Title of Dataset: Dirt cheap: An experimental test of controls on resource exchange in an ectomycorrhizal symbiosis

# Title of Dataset: Dirt cheap: An experimental test of controls on resource exchange in an ectomycorrhizal symbiosis --- We measured resource (carbon (C), nitrogen (N), and phosphorus (P)) transfers, and their ratios, between Pinus taeda seedlings and two ectomycorrhizal (EM) fungal species, Rhizopogon roseolus and Pisolithus arhizus in a laboratory experiment. To test effects of light, fungal species, and time on absolute amounts and ratios of transferred resources (Question 1), data on C, N, and P fluxes, and N:C and P:C exchange prices were analyzed as response variables in separate univariate analyses using linear mixed-effects models using the lmerTest package in R version 3.5.2, with growth period (1, 2, and 3), light level (high and low), EM fungal species, and their interactions as fixed effects. To test for effects of resource transfer on accumulated fungal and plant biomass (Question 2), we conducted model selection among all possible linear mixed-effect models for which the candidate variables were the main effects of the five resource flux variables representing effects of total resource transfer and exchange ratios (C, P, N, N:C, N:P). ## Description of the Data and file structure The data are structured in a flat file, with each variable in a unique column. There are variables representing the three manipulated experimental factors, Light (low & high), Fungi (Rhizopogon and Pisolithus), and growth period (10 weeks, 20 weeks, and 30 weeks). The other variables represent resource fluxes of C, N, and P, and their ratios, fungal C partitioned between respiration and C in biomass, as well as plant biomass and fungal biomass. The associated article describes analyses that can be detected using these variables. ## Sharing/access Information Links to other publicly accessible locations of the data: Was data derived from another source? No If yes, list source(s): ## Each row provides data on a unique experimental unit (mycocosm). Each variable in the dataset is described below: Number: Integer indicating a unique experimental unit (mycocosm) (range: 25 to 231) Planted: Date on which the experimental unit was planted, i.e., a seedling was inoculated with mycorrhizal fungal spores and transplanted into soil in a mycocosm Harvest.date: Date (format: month/day/year; values: 10/18/2017 to 2/22/2018) on which the mycocosm was destructively harvested (format: month/day/year, values: 8/4/2016 or 8/6/2017) Days in Experiment: Integer indicating number of days between planting and harvest for an experimental unit (range: 73 to 202) Mycocosm: Categorical code unique for each individual mycocosm, which indicates (in part) its treatment and replicate (format: WWXXYZZ, where WW indicates fungal species and can take values Pi or Rh indicating Pisolithus arhizus or Rhizopogon roseolus respectively; XX indicates genotype of Pinus taeda and can take values 13 or 18; Y indicates low or high light treatment and can take values L or H respectively; ZZ indicates a replicate mycocosm within each combination of fungal species, pine genotype, and light treatment, and can take integer values 1 to 122) Tree: Integer indicating genotype of Pinus taeda (values: 13 or 18); the values 13 and 18 are categorical, with no quantitative interpretation Harvest: Integer indicating approximate number of weeks of growth before harvest (values: 10, 20, or 30) Fungi: Indicates which ectomycorrhizal fungal species was inoculated in each mycocosm (values: Rhizopogon or Pisolithus, indicating Rhizopogon roseolus or Pisolithus arhizus respectively) Replicate: Integer indicating a replicate mycocosm within each combination of fungal species, pine genotype, and light treatment (range: 1 to 122) Shelf: Character variable indicating which growth chamber shelf a mycocosm was grown on (format: XY, where X indicates left or right growth chamber in the Hoeksema laboratory at the University of Mississippi and can take values L or R respectively, and X indicates whether a shelf received a high or low light treatment and can take values H or L respectively) Light: Character variable indicating low or high light treatment (values: Low or High) biomass.C_umol: Continuous variable indicating estimated mass of carbon (micromoles) in fungal biomass in a mycocosm at harvest respired.C_umol: Continuous variable indicating estimated mass of carbon (micromoles) cumulatively respired by the fungus in a mycocosm from planting to harvest total.C_umol: Continuous variable indicating estimated total mass of carbon (micromoles) transferred to the fungus in a mycocosm from planting to harvest, calculated as sum of biomass.C_umol and respired.C_umol N:C: Continuous variable indicating estimated ratio of total nitrogen (N, micromoles) transferred to plant divided by total carbon (C, micromoles) transferred to fungus in a mycocosm from planting to harvest P:C: Continuous variable indicating estimated ratio of total phosphorus (P, micromoles) transferred to plant divided by total carbon (C, micromoles) transferred to fungus in a mycocosm from planting to harvest total.N: Continuous variable indicating estimated total nitrogen (N, micromoles) transferred to plant in a mycocosm from planting to harvest total.P: Continuous variable indicating estimated total phosphorus (P, micromoles) transferred to plant in a mycocosm from planting to harvest fungalmass_ug: Continuous variable indicating estimated total fungual biomass (micrograms) in a mycocosm at harvest plantmass_g: Continuous variable indicating estimated total dry plant biomass (grams) of the pine seedling in a mycocosm at harvest