Frequency-dependent seedling predation by rodents: growth and survival of Quercus wutaishanica in two habitats

Abstract

Abstract Rodents attack oak (Quercus wutaishanica) seeds based on their sizes and frequencies before germination. However, the predation of oak seeds post-germination (seedling cotyledons) is not well studied. Here, we not only tested the preference of rodents for Q. wutaishanica seedling cotyledons based on the frequency of large- versus small-seeded (FLS), but also evaluated the effects of predation on seedlings growth and survival in different habitats. We transplanted seedlings with the FLS set as 9:1, 7:3, 5:5, 3:7 and 1:9, respectively, in the forest gap and under the canopy in the Liupan Mountains National Nature Reserve in Ningxia Hui Autonomous Region, Northwest China. The results showed that: (i) in 1–7 days after transplanting seedlings, rodents prefer the cotyledon of large-seeded seedings while small-seeded seedlings were preferred in 8–60 days, and the positive frequency-dependent predation was observed. (ii) The cotyledons were preyed on, the apical buds were bitted off, and the whole seedlings were uprooted, which mostly occurred under the forest canopy. At the end of a growing season, the survival rate of seedlings in the forest gaps was more than twice that under forest canopies. (iii) If cotyledons were preyed on, the growth of Q. wutaishanica seedlings would not be affected, but the seedlings growth was severely inhibited when the apical bud was bitten off. These results not only provide new insights into the coexistence between rodents and seedlings of different phenotypes, but also reveal the ecological characteristics of deciduous Quercus regeneration.