The effect of shrub cover on conifer water-use patterns, growth, and response to climate change in the southern Sierra Nevada

As wildfire increases in size and severity, large areas of forest are undergoing substantial increases in shrub cover. In forests where water is the limiting resource, the paritioning of soil water between shrubs and trees may determine how shrubs affect tree growth and water-stress. We analyzed hydrogen and oxygen isotopes in the xylem water for two conifer species and two shrub species to assess how shrub cover affects the water-uptake patterns of conifers in the southern Sierra Nevada. Further, we analyzed tree growth and stable carbon isotopes in tree rings to assess how shrub cover affects tree growth, intrinsic water-use efficiency and response to climate change., Xylem samples were collected from two conifer species (Abies concolor and Pinus jeffreyi) and two shrub species (Arctostaphylos patula and Ceanothus cordulatus) in the southern Sierra Nevada. Soil samples were collected near a subset of the sampled trees. Xylem water and soil water were extracted using a cryogenic vacuum distillation and analyzed for hydrogen and oxygen stable isotopes.
Trees of both conifer species were cored or cross-sectioned after xylem samples were collected. Tree-ring analysis was used to calculate age and growth for each tree and carbon isotope analysis was performed on wood samples obtained from each tree core/cross section. , , Data and Code for \"The effect of shrub cover on conifer water-use patterns, growth, and response to climate change in the southern Sierra Nevada\"

Created by Marissa J. Goodwin

Code:
Shrub-Tree Water Use.Rmd = Code for data analysis

Dataframes:

Raw Soil Data.csv - This dataframe contains soil water hydrogen and oxygen data for each growing environment and tree species combination at three soil depths (0-10 cm, 10-20 cm, 20-30 cm). Columns are as follows: \"Identifier.1\" = unique identifier for each soil sample (some soil samples were analyzed twice), \"d18OVsmow\" = oxygen isotope ratio, \"d2HVsmow\" = hydrogen isotope ratio, \"Species.Shrub\" = Tree Species and growing environment combination (AO = white fir-Open, AS= white fir-Shrub, PO = Jeffrey pine-Open, PS = Jeffrey pine-Shrub), \"Site\" = Growing Environment (Open = Shrub Absent and Shrub = Shrub Dominant)

Xylem Water Data.csv - This dataframe contains xylem water hydrgoen and oxygen data for all trees and shrubs in each growing envi...