DOI: 10.5061/dryad.7d7wm380c
title: Land use change converts temperate dryland landscape into a net methane source

description: Drylands cover approximately 40% of the global land surface and are
 thought to contribute significantly to the soil methane sink. However,
 large-scale methane budgets have not fully considered the influence of
 agricultural land use change in drylands, which often includes irrigation
 to create land cover types that support hay or grains for livestock
 production. These land cover types may represent a small proportion of the
 landscape but could disproportionately contribute to greenhouse gas
 exchange and are currently omitted in estimates of dryland methane fluxes.
 We measured greenhouse gas fluxes among big sagebrush, introduced
 wetlands, and hay meadows in a semi-arid temperate dryland in Wyoming, USA
 to investigate how these small-scale irrigated land cover types
 contributed to landscape-scale methane dynamics. Big sagebrush ecosystems
 dominated the landscape while the introduced wetlands and hay meadows
 represented 1% and 12%, respectively. Methane uptake was consistent in the
 big sagebrush ecosystems, emissions and uptake were variable in the hay
 meadows, and emissions were consistent in the introduced wetlands. Despite
 making up 1% of the total land area, methane production in the introduced
 wetlands overwhelmed consumption occurring throughout the rest of the
 landscape, making this region a net methane source. Our work suggests that
 introduced wetlands and other irrigated land cover types created for
 livestock production may represent a significant, previously overlooked
 source of anthropogenic methane in this region and perhaps in drylands
 globally.
description: Raw flux data for methane, carbon dioxide, and other species were
 measured using a paired Picarro-Licor trace gas analyzer from June –
 August 2021 (flux data is in ghg_raw.csv, data for statistical analysis in
 ghg_stats.csv). Net nitrogen mineralization data was collected through ion
 exchange resins (data is in n_raw.csv). Bulk density, soil texture, pH,
 and soil carbon and nitrogen were completed on soil samples analyzed at
 Yale University (data is in soilcn.csv). Carbon and nitrogen were measured
 on an elemental analyzer. Soil texture was estimated using particle size
 analysis. pH was measured using a bench top pH meter. Land cover
 classification was done using the NatureServe database for Sublette
 County, WY (data used for scaling is in landcover.xlsx and shapefile is in
 landcover.zip). In 'included' tab on landcover.xlsx, there are
 two sections of data on the left and right, not one rectangular table of
 data.
description: # Land use change converts temperate dryland landscape into a net methane
 source Raw flux data for methane, carbon dioxide, and other species were
 measured using a paired Picarro-Licor trace gas analyzer from June –
 August 2021 (flux data is in `ghg_raw.csv`, data for statistical analysis
 in `ghg_stats.csv`). Net nitrogen mineralization data was collected
 through ion exchange resins (data is in `n_raw.csv`). Bulk density, soil
 texture, pH, and soil carbon and nitrogen were completed on soil samples
 analyzed at Yale University (data is in `soilcn.csv`). Carbon and nitrogen
 were measured on an elemental analyzer. Soil texture was estimated using
 particle size analysis. pH was measured using a bench top pH meter. Land
 cover classification was done using the NatureServe database for Sublette
 County, WY (data is in `landcover.xlsx` and in landcover.zip). In
 'included' tab on landcover.xlsx, there are two sections of data
 on the left and right, not one rectangular table of data. ## Description
 of the data and file structure #### ghg\_raw\.csv: * date: date of
 sampling (mm/dd/yy) * week: week of sampling (Week 1 - Week 11) * id: soil
 collar ID * ranch: site name (site1-3) * location: one of the four land
 cover types measured [meadow (hay meadow); bog (introduced wetland);
 slsage (sloping sagebrush); upsage (upland sagebrush)] * sh/is: indicates
 whether sample was taken under shrub or in the interspace * stemp: soil
 temperature ('b0C) * pcent_sand: % sand content * ph: soil pH *
 chamber offset: height of soil collar from the surface of soil (measured
 in cm) * volume add: volume added through extension of chamber attachment
 (cm3) * start time: start time of sampling (hour:minute:second) * end
 time: end time of sampling (hour:minute:second) * time off: offset from
 the time read by the two instruments (s) * co2 flux: carbon dioxide flux
 measured over 8 minute period (umol co2 m-2 s-1) * co2 rsq: R-squared of
 exponential fit of values over 8 minute period * ch4 flux: methane flux
 measured over 8 minute period (umol ch4 m-2 s-1) * ch4 rsq: R-squared of
 exponential fit of values over 8 minute period * n2o flux: nitrous oxide
 flux measured over 8 minute period (umol n2o m-2 s-1) * n2o rsq: R-squared
 of exponential fit of values over 8 minute period * nh3 flux: ammonia flux
 measured over 8 minute period (umol nh3 m-2 s-1) * nh3 rsq: R-squared of
 exponential fit of values over 8 minute period * h2o flux: h2o flux (%
 water vapor) * h2o rsq: R-squared of exponential fit of values over 8
 minute period * notes: anything important to note from data collection of
 that day #### ghgstats.csv: * date: date of sampling (mm/dd/yy) * week:
 week of sampling (Week 1 - Week 11) * id: soil collar ID * ranch: site
 name (site1-3) * location: one of the four land cover types measured
 [meadow (hay meadow); bog (introduced wetland); slsage (sloping
 sagebrush); upsage (upland sagebrush)] * stemp: soil temperature
 ('b0C) * h2o flux: h2o flux (% water vapor) * h2o rsq: R-squared of
 exponential fit of values over 8 minute period * sand: % sand content (0-5
 cm) * clay: % clay content (0-5 cm) * pH: soil pH (0-5 cm) * carbon: %
 soil carbon (0-5 cm) * nitrogen: % soil nitrogen (0-5 cm) * co2 flux:
 carbon dioxide flux measured over 8 minute period (umol co2 m-2 s-1) * co2
 rsq: R-squared of exponential fit of values over 8 minute period * ch4
 flux: methane flux measured over 8 minute period (umol ch4 m-2 s-1) * ch4
 rsq: R-squared of exponential fit of values over 8 minute period ####
 n\_raw\.csv: * ranch: site name (site1-3) * location: one of the four land
 cover types measured [meadow (hay meadow); bog (introduced wetland);
 slsage (sloping sagebrush); upsage (upland sagebrush)] * no3: nitrate
 concentrations (ug no3/10cm2/burial length) * nh4: ammonium concentrations
 (ug nh4/10cm2/burial length) * fe: iron concentrations (ug fe/10cm2/burial
 length) * s: sulfur concentrations (ug s/10cm2/burial length) ####
 soilcn.csv: * ranch: site name (site1-3) * location: one of the four land
 cover types measured [meadow (hay meadow); bog (introduced wetland);
 slsage (sloping sagebrush); upsage (upland sagebrush)] * depth: depth of
 soil sample (cm) * finebulkd: fine soil bulk density (g soil cm-3) * c: %
 soil carbon (0-5 cm) * n: % soil N (0-5 cm) * cpool: total soil carbon for
 0-5 cm (g C m-2) * npool: total soil N for 0-5 cm (g N m-2) ####
 landcover.xlsx: Sheet1 (ecosystems): * gridcode: NatureServe grid code
 assignment * Shape Area: area covered by a given land cover type (m2) *
 Value: grid code assignment * Count: Number of land cover types classified
 under a given name within the county boundary * ECOLSYS_LU: Land cover
 type classification under NatureServe categories Sheet2 (included): *
 ecotype: Land cover type classification under NatureServe categories *
 shape area: area covered by a given land cover type (m2) * Total shape
 area: area covered by landscape of included cover types (m2) * %
 introduced wetland: % of area represented by introduced wetland cover
 types within landscape * % hay meadow: % of area represented by hay meadow
 cover types within landscape * % big sagebrush: % of area represented by
 big sagebrush cover types within landscape #### **landcover.zip** *
 landcover.dbf: database file, attribute data  * landcover.prj: projection
 file, coordinate system  * landcover.shp: shapefile, stores geometry of
 spatial data  * landcover.shx: shape index file  ## Code/Software ####
 figs.R: used to make the primary figures for the manuscript and
 supplementary figures Completed in R (version 4.4.2) Packages: `ggplot2`,
 `wesanderson`, `stringr`, `zoo`, `tidyverse`, `scales`, `ggpubr`,
 `cowplot`, `gt`, `dplyr`,  'sf' #### stats.R: -used to do the
 statistical analysis for the manuscript -Completed in R (version 4.4.2)
 -Packages: 'pracma', `tidyverse`, `ggpubr`, `rstatix`, `lme4`,
 'lmerTest', `emmeans`, 'car', `MASS`, `glmm` ##
 **Supplementary ** scalefigure.pptx * used to make figure 6 for manuscript
 (weighted cumulative methane flux by cover type)  ## Changes from previous
 version:  * Created a few different figures (one land cover map and made
 some edits to existing figures). The script 'figs.r' reflects
 those changes. I added the land cover shapefile I used to make the land
 cover map (landcover.zip). I ran a few new analyses on cumulative gas
 fluxes, which is included in the script, 'stats.r'. All other
 files are the same.