Distribution patterns of the soil seed bank of Crataegus songarica K. Koch with altitude in the western Tianshan wild fruit forest

We studied the composition and spatial distribution characteristics of the soil seed bank and seedling renewal rate of the rare Crataegus songarica plant in the Western Tianshan Wild Fruit Forest in Xinjiang along the altitudinal gradient, combining field sampling, laboratory experiments, and data analysis. Results showed that: (1) Wormy seeds, solid seeds, and plump seeds accounted for 50.83%, 46.22%, and 2.95% of the total C. songarica soil seed bank, respectively. The number of plump seeds at each altitude was very low, but showed a fluctuating trend with altitude (first decreasing, then increasing, then decreasing again), reaching a maximum density of (2.36 ± 0.71) grains/m² at 1400–1500 m. (2) For vertical distribution of the soil seed bank, wormy seeds were dominant in each soil layer, followed by solid seeds, with the density of plump seeds significantly lower than both. The density of plump seeds did not differ significantly between soil layers. For horizontal distribution, the density of wormy seeds, solid seeds, and plump seeds in the soil seed bank showed a decreasing trend with increasing distance from the C. songarica mother plant, with 94% of plump seeds distributed within 3 m of the mother plant. (3) Seedlings were also distributed near the mother plant (within 2.5 m). There were few seedlings, and the number of seed seedlings was even less (< one strain/50 m²). The seedling conversion rate was only 5‰, dominated by emergent asexual reproduction supplemented with native sexual reproduction. In conclusion, C. songarica seed density was not significantly affected by the altitudinal gradient and seed renewal ability was poor under natural conditions. Thus, C. songarica seedling conversion and renewal could be promoted by regulating environmental factors and improving seed habitat.