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Cherry spruce rust in the Wigry National Park and Suwałki Forest District: cone infestation and its implications
Abstract Thekopsora areolata and Chrysomyxa pirolata are pathogens preferentially infesting Norway spruce cones and lead to the complete failure of spruce seed yield. Thus, the presence of seed-injuring pathogens may be a crucial factor driving close association between cherry spruce rust occurrence on trees and limited natural regeneration of the preferred host. However, a major uncertainty remains as to which pathogens are responsible for cone infection and reduced seed viability, resulting in impeded renewal of young trees. Our study aims to investigate whether T. areolata or C. pirolata presence on the Norway spruce cones was responsible for cherry spruce rust in three sites within the Wigry National Park (one site) and the Suwałki Forest District (two sites) in North-Eastern Poland. We harvested randomly five infested Norway spruce cones from each location and analysed them to verify specific pathogen occurrence. We analysed rDNA fragments such as ITS regions and 28S to precisely identify the disease causal agent on the cones and estimate the potential of genetic diversity of the analysed fungus species. Thekopsora areolata was identified as the main fungus promoting cherry spruce rust, suggesting that host species regeneration is constrained by this pathogen’s distribution. We assumed that the apparent cherry spruce rust presence and lack of Norway spruce natural regeneration likely result from cone infection and the availability of healthy, high-quality seeds. Moreover, the occurrence of cherry spruce rust may explain the challenges associated with the deficit of seeds used for the artificial regeneration of spruce stands.
Climate warming, ecological dynamics and nature conservation drive tree diversity in Wigierski National Park, Poland
In response to ongoing climate warming, tree species adapted to colder climates are expected to shift their geographic ranges northward. Within the framework of long-term ecological monitoring in Wigry National Park (northeastern Poland), observed changes in forest biocenoses reflect the combined influence of climate change and natural ecological dynamics. This study compares dendroflora composition and diversity between two monitoring periods, 2011 and 2024, as part of an ongoing effort to track climate-related ecological shifts. Tree observations and measurements were carried out using concentric circular plots. In the largest plots, all trees with a diameter at breast height (d.b.h.) ≥ 12 cm were recorded by species, and their d.b.h. was measured. In the smaller plots, all trees with a d.b.h. ≥ 2 cm and < 2 cm but taller than 30 cm were similarly identified and measured. Data were recorded with Field-Map software integrated with an electronic calliper. The species-level taxonomic data, individual counts and basal area per species and plot were used to calculate biodiversity indices. Over the 13-year interval, a marked increase in overall dendroflora diversity was observed. Notably, the dominance of canopy-forming conifers – Pinus sylvestris and, to a lesser extent, Picea abies – measured as the proportion of individuals or stem density, has declined. This decline of coniferous species has been accompanied by an increase in the abundance and diversity of broadleaved deciduous species, including Tilia cordata, Quercus robur, Betula pendula, and Acer platanoides. Other thermophilous deciduous taxa also exhibited upward trends in both presence and abundance. Furthermore, the exponential of Shannon entropy, reached the highest value when evergreen conifers comprised 35% of the stand composition in 2011 and 18% in 2024. This finding suggests that maximum dendroflora diversity reaches its highest level at an intermediate proportion of conifers presence, rather than under conifers dominance or absence. Collectively, the processes occurring in Wigierski National Park illustrate the gradual shift in ecotonal forest ecosystems from cold-adapted coniferous species to broadleaved deciduous taxa due to ongoing climate change.
Regenerating oak trees with different techniques has long-lasting legacy effects on root development, stem growth and plant physiology
Abstract Regeneration methods can have legacy effects on tree physiology and growth via differential root development and affect forest climate sensitivity. However, there are few studies providing a long-term perspective on how forest regeneration techniques affect root development and physiology of established seedlings that have grown into trees. This study investigates leaf carbon (C), oxygen (O) and nitrogen (N) isotope composition (δ13C, δ18O, δ15N) and stem growth in ⁓20-year-old oak (Quercus robur L.) trees regenerated in two stands by three methods: direct acorn sowing in the field, bare-root planting preceded by root pruning and containerized planting with the root plug intact. Leaf isotopic values were measured three times during summer, together with tree-ring δ13C. Ground penetrating radar analyses indicated that acorn sowing resulted in deep root systems compared shallower root systems of bare-root and containerized trees. Higher annual basal area increment was observed in acorn-sown oaks than in bare-root or containerized oaks. Leaf δ13C, δ18O and δ15N values varied among regeneration origins. Trees with deeper root systems consistently showed lower leaf δ18O values, regardless of the season, which suggests higher uptake of water from deep soil horizons and better leaf hydration. In contrast, oaks with shallower root systems exhibited higher leaf δ18O values, which were positively related with δ13C. More negative leaf δ15N values in shallow-rooted oaks pointed to higher water stress. A lack of correlation between N concentration and intrinsic water-use efficiency (iWUE) for containerized trees suggests that variability in stomatal conductance rates governed iWUE in these shallow-rooted oaks. The lack of correlation between leaf and tree-ring δ13C supports that leaf physiological processes do not necessarily explain latewood isotopic composition. We conclude that regeneration techniques have long-lasting, carry-over effects on root development, plant physiology and tree growth. The findings underscore the importance of considering tree regeneration origin and root distribution when assessing the impact of climate change on tree performance and forest vigor.
Identification of genetics and hormonal factors involved in Quercus robur root growth regulation in different cultivation system
AbstractUnderstanding the molecular processes and hormonal signals that govern root growth is of paramount importance for effective forest management. While Arabidopsis studies have shed light on the role of the primary root in root system development, the structure of root systems in trees is considerably more intricate, posing challenges to comprehend taproot growth in acorn-sown and nursery-cultivated seedlings. In this study, we investigated Quercus robur seedlings using rhizotrons, containers, and transplanted containers to rhizotrons, aiming to unravel the impact of forest nursery practices on processes governing taproot growth and root system development. Root samples were subjected to RNA-seq analysis to identify gene expression patterns and perform differential gene expression and phytohormone analysis. Among studied cultivation systems, differentially expressed genes (DEGs) exhibited significant diversity, where the number of co-occurring DEGs among cultivation systems was significantly smaller than the number of unique DEGs in different cultivation systems. Moreover, the results imply that container cultivation triggers the activation of several genes associated with linolenic acid and peptide synthesis in root growth. Upon transplantation from containers to rhizotrons, rapid enhancement in gene expression occurs, followed by gradual reduction as root growth progresses, ultimately reaching a similar expression pattern as observed in the taproot of rhizotron-cultivated seedlings. Phytohormone analysis revealed that taproot growth patterns under different cultivation systems are regulated by the interplay between auxin and cytokinin concentrations. Moreover, the diversification of hormone levels within the root zone and cultivation systems allows for taproot growth inhibition and prompt recovery in transplanted seedlings. Our study highlights the crucial role of hormone interactions during the early stages of taproot elongation, influencing root system formation across.
Comparative RNA sequencing-based transcriptome profiling of Quercur robur: specific sets of genes involved in taproot and lateral roots emergence
Abstract Root development is well recognized in model plants, with many studies focusing only on primary root growth or lateral root initiation. However, taproot vs lateral root development has rarely been explored using molecular tools, and even less is understood about how the molecular processes engaged in taproot elongation shape the emergence of lateral roots in trees in the time-dependent manner. We address how gene expression is associated with elongation of taproot and lateral root formation of Quercus robur L. In addition, we have analyzed how the exogenous application of hormones and inhibitors shapes the root architecture. We also revealed that lateral root formation and emergence corresponds to expression of genes at specific taproot length points. Therefore, our study suggests that the pattern of gene expression in the taproot tips is involved in the shaping of lateral root growth. In addition, we have shown that lateral roots are characterized by a set of genes that are distinct from those expressed in the taproot tips. Insights from this study contribute to better understanding root development in trees.
Gymnosperms demonstrate patterns of fine‐root trait coordination consistent with the global root economics space
Abstract Gymnosperms encompass a diverse group of mostly woody plants with high ecological and economic value, yet little is known about the scope and organization of fine‐root trait diversity among gymnosperms due to the undersampling of most gymnosperm families and the dominance of angiosperm groups in recent syntheses. New and existing data were compiled for morphological traits (root diameter, length, tissue density, specific root length [SRL] and specific root area [SRA]), the architectural trait branching ratio, root nitrogen content [N] and mycorrhizal colonization. We used phylogenetic least squares regression and principal component analysis to determine trait–trait relationships and coordination across 66 species, representing 11 of the 12 extant gymnosperm families from boreal, temperate, subtropical and tropical biomes. Finally, we compared the relationship between family divergence time and mean trait values to determine whether evolutionary history structured variation in fine‐root traits within the gymnosperm phylogeny. Wide variation in gymnosperm root traits could be largely captured by two primary axes of variation defined by SRL and diameter, and root tissue density and root nitrogen, respectively. However, individual root length and SRA each had significant correlations with traits defining both main axes of variation. Neither mycorrhizal colonization nor root branching ratio were closely related to other traits. We did not observe a directional evolution of mean trait values from older to more recently diverged gymnosperm families. Synthesis. Despite their unique evolutionary history, gymnosperms display a root economic space similar to that identified in angiosperms, likely reflecting common constraints on plants adapting to diverse environments in both groups. These findings provide greater confidence that patterns observed in broad syntheses justly capture patterns of trait diversity among multiple, distinct lineages. Additionally, independence between root architecture and other traits may support greater diversity in below‐ground resource acquisition strategies. Unlike angiosperms, there were no clear trends towards increasingly thin roots over evolutionary time, possibly because of lower diversification rates or unique biogeographic history among gymnosperms, though additional observations are needed to more richly test evolutionary trends among gymnosperms.
Climate legacy in seed and seedling traits of European beech populations
Tree species’ ability to persist within their current distribution ranges is determined by seed germination and seedling growth. Exploring variation in these traits in relation to climatic conditions helps to understand and predict tree population dynamics, and to support species management and conservation under future climate. We analyzed seeds and seedlings of 26 European beech populations from the northeastern boundary of the species range to test whether: 1) adaptation to climatic conditions is reflected in depth of dormancy and germination of seeds; 2) climatic characteristics of origin predictably affect seedling traits. The variation in seed dormancy and germination in a laboratory test, and seedling growth and morphology traits in a nursery common-garden test was examined. Populations originating from warmer and drier sites (mostly from the northern region), compared to those from the opposite end of climatic gradient, germinated later, with a lower success, and produced seedlings with shorter and tougher roots. They had deeper dormancy and poorer seed germination capacity, and are likely more vulnerable to environmental changes. The climatic conditions at the origin shape the intraspecific variation of seed germination and seedling traits, and may limit regeneration from seed and affect adaptation potential of beech to increasing temperatures and decreasing precipitation.
Shields against pollution: phytoremediation and impact of particulate matter on trees at Wigry National Park, Poland
Root anatomical adaptations of contrasting ectomycorrhizal exploration types in Pinus sylvestris and Quercus petraea across soil horizons
Abstract Aims The anatomical characteristics of ectomycorrhizal exploration types in response to soil variability remain insufficiently understood. We examined the root anatomy of contact and long-distance exploration types in Pinus sylvestris and Quercus petraea, species with distinct ecological needs, across different soil horizons. Methods The diameter of ectomycorrhizal roots, the root absorptive traits i.e. proportion of cortex and mantle area, the percentage stele in the diameter, and the weighted average diameter of vessels (Ra) in the ectomycorrhizas were measured within ectomycorrhizas collected from organic and mineral soils across the soil profile. Results The absorptive traits varied along soil horizons, in which water and nutrient availability changed inversely. The proportion of cortex was associated with exploration type, but was not specific to tree species. However, the ectomycorrhizal diameter and the percentage of mantle within the root forming contact exploration type of P. sylvestris showed no variation among soil horizons. In contrast, the soil horizon significantly influenced all root anatomical traits in the contact exploration type of Q. petraea by enhancing the contribution of the absorption area of the root area, mainly in the illuvial horizon, but reaching the smallest value in the organic horizon. The Ra and the cell wall thickness of the vessels were strongly dependent on tree species. With increasing soil depth, Ra in Q. petraea increased, and stele proportion in root diameter decreased. Conclusion The results suggest that water acquisition traits differ among tree species, but traits associated with nutrient absorption (proportion of cortex and mantle area) within specific soil horizons are closely related to the ectomycorrhizal exploration type.