Data from: N₂-fixation is linked to the ability to encroach in African savanna trees

This dataset includes nitrogen (N) dynamics for 12 southern African
savanna tree species (six encroachers, six non-encroachers) under
manipulated atmospheric CO2 (~398 ppm ambient, ~545 ppm elevated) and soil
moisture (well-watered vs water-limited) in open-topped chambers. Measured
traits include nodule mass fraction, leaf and stem δ15N, and percentage of
N derived from N2-fixation (% Ndfa). The data capture both short- and
long-term N allocation strategies and enable exploration of how CO2 and
water treatments affect N dynamics across encroaching and non-encroaching
species.