Subtropical Area Of China Research Articles

Effects of Thinning on Carbon Storage in a Mixed Broadleaved Plantation in a Subtropical Area of China

Forest thinning is a widely used silvicultural method in forest management and has complex effects on carbon sequestration in different types of forest ecosystems. The present study examined the short-term effects of different thinning intensities on carbon storage in an 11-year-old mixed broadleaved plantation. The results partially supported that different thinning intensities have varying impacts on carbon storage in different parts of forest ecosystems. The main results were as follows: (1) The effect of thinning on promoting the growth of fast-growing tree species (Michelia macclurei Dandy and Schima superba Gardn. et Champ.) was earlier than that of slow-growing tree species (Castanopsis hystrix Miq.). (2) A greater thinning intensity conferred greater effects on promoting the tree biomass carbon growth, litter carbon storage, and understory plant diversity, in the order of 41%~50% > 31%~40% > 20%~30%, but these values were lower than those for the unthinned plots. (3) The soil carbon storage declined most in the 41%~50% thinned plots, due to the reduced carbon storage in the humus layer. (4) The 20%~30% thinning intensity promoted carbon sequestration in the short term in the mixed broadleaved plantation. The results suggested that a lower thinning intensity promoted carbon sequestration in the short term, a greater thinning intensity reduced carbon storage at first, but the negative effect on carbon storage exhibited trade-offs later by the growth of tree and understory plant biomass carbon and the accumulation of litter layer carbon.

Mycenabrunnescens (Basidiomycota, Mycenaceae), a new species of Mycena sect. Pterigenae from China.

Mycena (Pers.) Roussel (1806) is a large genus of Mycenaceae known for having small to medium-sized basidiomata. It is typified by the species Mycenagalericulata (Scop.) Gray. For years, many mycologists have made important contributions to understanding Mycena and several monographs have been published. Three specimens were collected from China that belonged to the genus Mycena. On the basis of morphological analysis and phylogenetic analyses employing DNA sequences, a new species is described. Mycenabrunnescens sp. nov. is described as a new species from subtropical areas of China. It is characterised by its brown pileus, whitish lamellae that turns brown when bruised, orange to brown lamellae edges, the absence of pleurocystidia and cheilocystidia with simple or branched excrescences at the apex containing yellowish-brown contents. We performed phylogenetic analyses on a concatenated dataset comprising the internal transcribed spacer and large subunit regions of nuclear ribosomal RNA using Bayesian Inference and Maximum Likelihood methods. The result showed that the new taxon clustered in an independent group and is closely related to M.albiceps and M.flosoides.

First report of Fusarium commune causing Torreya grandis crown and root rot in China

AbstractTorreya grandis cv. Merrillii is an important economic tree widely cultivated in hilly subtropical areas in China and some parts of Japan and Korea. Crown and root rot was found on T. grandis in Zhejiang Province of China. Three isolates with similar morphology were isolated from diseased samples, and used for identification and pathogenicity tests. The pathogenicity of the isolates was confirmed by fulfilling Koch's postulates. The pathogen was identified as Fusarium commune based on morphological characteristics and phylogenetic tree constructed by combining ITS and TEF‐1α gene sequences. This is the first report of F. commune causing crown and root rot on T. grandis in China.

Characteristics of iron (hydr)oxides and Cr(VI) retention mechanisms in soils from tropical and subtropical areas of China

Though both iron (hydr)oxides and soil organic matter (SOM) significantly influence heavy metal behaviors in soils, studies on the characteristics of natural minerals and the synergic effects of the two on Cr(VI) transformation are limited. This study investigated Cr(VI) retention mechanisms in four soils from tropical and subtropical regions of China based on a comprehensive characterization of Fe (hydr)oxides. These soils exhibited varying quantities of hematite, ferrihydrite and goethite, with distinct Al substitution levels and varied exposed crystallographic facets. Adsorption experiments revealed a positive correlation between Fe (hydr)oxide content and Cr(VI) fixation amount on colloid, which was influenced by the mineral types, Al substitution levels and facet exposures. Further, Cr(VI) was sequestered on soil by adsorption and reduction. In soils enriched with crystalline Fe (hydr)oxides, Cr(VI) reduction was primarily governed by SOM, while in soils enriched with poorly crystalline Fe (hydr)oxides, mineral-associated Fe(II) also contributed to Cr(VI) reduction. Aging experiments demonstrated that SOM and mineral-associated Fe(II) expedited Cr (VI) passivation and diminished the Cr leaching. These results improve our understanding of natural Fe (hydr)oxide structures and their impact on Cr(VI) behavior in soils, and shed light on complex soil-contaminant interactions and remediation of Cr(VI) polluted soils.

Responses of the Crown Shape of Larix kaempferi Plantations to Site Index in Subtropical Areas of China

This study addresses how site index may affect crown shape by developing a crown shape regression model for the planted L. kaempferi at high altitudes in the subtropical climate of China. A total of 9241 branches from 78 trees, including 39 dominant trees and 39 intermediate trees, were measured in Hubei Province, southern China. The branch characteristics, including branch length, branch angle, and branch chord length of all living branches, were measured by felling trees. The models that showed good performance in crown shape modeling were used and compared in the present study. The goodness of fit statistics and stability of parameter estimation of the modified Kozak equation were better than those of the segmented polynomial equation. A nonlinear mixed-effect crown shape model was developed based on the modified Kozak equation. In addition to the tree level variables of diameter at the breast height (DBH), crown ratio (CR), and tree height-to-DBH ratio, an attempt was made to incorporate the site index into the crown shape model for the planted L. kaempferi. However, the site index was not a significant variable in the crown shape model. The purpose of our study was to lay the foundation for further study of the growth of the trees and the effects of crown morphology on stem growth in the future.

Leaching of soil legacy nitrogen in intact soil columns and significance of soil macropore structure

Excessive application of chemical fertilizers accumulates nitrogen in soil (soil legacy nitrogen), and its release has a long-term impact on environmental quality. The information regarding leaching of soil legacy nitrogen and role of soil pore structure is scarce. Fifteen undisturbed soil cores with a depth of ~200 mm were collected from five paddy fields in a subtropical area of China, and soil pore structure was characterized with X-ray computed tomography. The batch leaching column experiments were conducted to investigate the nitrogen leaching from the soil cores. In the leachate, inorganic nitrogen (NO3−–N and NH4+–N) accounted for 73–85 % of total dissolved nitrogen (TDN), which showed small variations among the five sampling sites. The NO3−–N, NH4+–N and TDN concentrations in the leachate over the number of leaching times could be well fitted with the Gaussian, exponential or linear models, suggesting that different nitrogen forms showed variable leaching dynamics. NO3−–N and TDN leaching losses continued to increase with the number of leaching times, whereas NH4+–N leaching from the soil had a threshold value. Combination of changes in soil nitrogen content after leaching, the lagging effect of soil legacy nitrogen may be partly attributed to the continuous transformation of NH4+–N and organic nitrogen into NO3−–N in the soils. Besides the nitrogen content in the soil, the most important factor of soil pore structure controlling NO3−–N and TDN leaching loss was the fractal dimension; NH4+–N was mainly controlled by connectivity. The present study highlighted the importance of soil pore structure and nitrogen format transformation in the leaching of soil legacy nitrogen.

Genomic and phylogenetic profiling of RNA of tick-borne arboviruses in Hainan Island, China

Ticks act as vectors and hosts of numerous arboviruses. Examples of medically important arboviruses include the tick-borne encephalitis virus, Crimean Congo hemorrhagic fever, and severe fever with thrombocytopenia syndrome. Recently, some novel arboviruses have been identified in blood specimens of patients with unexplained fever and a history of tick bites in Inner Mongolia. Consequently, tick-borne viruses are a major focus of infectious disease research. However, the spectrum of tick-borne viruses in subtropical areas of China has yet to be sufficiently characterized. In this study, we collected 855 ticks from canine and bovine hosts in four locations in Hainan Province. The ticks were combined into 18 pools according to genus and location. Viral RNA-sequence libraries were subjected to transcriptome sequencing analysis. Molecular clues from metagenomic analyses were used to classify sequence reads into virus species, genera, or families. The diverse viral reads closely associated with mammals were assigned to 12 viral families and important tick-borne viruses, such as Jingmen, Beiji nairovirus, and Colorado tick fever. Our virome and phylogenetic analyses of the arbovirus strains provide basic data for preventing and controlling human infectious diseases caused by tick-borne viruses in the subtropical areas of China.

Effects on the Synthesis and Accumulation of Triterpenes in Leaves of Cyclocarya paliurus under MeJA Treatment

Cyclocarya paliurus (Batal.) lljinskaja, the sole and multi-functional tree species of the family Juglandaceae, grows extensively in subtropical areas of China. Species-specific triterpenoids in its leaves have validated health-promoting effects, including hypoglycemic and hypolipidemic activities. To illustrate the effect of MeJA treatment on the accumulation and biosynthesis of triterpenoids in C. paliurus leaves at different stages of maturity, the contents of total triterpenoids and six triterpene compounds, along with the relative expression of three key genes, were detected. The results showed that the contents of triterpenes and expression patterns of the genes significantly differed among the samples. Different treatment times also had diverse effects on triterpenoid accumulation and gene expression. MeJA treatment had positive effects on total triterpenoids, cyclocaric acid B, and cyclocarioside A/B, especially in young leaves. Gene expression was highest in young leaves after 10 days of treatment, indicating that they were the most sensitive to MeJA. This study provided a reference for improving the accumulation of triterpenoids in C. paliurus plantations in the future.

Hyphantria cunea (Drury) Showed a Stronger Oviposition Preference for Native Plants after Invading the Subtropical Region of China

Hyphantria cunea (Drury) (Lepidoptera: Erebidae) is an invasive alien species that is widely distributed in northern China. H. cunea now occurs for the first time in the subtropical areas of China. Despite the importance of identifying oviposition host plants to control the spread of H. cunea, it is not clear whether H. cunea has a new oviposition preference for plant hosts in the new habitat after invading the subtropical region. At the same time, whether the presence of new plant volatiles of new hosts in new habitats influences the oviposition host preference of H. cunea has not been studied. In this study, we investigated the oviposition host plant preferences of H. cunea in the subtropical region of China. In the presence of multiple potential host plants, we found, for the first time, that H. cunea preferred Carya illinoinensis, Morus alba, and Carya cathayensis for oviposition. Through the effects on plant volatiles and on the oviposition, ten volatile compounds with significant differences in relative abundance between five plants with different fitness levels were significantly correlated with the oviposition preference of females. Cis-Hex-3-en-1-ol, (E)-3-Hexen-1-ol, cis-3-Hexenyl acetate 1, and 3-Pentadiene,4-methyl, had a significant positive correlation with the adult oviposition preference. Our results provide an important research basis for the study of green prevention and control strategies of subtropical H. cunea in China.

A dataset of species composition and biomass in successional stages of Tiantong typical evergreen broad-leaved forest (2008–2017)

As a basic properties of forest vegetation, forest succession law is the basis understanding . Typical evergreen broad-leaved forest a zonal vegetation in the subtropical area of China. The existing vegetation is mostly in different secondary succession stages due to human and natural disturbance. lant species is an important indicator of the forest ecosystem and the basis for the study o structure, function and dynamics of evergreen broad-leaved forest. According to CNERN monitoring standards, Zhejiang Tiantong Forest Ecosystem Observation and Research Station three three succession plots and established a dataset species composition 2008 to 2017. The succession plots are evergreen shrub plot, Schima Superba forest plot and Castanopsis fargesii forest plot, respectively species name, abundance, mean diameter and biomass of woody plants the plots. The database provides critical data for the study and application of succession, community assembly and forest restoration in subtropical typical evergreen broad-leaved forests.

Two new Mycena (Mycenaceae, Agaricales) species with rhizomorphs from subtropical areas of China

Two new taxa are described from subtropical areas of China: Mycena chlorocyanea sp. nov. in sect. Viscipelles, and Mycena flosoides sp. nov. in sect. Polyadelphia. Photographs of basidiomata and morphological features, and relevant illustrations of these species are presented in this paper. Morphological characters were compared with related Mycena species, and phylogenetic analyses were conducted using internal transcribed spacer and the large subunit regions of nuclear ribosomal RNA gene sequences with Bayesian Inference and Maximum Likelihood. The phylogenetic trees showed that the two new taxa can be distinguished from phenotypically similar and phylogenetically related species.

Fossil Fruits of Ceratophyllum from the Upper Eocene and Miocene of South China.

Ceratophyllum L. is a cosmopolitan genus of perennial aquatic herbs that occur in quiet freshwaters. Fossils of this genus have been widely reported from the Northern Hemisphere, most of them occurring in the temperate zone. Here, we describe two species of fossil fruits discovered from subtropical areas of China. The fossil fruit discovered from the upper Eocene Huangniuling Formation of the Maoming Basin is designated as C. cf. muricatum Chamisso, and fruits discovered from the Miocene Erzitang Formation of the Guiping Basin are assigned to the extant species C. demersum L. The discovery of these two fossil species indicates that Ceratophyllum had spread to South China by the late Eocene and their distribution expanded in subtropical China during the Miocene.

The species richness pattern and its component dependence of two typical secondary forests in central China

Secondary forests dominated by Masson pine (Pinus massoniana, MPF) and Chinese fir (Cunninghamia lanceolata, CFF) are widespread in the subtropical areas of China, whereas their biodiversity patterns receive far less attention than biomass patterns. This study aimed to gain insights into the species richness (SR) patterns of the typical natural secondary MPF and CFF in central China, with the old-growth zonal vegetation (evergreen-deciduous broadleaved mixed forest, EDBMF) used as reference. We established 45 plots across the three forest types and surveyed all the stems with a diameter at breast height ≥ 1 cm in each plot. Specifically, we compared the local (plot-level) and rarefied SR among the three forest types; at the metacommunity level, we examined the dependence of the rarefied SR difference between MPF and CFF on the number of individuals (N), species abundance distribution (SAD), and conspecific spatial aggregation (CSA); and we also assessed how local SR changed with N and species dominance within MPF and CFF. Our results showed that MPF had local and rarefied SR levels higher than CFF and closer to EDBMF. Both N and SAD had positive contributions to the high rarefied SR level of MPF (relative to CFF), while CSA had negative contributions. The N contributions were significant and dominated at most scale, the SAD contributions were considerable and significant at large scales, and the CSA contributions were significant at small and intermediate scales. Moreover, within MPF and CFF, local SR changed with N more generally than with species dominance. In conclusion, at both local and metacommunity level, MPF was generally more species-rich than CFF, and this difference remarkably depended on N, suggesting that the habitat conditions of CFF may be stressful for species persistence. Our findings also have several implications for biodiversity research and ecosystem management.

Impacts of Moso bamboo (Phyllostachys pubescens) invasion on species diversity and aboveground biomass of secondary coniferous and broad-leaved mixed forest.

In recent decades, Moso bamboo has been largely increasing in the subtropical area of China, raising ecological concerns about its invasion into other native forest ecosystems. One concern is whether the invasion of Moso bamboo significantly simplifies forest community composition and structure and declines biomass. This study adopted the space-for-time method to investigate a secondary coniferous and broad-leaved mixed forest (SF) being invaded by an adjacent Moso bamboo forest (MB) in the Wuxie forest reserve, Zhejiang Province. Three plots were established in each SF, MB, and transitional forest. The results showed that the species composition and species dominance of the arborous layer changed significantly (P < 0.05), which was indicated by the significantly decreased species richness (Margalef index, Shannon–Wiener index, and Simpson index) and evenness (Pielou evenness index). In contrast, the species richness of the shrub and herbaceous layers had two divergent indications (increasing or unchanged), and the evenness remained unchanged. The total and arborous-layer aboveground biomass of the forest community has had no noticeable change (P < 0.05). However, the biomass of the shrub and herbaceous layers showed an increasing trend (shrub significant but herbaceous not), but they only occupied a small proportion (∼1%) of the total biomass. Finally, the aboveground biomass and the diversity index had no significant correlation in each layer and overall stands. We hope that the findings could provide a theoretical basis for the invasion mechanism and ecological consequences of the Moso bamboo invasion.

Mycena subpiligera sp. nov., a Symbiotic Species from China Associated with the Seed Germination of Gastrodia elata

Mycena subpiligera, a new taxon in sect. Fragilipedes that can strongly enhance the germination efficiency of Gastrodia elata seeds, was discovered in subtropical areas of China. As revealed by a morphological comparison with related Mycena species as well as maximum likelihood (ML) and Bayesian phylogenetic analyses based on sequences of the internal transcribed spacer (ITS) and the large subunit (LSU) regions of nuclear ribosomal RNA, the new taxon can be distinguished from phenotypically similar and phylogenetically related species. Optimal cultural conditions for M. subpiligera basidiomata are reported, and the germination rate of the new species is compared with that of M. citrinomarginata.

The complete chloroplast genomes of Tetrastigma hemsleyanum (Vitaceae) from different regions of China: molecular structure, comparative analysis and development of DNA barcodes for its geographical origin discrimination

BackgroundTetrastigma hemsleyanum is a valuable traditional Chinese medicinal plant widely distributed in the subtropical areas of China. It belongs to the Cayratieae tribe, family Vitaceae, and exhibited significant anti-tumor and anti-inflammatory activities. However, obvious differences were observed on the quality of T. hemsleyanum root from different regions, requiring the discrimination strategy for the geographical origins.ResultThis study characterized five complete chloroplast (cp) genomes of T. hemsleynum samples from different regions, and conducted a comparative analysis with other representing species from family Vitaceae to reveal the structural variations, informative markers and phylogenetic relationships. The sequenced cp genomes of T. hemsleyanum exhibited a conserved quadripartite structure with full length ranging from 160,124 bp of Jiangxi Province to 160,618 bp of Zhejiang Province. We identified 112 unique genes (80 protein-coding, 28 tRNA and 4 rRNA genes) in the cp genomes of T. hemsleyanum with highly similar gene order, content and structure. The IR contraction/expansion events occurred on the junctions of ycf1, rps19 and rpl2 genes with different degrees, causing the differences of genome sizes in T. hemsleyanum and Vitaceae plants. The number of SSR markers discovered in T. hemsleyanum was 56–57, exhibiting multiple differences among the five geographic groups. Phylogenetic analysis based on conserved cp genome proteins strongly grouped the five T. hemsleyanum species into one clade, showing a sister relationship with T. planicaule. Comparative analysis of the cp genomes from T. hemsleyanum and Vitaceae revealed five highly variable spacers, including 4 intergenic regions and one protein-coding gene (ycf1). Furthermore, five mutational hotspots were observed among T. hemsleyanum cp genomes from different regions, providing data for designing DNA barcodes trnL and trnN. The combination of molecular markers of trnL and trnN clustered the T. hemsleyanum samples from different regions into four groups, thus successfully separating specimens of Sichuan and Zhejiang from other areas.ConclusionOur study obtained the chloroplast genomes of T. hemsleyanum from different regions, and provided a potential molecular tracing tool for determining the geographical origins of T. hemsleyanum, as well as important insights into the molecular identification approach and and phylogeny in Tetrastigma genus and Vitaceae family.

Association Analysis Between Genotype and Environment: Differentiation Between Cyclocarya paliurus Resources That Accumulate Triterpenoids.

Cyclocarya paliurus is mainly distributed in subtropical areas of China. Its leaves are rich in beneficial triterpenoids that have bioactivities against human diseases, including hyperlipemia, diabetes, and hypertension. In this study, data on the genetic diversity, distributing environment, and triterpenoids of C. paliurus samples were collected from a wide area in China. The data covered 316 C. paliurus germplasms collected from 26 distinct populations. Association analysis between genotype and triterpenoids was carried out to describe triterpenoids accumulation pattern. Based on our analyses, we identified the important trend that genotypes with higher triterpenoid contents belonged to a unique genotype subgroup. The results showed that pterocaryoside B and pterocaryoside A significantly vary among the genotypic subgroups. In addition, the different genotypic subgroups showed distinct geographical distributing areas. These findings provide information about the relationship between genetic and environmental factors and how this affects triterpenoids accumulation. This information will be valuable for targeted breeding and for further germplasm selection of C. paliurus resources.

Non-growing season drought legacy effects on vegetation growth in southwestern China

Water availability influences terrestrial ecosystems' composition, structure, and function. Recently, climate change increased drought periods frequency and length in many parts of the world, including southwestern China, a biodiversity hotspot. Although the drought impacts on ecosystems are well known, studies are scarce in subtropical areas of China. This work studied the drought legacy effects on vegetation growth in southwestern China using Normalized Difference Vegetation Index (NDVI) and the Standardized Precipitation Evapotranspiration Index (SPEI), with a particular focus on non-growing season extreme drought events. Pervasive non-growing season drought legacy effects were found in the first growing season in most parts of southwestern China. The highest impacts were identified in forests, while the effects in grass were less severe. At the regional scale, horizontal and vertical spatial patterns of drought legacy effects were heterogeneous, and the highest impacts were found in warmer and wetter forests and alpine grasslands. Our study highlights that severe drought conditions may dramatically affect vegetation growth in southwestern China.

Stand carbon storage and net primary production in China’s subtropical secondary forests are predicted to increase by 2060

BackgroundForest ecosystems play an important role in carbon sequestration, climate change mitigation, and achieving China's target to become carbon (C) neutral by 2060. However, changes in C storage and net primary production (NPP) in natural secondary forests stemming from tree growth and future climate change have not yet been investigated in subtropical areas in China. Here, we used data from 290 inventory plots in four secondary forests [evergreen broad-leaved forest (EBF), deciduous and evergreen broad-leaved mixed forest (DEF), deciduous broad-leaved forest (DBF), and coniferous and broad-leaved mixed forest (CDF)] at different restoration stages and run a hybrid model (TRIPLEX 1.6) to predict changes in stand carbon storage and NPP under two future climate change scenarios (RCP4.5 and RCP8.5).ResultsThe runs of the hybrid model calibrated and validated by using the data from the inventory plots suggest significant increase in the carbon storage by 2060 under the current climate conditions, and even higher increase under the RCP4.5 and RCP8.5 climate change scenarios. In contrast to the carbon storage, the simulated EBF and DEF NPP declines slightly over the period from 2014 to 2060.ConclusionsThe obtained results lead to conclusion that proper management of China’s subtropical secondary forests could be considered as one of the steps towards achieving China’s target to become carbon neutral by 2060.

Complete genome sequence of biocontrol strain Paenibacillus peoriae HJ-2 and further analysis of its biocontrol mechanism

BackgroundParis polyphylla is a herb widely used in traditional Chinese medicine to treat various diseases. Stem rot diseases seriously affected the yield of P. polyphylla in subtropical areas of China. Therefore, cost-effective, chemical-free, eco-friendly strategies to control stem rot on P. polyphylla are valuable and urgently needed.ResultsIn this paper, we reported the biocontrol efficiency of Paenibacillus peoriae HJ-2 and its complete genome sequence. Strain HJ-2 could serve as a potential biocontrol agent against stem rot on P. polyphylla in the greenhouse and field. The genome of HJ-2 consists of a single 6,001,192 bp chromosome with an average GC content of 45% and 5,237 predicted protein coding genes, 39 rRNAs and 108 tRNAs. The phylogenetic tree indicated that HJ-2 is most closely related to P. peoriae IBSD35. Functional analysis of genome revealed numerous genes/gene clusters involved in plant colonization, biofilm formation, plant growth promotion, antibiotic and resistance inducers synthesis. Moreover, metabolic pathways that potentially contribute to biocontrol mechanisms were identified.ConclusionsThis study revealed that P. peoriae HJ-2 could serve as a potential BCA against stem rot on P. polyphylla. Based on genome analysis, the genome of HJ-2 contains more than 70 genes and 12 putative gene clusters related to secondary metabolites, which have previously been described as being involved in chemotaxis motility, biofilm formation, growth promotion, antifungal activity and resistance inducers biosynthesis. Compared with other strains, variation in the genes/gene clusters may lead to different antimicrobial spectra and biocontrol efficacies.