The judgement of grass slopes conditions must be done ecologically, for grass slopes are to be constructed to improve the localities and the landscapes from the road.
The ecological judgement of grass slopes is equal to the judgement of the progression of succession. And succession must be judged from two viewpoints. One is from floristic composition and the other is from biological spectra.
Firstly, the author investigated the plant communities of the railwayside slopes at Chuosen line in Tokyo, which were constructed 80 years before, in order to be able to compare succession stages of the slopes, which were constructed 1.5, 3, and 5 years before. The table work after this survey shows 4 plant communities.(Table 1) 2 Miscanthus types, Imperata type, and Zoysia type.
Secondly, vegetation survey was practiced on the slopes (constructed 1.5, 3, and 5 years before), which were at first covered by imported species (Festuca arundinacea Schreber and Eragrostis curvula Nees) (Table 2, 3, 4) and native species (Zoysia japonica steud.).(Table 5) From these results the progression of succession was diagnosed.
The method by floristic composition was firstly proposed. The diagnoses were as follows:
1. The difference of the progression between the two method of construction, by imported species and by native species, could not be recognized clearly.
2. On the banking slopes the progression is faster than the cutting slopes.
3. Earlier, the cutting slopes were wetter, but after 5 years or so they became drier than the banking slopes.
Then the method by biological spectra was proposed.(Table 6) The biological spectra were expressed according to the RAUNKIAER'S dominancy forms and the species percentage (Sp%). The results were as same as the former's. I recognized the stable condition of grass slopes, when the Sp% of Th became under 20% and the number of species became over 20
