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Zoltán Kern and Ionel Popa

Abstract

A set of subfossil macroremains, consisting of 118 oak (Quercus sp.) and 61 elm (Ulmus sp.) trees, was collected at five sites in the foothills of the Eastern Carpathians along the course of the Suceava river. The tree-ring widths of the subfossil samples were measured. Dendrochronological synchronization resulted in five oak chronologies, although each encompassed relatively few (2 to 4) reliably cross-dated series. Radiocarbon analysis was performed on samples from three of the floating chronologies and on an additional single oak sample. Double radiocarbon data from two of the floating chronologies allowed for improved calibration using the wiggle-match estimate of the subfossil oak remains. Radiocarbon evidence highlighted the fact that the subfossil material recovered from the fluvial deposits of the Suceava river may represent a substantial part of the Holocene, from ~700 to ~7000 years ago. When temporal distribution of 14C dated sequences from the Suceava black oaks were compared to the calibrated age ranges reported from nearby rivers (Siret, Moldova), deposition events were observed to coincide at around 0.8–0.9 ka cal BP and ~3.7–3.6 ka cal BP. The five presented floating chronologies, and especially the first 14C wiggle-matched tree-ring sequences of Ro-manian black oaks could become key building blocks in a longer regional oak tree-ring chronology for the Eastern Carpathian region.

Open access

Rudolf Petráš, Michal Bošeľa, Julian Mecko, Julius Oszlányi and Ionel Popa

Abstract

Height-diameter models define the general relationship between the tree height and diameter at each growth stage of the forest stand. This paper presents generalized height-diameter models for mixed-species forest stands consisting of Norway spruce (Picea abies Karst.), Silver fir (Abies alba L.), and European beech (Fagus sylvatica L.) from Slovakia. The models were derived using two growth functions from the exponential family: the two-parameter Michailoff and three-parameter Korf functions. Generalized height-diameter functions must normally be constrained to pass through the mean stand diameter and height, and then the final growth model has only one or two parameters to be estimated. These “free” parameters are then expressed over the quadratic mean diameter, height and stand age and the final mathematical form of the model is obtained. The study material included 50 long-term experimental plots located in the Western Carpathians. The plots were established 40-50 years ago and have been repeatedly measured at 5 to 10-year intervals. The dataset includes 7,950 height measurements of spruce, 21,661 of fir and 5,794 of beech. As many as 9 regression models were derived for each species. Although the “goodness of fit” of all models showed that they were generally well suited for the data, the best results were obtained for silver fir. The coefficient of determination ranged from 0.946 to 0.948, RMSE (m) was in the interval 1.94-1.97 and the bias (m) was -0.031 to 0.063. Although slightly imprecise parameter estimation was established for spruce, the estimations of the regression parameters obtained for beech were quite less precise. The coefficient of determination for beech was 0.854-0.860, RMSE (m) 2.67-2.72, and the bias (m) ranged from -0.144 to -0.056. The majority of models using Korf’s formula produced slightly better estimations than Michailoff’s, and it proved immaterial which estimated parameter was fixed and which parameters were free