P. Hari

A dynamic approach to the analysis of daily height growth of plants

A model for analysing the daily height increments of vascular plants is presented. Temperature plays a dual role in growth. It strongly affects the daily increments and it determines the rate of maturation. Therefore the concept of inherent growth rhythm had to be introduced into the model in order to obtain satisfactory agreement between computed and measured daily increments. The model which includes the effect of temperature and that of inherent growth rhythm was found to have quite a good predictive value when applied to independent material.

The inherent growth rhythm and its effect on the daily height increment of plants

A quantitative method for monitoring the effect of the inherent growth rhythm on growth throughout the whole growth period is presented. The method is applied to the analysis of daily height growth of several vascular plants representing a great variety of genetic variance. The basic pattern of growth seems to be similar irrespective of the plant species except for the timing, in which there is a pronounced variance. The timing of growth is a very important phenomen for adaptation.

A DYNAMIC MODEL FOR ABOVE-GROUND GROWTH AND DRY MATTER PRODUCTION IN A FOREST COMMUNITY

(1) A dynamic model for estimating the dry matter production rate of a plant community is described. The model is used to simulate the production rate of above-ground dry matter by trees and by the ground vegetation in a Scots pine (Pinus sylvestris) stand. Only formation of structural dry matter during the vegetative growth phase is considered. (2) The model assumes that growth and production rates are affected by environmental factors, but they are also dependent upon the internal state of the plant. Temperature is the only environmental factor considered. The physiological stage of development of the plant during the annual cycle is estimated as a function of temperature. Its effect on growth rate is brought into the model by means of inherent growth rhythm. (3) The concept of potential production rate, PPR, is introduced. It combines the effect of the inherent growth rhythm, number of growing compartments and the amount of available carbohydrates on the growth rate into one variable. The actual production rate of the community is obtained by multiplying PPR by the temperature factor. (4) Strong correlation was found between measured and modelled values for daily growth and production.