DOI: 10.18150/cgmpca
title: Local chronologies of introduced and native coniferous tree species growing in northwestern Poland (Barlinek Forest Inspectorate)

description: Local chronologies of introduced and native coniferous tree species growing in northwestern Poland (Barlinek Forest Inspectorate) Six tree species were selected for the study. Two of these species have natural occurrences in Poland: Scots pine (Pinus sylvestris) - PS and Common larch (Larix decidua) - LD. The remaining four species were introduced from North America: Lawson Cypress (Chamaecyparis lawsoniana) - CL, Western red cedar (Thuja plicata) - TP, Douglas fir (Pseudotsuga menziesii) - PM and Eastern white pine (Pinus strobus) - PST.Field works were carried out in July 2020 (C. lawsoniana, T. plicata), June 2023 (L. decidua, P. menziesii) and November 2023 (P. sylvestris, P. strobus). Tree height was measured using a Nikon Forestry Pro II laser rangefinder. The trunk diameter was measured using a medium gauge at a height of 1.3 m above ground level. Sampling for dendrochronological analyses was performed on the healthiest trees, i.e., those with no apparent trunk damage. Samples were taken from 131 trees using a Pressler borer at a height of 1.3 m above ground level (Table 1). In the laboratory, the samples were glued to boards, dried and cut with a knife to obtain a clear view of the tree-ring boundaries. Tree ring width (TRW) was measured under a stereoscopic microscope to 0.01 mm using LBD_Measure software (version 1.0).Cross-dating between the individual tree TRW time series was performed using on-screen visual comparisons (high visual similarity), and statistical parameters commonly used as cross-dating coefficients in dendrochronology: Student’s t-test, r correlation coefficient and Gleichläufigkeit (GL%). To check the annual variability of the TRW, standard deviation (STD), mean sensitivity (MS) and autocorrelation coefficient lagged by one year (AC) were also calculated (Table 2).The T. plicata and the P. menziesii trees reach the tallest heights (34 m). The L. decidua and the P. strobus display slightly lower heights (31 and 30 m, respectively). The lowest heights were reached by the P. sylvestris (23.5 m) and the C. lawsoniana (22 m) trees. The P. menziesii trees are distinguished by the highest average trunk diameter (66 cm, ranging from 44 to 99 cm). The lowest trunk diameter was observed for the C. lawsoniana: on average 36 cm, ranging from 27 to 51 cm (Table 1).A chronology was compiled for each studied species. The shortest chronology C. lawsoniana (CL) spans 114 years from 1906 to 2019, and the longest chronologies span 136 years (from 1887 to 2022, L. decidua - LD chronology) and 135 years (from 1887 to 2023, P. sylvestris - PS chronology) (Table 2). On average, a chronology is based on 18 individual growth curves, ranging from 13 curves for the P. strobus (PST) chronology to 21 curves for the L. decidua - LD chronology. The average tree-ring width is the lowest for the PS (P. sylvestris) chronology (1.62 mm/year) and for the PST (P. strobus) chronology (1.69 mm/year), while the highest value is recorded for the TP (T. plicata) chronology (2.80 mm/year).The most convergent chronology pair, as expressed by the t index, are PM/TP chronologies (t=11.21). High t values (&gt;7.0) are also obtained for the following pairs of chronologies: CL/PM and PS/PST. The lowest t index values are observed for the CL/PST chronologies (2.30). Low t index values (t&lt;3.0) are also displayed by the pairs CL/LD and LD/PS (Table 3). As expressed by the GL index, the PS and PST chronologies represent the most convergent chronology pair (73%). GL values &gt;65% are also obtained for the following pairs of chronologies: LD/PS, CL/PS, PM/PS, CL/PM and PM/PST. The lowest GL value was obtained for the CL/LD pair (44%). Comparably low GL values (&lt;50%) were noted for the pairs of chronologies: LD/PST, CL/TP and PST/TP (Table 3). Files with data of coniferous tree-ring width and local chronologies (PS, LD, CL, TP, PM, PST): 1st column - year, 2nd column and next - tree-ring width of individual trees in mm (tree1, tree2, …), next column - local chronology in mm (bold numbers), last column - number of samples in a given year.Table 1. List of research plots with basic information.Table 2. Basic statistics of measured and index (residual) local coniferous chronologies: P. sylvestris (PS), L. decidua (LD), C. lawsoniana (CL), T. plicata (TP), P. menziesii (PM) and P. strobus (PST). Abbreviations: TRW – tree-ring width; SD – standard deviation; AC – first order autocorrelation; MS – mean sensitivity; EPS – Expressed Population Signal; rbt – series intercorrelation.Table 3. Similarity of local chronologies of P. sylvestris (PS), L. decidua (LD), C. lawsoniana (CL), T. plicata (TP), P. menziesii (PM) and P. strobus (PST) as measured with t and GL (%) values.