Data: Large old trees increase growth under shifting climatic constraints: Aligning tree longevity and individual growth dynamics in primary mountain spruce forests

In a world of accelerating changes in environmental conditions driving
tree growth, tradeoffs between tree growth rate and longevity could
curtail the abundance of large, old trees (LOTs), with potentially dire
consequences for biodiversity and carbon storage. However, the influence
of tree-level tradeoffs on forest structure at landscape scales will also
depend on disturbances, which shape tree size and age distribution, and on
whether LOTs can benefit from improved growing conditions due to climate
warming. We analyzed temporal and spatial variation in radial growth
patterns from ~5000 Norway spruce (Picea abies (L.) H. Karst) live and
dead trees from the Western Carpathian primary spruce forest stands. We
applied mixed-linear modeling to quantify the importance of LOT growth
histories and stand dynamics (i.e. competition and disturbance factors) on
lifespan. Finally, we assessed regional synchronization in radial growth
variability over the 20th century, and modelled the effects of stand
dynamics and climate on LOTs recent growth trends. Tree age varied
considerably among forest stands, implying an important role of
disturbance as an age constraint. Slow juvenile growth and longer period
of suppressed growth prolonged tree lifespan, while increasing disturbance
severity and shorter time since last disturbance decreased it. The highest
age was not achieved only by trees with continuous slow growth, but those
with slow juvenile growth followed by subsequent growth releases. Growth
trend analysis demonstrated an increase in absolute growth rates in
response to climate warming, with late summer temperatures driving the
recent growth trend. Contrary to our expectation that LOTs would
eventually exhibit declining growth rates, the oldest LOTs (>400
years) continuously increase growth throughout their lives, indicating a
high phenotypic plasticity of LOTs for increasing biomass, and a strong
carbon sink role of primary spruce forests under rising temperatures,
intensifying droughts, and increasing bark beetle outbreaks.