Regeneration dynamics of Euptelea pleiospermum along latitudinal and altitudinal gradients: Trade-offs between seedling and sprout

Abstract

Poleward and upward range shifts are important strategies for range-restricted tree species in the face of climate warming, but empirical studies of both latitudinal and altitudinal shifts are scarce. We investigated regeneration dynamics of an endemic Tertiary-relict tree (Euptelea pleiospermum) along (i) a latitudinal gradient across its range in China and (ii) altitudinal gradients along three mountains at low, middle and high latitudes. Sprouting ratio and relative seedling density present contrasting latitudinal patterns, with more seedlings at the leading edges and more sprouts at the trailing edges. We detected no apparent shift, a downslope shift and an upward shift along mountains located at low, middle and high latitudes, respectively. Sprouting ratio and relative seedling density also show contrasting altitudinal patterns. Our results suggested (i) northward migration along the latitudinal gradient and (ii) disparity in altitudinal shifts of the same tree species along different mountains. Furthermore, we emphasize that sprouting is an important strategy for sprouting tree species to buffer range contraction at the trailing edges in the face of climate warming.