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Provenance trials are used to study the effects of tree origin on climate-growth relationships. Thereby, they potentially identify provenances which appear more resilient to anticipated climate change. However, when studying between provenance variability in growth behavior it becomes important to address potential effects related to site marginality in the context of provenance trials. In our study we focus on provenance-specific climate sensitivity manifested under marginal growth conditions. We hypothesized that the provenance effects are masked if trials are located at marginal environmental conditions of the natural species distribution. Under this framework, we investigate 10 Norway spruce provenances growing at two contrasting locations, i.e., a relatively drought-prone site in western Poland (at the climatic margin of Norway spruce's natural distribution) and a mild and moist site in north-eastern Poland (within its natural range). Combining principal component analysis with climate-growth relationships, we found distinguishable growth patterns and climate correlations among provenances. That is, at the mild and moist north-eastern site, we observed provenance-specific growth patterns and thus a varying drought susceptibility. In contrast, at the dryer western site, provenance-specific growth patterns were less pronounced and all provenances expressed a common and strong sensitivity to drought. Our results indicate that the genetic specificity of growth reactions diminishes toward the distributional margins of a given species. We conclude that the climate conditions at the margins of a species' distribution are constraining tree growth independently of tree origin. Because of this, the marginality of a site has to be considered when evaluating climate sensitivity of provenances within trials. As a consequence, the yet different responses of provenances to adverse growing conditions may synchronize under more extreme conditions in course of the anticipated climate change.

Fungi and oomycetes release volatiles into their environment which could be used for olfactory detection and identification of these organisms by electronic-nose (e-nose). The aim of this study was to survey volatile compound emission using an e-nose device and to identify released molecules through solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS) analysis to ultimately develop a detection system for fungi and fungi-like organisms. To this end, cultures of eight fungi (Armillaria gallica, Armillaria ostoyae, Fusarium avenaceum, Fusarium culmorum, Fusarium oxysporum, Fusarium poae, Rhizoctonia solani, Trichoderma asperellum) and four oomycetes (Phytophthora cactorum, P. cinnamomi, P. plurivora, P. ramorum) were tested with the e-nose system and investigated by means of SPME-GC/MS. Strains of F. poae, R. solani and T. asperellum appeared to be the most odoriferous. All investigated fungal species (except R. solani) produced sesquiterpenes in variable amounts, in contrast to the tested oomycetes strains. Other molecules such as aliphatic hydrocarbons, alcohols, aldehydes, esters and benzene derivatives were found in all samples. The results suggested that the major differences between respective VOC emission ranges of the tested species lie in sesquiterpene production, with fungi emitting some while oomycetes released none or smaller amounts of such molecules. Our e-nose system could discriminate between the odors emitted by P. ramorum, F. poae, T. asperellum and R. solani, which accounted for over 88% of the PCA variance. These preliminary results of fungal and oomycete detection make the e-nose device suitable for further sensor design as a potential tool for forest managers, other plant managers, as well as regulatory agencies such as quarantine services.

Key messageJuveniles and canopy trees may not exhibit similar nitrogen acquisition responses to soil temperature change caused by variation in snow cover over winter.The use of 15N tracer is a powerful tool for tracking the effects of variation in soil frost on plant nitrogen acquisition. While the responses of juvenile trees to environmental change are often used to infer the responses of canopy trees, the 15N enrichment responses of juveniles and mature canopy trees may not be comparable. We conducted a winter soil temperature manipulation study (snow exclusion, ambient snow or soil insulation) in a lowland Fagus sylvatica forest. 15N tracer was applied the following spring and the 15N enrichments of soil, juvenile and mature canopy trees were examined in late fall. Within canopy trees and juveniles, the relative treatment effects on 15N enrichment were consistent among all sampled tissues (roots, stem cores, leaves, buds and the current year’s shoot growth). For juveniles, 15N enrichment was highest under snow exclusion (coldest soil) and lowest under soil insulation (warmest soil), and lower 15N enrichment occurred under ambient conditions than under snow exclusion. For canopy trees, 15N enrichment also was highest under snow exclusion and lowest under soil insulation, but there was no difference in 15N enrichment between ambient conditions and the snow exclusion treatment. Therefore, our results indicate that sampling of juveniles may overestimate the nitrogen acquisition responses of mature trees to winter temperature variation.

The magnitude and frequency of soil frost events might increase in northern temperate regions in response to climate warming due to reduced insulation caused by declining snow cover. In temperate deciduous forests, increased soil frost severity can hamper tree growth and increase the mortality of fine roots, soil fauna and microorganisms, thus altering carbon and nutrient cycling. From single-site studies, however, it is unclear how the sensitivities of these responses change along continental gradients from regions with low to high snowfall. We conducted a gradient design snow cover and soil temperature manipulation experiment across a range of lowland beech forest sites to assess the site-specific sensitivity of tree growth and biogeochemical cycling to soil cooling. Even mild and inconsistent soil frost affected tree increment, germination, litter decomposition and the retention of added ¹⁵N. However, the sensitivity of response (treatment effect size per degree of warming or cooling) was not related to prevailing winter climate and snow cover conditions. Our results support that it may be valid to scale these responses to simulated winter climate change up from local studies to regional scales. This upscaling, however, needs to account for the fact that cold regions with historically high snowfall may experience increasingly harsh soil frost conditions, whereas in warmer regions with historically low snowfall, soil frost may diminish. Thus, despite the uniform biotic sensitivity of response, there may be opposing directions of winter climate change effects on temperate forests along continental temperature gradients due to different trends of winter soil temperature.

The radial growth of pedunculate oak ( ), a species often ecologically dominating European deciduous forests, is closely tied up with local environmental variables. The oak tree-ring series usually contain a climatic and hydrologic signal that allows assessing the main drivers of tree growth in various ecosystems. Understanding the climate-growth relationship patterns in floodplains is important for providing insights into the species persistence and longevity in vulnerable riverine ecosystems experiencing human-induced hydrology alteration. Here, we use 139 years long instrumental records of local temperature, precipitation, and water levels in the Dnipro River in Kyiv to demonstrate that the implementation of river regulation has decoupled the established relationship between the radial growth of floodplain oak and local hydro-climatic conditions. Before the river flow has been altered by engineering modifications of 1965-1977, the water level in the Dnipro River was the key driver of oak radial growth, as reflected in the tree-ring width and earlywood width. The construction of two dams has altered the seasonal distribution of water level diminishing the positive effect of high water on oak growth and subsequently reversing this trend to negative, resulting from a seasonal ground water surplus. The decrease in the correlation between oak growth indices and the river's water level in April-June was unprecedentedly rapid and clearly distinguishable among other changes in the growth-to-climate relationship. Our findings further demonstrate that trees growing in areas exposed to urban development are the most susceptible to downside effects of river regulation.

Key messageThe intra-annual variability in stem size of marginal beech population from south-eastern distribution range of beech in Poland is higher within than between populations.One of the key issues of the distribution of tree species is their ability to track environmental changes. European beech (Fagus sylvatica L.) is a species highly sensitive to extreme climatic events, because of its high phenotypic plasticity. In this study, we aim to determine the variability in stem size between and within marginal beech populations. Marginal populations of beech growing under uniform environmental conditions of provenance trial offer unique opportunity to detect adaptive differentiations driven by natural selection. In this work, we studied stem size variation recorded by automatic band dendrometers in four beech marginal populations growing in a common garden in the south-eastern distribution range of beech in Poland over the period 2016–2018. Strong climatic effects and weak provenance differences in seasonal stem size variation were observed. The provenances exhibited similar climate-related seasonal stem circumference variation. A high within-provenance variation was confirmed. Temperature of spring as well as temperature and precipitation of autumn were detected as key climatic parameters mostly for onset and end of stem size variation. Maximum stem size was mostly affected by the later end of its variation, which positively affected its duration. Climatic distance between beech provenances and provenance trial had a negligible effect on the variability in seasonal stem size variation between provenances. The evidence of weak inter-provenance and high intra-provenance variation in stem size changes observed in the south-eastern distribution range indicates that an individual-based approach could be a suitable strategy, when selecting for phenotypic plasticity.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Increased tree species diversity can promote forest production by reducing intra-specific competition and promoting an efficient unitization of resources. However, questions remain on whether and how mixed stands affect the dynamics of intra–annual xylem formation in trees, especially in subtropical forests. In this study, we randomly selected 18 trees from a monoculture of 63-year-old Masson pine (Pinus massoniana) growing in pure stands and mixed them with 39-year-old Castanopsis hystrix in Pinxiang, southern China. A total of 828 microcores were collected biweekly throughout the growing season from 2022 to 2023 to monitor the intra-annual xylem formation. Cell production started in early March and ended in late December and lasted about 281 to 284 days. Xylem phenology was similar between mixed and pure stands. During both seasons, the Masson pine in mixed stands showed higher xylem production and growth rates than those in pure stands. The Masson pine in mixed stands produced 45–51 cells in 2022 (growth rate of 0.22 cells day−1) and 35–41 cells in 2023 (0.17 cells day−1). Growth rate, and not growth seasons, determined the superior xylem growth in the mixed stands. Our study shows that after 39 years of management, Masson pine and C. hystrix unevenly aged mixed stands have a significant positive mixing effect on Masson pine xylem cell production, which demonstrates that monitoring intra-annual xylem growth dynamics can be an important tool to evaluate the effect of species composition and reveal the mechanisms to promote tree growth behind the mixing effect.

The intraspecific variation of climate–growth relationships observed on provenance trials results from among–provenance differences in phenotypic plasticity. Temporal variation in radial growth synchrony among provenances may be modified by adverse climatic/biotic conditions such as drought or insect defoliation. However, these factors can potentially diminish provenance–specific growth reactions and, consequently, prevent the identification of provenances with the highest adaptive potential. Thus, understanding the influence of major biotic conditions on provenance–specific climate–growth relationships seems to be important to anticipate climate change. To determine provenance–specific growth patterns in relation to climate conditions (drought), seed production (reproductive effort), and insect defoliation in a common garden of Scots pine (Pinus sylvestris L.), we applied dendroecological techniques to time–series of tree–ring widths and basal area increments. The long–term records of seed production and insect outbreaks from the local Scots pine stands were used to explain the potential effect of biotic factors on the temporal dynamics of radial growth synchrony. During a period of favorable growth conditions, Scots pine provenances showed a decline in inter–provenance synchronicity in growth patterns, while during years affected by severe soil water deficit and insect defoliation, they manifested high uniformity in growth dynamics. The long–term trend in growth synchrony among P. sylvestris provenances depend on both abiotic and biotic environmental factors. This gains significance following an introduction of the appropriate selection of tree provenances for climate–smart forestry.

Understanding species-specific adaptations to climate change, which exacerbates drought stress and heat waves, is crucial for sustainable forests. This knowledge can help in selecting potential alternatives for species such as Norway spruce (PIAB), which faces significant dieback in Central European forests. In this study, we focused on the adaptive capacity under novel climate of native silver fir (ABAL) and alien Douglas-fir (PSME) as potential alternatives for the most threatened old spruce stands in the Sudetes (Poland). We applied dendrochronological approach to track tree growth dynamics over the last 70 years and quantified how species resisted and recovered from the extreme drought events of 2003 and 2015. Our results revealed the highest potential to adapt to climate change manifested by ABAL. It displayed not only lower sensitivity to precipitation shortages but it also showed greater resilience and resistance to extreme drought compared to the remaining species. In addition, both ABAL and PSME could benefit from extended growing seasons. On the other hand, the non-native PSME outperformed both native species in terms of growth rate. However, it was similarly sensitive to summer precipitation as PIAB and showed low drought tolerance. Our findings supports a better understanding of species-specific differences in their adaptive potential and can help forest managers make informed decisions about species selection for climate change-adapted future forest.