total). Half of the study trees will be located on wet sites and half on dry sites as illustrated in Figure 1. Tree water utilization will be compared before and after prescribed burns. Fire damage to trees naturally exhibits high spatial variability, with some trees suffering relatively severe effects while others experience minimum to no effects. We will take advantage of this variability by comparing tree water utilization dynamics along a continuous gradient of observed fire damage (e.g., basal scarring and crown scorch). We will collect samples of tree xylem water, soil water at different depths, and groundwater obtained from wells and springs located near each grove for isotopic analysis. Event-based precipitation samples (rain and snow) will be collected within or near each grove throughout the study period using standard protocols (IAEA/GNIP 2014) and used to establish a local meteoric water line (LMWL). Tree xylem, soil and ground water samples will be collected 4 times per year – in May/June, July, September and November – to characterize variation of isotopic signatures throughout the growing season. Tree xylem water will be collected from sapwood obtained from two replicate increment cores at 10m height on opposites sides of each tree trunk. Cores are collected at 10m in order to avoid persistent weeping of water from bore holes that occurs when coring sequoia trees at ground level. Increment cores will be obtained by climbing each tree using rope-based arborist techniques. Soil cores to 1m depth will be obtained using a soil borer and separated into 4 evenly distributed samples to characterize soil isotopic profiles.

Approved