Data for: Growing faster, longer or both? Modelling plastic response of Juniperus communis growth phenology to climate change

Aim: Plant growth and phenology plastically respond to changing climatic conditions both in space and time. Species-specific levels of growth plasticity determine biogeographical patterns and the adaptive capacity of species to climate change. However, a direct assessment of spatial and temporal variability in radial-growth dynamics is complicated, as long records of cambial phenology do not exist.

Location: 16 sites across European distribution margins of Juniperus communis L. (the Mediterranean, the Arctic, the Alps and the Urals).

Time period: 1940-2016

Major taxa studied: Juniperus communis

Methods: We applied the Vaganov-Shashkin process-based model of wood formation to estimate trends in growing season duration and growth kinetics since 1940. We assumed that J. communis would exhibit spatially and temporally variable growth patterns reflecting local climatic conditions.

Results: Our simulations indicate regional differences in growth dynamics and plastic responses to climate warming. Mean growing season duration is the longest at Mediterranean sites and, recently, there is a significant trend towards its extension of up to 0.44 days per year. However, this stimulating effect of longer growing season is counteracted by declining summer growth rates caused by amplified drought stress. Consequently, overall trends in simulated ring-widths are marginal in the Mediterranean. By contrast, durations of growing seasons in the Arctic show lower and mostly non-significant trends. However, spring and summer growth rates follow increasing temperatures, leading to a growth increase of up to 0.32 % per year.

Main conclusions: This study highlights the plasticity in growth phenology of widely distributed shrubs to climate warming–an earlier onset of cambial activity that offsets the negative effects of summer droughts in the Mediterranean and, conversely, an intensification of growth rates during the short growing seasons in the Arctic. Such plastic growth responsiveness allows woody plants to adapt to the local pace of climate change.

Methods
This data package contains (i) input ring-width series of Juniperus communis used to calibrate the Vaganov-Shashkin model and (ii) outputs of the model important for the interpretations made in the above-referenced paper.

(i) were obtained using standard dendrochronological procedures (including field sampling, laboratory processing and ring-width measurement). Individual datasets are stored in RWL format which might be uploaded by most of dendrochronological softwares. Data represent annual ring widths of J. communis shrubs. If multiple discs/radii were measured at specific site, they were averaged into the shrub level. One RWL file is provided for each site of the network.

(ii) represent outputs of the Vaganov-Shashkin models' simulations applied on each site of the network.

For detailed description of each dataset, please, see enclosed ###README.txt file.