Daugavietis, M., Bisenieks, J. and Daugaviete, M. 2011. Interrelations among Grey Alder Stand Characteristics.  Baltic Forestry 17 (1): 68 – 75

The purpose of the study is to determine the interrelations of the assessment characteristics necessary for modelling the yield of grey alder stands. The models serve as a theoretical base that allows developing recommendations for forest cultivation technologies in line with the forest cultivation goals. The growth and yield tables for three site indexes, which have been used in forest management until now, do not encompass the whole variety of grey alder stands, so possibilities of expanding the tables are being looked for by introducing additional site indexes by means of extrapolation.
A new mathematical model for determination of grey alder site index has been developed on the basis of data obtained from stem analysis of sample tree trunks, which can be used to calculate curves of growth of the average height up to age 40, and a new scale for determination of the site index has been recommended, where site index is denoted as the average height of the stand in metres at age 20. The method of multiple regression has been used for interpretation of interrelations of stand assessment characteristics. The regression models incorporate three independent variables selected by way of logical analysis. The calculation of the regression coefficients uses data obtained from a one-time survey of 150 sample plots. A description of the sample plots is provided. Formulas of I. Liepa have been used for calculation of stem volume and current increment of the reduced volume of the stand. Mathematical models of the interrelations of stand assessment characteristics have been developed, which can be used to determine the following stand yield characteristics: average diameter, basal area, volume, the reduced actual volume increment and the current annual height increment.
It has been demonstrated that grey alder stands up to age 40 maintain a high yield and large annual current volume increment, which is higher than the average volume increment.
In the models, one of the main independent variables that can be regulated with forest management is the number of trees, and the models allow predicting the effect of thinning on the wood yield.

Key words: grey alder, site index, volume, the reduced current volume increment, current increment of average height, current increment of average diameter at breast height