1 Introduction

During the eighteenth and nineteenth centuries, the black cherry tree (Prunus serotina Ehrh.) was introduced as a productive species in European forests. However, the tree and its wood did not perform as expected (Tumiłowicz 1977; Starfinger 1997), despite being ecologically and economically beneficial in its native range in North and Central America (Marquis 1990; Ryo et al. 2021). The wood from the Allegheny Plateau in the USA has long been a valued raw material (Record and Hess 1944; Marquis 1990; Starfinger 1997; Ray 2018). The continued introduction of black cherry into European forests throughout the 19th and much of the 20th century as a phytomeliorative or wind and fire protection species contributed to its rapid spread and eventually to its invasive neophyte status in Europe (Starfinger 1997, Vanhellemont 2009). Currently, it is a component of many forest ecosystems, both managed and covered by various forms of nature protection, combated on a large scale and at high costs (Starfinger et al. 2003; Kettunen et al. 2008; Otręba et al. 2014; Ligocki et al. 2021). The properties of its wood are therefore important in the ecological, economic, and utility context, including, for example, the possibility of the local-scale production of wood products. However, knowledge about the characteristics of black cherry wood in its exotic range in Europe, including Poland, is still poor and fragmentary (Pacyniak and Surmiński 1976; Tumiłowicz 1977). This also applies to the chemical composition and the colonization of black cherry wood by fungi in natural conditions (Marciszewska et al. 2018, 2020; Baranowska et al. 2019, 2023), its susceptibility to decomposition and the possibility of combating black cherry with biological methods through the use of wood-inhabiting fungi (Szewczyk 2022) other than only Chondrostereum purpureum (Hamberg et al. 2021).

The work aimed to determine and characterize black cherry wood’s physical, mechanical, and chemical properties and resistance to fungal decay in the invaded range of the species. The premise for undertaking this research was the finding of different rates of tree dieback and the appearance of fungi sporocarps on the stumps of controlled black cherry trees (Marciszewska et al. 2018, 2020) in a field experiment carried out in Kampinos National Park (KNP) in 2015–2018 (Otręba et al. 2017; Marciszewska et al. 2018). The age of the oldest specimens of the black cherry growing nowadays in the area of KNP and originating from small but numerous and dispersed plantings in the 1950s–1970s (Otręba 2014) may even be slightly over 70 years old. The research hypothesis assumes that:

  • - The wood of trees growing in better habitat conditions, expressed by higher humidity and organic nitrogen and carbon content in generally poor Arenosol and Podzolic soils, will feature wider rings.

  • - Due to the semi-ring porous nature of black cherry wood, a larger average ring width will translate into a higher density of this wood and differences in other physical properties.

  • - Better physical parameters will be associated with better mechanical properties of the wood and its specific chemical composition.

  • - Better physical-mechanical properties of wood and its specific chemical composition will, in turn, determine greater resistance to fungal decay in trees grown in moister and richer soil.

2 Materials and methods

2.1 Research plots, collection, and initial preparation of research material

The wood for the tests was collected in February 2020 in two stands constituting two separate research plots, about 5 km apart, located in the Laski Protected Area of the Kampinos National Park and established in 2015 to research black cherry control (Table 1; Otręba et al. 2017; Marciszewska et al. 2018). The main abiotic factor differentiating the habitat conditions on both plots was moisture and the total content of organic nitrogen and carbon in the soil: higher in the plot in Lipków and associated with the presence of Gleic Albic Podzol soil, and lower in the drier and poorer soil of the Albic Arenosol type in Sieraków (Marciszewska et al. 2018). Both soils have low pH (Lipków: 3.7; Sieraków: 3.9), a leached horizon in the soil profile, and are classified as poor.

Table 1 Characteristics of tree stands on study plots in the Laski Protection Area of the Kampinos National Park (Otręba et al. 2017, Draft Protection Plan for the Kampinos National Park 2023). Birch – Betula pendula Roth, locust – Robinia pseudoacacia L., maple – Acer platanoides L., pine – Pinus sylvestris L., oak – Quercus robur L., red oak – Q. rubra L.
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Three sample trees were selected per plot, characterized by close to average height and thickness and straight trunk, without visible mechanical damage, cankers, sporocarps of fungi, or traces of insects. The trunk diameter was measured at breast height (DBH, i.e., approx. 1.3 m from the ground) in two perpendicular directions (DBH 1, DBH 2). The age of the sample trees was determined as cambial at a height of 50 cm from the ground, based on the number of wood rings counted with CooRecorder 7.81 software (Cybis Elektronik and Data AB, Sweden) along the radius of the trunk cross-section from the north side in wood images acquired using an Epson scanner. The last wood ring included in the measurements was produced in the 2019 growing season. Based on the analysis of the images, the vascular type of wood and the presence of heartwood were also verified. Three one-meter rollers were made from 0.5 m to 3.5 m above the ground from each trunk, seasoned outdoor to air dry, and then used for further research. An equal number of mature wood samples were taken from each roll. Further measurements were carried out on the mixed sample.

2.2 Research on the structural, physical, and mechanical properties of wood

Wood properties were determined for harvested and seasoned wood samples without defects. Two coarse samples, about 40 cm in length, were cut from each 1 m wooden roller. Then, three sets of axially matched samples were cut out from each coarse sample for specific physical and mechanical tests. Two sets of 20 × 20 × 30 mm samples were twins of 20 × 20 × 300 mm samples (the last specified dimension of the sample is the dimension along the grain). Twenty-two wood properties (Table 2) were determined using a total of 120 samples of mature wood (60 samples per plot, 20 samples per tree).

Table 2 Wood properties tested on black cherry wood samples (Prunus serotina Ehrh.) from the invaded range of the species in the Kampinos National Park (Poland). All of the properties were tested on 120 samples
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The average ring width was measured on scanned (1200 dpi) cross-sections of wood samples using CooRecorder 7.8 software. The density of wood was determined at 12% absolute humidity using the same samples. An electronic caliper with an accuracy of 0.01 mm was used to make stereometric measurements in the tangential, radial, and longitudinal directions. The mass of samples was determined on a technical scale with an accuracy of 0.001 g. The moisture content of the samples was determined using the drying-weighing method (PN-77/D-04100). After determining the density, compression tests were performed on the same samples along the grain. The modulus of elasticity for static bending and static bending was tested in the tangential direction (perpendicular to the radial section) with a support spacing of 240 mm. All mechanical properties tests were carried out at 12% humidity by applicable standards on the ZD-10 universal testing machine with a valid legalization certificate.

After static bending tests, 20 × 20 × 30 mm samples were cut from the ends of the 20 × 20 × 300 mm samples to determine the density of completely dry wood, basic density, percentage of wood substance, porosity, total radial, tangential, longitudinal and volume shrinkage, shrinkage coefficients and shrinkage anisotropy index. The samples were immersed in distilled water to moisten to the maximum swollen state (i.e., about 30% moisture) and measured with a caliper in three directions with an accuracy of 0.01 mm. After the samples reached a moisture content of several percent, they were dried in a dryer at about 105 °C to a moisture content of 0%. Then, the samples were weighed on a technical balance with an accuracy of 0.001 g, and the stereometric measurement was repeated.

The wood density of the samples used for the decay test was determined by the drying-weighing method (Krzysik 1978; Kokociński 2004) at a wood moisture content of approx. 11%.

2.3 Anatomical studies of wood fibers

A sample of 20 × 20 × 30 mm without defects was selected from each tree and soaked in distilled water for six weeks until it sank. Then, using a Leica SM 2000 R microtome, thin slices of wood were cut and macerated for 24 h at 60 °C in a 1:1 (v/v) mixture of 30% hydrogen peroxide and 99.5% acetic acid. After rinsing three times with distilled water and three days of incubation, the macerates were stained for 24 h with Etzold's dye, then rinsed three times with a 1:1 (v/v) mixture of glycerol and distilled water and incubated for another 24 h. The samples were later transferred to slides and sealed in a solution of glycerol and water in a volume ratio of 1:1. Then, using an Olympus Provis AX70 microscope equipped with an Olympus UC90 camera and "Cell Sens Standard" software, 30 individual undamaged wood fibers were imaged for each tree. On the archived images, the following measurements were made using the ImageJ program: length (L, mm), diameter (D, mm), lumen diameter (d, mm), and fiber wall thickness (G, mm). A total of 180 fibers were measured, 90 for each plot.

Based on the obtained results, calculations of selected indicators describing wood fibers were made: selection was based on their importance in the pulp production process and for the use of wood in the pulp and paper industry (Mühlsteph 1941; Runkel 1949; Einspar 1964; Surewicz 1971; Surma-Ślusarska and Surewicz 1985a, 1985b; Przybysz 2005a, 2005b, 2005c; Przybysz and Godlewska 2005). The following six indicators were defined:

  • - Slenderness index (L/D), which should be as high as possible and amount to at least 40; the higher the value, the greater the strength of the paper obtained (Oniśko 1970).

  • - Runkel ratio (2G/d), which significantly affects the tendency of fibers to felt and the strength properties of paper products. The lower the value, the more valuable the raw material is for the paper industry (Runkel 1949). The thinner the wall of the fiber, the lower the value of this ratio.

  • - Rigidity coefficient (G/D × 100%) shows an inversely proportional effect on the breaking strength. The thicker the fiber wall, the higher the value of the coefficient and the lower the strength parameters.

  • - Mühlsteph ratio ((D2-d2)/D2), which shows an inversely proportional tendency concerning deformation (flattening) of the fiber during the drying process (Mühlsteph 1941; Einspar 1964). The lower the Mühlsteph ratio, the greater the tendency to fulling.

  • - Flexibility coefficient (d/D), the higher the d/D the greater the fiber lumen and the smaller the diameter (the fibers are more flexible). The higher the index, the more valuable the raw material is for papermaking.

  • - Solids index ((D2-d2)/L), which is a measure of the homogeneity and consistency of the paper (Surma-Ślusarska and Surewicz 1985a, 1985b).

2.4 Determination of chemical composition and pH of wood

Some of the material prepared in the form of mature wood samples for the fungal decay test (see Sect. 2.5) was used to determine the chemical composition of black cherry wood. The ground material (0.4–1.0 mm fraction, 30 g per plot) consisting mainly of heartwood was dried at 105 °C to constant weight. The material was extracted in a Soxhlet apparatus according to the method described by Sluiter et al. (2008b). The extraction was carried out for 10 h using an azeotropic mixture of chloroform and 96% ethyl alcohol in a weight ratio (93:7), which as demonstrated by Antczak et al. (2006) is a very good replacement for the previously used mixture of benzene and ethanol, enabling the complete removal of both polar and non-polar low molecular substances. Identification of the extractives was performed by gas chromatography with mass spectrometry (GC–MS) on an ultra-efficient GCMS-QP2010 (Shimadzu, Kyoto, Japan) chromatograph with an AOC-20i autosampler, Zebron ZB5M column, 30 m long, 0.25 mm in diameter, 0.25 µm bed (Phenomenex, Torrance, CA, USA) with the following program and analysis parameters: injection temperature 250 °C, split-direct, detector power supply 1 kV; temperature program: 50 °C held for 8 min, boost 10 °C to 320 °C and held for 10 min.

After extraction, the content of the following substances was determined in the wood:

  • - lignin insoluble in 72% sulfuric acid VI (Klason lignin) (TAPPI T222 om-02, 2006),

  • - lignin soluble in 72% sulfuric acid VI using a spectrophotometer UV-Vis Shimadzu MINI-1240 (TAPPI UM 250, 1985),

  • - cellulose by Kürschner and Hoffer method using a mixture of 65% nitric acid V and 96% ethyl alcohol (Saeman et al. 1954; Krutul 2002),

  • - holocellulose using sodium chlorite (Wise et al. 1946),

  • - mineral substances in the form of ash using a muffle furnace (Sluiter et al. 2008a).

The pH of the wood was determined using the method described by Mayer and Koch (2007), also for the ground (fraction 0.4–1.0 mm), non-extracted material. A mixture of 1 g of wood and 25 cm3 of distilled water was used for the determination. The pH measurement was carried out with the CP-551 pH-meter (Elmetron, Zabrze, Poland) with the IJ 44C electrode (Elmetron, Zabrze, Poland) after 1 h of soaking. The wood’s chemical composition and pH measurements were each determined three times, and the averages and statistics were given for all sample trees and broken down into plots.

2.5 Study of wood fungal decay

Four species of Basidiomycota fungi, responsible for different types of wood decay, used in standard tests of the durability of natural wood, of economic importance, and common in Polish forests, were used in the study. The brown rot type was represented by Coniophora puteana (Schumach.) P. Karst. (strain BAM Ebw. 15), white uniform rot by Armillaria borealis Marxm. & Korhonen and Trametes versicolor (L.) Lloyd and white pocket rot by Heterobasidion annosum (Fr.) Bref. The isolates came from the collection of pure cultures of the Department of Forest Protection of the Warsaw University of Life Sciences. Decay resistance tests were conducted on 288 wood samples (144 samples per plot, 36 samples per fungal species, and 12 per sample tree) measuring 1.5 × 2.5 × 5.0 cm, consisting mainly of heartwood. Due to the relatively small size of the tree trunks, some samples were not homogeneous in terms of wood structure, i.e., apart from the heartwood, they also contained a minimal share of sapwood.

The ability of the fungus to decompose the wood was determined based on the dry mass loss of wood samples (ML) in a 16-week decay test. The basic test procedures were performed following the PN-EN 350 (2016) and PN-EN-113 (2022) standards and according to the works of Szczepkowski (2010a, b) and Szczepkowski et al. (2021). Briefly, after conditioning in normal climatic conditions, the samples were measured with an accuracy of 0.01 mm and weighed with an accuracy of 0.01 g. For each plot, six additional wood samples (12 in total, two for each sample tree) were dried at 105 °C to constant weight and weighed to calculate the average moisture content of the samples conditioned in normal climate. The mean moisture content (MC) was determined as the average moisture content of six samples from each location (12 samples in total). The above calculations made it possible to determine the percentage mass loss of the samples, with only samples having MC over 25% included (134 of the initial 144 samples; Rypáček 1966; EN 113 1980; Rayner and Boddy 1988; Schmidt 2006).

The wood samples used in the decay test were not artificially dried. Before the decay testing, the samples were sterilized twice, 24 h apart, in an autoclave at 121 °C and 0.12 MPa pressure for 20 and 10 min, respectively. They were then soaked in sterile distilled water for about one hour. Following soaking, two samples of wood were placed in Kolle flasks with about three-week-old cultures of the tested species of fungi grown in 50 cm3 of 2% MEA medium (Carl Roth, Germany). After 16 weeks of incubation at 22 ± 2 °C and 70 ± 5% relative humidity, the samples were removed, cleaned of surface mycelium, and weighed. They were then dried at 105 °C to constant weight, reweighed, and mass loss calculated. To compare and verify the isolates’ properties, an additional decay test was carried out for four samples of beech wood (Fagus sylvatica L.), according to the method adopted in the experiment.

2.6 Calculations and statistical analysis

An Excel spreadsheet from Microsoft Office 365 software was used to organize the measurement data and calculate basic statistics. STATISTICA 13.1 (The TIBCO Software Inc. 2017) was used for further analysis. A set of descriptive statistics of the examined parameters (mean, minimum, maximum, standard deviation) was developed. A significance level of ɑ = 0.05 was assumed for each test. Due to the inconsistency of the data distribution with the normal distribution, the non-parametric Mann–Whitney U test was performed. In the case of significant differences between the study groups (plots in Lipków and Sieraków), prepared descriptive statistics were used to assess the differences.

3 Results and discussion

3.1 Biometrics of sample trees

The sample trees from the plot in Sieraków had a slightly larger diameter at breast height than those from the plot in Lipków (Table 3). The average DBH here was 17.68 cm compared to 15.40 cm in Lipków, with the same average height of trees on both plots of 16.5 m. The cambial age of the trees from the plot in Lipków was slightly higher and averaged 46 years, while in Sieraków, it was 40 years (Table 3).

Table 3 Biometric parameters of sample trees used for testing the properties of black cherry (Prunus serotina Ehrh.) wood on two study plots located in the Kampinos National Park
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3.2 Wood grain morphology

The examined wood contains a zone of densely arranged vessels at the beginning of each ring and a less frequent arrangement of smaller vessels in transitional and latewood (Fig. 1), which, according to the IAWA definition (1989), corresponds to the wood of the semi-ring-porous vascular type. In the literature, black cherry wood is described as similar to wood of other species of the genus Prunus and as semi-ring-porous (Wagenführ 2000) to diffuse-porous (Insidewood, The Wood Database). The impact of ring width on the physical and mechanical properties of wood is most strongly manifested in ring-porous woods (Jagels 2006), where both the reduction and the increase of the ring width occur mainly in the latewood zone containing reinforcing elements (Jagels 2006, Tulik et al. 2010). In a semi-ring-porous wood of black cherry, the relationship between the width of the rings and the physical and mechanical properties of the wood can also be expected, but a weaker one, while in diffuse-porous wood, such a relationship is not observed (Jagels 2006).

Fig. 1
figure 1

Fragment of a scan of a disc of black cherry wood from the plot in Sieraków in the Kampinos National Park. In the upper right corner, an enlarged fragment with a visible arrangement of vessels in a wood ring is shown

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The examined wood is characterized by the presence of colored heartwood (Fig. 1). The number of rings in the sapwood of tree trunks did not differ significantly. It averaged eight rings (SD ± 1.5) for trees from both study plots. In addition, there was always one intermediate ring between the sapwood and the fully developed heartwood.

3.3 Structural, physical, and mechanical properties of the wood

Table 4 presents the essential characteristics of the examined wood properties. Statistically significant differences between the plots were shown for the average ring width, density, total shrinkage, shrinkage coefficient, shrinkage anisotropy index, modulus of elasticity, and strength coefficient of wood quality. Wood from Lipków had a higher average ring width of 3.26 mm, which resulted in a statistically significant, higher density of wood for each sample size and humidity. Significant statistical differences between the plots were also observed for the total tangential shrinkage, the coefficient of tangential shrinkage, and the shrinkage anisotropy index. However, wood from Sieraków had higher values for these physical properties. For the mechanical properties, significant differences were found only for the modulus of elasticity in static bending and the coefficient of modulus of elasticity in static bending. The wood from Sieraków had higher values for these properties. However, no statistically significant differences were found for the other physical and mechanical properties examined.

Table 4 Structural, physical, and mechanical properties of black cherry wood (Prunus serotina Ehrh.) in the Kampinos National Park. M – mean, Max. – maximum, Me – median, Min. – minimum, SD – standard deviation. Wood properties showing statistically significant differences between the plots in terms of the mean are marked in bold (U Mann–Whitney test). Data for 120 samples in total, 60 samples per plot
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The average wood density values obtained from the two habitats studied were 649 kg/m3 at 12% humidity and 613 kg/m3 at 0% humidity. These values are higher than those reported by Kozakiewicz (2010) for wood from North America, which were 580 kg/m3 and 550 kg/m3 respectively. The tested wood had a porosity of 59%, which is lower than the value given by Kozakiewicz (2010) – 64%. The higher density of the wood studied resulted in higher shrinkage values in individual anatomical directions: longitudinal – 0.3%, radial – 5%, tangential – 11%, volumetric – 16%. This is compared to Kozakiewicz’s (2010) findings of 0.2%, 4.0%, 7.7%, and 12.5%, respectively. The obtained results classify black cherry wood from Poland as a wood with medium shrinkage. For mechanical properties at 12% humidity, lower values were obtained for compressive strength Rc12 – 56.8 MPa and modulus of elasticity Eg12 – 1942 MPa than those reported by Kozakiewicz (2010), which were 59 MPa and 13,500 MPa, respectively. However, a higher value was obtained for static bending strength Rg12 – 102 MPa compared to 93 MPa.

In our tests, we found that the density of the wood at 12% humidity is higher than that of Prunus serotina wood from eastern North America, which has a density of 560 kg/m3 (Gabarro Wood…). The shrinkage anisotropy index of American wood, with a value of 1.92, is lower than that of black cherry wood from the Kampinos Forest, which was 2.24 and resulted in a stronger tendency for wood from Poland to warp. The mechanical properties of the wood from Lipków and Sieraków are also better than those recorded in North America: Rc12 – 49 MPa, Rg12 – 85 MPa, Eg12 – 10,300 MPa (Gabarro Wood…).

Studies carried out in Latvia on Prunus avium L. (Pavlovics 2011) showed an average ring width of 3.3 mm, similar to that obtained in this study, 3.05 mm. The densities we obtained for wood from the Kampinos Forest at 0% and 12% humidity were slightly lower than those obtained in Latvia – 628 kg/m3 and 657 kg/m3, respectively, with the same porosity of 59%. Shrinkages in individual anatomical directions also had similar values to those from Latvia: 5.1% in the radial direction, 10.7% in the tangential direction, and 14.5% in total volumetric shrinkage. The shrinkage coefficients in individual anatomical directions and the total volumetric shrinkage also overlap. In the case of mechanical properties tested at 12% humidity, the values of Rc12 and Eg12 of black cherry wood from the Kampinos Forest were slightly higher compared to those obtained in Latvia – 52.5 MPa and 10,500 MPa – and slightly lower for Rg12 at 104.7 MPa (Pavlovics 2011).

Our research on Prunus serotina wood from the Kampinos Forest showed higher values of wood parameters than those obtained for 41-year-old Prunus avium in research carried out in northern Poland in the Elbląg Forest District on the deciduous fresh forest habitat, where the average annual ring width was 2.97 mm and density at 12% humidity – 578 kg/m3 (Pięta 2019). Similarly, for mechanical properties: Rc12 – 49.3 MPa, Rg12 – 92.5 MPa, Eg12 – 10,862 MPa. The JRc12 strength quality coefficient showed comparable values in both tests. On the other hand, the JRg12 and JEg12 coefficients for Prunus avium were higher: 16 km and 1883.5 km, respectively. Wood from the Elbląg Forest District also had lower values for physical properties such as density 0% – 526 kg/m3, basic density 456 kg/m3, and the share of wood substance – 35%. Lower density resulted in lower shrinkage values in individual anatomical directions: radial – 3.84%, tangential – 9.57%, and volumetric – 13.35%. Higher values were obtained for longitudinal shrinkage – 0.35% and the shrinkage anisotropy index – 2.53 (Pokropowicz 2020). The obtained density at 12% is also higher than that of Prunus padus wood from Finland – 600 kg/m3 at 15% humidity (Uusitalo 2004).

3.4 Anatomical properties of wood fibers

Table 5 presents diverse parameters and indicators that define the fiber structure of the black cherry wood. The length, average width, and lumen diameter of the wood fibers showed significant statistical differences between the plots. Fibers from trees in Lipków had higher values for these characteristics. Among the calculated ratios, the Runkel and Mühlsteph ratios and the flexibility coefficient showed significant differences. Wood from Lipków had lower values for the first three indices and higher values for flexibility, making it a better raw material for the production of cellulose and the pulp and paper industry. However, due to the fibers' shortness, using this wood in the pulp and paper industry is possible only as a pulp additive. Uusitalo (2004) reported 1.5 mm as the fiber length of Prunus padus from Scandinavia, which is about 0.5 mm longer than the fiber length we found for black cherry.

Table 5 The parameters and indexes of black cherry wood (Prunus serotina Ehrh.) fiber structure in the Kampinos National Park. N – number of samples, M – mean, Max. – maximum, Me – median, Min. – minimum, SD – standard deviation. Statistically significant differences (U Mann–Whitney test) between plots means are marked in bold. Data for 180 samples in total, 90 samples per plot
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The black cherry fibers from KNP shared a comparable length of 10 mm with Wagenführ’s report (2000). However, they demonstrated greater values of fiber diameter (0.0199 mm), wall thickness (0.0049 mm), and Runkel ratio (1.07) compared to 0.0175 mm, 0.002 mm, and 0.46, respectively (Wagenführ 2000). The lumen diameter was the only difference found, being 0.013 mm larger than in our study. No significant differences were observed between the plots for wall thickness, slenderness index, and solids index.

3.5 Chemical composition and pH of wood

Wood from both study plots did not differ significantly in terms of the six chemical parameters tested, which are presented in Table 6. However, the percentage share of extractives was 1.5 times higher in the wood of trees from the plot with wetter and richer soil (Lipków, 4.3%) compared to the plot in Sieraków (2.8%) with drier and poorer soil. The results obtained in this work are similar to literature data, which, even within the same species, show significant differences in the chemical composition of the wood. According to Pettersen (1984), the content of extractives in P. serotina wood was 5%, and in Prunus padus wood, it was 2%. In turn, the cellulose content in the wood of these species was 45% and 47%, respectively, while the holocellulose content was 85% and 81%. According to the results presented by Pettersen (1984), the Klason lignin content in the wood of P. serotina and P. padus is at the same level and amounts to 21%. Also, Wagenführ (2000) gives a lignin content for P. serotina of approx. 22%. Similarly, the ash content, representing mineral substances, given for P. serotina wood by Pettersen (1984) and Wagenführ (2000) was similar to the results obtained in this work. It amounted to 0.1%, while for P. padus Pettersen (1984) gives a value of 0.2%.

Table 6 Chemical composition of the wood of black cherry (Prunus serotina Ehrh.) growing in the Kampinos National Park on plots differing in soil moisture and total organic carbon and nitrogen content: Lipków – Gleic Albic Podzol soil type, wetter and richer; Sieraków – Albic Arenosol soils type, drier and poorer. The significance of the differences was tested with the U Mann–Whitney test
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The examined wood was acidic: the average pH determined for wood samples from both plots in total was 4.53 (SD ± 0.05). The wood from Lipków had a lower pH value of 4.27 (SD ± 0.05), the average pH of wood from Sieraków was 4.51 (SD ± 0.02). The results obtained are higher than the pH values given by Mayer and Koch (2007) for the heartwood of black cherry, but lower than the values given by these authors for sapwood, which are 4.0 and 5.0, respectively. Part of this difference may be due to some proportion of sapwood in the overall heartwood samples of the examined wood.

The analysis of the chemical composition of chloroform-ethanol extract showed the presence of 44 different compounds in the examined wood (Table 7), qualitatively determined with a probability of 71% to 91%. Of these, 12 were common to the wood of both plots, 16 were exclusive to each plot, and six compounds were characterized by antifungal activity confirmed in the literature. A significantly higher total share of compounds with confirmed antifungal properties was found in the chloroform-ethanol extract from Lipków wood, corresponding to 62.93% of the peaks area of all identified substances included in the chromatogram, compared to 8.68% for wood from Sieraków. The extracts differed in the type and number of these compounds (Table 7): the presence of all six compounds with antifungal activity was found in the wood from Lipków; in the wood from Sieraków there were only three such compounds – hydroquinone (Fathi Azarbayjani et al. 2019; Talebi et al. 2018), caproic acid (Park et al. 1986) and squalene (Duriati et al. 1993; Yusoff et al. 2020). The chloroform-ethanol extract from Lipków was distinguished by a particularly high content of caproic acid, catechol (Kocaçalişkan et al. 2006), and 5-hydroxy-2,3-dimethyl-2-cyclopenten-1-one (de Souza et al. 2017) with trace amounts of hydroquinone, phytol (Yusoff et al. 2020) and squalene.

Table 7 Chemical composition of chloroform-ethanol extract of black cherry wood growing in the Kampinos National Park. Determination by GC-MS method
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3.6 Natural resistance of wood to fungal decay

3.6.1 The wood density of the samples used in the decay test

The wood density of the samples used in the decay test ranged from 545 to 741 kg/m3 for the samples from Lipków and from 582 to 720 kg/m3 for the samples from Sieraków (Table 8). The average wood density values of the samples taken from the trees in the Lipków plot before the examination of decay by particular species of fungi ranged from 645 kg/m3 (C. puteana) to 681 kg/m3 (H. annosum). The average values of wood density of samples made of trees from the plot in Sieraków before the examination of decay by particular species of fungi ranged from 630 kg/m3 (H. annosum) to 634 kg/m3 (A. borealis).

Table 8 Density of black cherry (Prunus serotina Ehrh.) wood samples used in the decay test by four species of Basidiomycota fungi. Means of 36 samples representing three sample trees on each study plot in the Kampinos National Park
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The wood density of the tested samples was slightly higher than the values reported by other authors. The average density of P. serotina wood samples used in the study, calculated jointly for both plots, was 640 kg/m3 and was slightly higher than the value of 630 kg/m3 given for wood of this species from a 30-year-old tree with a DBH of 28 cm obtained from Municipal Forests in Poznań (Western Poland) by Pacyniak and Surmiński (1976). According to Bärner (1942), the density of air-dry black cherry wood is 510 kg/m3; Kozakiewicz (2010) for wood of P. serotina from its original range gives density values in the range of 490–580–620 kg/m3 for 12% moisture content. Wagenführ (2000) reports that P. serotina wood is characterized by similar properties to Prunus avium wood and gives density values in the range of 525–580–615 kg/m3 (at a moisture content of 12–15%). The wood density of P. serotina from its natural range, given as an average dry weight by The Wood Database, is 560 kg/m3.

3.6.2 Mass loss of wood after the decay test

Based on the median, the smallest value of mass loss of wood (ML, in total for both plots) was found in the samples decomposed by C. puteana (1.49%, Table 9). A slightly higher value (2.86%) was found for H. annosum. In the case of A. borealis the ML was about twice to three times as high as in the case of the two above-mentioned fungal species. The highest value of the ML (15.89%) was found for T. versicolor: this loss is more than twice as large as compared to A. borealis and about five to seven times greater as compared to H. annosum and C. puteana respectively. Except for C. puteana the wood samples from Sieraków were slightly more intensively decomposed by tested species of fungi than the samples from Lipków (Table 9). However, considering the mean values of ML, this statement also applies to C. puteana. Depending on the fungus species, the median differences of ML ranged from 0.06% for C. puteana to 4.07% for T. versicolor (Table 9).

Table 9 The mass loss of black cherry (Prunus serotina Ehrh.) wood from the Kampinos National Park due to decay by four species of Basidiomycota fungi. Means and medians for three trees and 36 samples per plot and six trees and 72 samples in total (except for A. borealis). M – mean, Max. – maximum, ME – median, Min. – minimum
Full size table

The decomposition abilities of the fungal isolates used for decay tests were checked in a parallel experiment carried out on the samples of beech wood. The obtained mass losses were higher in comparison with black cherry wood: the largest beech wood ML was found for T. versicolor, the smallest for H. annosum (Table 10).

Table 10 Density, moisture, and mass loss of beech wood (Fagus sylvatica L.) in samples after the decay test carried out by four fungal isolates to compare and verify their decomposition abilities. Data for four samples
Full size table

The resistance of wood to biotic factors, including fungi, is an important functional feature that determines the scope of application of a given wood. The natural resistance of wood to fungal decay is conditioned by a number of its features and properties and is considered an essential indicator of wood quality (Cartwright and Findlay 1958; Rypáček 1966; Schmidt 2006).

To date, little work has been done on the natural durability of P. serotina wood, although its extracts have been extensively studied for color and color changes due to heat treatment in veneer production (Mayer et al. 2006). Scheffer and Cowling (1966) describe black cherry wood as resistant or very resistant to fungal rot. However, according to Ross (2010), P. serotina wood is considered to be medium-durable. According to The Wood Database, black cherry heartwood is rated as being very durable and resistant to decay, but typically not used in exterior applications.

Of the fungi species studied, the greatest ML of P. serotina wood was caused by T. versicolor, responsible for white decay, which can attack the wood of almost all woody plants, using a full range of enzyme systems to decompose the substrate entirely (Rayner and Boddy 1988). It is widely distributed in the world, mainly as a saprotroph, on many species of deciduous trees (Kotlaba 1984; Breitenbach and Kränzlin 1986; Bernicchia 2005; Ryvarden and Melo 2014), including P. serotina, both in its natural (Browne and Laurie 1968; Ginns 1986) and secondary range (Marciszewska et al. 2018, 2020). It is used as a mandatory species in hardwood durability tests (PN-EN 350 2018; PN-EN 113–2 2022). In the parallel decay test of the Fagus sylvatica reference wood samples, ML of over 30% was found (Table 10) i.e., above the 20% threshold recommended in the PN-EN 113–2 (2022) standard, which proves the very good properties of the applied isolate. In our study, P. serotina wood presented an ML of about 16% when tested against T. versicolor. Therefore, wood sourced from 45-year-old P. serotina trees in the invaded range was classified as slightly durable ( DC 4, 15 < ML ≤ 3, PN-EN 350 2018). Testing on 13-year-old trees from the secondary range in Germany produced lower results, with a median ML of 3.6% in non-leached samples and 8.4% in leached samples (Brischke et al. 2018).

In a study conducted on 30-year-old black cherry trees in western Poland, it was found that Cyclocybe aegerita (V. Brig.) Vizzini (= Agrocybe aegerita (V. Brig.) Singer) and Chondrostereum purpureum (Pers.) Pouzar, two other species of fungi that cause the same type of decay as T. versicolor, resulted in 9% ML in wood samples (Szewczyk 2022). This is almost half as much as T. versicolor in our study. However, Szewczyk (2022) tested sapwood in a study lasting twelve weeks. Black cherry wood is classified as intermediate between diffuse- and ring-porous (semi-ring-porous wood) with colored heartwood (Wagenführ 2000; Insidewood; The Wood Database). The ML observed in P. serotina wood may be attributed to its structure. It is lower than in some diffuse-porous species without heartwood but greater than that of ring-porous species with colored heartwood. The same strain of T. versicolor used in the experiment caused significant ML of 19.6–31.0% in the diffuse-porous wood of F. sylvatica (Szczepkowski 2010a), but only 1.3% in the case of heartwood of Quercus robur (Szczepkowski 2010b). Other sources report a slight reduction in the mass of oak wood by 3.7% (Cartwright and Findlay 1958) and 4.1–6.2% (Aloui et al. 2004) as a result of decay by T. versicolor. Oak is classified in the group of trees with the most durable wood (PN-EN 350 2016) due to the high proportion of tannins/tannins rich in phenolic compounds that inhibit the development of fungi in wood (Szczepkowski 2010b). Our research has revealed that the wood of P. serotina, like its leaves and inflorescences (Telichowska et al. 2020; Brozdowski et al. 2021), contains phenolic compounds that can inhibit fungal activity.

The ML of black cherry wood samples caused by A. borealis was the second largest in our study. However, this species caused ML of beech wood below the recommended threshold by the PN-EN 113–2 (2022) standard, making it unsuitable for classifying black cherry wood durability. The fungus causes an even white rot of wood and is one of the pathogens responsible for a dangerous disease – Armillaria root rot (Fox 2000; Żółciak 2015; Sierota et al. 2019; Szczepkowski et al. 2022). It attacks the wood of both coniferous and deciduous trees, including representatives of the genus Prunus (Jankovský 2003; Kedves et al. 2021), such as the black cherry. This species is genetically similar to Armillaria ostoyae (Romagn.) Herink, which caused a similar reduction in the mass of black cherry wood samples by an average of 7% (Szewczyk 2022). In contrast, studies by Żółciak (2002) found that strains of A. borealis caused three times greater ML of beech wood ranging from 19.68 to 21.40% after a twelve weeks decay test and twice as large in oak wood in the range of 9.74–12.43% and much less in spruce wood (5.41–7.77%). Our results for black cherry were similar to those observed in spruce wood.

In the case of C. puteana, the cause of brown decay, the median mass of P. serotina wood samples decreased by 1.49%. This decrease could potentially indicate a durability class of 1, meaning the wood is very durable (DC 1, ML ≤ 5%, PN-EN 350 2018) if not for the higher ML for T. versicolor. In the studies of Brischke et al. (2018) C. puteana isolate reduced sample weight by 8.4%. The C. puteana strain used in our research in a parallel test of beech wood decay resulted in a 20% mass reduction of the samples (Table 10), which indicates its good decomposition properties, following the PN-EN 113–2 (2022) standard. The same strain of C. puteana, in the research of Szczepkowski (2010a), caused a mass loss of beech wood from various regions of Poland in the range of 25.9–30.7%. However, in the case of oak wood from various regions of Poland, the mass of samples decreased by an average of 2.1% (Szczepkowski 2010b).

Sporocarps of Heterobasidion annosum (Fr.) Bref were found on the roots of P. serotina samples in both Lipków and Sieraków (Marciszewska et al. 2018). Therefore, an isolate of this species was used in this study. The fungus is the cause of one of the most dangerous diseases in forestry – Annosum root rot. The pathogen mainly affects conifers, less often deciduous trees (Woodward et al. 1998; Sierota et al. 2019; Szczepkowski et al. 2022). The H. annosum isolate was derived from Betula pendula and caused the second lowest ML of black cherry wood samples among the tested fungi, with a median of 2.86%. Since this species caused a mass loss of beech wood below the threshold recommended by the PN-EN 113–2 (2022) standard it could not be used to classify black cherry wood in terms of durability. In other laboratory decay tests, strains of H. annosum give similar results reducing the mass of beech wood by 5–6% (Schmidt et al. 1986) and pine wood after two months of incubation by 3.4% (Mitchelson and Korhonen 1998).

It is worth noting that regarding mean values the wood samples from Sieraków showed a greater ML caused by all four species than those from Lipków (Table 9). The wood from Lipków contained about 1.5 times more extractives than the other (Table 6), which may have caused the difference in ML. Moreover, the extractives from Lipków had over seven times higher share of compounds with confirmed antifungal properties than those from Sieraków (Table 7), which may explain the smaller ML of wood caused by all four species of fungi in the samples from Lipków. This thesis is supported by the results of Szczepkowski (2010b), who found that oak wood with higher extractives content was less degraded by C. puteana, T. versicolor, and Laetiporus sulphureus (Bull.) Murrill.

4 Conclusion

Black cherry wood from the exotic range of the species in the forests of Kampinos National Park (Poland) is characterized by a quite significant average density and relatively strong mechanical properties, often exceeding the raw material from its native range. Regarding the tested structural, physical, and mechanical properties, P. serotina wood from the Kampinos Forest has comparable properties to wood from Latvia. Our results suggest that the species can take advantage of even minor differences in moisture and trophy of generally poor soils and habitats it has been introduced, resulting in the diversification of characteristics and properties of its semi-porous wood. This diversity is manifested in terms of the physical and mechanical properties of the wood, its chemical composition, and its resistance to biological decay. Regardless of the statistical significance of some of the results obtained, it seems necessary to carry out further research to verify the differences observed:

  • - Trees grown in moist soil with higher levels of total nitrogen and organic carbon (Podzol) produced denser and wider-ringed wood. Only the modulus of elasticity for static bending and the strength quality factor for this modulus differed significantly between plots, both of which were higher in trees from this particular plot.

  • - The plot from which the wood was obtained significantly impacted most of the parameters and indices of the wood fiber structure. Wood from Lipków grown in moister and more fertile soil showed better potential suitability for papermaking.

  • - Although there were no significant differences in the basic chemical composition of the wood between the plots, trees that grew in moister and more fertile Podzol soil produced wood with a higher extractives content. Specifically, the wood from these trees had over seven times higher content of compounds that possess antifungal activity, such as caproic acid, catechol, and 5-hydroxy-2,3-dimethyl-2-cyclopenten-1-one.

  • - Black cherry wood was classified as slightly durable (durability class 4) based on the highest mass loss of wood caused by T. versicolor. It was observed that regarding mean values all four tested fungi caused a lower mass loss of wood when it had a higher content of extractives, including compounds with antifungal properties.

Good mechanical properties combined with the aesthetic values of black cherry wood from KNP make it suitable for furniture, floorboards, veneers, marquetry, household appliances, and haberdashery wood at the non-industrial scale. In Poland, this wood is mostly used as fuel due to the shortage of raw materials with the required dimensions for the industry. However, this should not prevent the wood from being used in niche applications that fully exploit its good functional and aesthetic properties.