DOI: 10.5061/dryad.mcvdnck6p
title: Leather oak (Quercus durata) herbarium leaf N and C stable isotopes and tree ring width index

description: Increasing anthropogenic emissions of nitrogen (N) and carbon (C) are
 major threats to ecosystems globally. Although atmospheric N deposition is
 likely affecting N cycling and community composition in California’s
 serpentine ecosystems, a historical record of N inputs to vegetation has
 yet to be reconstructed for these nutrient-limited biodiversity hotspots.
 For leather oak (Quercus durata var. durata), a foundational,
 serpentine-endemic species, we investigated leaf N and C isotopic
 composition (δ15N and δ13C) and leaf %N of herbarium and modern leaf
 samples collected from 1899 to 2009 from serpentine ecosystems in two
 study areas in California: Santa Clara County, and Lake and Napa Counties
 combined. We also evaluated tree ring growth over a similar time period in
 long-lived leather oak individuals. Leaf δ15N and δ13C values decreased
 over time in both study areas, likely reflecting changes in the regional
 atmospheric N and C pools caused by human perturbation.  However,
 leaf %N values and stem growth did not change directionally over time,
 indicating that increasing atmospheric N deposition and CO2 concentration
 may not translate to increased N uptake or productivity in plants with
 conservative growth strategies, even in ecosystems thought to be
 N-limited.  In serpentine systems, this could competitively
 advantage nitrophilic invasive annual grasses and accelerate trends toward
 native species loss.  While the rates of decline in leaf δ15N
 values were similar between study areas, rates of decline in leaf δ13C
 values were steeper in Santa Clara County, possibly reflecting its more
 urban environment.  Herbarium samples combined with tree ring
 data can provide a valuable opportunity to explore the historical record
 of human-induced changes in N and C cycling and their biotic
 impacts. 
description: # Leather oak (Quercus durata) herbarium leaf sample N isotope and tree
 ring width index
 [https://doi.org/10.5061/dryad.mcvdnck6p](https://doi.org/10.5061/dryad.mcvdnck6p) ## Description of the data and file structure [https://doi.org/10.5061/dryad.mcvdnck6p](https://doi.org/10.5061/dryad.mcvdnck6p) This file includes a 1) a data set on tree ring widths and ring width index from cores taken at McLaughlin Reserve in Lake County and Coyote Ridge Preserve in Santa Clara County, California; and 2) a set of leaf N and C stable isotope measurements and leaf %N from herbarium and modern samples collected throughout Lake and Napa Counties and Santa Clara County, California. ## Description of the data and file structure The files has two tabs. Tab one, Leaf Data, includes the leaf data and tab two includes the tree ring data (ring width index). Variables are Date, indicating the date the sample was taken; Accession or ID #, indicating the number associated with the herbarium sample; 15N, indicating the delta 15N value of the leaf; %N, indicating the percent N of the leaf; 13C, indicating the delta 13C value of the leaf, and location, indicating the county in which the sample was collected. The Accession or ID # includes an abbreviation for the herbarium (CAS=California Academy of Sciences, UC=University of California). For modern samples, the Accession or ID # column includes an independent identifier number, date = collection date. Tab two, RWI data, includes County, indicating the county where the core sample was collected; Years, indicating the years covered by the core sample. Columns C-W represent the individual tree cores, where T(#) identifies the tree from which the core was taken, and RWI refers to the averaged calculated ring width index for the time period indicated. ### Files and variables #### File: Data\_File.xlsx **Description:** Tab 1 Leaf data ##### Variables Date, indicating the date the sample was taken Accession or ID #, indicating the number associated with the herbarium sample. The Accession or ID # includes an abbreviation for the herbarium (CAS=California Academy of Sciences, UC=University of California). 15N, indicating the delta 15N value of the leaf %N, indicating the percent N of the leaf 13C, indicating the delta 13C value of the leaf Location, indicating the county in which the sample was collected. **Description: Tab 2 RWI data** **Variables** County, indicating the county where the core sample was collected Years, indicating the years covered by the core sample Columns C-W represent the individual tree cores, where T(#) identifies the tree from which the core was taken, and RWI refers to the averaged calculated ring width index for the time period indicated ## Code/software excel