Data from: Low-molecular weight organic acid production by arbuscular and ectomycorrhizal conifers
Data files
Jul 03, 2026 version files 56.30 KB
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README.md
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root_tip_organic_acid_assay.xlsx
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soil_cation_chemical_properties.xlsx
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soil_water_acids_and_cations.xlsx
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Abstract
Temperate rainforests along the North American Pacific coast often have heavily podzolized soils with low pH and depleted base cations. As such, low-molecular weight organic acids (LMWOA) possibly play an important role in rainforest soils by enhancing the biotic weathering of minerals, but whether ectomycorrhizal (EM) fungi and arbuscular (AM) fungi differ in this trait is uncertain. We compare LMWOA concentrations in soils and directly produced from individual root tips by an EM conifer (Picea sitchensis) and AM conifer (Thuja plicata) in a six-decade long field trial. Soil water extracts were dominated by tartaric acid, particularly in the organic horizon, and were 10-fold higher on average under T. plicata. The effect of tartaric acid on cation availability was highlighted by a positive correlation with calcium in soil solution, but at a significantly lower rate of release under T. plicata. We also found podzolization attributes elevated under T. plicata, with slightly less base saturation, lower pH near the soil surface, and greater concentrations of exchangeable aluminum. A short-term laboratory assay demonstrated 50 % higher production of total LMWOA (primarily formic acid) by distal roots of T. plicata compared to EM fungal colonies. Several findings deserve further investigation, including whether these organic acids protect roots from aluminum toxicity, and the possible role of mycorrhizosphere bacteria in LMWOA production for either mycorrhizal type. When considering the ‘whole-tree’ response, we suggest T. plicata through LMWOA production would be well adapted to exploiting the widespread base-poor soils of the Pacific coast rainforest.
Included are the humus layer and mineral soil properties for exchangeable cations, CEC, pH, and low weight molecular acids between Sitka spruce and western redcedar. In addition, the organic acid assay results from a 1 hour incubation of retrieved ectomycorrhizal root tips and cedar roots. Results are focused on the extent and role of low weight molecular organic acids in temperate rainforests.
Description of the data and file structure
For the soils data (soil_cation_chemical_properties.xlsx), column one is the tree species (Cw = western redcedar, Ss = Sitka spruce), column two is the plot number, column three is the subsample, and column four is the soil substrate. The remaining columns are the associated soil data.
For the laboratory assay (root_tip_organic_acid_assay.xlsx), column one is the day of the measurements, column two is the mycorrhizal type (EM for ectomycorrhizal, AM for arbuscular), column three is the plot number, column four is the soil substrate, column five is the lab ID, column six is the fungal species name (a '.' denotes a sample where no useable molecular data was obtained), column seven is the Species Hypothesis (UNITE; NA refers to a sequences that has a < 98.5 % match to the database), and the remaining columns are the associated organic acid data.
For the organic acids and cations in soil solution (soil_water_acids_and_cations.xlsx), column one is the tree species (Cw = western redcedar, Ss = Sitka spruce), column two is the plot number, column three is the subsample, and column four is the soil substrate. The remaining columns are the associated concentrations of organic acids (tartaric and citric) and soluble cations (Ca, K and Mg).
The main data sets are the soil base cation properties and organic acids under each tree species, plus the laboratory assay of retrieved root tips for organic acid production.
Sharing/Access information
All data used in the manuscript are included in this Dryad submission. Further questions about the data can be made through the British Columbia Ministry of Forests