Short-term acute nitrogen deposition alters the interaction between Korean pine seeds and food hoarding rodents

Although the environmental impacts of nitrogen (N) deposition have been well studied, how nitrogen deposition affects the interaction between seeds and food hoarding animals has never been investigated. In this study, N was added twice as NH4NO3 to Korean pines Pinus koraiensis in order to explore the impacts of N deposition on seed traits and food-hoarding behaviors of small rodents in the northeastern deciduous forests in China. Pine cones were collected to measure seed traits and to test food-hoarding behaviors of small rodents both in the field and in semi-natural enclosures. Our results showed that short-term N addition significantly enhanced the ratio of seed meat to seed coats and the concentrations of crude protein. Moreover, seed volatile compounds were significantly altered by N addition, resulting in lower emission of α-pinene but higher emissions of D-limonene. Consequently, nitrogen addition increased seed scatter-hoarding by both Tamias sibiricus and Apodemus peninsulae in enclosures. Field experiments showed the consistent results that small rodents preferred to scatter-hoard seeds with N addition over the control. To our knowledge, this is the first study showing that nitrogen deposition shapes the interaction between seeds and food-hoarding animals through altering the physical and chemical traits of seeds.