Structure of the diameter of different ages overgrowth beech stands Ukrainian Carpathian

Abstract

Forest structure studies are of a great importance for the development of
forest inventory regulations.
Analysis of data revealed the difference in the structure of European beech
Fagus sylvatica L. overmature stands. Based on the stem volume of younger
generations, analyzed stands can be divided into types: i) even-aged – without
clearly distinct second storey; ii) relatively even-aged – with the 10% of volume
share of younger generations; iii) uneven-aged – with more than 10% of volume
share of younger generations.
Research data consists of tree stands from all three types (33%, 36% and
32% of the total tree stands amount respectively). During the cruising of
uneven-aged stands, average diameters may vary considerably, e.g., the
average diameter of tree stand is 36 cm, while for the first storey it is 48 cm,
and for the second – 12 cm.
The statistical analyses of our research data accompanied with the results
of previous researches in this field of study (O.A. Hirs) showed that the most
accurate results are obtained using β-distribution.
It was found that overmature beech stands of the Carpathian region are
characterized with two-storyed structure and presence of younger trees.
Structure indices of both first and second storeys, as well as overall combined
stand structure indices are characterized with different parameters.
Skewness and kurtosis indices decrease after the storeydifferentiation in the
stand structure. Yes, skewness of overall combined stands varies from -0,28 to
+2,93 (in average +0,47), while skewness of the first storey varies from -0,25 to
+1,91 (in average +0,46); kurtosis of overall combined stands varies from -1,29
to +9,35 (in average +0,37), while kurtosis of the first storey varies from -1,29 to
+6,54 (in average -0,16).
Analyzes of research data showed that second storey with the 10% volume
share is present in overmature stands with average diameter from 20 to 44 cm. In the range of average diameter from 48 to 68 cm second storey has 1-6% of
total stand volume.
Mathematical modelling was conductedseparately for different storeys and
whole stand. It was used in order to retrieve data needed for further creation of
diameter distribution tables. Such indices as variability, minimal and maximal
reduction numbers, share of merchantable stems were modeled based on
average diameter of the stand. Correlation indices between diameter variability
of merchantable and overall stems were modeled based on the share of
merchantable trees in the stand.
Both diameter distribution of the whole stand and diameter distribution of the
second storey were calculated using program developed by the Department of
Forest Inventory and Forest Management of National University of Life and
Environmental Sciences of Ukraine.
Dependence of second storey average diameter from average diameter of
the whole stand was revealed on the basis of correlation coefficients between
diameter distributions of the first and second storey. Besides that, mathematical
model of second storey stem volume dependence from the overall combined
stand average diameter was also created. Diameter distribution of each
storeywas calculated using conversion coefficients and age class distribution
data.
Overmature beech tree stands, stand inventory within different
storeys, age classes of tree stands.