Characteristics of soil seed banks and their influencing factors in Ephedra rhytidosperma communities at different altitudes on the eastern foothills of Helan Mountain, China.

Abstract

Ephedra rhytidosperma is a national key protected plant species in the eastern foothills of the Helan Mountains. We established sample plots in E. rhytidosperma communities at altitudes of 1236, 1350, 1477, and 1603 m. Through field surveys and indoor seed bank germination experiments, we investigated the characteristics of soil seed banks in E. rhytidosperma community across different altitudes and their influencing factors. The results showed that in the soil seed banks across four altitudes, a total of 13 plant species germinated, belonging to 12 genera and 7 families. Species from Amaranthaceae and Poaceae were predominant, with annual herbs constituting the primary life form. The Margalef richness and Shannon diversity index were lowest in the 1477 m plot and highest in the 1603 m plot. The average density of soil seed bank ranged from 1713 to 9127 seeds·m^-2, showing a pattern of initial increase followed by decrease with increasing altitude. Soil seed bank density at 1350 m and 1477 m plots were significantly higher than those at 1236 m and 1603 m plots. Most seeds were distributed in the litter layer and the 0-5 cm soil layer, with soil seed bank density progressively decreasing with increasing soil depth. The similarity between soil seed bank and the aboveground vegetation in species composition was low. Redundancy analysis revealed that aboveground vegetation richness index and dominance index were key vegetation factors affecting soil seed bank, with explained variance percentages of 19.5% and 28.4%, and contribution rates of 24.6% and 35.9%, respectively. Soil bulk density was the significant soil factor affecting soil seed bank, but exhibited a relatively low explanatory rate (8.9%) and with a contribution rate of 11.3%. In conclusion, the mid-altitude suitable habitats (1350 m and 1477 m) exhibited higher regeneration potential of soil seed bank, enabling natural restoration via seed bank. However, marginal altitude non-suitable habitats (1236 m and 1603 m) required interventions (enclosure and reseeding) to enhance seed bank species richness and seed reserves, promote positive community succession, and thereby strengthen ecosystem stability and resilience.