关键词: 种子大小, 子叶取食, 负密度依赖性, 幼苗建植, 六盘山区

Abstract: Cotyledon is the basic nutrition source at seed germination and seedling establishment of Quercusspecies. In this study, a field survey was conducted to investigate the cotyledon loss dynamics of Quercus wutaishanica seedlings germinated from large and small seeds under the predation pressure of herbivorous animals and different density treatments (0.25, 0.75, 1.50, 2.25, and 4.00 ind·m^-2) and its effects on seedling survival and growth inLarix principis rupprechtiiforest of Liupan Mountains. The results showed that final cotyledon retention rates (FCRRs) and survival rates (SRs) of seedlings were higher under lower density and lower under higher density in both large and small seeded seedlings, indicating a negative conspecific density-dependence. Seedlings germinated from large seeds had higher survival rates than those from small seeds under all density treatments. Regardless of whether cotyledons were lost or not, large-seeded seedlings had greater basal stem diameter, taproot length, leaf number, leaf area per plant (LAPP), and total dry weight (TDW) than small-seeded ones. The LAPP and TDW of smallseeded seedlings with cotyledons loss were lower than those of cotyledon-intact seedlings. Both root-shoot ratio (RSR) and specific leaf area (SLA) were higher in large-seeded seedlings than in small-seeded seedlings, while specific root length (SRL) and specific shoot length (SSL) were lower in large-seeded seedlings. A slight decrease was found in RSR of cotyledons-lost seedlings, while increases with different degrees were detected in SLA, SRL, and SSL. In summary, the FCRRs and SRs of Q. wutaishanicaseedlings established from both large and small seeds showed a negative density-dependence. There were higher SR and growth advantage in large-seeded seedlings than in small-seeded seedlings. Cotyledon loss affected seedling survival and growth. Seedlings of Q. wutaishanica could adapt to the difference of nutrition storage in different sized seeds and compensate the negative effect of cotyledon loss on seedling survival and growth by regulating their morphological plasticities. Our results could provide scientific basis for the practice of seedling regeneration of degenerated secondary forest and seeding afforestation of Q. wutaishanica in Liupan Mountains.

Key words: seed size, cotyledon predation, negative density dependence, seedling establishment, Liupan Mountains.