Effects of hoarding activity of Apodemus mice on the regeneration and spreading of acorn-producing tree species.

为了阐明姬鼠囤积活动对橡子树种更新和传播的影响，本研究对姬鼠种群动态和囤积行为、美洲斑潜蝇(Pasania Edulis)的橡子产量及其从种子生产到育苗的死亡率进行了研究。大斑潜蝇和银纹伊蚊的数量每年都表现出相同的季节变化，春季种群数量最多，夏、秋季种群数量减少，晚秋以后种群数量增加。越冬期间驻留鼠的数量和果实产量的年变化并不总是一致的。每隔3~4年记录一次大果期，多数年份空果率低。姬鼠平均运输掉下的橡子10-50米，并将它们囤积在土壤中。运输的橡子所占的比例随野生孔等中型和大型哺乳动物捕食的强度而变化。大约60%的缓存橡子是被囤积者找回的，其中大约40%是被储藏者以外的老鼠偷走的。在这两种情况下，回收的橡子都被运到离母树更远的地方。编制了1995-2008年生产的橡子的生命表，并进行了关键因素分析。由姬鼠(K21)捕食掉下的橡子的强度决定了橡子从树上结实到育苗期间总死亡率的年变化(总K)。全K和K_(21)的密度关系与密度成反比。在这14年中，只有在1999年、2003年和2007年这3个主要年份，鼠类数量较少的情况下，姬鼠才能起到种子传播者的作用，对橡子树种的更新和传播做出贡献；在其余11年中，老鼠似乎扮演了种子捕食者的角色。

To clarify the effects of the hoarding activity of Apodemus mice on the regeneration and spreading of acorn-producing tree species, I studied the population dynamics and hoarding behavior of Apodemus mice, the acorn production of Pasania edulis, and its mortalities from acorn-production to seedling-establishment. A.speciosus and A.argenteus showed the same seasonal changes in their numbers every year ; the population was largest in spring, decreased during summer and fall, and then increased from late fall. The annual changes in the number of resident mice during winter and the acorn production of P.edulis did not always correspond. The masting of P.edulis acorns was recorded every 3-4 years, and in the mast years, the percentage of empty acorns was low. Apodemus mice transported dropped acorns 10-50m, on average, and hoarded them in the soil. The percentage of the transported acorns varied with the intensity of predation by middle- and large-sized mammals such as wild bores. About 60% of cached acorns were recovered by their hoarders and about 40% of them were stolen by mice other than the hoarders. In both cases, the recovered acorns were transported farther from their mother trees. I made the life tables of the acorns produced from 1995 to 2008, and conducted a key-factor analysis. The annual changes in the total mortality of acorns during the period from acorn-production on the trees to seedling-establishment (Total K) was determined by the intensity of the predation of dropped acorn by Apodemus mice (k21). The density relationships of Total K and k21 were inversely-density dependent. Out of the 14 years, Apodemus mice could act as seed-dispersers and contribute to the regeneration and spreading of acorn-producing tree species only in three mast years with a low mice population ; 1999, 2003, and 2007, and in the other 11 years, mice seemed to act as seed-predators.