執行成果摘要
Soil health index, like site quality or forest productivity, is one of the objectives of ecosystem management and is related to forest sustainable management. However, very litter information is available that relates soil health index to total net primary production of managed plantations in Taiwan. The goals of the project are to investigate the soil non-biological qualities of plantations basic on various species and areas to in order to analyze and select soil health index for sustainable management of plantations. To achieve to goal the Cryptomeria japonica plantations in northern Taiwan will be selected this year and investigated their tree growth and soil properties and tree growth. The relationship between tree growth and soil properties were analyzed in order to select possible soil health index of the Cryptomeria japonica plantation. For the Cryptomeria japonica plantations of Wulai working circle located at Tonghow area, 37 to 48 year-old and at an elevation of 490-700 m, the dbh and tree height of trees increased with age, but tree density decreased. The soil physical characteristics were the same with ages, but soil total carbon and nitrogen and available phosphorus decreased with age. The available phosphorus showed the largest descended percentage, which may cause phosphorus shortage in soil. The soil total carbon and nitrogen and available phosphorus of Cryptomeria japonica plantations of Taipingshan working circle were, however, no regularity. Soil total carbon and available phosphorus were extremely different among the stands. Soil characteristics showed no relationship with tree growth too, which indicated there were other factors influenced soil characteristics and tree growth. In conclusion, soil available phosphorus is regarded as soil health index in the Cryptomeria japonica plantations of Wulai working circle, but more data collection and analyses are needed to select soil health index of the plantation in other working circles.