Responses of alpine shrubs to simulated environmental change during three years in the mid-latitude mountain, northern Japan

Effects of artificial warming on phenology, individual leaf traits, vegetative growth, and reproduction of five alpine species (two deciduous and three evergreen shrubs) were investigated during three years in the mid-latitude alpine, northern Japan. Eleven open-top chambers (OTCs) were set up on a fellfield (1680 m a.s.l.) in the Taisetsu Mountains by which air temperature at plant height was increased by ca 2 degreesC. Vaccinium uliginosum (deciduous shrub) showed earlier leaf emergence in every season and earlier flowering only in the first season in the OTCs. By contrast, acceleration of leaf emergence in the OTCs was not clear for other species, i.e. Arctous alpinus (deciduous shrub), Ledum palustre, V. vitis-idaea, and Empetrum nigrum (evergreen shrub). Both deciduous species showed longer leaf life-span in the OTCs every season. All evergreen species had higher leaf survival rates in the OTCs, indicating extension of leaf life-span. Leaf nitrogen concentration and leaf mass per unit leaf area (mg cm(-2)) generally tended to decrease in the OTCs. Relationships between the individual leaf traits and cumulative air temperature during the leaf developing period were not clear. Total leaf production during the three seasons increased in the OTCs in A. alpinus, L. palustre, V. vitis-idaea, and E. nigrum. All evergreen shrubs showed larger shoot growth in the OTCs but both deciduous shrubs did not show significant changes. In contrast to the vegetative growth, deciduous shrubs produced more flowers in the OTCs. Fruit production was not influenced by the OTCs for all species. The extension of photosynthetic period in the OTCs may contribute to the larger vegetative growth or flower production.