Abstract
On the basis of the theoretical equations on plant growth which were derived by THORNLEY by dividing respiration into two components, growth and maintenance, a new theoretical equation for the density effect of plant growth is firstly presented here, and its advantage over the famous reciprocal equation of the logistic theory of the C-D effect is discussed. In order to consider the characteristics of the two parameters, maintenance respiration rate (m) and conversion efficiency of growth (YG), a few equations were derived theoretically for tree growth. The estimation of the values of m, YG and m•YG, was carried out by applying published data of the productivity of Cryptomeria japonica plantations, that of the yield tables and that of the stem analysis to the corresponding equations. As a result, it was revealed that m and YG could be regarded as nearly constant even though the growth periods were much longer, and the YG-value of 0.38 was about a half and the m-value roughly about a hundredth compared with crops. Even though the estimation was made with such different types of data, the m•YG-values were in agreement with each other. It was possible to estimate, approximately at least, the annual rates of gross photosynthesis and respiration of stands and individual trees by using the data of yield tables and of the stem analysis.
