Experimental research on vegetation response to artificial warming on a mid-latitude high mountain, Central Japan

Abstract

In order to investigate the vegetation response to global warming, experimental research was carried out on a high mountain of Japan for three years from 1997 to 1999. The experimental site was in the alpine zone at 2,780 m above sea level, near the peak of Mt. Norikura (3,026 m) in central Japan. Vegetation growing period is about 4 months without snow cover from early June to early October. Five open top chambers with a diameter of 80 cm and a height of 30 cm were used for temperature enhancement, and another five places were selected as controls outside the chambers. The main objectives were to clarify the differences in vegetation growth, phenology, biomass and coverage of plant between temperature-enhanced chambers and controls. To prove temperature enhancement, air temperature at vegetation height of 5 cm high above ground and ground temperature at root layer of 3 cm depth were recorded every hour in each chamber and at each control. Vegetation growth and phenology of several alpine species were measured at about four-week intervals, and biomass and coverage were measured on the last experimental day every year. The mean air temperature at vegetation height and mean ground temperature at root layer in chambers were about 0.65°C and 0.25°C higher than in the controls, respectively. Vegetation growth was significantly accelerated, and phenology was surely affected by the extension of growth period due to temperature enhancement for most of the plants observed. Vegetation growth and phenology, however, varied with species, indicating that species vary in response to warming. Differences in biomass between chambers and controls were not significant for all years, suggesting that the total growth of plants in the unit area is controlled by nutrient conditions of the soil. Through three years of experiment, coverage of Loiseleuria procumbens (Ericaceae) recognizably increased, overcoming other species in chambers, while there were no conspicuous changes in controls. It suggests that L. procumbens whose canopy expands horizontally over the other forbs might be more physiologically active than others under warming conditions, although vegetation growth showed positive response to temperature enhancement for most species.