Compression Wood Research Articles

MXene@Wood composite with absorption-dominated electromagnetic interference shielding performance through structural modification

Wood-based materials possess unique porous structure that are sustainable and green, showing great potential in many applications. Herein, MXene@Wood composites were prepared for electromagnetic interference shielding and thermal insulation, and their pore structure is monitored by compression of wood. Benefiting from the heterogeneous interface between MXene and the wood surface to enhance interfacial polarization, MXene@Wood presents a superior impedance match in cross-section compared to tangential-section. In the cross-section, MXene@Wood at a 30 % compression ratio achieves an absorption coefficient of 0.73 and a shielding effectiveness of 41.78 dB. After a 30 % compression ratio, MXene@Wood in cross-section achieves an absorption coefficient of 0.73 and a shielding effectiveness of 41.78 dB, it also exhibits wave absorption performance with a minimum reflection loss of −15.11 dB at 2 mm, meeting the commercial requirements. The effect of the pore structure of wood on shielding performance is further verified by finite element analysis. Furthermore, MXene@Wood also demonstrates excellent thermal insulation properties benefit to the reduced gas-phase heat transfer. This sustainable composite with electromagnetic shielding performance and thermal insulation properties largely expands the application area of wood.

Scott Blair Fractional-Type Viscoelastic Behavior of Clear Spruce Wood: Influence of Compression Wood on Power-Law Stiffness Parameters

In this paper, we investigate the influence of intrinsic compositional parameters on the viscoelastic compliance by employing three-point bending creep tests on clear, i.e., defect-free, spruce samples with a dimension of 15 × 15 × 280 mm3. In addition to the regular samples, a prominent wood variation was investigated: so-called compression wood, stemming from an adaptive response of the growing tree to maintain structural stability. Tests were conducted at constant ambient conditions: isothermal at 20 degrees Celsius and at a relative humidity of 65 percent. These conditions were also employed during sample conditioning, leading to an equilibrium moisture content of the specimens of approximately 12 percent. Hence, so-called basic creep properties were investigated. Furthermore, we show that the experimentally observed compliance can be exceptionally well-modeled by a Scott Blair fractional-type element, with the latter calibrated by a mere number of two independent material parameters. This allows to render rather explicit dependencies of these parameters with respect to the dry density and the volumetric content of the compression wood. There, the quasi-instantaneous stiffness of the employed Scott Blair element is an increasing function of the dry density. While this primary dependency is also observed for compression wood, the quasi-instantaneous stiffness is significantly smaller over the investigated density range.

Combining microscale ATR-FTIR and chemometrics to interpret degradation characteristics of earlywood, latewood, and compression wood in waterlogged archaeological pine wood

Interpreting the degradation characteristics of waterlogged archaeological wood (WAW) is crucial for the conservation of wooden cultural heritage. Generally, multidisciplinary diagnostic methods, including physical, micromorphological, and chemical approaches, are employed to evaluate the preservation state of WAW. However, primarily focused on the sample level, this methodology limits the understanding of the variability in degradation from a detailed perspective. In this paper, we adopted the in-situ microscale attenuated total reflectance Fourier transform infrared (ATR-FTIR) method to investigate the degradation variability in waterlogged archaeological Masson pine (Pinus massoniana) wood excavated from the ancient Chinese shipwreck Nanhai No. 1. Specifically, spectra of earlywood (EW), latewood (LW), and compression wood (CW) were extracted and combined with chemometrics to achieve rapid classification of their degradation levels. The micromorphological features of wood cell walls in conjunction with the ratios of lignin (A1509) and carbohydrate (A1370) peak areas were used to estimate the degradation levels. Unlike recent wood, moderate degradation in CW and severe degradation in EW and LW were classified in archaeological samples. The degradation levels were effectively determined through principal component analysis (PCA) and sparse partial least squares discriminant analysis (sPLSDA). The results suggest that chemometric analysis is a promising method to discern the variable degradation levels of archaeological wood at the tissue level. The methodologies developed in this study provide detailed insights into the degradation characteristics in WAW and improve the accuracy of evaluating the preservation state.

Tribological properties and related effects of compressed, thermally modified and wax-impregnated wood

AbstractThis paper develops a process for the preparation of modified wood with low friction and low wear for tribological applications such as self-lubricating bearings. Two types of wood, beech (Fagus sylvatica) and robinia (Robinia pseudoacacia), have been studied and the results compared with naturally lubricated native lignum vitae. The process developed consists of plasticisation followed by compression in a mould, thermal modification and subsequent wax impregnation. Plasticisation was carried out by conditioning the samples to a low equilibrium moisture content of 10%, followed by heating to a sample core temperature of 80 °C. This process protects the internal wood structure from mechanical damage during densification. After plasticisation, the wood was compressed in a press mould. A low springback effect (SBE), resulting in compression of up to 40%, was achieved by unloading the mould without opening it. This step optimises compressive strength and hardness. Subsequent heat treatment reduces thickness swelling by up to 85%. Finally, a wax impregnation was applied to reduce friction. Sliding wear tests on modified beech wood have shown that the lowest wear occurs in the cross-sectional orientation (load perpendicular to the fibre ends; rxt orientation). Sliding friction studies using a steel ball on a ball-on-disc tribometer showed that compressed and thermally modified samples impregnated with rapeseed wax or beeswax exhibited coefficients of friction in a range of 0.08 to 0.09. These values are almost four times lower than those of plain compressed wood and even lower than those of lignum vitae, which was used for plain bearings decades ago. This study clearly demonstrates the high potential of compressed, thermally modified and wax-impregnated wood.

What do trees reveal about the sliding of the lateral moraine of the Belvedere Glacier (western Italian Alps)?

The debris-covered Belvedere Glacier is an iconic place for investigating glacier dynamics and geomorphological processes typical of high mountain environments. Moreover, being located in an area highly suited to tourism, glacial and geomorphological hazards can evolve into risk scenarios. Particular attention has been paid during this research to the surge-type event that occurred at the beginning of the 21st century, and to the recent sliding of a lateral moraine nearby the chairlift station. Tree sampling was performed (19 trees on the lateral moraine; 10 undisturbed trees), and the results were compared with morphometric measurements on orthophotos of different years. Besides sampling trunks, the six available exposed roots (13 samples) from a tree located along the sliding niche were sampled to identify the exposure time. Morphometric measurements of the touristic trail dislocation indicate a sliding rate of 1.87 m/y – 1.98 m/y (2018–2023), while the regression rate of the sliding niche is 1.70 m/y (2021–2023). The age of trees along the trench is variable (14–49 years), as is the signal of compression wood, enhancing differentially the passage of the surge wave and the subsequent glacier downwasting. The beginning of root exposure occurred between 2017 and 2019, before the effective evidence of large fractures in the ground. Moreover, the roots show traumatic resin ducts in the period between 2020 and 2022, confirming the tree disturbance. In conclusion, the investigated events are recorded differentially in the sampled trees, especially in roots, anticipating the actual commencement of ground failure. A multidisciplinary approach, including remote sensing, field survey, and dendrogeomorphological analysis is essential to define the dynamics of complex systems.

PagKNAT2/6b regulates tension wood formation and gravitropism by targeting cytokinin metabolism.

Tension wood is a specialized xylem tissue associated with gravitropism in angiosperm trees. However, few regulators of tension wood formation have been identified. The molecular mechanisms underpinning tension wood formation remain elusive. Here, we report that a Populus KNOTTED-like homeobox gene, PagKNAT2/6b, is involved in tension wood formation and gravity response. Transgenic poplar plants overexpressing PagKNAT2/6b displayed more sensitive gravitropism than controls, as indicated by increased stem curvature. Microscopic examination revealed greater abundance of fibre cells with a gelatinous cell wall layer (G-layer) and asymmetric growth of secondary xylem in PagKNAT2/6b overexpression lines. Conversely, PagKNAT2/6b dominant repression plants exhibited decreased tension wood formation and reduced response to gravity stimulation. Moreover, sensitivity to gravity stimulation showed a negative relationship with development stage. Expression of genes related to growth and senescence was affected in PagKNAT2/6b transgenic plants. More importantly, transcription activation and electrophoretic mobility shift assays suggested that PagKNAT2/6b promotes the expression of cytokinin metabolism genes. Consistently, cytokinin content was increased in PagKNAT2/6b overexpression plants. Therefore, PagKNAT2/6b is involved in gravitropism and tension wood formation, likely via modulation of cytokinin metabolism.

Improved calculations of joints in anisotropic structural materials

Introduction. Contemporary methods for the design and calculation of building structures are often limited to the elastic stage of the material work. In order to analyze the stress-strain state of joints, it is necessary to take into account the properties of the material, as well as its operation under the load, including both elastic and non-linear stages. In this case, anisotropic materials, e.g. wood, represent a particular interest. Therefore, the paper presents a theoretical and practical study of the work, performed by wooden samples.Aim. To perform tests and numerical simulations for analyzing the stress-strain state and improve the calculations of anisotropic structural materials.Materials and methods. Compression tests of wooden samples, made of second-grade pine, were carried out along the fibers with fixed vertical compression stresses and strains. The tests were performed using a hydraulic press with a maximum load of 50 t. Strain gauge equipment was used to record strains and stresses. Based on the data of compression tests, the numerical simulation of the samples in the LIRA-SAPR and ANSYS software packages was performed.Results. According to the test results, the elastic stage of the compressed wood ranges up to 90 kN, followed by a transition to the plastic deformation. The performed numerical simulation of the samples in the LIRA-SAPR and ANSYS software packages demonstrated the convergence of the results. However, the ANSYS software package allows for a more detailed simulation and calculation of joints and structures. The comparison of distributions of vertical compression stresses σy, obtained in tests and ANSYS software package numerical simulation, proved the convergence of the results (discrepancy of less than 5 %). This confirms the effectiveness of using this software package for simulating the joints of anisotropic materials.Conclusions. The results of tests and numerical simulation showed the effectiveness of using the ANSYS software package to calculate complex joints of anisotropic structural materials. The convergence of the results is established for the elastic stage. An additional study is required to simulate the plastic stage.

Softwood branches modelled as a composite beam of compression and opposite wood: investigation of bending resistance

ABSTRACT Wood branches subjected to bending develop reaction wood to accommodate both tensile and compressive stresses. For softwood, such as Norway spruce and Scots pine, compression wood (CW) develops in the lower parts, while opposite wood (OW) develops on the upper parts of the branch. It is likely that the ratio of CW to OW is optimised for mechanical load bearing by nature. This hypothesis was tested with an analytical beam model using experimental data of stiffness and strength of CW and OW at CW fractions from 0 to 100%. It was found that there is indeed a maximum bending moment capacity around 35% CW, like literature values of CW content in softwood branches. For all compositions, compressive or tensile strength of OW was governing the behaviour.

Characterization of hygrothermal, gas pressure and stress characteristics for poplar wood during unilateral surface densification

Unilateral surface compression in wood presents notable benefits, including reduced wood volume loss and energy consumption, rendering a highly promising and extensive utilization. However, shortcomings in compressed wood arise due to unclear gas pressure, temperature, and moisture content distribution within the wood during hot pressing. In this paper, the temperature and pressure distribution were analyzed utilizing an optical fiber temperature and pressure measurement system within the wood during hot pressing. Moreover, the moisture content, stress and strain in each layer at the end of hot pressing were discussed extensively. The results showed that the wood surface layer (SL) and subsurface layer (SSL) maximum temperature values were similar even with different layer thicknesses. Under sealing conditions, SL and SSL temperatures were generally 6 ℃ to 7 ℃ higher compared to unsealing conditions. The gas pressure maximum value exhibited an opposite order, gradually transferring to the core layer (CL) and declining as the processing time extended. During compression treatment, moisture migrated from the hot end to the cold within the wood. The moisture content displayed significant differences between the middle and end parts of the wood under unsealed conditions, with the disparity becoming more pronounced further away from the hot end. The transition region of the compressed wood served as a stress concentration area, experiencing the highest levels of stress. The dense region followed with the second highest stress levels, while the un-densified region exhibited the least amount of stress. Under the same process parameters, the thickness had little influence on the distribution of dense layers.

A COBRA family protein, PtrCOB3, contributes to gelatinous layer formation of tension wood fibers in poplar.

Angiosperm trees usually develop tension wood (TW) in response to gravitational stimulation. TW comprises abundant gelatinous (G-) fibers with thick G-layers primarily composed of crystalline cellulose. Understanding the pivotal factors governing G-layer formation in TW fiber remains elusive. This study elucidates the role of a Populus trichocarpa COBRA family protein, PtrCOB3, in the G-layer formation of TW fibers. PtrCOB3 expression was upregulated, and its promoter activity was enhanced during TW formation. Comparative analysis with wild-type trees revealed that ptrcob3 mutants, mediated by Cas9/gRNA gene editing, were incapable of producing G-layers within TW fibers and showed severely impaired stem lift. Fluorescence immunolabeling data revealed a dearth of crystalline cellulose in the tertiary cell wall (TCW) of ptrcob3 TW fibers. The role of PtrCOB3 in G-layer formation is contingent upon its native promoter, as evidenced by the comparative phenotypic assessments of pCOB11::PtrCOB3, pCOB3::PtrCOB3, and pCOB3::PtrCOB11 transgenic lines in the ptrcob3 background. Overexpression of PtrCOB3 under the control of its native promoter expedited G-layer formation within TW fibers. We further identified 3 transcription factors that bind to the PtrCOB3 promoter and positively regulate its transcriptional levels. Alongside the primary TCW synthesis genes, these findings enable the construction of a 2-layer transcriptional regulatory network for the G-layer formation of TW fibers. Overall, this study uncovers mechanistic insight into TW formation, whereby a specific COB protein executes the deposition of cellulose, and consequently, G-layer formation within TW fibers.

The hygroscopic behavior of surface compressed wood in response to superheated steam treatment at varying steam pressures

Superheated steam treatment has been shown to be an efficient strategy for enhancing the dimensional stability of compressed wood. This study evaluated the hygroscopic behavior of surface compressed (SC) wood subjected to superheated steam treatment (SHTSC wood) at varying steam pressures (0.1 MPa, 0.3 MPa, 0.5 MPa, and 0.7 MPa). As the steam pressure increased, the equilibrium moisture content (EMC) of SHTSC wood showed a gradual decrease throughout the hygroscopic range, indicating improved hygroscopic stability. The reduction in EMC for SC wood was associated with a decrease in polylayer moisture content (Ms) from 0% to 95% RH, while the EMC reduction for SHTSC wood was attributed to the combined effect of diminished monolayer (Mh) and Ms. The superheated steam treatment resulted in a range of chemical alterations in the SHTSC wood, including a decrease in hemicelluloses content and the quantity of sorption sites (–OH, C–O groups). Concurrently, there was a relative augmentation in the content of cellulose and extractives, alongside a heightened degree of lignin cross-linking. Furthermore, the superheated steam treatment also affected the cellular structure of the SHTSC wood, resulting in an increased ratio of macropores to mesopores, as well as the formation of microcracks within the cell wall. These changes became more pronounced as the steam pressure elevated, contributing to the reduced hygroscopic characteristics and improved dimensional stability of SHTSC wood.

Cross-field pitting characteristics of reaction wood in the stem wood of Pinus merkusii and Agathis loranthifolia

This research investigated and compared the pitting type, pit number (PN), and pit diameter (PD) in the cross-field of compression wood (CWD), lateral wood (LWD), and opposite wood (OWD) in stem wood of Pinus merkusii and Agathis loranthifolia growing in Indonesia. Identification and quality evaluation were done using optical and scanning electron microscopy. A piceoid pit type was observed in the CWD of both species. The LWD and OWD of P. merkusii showed window-like and pinoid pits, whereas those of A. loranthifolia showed taxodioid and cupressoid pits. The PN and PD were the smallest in CWD of both species. In P. merkusii, LWD and OWD showed similar PN values, and PN in all parts increased from the pith to the bark. In A. loranthifolia, LWD had higher PN than in OWD, and PN in CWD and LWD decreased from near the pith to the bark, whereas in OWD, it increased. All parts of P. merkusii and CWD and OWD of A. loranthifolia showed a positive correlation between PN and radial tracheid diameter, whereas LWD showed a negative correlation. In P. merkusii, the PD of LWD approximated that of OWD, whereas, in A. loranthifolia, LWD had a larger PD than that exhibited by OWD.

Chemical reagent for detecting tension wood in selected tree species

Reaction wood is a wood defect arising during the growth of the tree in the part of the trunk that is under tension (hardwood tree species) or compression (coniferous tree species). Beech (Fagus sylvatica L.) tension wood has different anatomical and chemical characteristics than normal (opposite) wood. The difference in density is conditioned by the percentage of the gelatinous layer (G-layer). Fibre cells in reaction beech wood have a different cell wall structure and a different chemical composition. Tension wood cannot be detected by the naked eye. It is only possible to assume its occurrence based on the macroscopic characteristics of the logs, such as a woolly surface, taper or eccentric pith, and so forth. However, these are imprecise and unreliable methods that have minimal effectiveness, especially when shortening the length of the log for cut-outs. This study aimed to create a unique chemical reagent for the detection of tension wood in logs and timber and wood products immediately. The present research can contribute to the mitigation of flaws resulting from the reaction of wood in timber production while addressing noticeable constraints in manufacturing, such as energy resources and the availability of wood raw materials. This can be achieved through the efficient identification of reaction wood in materials. The colour change is only temporary and will fade over time. After the chemical reagent has dried on the surface, the surface can be milled. The colour change extends to a depth of approx. of 3 to 5 mm.

Minimizing the polymer content of compressed transparent synthetic wood from renewable biomass sources: A comparative life cycle assessment

Transparent wood derived from renewable biomass resources has an enormous potential for utilizing in constructions, electrons devices, energy storage, etc. However, due to its high polymer content, the currently described transparent wood could not be developed in a sustainable manner. Herein, a feasible strategy for synthesizing compressed transparent wood was proposed to minimize the content of polymerized poly(methyl methacrylate) in composites, involving the poly(methyl methacrylate) partial-filling into the delignified wood and densification. This synthesis method prompted a substantial reduction of poly(methyl methacrylate) content (58.8%) in the obtained compressed transparent wood contrasted with the typical transparent wood (91.8% poly(methyl methacrylate) content). Besides, an ideal optical transmittance of 77.9% with 0.4 mm thickness and an optical haze of 49.2% with 0.7 mm thickness at 800 nm wavelength were achieved. Also, the improved tensile strength and flexural strength of compressed transparent wood were up to 85.0 MPa and 145.3 MPa, respectively. Additionally, a comparative life cycle assessment was conducted to assess the environmental impacts. The total environmental impact score was separately reduced by 23%, and 28% compared to the typical transparent wood and poly(methyl methacrylate) polymer, suggesting the feasibility of sustainable manufacture of transparent wood materials by decreasing polymer content. The compressed transparent wood also showed much lower thermal conductivities (0.28–0.31 W/mk) than glass and contributed to offering uniform illumination.

Analysis of Deformation Fixation of Thermally Compressed Scots Pine (Pinus sylvestris L.)

Heat treatment effectively inhibits the water absorption recovery of compressed wood. To elucidate this phenomenon, we prepared compressed pine and thermally compressed pine (heartwood and sapwood) using the hot pressing method at 160 °C, 180 °C, 200 °C, and 220 °C. The effects of chemical components, swelling stresses, and monosaccharides on modified wood recovery were investigated using regression analyses. Notably, the recovery of both compressed heartwood and sapwood during water absorption declined from 18.89% to 2.66% and from 58.40% to 1.60%, respectively, after heat treatment. Similarly, the swelling stresses of the compressed heartwood and sapwood at 220 °C, respectively, ranged from 0.693 MPa to 0.275 MPa and from 0.783 MPa to 0.330 MPa. These were close to the values of untreated heartwood (0.175 MPa) and sapwood (0.225 MPa). Regression functions indicated that the recovery of compressed wood is chemically dependent on hemicellulose and mechanically related to swelling stress. For monosaccharides, regression functions indicated that modified heartwood recovery primarily relied on mannose, whereas modified sapwood recovery was remarkably affected by mannose and xylose. This confirmed that the pyrolytic monosaccharides in hemicellulose promoted stress relaxation, which induced the deformation fixation of thermally compressed wood.

Determination of lignin composition in compression wood-like reaction wood of angiosperm Gardenia jasminoides by pyrolysis–gas chromatography–mass spectrometry

Abstract Using pyrolysis–gas chromatography–mass spectrometry, the lignin composition was analysed in normal and reaction wood samples grown at three stem inclination angles in Gardenia jasminoides, which forms compression wood-like reaction wood. Lignin content among the samples was not significantly different. However, the reaction wood samples with larger stem inclination angles showed a lower syringyl/guaiacyl ratio. In conclusion, the degree of inclination affected the lignin composition in G. jasminoides reaction wood, and qualitative changes in lignin might be necessary to mechanically support the stems in this species.

Integrating Dendrogeomorphology into Stress–Strain Numerical Models: An Opportunity to Monitor Slope Dynamic

Monitoring systems are recognized worldwide as fundamental tools for landslide risk management. However, monitoring can be difficult when dealing with large slopes in forested areas. In these situations, dendrogeomorphology can offer a low-cost and low-impact alternative for providing distributed information with an annual temporal resolution. The present study is a first attempt to integrate dendrometric and dendrogeomorphic data into a numerical finite difference model, in order to simulate the stress–strain behavior of the tree-slope system. By using a parametrical approach, the capability of the numerical model to effectively reproduce the tree stem anomalies (i.e., tilting angle, J-shaped feature, and internal stresses causing tree-ring growth anomalies such as eccentric growth and reaction wood) was verified, and the target parameters for the model calibration were identified based on a sensitivity analysis, which emphasized the relevance of the wood deformability; moreover, the interpretation of results allowed to point out different peculiarities (in terms of type of deformation, falling direction, and distribution of internal stresses) for different slope conditions (kinematics and depth of the failure surface) and different zones of the landslide (head scarp, main body, and toe). Afterwards, the modeling approach was applied to the Val Roncaglia landslide (Northen Italy), which involves a complex roto-translational kinematics, characterized by multiple sliding surfaces. The simulated stem anomalies showed good agreement with the ones arising from onsite dendrometric surveys, and they confirmed the conceptual model of the landslide, enabling the planning of further specific investigations. Moreover, the capability of the model in reproducing the tilting angle of trees, if correlated to their eccentricity, could provide a quite long time series (over more than 50–60 years) of the landslide reactivation and allow the use of dendrochronological data for the model calibration, thereby enhancing slope dynamic monitoring and landslide risk management.

Protein content and antioxidant enzymes activity in reaction wood of poplar and their response to different levels of sustained bending stress

Protein content and antioxidant enzymes activity in reaction wood of poplar and their response to different levels of sustained bending stress

Interclonal variability in sensitivity to wind breakage: Comparative analysis of the mechanical behaviour of stems of two Hevea clones

The rubber tree (Hevea brasiliensis) is the main source of natural rubber production, with more than 14 million tonnes produced each year. Unfortunately, throughout their economic lifespan on the plantation (between 35 and 40 years), heveas trees are sensitive to wind damage, especially trunk breakage. Over a 30-year period, it is estimated that losses due to the wind breakage of tree stems reach nearly 40%. Industrial hevea plantations are organized in monoclonal plots. Clones are selected based on their productivity, disease resistance, etc., but not for their mechanical behaviour or sensitivity to wind-induced breakage, as breeders lack the appropriate tools to assess these criteria. Field observations highlight variations among clones in their susceptibility to wind breakage, underscoring the increased importance of evaluating mechanical criteria. Among the known causes of these differences in Hevea trees are competition between latex production and growth, crown shape and the presence of tension wood. In this article, we investigated the mechanical behaviour of the stems of two Hevea clones. One, IRCA825, is recognized as very sensitive, while the other, IRCA41, is known for its resistance to wind breakage. We measured biomechanical parameters such as trunk bending stiffness (EI), green wood stiffness (E) and modulus of rupture (MOR). To assess these parameters, we performed bending tests until breakage on standing trees of clonal fields in Ivory Coast, followed by wood characterisation tests in laboratory. A comparative analysis of the bending tests revealed that clones IRC825 and IRCA41 exhibit equivalent trunk bending stiffness. Nevertheless, IRCA41 differs from IRCA825 by having higher green wood stiffness and breaking strength, attributes that mainly explains its higher wind resistance. Comparative analysis of the wood structure indicated that the differences in wood stiffness and breaking strength are mainly attributed to the higher wood density in IRCA41 compared to IRCA825, with no discernible differences in microfibril angle and specific modulus.

Divergent patterns of landslide activity and triggering factors at a local scale of a single mountain massif (Island Beskid Mts., Western Carpathians, Poland)

Landslide protection and mitigation are critical issues in many regions worldwide, where lives and livelihoods depend on correctly determining landslide hazards. However, local differences in the response of landslide slopes to meteorological or seismic triggering factors can decrease the performance of landslide models and forecasts. Thus, recognising and understanding spatial patterns of landslide activity at a local scale should be one of the priorities of landslide research. In this study, we analyse the activity and triggering factors of two landslides in one mountain massif, <2 km apart, in the Western Carpathians, Poland. We analysed 61-year-long (1959–2019) records of the activity of study landslides, i.e. dendrochronological reconstruction based on ring eccentricity and compression wood dated in 65 specimens of European silver fir (Abies alba). We compared the dendrochronological proxy of landslide activity at two study slopes with precipitation and earthquakes in the study area. Based on statistical correlations with 560 precipitation indicators, we found that the similarities between the two study landslides include only the direct triggers in June–July and March. The Wiśnia landslide, unlike Hajdowska, can also be triggered by precipitation in October. However, the main difference between the study landslides lies in the preparatory precipitation. Hajdowska shows significant dependence from precipitation of the previous December and current February, while at the Wiśnia study site, the preparatory precipitation is less important and covers the previous October–November and current January. Our results show that although study landslides could be reactivated at one time by similar direct triggers of spring or summer, such simultaneous reactivation would require preconditions of antecedent precipitation of the previous winter half-year (October–March) different for each landslide. Suppose, the requirements of antecedent precipitation are fulfilled only for one of the landslides during the winter half-year. In that case, the other will remain inactive despite the later occurrence of a shared direct trigger in spring or summer. The example of Hajdowska and Wiśnia shows that significant differences in landslide activity, hazard and triggering factors can exist even at the local scale. We argue that omitting even such subtle, unevident differences in the conditions of landslide activity leads to errors in landslide modelling and forecasting. For example, linking Hajdowska and Wiśnia landslides with one precipitation threshold or model of slope instability based on their adjacent location would not be effective in predicting reactivations. The precision of landslide modelling and forecasting depends on the accuracy of preceding analyses of landslide activity and triggering factors. We argue that in the case of the two adjacent landslides studied the divergent patterns of their activity and triggers would not be revealed without analysing long-term (> 60 years long) data sets.