2.2 Field survey
Twelve 10 m × 10 m study plots were established at 200-m elevational intervals from 1800 m to 2800 m, extending from the east to the west of the Yatsugatake Mountains. The plants in each plot were identified based on the taxonomic groups: trees, shrubs, herbs, ferns, and bryophytes. Ferns and bryophytes included both epiphytic and terrestrial species. Epiphytic species were recorded up to 2.0 m from the ground.
To examine the influence of climate on plant diversity, temperature and relative humidity (RH) were measured in each plot at ~5 cm above the ground at 4-h intervals throughout the year, obtained using HOBO U23 Pro v2 temperature/relative humidity data loggers (Onset Computer Corporation, Bourne, MA, USA). To reduce the influence of sunlight on the measurements, the data loggers were covered by a CO-RS1 solar radiation shield (Onset Computer Corporation). Based on the measurements of temperature and RH, the following climatic variables were calculated: mean annual temperature (Tempann), mean temperature during the growing season (Tempgrow), mean temperature during the snow season (Tempsnow), mean annual RH (RHann), mean RH during the growing season (RHgrow), mean RH during the snow season (RHsnow), and the duration of the snow season (snow cover). The series of snow-cover days with over 90% RH was defined as the snow season. This definition was based on a primary experiment that buried the data loggers under a snow pack. The remaining days were defined as the growing season.