抄録
The impact of forest thinning operations on surface soil physical properties was investigated under varying forest conditions. Five forest conditions were delineated into natural broadleaved forest, Japanese cedar (Sugi) and Japanese cypress (Hinoki) plantations with and without thinning operations. Ordination analysis by principal component method of the different soil physical characteristics extracted two main components regarded as water holding factor (WHF) and water movement factor (WMF). The extracted principal component (PC) values were used as dependent variables to analyze the effects of forest species and forest operations. The results showed that both means of WHF and WMF were high in natural broadleaved forest and coniferous forest plantations with operations, and low in coniferous forests plantations without operations. Overall, the highest means of WHF were found in plantations occupied by cedar with operations comparable to natural broadleaved species. Moreover, the highest means of WMF were found in cypress plantations with operations and in broadleaved species whereas cedar and cypress plantation forests without operations showed the lowest values. These results suggest that the thinning operations indirectly contribute to improve surface soil physical properties of coniferous forest plantations.
