Phoebe Zhennan Research Articles

Assessing population genetic structure and diversity and their driving factors in Phoebe zhennan populations

Assessing population genetic structure and diversity and their driving factors in Phoebe zhennan populations

Introduction of broadleaf tree species can promote the resource use efficiency and gross primary productivity of pure forests.

Long-term pure forest (PF) management and successive planting has result resulted in "low-efficiency artificial forests" in large areas. However, controversy persists over the promoting effect of introduction of broadleaf tree species on production efficiency of PF. This study hypothesised that introduced broadleaf tree species can significantly promote both water-nutrient use efficiency and gross primary productivity (GPP)of PF. Tree ring chronologies, water source, water use efficiency and GPP were analysed in coniferous Cunninghamia lanceolata and broadleaved Phoebe zhennan growing over the past three decades. The introduction of P. zhennan into C. lanceolata plantations resulted in inter-specific competition for water, probably because of the similarity of the main water source of these two tree species. However, C. lanceolata absorbed more water with a higher nutrient level from the 40-60-cm soil layer in mixed forests (MF). Although the co-existing tree species limited the basal area increment and growth rates of C. lanceolata in MF plots, the acquisition of dissolved nutrients from the fertile topsoil layer were enhanced; this increased the water use efficiency and GPP of MF plots. To achieve better ecological benefits and GPP, MFs should be constructed in southern China.

Influence of tree age on the wood color and compounds involved in the “golden-thread” wood color formation in Phoebe zhennan

Wood color plays a key role in the quality and commercial value of wood products. However, the mechanism underlying wood color formation has yet to be fully elucidated. The principal objective of this study was to determine the effects of tree age on the wood color and identify the key metabolites correlated with the golden-thread wood color formation in Phoebe zhennan. The results indicated that the golden-thread wood color of P. zhennan was significantly affected by tree age. Four polar organic solvents and water were tested for the extraction of the metabolites, and ethyl acetate was determined to be the most suitable solvent for the extraction of the golden-thread wood color-related metabolites. Based on the experimental data from the UVVIS-NIR spectral scanning and comparative metabolomics, 66 differentially accumulated metabolites were significantly enriched in older wood, and among these, 46 metabolites (e.g., prenol lipids, carboxylic acids and their derivatives, steroids and their derivatives, and benzene and its substituted derivatives) were closely related to the golden-thread wood color formation (r = 0.526–0.944, P < 0.05). In addition, compared to younger wood (10 years old), older wood (30 and 80 years old) had greater durability and a stronger fragrance because of the enrichment of sesquiterpenoids in older wood. In this study, the effects of tree age on P. zhennan wood color, fragrance, and durability were determined through the alterations in the composition and contents of the related secondary metabolites. These findings contribute to a better understanding of the special wood color formation and can be used for a wide range of applications in the wood industry, from quality control to marketing and product development.

Characterizing BVOC emissions of common plant species in northern China using real world measurements: Towards strategic species selection to minimize ozone forming potential of urban greening

Biogenic volatile organic compounds (BVOCs) emitted by plants play a crucial role in ozone (O3) formation. Avoiding urban air quality trade-offs of urban greening involves selecting low-emission and O3 forming potential (OFP) plants. Using a dynamic enclosure system and the TD-GC-MS technique, we measured BVOC emissions from 47 common urban greening plant species in northern China. The potential to form O3 was estimated based on the emission quantification of 63 compounds and their maximum incremental reactivity (MIR) values. The results indicated that isoprene and most of monoterpene dominated BVOC emissions. Most of the broad-leaved trees were isoprene emitter, whereas needle-leaved and some broad-leaved trees emitted monoterpene and sesquiterpene. Alkene emissions, such as 1-hexene, were relatively low, while Phoebe zhennan exhibited higher aromatics such as m-ethyltoluene. Broad-leaved trees had a higher potential for O3 generation compared to needle-leaved trees. BVOC emission rates and OFP varied significantly among plant species, ranging from 0.08 to 112.23 μg/(g h) and 0.33–1130.75 μg/(g h), respectively. To minimize BVOC emissions and O3 pollution, we determined a list of preferred urban greening plants using hierarchical cluster analysis combined BVOC emission rates and OFPs. Based on our findings, we recommend incorporating plants with low BVOC emissions and OFPs, such as Eucommia ulmoides, Firmiana platanifolia, and Cercis chinensis, in future urban greening plans to prevent strengthening O3 pollution in northern China.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology.

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms remain poorly understood. In a two-way factorial block design, the growth and photosynthesis of 2-year-old Phoebe zhennan seedlings were investigated in two water availabilities (high versus low) and three stimulated fissure habitat groups (soil, soil-filled fissure and non-soil-filled fissure). Moreover, the fissure treatments included both small and big fissures. Compared to the soil group, the non-soil-filled fissure group had decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased net photosynthetic rate (Pn) and retained stable water use efficiency (WUE) at low water availability. However, there were no significant differences between the soil-filled fissure group and soil group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group decreased the root distribution in total and in the soil layer, and also increased WUE at low water availability. Across all treatments, fissure size had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. These results suggest that rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change.

Identification and variation analysis of the composition and content of essential oil and fragrance compounds in Phoebe zhennan wood at different tree ages.

Wood essential oil and wood products with special fragrances are high value-added forest products. Despite the availability of essential oil and volatile organic compounds (VOCs) from Phoebe zhennan wood, their variation and dependence on tree age have not been examined. After essential oil extraction and wood processing, the yields and compositions of essential oils and VOCs in wood from P. zhennan trees of different ages (10a, 30a, and 80a) were determined. The yield of essential oil from 30a wood was significantly greater than that from 10a and 80a wood. Liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) revealed 672 and 41 volatile compounds, respectively, in the essential oil and wood, the majority of which exhibited large fluctuations in relative content and composition depending on tree age. Sesquiterpenoids, fatty acids and conjugates may greatly contribute to the main components of essential oil from wood. Almost all major sesquiterpenoid compounds, such as caryophyllene α-oxide, eudesmo, and cubebene, were identified in the essential oils from the 30a and 80a wood, and their relative contents were much greater than those in the 10a wood. The main components of the wood fragrance were sesquiterpenoids. The types and relative contents of sesquiterpenoids from wood increased with tree age. These results suggest that choosing wood from trees of a suitable age will significantly improve the efficiency of wood utilization.

Boosting cadmium tolerance in Phoebe zhennan: the synergistic effects of exogenous nitrogen and phosphorus treatments promoting antioxidant defense and root development.

Plants possess intricate defense mechanisms to resist cadmium (Cd) stress, including strategies like metal exclusion, chelation, osmoprotection, and the regulation of photosynthesis, with antioxidants playing a pivotal role. The application of nitrogen (N) and phosphorus (P) fertilizers are reported to bolster these defenses against Cd stress. Several studies investigated the effects of N or P on Cd stress in non-woody plants and crops. However, the relationship between N, P application, and Cd stress resistance in valuable timber trees remains largely unexplored. This study delves into the Cd tolerance mechanisms of Phoebe zhennan, a forest tree species, under various treatments: Cd exposure alone, combined Cd stress with either N or P and Cd stress with both N and P application. Our results revealed that the P application enhanced root biomass and facilitated the translocation of essential nutrients like K, Mn, and Zn. Conversely, N application, especially under Cd stress, significantly inhibited plant growth, with marked reductions in leaf and stem biomass. Additionally, while the application of P resulted in reduced antioxidant enzyme levels, the combined application of N and P markedly amplified the activities of peroxidase by 266.36%, superoxide dismutase by 168.44%, and ascorbate peroxidase by 26.58% under Cd stress. This indicates an amplified capacity of the plant to neutralize reactive oxygen species. The combined treatment also led to effective regulation of nutrient and Cd distribution in roots, shoots, and leaves, illustrating a synergistic effect in mitigating toxic impact of N. The study also highlights a significant alteration in photosynthetic activities under different treatments. The N addition generally reduced chlorophyll content by over 50%, while P and NP treatments enhanced transpiration rates by up to 58.02%. Our findings suggest P and NP fertilization can manage Cd toxicity by facilitating antioxidant production, osmoprotectant, and root development, thus enhancing Cd tolerance processes, and providing novel strategies for managing Cd contamination in the environment.

Responses of water use efficiency of Chinese fir to mixed planting and meteorological factors

Chinese fir in China are generally inefficient plantations with single species, unreasonable stand density, and low productivity. The introduction of broadleaved species is usually adopted as a strategy to improve Chinese fir plantations. Taking the pure forests and mixed forests of the Guanshan Forest Farm in Jiangxi Province as example, we quantified the intrinsic water-use efficiency (iWUE) of trees based on the stable isotope carbon method, as well as its response to meteorological factors, and investigated the improvement of stand quality after introducing Phoebe zhennan into Chinese fir plantation. The results showed that the basal area increment was 0.23 cm2 in pure forest, being higher than that of 0.19 cm2 in mixed forest. The δ13C and iWUE of pure forest were -27.4‰ and 52.9%, respectively, being lower than those of -26.7‰ and 62.8% in the mixed forest. Tree δ13C in pure forest was more sensitive to changes in mean annual precipitation and mean annual relative humidity, while that in mixed forest was not significantly correlated with meteorological factors. Pure forest iWUE was positively correlated with mean annual temperature, mean annual atmospheric CO2 concentration, and mean annual maximum temperature, and negatively correlated with mean annual precipitation and mean annual relative humidity, while mixed forest iWUE was positively correlated with mean annual atmospheric CO2 concentration only. Our results indicated that pure forests was more sensitive to climate than mixed forests.

Comparative Metabolomics and Transcriptome Analysis Reveal the Fragrance-Related Metabolite Formation in Phoebe zhennan Wood.

Nanmu (Phoebe zhennan) has a unique fragrance and is a high-quality tree species for forest conservation. The types and contents of volatile compounds in different tissues of nanmu wood are different, and the study of its volatile metabolites can help us to understand the source of its fragrance and functions. In order to explore the metabolites related to the wood fragrance of nanmu and to find out the unique volatile substances in the heartwood, gas chromatography-mass spectrometry (GC-MS) was performed to analyze the non-targeted metabolomics in five radial tissues from the sapwood to the heartwood of nanmu. A total of 53 volatile metabolites belonging to 11 classes were detected in all tissues, including terpenes, aromatic hydrocarbons, organoheterocyclics, phenols, esters, organic acids, alcohols, alkaloids, alkane, indoles derivatives, and others. And most of the volatile metabolites were identified for the first time in nanmu wood. Among them, terpenes and aromatic hydrocarbons were the main volatile components. In addition, 22 differential metabolites were screened from HW and SW, HW, and TZ via metabolomic analysis. Among these DAMs, three volatile metabolites (cadinene, a sesquiterpenoid; p-cymene, a monoterpenoid; 1,3,5-triisopropylbenzene, an aromatic hydrocarbon) contributed heavily to the characteristic fragrance of the heartwood. Additionally, the expression of transcripts showed that the unigenes in the terpenoid biosynthesis pathway were especially up-regulated in the SW. Therefore, we speculated that fragrance-related metabolites were synthesized in SW and then deposited in heartwood during sapwood transformed to heartwood. The expression levels of transcription factors (e.g., WRKY, C2H2, NAC) acted as the major regulatory factors in the synthesis of terpenoid. The results lay the foundations for further studies on the formation mechanism of fragrance components in nanmu wood and also provide a reference for the further development and utilization of nanmu wood.

The Early Effect of Plant Density on Soil Physicochemical Attributes and Bacterial and Understory Plant Diversity in Phoebe zhennan Plantations

The effect of stand density on the soil bacterial community and diversity remains unclear. Spectrophotometry and full-length 16S rRNA sequences were used to determine the effects of planting density on soil physicochemical attributes and the diversity of soil bacterial and understory vegetation in a young Phoebe zhennan plantation at five densities. The findings showed that stand density had significant effects on the total nitrogen, ammonium nitrogen (NH4+-N), nitrate-nitrogen (NO3−-N), organic carbon, and the dominance and evenness of shrubs. Candidatus Udaeobacter and Candidatus Soilbacter were the two most common genera across the five stand densities. The density D5 (850 stems/hm2) demarcated from the others with a lower diversity of soil bacteria. Overall, the relatively low- and middle-density plantations were more conducive to complex and stable understory vegetation, bacterial communities, and soil nutrient cycles. The functional categories of the bacterial communities revealed a high proportion associated with chemoheterotrophy, aerobic chemoheterotrophy, and nitrogen fixation. Bacterial diversity and function were significantly influenced by soil pH, NH4+-N, NO3−-N, total phosphorus, and available phosphorus. However, there were no significant correlations between soil physicochemical attributes, understory vegetation, and bacterial diversity. Therefore, we speculated that the key drivers of the soil bacterial community were the soil physicochemical attributes and that stand density affected the soil bacterial community diversity by changing the soil physicochemical attributes. Overall, P. zhennan plantations with densities below 600 stems/hm2 were conducive to complex and stable soil bacterial communities and nutrient cycles.

Morphological and Phylogenetic Analyses Reveal Three New Species of Pestalotiopsis (Sporocadaceae, Amphisphaeriales) from Hainan, China.

Species of Pestalotiopsis were mainly introduced as endophytes, plant pathogens or saprobes from various hosts. In this study, ten strains were isolated from Ficus macrocarpa, Phoebe zhennan and Spatholobus suberectus in China. Based on multilocus phylogenies from the internal transcribed spacer (ITS), the partial translation elongation factor 1-alpha gene (tef1α) and the partial beta-tubulin gene (tub2), in conjunction with morphological characteristics, we describe three new species, viz., Pestalotiopsis ficicola sp. nov., P. phoebes sp. nov. and P. spatholobi sp. nov.

Geographical origin classification of Phoebe zhennan and Phoebe bournei by solid phase micro-extraction and gas chromatography-mass spectrometry

Phoebe zhennan and Phoebe bournei are favored for their fine-grain, insect resistance, special fragrance, not easily cracked and deformed, which had been widely used in furniture and construction. Wood authenticity regarding different varieties and geographical origins is increasingly becoming a concern for consumers. Due to the difference in wood quality characteristics and economic value of genus Phoebe species from different geographical origins, it is important to establish a fast, efficient, and reliable method to discriminate the geographical origin of Phoebe zhennan and Phoebe bournei. Solid phase micro-extraction (SPME) was used as sample preparation approach and gas chromatography-mass spectrometry (GC–MS) technique was employed to analyze the volatile compounds. As a result, a total of 40 volatiles were identified by SPME–GC–MS among Phoebe zhennan samples from four origins, while 34 substances identified among Phoebe bournei samples. The wood samples of Phoebe zhennan and Phoebe bournei from different major production areas in China were able be discriminated by GC–MS spectroscopy. This finding indicated that genus Phoebe species from different climate zones had different chemical composition, which verified that the SPME–GC–MS technique can be used to classify different species of wood with characteristic compounds.

Rhizosphere soil nutrients and bacterial community diversity of four broad-leaved trees planted under Chinese fir stands with different stocking density levels

ObjectiveRhizosphere soil nutrients and bacterial diversity of four broad-leaved tree species underplanted in Chinese fir plantation with different stand density levels were analyzed to reveal characteristics of the rhizosphere soil environment and selection of suitable underplanted tree species.MethodsChinese fir plantation with three density levels (900, 1,200, and 1,875 stems ha–1, respectively) were selected and underplanted with Michelia macclurei, Schima superba, Phoebe zhennan, and Tsoongiodendron odorum. The rhizosphere soil nutrients and bacterial community of the broad-leaved tree species were determined after 4 years.ResultsSignificant differences in rhizosphere nutrient content were detected among different tree density levels, where the contents of total K, available K and available P in 900 stems ha–1 stands were significantly higher than the other stocking density levels. There were also significant differences in the contents of total C, total N, total K, available K and available P in the rhizosphere soils of the four trees species, while there were no significant differences in pH and total P. Rhizosphere soil nutrient contents were higher under S. superba and M. macclurei than under P. zhennan and T. odorum. The rhizosphere soil nutrient contents and bacterial diversity decreased with the increase of stand density, and the bacterial diversity showed significant differences in the rhizosphere soils of P. zhennan, T. odorum and S. superba when underplanted in different stand densities. The bacterial diversity was positively correlated with the available P content of rhizosphere soils, suggesting that soil available P content plays an important role in shaping the structure of bacterial community.ConclusionThe nutrient contents and bacterial diversity of rhizosphere soils of underplated broad-leaved species decreased with increasing stand density of Chinese fir plantation. Rhizosphere soils of M. macclurei and S. superba were rich in nutrient contents and bacterial diversity. Thus, low density of Chinese fir plantation (900 stems ha–1) underplanted with M. macclurei and S. superba is suitable for the establishment of mixed forest, which will facilitate better tree growth and maintaining soil fertility to realize sustainable management of forests.

桢楠幼苗适应喀斯特岩溶裂隙生境及降雨时间格局变化的方式

PDF HTML阅读 XML下载 导出引用 引用提醒 桢楠幼苗适应喀斯特岩溶裂隙生境及降雨时间格局变化的方式 DOI: 10.5846/stxb202112183590 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 重庆市自然科学基金面上项目（cstc2020jcyj-msxmX0244）；中央高校基本科研业务费专项（XDJK2020B037）；国家自然科学基金项目（31500399） Phoebe zhennan S. Lee seedlings adjust the biomass allocation and root distribution to adapt to the karst fissure habitat and rainfall temporal pattern Author: Affiliation: Fund Project: General Project of Chongqing Natural Science Foundation(cstc2020jcyj-msxmX0244);Special Funds for Fundamental Scientific Research Operation of Central Universities(XDJK2020B037);National Natural Science Foundation of China(31500399) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:喀斯特生态系统是全球陆地生态系统的重要组成部分，生态环境极为脆弱。由于碳酸盐岩长期强烈的化学溶蚀作用，其基本特征体现为地表土壤和地下岩溶裂隙及洞穴的二元结构。近年来，在全球气候变化下，我国西南地区降雨格局呈现降雨频次减少且单次降雨量增加的趋势。因此，岩溶裂隙和区域降雨时间格局改变将对喀斯特地区的植物生长产生重要影响。通过模拟不同岩溶裂隙生境（S0：24 cm土壤；S1/2：12 cm土壤层+12 cm裂隙层；S3/4：6 cm土壤层+18 cm裂隙层）和不同降雨时间格局（I2d：2 d降雨间隔；I19d：19 d降雨间隔），探究二年生桢楠（Phoebe zhennan S.Lee）幼苗是否通过生物量分配及根系分布的调整来适应变化环境。结果显示：（1）短时间降雨格局下，相比全土生境，少量岩溶裂隙存在并不影响桢楠幼苗生物量的积累，然而随着岩溶裂隙层进一步增厚和降雨时间间隔延长，桢楠降低了总生物量，减少了茎且增大了根和叶的生物量分配。（2）桢楠幼苗的根系垂直分布随着深度增加而下降，且无论在何种降雨时间格局下，两种岩溶裂隙生境下桢楠均增加了岩溶裂隙之上土壤层的根系生物量分配比例。研究表明：赋存有土壤的岩溶裂隙能成为植物幼苗赖以生存的生境，但这种提供生境的能力随岩溶裂隙层增厚以及降雨时间间隔延长而减弱。桢楠幼苗以牺牲对茎生物量的分配投资为代价，提高对根系或者叶片的生物量投资，同时增大界面土层中的根系分布，来保证最大化地利用有限的土壤资源，从而适应喀斯特的岩溶裂隙（及干旱）生境。 Abstract:Karst is one of the most important fragile ecological environments in globally terrestrial ecosystems. It is basically characterized by the dual structure of surface soil and underground karst fissures and caves, due to the long-term strong chemical dissolution of carbonate rocks. In recent years, under global climate change, the rainfall pattern in southwestern China has shown a trend of decreasing rainfall frequency and greater sub-rainfall. The karst region in southwestern China, which belongs to the subtropical monsoon climate, often suffers from more obvious alternating wet and dry conditions. The underground karst fissures and variation in the temporal pattern of regional rainfall will have a significant impact on plant growth and development in this region. In this study, in order to explore whether the seedlings of Phoebe zhennan S. Lee adjust biomass allocation and root distribution to adapt to the changing environment, we simulated different karst fissure habitats (S0:24 cm soil; S1/2:12 cm soil layer+12 cm karst fractured layer; S3/4:6 cm soil layer+18 cm karst fractured layer) and different rainfall temporal patterns (I2d:rainfall interval of 2 days; I19d:rainfall interval of 19 days), and checked the plants biomass accumulation and allocation, root vertical distribution. The results showed that:(1) under the short-term rainfall pattern, compared with the whole soil habitat, the habitat with a small proportion of karst fissures did not affect the biomass accumulation of P. zhennan seedlings. With the thickening of karst fractured layer and the extension of the rainfall interval, P. zhennan reduced the total biomass, allocating less biomass to stems and more to roots and leaves. (2) The vertical distribution of root system of P. zhennan seedlings decreased with the deepen of soil layer, but increased the root biomass allocation ratio in the soil layer above the karst fissures, regardless of the rainfall temporal pattern. The results show that the fissures hosted soil can be a certain habitat for plants. However, with the thickening of fractured layer and extension of the rainfall interval, the fissures weaken the ability of the habitat. P. zhennan seedlings increase investment to root and leaf at the expense of stem biomass, and increase the root distribution in the interface soil layer above the fissures to ensure the maximum use of limited soil resources so as to adapt to the fissure (and arid) habitat in karst. 参考文献 相似文献 引证文献

Environmental Factors Driving the Spatial Distribution Pattern of Venerable Trees in Sichuan Province, China.

Venerable trees are important natural resources and cultural heritage, offering historical, ecological, social and economic value. However, global warming and anthropogenic activities have threatened their welfare and survival. A comprehensive understanding of their current and future spatial patterns, vis-á-vis environmental conditions, can inform the co-management of sustainable resource use and conservation. We employed the existing spatial occurrence data and environmental variables (bioclimate and elevation) to simulate the optimal habitats for venerable trees in China's Sichuan Province. We evaluated the current and future climate scenarios of 2100 with double CO2 concentration. The BIOCLIM and QGIS spatial analyses assessed the primary factors of geographical distribution. The results identified 10,720 venerable trees from 123 species, 81 genera and 42 families. Cupressus funebris dominated, with the maximum importance value, followed by Ginkgo biloba, Ficus virens var. sublanceolata, and Phoebe zhennan. The elevation distribution of tree abundance and species richness demonstrated a unimodal pattern, skewing to the low-elevation end, with a concentration in the 600-1500 m low-medium altitude. The majority of trees and excellent habitats were found in eastern Sichuan with a less harsh terrain and climate. The bio3 (isothermality) and bio7 (temperature annual range) factors significantly influenced tree occurrence. Temperature imposed a greater effect on distribution than moisture under the current climate scenario. For the future climate-change scenario, the suitable habitats were predicted to maintain an overall stable pattern, with largely contiguous expansions of better habitats. However, climate warming would shrink the excellent habitats on the plains. The findings can inform strategies and guidelines for venerable-tree conservation in Sichuan. Furthermore, vulnerable areas could be identified. The future range expansion sites could be enlisted to cultivate new trees to replenish the venerable-tree pool. Habitat patches that remain sustainable could provide refugia with the potential for protected-area designation.

Effects of natural ageing on macroscopic physical and mechanical properties, chemical components and microscopic cell wall structure of ancient timber members

The main objective of this study was to investigate the effects of natural ageing on macroscopic physical and mechanical properties, chemical components, and microscopic cell wall structure of larch (Larix principis-rupprechtii Mayr) and nanmu (Phoebe zhennan S. Lee) timber members in ancient architecture. In this work, aged larch and nanmu timber members were obtained from the restoration architecture and their ages were determined based on accelerated mass spectrometer 14C method. Macroscopic physical, mechanical properties and chemical components were tested and determined of each timber members; meanwhile, the microstructural changes of cell wall were observed by scanning electron microscope (SEM). Finally, Pearson’s correlation analysis was conducted to reveal the relationships among them. The results indicated that natural ageing has a significantly effect on the macroscopic physical and mechanical properties, chemical components, and microscopic cell wall structure. First, equilibrium moisture content (EMC), the coefficient of wet swelling coefficient (SW) and colour parameters considerably changed of larch and nanmu timber members with aging years. Mechanical property parameters of larch timber show a significant decrease, and the changes of chemical components and microstructure of cell structure of nanmu specimens indicates the mechanical property parameters decreased. Further, the relative contents of cellulose and hemicellulose were significantly reduced, obvious damage and deformation were observed in the cell wall of larch and nanmu timber specimens. The results explained the change of macroscopic physical and mechanical properties, especially negative effects on mechanical properties. It was concluded that the relative contents of cellulose and hemicellulose were decreased, and the microstructure was damaged under the natural ageing effect, resulting in a decrease in mechanical properties with an increase in colour properties and dimensional stability.

Ancient plastid genomes solve the tree species mystery of the imperial wood “Nanmu” in the Forbidden City, the largest existing wooden palace complex in the world

Societal Impact StatementCombining natural and social science approaches to conduct archeological research on wooden cultural relics is important for exploring major aspects of ancient civilizations. The Forbidden City in Beijing, China, is the largest existing wooden palace complex in the world. We examined ancient DNA of imperial wood “Nanmu” specimens taken from representative structural components of the Forbidden City, in order to provide a new perspective on the long‐standing dispute about its species. This allowed us to accurately identify and properly restore these wooden artifacts and improved our understanding of the past interactions between plant distribution, forest resources, and human activities.Summary Exploring the life styles and production methods of past generations using plant resources can help us to improve our understanding of human civilization. Nanmu, known for its high wood quality, was exclusively used for imperial palace construction in the 15th–19th centuries in China, yet its species has been a subject of long‐standing debate. Here, we revisit this unresolved problem, using morphology and ancient DNA (aDNA) to analyze 21 centuries‐old Nanmu specimens sampled from representative palaces of the Forbidden City. Cytochemical staining demonstrated that endogenous aDNA sporadically occurs in the wood ray parenchyma cells of Nanmu specimens. High‐quality plastid genomes were retrieved from archeological woods for the first time via an aDNA capture method, with 90%–100% coverage (137,663–152,805 bp) and sequence depths of 27.05‐ to 1409.94‐fold. Utilizing these ancient genomes, our results demonstrate that Phoebe zhennan and Phoebe hui are most likely the main species of Nanmu in the Forbidden City. This finding diverges from the prevailing view that Nanmu encompasses woods from the whole genus Phoebe and even its close relative Machilus. It also shows that stringent criteria were used when selecting construction materials for the Forbidden City. By combining morphological traits with aDNA analyses, we provide a new solution for identifying the species of timber used for ancient architecture, and we increase our understanding of the way in which forest resources were recognized and utilized by our ancestors despite the lack of a plant taxonomic framework in ancient times.

Genetic Diversity of Nanmu (Phoebe zhennan S. Lee. et F. N. Wei) Breeding Population and Extraction of Core Collection Using nSSR, cpSSR and Phenotypic Markers

Genetic characterization is vital for tree germplasm utilization and conservation. Nanmu (Phoebe zhennan S. Lee. et F. N. Wei) is an extremely valuable tree species that can provide logs for many industrial products. This study aimed to assess the genetic diversity of a Nanmu breeding population using nine nSSR, five newly-developed cpSSR markers, and nine phenotypic traits, and extract a core collection. In general, the Na, Ne, and PIC for each nSSR/cpSSR were 2–37/2–3, 1.160–11.276/1.020–1.940, and 0.306–0.934/0.109–0.384, respectively. Fifteen chlorotype haplotypes were detected in 102 germplasms. The breeding population exhibited a relatively high level of genetic diversity for both nSSR (I = 1.768), cpSSR (I = 0.440, h = 0.286), and phenotypic traits (H′ = 1.98). Bayesian and cluster analysis clustered these germplasms into three groups. The germplasms revealed a high level of admixture between clusters, which indicated a relatively high level of gene exchange between germplasms. The F value (0.124) also showed a moderate genetic differentiation in the breeding population. A core collection consisting of 64 germplasms (62.7% of the whole germplasm) was extracted from phenotypic and molecular data, and the diversity parameters were not significantly different from those of the whole germplasm. Thereafter, a molecular identity was made up for each core germplasm. These results may contribute to germplasm management and conservation in the Nanmu breeding program, as well as genetics estimation and core collection extraction in other wood production rare species.

Variations of rhizosphere and bulk soil microbial community in successive planting of Chinese fir (Cunninghamia lanceolata).

Successive planting and monoculture, as common forest management methods, are widely used globally, especially in Chinese fir plantations in the subtropical areas of southern China. Although soil fertility depletion and productivity decline caused by successive planting have been widely reported, the underlying mechanism is still ambiguous. In this study, the composition and diversity of soil microorganisms (rhizosphere and bulk soils) in Chinese fir seedlings exposed to successive planting soils (first-generation Chinese fir seedings, FCP. second-generation Chinese fir seedings, SCP. third-generation Chinese fir seedings, TCP) and broadleaf tree species soil (Phoebe zhennan S. Lee et F. N. Wei, CK) were examined with high-throughput sequencing technology. Our findings revealed that the diversity and richness of bacterial and fungal communities were remarkably reduced in TCP than FCP and SCP, and were remarkably different between FCP and SCP. At the phylum level, the fungi with greatest relative abundance were Basidiomycota (5.74–32.88%) and Ascomycota (57.63–87.38%), while the bacteria with the greatest relative abundance were Acidobacteria (23.16–31.17%) and Proteobacteria (24.71–29.32%) for all treatments in both soil types. Additionally, the relative abundance of some pathogens (Penicillium and Burkholderia) was significantly higher in TCP than in FCP and SCP, suggesting that the presence of pathogens is an important factor in increasing the incidence of soil-borne sickness. Moreover, changes in fungal and bacterial communities were predominantly driven by soil dissolved organic carbon (DOC), DOC/DON ratio (DOCN), NO3–-N, microbial biomass carbon (MBC), and MBC/MBN ratio (MBCN). Overall, the long-term monoculture of Chinese fir promotes the microecological imbalance of rhizosphere and bulk soil, and remarkably reduced soil microbial community diversity. These results can provide a scientific support for the implementation of future management measures for fir plantations (e.g., fertilization, addition of microbial fungicides, and construction of mixed forests).

Phosphorus fertilization of Phoebe zhennan seedlings under drought reduces nitrogen assimilation

Phosphorus (P) limitation and water stress can affect trees’ growth, yet differing levels of nutrition under drought may have negative or positive effects on their growth and metabolism. This study aimed to evaluate the impact of P nutrition upon growth and metabolism in drought-stressed Phoebe zhennan (an endangered forest tree species) seedlings, to provide a basis for strengthening its conservation in the face of future climate change. A complete randomized design was used to investigate the effects of four different levels of P fertilization (no P, low P, moderate P, and high P) under water stress on the growth, photosynthesis, and nitrogen metabolism of P. zhennan. Drought-stressed seedlings under high P (HP) application had enhanced growth, while moderate P (MP) application improved their root biomass and leaf area only, whereas low P (LP) did not significantly affect any growth trait. Moreover, HP fertilization had positive effects on leaf relative water contents (LRWCs), while HP and MP both significantly improved photosynthetic traits vis-à-vis non-fertilized seedlings. The concentration of soluble sugars was significantly higher in non-fertilized than fertilized seedlings as were nitrogenous compounds (NO3 − and NH4 +) and nitrogen metabolic enzymes (NR, GDH, GOGAT, and GS) activities. Both NO3 −and NH4 +concentrations were significantly decreased under HP application compared with the non-fertilized counterparts. The plant traits improved under HP application counteracted the adverse impact of low nitrate availability and promoted seedling growth. Low-dose fertilization produces depressive effects in P. zhennan, but a high P concentration can overcome those negative effects to improve growth.