A roadmap to disentangling ecogeographical patterns of spatial synchrony in dendrosciences

Abstract

A systematic assessment of spatial synchrony in tree growth, a fundamental feature of spatiotemporal forest dynamics, can provide valuable insights into complex tree reactions across species and environmental gradients. The concept of spatial synchrony in ecology refers to the presence of coordinated time fluctuations in certain characteristics that can be observed in plant and animal communities inhabiting an area. It is a well-known phenomenon common to virtually every taxon, but comparatively little attention has been given to the study of the temporal coherence of forest tree performance across biogeographical gradients. In forest ecosystems, tree growth dynamics is primarily driven by climatic variability (i.e., the Moran effect). Due to rapid climate change, trees are increasingly pushed to their physiological limits up to the level that many populations are facing immediate risk of extinction. The characterization of synchrony patterns in tree growth can provide clues on the relevance of emerging climatic threats on forests, as new combinations of precipitation and temperature are entraining tree performance worldwide. In this regard, comprehensive and systematic approaches to analyse spatiotemporal dynamics of tree growth are needed. Here, we present a methodology for disentangling and interpreting how the variability and common signal strength of tree growth (or other traits) are structured in tree-ring networks. It is grounded on mixed modelling principles and broadens well-known theoretical principles in dendrosciences. Based on this approach, we describe the essential properties of spatial synchrony in tree growth at multiple geographical scales. We also discuss the potential of this methodology to discern early warning signals of climate change impacts on forest ecosystems.