Coniferous Forest Trees Research Articles

Research progress on cambium activity and radial growth dynamics monitoring of coniferous species

The radial growth of trees plays a crucial role in determining forest carbon sequestration capacity. Understanding the growth dynamics of trees and their response to environmental factors is essential for predicting forest's carbon sink potential under future climate change. Coniferous forest trees are particularly sensitive to climate change, with growth dynamics responding rapidly to environmental shifts. We collected and analyzed data from 99 papers published between 1975 and 2023, and examined the effects of exogenous factors (such as temperature, water, and photoperiod) and endogenous factors (including tree age and species) on cambial activity and radial growth in conifers. We further explored the mechanisms underlying these effects. The results showed that climate warming had the potential to advance the onset while delayed the end of xylem differentiation stages in conifers in temperate and boreal regions. Water availability played a crucial role in regulating the timing of cambial phenology and wood formation by influencing water potential and cell turgor. Additionally, the photoperiod not only participated in regulating the start and end times of growth, but also influenced the timing of maximum growth rate occurrence. Future climate warming was expected to extend the growing season, leading to increase in growth of conifers in boreal regions and expanding forests to higher altitudes or latitudes. However, changes in precipitation patterns and increased evapotranspiration resulting from temperature increases might advance the end of growing season and reduce growth rate in arid areas. To gain a more comprehensive understanding of the relationship between radial growth and climatic factors, it is necessary to develop process-based models to elucidate the physiological mechanisms underlying wood formation and the response of trees to climatic factors.

Comparing field measurements and annotations as training data for UAV-based detection of standing dead trees in coniferous forest

ABSTRACT Deadwood provides a habitat for a large number of species and acts as a significant carbon storage. Thus, deadwood mapping allows planning various actions related to biodiversity conservation and forest management. Airborne laser scanning (ALS) provides an efficient means for monitoring large forested areas and is thus a potential method for deadwood mapping. Machine learning (ML) can be used for automating deadwood detection from ALS data. However, ML requires training data, collecting of which is laborious using field measurements. This study inspected the feasibility of training data manually annotated from aerial images for the mapping of individual standing dead trees. The standing dead trees were mapped from an ALS dataset collected with an unmanned aerial vehicle (UAV). The study was carried out by performing ML-based standing dead tree detection using annotated training data and field-measured training data, and comparing the performances of the models trained on these two datasets. The study found that using annotated training data improves the performance of standing dead tree detection due to its higher availability compared to field-measured data. For large trees (height > 14 m), the precision, recall, Cohen’s kappa score, and Matthews correlation coefficient achieved by the best classifier trained on annotated data were 0.23, 0.48, 0.17, and 0.20, respectively. In comparison, the corresponding metrics for the best classifier trained on field-measured data were 0.14, 0.52, 0.04, and 0.13. Annotated standing dead tree data is not a representative sample of the true standing dead tree population, as small trees and trees without crowns (snags) can often not be identified from aerial images. However, the study found that identifying such trees is challenging even when using field-measured training data, and thus using annotated training data does not bias results. In general, the results of the study showed that ALS-based standing dead tree detection should focus on the detection of large trees.

Broadleaved trees enhance biodiversity of the understorey vegetation in boreal forests

Understorey vegetation constitutes a remarkable part of the total biodiversity of boreal forests. Mixing broadleaved trees in coniferous forests has been shown to enhance vascular plant abundance and species richness, while high stand density has a counteracting effect. However, more information is needed on how environmental factors modify these biodiversity responses.We investigated how the proportion of broadleaved trees of total basal area, tree species richness, stand density, and shrub cover were reflected in the number of vascular plant species and percentage cover of herbs and bilberry (Vaccinium myrtillus). We also studied the response of site fertility indicators, i.e. C:N ratio and extractable calcium concentration in the soil organic layer, to broadleaved species in mixed-forests.The study was based on the data of understorey vegetation, soil, and stand properties in forests on mineral soil, inventoried on a systematic sample plot network in Finland in 2006. We used a subset of 307 plots in the hemi-southern and middle boreal zones and divided the plots either to xeric or mesic types. We used generalized additive models in analysing the data.Birches (Betula sp.) were the main broadleaved species. Vascular species richness and herb cover generally increased with increasing proportions of broadleaved trees and tree species number both on mesic and xeric sites but decreased with increasing stand density on mesic sites. An increase in proportion of broadleaved trees and stand density resulted in decreased bilberry cover in the southern boreal zone, probably due to stand shading, but in increased cover in the middle boreal zone. Vegetation responses to increasing shrub cover often showed unimodal shape. As increase of proportion of broadleaved trees correlated positively with calcium and negatively with C:N of the organic layer, we suggest that nutrient input from easily decomposable birch leaf litter promotes species richness and herb cover via improved nutrient availability in the soil.Our results indicate that many stand characteristics determining understorey biodiversity can be directed by forest management regimes. Generally, slight increase of broadleaved trees benefitted the understory plant richness, given that stand density is not too high. Because site type and zone controlled many responses, we suggest that it would be beneficial to have habitat and zone-specific instructions in forest management practices that conserve understorey vegetation and its multi-purpose ecosystem services.

Effect of Tree Size Heterogeneity on the Overall Growth Trend of Trees in Coniferous Forests of the Tibetan Plateau

Tree growth is under the combined influence of abiotic and biotic factors. Trees with different sizes may respond differently to these factors, implying that tree size heterogeneity may also modulate the overall growth trend. To test this hypothesis, we focused on the radial growth trends of natural subalpine forests on the Tibetan Plateau. We first extended the iterative growth model (IGM) to the tree ring scale (IGMR) to test the applicability of the generalized metabolic growth theory to tree growth. As predicted by the IGMR, the radial growth of trees at the aggregate scale is constrained by a unimodal pattern. Using the IGMR, we reconstructed the historical best growth trajectory (HBGT) of trees within the same community based on the tree with the largest radius and/or longest age in the community. From the average difference between the HBGT and the current radial growth rate of trees with different sizes, we constructed an indicator that can measure the overall variation in tree radial growth. Based on this indicator, we found a negative effect of tree size heterogeneity on the overall variability of tree growth across elevations. Further analysis also revealed that the radial growth rate of trees on the Tibetan Plateau has increased significantly compared to the past, where the growing season average temperature and annual minimum temperature were negatively and positively correlated with tree growth below and above the treeline, respectively. Our study not only confirmed that the overall variability of tree growth depends on tree size heterogeneity but also proposed an indicator that reveals net changes in the tree radial growth rate relative to the past. These theoretical advances are highly beneficial for understanding changes in the extent of subalpine forests.

4D monitoring of mountain areas using the UAV-PPK workflow

The mapping and three-dimensional modeling of mountain areas and the study of land cover change dynamics are current tasks in preserving and maintaining protected natural parks and forests. In this context, recent developments in digital photogrammetry using the SfM-MVS method to process captured imagery and the development of unmanned aerial systems (UAS) allow for reducing the costs, time, and the use of human resources and obtaining and repeatable 3D topographic data for moun-tainous regions. We will call this acquired 3D high-resolution topographic data (HRTD) 4D data in the context of an additional temporal component. The main objective of this study is to evaluate the applicability of PPK (Post-Processing Kinematic) direct georeferencing of images captured by UAVs and processed through the SfM-MVS method to obtain HRTDs for 4D land cover analysis. We analyze a 3D HRTD with an acquisition interval of two years for a mountain test area in Plana Mountain near Sofia. The test area has a diverse vegetation cover, including coniferous forest, grassland, hay meadows, shrubs, and single deciduous trees. We conducted multiple surveys of the test area with a budget PPK-UAV configuration (DJI Phantom 4 Pro with a single-frequency PPK-GNSS kit installed) from March 2020 to October 2022. Two autumn surveys from September 2020 and October 2022 were se-lected, which possess the most-good performance on numerical data accuracy. We performed 3D data analysis on 1) Assessment of the accuracy of PPK-SfM-MVS photogrammetry generated topographic data (3D clouds and DSM); 2) Investigation of the errors in the individual specific surfaces (for the individual isolated sections) using the M3C2 tool for comparing and evaluating dense point clouds; 3) Determining land cover changes in the demarcated areas using a surface of differences (DoD). Accuracy analysis showed that the PPK solution provides comparable accuracy (about RMSE3D = 0.067 m for the 2020 data, georeferencing (PPK+1GCP) and RMSE3D about 0.13 m for the 2022 data, georeferencing (PPK only)) like the GCP method. The multi-temporal topographic reconstructions based on UAV- PPK-SfM allowed us to quantify and qualitatively determine the land cover changes that occurred. The UAV-PPK-SfM workflow in the context of 4D land surface monitoring and the results suggested that even low-cost UAV-PPK systems can provide data suitable for measuring geomorphic change at the scale of the acquired data. The multi-temporal topographic reconstructions based on UAV- PPK-SfM allowed us to quantify and qualitatively determine the land cover changes that occurred. The UAV-PPK-SfM workflow in the context of 4D land surface monitoring and the results suggested that even low-cost UAV-PPK systems can provide data suitable for measuring geomorphic change at the scale of the acquired data.

Multispecies individual tree crown extraction and classification based on BlendMask and high-resolution UAV images

Accurate detection and segmentation of individual trees from unmanned aerial vehicle images is critical for forestry resource surveys and accurate forest management. Deep learning methods have been used for studies of individual tree crown segmentation, classification, and number of trees in mixed coniferous and broad-leaved forests, but the accuracy needs to be improved. Therefore, this study uses BlendMask, a simpler and more efficient algorithm that combines Mask R-CNN and Yolact algorithms to effectively combine instance-level information with semantic information at a finer granularity level, greatly improving crown segmentation accuracy and classification results. Three coniferous species and five broad-leaved species unmanned aerial vehicle images collected from the Jing Yue multispecies ecological forestry site in Changping District, Beijing, were used as the dataset, and the results were compared with Yolact and Mask R-CNN. The results show that the method described in this work has the highest Kappa coefficient (0.89) and overall accuracy (92.14%) in the test set. For segmentation accuracy, coniferous species’ producer’s accuracy was 0.91 to 0.95, whereas that of broad-leaved species was 0.89 to 0.92. For species classification, the F1-score and mean average precision for coniferous species were greater than 91%, whereas those for broad-leaved species were 77.64% to 85.63%. The accuracy of extracting stand density in low and medium canopy density stands was 0.9909 and 0.9422, respectively, whereas that in high canopy density stands was 0.8913. This study shows that the BlendMask model has a good effect in studying the classification of multiple tree species, the segmentation of individual tree crowns, and the statistics of the number of trees in complex forest areas. Compared with broad-leaved forests and high canopy density stands, this model is more suitable for coniferous forest and medium and low canopy density stand scenarios. This study provides an important tool for obtaining more accurate species classification, canopy segmentation, and resource inventory results in complex forest areas.

Tree species identity and mixing ratio affected the release of several metallic elements from mixed litter in coniferous-broadleaf plantations in subtropical China

Planting broadleaf trees in coniferous forests has been shown to promote biogeochemical cycling in plantations; however, how species mixing influences litter decomposition and release of metallic elements from mixed coniferous-broadleaf litter remains unclear. An in situ litter decomposition experiment was conducted to examine the effect of 1) a mixture from coniferous litter (Pinus massoniana) with different individual broadleaved litter (Bretschneidera sinensis, Manglietia chingii, Cercidiphyllum japonicum, Michelia maudiae, Camellia oleifera) and 2) their mixing ratio (mass ratios of coniferous and broadleaf litter of 5:5, 6:4 and 7:3) on the release of metallic elements [calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn)] during litter decomposition. We found that the identity of the broadleaf tree species in the mixed litter and the mixing ratio affected the release rates of metallic elements (p < 0.05). After one year of decomposition, K, Mg, Mn and Zn were released, while Na, Ca, Fe and Cu accumulated in the mixed litter. Mixing increased the release of K, Ca, Na, Mg, Fe, Mn, Cu and Zn in more than one-third of the samples, but inhibited the release of K, Fe and Mn in less than 14% of the samples. Increasing the mixing ratio of coniferous to broadleaf litter enhanced the release of Na, Fe, Mn and Zn but decreased the release of Ca and Mg. Overall, these results highlight that mixed litter, particularly tree species identity and mixing ratio, can alter the release and enrichment of metallic elements during litter decomposition, thereby affecting the cycling of metallic elements in plantations with different species compositions.

Mixing with broad-leaved trees shapes the rhizosphere soil fungal communities of coniferous tree species in subtropical forests

Although replanting broad-leaved trees in coniferous forest has been proven to increase stand soil quality, it is unclear how this prevalent forest management regime affects the soil fungal communities of individual conifers in mixed forest. Herein, we chose two representative coniferous tree species (Pinus massoniana and Pinus elliottii) and employed high-throughput sequencing and quantitative PCR to investigate fungal community composition and function in rhizosphere soils under monoculture and in mixed forests (replanted with Schima superba for 13 years) in subtropical China. Mixing with broad-leaved trees resulted in increased rhizosphere soil organic carbon (SOC) and nutrient (total nitrogen, NH4+ and available phosphorus). Rhizosphere soil fungal abundance (ITS gene copy numbers) and community diversity of conifers were increased after mixing. Meanwhile, the soil fungal abundance and ACE richness index in Masson pine were higher compared with slash pine whether in monoculture or mixed forests. Ascomycota, Basidiomycota, Mortierellomycota and Glomeromycota were the dominant phyla in soils. Mixing with broad-leaved trees decreased the relative abundance of Ascomycota, while it increased Basidiomycota and Glomeromycota in the rhizosphere soil of conifers. Moreover, there was a decrease in the relative abundance of animal pathogens and wood saprotrophic fungi, while soil saprotrophic fungi, ectomycorrhizal and arbuscular mycorrhizal fungi were increased in rhizosphere soil of conifers after mixing, suggesting changes from saprotrophic fungi to symbiotrophic fungi to increase soil nutrient supply and enhance tree nutrient uptake. Principal coordinates analysis showed that the fungal communities in mixed forests clustered closely and were separated from monoculture forests. Fungal community composition and function were mainly dependent on SOC. Our results indicate that mixing with broad-leaved trees increases fungal abundance, alters fungal community composition and function and thus potentially contributes to soil quality improvement and tree nutrient acquisition of conifers. Masson pine is more adaptable than slash pine to establish mixed forest in subtropical China.

Larch or Mongolian pine? Effects of tree species on soil properties and microbial biomass with the consideration of afforestation time

Tree species and afforestation age can affect soil carbon (C) and nitrogen (N) sequestration as well as soil properties through different litter input and microbial activities. However, uncertainty remains because the responses vary under different climates and prior land uses. A site-specific study was conducted to investigate the dissimilarities in plant litter, soil properties, and soil microbial biomass and their influencing factors of different aged (22, 32, and 44 years) larch (Larix principis-rupprechtii) plantations and different aged (19, 30, and 43 years) Mongolian pine (Pinus sylvestris var. mongolica) plantations. In general, afforestation increased soil organic carbon (SOC), soil total nitrogen (STN), soil microbial biomass carbon (MBC), and soil microbial biomass nitrogen (MBN) contents compared with those of sparse grassland. However, there was still room for improvement in these variables compared with local natural secondary forest, which was dominated by white birch (Betula platyphylla, a deciduous broad-leaved tree species). Changes in STN, SOC, MBC, and MBN contents with afforestation age were almost insignificant in larch plantations, while significant increase can be found in STN (only in 10–20 cm soil layer), MBC and MBN in Mongolian pine plantations. The results indicated that larch was superior to Mongolian pine in soil C and N sequestration and soil fertility improvement at an early afforestation stage probably because of the higher C and N inputs from litter and higher N supply in the soil. There is an upper limit of carbon and nitrogen sequestration and soil fertility in the coniferous plantation, and mix planting of broad-leaved trees in coniferous forests may make up for this disadvantage. This study provided a reference for the selection of afforestation tree species in northern China and other areas with similar climatic conditions.

Interaction of a Liquid Aerosol with the Combustion Front of a Forest Combustible Material Under the Conditions of Countercurrent Air Flow

Experimental investigations on the characteristic times of suppression of the flame combustion and thermal decomposition of wastes of coniferous and deciduous forest trees under the action of a liquid aerosol have been performed. As forest combustible materials, birch leaves and a mixture of components of a forest ground cover (leaves, needles, twigs) were used. Three schemes of interaction of a water droplet flow with a forest combustible material in the process of its burning were considered: the first scheme in which a material is preliminary moistened by the water sprayed upstream of its combustion front, the second scheme in which a liquid aerosol is supplied directly to the combustion front, and the third combined scheme in which water is sprayed upstream of the combustion front and over it. The influence of a favoring and an adverse air flows on the termination of combustion of a model fire hotbed was investigated. The conditions of spraying of water over forest combustible materials, providing the suppression of their flame combustion and thermal decomposition, were determined.

Deprivation of root-derived resources affects microbial biomass but not community structure in litter and soil.

The input of plant leaf litter has been assumed to be the most important resource for soil organisms of forest ecosystems, but there is increasing evidence that root-derived resources may be more important. By trenching roots of trees in deciduous and coniferous forests, we cut-off the input of root-derived resources and investigated the response of microorganisms using substrate-induced respiration and phospholipid fatty acid (PLFA) analysis. After one and three years, root trenching strongly decreased microbial biomass and concentrations of PLFAs by about 20%, but the microbial community structure was little affected and the effects were similar in deciduous and coniferous forests. However, the reduction in microbial biomass varied between regions and was more pronounced in forests on limestone soils (Hainich) than in those on sandy soils (Schorfheide). Trenching also reduced microbial biomass in the litter layer but only in the Hainich after one year, whereas fungal and bacterial marker PLFAs as well as the fungal-to-plant marker ratio in litter were reduced in the Schorfheide both after one and three years. The pronounced differences between forests of the two regions suggest that root-derived resources are more important in fueling soil microorganisms of base-rich forests characterized by mull humus than in forests poor in base cations characterized by moder soils. The reduction in microbial biomass and changes in microbial community characteristics in the litter layer suggests that litter microorganisms do not exclusively rely on resources from decomposing litter but also from roots, i.e. from resources based on labile recently fixed carbon. Our results suggest that both bacteria and fungi heavily depend on root-derived resources with both suffering to a similar extent to deprivation of these resources. Further, the results indicate that the community structure of microorganisms is remarkably resistant to changes in resource supply and adapts quickly to new conditions irrespective of tree species composition and forest management.

The Role of Microsites in the Natural Regeneration of Trees in Boreal Tall-Herb Dark Coniferous Forests of the Northern Urals

This paper presents the results of research into the role of various types of microsites (flat under- and intercrown areas, stumps, fallen logs, mounds, and pits) in the natural regeneration of trees in uneven-aged dark coniferous boreal tall-herb spruce–fir forests of the northern Urals. Areas of microsites of various types have been identified; a general description of natural tree regeneration is provided; the association of undergrowth of various tree species with different microsites was determined; and the undergrowth distribution by ontogenetic states has been assessed. The lowest undergrowth density was registered on flat sites occupying the major part of the community area, while the highest density was detected on elevated microsites (fallen logs, stumps, and mounds) the total area of which is pretty small. The highest density of the undergrowth of all species was observed on stumps. On mounds and fallen logs, it was 4.3 and 3.0 times lower, respectively. It is shown that elevated microsites (stumps, fallen logs, and mounds) are required for successful survival of the undergrowth of various tree species in boreal tall-herb forests.

The effect of tree distribution by diameter classes on the density of pine and spruce trees in mixed coniferous forest stands without forestry impact

In this paper, we consider the influence of tree distribution rows by the diameter classes on the wood density of pine and spruce in coniferous stands not covered by felling. Dependences of the wood density in pure and mixed coniferous stands were studied with changes in the composition of the stand and the quantitative representation of pine and spruce trees by diameter classes. On the basis of the obtained quantitative material, the relationship between the density of wood and trunks thicknesses was modeled according to the diameter classes of pine and spruce trees. The developed regression equations make it possible to predict the density changes of pine and spruce wood in stands with different shares of their participation.

Ризик зникнення берези повислої в Житомирському Поліссі України

З’ясовано причини усихання березових насаджень у Житомирському Поліссі України. Акцентовано увагу на глибокій патології берези повислої, яка спричинена комплексом факторів і передусім пов’язана з бактеріальною етіологією. Встановлено, що мокра деревина у стовбурі беріз – бактеріального походження. Відібрано зразки деревини й ексудату для лабораторних досліджень із рослин, які мали яскраво виражені ознаки патології (тріщини, здуття). Експериментально доведено, що збудником бактеріозу берези повислої є фітопатогенна бактерія-полібіотроф Enterobacter nimipressuralis Carter, яка спричинює водянку хвойних і листяних лісових деревних рослин.&#x0D; Встановлено, що на ступінь всихання беріз дещо впливає склад насаджень – складні за формою і мішані за складом деревостани є стійкішими до бактеріозу. Поширеність бактеріальної водянки в березових насадженнях різних вікових груп зростає зі збільшенням їхнього віку і зниженням повноти. Відзначено неоднаковий ступінь ураження бактеріальною водянкою різних груп рослинних асоціацій: чорницевих, злакових, зеленомохових та вересових.&#x0D; Під час обстеження стовбурів модельних дерев виявлено закономірність висотного розташування осередків ураження. Наведено дані щодо характеру типу ураження і щільності розташування виразок на стовбурі, описано видовий склад і рівень домінування рогохвостів, котрі екологічно та трофічно пов’язані з березою повислою.

Predicting abundance and diversity of tree-related microhabitats in Central European montane forests from common forest attributes

The continued provision of old-growth elements in forest landscapes is a critical factor for biodiversity conservation in Central Europe. A well-established method for predicting the potential of forests to maintain biodiversity is to quantify tree-related microhabitat structures (TreMs). Our aim was to predict the TreM abundance and diversity for collectives of TreM-bearing trees; here 15 large trees per plot that were preselected by the largest crown sizes using remote sensing information. TreMs were inventoried on 2085 living trees across 139 plots (each 1 ha) in montane forests of the Black Forest, southwest Germany according to a detailed catalogue comprising 64 different TreM structures. We tested the influence of forest management, forest cover in the surrounding landscape (25 km radius), forest type, the number of standing dead trees, altitude and mean diameter at breast height (DBH) on the abundance and diversity of TreMs on living trees. All plots are managed or have been recently (20–40 yrs) abandoned from management. Generalized linear models (GLM) were used to identify the drivers of abundance and diversity of TreMs. The abundance of TreMs borne by the 15 large trees per plot is greater on plots located at higher altitudes. Increasing mean DBH leads to significantly higher abundance and diversity of TreMs. Groups of TreM-bearing trees in monospecific coniferous forests have the highest abundance but those in mixed-coniferous-broadleaved forests have the greatest diversity of TreMs. The occurrences of 11 out of 64 specific TreM structures were related to forest management, forest type, altitude or mean DBH. Large branch holes and buttress cavities increased with mean DBH and were found more frequently in mixed-coniferous-broadleaved forests than in the other forest types. The abundance of epiphytes on TreM bearing trees increased with altitude. This study demonstrates that the average abundance and diversity of TreMs can be predicted with readily available forest attributes. Additionally, the occurrence of specific TreMs could be described with the variation in these selected forest attributes.

Foliar nitrogen metabolism of adult Douglas-fir trees is affected by soil water availability and varies little among provenances.

The coniferous forest tree Douglas-fir (Pseudotsuga menziesii) is native to the pacific North America, and is increasingly planted in temperate regions worldwide. Nitrogen (N) metabolism is of great importance for growth, resistance and resilience of trees. In the present study, foliar N metabolism of adult trees of three coastal and one interior provenance of Douglas-fir grown at two common gardens in southwestern Germany (Wiesloch, W; Schluchsee, S) were characterized in two subsequent years. Both the native North American habitats of the seed sources and the common garden sites in Germany differ in climate conditions. Total and mineral soil N as well as soil water content were higher in S compared to W. We hypothesized that i) provenances differ constitutively in N pool sizes and composition, ii) N pools are affected by environmental conditions, and iii) that effects of environmental factors on N pools differ among interior and coastal provenances. Soil water content strongly affected the concentrations of total N, soluble protein, total amino acids (TAA), arginine and glutamate. Foliar concentrations of total N, soluble protein, structural N and TAA of trees grown at W were much higher than in trees at S. Provenance effects were small but significant for total N and soluble protein content (interior provenance showed lowest concentrations), as well as arginine, asparagine and glutamate. Our data suggest that needle N status of adult Douglas-fir is independent from soil N availability and that low soil water availability induces a re-allocation of N from structural N to metabolic N pools. Small provenance effects on N pools suggest that local adaptation of Douglas-fir is not dominated by N conditions at the native habitats.

Root-associated fungal communities in three Pyroleae species and their mycobiont sharing with surrounding trees in subalpine coniferous forests on Mount Fuji, Japan

Pyroleae species are perennial understory shrubs, many of which are partial mycoheterotrophs. Most fungi colonizing Pyroleae roots are ectomycorrhizal (ECM) and share common mycobionts with their Pyroleae hosts. However, such mycobiont sharing has neither been examined in depth before nor has the interspecific variation in sharing among Pyroleae species. Here, we examined root-associated fungal communities in three co-existing Pyroleae species, including Pyrola alpina, Pyrola incarnata, and Orthilia secunda, with reference to co-existing ECM fungi on the surrounding trees in the same soil blocks in subalpine coniferous forests. We identified 42, 75, and 18 fungal molecular operational taxonomic units in P. alpina, P. incarnata, and O. secunda roots, respectively. Mycobiont sharing with surrounding trees, which was defined as the occurrence of the same mycobiont between Pyroleae and surrounding trees in each soil block, was most frequent among P. incarnata (31 of 44 plants). In P. alpina, sharing was confirmed in 12 of 37 plants, and the fungal community was similar to that of P. incarnata. Mycobiont sharing was least common in O. secunda, found in only 5 of 32 plants. Root-associated fungi of O. secunda were dominated by Wilcoxina species, which were absent from the surrounding ECM roots in the same soil blocks. These results indicate that mycobiont sharing with surrounding trees does not equally occur among Pyroleae plants, some of which may develop independent mycorrhizal associations with ECM fungi, as suggested in O. secunda at our research sites.

Interspecific Plastome Recombination Reflects Ancient Reticulate Evolution in Picea (Pinaceae).

Plastid sequences are a cornerstone in plant systematic studies and key aspects of their evolution, such as uniparental inheritance and absent recombination, are often treated as axioms. While exceptions to these assumptions can profoundly influence evolutionary inference, detecting them can require extensive sampling, abundant sequence data, and detailed testing. Using advancements in high-throughput sequencing, we analyzed the whole plastomes of 65 accessions of Picea, a genus of ∼35 coniferous forest tree species, to test for deviations from canonical plastome evolution. Using complementary hypothesis and data-driven tests, we found evidence for chimeric plastomes generated by interspecific hybridization and recombination in the clade comprising Norway spruce (P. abies) and 10 other species. Support for interspecific recombination remained after controlling for sequence saturation, positive selection, and potential alignment artifacts. These results reconcile previous conflicting plastid-based phylogenies and strengthen the mounting evidence of reticulate evolution in Picea. Given the relatively high frequency of hybridization and biparental plastid inheritance in plants, we suggest interspecific plastome recombination may be more widespread than currently appreciated and could underlie reported cases of discordant plastid phylogenies.

Seasonal changes of natural antioxidant content in the leaves of Hungarian forest trees

Despite the numerous investigations on the phenolic composition and antioxidant properties of different plant tissues, there are only a few studies about forest tree leaves, moreover, the monitoring of seasonal changes is an underexplored area. The present investigation aimed to provide a comparative analysis of the antioxidant properties of the leaves from 12 selected Hungarian coniferous and deciduous forest tree species, during the vegetation period. From the methanolic extracts, the total phenol, flavonoid and flavan-3-ol contents were determined, as well as the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and ferric reducing ability of plasma (FRAP) antioxidant capacities. The investigated species revealed diverse seasonal tendencies in their chemical parameters, including seasonal extremities. According to results, polyphenols had a determinant role in the antioxidant efficiency of the leaf extracts. The evaluation of the overall antioxidant power was accomplished by a scoring system. The species with the highest antioxidant capacity values (scores) were: European hornbeam (Carpinus betulus L.)>sweet chestnut (Castanea sativa Mill.)>Turkey oak (Quercus cerris L.)>downy oak (Quercus pubescens Willd.)>pedunculate oak (Quercus robur L.). The leaves of the listed species could be future sources of food antioxidants and nutritional supplements.

Quantifying the missing link between forest albedo and productivity in the boreal zone

Abstract. Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Currently, the physical link between forest albedo and productivity is poorly understood, yet it is crucial for designing optimal forest management strategies for mitigating climate change. We investigated the relationships between boreal forest structure, albedo and FAPAR using a radiative transfer model called Forest Reflectance and Transmittance model FRT and extensive forest inventory data sets ranging from southern boreal forests to the northern tree line in Finland and Alaska (N = 1086 plots). The forests in the study areas vary widely in structure, species composition, and human interference, from intensively managed in Finland to natural growth in Alaska. We show that FAPAR of tree canopies (FAPARCAN) and albedo are tightly linked in boreal coniferous forests, but the relationship is weaker if the forest has broadleaved admixture, or if canopies have low leaf area and the composition of forest floor varies. Furthermore, the functional shape of the relationship between albedo and FAPARCAN depends on the angular distribution of incoming solar irradiance. We also show that forest floor can contribute to over 50 % of albedo or total ecosystem FAPAR. Based on our simulations, forest albedos can vary notably across the biome. Because of larger proportions of broadleaved trees, the studied plots in Alaska had higher albedo (0.141–0.184) than those in Finland (0.136–0.171) even though the albedo of pure coniferous forests was lower in Alaska. Our results reveal that variation in solar angle will need to be accounted for when evaluating climate effects of forest management in different latitudes. Furthermore, increasing the proportion of broadleaved trees in coniferous forests is the most important means of maximizing albedo without compromising productivity: based on our findings the potential of controlling forest density (i.e., basal area) to increase albedo may be limited compared to the effect of favoring broadleaved species.