Implications of seed germination ecology for conservation of Camptotheca acuminata, a rare, endemic, and endangered species in China

Abstract

Seed germination and seedling recruitment are among the most critical stages for plant population persistence and development, which may be influenced by habitat fragmentation and resulting microhabitat changes. We conducted laboratory and field experiments using seeds of Camptotheca acuminata, a rare, endemic, and endangered species in China, to investigate the effects of temperature change and water availability on seed viability and germination. The seeds were sensitive to high temperature and water stress. Germination percentages > 60% occurred only between 20–35 °C and water potentials > − 0.6 MPa. Heating at 75 °C and above for 30 min, continuous heating at 40 °C for 20 days, or desiccation following 120 h imbibition killed nearly all seeds. These seed traits made none of the five microhabitats investigated suitable for regeneration. In the understory plot, most seeds germinated, but the resultant seedlings survived only a short time, depending on reserve food supply from the seeds. Sensitivity to high temperature and water stress inhibited germination in the other plots and most seeds died in the hydration-dehydration cycles. We concluded that efficient natural regeneration could occur only in very special habitats: cool, with stable moist soil but ample sunlight, most likely in suitable gaps in continuous forests. In addition to habitat loss and over-exploitation, difficulties in natural seed germination and seedling recruitment are primary reasons for the current status of C. acuminata. For population recovery of C. acuminata, understory microhabitat protection and artificial support for germination and seedling recruitment are required.