Studies on the Gross Metabolism in a Sasa paniculata Type Grassland : II. The Physiological Response to Environmental Factors

Abstract

To elucidate the physiological response to environmental factors seasonal changes of productive structure of a Sasa paniculata type grassland in Kamishihoro were investigated from July to October in 1970, using the stratified-clip method. The results obtained in this study are summarized as follows: 1. When the leaf-area grows up according to the logistic equation (1), vertical accumulation of leaf-area in a plant community are expressed as the equation (2). Therefore, the light interception in the foliage is given by the general dynamic equation (4). 2. Light interception at the maximum growing-point of leaf-area is given by the equation (7). 3. In the case of this Sasa type grassland, at the maximum growing-point of leaf-area the relative light intensity through a leaf plane ranged from 45.4% to 24.9% and hence the amount of light interception by the Sasa leaves ranged from 54.5% to 75.1%. Therefore, about 55% of the illumination above the canopy is required by Sasa paniculata in order to maintain its growth. 4. The most of nutrient elements, which plants are able to absorb, are supplied by L, F, H and A_0 layers and thread roots develop into the direction of the higher contents of nutrient elements 5. The most major elements of available state were included in surface soil, while minor elements were supplied by both surface and deep soils. 6. Crude protein and ash contents in leaves and thread roots were higher than those in stems, rhizomes and roots, and crude fiber and NFE in stems were higher than those in leaves, rhizomes, roots and thread roots, while crude fat in leaves was the highest of all above- and under-ground parts. 7. Crude protein in rhizomes, roots and thread roots, crude fat in leaves, rhizomes, roots and thread roots, crude fiber in leaves and stems, NFE in rhizomes, roots and thread roots, and crude ash in leaves, rhizomes, roots and thread roots increased throughout the growing season but crude protein in leaves and stems, crude fat in stems, crude fiber in rhizomes, NFE in leaves and stems, and crude ash in stems decreased respectively. 8. The pattern of seasonal changes of major element contents in each organs differed from one another, especially in the case of N in leaves, P in rhizomes, K in stems and Mg in rhizomes. 9. The contents of Na, Fe, Mn, Zn, Cu, Co and Ni in thread roots were the highest , of those in above- and under-ground parts and fluctuation of their seasonal contents was remarkable, 10. The season peak of standing crops in dry weight of leaves, stems, live above-ground parts, total above-ground parts, rhizomes, roots, thread roots, total roots, live under-ground parts, total under-ground parts, total live parts and total were 609.0, 1,738.8, 2,347.8, 2,895.2, 1,771.0, 475.5, 1,175.6, 1,641.8, 3,307.8, 3,711.3, 5,665.6 and 6,363.9g/m^2 respectively. These seasonal peaks of thread roots, total roots and total under-ground parts were observed in October and the other organs were shown in September. 11. The productive structure of the Sasa type grassland in Kamishihoro was presented in Fig. 10 and the pattern of its seasonal change was compared with one another.