From Trees to Ecosystems: Spatiotemporal Scaling of Climatic Impacts on Montane Landscapes Using Dendrochronological, Isotopic, and Remotely Sensed Data

Abstract

AbstractAn interdisciplinary approach is needed for understanding tree physiology and forest biogeochemical cycles undergoing climate change and rising atmospheric CO2. We combined tree ring time series, wood isotope signatures, remotely sensed variables, and climatic data to perform a spatiotemporal scaling analysis of tree physiology and high‐elevation forest responses to rising CO2. The main question addressed is how tree physiological performance of dominant trees can be combined with satellite‐derived information of stand‐level productivity to understand how the landscape shapes the relationship between forest structure and function. Annually resolved tree ring carbon and oxygen isotopic ratios (δ13C and δ18O), carbon isotope discrimination from CO2 to wood (Δ13C), and intrinsic water‐use efficiency (iWUE) of dominant Pinus hartwegii Lindl. trees were sampled and compared against stand‐level normalized difference vegetation index (NDVI) time series from 2000 to 2016. Linear mixed‐effects models tested the effects of elevation, aspect, and time. Carbon and oxygen isotope ratios were correlated with NDVI mainly for the previous fall‐winter season and for the beginning of the growing season. Wood δ13C decreased over time regardless of spatial position, whereas wood δ18O varied as a function of altitude and time. Although Δ13C did not vary with elevation, aspect, or time, a notable decline in Δ13C and peak in iWUE during a severe drought event was evident. Results highlight the link between remotely sensed data, tree ring isotopic composition, and tree physiology as the determining factors to determine spatiotemporal variability in dendroecological studies.