Data from: Biomass partitioning in a future dry and CO2 enriched climate: shading aggravates drought effects in Scots pine but not European black pine seedlings

1. Climate change alters both water and CO2 availability for plants, but
it is largely unknown how they interact with light to affect tree seedling
establishment and early growth. Light availability is often regulated by
forest management, thus understanding how these resources co-limit the
regeneration success of tree species and populations with contrasting
drought tolerances is essential for adaptive forest management and
particularly for assisted migration. 2.We studied biomass partitioning of
3-year-old Scots pine (Pinus sylvestris) and European black pine (Pinus
nigra) seedlings in response to combined effects of light (22% and 40%
shade), soil water availability (moist and dry conditions) and CO2
(ambient and elevated), and examined the responses of seedlings from
Central Alpine and Mediterranean origin. Seedlings of nine populations
with varying drought tolerances were grown in a common garden in the
European Central Alps. Shoot height, vertical root length, shoot and root
biomass of the plants were assessed at the end of the third growing
season. 3. Under 40% shade and dry conditions, P. sylvestris seedlings
severely reduced shoot biomass, resulting in an increased specific shoot
height (SSH) compared to seedlings under 22% shade and moist conditions.
In contrast, P. nigra seedlings retained a constant shoot biomass under
all treatment combinations. Seedlings from drier origin were generally
larger, heavier, and had longer vertical roots than those from wetter
locations. In order to keep up shoot height, seedlings from wetter origins
disproportionately increased SSH under shaded conditions compared to
populations from drier origin. 4. Synthesis and applications. Under high
light availability, Scots pine (Pinus sylvestris) and European black pine
(Pinus nigra) seedlings were well adapted to dry conditions. Moderate
shading, however, substantially reduced Scots pine but not black pine
growth, and potentially amplified the vulnerability of Scots pine
seedlings to drought. Optimizing light conditions in forests, e.g. by
thinning, may thus enhance early Scots pine regeneration in a drier future
climate.27-Nov-2018