Fargesii Var Research Articles

Two previously undescribed cholestanol saponins from the rhizomes of Paris fargesii var. petiolata

Two previously undescribed cholestanol saponins, parpetiosides F − G (1–2), and six known analogs (3–8) were isolated from the rhizomes of Paris fargesii var. petiolata. Their structures were elucidated by extensive spectroscopic data analysis and chemical methods. Compound 1 was a rare 6/6/6/5/5 fused-rings cholestanol saponin with disaccharide moiety linked at C-26 of aglycone which was hardly seen in genus Paris. All of these compounds were discovered in this plant for the first time. In addition, the cytotoxicities of saponins (1–8) against three human cancer cell lines (U87, HepG2 and SGC-7901) were evaluated by CCK-8 method, and saponins 5–8 displayed certain cytotoxicities. The strong interactions between saponins 5–8 and SCUBE3, an oncogene for glioma cells, were displayed by molecular docking.

Peripatric speciation within Torreya fargesii (Taxaceae) in the Hengduan Mountains inferred from multi-loci phylogeography

BackgroundThe Hengduan Mountains (HDM) are one of the major global biodiversity hotspots in the world. Several evolutionary scenarios, especially in-situ diversification, have been proposed to account for the high species richness of temperate plants. However, peripatric speciation, an important mode of allopatric speciation, has seldom been reported in this region.ResultsHere, two chloroplast DNA regions and 14 nuclear loci were sequenced for 112 individuals from 10 populations of Torreya fargesii var. fargesii and 63 individuals from 6 populations of T. fargesii var. yunnanensis. Population genetic analyses revealed that the two varieties are well differentiated genetically (FST, 0.5765) and have uneven genetic diversity (π, 0.00221 vs. 0.00073 on an average of nuclear loci). The gene genealogical relationship showed that T. fargesii var. yunnanensis is inferred as derived from T. fargesii var. fargesii, which was further supported by the coalescent simulations (DIYABC, fastsimcoal2 and IMa2). By the coalescent simulations, the divergence time (~ 2.50–3.65 Ma) and the weak gene flow between the two varieties were detected. The gene flow was asymmetrical and only occurred in later stages of divergence, which is caused by second contact due to the population expansion (~ 0.61 Ma) in T. fargesii var. fargesii. In addition, niche modeling indicated that the two varieties are differentiated geographically and ecologically and have unbalanced distribution range.ConclusionsOverall, T. fargesii var. fargesii is always parapatric with respect to T. fargesii var. yunnanensis, and the latter derived from the former in peripatry of the HDM following a colonization from central China during the late Pliocene. Our findings demonstrate that peripatric speciation following dispersal events may be an important evolutionary scenario for the formation of biodiversity hotspot of the HDM.

Temporal Variability in Soil Greenhouse Gas Fluxes and Influencing Factors of a Primary Forest on the Eastern Qinghai-Tibetan Plateau

Soil greenhouse gas (GHG) fluxes relate to soil carbon and nitrogen budgets and have a significant impact on climate change. Nevertheless, the temporal variation and magnitude of the fluxes of all three major GHGs (CO2, CH4 and N2O) and their influencing factors have not been elucidated clearly in primary forests on the eastern Qinghai-Tibetan Plateau. Herein, field chamber GHG fluxes from May to November, soil microbial community and enzyme activity were analyzed in a fir-dominated (Abies fargesii var. faxoniana) primary forest. The emission rates of CO2 and N2O ranged between 64.69–243.22 mg CO2 m−2 h−1 and 1.69–5.46 ug N2O m−2 h−1, exhibiting a temporally unimodal pattern with a peak in July. The soil acted as a CH4 sink, and the uptake rate varied between 52.96 and 84.67 μg CH4 m−2 h−1 with the higher uptake rates in June and November. The temporal variation in the CO2 flux was significantly correlated with the geometric mean of enzyme activities, suggesting that the soil CO2 flux was determined by microbial activity rather than soil microbial biomass. The soil N2O flux was positively related to nitrate concentration with marginal significance, probably because N2O was a byproduct of nitrification and denitrification processes. The soil CH4 uptake was closely associated with methanotrophic biomass (18:1ω7c). The results highlight divergent temporal dynamics of GHG fluxes owing to different driving mechanisms and an important CH4 sink in the primary forest soil, helping to evaluate the carbon and nitrogen budgets of primary forests on the eastern Qinghai-Tibetan Plateau.

Rohdea brachyanthera (Asparagaceae), a new species from Guangdong, southern China

Rohdea brachyanthera, a new species from Nanling National Reserve of northern Guangdong, China, is described and illustrated. It is most similar to R. fargesii var. tsinlingensis in the perianth tube bearing an appendage at apex and the stamens are attached to it, but differs in the smooth inner surface of the perianth and stamens; the presence of six rib-like protrusions on the internal surface of the perianth tube; a ring-shaped, succulent appendage that is outwardly swollen and smooth on the surface and dilated triangular filaments that are united with the appendages at the base. Information on the habitat and phenology as well as notes on the taxonomic relationships with other congeners is also provided.

Spatial variations in ectomycorrhizal fungi and host tree reciprocal relations are associated with the local distribution patterns of Minjiang fir

Ectomycorrhizal fungi (ECMF) can help maintain the natural range of host trees by assisting their occupancy in the boundary of distribution. However, it is unclear whether the boundary-dependent variations in ECMF communities and their relationships with hosts are associated with the patterns of local-scale host tree distributions. In this study, we investigated the community structure of ECMF in the root tips of the Minjiang fir (Abies fargesii var. faxoniana) saplings, and examined the variations in root-associated ECMF communities and their relationships with the fir saplings along environmental gradients from the centric suitable habitats (SH) on shady slopes to range boundaries (RB) at the upper and lower elevations of the SH and on sunny slopes. We found that both the SH and the upper RB were enriched by the ECMF taxa in the genus Cortinarius, which were positively correlated with the basal diameter (BD) of the firs. In contrast, the lower RB of the shady slopes and the sunny slopes harbored a higher abundance of the ECMF taxa in the genus Tylospora, which were negatively correlated with the BD of the firs. The relationships between the firs and some of the same ECMF species, such as Cortinarius balaustinus and Cortinarius casimiri, shifted from positive at the SH to negative at the lower RB of the shady slopes and on sunny slopes. Soil properties differed between habitat types, so do the relationships of soil properties with ECMF communities. These marginal alterations in ECMF communities and their relationships with the fir saplings were not explainable by changes in soils. Our study highlighted habitat-dependent shifts in root-associated ECMF communities and their correlations with Minjiang fir saplings from suitable habitats to range boundaries. The results suggest that these marginal patterns may be associated with variations in habitats rather than current soil properties for Minjiang firs. The spatial variations in ECMF communities and their relationships with fir saplings could be useful indicators for identification of the site suitability for Minjiang fir regeneration and conservation.

Reinstatement of the Chinese species Rohdea yunnanensis (Asparagaceae)

Examination of living populations and herbarium specimens (including type material) of Rohdea yunnanensis and R. fargesii has revealed that the two species are morphologically very distinct from each other. We therefore reinstate the independent specific status of R. yunnanensis which has been placed in synonymy with R. fargesii var. fargesii. In former species, the blade margin denticulate; bract base branched or erose; perianth lobe also erose and denticulate; fruit conical and seed reniform, hilum oblique.

Optimizing Observation Plans for Identifying Faxon Fir (Abies fargesii var. Faxoniana) Using Monthly Unmanned Aerial Vehicle Imagery

Faxon fir (Abies fargesii var. faxoniana), as a dominant tree species in the subalpine coniferous forest of Southwest China, has strict requirements regarding the temperature and humidity of the growing environment. Therefore, the dynamic and continuous monitoring of Faxon fir distribution is very important to protect this highly sensitive ecological environment. Here, we combined unmanned aerial vehicle (UAV) imagery and convolutional neural networks (CNNs) to identify Faxon fir and explored the identification capabilities of multispectral (five bands) and red-green-blue (RGB) imagery under different months. For a case study area in Wanglang Nature Reserve, Southwest China, we acquired monthly RGB and multispectral images on six occasions over the growing season. We found that the accuracy of RGB imagery varied considerably (the highest intersection over union (IoU), 83.72%, was in April and the lowest, 76.81%, was in June), while the accuracy of multispectral imagery was consistently high (IoU > 81%). In April and October, the accuracy of the RGB imagery was slightly higher than that of multispectral imagery, but for the other months, multispectral imagery was more accurate (IoU was nearly 6% higher than those of the RGB imagery for June). Adding vegetation indices (VIs) improved the accuracy of the RGB models during summer, but there was still a gap to the multispectral model. Hence, our results indicate that the optimized time of the year for identifying Faxon fir using UAV imagery is during the peak of the growing season when using a multispectral imagery. During the non-growing season, RGB imagery was no worse or even slightly better than multispectral imagery for Faxon fir identification. Our study can provide guidance for optimizing observation plans regarding data collection time and UAV loads and could further help enhance the utility of UAVs in forestry and ecological research.

Cytotoxic steroidal saponins from the rhizomes of Paris fargesii var. Petiolata

Phytochemical investigation on the rhizomes of Paris fargesii var. petiolata (Baker ex C. H. Wright) Wang et Tang led to the isolation of five previously undescribed steroidal saponins, parpetiosides A–E (1–5), and six known analogs (6–11). Their structures were established by extensive spectroscopic data analysis and chemical methods. Compound 5 was a rare steroidal saponin with disaccharide moiety linked at C-26 of dehydrokryptogenin that was hardly seen in the genus Paris. The cytotoxicities of the isolated compounds against three human cancer cell lines (U87, HepG2 and SGC-7901) were evaluated, and compound 1 displayed certain inhibitory effect with IC50 values of 8.02 ± 0.45, 8.24 ± 0.57 and 6.20 ± 0.79 μM, respectively. Moreover, the preliminary mechanism of 1 inhibiting the proliferation of the three cancer cell lines might be related to cell cycle distribution and the induction of S phase arrest.

The Contributions of Soil Fauna to the Accumulation of Humic Substances during Litter Humification in Cold Forests

Litter humification is an essential process of soil carbon sequestration in forest ecosystems, but the relationship between soil fauna and humic substances has not been well understood. Therefore, a field litterbag experiment with manipulation of soil fauna was carried out in different soil frozen seasons over one year in cold forests. The foliar litter of four dominated tree species was selected as Birch (Betula albosinensis), Fir (Abies fargesii var. faxoniana), Willow (Salix paraplesia), and Cypress (Juniperus saltuaria). We studied the contribution of soil fauna to the accumulation of humic substances (including humic acid and fulvic acid) and humification degree as litter humification proceeding. The results showed that soil fauna with litter property and environmental factor jointly determined the accumulation of humic substances (humic acid and fulvic acid) and humification degree of four litters. After one year of incubation, the contribution rates of soil fauna to the accumulation of humic substances were 109.06%, 71.48%, 11.22%, and −44.43% for the litter of fir, cypress, birch, and willow, respectively. Compared with other stages, both growing season and leaf falling stage could be favorable to the contributions of soil fauna to the accumulation of humic substances in the litter of birch, fir, and cypress rather than in willow litter. In contrast, the contribution rates of soil fauna to humification degree were −49.20%, −7.63%, −13.27%, and 12.66% for the litter of fir, cypress, birch, and willow, respectively. Statistical analysis indicated that temperature changes at different sampling stages and litter quality exhibited dominant roles in the contributions of soil fauna on the accumulation of humus and litter humifiaction degree in the cold forests. Overall, the present results highlight that soil fauna could play vital roles in the process of litter humification and those strengths varied among species and seasons.

Interactive effects of citric acid and mineral fertilization on soil microbial carbon use efficiency in the rhizosphere of two coniferous species

Soil microbial carbon use efficiency (CUE) has been identified as a critical parameter in regulating soil organic carbon (SOC) sequestration. Climate change has been shown in numerous studies to increase the input of root exudates into the soil, thereby affecting soil communities and soil carbon (C) balance. However, it remains uncertain how citric acid (a major component of root exudates) impacts the microbial CUE in forest soil under different soil fertility conditions. Hence, we investigated the responses of soil microbial community composition, enzyme activity, and microbial CUE to a 2-year citric acid addition and mineral fertilization experiment in the rhizospheres of Abies fargesii var. faxoniana and Picea purpurea. Citric acid addition had no significant effects on the C: nutrient imbalance between microbial biomass and their resources in fertilized soils, but it increased the microbial C: nutrient imbalance in non-fertilized soils. The effects of citric acid on microbial CUE were influenced by soil fertility. Citric acid addition had a significant negative effect on microbial CUE in non-fertilized soils in both species tested, whereas no significant change in this parameter was observed in soil treated with NPK fertilizers. NPK fertilization can reduce citric acid-induced soil C loss by increasing microbial CUE. The microbial CUE of P. purpurea was lower than that of A. faxoniana. The differences in root C allocation, the C:N ratio of fine root and root exudates, and N uptakes may contribute to tree species variation in microbial CUE. Our findings contribute to a better understanding of the processes governing the impacts of C and nutrient inputs on microbial C cycles in subalpine conifer forest soils.

Study of the genus Torreya (Taxaceae) based on chloroplast genomes.

Species of the genus Torreya are similar in morphology, and their morphological taxonomic characteristics are not stable because of environmentally induced changes. Therefore, morphology is insufficient for understanding their relationships. Chloroplast genome sequencing technology provides a powerful tool for molecular analysis to get more infomation for classification and identification of Torreya genus. A total of 4 chloroplast genome of Torreya, including T. Parvifolia, T. nucifera, T. fargesii var. Yunnanensis and T. grandis var. jiulongshanensis, were sequenced and annotated. Campartive genome and phylogenetic tree were provided for variation analysis. The chloroplast genome size of the four samples is about 137 kb, the inverted repeat (IR) regions are identified in the genus Torreya. Genome comparison using mVISTA showed high sequence similarity among different species. Regions with divergence in exon regions include accD, ndhB, ndhF, psbA, psbJ, rpl2, rps3, rps16, rps18, ycf1, and ycf2. The phylogenetic tree based on 73 single-copy genes showed a clearer relationships among different species of Torreya. All genomes of the four Torreya species consist of two short IR regions, and results of the phylogenetic analysis concluded that T. parvifolia should be considered as T. fargesii var. yunnanensis or treated as a sister species. T. grandis var. jiulongshanensis should be treated as a variety of T. grandis according to molecular evidence, supporting the originally published proposal.

川西米亚罗亚高山暗针叶林岷江冷杉和糙皮桦空间格局及其关联性分析

PDF HTML阅读 XML下载 导出引用 引用提醒 川西米亚罗亚高山暗针叶林岷江冷杉和糙皮桦空间格局及其关联性分析 DOI: 10.5846/stxb202103220756 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项（CAFYBB2016MA004，CAFZC2017M004）；国家重点研发计划课题（2016YFC0502104） Spatial patterns and associations of main dominant species Abies fargesii var. faxoniana and Betula utilis in Miyaluo subalpine dark coniferous forest of western Sichuan, China Author: Affiliation: Fund Project: 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:基于2019年9月完成的川西米亚罗亚高山暗针叶林9.6 hm2动态样地的调查数据，分析了主要优势种岷江冷杉（Abies fargesii var.faxoniana）与糙皮桦（Betula utilis）的径级结构，并运用O-ring统计中的成对相关函数g（r）和g12（r），研究了两个优势种的空间格局及其种内、种间的关联性。结果表明：岷江冷杉与糙皮桦径级分布连续，均呈倒"J"型。岷江冷杉与糙皮桦的不同径级个体主要呈现由聚集分布向随机分布发展的趋势。岷江冷杉的小树对幼树、中树对幼树、中树对小树以及大树对中树的种内相关性在所有空间尺度上均为显著正相关（P<0.05），而相同径级糙皮桦的种内相关性则表现为由显著正相关（P<0.05）逐渐向无显著相关（P>0.05）变化。随着空间尺度的增大，岷江冷杉的大树对幼树、大树和小树由无显著相关（P>0.05）逐渐向显著正相关（P<0.05）变化，糙皮桦的大树对幼树由显著负相关（P<0.05）逐渐向无显著相关（P>0.05）变化。岷江冷杉大树对糙皮桦所有径级个体的种间相关性主要呈现由为显著负相关（P<0.05）逐渐向无显著相关（P>0.05）变化，糙皮桦大径级个体对所有径级的岷江冷杉主要呈现出显著负相关（P<0.05）。岷江冷杉和糙皮桦的空间格局及其关联性随径级、空间尺度的不同而变化。 Abstract:Based on the investigation data from a 9.6 hm2 Miyaluo dark coniferous forest dynamics plot in western Sichuan in September 2019, the diameter at breast height (DBH) size class structure of two dominant species Abies fargesii var. faxoniana and Betula utilis was analyzed. The spatial distribution, intraspecific and interspecific associations of the two dominant species with four different DBH size classes were also illustrated by using paired correlation functions g(r) and g12(r) in the O-ring statistics of spatial point pattern analysis. The DBH size class structure of the two dominant species showed continuously and a reverse "J" type distribution. The individuals of A. fargesii var. faxoniana and B. utilis with different DBH size classes mainly showed a tendency from aggregation distribution to random distribution. The interspecific relationships of A. fargesii var. faxoniana including small trees to saplings, medium trees to saplings, medium trees to small trees, big trees to medium trees showed positively spatial associations, while that of B. utilis presented a trend from significantly positive (P<0.05) to non-obvious associations (P>0.05). With the increase of spatial scale, the relationship between big trees to sapling and between big trees to small trees of A. fargesii var. faxoniana was from non-obvious to significantly positive associations (P<0.05). However, the big trees to saplings of B. utilis showed a change from significantly negative to non-obvious associations (P<0.05). In the meanwhile, the big trees of A. fargesii var. faxoniana to all DBH size classes individuals of B. utilis mainly showed a trend from significantly negative (P<0.05) to non-obvious associations. There were mainly significant negative associations (P<0.05) between individuals with big DBH size classes of B. utilis and all DBH size classes individuals of A. fargesii var. faxoniana (P<0.05). In short, the spatial distribution pattern and associations of A. fargesii var. faxoniana and B. utilis varied with the change of DBH size classes and the spatial scale. 参考文献 相似文献 引证文献

Altitudinal variations of hydraulic traits in Faxon fir (Abies fargesii var. faxoniana): Mechanistic controls and environmental adaptability

Global climate change has been seen to result in marked impacts on forest ecosystems such as accelerated tree mortality worldwide due to incidental hydraulic failure caused by intensified and more frequent occurrence of extreme drought and heat-waves. However, it is well understood how the tree hydrological strategies would adjust to environmental variability brough about by climate changes. Here we investigated the hydraulic adjustment as a mechanism of acclimation to different climate conditions along an altitudinal gradient in Faxon fir ( Abies fargesii var. faxoniana ) ― a tree species that plays a key role in conservation of wildlife and maintenance of ecosystem services in subalpine forests. The hydraulic traits and selective morphological and physiological variables were measured seasonally along an altitudinal gradient from 2,800 to 3,600 ​m a.s.l. We found that the native percentage loss of conductivity (PLC) increased with altitude across the seasonal measurements . Both the native sapwood-specific hydraulic conductivity ( K s ) and native leaf-specific hydraulic conductivity ( K l ) significantly decreased with altitude for measurements in July and October, coinciding with the timing for peak growth and pre-dormancy, respectively. The morphological traits varied toward more conservative tree hydrological strategies with increases in altitude, exhibiting trade-offs with hydraulic traits. The total non-structural carbohydrates in both needle (NSC Needle ) and branch (NSC Branch ) as well as photosynthetic capacity of current-year leaves played variable roles in maintaining the integrity of the hydraulic functioning and shaping the hydraulic adjustment under prevailing environmental conditions. Our findings indicate that Faxon fir possesses some degree of hydraulic adaptability to water limitation imposed by climate fluctuations in subalpine region through morphological and physiological modifications.

Effects of forest canopy density and epixylic vegetation on nutrient concentrations in decaying logs of a subalpine fir forest

Deadwood and the associated epixylic vegetation influence nutrient cycles in forest ecosystems. Open canopies strongly regulate deadwood decomposition and disrupt epixylic vegetation on logs. However, it is unclear how the forest canopy density and epixylic vegetation growth affect the nutrient concentrations in deadwood. We measured the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), and manganese (Mn) in experimentally exposed decaying logs placed in gaps, at the edge of gaps, and under the closed canopy during a four-year decomposition experiment in a Subalpine Faxon fir forest (Abies fargesii var. faxoniana) on the eastern Qinghai-Tibetan Plateau, China. To assess the effect of the epixylic vegetation, we experimentally removed it from half of the logs used in the study. Under open canopy conditions in the gap and at the edge, the concentrations for most of the nutrients in the bark and the highly decayed wood were lower than under the closed canopy. The effect of the epixylic treatment on nutrient concentrations for all but K and Na in barks varied with the decay classes. Significantly lower concentrations of N, P, Ca, and Mn following the removal of epixylic vegetation were observed in the wood of decay class IV. Epixylic vegetation significantly increased most nutrient concentrations for decaying barks and wood under open canopy conditions. In contrast, epixylic vegetation had no or minimal effects under the closed canopy. Forest canopy density and epixylic vegetation significantly alter the nutrient concentrations in decaying logs. Open canopies likely accelerate the rate of nutrient cycling between the epixylic vegetation and decaying logs in subalpine forests.

Seasonal and Altitudinal Variation in Non-Structural Carbohydrates of Faxon Fir (Abies Fargesii VAR. Faxoniana) at Wolong Nature Reserves in Sichuan Province, Southwest China

Seasonal and Altitudinal Variation in Non-Structural Carbohydrates of Faxon Fir (Abies Fargesii VAR. Faxoniana) at Wolong Nature Reserves in Sichuan Province, Southwest China

Has tree density increased at alpine treelines on the eastern Tibetan Plateau?

Treeline densification, along with increased growth rates, is considered a primary manifestation of climate warming at alpine treelines. However, treeline densification has typically been inferred from comparisons of present-day tree density with estimates of former densities inferred from current age structure; the densification has not been verified with long-term monitoring data and thus empirical testing is needed. In this study, a series of plots was established along an altitudinal gradient in a treeline ecotone on the eastern Tibetan Plateau; the plots were then surveyed repeatedly for ten years to analyse spatiotemporal variation in tree regeneration. The densities of Abies fargesii var. faxoniana seedlings and saplings increased from low altitude sites to high altitude sites, before dropping to zero beyond the treeline. The density of fir seedlings at the treeline in 2018 was significantly lower than in 2008. There were no significant differences in the density of saplings, small trees, medium trees, or old-growth trees between 2018 and 2008. As compared to regeneration patterns from 65 years ago, treeline densification represents a spatial phenomenon related to altitude, but not a temporal pattern on the eastern Tibetan Plateau. A more comprehensive understanding of the effects of climate warming on treeline regeneration will require further long-term monitoring and research.

Choices of ectomycorrhizal foraging strategy as an important mechanism of environmental adaptation in Faxon fir (Abies fargesii var. faxoniana)

Faxon fir (Abies fargesii var. faxoniana) is endemic to the cool and moist subalpine region of Southwest China, where the occurrence of warmer and drier climate may impose uncertain environmental constraints to its population stability and community scuccession. Here we determine the role of root-mycorrhizal symbiosis in the adaptability of Faxon fir to varying environmental conditions. The traits and foraging behaviors of the ectomycorrhizal (ECM) associations in Faxon fir were investigated along elevational gradient in three representative natural distributional areas of the species. Soil and Faxon fir root samples were collected from varying elevations in three study areas, namely Wolong Nature Reserve, Miyaluo Nature Reserve, and Wanglang Nature Reserve, in Sichuan province, Southwest China, using point-centered quarter sampling method, with 32 samples for each elevational site. Measurements were made on fine root biomass, ECM morphological diversity and soil exploration types, density and superficial area of ECM root tips, and soil chemistry. Values for selective climatic variables were derived from the national grid-datasets of meteorology of China. Principle component analysis (PCA), redundancy analysis (RDA) and linear regressions were performed to determine the inter-relationships of ECM root traits with climatic and soil factors, and the variations of the ECM root traits with elevation. We found that the biomass of absorptive fine roots and ECM morphological diversity decreased with rising elevations and increasing soil water content or precipitation and soil C:N ratio. The foraging ability of ECM roots, inferred by the soil exploration type of ECM symbionts, and density and superficial area of ECM root tips, were weakened by warming and drying. Under conditions of low N availability, both the frequency of contact exploration type and ECM root tip density prevailed, whilst the frequency of both short-distance and medium-distance exploration types tended to decline, suggesting conservative carbon cost of ECM root systems in low fertility soil. Overall, our findings suggest that the ECM symbionts in Faxon fir adopt the strategy of C investment in root systems in response to warming and drying while relying on the functional efficiency of the ECM root tips toward the colder and more humid environments, and that Faxon fir may sustain moderate changes in the regional climate and maintain population stability, partially owning to adjustment of the ECM foraging strategies.

The complete chloroplast genome of Torreya parvifolia, a species with extremely small population in China

Torreya parvifolia (Torreya, Taxaceae) is endemic in Sichuan, China. It consisted of an extremely small population with less than 100 wild individuals. In this study, the complete chloroplast genome of T. parvifolia was assembled using the Illumina data. The complete chloroplast genome of T. parvifolia is 137,106 bp in length. The genome consists of 119 genes in total, including 82 protein-coding genes (PCGs), 4 ribosomal RNA (rRNA) genes, and 33 transfer RNA (tRNA) genes. Phylogenetic analysis indicated that T. parvifolia was closely related to T. fargesii, T. nucifera, and T. fargesii var. yunnanensis with strong support.

Recent decline of high altitude coniferous growth due to thermo-hydraulic constrains: evidence from the Miyaluo Forest Reserve, Western Sichuan Plateau of China

Tree growth decline has been reported in many places around the globe under the context of increasingly warming climate, and strengthening drought intensity is detected to be the primary factor for such decline, particularly in northern forest sites, as well as arid and semi-arid areas. Yet, the forest growth decline in high altitude, high mountain sites certainly merits investigation. Here, we reported faxon fir (Abies fargesii var. faxoniana) forest growth decline (slope = -0.64) at the tree line (4150 m above sea level) in Miyaluo Forest Reserve (MFR) at the Western Sichuan Plateau, southwestern China since 2000. We investigated the cause of tree growth decline by applying dendrochronological approaches. We took tree-ring samples from fir trees at the tree line and developed tree-ring width (TRW) chronology. The tree growth – climate relationship analysis showed that maximum temperature (Tmax) was the primary factor limiting the radial growth of fir trees in the investigated area. The moving correlation analysis indicated the strengthening positive influence of Tmax, spring precipitation, and cloud cover during winter and monsoon period on radial growth since 2000s. Our results have shown that both thermal and hydraulic constrains accounted for the radial growth decline of fir trees at the tree line of MFR in the western Sichuan Plateau.

&lt;p&gt;&lt;strong&gt;Taxonomic notes on &lt;em&gt;Ilex&lt;/em&gt; sect. &lt;em&gt;Ilex&lt;/em&gt; (Aquifoliaceae) from China II: Revision of &lt;em&gt;I&lt;/em&gt;. &lt;em&gt;fargesii&lt;/em&gt; and related species based on molecular and morphological evidence&lt;/strong&gt;&lt;/p&gt;

Based on the results of phylogenetic reconstructions employing two nuclear ribosomal DNA loci (ITS and ETS), as well as morphological observation and comparisons of branches, leaves, inflorescences/infructescences and pyrenes, a taxonomic revision of three species of Ilex from China is conducted and presented herein. Ilex fargesii is subdivided into I. fargesii subsp. fargesii and I. fargesii subsp. melanotricha, with I. fargesii var. angustifolia and I. fargesii var. brevifolia newly treated as synonyms of the type subspecies. The split of the two subspecies of I. fargesii in the molecular phylogeny is conformed with their divergence in distribution, which is clearly separated by the Tanaka-Kaiyong Line. Similar geographic disjunction is also revealed in the two subspecies of I. wattii, i.e. I. wattii subsp. wattii and I. wattii subsp. marlipoensis. Meanwhile, I. gintungensis and I. venosa newly reduced to the synonyms of I. wattii subsp. wattii, and I. marlipoensis and I. cupreonitens to I. wattii subsp. marlipoensis. Furthermore, we confirm I. pubifructa to be a newly recorded species in China and I. denticulata to be excluded from China. Both our molecular and morphological analyses do not support the synonymization of I. chartaceifolia (including I. chartaceifolia var. glabra) and I. micropyrena with I. fargesii. However, the specific status of I. chartaceifolia and I. micropyrena is not resumed in this study because of their intricate and unclear relationships with I. dunniana, I. intermedia and I. subodorata.