model the potential ECM growth declines with rising soil N. This scaling function is based on observations from field and laboratory experiments, which showed that the ECM biomass of mycelia and mantle can be as much as 30-50 % of fine-root biomass, and the majority of ECM decrease in abundance and functioning when the soil N levels are high (e.g., Wallander, 2005;Wallenda and Kottke, 1989;Högberg et al, 2010). The actual ECM growth is limited by the maximum growth and calculated by a predefined fraction of assimilated root C, assuming that the production of an optimum mycorrhization degree requires a certain amount of ECM biomass (Eq.…”