DOI: 10.5061/dryad.v9s4mw756
title: Functional attributes of conifers expanding into temperate semi-arid grasslands modulate carbon and nitrogen fluxes in response to prescribed fire

description: Fire exclusion is a key factor driving conifer expansion into temperate
 semi-arid grasslands. However, it remains unclear how reintroducing fire
 affects the aboveground storage of carbon (C) and nitrogen (N) in the
 encroaching tree species and belowground in soils. To assess the impacts
 of fire reintroduction C and N pools and fluxes in areas of conifer
 expansion we targeted a region of the Northern Great Plains that has
 experienced extensive woody plant expansion (WPE) of two species:
 ponderosa pine (Pinus ponderosa) and juniper (Juniperus spp). We
 quantified tree mortality of both species to estimate the amount of dead
 biomass C and N produced by a recent prescribed fire, in addition to
 changes in soil C, pyrogenic C (PyC), and N concentrations across a
 woody-cover gradient using a before/after/control experimental design.
 Post-fire soil chemical analysis revealed a 2-year increase in mineral
 soil C, PyC and N, suggesting the return of fire led to the transfer of
 partially combusted plant organic matter back to the soil.
  Further, we found that functional trait differences between the
 two species influenced the distribution of living conifer biomass-N prior
 to fire. Despite junipers having 41% less total aboveground biomass than
 ponderosa, they contained two times more aboveground N. Prescribed fire
 resulted in 88% mortality of all mature juniper stems and increased fire
 severity correlated with greater pre-fire juniper cover. Ponderosa
 mortality varied by size class, with &gt;40 cm stem diameter class
 having only 28% mortality. High mortality and greater aboveground N
 storage in juniper biomass, compared to ponderosa, led to 77% of the total
 conifer biomass N lost. Consequently, the functional attributes of
 expanding trees differentially contribute to fluxes of C and N after the
 return of fire, with junipers acting as conduits for N movement due to
 their relatively higher N content in less fire-resistant tissues and
 ponderosa serving as important and more stable storage pools for C.
 Together, these findings highlight the importance of considering
 species-specific traits when planning WPE management strategies at
 landscape-scales, particularly when goals include C storage or soil
 nutrient status.
description: The data from this study was collected over multiple field
 seasons and includes soil chemistry, bole and foliar biomass chemistry for
 pinus ponderosa and juniperus scopulorum, individual ponderosa stem
 measurements and biophsyical data for field plot
 characterization. 
description: # Functional attributes of conifers expanding into temperate semi-arid
 grasslands modulate carbon and nitrogen fluxes in response to prescribed
 fire
 [https://doi.org/10.5061/dryad.v9s4mw756](https://doi.org/10.5061/dryad.v9s4mw756) ## Description of the data and file structure Data include 1. pre and post soil chemistry concentrations and area scaled pools (0-10 cm soil depth) 2. biophysical plot characteristics 3. individual pinus ponderosa stem measurements 4. needle leaf and bole chemistry for pinus ponderosa and juniperus scopulorum All NA's indicate missing or unmeasured values See associated manuscript for detailed information on collection, processing, and analysis. ### Files and variables #### File: fire\_soil\_chemistry.csv **Description:** Soil chemistry at a 0-10 cm soil depth pre and post fire treatment ##### Variables * Plot: Plot identifer * Label: month and day of sample collection * Month: month of collection * Year: year of collection * Treatment: fire treatment (pre, post, burned, and unburned controls) * C_conc: soil C concentration (%) * N_conc: soil C concentration (%) * C_N: soil C:N * Bulk_density: soil bulk density in g cm^3 * SOC_pool: area scaled soil carbon pool Mg C ha^-1 * TN_pool: area scaled soil nitrogen pool Mg N ha^-1 * PyC: pyrogenic carbon concentration (%) * PyC_pool: area scaled soil pyrogenic carbon pool Mg PyC ha^-1 * PyC_C: Ratio of PyC:C #### File: DIN.csv **Description:** Inorganic nitrogen concentrations via KCl field moist extractions (2M) at 0-10 cm soil depth, pre and post fire treatment ##### Variables * Plot: plot identifier * Month: month of sample collection * Year: year of sample collection * DIN: dissolved inorganic nitrogen concentration ug g^-1 dry soil (KCl extractable) * Type: Identifier for NO3-N or NH4-N * Fire: Treatment (pre, post, burned, and unburned controls) #### File: wood\_leaf\_chem.csv **Description:** Woody and foliar biomass chemistry ##### Variables * Field id: Tree species and tissue type * Sample ID: Unique identifier * Species: Tree species * Tissue: tissue type (bole wood or needle leaf) * N: Nitrogen concentration in % of mass * P: Phosphorus concentration in % of mass * S: Sulfur concentration in % of mass * Ca: Calcium concentration in % mass * Mg: Magnesium concentration in % of mass * Na: Sodium concentration in % of mass * Zn: Zinc concentration in % of mass * Fe: Iron concentration in % of mass * Mn: Manganese concentration in % of mass * Cu: Copper concentration in % of mass * B: Boron concentration in % of mass * C: Carbon concentration in % of mass #### File: plot\_characteristics.csv **Description:** biophysical plot characteristics  ##### Variables * plot: plot identifier * longitude: in decimal degrees * latitude: in decimal degrees * elevation: in meters above sea level * aspect: primary aspect in a cardinal direction (N,E,S,W) * sin_asp: * cos_asp: * ph: soil ph 0-10 cm depth * slope: slope angle in degrees * bulk_density: soil bulk density in g cm ^3 * mature_stem_density: mature tree (ponderosa and juniper) stems per 0.04 ha * Max_age: max tree age (ponderosa and juniper) in the plot * Pondo_cover: ponderosa over per plot (%) * June_cover: juniper cover per plot (%) * Woody_cover: total woody cover of plot (%) * juniper_mortality: % of junipers that were classified as dead after the fire via &gt; 70% crown scorch * ponderosa_mortality: % of junipers that were classified as dead after the fire via &gt; 70% crown scorch #### File: tree\_measurements.csv **Description:** Individual tree measurements on just ponderosa pine stems ##### Variables * Year: year of measurement * Plot: plot tree is located in * Tree: unique identifier for each mature ponderosa in the plot * TreeBurnSeverity: burn classification (0 = no evidence of burn, 1 = light evidence of burning, 2= moderate evidence of burning, 3 = extensive evidence of burning) * DBH: Diameter at breast height (cm) * Height: Tree height in meters * BA: Basal area ## Code/software All analysis was conducted in R.