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Tree detection and canopy area measurement are important and difficult tasks in forest inventory, which are important for understanding forest stand structure. This study utilized remotely piloted aircraft (RPA) aerial photography technology to collect remote sensing images of forests in Xiong County, China, creating a dataset comprising 1200 images of six tree species. Based on this dataset, the paper proposes an optimized model, Att-Mask R-CNN, for canopy detection and segmentation. Att-Mask R-CNN outperforms the original models (Mask R-CNN and MS R-CNN) by achieving 65.29% mean average precision for detection, 80.44% mean intersection over union for segmentation, and 90.67% overall recognition rate for the six tree species. In addition, a pixel statistics method based on segmentation masks is introduced for estimating the vertical projected area of individual tree crowns, and comparisons between the measured and predicted vertical projected area of the crowns of six tree species (100 trees of each class) show an overall goodness-of-fit R2 of 85% and a relative root-mean-square error rRMSE of 12.81%. By using remote sensing images from RPAs and optimizing existing deep learning models, the detection and segmentation of individual tree canopies can be achieved, resulting in a more accurate understanding of forest structure, which provides scientific support for forest management and resource monitoring. [ABSTRACT FROM AUTHOR]

Forest products trade has a critical role to play in both global economic development and environmental protection. Based on the trade data of global forest products, raw forest products, and processed forest products from 2000 to 2020, this paper constructed a trade network and analyzed its pattern by using indicators such as density, average distance, out-strength, and in-strength. The results show that from 2000 to 2020, the global trade network of forest products has been increasingly connected. Compared with the trade of raw material forest products, the trade network of processed forest products is more closely connected and its transport efficiency is higher. Countries with high GDP such as USA, China, and Germany are leading trading countries in forest products. Countries with abundant forest resources are the major exporters of raw forest products, while labor- and capital-abundant countries are major exporters of processed forest products. Countries with abundant labor and capital and high GDP are the main importers of raw forest products. [ABSTRACT FROM AUTHOR]

Growth and yield systems are essential tools for enhancing forest management decision-making. This study systematically evaluated three stand-level models and two data types for predicting stand survival and basal area of Chinese fir (Cunning lanceolate (Lamb.) Hook.) plantations in southern China. The first model links survival and diameter through the self-thinning concept. The second model incorporates stand diameter, the previous year's diameter, and stand survival, while the third model treats stand survival and diameter as mutually independent functions of only stand age. Model 2 was the best performer for short-term prediction (2–4 years), whereas Model 3 excelled in longer projection periods (6–10 years). Despite the independent predictions of stand survival and diameter in Model 3, it closely tracked observed self-thinning trajectories in long-term predictions. Tree-level model growth derived from Models 2 and 3 performed optimally for short-term and long-term tree-level predictions, respectively. While limited to four experimental sites, this research contributes theoretical groundwork to growth and yield modeling for Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understory small trees and shrubs play a crucial role in the biogeochemical cycles in forest ecosystems. However, their biomass in northeastern China is still uncertain and has been heavily disregarded due to the limited number of available allometric equations. For this study, 782 plants from 33 species obtained by the destructive method were used to develop species-specific and generalized aboveground allometric biomass equations based on collar diameter (D) and height (H) using weighted nonlinear seemingly unrelated regression. Each biomass component was shown to be well predicted by D alone, with R2 adj. values mostly greater than 0.80. The majority of species performed better in the models for wood and aboveground biomass when H was included as D2H. Furthermore, generalized equations for the two components showed a comparatively large coefficient of variation but comparable Bias to species-specific equations, especially for small trees. It is recommended to estimate biomass using generalized equations for mixed species only when species-specific equations are unavailable at a given site. However, in the event when precision is not the primary concern, generalized equations are also suggested. The developed equations will help to improve the accuracy of biomass assessment of understory woody plants in northeastern China forest ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As one of the most widely used dwarf bamboos, Pleioblastus viridistriatus has well-developed rhizome and root systems, which can rapidly expand into forest stands. However, little is known about the influence of P. viridistriatus expansion on the undergrowth diversity in subtropical forests of China and its association with the diversity of soil bacterial microbiota. The species diversity and soil bacterial community structure were investigated in a forest where P. viridistriatus was expanding into coniferous and broad-leaved mixed forest. We found that P. viridistriatus expansion reduced species diversity in the shrub and herbaceous layers and had significant effects on major soil physicochemical properties. In addition, the alpha diversity indexes were significantly increased and the abundance of Actinobacteria and Candidatus Saccharibacteria increased, while the abundance of Nitrospirae and Deinococcus-Thermus decreased with the increasing expansion. At the genus level, a total of 25 genera of soil bacteria showed significant difference in abundance. Overall, expansion of P. viridistriatus reduced forest species diversity, while increased soil nutrient accumulation and specific bacterial abundance to improve nutrient acquisition. Our results can provide guidance for controlling dwarf bamboo expansion and help the sustainable forest management. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Available P is the major growth-limiting factor in southern China where Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations are increasingly established. Planting P-efficient clones is a viable option to enhance productivity of Chinese fir plantations. Two Chinese fir clones with high P efficiency (M1 and M4) were chosen as the research materials and their adaptive responses to low P stress were examined. The increment in root morphological traits and biomass production of these clones was measured by a sand culture experiment with a heterogeneous P supply. For both clones, P starvation resulted in significantly higher root surface area and root volume but not root length. For clone M4, the mean root diameter was also larger under P deficiency than under normal P supply. Interestingly, the root morphological traits varied substantially within the same root system where the starved roots had higher values for all morphological traits than the nonstarved ones. Phosphorus starvation did not affect shoot and root biomass or the root to shoot ratio, but the whole-plant biomass increment was large under P deficiency for clone M4. In conclusion, the adaptation to low P stress in these clones is attributed to increased P acquisition and utilization efficiencies. La disponibilité de P est le principal facteur limitant dans le sud de la Chine où le sapin de Chine (Cunninghamia lanceolata (Lamb.) Hook.) est de plus en plus planté. La plantation de clones qui utilisent efficacement le P constitue une option pour améliorer la productivité des plantations de sapin de Chine. Deux clones de sapin de Chine dont l'efficacité d'utilisation de P est élevée (M1 et M4) ont été choisis comme matériel expérimental et leurs réactions adaptatives à un léger stress causé par une carence en P ont été étudiées. L'accroissement des caractères morphologiques des racines et de la production de biomasse de ces clones a été mesuré au moyen d'une expérience de culture dans le sable avec différents apports de P. Chez les deux clones, une carence en P a entraîné une augmentation significative de la surface et du volume mais non de la longueur des racines. Le diamètre moyen des racines du clone M4 était également plus grand lorsque P était déficient que lorsque l'apport de P était normal. Il est intéressant de noter que les caractères morphologiques des racines variaient substantiellement chez un même système racinaire : tous les caractères morphologiques avaient des valeurs plus élevées chez les racines carencées que chez les racines non carencées. Une carence en P n'a pas influencé la biomasse des pousses et des racines, ni le rapport entre les racines et les pousses, mais l'accroissement de la biomasse globale des plants du clone M4 était important lorsque le P était déficient. En conclusion, l'adaptation de ces clones à un léger stress causé par une carence en P est attribuée à une plus grande efficacité de prélèvement et d'utilisation de P. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the subalpine zone of the Qinghai–Tibetan Plateau of China, Dragon spruce (Picea asperata Mast.) is commonly used for reforestation. The aim of the present work was to study the effects of seasonally frozen soil on the germination of P. asperata seeds and to investigate whether these effects were associated with resumption of the antioxidant defense system. The nonfrozen treatment resulted in near failure of germination (1%) and was associated with relatively high levels of hydrogen peroxide (H2O2) and low activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxide (APX). Germination of P. asperata seeds at 10 cm under the seasonally frozen soil was higher than that at 5 cm by 26%; this higher germination rate was associated with the recovery of SOD, CAT, and APX activities. The levels of malondialdehyde (MDA) in seeds from seasonally frozen treatments were higher than those in the nonfrozen treatment, implying greater lipid peroxidation and that frozen seeds might have suffered from oxidative stress. The results indicate that seasonally frozen soil facilitated the germination of P. asperata seeds and that germination was closely related to the resumption of antioxidant enzymes activity. Overall, these findings suggest that the disappearance of seasonally frozen ground caused by global warming might result in failure of regeneration of P. asperata. L’épicéa de Chine (Piceaasperata Mast.) est couramment utilisé pour le reboisement dans la zone subalpine du plateau Qinghai–Tibet en Chine. Le but des travaux présentés dans cet article consistait à étudier les effets d’un gel saisonnier dans le sol sur la germination des graines de P. asperata et à déterminer si ces effets étaient associés au rétablissement du système de défense antioxydant. Un traitement sans gel a empêché presque toute germination (1 %) et était associé à un niveau relativement élevé de peroxyde d’hydrogène (H2O2) et à une faible activité de la superoxyde dismutase (SOD), de la catalase (CAT) et de l’ascorbate peroxydase (APx). À une profondeur de 10 cm dans un sol soumis à un gel saisonnier la germination des graines de P. asperata était 26 % plus élevée qu’à 5 cm et elle était associée à la reprise de l’activité de la SOD, de la CAT et de l’APx. Le niveau de propanedial (MDA) dans les graines exposées à un gel saisonnier était plus élevé que dans les graines non exposées au gel, ce qui implique une plus grande peroxydation des lipides et le fait que ces graines aient pu souffrir d’un stress oxydatif. Les résultats indiquent que le gel saisonnier dans le sol assure une meilleure germination des graines de P. asperata. La germination était étroitement reliée à la reprise de l’activité des enzymes antioxydantes. La disparition du gel saisonnier dans le sol causée par le réchauffement global pourrait mettre en péril la régénération de P. asperata. [ABSTRACT FROM AUTHOR]

Taxus wallichiana var. mairei (Lemée & Léveillé) L. K. Fu & Nan Li is a highly endangered conifer in China. It is dioecious and wind pollinated, with seed dispersal by animals. Extant natural populations on mainland China and Taiwan are highly scattered, largely as a result of habitat loss and overexploitation. Intersimple sequence repeat (ISSR) markers were employed to assess the genetic structure among 464 individuals from 17 populations across the variety’s distribution range in the Sino–Japanese and Malesian floristic subkingdoms. ISSRs revealed a high genetic diversity (percentage of polymorphic loci = 98.4%, Nei’s gene diversity = 0.3467, Shannon’s information index = 0.5152) at the species level and high differentiation among populations (coefficient of gene differentiation = 0.4066; θB = 0.4376). Gene flow among populations was found to be limited to the mainland populations. A UPGMA (unweighted pair group method with arithmetic mean) dendrogram suggests that the population in Taiwan is genetically the most isolated, while among the mainland populations a trend of an east–west split is suggested. This finding is supported by the analysis of molecular variance. The pattern of genetic variation suggests that the extant distribution of T. wallichiana var. mairei is the result of the fragmentation of a historically more continuous distribution. Conservation measures for this highly endangered plant are discussed, and an integrated approach to increase plant density and connectivity among the remaining populations is suggested. Taxus wallichiana var. mairei (Lemée & Léveillé) L. K. Fu & Nan Li est un conifère chinois très menacé. C’est une espèce dioïque et anémophile dont les graines sont dispersées par les animaux. Les populations naturelles qui subsistent en Chine continentale et à Taiwan sont très fragmentées en raison de la surexploitation et de la perte d’habitats. Les auteurs ont utilisé des marqueurs des régions intermicrosatellitaires (ISSR) pour évaluer la structure génétique de 464 individus dans 17 populations représentatives de la répartition naturelle de l’espèce dans les sous-régions floristiques malaisienne et sino-japonaise. Les marqueurs ISSR ont révélé une grande diversité génétique au niveau de l’espèce (PPB = 98,4 %, HE = 0,3467, I = 0,5152) et une forte différenciation parmi les populations (GST = 0,4066; θB = 0,4376). Le flux génique parmi les populations était limité aux populations continentales. Un dendrogramme UPGMA indique que la population de Taiwan est génétiquement la plus isolée et que les populations continentales ont tendance à se dissocier selon un axe est-ouest, ce qui est supporté par AMOVA. Ce patron de variation génétique indique que la distribution actuelle de T. wallichiana var. mairei est le résultat de la fragmentation d’une distribution historiquement plus continue. Les auteurs discutent de mesures de conservation pour cette espèce fortement menacée; ils suggèrent d’adopter une approche intégrée pour augmenter la densité des populations résiduelles ainsi que leur connectivité. [ABSTRACT FROM AUTHOR]

The morphological and physiological responses of two contrasting Populus cathayana Rehd. populations to three light regimes, full sunlight (control), 33% full sunlight (moderate shade), and 12% full sunlight (severe shade), were investigated under well-watered and drought conditions. The populations were from Hanyuan (relatively more annual rainfall and less annual solar radiation) and Ledu (less annual rainfall and more annual solar radiation) in western China. In both populations, drought-treated plants exhibited reduced growth, leaf relative water content, net photosynthesis, and maximal efficiency of photosystem II (PSII); increased levels of chlorophyll, carotenoid, abscisic acid, and carbon isotope composition; and a greater accumulation of malondialdehyde (MDA) than did well-watered plants. There was an apparent alleviation of drought effects by moderate shade, especially in the Hanyuan population, as indicated by the higher leaf relative water content, net photosynthesis, stomatal conductance, and maximal efficiency of PSII and the lower MDA content. On the other hand, an apparent aggravation of drought effects by severe shade was also observed, especially in the Ledu population, as indicated by the lower total biomass and net photosynthesis and the higher MDA content. Moreover, the Hanyuan population was more shade tolerant and drought sensitive than the Ledu population. Les réactions morphologiques et physiologiques de deux populations différentes de Populus cathayana Rehd. à trois régimes de lumière, c.-à-d. plein ensoleillement (témoin), 33 % du plein ensoleillement (ombrage modéré) et 12 % du plein ensoleillement (très ombragé), ont été étudiées dans des conditions adéquates d’arrosage et des conditions de sécheresse. Les populations provenaient de Hanyuan (précipitations annuelles relativement plus élevées et rayonnement solaire annuel relativement plus faible) et de Ledu (moins de précipitations annuelles et plus de rayonnement solaire annuel) dans l’ouest de la Chine. Dans les deux populations, la croissance, la teneur relative en eau dans les feuilles, la photosynthèse nette et l’efficacité maximale de PSII étaient plus faibles et les quantités de chlorophylle, de carotène, d’acide abscissique, la composition isotopique du carbone ainsi que l’accumulation de propanedial étaient plus élevées chez les plants exposés à la sécheresse que chez les plants bien arrosés. Les effets de la sécheresse ont apparemment été atténués par un ombrage modéré, spécialement dans la population de Hanyuan, tel que l’indiquaient une teneur relative en eau dans les feuilles, une photosynthèse nette, une conductance stomatale et une efficacité maximale de photosystème II (PSII) plus élevées ainsi qu’un contenu en propanedial plus faible. D’un autre côté, les effets de la sécheresse ont apparemment été aggravés par des conditions très ombragées, spécialement dans la population de Ledu, tel que l’indiquaient la biomasse totale et la photosynthèse nette plus faibles ainsi que le contenu en propanedial plus élevé. De plus, la population de Hanyuan était plus tolérante à l’ombre et plus sensible à la sécheresse que la population de Ledu. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)