The Mechanism and Function of Tree Root in the Process of Forest Procution V. Reduction of Inorganic Matters to Soil and Formation of Porosity Resulting from Root System

1990

S. 1-49

8 Abb., 16 Tab.

Unselbständiges Werk

200062309

Bulletin of the Forestry and Forest Products Research Institute 1990 ; (357), S. 1-49

The rotting of roots after the cutting or dying of trees is an important process that forms porosity in the soil and supplies organic or inorganic matters to the soil. These matters or porosity have physico-chemical influences on forest soils, which are helpful to forest reproduction. The root biomass per ha of dominant and codominant trees at each stand age and the amount per ha of porosity and inorganic matters were estimated for different stand ages of C. japonica, Ch. obtusa, P. densiflora and L. leptolepis. When the trees were cut down at a stand age of 40 years in the second site class forest of yield table, the root biomass per ha left in the soil was 67 tons for C. japonica, 45 tons for Ch. obtusa, 47 tons for P. densiflora, and 37 tons for L. leptolepis. The total amount per ha of inorganic matters restored to the soil was as follows: Nitrogen-71 kg for C. japonica, 80 kg for Ch. obtusa, 35 kg for P. densiflora, and 39 kg for L. leptolepis; and Phosphorus-13 kg for C. japonica and Ch. obtusa, 10 kg for P. densiflora and 8 kg for L. leptolepis; Potassium-88 kg for C. japonica, 74 kg for Ch. obtusa, 68 kg for P. densiflora, and 36 kg for L. leptolepis; and Calcium-250 kg for C. japonica, 70 kg for Ch. obtusa, 103 kg for P. densiflora, and 31 kg for L. leptolepis. The amount per ha of porosity estimated from the root volume was 161 m3 for C. japonica, 93 m3 for Ch. obtusa, 110 m3 for P. denisflora, and 88 m3 for L. leptolepis. The root biomass, the amount of porosity, and the amount of inorganic matters considerably varied with species. The difference in the amount of inorganic matters was largely due to the difference in stand volume. The distribution of the root biomass and the amount of porosity in the soil is dependent upon how thick are the roots, such as stock, very large roots or large roots which occupy a greater part of the root biomass. The ratios of root distribution within the upper horizon 30 cm deep were, to the total amount of root biomass, 80 % for C. japonica and L. leptolepis, 89 % for Ch. obtusa and 68 % for P. densiflora. All the species except P. densiflora showed the high ratios of over 80 % in the upper horizon. P. densiflora grows its tap roots into deep soil and therefore has a comparatively high ratio in the lower soil horizon. The reduction ratios of matters in the 40 years-old stands of each species were estimated from both data of dry matters and inorganic matters in the above- and under-ground parts. The ratios for dry matter were 68 % for C. japonica, 75 % for Ch. obtusa, 69 % for P. densiflora, and 67 % for L. leptolepis.