TODA Hiroto Agriculture, Tokyo University of Agriculture and Technology Assistant professor, 農学部, 助手 (00237091)
ISHIBASHI Seiji Agriculture, Tokyo University of Agriculture and Technology Associate professors, 大学院・農学生命科学研究科, 助教授 (30212921)
KITAYAMA Shigeru Agriculture, Tokyo University of Agriculture and Technology Professor, 農学部, 教授 (10026502)
WU Jiling Nanjin Forest University Fac. Timber Technology Professor
HUANG Baolong Nanjin Forest University Fac. Resource and Environment Professor
呉 季陵 南京林業大学, 木材工学院, 教授
黄 宝龍 南京林業大学, 資源・環境学院, 教授
|Budget Amount *help
¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 2000 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1999 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1998 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Wetlands in China cover an area of approximately 63 millions ha, which ranks third in the world, and part of which has been exploited for forestry. The study area was located in Jangsu County, Jangus province, China. The study site of poplar and tax odium stands were divided into three groups respectively, a high, a middle, and a low water table site. The growth dynamics, biomass productivity, properties of soil, and characteristics of carbon and nitrogen mineralization in various study sites were studied. The principal results and conclusions are as follows.
1. Effects of the water table on the biomass and nutrient contents of stands.
A high water table seriously inhibited the growth in height, DBH, volume and biomass productivity of poplar and tax odium ; growth increased from lowest at the high water table site, to greatest at the low water table site. The biomass productivity of 10-year-old poplars situated in the high, middle, and lower water tables were 73, 162, 259 t/ha respectively. The biomass productivity of 17-year-old tax odium located in the high, middle, and low water tables were 56, 105, 163 t/ha, respectively.
2. Physical and chemical properties of soil in the forest wetland.
The air porosity of the soil decreased rapidly after the site was flooded. Exch, Ca, Mg and CEC was highest in the low water table and lowest in the high water table. A high water table caused a pH increase of 0.5 to 1.0 or more, but the organic matter content of the A0 horizon of the high water table site was higher than that of the lower water table site.
The amount of inorganic nitrogen decreased rapidly in 0-20 cm soil depth as water table height increased. The NO_3-N was particularly low in the high water table sites because of denitrification. In September, methane emissions would increase greatly when the soil is flooded.