Fig. 2.
The sampling design is shown starting with regional scale variables on the left, stand scale properties in the middle, and plant scale on the right, based on the scale at which each property was measured. Transects were established on different parent materials (BS, AN, and GR) selected for their prevalence across the Sierra Nevada and for their contrasting mineralogical properties that result from differences in weatherability. At the stand scale, a number of dynamic climatic and ecosystem variables represent general trends associated with elevational gain at all transects. Soil weathering was measured as clay content, secondary iron (Fed), and as a function of a pedogenic energy (Eped). Canopy density was measured by hemispherical photography used to calculate LAI, which was compared with stand-level NDVI, a satellite-based measure of greenness and productivity. Climate variables were derived from the PRISM model (26). Tree-level variables, such as isotopic composition and nitrogen content, were measured to help understand resource limitation and photosynthetic capacity across the gradient. Taken together, these variables were used to investigate how species traits and soil properties affect productivity and water-use efficiency of trees and forests throughout the region.