deletions | additions       diff --git a/Fungal_weathering_in_the_lab__.md b/Fungal_weathering_in_the_lab__.md  index 222267a..c339ed6 100644  --- a/Fungal_weathering_in_the_lab__.md  +++ b/Fungal_weathering_in_the_lab__.md 
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In addition, wood decomposing fungi produce large amounts of oxalic acids when degrading wood \citep{Dutton_1996}, which may have secondary effects on phosphorous release from the soil \citep{Fransson_2004}.    It is not clear if organic acid release and acidification is a primary mechanism to release nutrients from soil minerals, or a secondary effect related to the way microorganisms are growing in the soil.  Proton Protons  are exuded in response to uptake of positively charged ions regardless of if minerals are present or not, and exudation of organic acids can occur in response to many different factors such as pathogenesis and detoxification of heavy metals \cite{Dutton_1996}. Furthermore, concentrations of organic acids in soil solution \citep{van_Hees_2000} seldom reach levels that have significant effects on mineral dissolution \citep{chadwick_changing_1999}.  On the other hand, fungal hyphae attach to surfaces to be able to grow and proliferate through the soil, which may affect the surface of the minerals both physically and chemically \citep{McMaster_2008}.  
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In some laboratory experiments with axenic cultures of microorganism it has been found that attachment to biotite surfaces yielded stronger dissolution compared to when they were separated by a membrane. This demonstrate that not only the chemicals produced but also the physical attachment is important for mineral dissolution \citep{Ahmed_2015}.  However, in other experiments, no additional effect on weathering was found when EMF hyphae were attached to minerals in axenic growth in solution cultures \cite{Balogh_Brunstad_2008}.   One problem with axenic solution experiments is that no sink (the plant) is available for the released elements. Nutrient removal from the soil solution will change the saturation state of minerals containing these nutrients. This will increase the dissolution rate, although its effect is only substantial under close to saturated conditions.  In one study with axenic pine seedlings ectomycorrhizal with *P. involutus*, \citet{Bonneville_2011} found large removal of K, Mg and Fe under hyphae attached to biotite, which suggests that hyphal attachment, and a sink for element removal (the plant) is important for mineral dissolution to occur. Furthermore, it could be demonstrated that the biotite surface was strongly acidified under the hyphae, which suggests that specific chemical conditions occur under biolayers formed by the fungal mycelium.  \citet{Schmalenberger_2015} demonstrated mineral specific exudation of oxalate by *P. involutus* using labelled ¹⁴CO₂ given to the host plant.  Oxalate was exuded in response to minerals in the following sequence Gabbro > limestone, olivine and basalt > granite and quartz.