Ecological theory predicts that the soil seed bank stabilizes the
composition of plant communities in the face of environmental
variability. Using one of the longest seed bank-vegetation databases, we
tested whether the composition of the seed bank is more stable than the
standing vegetation in annual communities across a rainfall gradient.
The composition of the seed bank differed from the vegetation throughout
the years with a higher abundance of small-seeded and persistent-seeded
species. Year-to-year variability in composition increased with
increasing aridity, but its magnitude was similar in the seed bank and
the vegetation. Importantly, the rate of long-term compositional change
was much slower in the seed bank. These results support the hypothesis
that the seed bank can buffer against climatic shifts and increases the
resistance of plant communities to directional trends. We conclude that
the seed bank plays a crucial role in the stability of plant communities
under global changes.