Tree growth influenced by warming winter climate and summer moisture availability in northern temperate forests.

Jill E Harvey,Adomas Vitas,Āris Jansons,Martin Wilmking,Tobias Scharnweber,Kristina Sohar,Karolina Janecka,Marcin Klisz,Roberto Cruz‐García,Anna Cedro,Juliane Stolz,Robert Weigel,Igor Drobyshev,Ernst Van Der Maaten,Allan Buras,Lena Muffler,Alar Läänelaid,Marieke Van Der Maaten‐Theunissen,Barbara Spyt,Roberts Matisons,Marko Smiljanić,Jüergen Kreyling ,Ryszard J Kaczka

doi:10.1111/gcb.14966

Abstract

The role of future forests in global biogeochemical cycles will depend on how different tree species respond to climate. Interpreting the response of forest growth to climate change requires an understanding of the temporal and spatial patterns of seasonal climatic influences on the growth of common tree species. We constructed a new network of 310 tree-ring width chronologies from three common tree species (Quercus robur, Pinus sylvestris and Fagus sylvatica) collected for different ecological, management and climate purposes in the south Baltic Sea region at the border of three bioclimatic zones (temperate continental, oceanic, southern boreal). The major climate factors (temperature, precipitation, drought) affecting tree growth at monthly and seasonal scales were identified. Our analysis documents that 20th century Scots pine and deciduous species growth is generally controlled by different climate parameters, and that summer moisture availability is increasingly important for the growth of deciduous species examined. We report changes in the influence of winter climate variables over the last decades, where a decreasing influence of late winter temperature on deciduous tree growth and an increasing influence of winter temperature on Scots pine growth was found. By comparing climate-growth responses for the 1943-1972 and 1973-2002 periods and characterizing site-level growth response stability, a descriptive application of spatial segregation analysis distinguished sites with stable responses to dominant climate parameters (northeast of the study region), and sites that collectively showed unstable responses to winter climate (southeast of the study region). The findings presented here highlight the temporally unstable and nonuniform responses of tree growth to climate variability, and that there are geographical coherent regions where these changes are similar. Considering continued climate change in the future, our results provide important regional perspectives on recent broad-scale climate-growth relationships for trees across the temperate to boreal forest transition around the south Baltic Sea.

Highlights

The productivity, composition and functional role of future forests in global biogeochemical cycles will depend on how different tree species respond to climate, competition with neighbours, and local environmental conditions
We focused on two climate–growth relationships for each tree species: (a) the dominant climate variable influencing the regional growth of a species across the study region (‘dominant climate response’), and (b) the climate–growth relationship that exhibited the greatest change in strength and/or direction when we compared the response for the two 30 year periods (‘greatest change climate response’)
Variability in correlation strength and direction was detected among sites for each climate variable and for each tree species, we report here (a) the broadly dominant relationship between tree growth and climate, and (b) the climate–growth relationship exhibiting the greatest change over the 1943–2002 period

Summary

Introduction

The productivity, composition and functional role of future forests in global biogeochemical cycles will depend on how different tree species respond to climate, competition with neighbours, and local environmental conditions. Climate change effects on vegetation have been documented at annual and seasonal scales, with the most research directed at evaluating the effects of climate in summer months. Climate warming is more pronounced in winter than summer at locations in the mid- to high-latitudes (Xia et al, 2014), where changing winter precipitation patterns (spatial and temporal variability, type; Wu et al, 2019), extreme cold events (magnitude and frequency; Kodra, Steinhaeuser, & Ganguly, 2011) and temperature (variability in extremes and mean) can independently and collectively influence patterns of vegetation growth and distribution, especially in temperate mixed-wood forests (Kreyling, 2010; Kreyling & Henry, 2011). To better identify the effects of these climatic changes on forest productivity, spatially explicit estimations of tree growth (i.e. radial tree-ring growth) responses to seasonal climate are required. Analyses assessing the stationarity of these climate–growth responses are necessary to determine changing climate effects on tree growth

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Conclusion