deletions | additions       diff --git a/From_lab_to_field_Although__.md b/From_lab_to_field_Although__.md  index 50675e0..5d6fed7 100644  --- a/From_lab_to_field_Although__.md  +++ b/From_lab_to_field_Although__.md 
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Tunnels, as described in \citet{Jongmans_1997} are the only quantifiable fungal markers of weathering that remain visible over geological time.  Unfortunately, fungal tunneling either reflects only a small portion of the total effect of fungi on the weathering process, or the fungal impact is negligible, as tunneling contributes less than 0.5% tot total mineral weathering \citep{Smits_2005}.  In a recent paper \citet{Koele_2014} showed that mineral tunneling is not exclusively found under ectomycorrhizal vegetation, but also in forest soils, never exposed to ectomycorrhizal vegetation.   This suggests that tunnels can be formed by other means (e.g. arbuscular mycorrhizal or saptrophic fungi). Work by \citet[\citeyear{Quirk_2014}]{Quirk_2012} Quirk and others  indeed show that also arbuscular mycorrhizal fungi create weathering trenches on mineral surfaces. surfaces \citep{Quirk_2012, Quirk_2014} .  ##Isotope tracers 
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Applied to plant tissues, it could potentially trace plant nutrients back to their primary source.   It has been primarily used to study the apatite weathering.  Apatite is a calcium-phosphate mineral, and as P has no stable isotopes, the uptake dynamics can only be studied via the Ca ion (or potentially the ¹⁸O/¹⁶O in the phosphate group) .  As In most rocks and soils  apatite isgenerally only a minor mineral in  the soil mineral matrix, its sole primary P source. But Ca Its  contribution to the soil solution Ca pool is minor compared to other minerals. If the Ca isotope ratio in the plant is more similar to the signature in apatite than in the soil solution, it indicates that the plant takes up Ca directly from the apatite crystal.   As the apatite crystals are below the root scale, it indicates a selective uptake via mycorrhizal hyphae colonizing apatite grains.   In an influential paper \citet{Blum_2002} applied this technique, but as in their study area, the different mineral sources did have similar Ca isotope ratios, they used the ratio between Ca and Sr instead.