Latitudinal diversity gradients of soil seed bank and aboveground vegetation in China

The latitudinal diversity gradient is one of the most general biogeographical patterns. However, current latitudinal diversity gradients have been mostly focused on aboveground vegetation, while such a pattern exists in soil seed bank, which is an irreplaceable natural resource that provides multifaceted benefits to terrestrial biodiversity, is not well understood. Here, we compiled plant diversity data of soil seed bank and corresponding aboveground vegetation from 496 sample sites in China, to detect whether the latitudinal diversity gradient of soil seed bank differs from that of aboveground vegetation. We found that soil seed bank exhibited a significant but weaker latitudinal diversity gradient compared to aboveground vegetation, and the latitudinal diversity gradient of soil seed bank was not observed for ecosystems dominated by herbaceous plants. In contrast to increasing species diversity of aboveground vegetation towards the tropics, species diversity in soil seed bank remained stable across the latitudinal gradient for grasslands and wetlands. Moreover, environmental factors associated with species diversity of soil seed bank and aboveground vegetation were different, with mean temperature and temperature range as the major driver of species diversity in soil seed bank while elevation and temperature seasonality as the major drivers of aboveground vegetation species diversity. Our results provide empirical evidence that biogeographic pattern of plant diversity generated from aboveground biota do not necessarily reflect that of belowground diversity, and aboveground-focused conservation may fail to protect plant diversity stored in soil seed bank.