Marino HIRAOKA, Takashi GOMI and Yoshimi UCHIYAMA
Abstract
To evaluate seasonal changes in forest floor cover percentageiFCP; total percent cover of understory vegetation and litterj, we continuously observed daily variation in forest floor cover on steep hillslopes in two catchments using automatic interval cameras. FCP values in six ODT x ODT]m plots varied in their response to meteorological factors, such as precipitation and air temperature. The cover percentage of understory vegetation in the plots decreased from UT to PR and from TS to P following decreases in daily air temperature during the fall and early winter, respectively. Seasonal variation in the cover percentage of litter was associated not only with precipitation during typhoon events and decline in daily air temperature but also with the species of overstory trees. Under mixtures of broad]leaved trees and Cryptomeria japonica, the cover percentage of litter increased from RT to WV together with a decrease in understory vegetation. Under broad]leaved canopies, the cover percentage of litter increased from QV to US as the daily air temperature declined after November. When daily air temperature fluctuated aroundO after mid]December, surface soil creep occurred from freezing and thawing in plots with sparse litter cover. Continuous observation using interval cameras allowed us to evaluate not only seasonal variation but also dynamic alteration of forest floor cover. Our approach could be used to examine the processes of soil erosion and sediment production on forested hillslopes, based on critical conditions for forest floor cover and air temperature combined with monitoring of surface soil movement.
Key wordsFseasonal change, forest floor cover, understory vegetation, litter, interval camera