A dynamic model of the daily height increment of plants

During recent decades much attention has Growth also depends on the internal state of been focused on the daily growth increment of the plant, which is, as a rule, described by time (t). plants, and the questions involved have been Accordingly, we arrive at the growth model (see analysed from many standpoints. But whilst the e.g. Kangas 1968: 42 43, Jonsson 1969: development of automatic data processing has 97 122) made it possible to deal with even the most comdv plicated interactions of several growth factors (i) — = g (x, t) operating simultaneously, the models for growth used so far have remained static (Whaley 1961, But the model defined by eq. (1) is unsatisfac Kozlowski 1964, Lyr et al. 1967). Either the tory, because the growth capacity of a plant is constantly changing nature of the innate growth usually not indicated well enough by time t tendency of plants has been ignored or its imalone. plications have been evaded in one way or The rate of biological maturation (M) is also another (Mork 1941, Wielgolaski 1966), or affected essentially by external conditions, or, else the analysis has been based on preconceived to be more precise, M = M (X). With the aid of formulae or pattern curves (Godske 1961). the rate of maturation M, we now introduce a The purpose of this paper is to present a new concept, the physiological age (s), by the dynamic approach to the analysis of the daily following equation: height increment of plants. Trees have been t used as an example, but the method is equally r applicable to other higher plants. Preliminary (2) = J M(X(r)) dr features of the model have been published else° where, with long-term diameter growth of tree We then suppose that growth depends on the stands as a practical example (Hari 1968). physiological age (s) as well as on the environ mental conditions X. Hence: