Forests synchronize their growth in contrasting Eurasian regions in response to climate warming

Abstract

Forests play a key role in the carbon balance of terrestrial ecosystems. One of the main uncertainties in global change predictions lies in how the spatiotemporal dynamics of forest productivity will be affected by climate warming. Here we show an increasing influence of climate on the spatial variability of tree growth during the last 120 y, ultimately leading to unprecedented temporal coherence in ring-width records over wide geographical scales (spatial synchrony). Synchrony in growth patterns across cold-constrained (central Siberia) and droughtconstrained (Spain) Eurasian conifer forests have peaked in the early 21st century at subcontinental scales (∼1,000 km). Such enhanced synchrony is similar to that observed in trees co-occurring within a stand. In boreal forests, the combined effects of recent warming and increasing intensity of climate extremes are enhancing synchrony through an earlier start of wood formation and a stronger impact of year-to-year fluctuations of growing-season temperatures on growth. In Mediterranean forests, the impact of warming on synchrony is related mainly to an advanced onset of growth and the strengthening of droughtinduced growth limitations. Spatial patterns of enhanced synchrony represent early warning signals of climate change impacts on forest ecosystems at subcontinental scales. U nderstanding how climate change affects forests across multiple spatiotemporal scales is important for anticipating its impacts on terrestrial ecosystems. Increases in atmospheric CO 2 concentration and shifts in phenology (1-3) could favor tree growth by enhancing photosynthesis and extending the effective growing period, respectively (4). Conversely, recent warming could increase respiration rates and, together with increasing heat and drought stresses, exert negative impacts on forest productivity (5, 6). Given the uncertainty as to what extent enhanced carbon uptake could be offset by the detrimental effects of warming on tree performance, the actual consequences of climate change on forest carbon cycling remain under debate. Notably, climate change has a stronger impact on forests constrained by climatic stressors, such as suboptimal temperatures or water shortage (7). As high-resolution repositories of biological responses to the environment, dendrochronological archives can be used to monitor this impact (8).The concept of spatial synchrony in tree growth refers to the extent of coincident changes in ring-width patterns among geographically disjunct tree populations (9). Climatic restrictions tend to strengthen growth-climate relationships, resulting in enhanced common ringwidth signals (i.e., more synchronous tree growth). Thus, regional bioclimatic patterns can be delineated by identifying groups of trees whose growth is synchronously driven by certain climatic constraints (10, 11). Previous synthesis studies have provided evidence for globally coherent multispecies responses to climate change in natural systems, including forests, with a focus on the role of increasingly warmer tempe...

Synchrony affects Taylor’s law in theory and data

“…Increasing evidence shows that changing Moran effects, possibly due to climate change, modify synchrony (19,21,(26)(27)(28). This work indicates that changed synchrony will modify the slope and possibly the validity of TL, with ramifications for applications of TL in many areas, including resource management (3), conservation (11), human demography (6), tornado outbreaks (8), and agriculture (2,12,13).…”

“…Understanding the relationship of synchrony with TL is important, because both patterns are widespread in population ecology, and because TL and recent observed climate changeinduced modifications in synchrony have applied importance (19,21,(26)(27)(28).…”

“…Large-scale climatic changes in the North Atlantic Oscillation caused changes in winter temperature synchrony, which in turn caused changes in the synchrony of pest aphid species in the United Kingdom (27). Changes in the synchrony of plankton (26) and tree rings (28) have been associated with climate change. If synchrony influences TL,…”

Minimum wood density of conifers portrays changes in early season precipitation at dry and cold Eurasian regions

“…An increasing influence of climate warming on temporal coherence in ringwidth records (spatial synchrony) have been observed across some of the studied Eurasian regions (Shestakova et al 2016). It could be tested if this enhanced synchrony holds too for density records at similar sub-continental scales since wood density seasonal components (MN, MX) respond to different climate variables, and wood density is a fundamental variable to estimate forest carbon uptake and woody biomass pools (Bouriaud et al 2015).…”

The High Mountain Conservation in a Changing World

“…Floods related to rain-on-snow events may increase (Beniston and Stoffel 2016), at least during a transition period as warming proceed. All things considered, climate change may increase synchrony between ecosystems compared to pre-industrial dynamics, which appears to be the case for forest over large areas (Shestakova et al 2016). …”