草地の状態診断に関する研究 I : 生活型組成による診断

抄録

The conditions of grassland must be examined from two viewpoints, biological and economical. The former is the standpoint of pure science and the latter is that of applied science. The judgement of grassland condition required for the production of meat and milk is zootechnical and economical, but the basis of such a judgement must be biological or ecological. Here the author will propose several criteria of judging the grassland trend and condition ecologically basing on his years' field survey of Japanese semi-natural grasslamds for grazing and mowing use. The ecological judgement of semi-natural grasslands in the forest-climax area like Japan will be equal to the judgement of the progression of plant succession. As one of succession-judgements, the judging method of grassland condition by the biological spectra is firstly proposed. The biological spectra are expressed by the combination of the RAUNKIAER'S dormancy forms, the NUMATA'S migrule forms (disseminule forms D_<1-5> and radicoid forms R_<1-5>) and the NUMATA'S growth forms modifying the GIMINGHAM'S system. The growth forms consist of t, b, e, r, pr, p, 1 and pseudorosette form (ps) as an intermediate type between r and e. Besides these, the spiny or thorny form (sp) will be noticed. The biological spectra are examined according to the species percentage (Sp %) and the dominance percentage (SDR %). We can compare and discuss the biological spectra of short-grass or Zoysia type (Table 3, 4, 5), high-grass or Miscanthus type (Table 7, 8), Sasa-type (Table 9), bracken type (Table 10, 11) and annual type grasslands (Table 12). On the basis of such data, a diagnostic criteria of the grassland condition by the biological spectra is proposed (Table 13). A grassland type covers some wide range of conditions as a seral stage. The figures in the Table 13 indicate the typical or standard state of each grassland by most characteristic items. These judgement are done according to the species percentage and in practical use the difference between the species percentage and the dominance percentage must be discussed. The grassland trend will be estimated by comparing grassland types as seral stages.