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Aim Overstorey tree species influence both soil properties and microclimate conditions in the forest floor, which in turn can induce changes in ground bryophyte communities. The aim of the study was to investigate the effect of tree species identity and the most important habitat factors influencing understorey bryophytes. Methods We assessed the effect of 14 tree species and related habitat parameters, including soil parameters, vascular plant presence and light intensity on bryophytes in monospecific plots covered by nearly fifty-year-old trees in the Siemianice Experimental Forest (Poland). Results The canopy tree species determined bryophyte species richness and cover. The strongest differences were observed between plots with deciduous and coniferous trees. Soils with a more acidic pH and lower content of macronutrients supported larger bryophyte coverage. We also found a positive correlations between vascular plants and availability of light as well as bryophyte species richness. Conclusion Tree species identity and differences in habitat conditions in the forest floor lead to changes of ground bryophyte richness, cover and species composition. Consequently, the changes in the dominant tree species in the stand may result in significant repercussions on ground bryophyte communities. We indicated that the introduction of alien tree species, i.e. Quercus rubra , has an adverse effect on bryophyte communities and suggested that the selection of tree species that contribute to the community consistent with the potential natural vegetation is highly beneficial for maintaining ground bryophyte biodiversity.

The objective of this study was to verify the accuracy of tree species identification using deep learning with leaf images of broadleaf and coniferous trees in outdoor photographs. For each of 12 broadleaf and eight coniferous tree species, we acquired 300 photographs of leaves and used those to produce 72,000 256 × 256-pixel images. We used Caffe as the deep learning framework and AlexNet and GoogLeNet as the deep learning algorithms. We constructed four learning models that combined two learning patterns: one for individual classification of 20 species and the other for two-group classification (broadleaf vs. coniferous trees), with and without data augmentation, respectively. The performance of the proposed model was evaluated according to the MCC and F-score. Both classification models exhibited very high accuracy for all learning patterns; the highest MCC was 0.997 for GoogLeNet with data augmentation. The classification accuracy was higher for broadleaf trees when the model was trained using broadleaf only; for coniferous trees, the classification accuracy was higher when the model was trained using both tree types simultaneously than when it was trained using coniferous trees only.

The temperature in northwestern China has increased significantly since the 1990s. However, the responses of mountainous forests to warming have not been extensively examined. We collected tree rings of two dominant coniferous species of Qinghai spruce (Picea crassifolia) and Chinese pine (Pinus tabulaeformis) in the eastern part of the Qilian Mountains, and analyzed the differences in the response dynamic of the radial growth of two species to climate change. The results showed that (1) the annual radial growth of Qinghai spruce was mainly restricted by the minimum temperature in July and October, and the growth of Chinese pine was mainly restricted by the mean temperature in September of the previous year, January, and July and the maximum temperature in March, May, and July. In particular, Qinghai spruce increased its sensitivity to total precipitation in the growing seasons in March, May, and July after the temperature abruptly increased. (2) In comparison to Qinghai spruce, Chinese pine showed a consistent response to the main climatic factors and was more severely affected by drought stress. Qinghai spruce had divergent responses to mean temperatures in March and May and minimum temperatures in April and June. (3) The growth of Qinghai spruce increased with a significant fluctuation at the end of the twentieth century, while the growth of Chinese pine first showed an increase and then a significant decreasing trend. At present, the increase in temperature has adversely affected the growth of Chinese pine in the eastern Qilian Mountains and promoted the growth of Qinghai spruce. However, a continuous temperature increase could negatively affect the growth of Qinghai spruce because of the increasing probability of drought stress. Therefore, we should pay more attention to the growth dynamics of Qinghai spruce, especially with the different water supply and demand, and to the effects of drought on Chinese pine in forest ecosystems in arid and semiarid areas.

AimSoil microbial legacy is a potentially important regulator of the associations of plants and mycorrhizal fungi. However, our understanding of how plant performance and root-associated fungi react to distinct soil microbial legacies during subalpine forest succession remains unclear.MethodsA pot experiment of two coniferous (Picea asperata Mast. and Abies fargesii var. faxoniana (Rehder & E. H. Wilson) Tang S. Liu) tree seedlings, using sterilized soil inoculated with the soil microbial legacy of herbs, shrubs, and trees, was conducted in a greenhouse. Plant biomass, root morphological traits (total root length, root surface area, and the number of root tips), the percentage of ectomycorrhizal (EcM) root colonization, root-associated fungal communities, and soil inorganic nitrogen content were measured.ResultsBoth coniferous seedling performance and EcM colonization were facilitated when grown in the soil microbial legacies of shrubs and trees rather than herbs. Correspondingly, soil microbial legacy favored root-associated EcM Ascomycetes and EcM fungi with ‘short-distance’ exploration type. The soil microbial legacies of trees induced a greater relative abundance of Wilcoxina, while those of herbs and shrubs resulted in greater abundances of Trichophaea, Geopora, and Hebeloma (belonging to ‘short-distance’ exploration type). Notably, the relative abundances of ‘short-distance’ explorers were positively correlated with root biomass.ConclusionsSoil microbial legacy may affect tree seedling establishment and modify plant performance across successional stages by regulating the colonization, composition, and exploration type of root-associated fungi.

To explore the difference in the response of the radial growth of Pinus tabulaeformis and Picea crassifolia on different timescales to climate factors in the eastern part of Qilian Mountains, we used dendrochronology to select four different timescales (day, pentad (5 days), dekad (10 days), and month) for exploration. The primary conclusions were as follows: (1) According to an investigation of the dynamic correlations between radial growth and climate conditions, drought during the growing season has been the dominant limiting factor for radial growth across both species in recent decades; (2) climate data at the dekad scale are best for examining the correlations between radial growth and climate variables; and (3) based on basal area increment, P. tabuliformis in the study area showed a trend of first an increase and then a decrease, while P. crassifolia showed a trend of continuous increase (BAI). As the climate continues to warm in the future, forest ecosystems in arid and semi-arid areas will be more susceptible to severe drought, which will lead to a decline in tree growth, death, and community deterioration. As a result, it is critical to implement appropriate management approaches for various species based on the peculiarities of their climate change responses.

Despite the well-established ability of urban green belts to reduce traffic noise, a comprehensive analysis of the specific role played by mixed coniferous trees and shrubs in noise mitigation remains lacking. This study aimed to clarify how different planting patterns and the characteristics of plants affect their noise-reduction performance. To achieve this, noise reduction was measured at 18 roadside green spaces comprising mixed coniferous trees and shrubs in Harbin, China, and Moscow, Russia. The results indicate that in lanes 5–15 m wide, the ‘Abreast’ planting pattern consistently offered greater noise reduction than the ‘Taffy’ configuration at all measured distances (5, 10 and 15 m). In addition, in winter the effectiveness of noise reduction improved due to snow cover, which enhanced the sound-absorbing properties of the vegetation. In our analysis, key factors such as diameter at breast height, minimum height under branches and road width emerged as crucial predictors of traffic noise reduction. Among these, carriageway width and sidewalk width exhibited the strongest correlations with noise attenuation. Finally, we developed a quantitative model for roadside green spaces that incorporates plant characteristics, planting schemes and road features. This model allows us to assess the contribution of each factor to overall noise reduction. The results of this study provide a scientific basis for designing and optimising vegetation-based noise-mitigation strategies to enhance the urban acoustic environment while also offering an analytical framework to support evidence-based urban forestry planning and policy.

This study was carried out to understand the characteristic of biogenic volatile organic compounds emitted from coniferous trees. The measured amounts of monoterpenes emitted from Pitch pine ( Pinus rigida ) and Korean pine ( Pinus koraiensis ) by season were generally in the order of: spring > summer ≈ fall > winter. The standard emission rate (the monoterpene emission rate at a standard temperature of 30 °C) from the coniferous trees decreased in fall and winter. In particular, the standard emission rates in winter were 1.2–6 times less than those during other seasons. In addition, the standard emission rates of P. koraiensis were significantly lower (3–30 times) than those of other coniferous species. α-Pinene, β-pinene, myrcene, and α-terpinene were the most abundant chemicals generated from P. rigida . However, the contribution of individual compounds to P. koraiensis displayed a different pattern from those from P. rigida and was dominated by α-pinene, d-limonene, and myrcene emissions. The monoterpene emission flux (EF) from P. koraiensis was 3–4 times lower than that from P. rigida .

In the context of climate change, assessing the adaptive potential of species and populations is crucial for developing effective conservation strategies. Changes in plant gene expression play a significant role in the adaptation process to climate change. This study aims to explore the adaptive responses of the conifer species Chamaecyparis hodginsii (the name has been revised from Fokienia hodginsii ) to climate change and analyze the molecular-level reactions of these long-lived trees to climatic shifts. It seeks to understand their phenotypic responses to climate change, identify key environmental factors driving adaptive gene expression, and provide information for transplantation conservation strategies based on genetic adaptability. By conducting mixed-tissue RNA sequencing on samples from multiple provenances and employing redundancy analysis (RDA), weighted gene co-expression network analysis (WGCNA), and partial least squares path modeling (PLS-PM), the study assesses the impact of climatic variables on gene expression and phenotype. It identifies key gene groups associated with environmental responses and elucidates the complex relationships between environmental factors, functional gene groups, and phenotypic traits. The findings reveal that C. hodginsii adapts to environmental stresses by regulating specific gene activities related to morphological trait adjustments. Moreover, environmental factors such as the impact on tree architecture emphasize the importance of Precipitation Seasonality, Isothermality, and Precipitation of Driest Quarter for adapting to climate stresses. This research not only unveils the complex adaptive responses of C. hodginsii to climate change but also provides critical insights for the management and conservation of long-lived tree species facing climate change threats.

How coniferous forests evolved in the Northern Hemisphere remains largely unknown. Unlike most groups of organisms that generally followa latitudinal diversity gradient, most conifer species in the Northern Hemisphere are distributed in mountainous areas at middle latitudes. It is of great interest to know whether the midlatitude region has been an evolutionary cradle or museum for conifers and how evolutionary and ecological factors have driven their spatiotemporal evolution. Here, we investigated the macroevolution of Pinus, the largest conifer genus and characteristic of northern temperate coniferous forests, based on nearly complete species sampling. Using 1,662 genes from transcriptome sequences, we reconstructed a robust species phylogeny and reestimated divergence times of global pines. We found that ∼90% of extant pine species originated in the Miocene in sharp contrast to the ancient origin of Pinus, indicating a Neogene rediversification. Surprisingly, species at middle latitudes are much older than those at other latitudes. This finding, coupled with net diversification rate analysis, indicates that the midlatitude region has provided an evolutionary museum for global pines. Analyses of 31 environmental variables, together with a comparison of evolutionary rates of niche and phenotypic traits with a net diversification rate, found that topography played a primary role in pine diversification, and the aridity index was decisive for the niche rate shift. Moreover, fire has forced diversification and adaptive evolution of Pinus. Our study highlights the importance of integrating phylogenomic and ecological approaches to address evolution of biological groups at the global scale.

Mature forests provide important wildlife habitat and support critical ecosystem functions globally. Within the dry conifer forests of the western United States, past management and fire exclusion have contributed to forest conditions that are susceptible to increasingly severe wildfire and drought. We evaluated declines in conifer forest cover in the southern Sierra Nevada of California during a decade of record disturbance by using spatially comprehensive forest structure estimates, wildfire perimeter data, and the eDaRT forest disturbance tracking algorithm. Primarily due to the combination of wildfires, drought, and drought-associated beetle epidemics, 30% of the region’s conifer forest extent transitioned to nonforest vegetation during 2011–2020. In total, 50% of mature forest habitat and 85% of high density mature forests either transitioned to lower density forest or nonforest vegetation types. California spotted owl protected activity centers (PAC) experienced greater canopy cover decline (49% of 2011 cover) than non-PAC areas (42% decline). Areas with high initial canopy cover and without tall trees were most vulnerable to canopy cover declines, likely explaining the disproportionate declines of mature forest habitat and within PACs. Drought and beetle attack caused greater cumulative declines than areas where drought and wildfire mortality overlapped, and both types of natural disturbance far outpaced declines attributable to mechanical activities. Drought mortality that disproportionately affects large conifers is particularly problematic to mature forest specialist species reliant on large trees. However, patches of degraded forests within wildfire perimeters were larger with greater core area than those outside burned areas, and remnant forest habitats were more fragmented within burned perimeters than those affected by drought and beetle mortality alone. The percentage of mature forest that survived and potentially benefited from lower severity wildfire increased over time as the total extent of mature forest declined. These areas provide some opportunity for improved resilience to future disturbances, but strategic management interventions are likely also necessary to mitigate worsening mega-disturbances. Remaining dry mature forest habitat in California may be susceptible to complete loss in the coming decades without a rapid transition from a conservation paradigm that attempts to maintain static conditions to one that manages for sustainable disturbance dynamics.