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Arbuscular mycorrhizal fungi (AMF) form a near-ubiquitous mutualistic association with roots to help plants withstand harsh environments, and play a key role in the establishment of coastal beach plant communities. Yet little is known about the structure and composition of AMF communities on coastal beaches of eastern China. In this study, we investigated the occurrence, community composition and diversity of AMF associated with common wild plants on a coastal beach of North Jiangsu, China. Almost all of the local wild species were colonized by AMF except for Chenopodium album L. Thirty-seven AMF species were isolated from the rhizosphere belonging to 12 genera in seven families. Glomus was the dominant genus and Funneliformis mosseae the dominant species. The colonization, spore composition and diversity of AMF were strongly related to edaphic factors. Sodium (Na+) ions in the soil significantly and negatively affected the colonization rate by AMF and both soil Na+ levels and pH had a significant negative effect on AMF spore density and evenness. However, there was a significant positive correlation between species richness and total organic carbon. The results provide insights into soil factors affecting native AMF communities in coastal beach habitats which could benefit vegetation recovery and soil reclamation efforts.

Mangrove and salt marsh ecosystems are one of the most productive ecosystems in terrestrial ecosystems, playing an important role in global carbon (C) cycling. The anaerobic condition in coastal wetland usually impedes the decomposition of soil organic carbon (SOC). However, the intrinsic stabilization mechanisms of SOC other than environmental factors are poorly understood in coastal wetland. In this paper, we investigated the relative contribution of mineral association and chemical compounds in maintaining the stabilization of SOC in the mangrove/salt marsh ecotone, and how the microbial community is involved in the stabilization. From NMR spectroscopy, we found that the SOC molecular structure of Spartina. alterniflora soils is simpler than that in mangrove forest, indicating an increased SOC decomposition with invasion of S. alterniflora. On the contrary, the molecular structure of SOC in mangrove forest was dominated by recalcitrant aromatic C. Meanwhile, the larger fractions of silt/clay content in S. alterniflora and the transitional community were corresponding to higher percentage of mineral organic carbon (MOC), which suggest that the SOC in S. alterniflora vegetated soil was mainly protected by the mineral association. The transitional community contained highest MOC content probably due to both physical protection of mineral association and recalcitrant C input from adjacent mangroves. We also found that the fraction of SOC and its chemical structure of functional groups were associated with microbial communities. This study revealed the occurrence of different SOC stabilization mechanisms between mangroves and salt marshes. The knowledge gained may help to make predictions about future SOC dynamics as the different stabilization processes may response to climate change or human activities differently.

Forest conversion may affect the soil microbial community through impacts on soil properties. However, our understanding of the effects on the soil bacterial community remains limited. The objective of this study was to understand the impacts of forest conversion of native broad-leaved species on soil bacterial structure and diversity. The phylogeny structure and diversity of the soil bacterial communities were compared among four forest types. We found that the soil total nitrogen (TN) and C:N ratios were significantly different between a mixed forest and other forest types. The native forest and mixed forest contained a higher relative abundance of Actinobacteria, Gammaproteobacteria, and Acidimicrobiia compared with the Chinese fir and Bamboo forests, but more unique operational taxonomic units (OTUs) were found in the Chinese fir and Bamboo forests. Soil bacteria in bamboo forest and Chinese fir forest showing a higher diversity but a lower total sequencing number than native forest and mixed forest. Among the soil properties, pH was an important variable that contributing to both soil bacterial communities and soil alpha diversities. Our work suggests that after a long-tern forest conversion, both land-use history and vegetation species strongly influence soil bacteria communities, and soil pH is a main factor that influences soil bacterial structure.

Dendrobium is an important medicinal material in China. It has the effect of nourishing the stomach, nourishing yin and clearing heat. In China, there are many types of Dendrobium, and different Dendrobium species have different efficacy. The present study is aimed at distinguishing three major Dendrobium species from morphological and microscopic identification in Ta-pieh mountains area. In this article, the roots, stems and leaves of Dendrobium huoshanense, Dendrobium officinale, and Dendrobium moniliforme are used as materials to compare the differences of tissues of these three Dendrobium species by morphological indexes and microscopic identification of different Dendrobium. The stem morphology of these three Dendrobium species was significantly different except for stem internodes number and the middle part of the stem diameter by measuring the stems of Dendrobium. To ensure the safe use of Dendrobium, we built a fast and convenient method combining normal and fluorescence microscopy was applied in the present study to distinguish D. huoshanense, D. officinale, and D. moniliforme. The microscopic results show that different types of Dendrobium exhibit different states that can be distinguished under normal light normal and fluorescence microscopy. This comparative study of morphology and microscopy contributes to the development of identification and quality evaluation of Dendrobium.

Enzymatic saccharification of corn stover can be enhanced by partially replacing commercial enzymes with bacterial crude enzyme extracts. Three bacteria, Bacillus sp. A0, Bacillus sp. CH20S1, and Exiguobacterium sp. AS2B, were cultured in a media with corn stover as the substrate. The cultural conditions were monitored and optimized to maximize CMCase and xylanase activity in the crude enzyme extracts. After 72 h of hydrolysis of corn stover with diluted crude enzymes (DCE) from the three strains, reducing sugars were released from non-pretreated and pretreated corn stovers. Values of the released sugars ranged from 48.23–71.69 mg g− 1, which were lower than those released by commercial cellulase (100–400 mg g− 1). The synergistic effects were observed when 12 FPU g− 1 and 4 FPU g− 1 of commercial cellulase were added to the DCE of the CH20S1 strain producing 315.90 mg g− 1 and 320.65 mg g− 1 reducing sugars, respectively. It was shown that an effective combination of bacterial DCE with commercial enzymes could achieve more cost-efficient saccharification of lignocellulosic biomass compared to either of the two enzymes used alone.

Pine wilt disease is a devastating forest disease caused by the pinewood nematode Bursaphelenchus xylophilus, which has been listed as the object of quarantine in China. Climate change influences species and may exacerbate the risk of forest diseases, such as the pine wilt disease. The maximum entropy (MaxEnt) model was used in this study to identify the current and potential distribution and habitat suitability of three pine species and B. xylophilus in China. Further, the potential distribution was modeled using the current (1970–2000) and the projected (2050 and 2070) climate data based on two representative concentration pathways (RCP 2.6 and RCP 8.5), and fairly robust prediction results were obtained. Our model identified that the area south of the Yangtze River in China was the most severely affected place by pine wilt disease, and the eastern foothills of the Tibetan Plateau acted as a geographical barrier to pest distribution. Bioclimatic variables related to temperature influenced pine trees’ distribution, while those related to precipitation affected B. xylophilus’s distribution. In the future, the suitable area of B. xylophilus will continue to increase; the shifts in the center of gravity of the suitable habitats of the three pine species and B. xylophilus will be different under climate change. The area ideal for pine trees will migrate slightly northward under RCP 8.5. The pine species will continue to face B. xylophilus threat in 2050 and 2070 under the two distinct climate change scenarios. Therefore, we should plan appropriate measures to prevent its expansion. Predicting the distribution of pine species and the impact of climate change on forest diseases is critical for controlling the pests according to local conditions. Thus, the MaxEnt model proposed in this study can be potentially used to forecast the species distribution and disease risks and provide guidance for the timely prevention and management of B. xylophilus.

Rainfall is an indispensable link in the atmospheric water cycle, which plays a critical role in forest hydrology. Quercus acutissima and Cunninghamia lanceolata are two fast-growing and economically important tree species in the middle and lower reaches of the Yangtze River. They are extensively applied in the restoration of vegetation, hydraulic engineering, and the development of artificial forests. The primary aims of this study were to describe and compare the changes in soil water content following rainfall events, while elucidating their relationships to environmental factors. From September 2012 to August 2013, we monitored the soil moisture at different depths every 30 min using commercially available soil moisture measuring devices. Hourly meteorological data were monitored over an open area at 200 m from the sample site, including photosynthetically active radiation (Par), air temperature (Ta), relative air humidity (RH), vapor pressure deficits (Vpd), rainfall, and wind speed. The results revealed that variations in the soil moisture content during summer (Cv = 0.231) and autumn (Cv = 0.0.170) were greater than during spring (Cv = 0.0.092) and winter (Cv = 0.0.055), with those in the deep soil moisture (Cv = 0.117) being smaller. The soil moisture content was significantly altered following the cessation of rainfall, where the initial and average moisture content, and the ACR of the soil increased with higher rainfall intensities. The ACR was positively correlated with Ta (γ = 0.16), RH (γ = 0.46) and rainfall (γ = 0.22), but negatively correlated with Par (γ = −0.29), Vpd (γ = −0.23), and wind speed (γ = −0.01). This study provides valuable information regarding the hydrological processes of artificial forests in the middle and lower reaches of the Yangtze River.

Anthropogenic overexploitation poses significant threats to the ecosystems that surround mining sites, which also have tremendous negative impacts on human health and society safety. The technological capacity of the ecological restoration of mine sites is imminent, however, it remains a challenge to sustain the green restorative effects of ecological reconstruction. As a promising and environmentally friendly method, the use of microbial technologies to improve existing ecological restoration strategies have shown to be effective. Nonetheless, research into the mechanisms and influences of rock-solubilizing microbial inoculums on plant growth is negligible and the lack of this knowledge inhibits the broader application of this technology. We compared the effects of rock-solubilizing microbial inoculums on two plant species. The results revealed that rock-solubilizing microbial inoculums significantly increased the number of nodules and the total nodule volume of Robinia pseudoacacia L. but not of Lespedeza bicolor Turcz. The reason of the opposite reactions is possibly because the growth of R. pseudoacacia was significantly correlated with nodule formation, whereas L. bicolor’s growth index was more closely related to soil characteristics and if soil nitrogen content was sufficient to support its growth. Further, we found that soil sucrase activity contributed the most to the height of R. pseudoacacia, and the total volume of root nodules contributed most to its ground diameter and leaf area. Differently, we found a high contribution of total soil carbon to seedling height and ground diameter of L. bicolor, and the soil phosphatase activity contributed the most to the L. bicolor’ s leaf area. Our work suggests that the addition of rock-solubilizing microbial inoculums can enhance the supply capacity of soil nutrients and the ability of plants to take up nutrients for the promotion of plant growth. Altogether, our study provides technical support for the practical application of rock-solubilizing microbes on bare rock in the future.

To protect endangered species and restore their habitats, it is important to be able to predict their potential geographic distributions. The Dendrobium plant is important in traditional Chinese medicine, but urban expansion and over-exploitation have led to a decrease of Dendrobium resources. To achieve sustainable development of Dendrobium resources, the spatial and temporal distribution of two Dendrobium species were systematically analyzed based on the distribution points of D. moniliforme (104) and D. nobile (87). Maximum entropy modeling (MaxEnt) was used to predict the distribution of suitable habitats for these Dendrobium species, both currently and in the future, under different representative concentration pathways (RCPs). Three RCPs included RCP2.6, RCP4.5, and RCP8.5. The results show that D. moniliforme and D. nobile are widely distributed in the south of China (Anhui, Guangdong, Jiangxi, and Hunan provinces). Worldwide, Japan and North Korea were identified as major distribution areas for D. moniliforme and D. nobile. Based on the MaxEnt model, the mean diurnal range and the minimum temperature of the coldest month were identified as the most significant bioclimatic variables controlling the distribution of D. moniliforme and D. nobile. Future climate change will likely result in an increase of suitable habitat areas for D. moniliforme (by around 16%), and a decrease for D. nobile (by around 1–10%), but climate change is unlikely to have much impact on the distribution of suitable habitats for D. moniliforme and D. nobile in Japan and North Korea. Based on our findings, measures should be taken to protect these precious medicinal plant resources, and the sites used for the artificial cultivation of Dendrobium will need to shift as the climate changes.

There are a large number of abandoned mining areas in China, where external-soil spray seeding is a common technique used to assist with the restoration of these areas. However, the soil component of external-soil spray seeding is deficient, and they are prone to collapse, which complicates ecological restoration. In this study, we added a mineral-solubilizing microbial strain to an external-soil spray seeding substrate in Robinia pseudoacacia and Lespedeza bicolor pots, which were monitored from December 2018 to November 2019. We investigated their root growth and root tensile properties, as well as root-reinforced soil shear strength. The results revealed that the addition of the microbial strain in the substrate improved root growth of Robinia pseudoacacia. The root-reinforced soil shear strength, tensile force and strength were also strengthened by the added microbial strain. Although the growth rate of Robinia pseudoacacia was faster than that of Lespedeza bicolor, the shear strength of the root-reinforced Robinia pseudoacacia soil was lower than that of the Lespedeza bicolor root-reinforced soil of the same diameter. Finally, compared with the cohesion, the change in the friction angle is relatively small, and differences in cohesion resulted in shear strength changes under the same treatment. Our results suggested that the addition of a mineral-solubilizing microbial strain to the external-soil spray seeding substrate could help plants strengthen the soil and positively enhance its effects. These results might also enrich the existing data on the effects of mineral-solubilizing microbial strains on plant roots, while guiding further studies toward improving the efficacy of external-soil spray seeding technologies.

Background Dendrobium huoshanense C.Z. Tang et S.J. Cheng is a traditional Chinese herbal medicine with high medicinal value in China. Polysaccharides and alkaloids are its main active ingredients. To understand the difference of main active ingredients in different tissues, we determined the contents of polysaccharides and alkaloids in the roots, stems and leaves of D. huoshanense. In order to explore the reasons for the differences of active ingredients at the level of transcription, we selected roots, stems and leaves of D. huoshanenese for transcriptome sequencing and pathway mining. Results The contents of polysaccharides and alkaloids of D. huoshanense were determined and it was found that there were significant differences in different tissues. A total of 716,634,006 clean reads were obtained and 478,361 unigenes were assembled by the Illumina platform sequencing. We identified 1407 carbohydrate-active related unigenes against CAZy database including 447 glycosyltransferase genes (GTs), 818 glycoside hydrolases (GHs), 60 carbohydrate esterases (CEs), 62 carbohydrate-binding modules (CBMs), and 20 polysaccharide lyases (PLs). In the glycosyltransferases (GTs) family, 315 differential expression genes (DEGs) were identified. In total, 124 and 58 DEGs were associated with the biosynthesis of alkaloids in Dh_L vs. Dh_S and Dh_R vs. Dh_L, respectively. A total of 62 DEGs associated with the terpenoid pathway were identified between Dh_R and Dh_S. Five key enzyme genes involved in the terpenoids pathway were identified, and their expression patterns in different tissues was validated using quantitative real-time PCR. Conclusions In summary, our study presents a transcriptome profile of D. huoshanense. These data contribute to our deeper relevant researches on active ingredients and provide useful insights into the molecular mechanisms regulating polysaccharides and alkaloids in Dendrobium. Electronic supplementary material The online version of this article (10.1186/s12864-018-5305-6) contains supplementary material, which is available to authorized users.

The brassinosteroids (BRs) constitute a recently defined class of plant hormone that can enhance the resistance of plants to multiple stresses. However, the effects of BRs on salt-stressed woody plants, notably on photosynthesis and chloroplast ultrastructure, have received little attention. Black locust (Robinia pseudoacacia L.) seeds and seedlings were pretreated with 1.04 µmol L− 1 24-epibrassinolide (24-epiBL) by soaking and root dipping, respectively, and grown under non-saline or saline conditions (0, 100, 200 mmol L− 1 NaCl). Salinity stress decreased photosynthesis, chlorophyll concentration, transpiration, and stomatal conductance but also decreased the water-use efficiency, while chlorophyll fluorescence indicated a decrease in photochemical quenching and in maximum potential quantum efficiency. Indicators of oxidative stress (for example, H2O2 and antioxidant enzymes), membrane leakage, and amounts of Na+ ions in leaves and chloroplasts were increased and, at the highest stress, chloroplast ultrastructure was severely disrupted. Exogenous 24-epiBL improved membrane stability and reduced foliar Na+ levels, while substantially alleviating stress-induced changes in photosynthetic gas exchange. Improvements in chlorophyll content and indicators of oxidative stress were not as large but were still highly significant. Thylakoid membrane structure was protected. Both methods of applying 24-epiBL were effective, but root-dipped seedlings performed marginally better. The results suggest that treatment of black locust seedlings with 24-epiBL prior to planting may improve performance and aid establishment on salt-affected soils.

Drought is one of the most critical limiting environmental factors for plant survival and restoration in areas of rocky desertification in southwestern China. Here, we aimed to understand how arbuscular mycorrhizal fungi (AMF) affect the growth and drought tolerance of tree species used for afforestation, with the ultimate aim of using them to restore degraded karst ecosystems. A pot experiment was conducted in which Zenia insignis seedlings were inoculated separately with three AMF (Funneliformis mosseae, Rhizoglomus intraradices, and Diversispora versiformis) and a mixture of all three species under two water regimes (drought stress and normal water) in a greenhouse. The results showed that AMF have a positive effect on plant biomass, osmolytes, and antioxidant enzyme activity under drought conditions. Shoot/root biomass increased by 12.5–33.8% and plant height increased by 13.6–32.1% after inoculation with AMF under drought conditions. The phosphorus content of the shoots significantly increased in mycorrhized plants, whereas nitrogen content was minimally affected. Superoxide dismutase and catalase activity was higher under drought stress in mycorrhized plants than in non-mycorrhized plants. The same pattern was found for soluble sugar and proline content in mycorrhized seedings under water deficit conditions. Mixed AMF inoculation had a more beneficial effect on plant growth than single AMF inoculation. In conclusion, our results indicate that AMF inoculation could help restore degraded ecosystems in desertified karst regions.

To find a multifunctional lignocellulolytic enzyme-producing strain, ten bacterial isolates from paper mill wastewater were tested for their carboxymethyl cellulose (CMC) hydrolytic ability. Bacillus sp. TPF-1, which exhibits the highest hydrolytic ability, was selected to produce lignocellulolytic enzymes using various biomass types as carbon sources. The highest CMCase (9.12 U/mL) and xylanase (102.55 U/mL) activities were obtained by green algae, and the maximum laccase activity (7037.28 U/L) was induced by Sargassum fusiforme. CMCase and xylanase showed the highest activities at 55 and 50 °C, respectively, with the same optimum pH of 5.4. The laccase exhibited optimum temperature of 40 °C and retained 60% more activity at 80 °C in extreme acid conditions (pH 2.2). To explore the multiple applications of these enzymes, crude enzymes induced by green algae were used to saccharify untreated algae. The reducing sugar produced by crude enzymes and commercial cellulase was 23 and 14% higher than that of the control, respectively, and it was 48% higher using crude enzymes with commercial cellulase (72 h). Additionally, the laccase induced by S. fusiforme was tested to decolorize two chemical dyes under an acidic condition (pH 2.2). The highest decolorization rates were 56.13 and 62.14% for Coomassie brilliant blue R-250 and Congo Red, respectively, in the presence of hydroxybenzotriazole monohydrate.

Labile fractions of soil carbon pools are sensitive to environmental changes, which would influence the stabilization of soil carbon. However, it is unclear whether the dynamics of labile organic carbon (LOC) and soil organic carbon (SOC) are coupled and how they influence each other in coastal wetland. The present work investigated the trends of soil carbon fractions among mangrove and Spartina alterniflora communities with different stand ages (1, 5, 10, and 15 years), at Quanzhou Bay Estuary Wetland Nature Reserve, China. We found that SOC in a mangrove ecosystem increased over time, while there was no significant trend in S. alterniflora dominated ecosystems. The highest LOC of mangrove appeared in 5-year-old communities, and then decreased with stand age. In S. alterniflora communities, content of labile fractions increased with the stand age. These trends indicated different soil carbon dynamics when comparing mangrove and S. alterniflora ecosystems. The development of mangroves promoted accumulation of recalcitrant carbon, while S. alterniflora ecosystems contributed to an increase of labile carbon. This phenomenon is probably caused by the characteristics of vegetation and the hydrological conditions. Mangroves contribute more refractory organic carbon to the soil carbon pool, while accumulation of LOC in S. alterniflora communities may inhibit the stabilization of SOC. Our study on the relationship of LOC and SOC implies that complex interactions occur among soil carbon pools and environmental conditions in coastal wetlands, suggesting soil carbon models should take into account decoupled dynamics of LOC and SOC.

In this study, we investigated the effect of forest types changes (from coniferous and broadleaf mixed forest (CBMF) to plantation forests of bamboo (Phyllostachys pubescens forest, MBF) and hickory (Carya cathayensis forest, CHF)) combined with intensive management on soil organic carbon (SOC) and microbial community structure, using the 13C-nuclear magnetic resonance (NMR) and phospholipid fatty acid (PLFA). The results indicated that soil organic carbon significantly decreased by 30.7 and 28.5% in MBF and CHF, respectively. The aromatic C and aromaticity also significantly decreased in MBF and CHF (P 0.05). Significant changes of the soil microbial community were found after the forest type changed from CBMF to MBF and CHF. Total soil microbial PLFAs, soil bacteria PLFAs, fungus PLFAs, actinobacteria PLFAs, arbuscular mycorrhizal fungi PLFAs and protozoan PLFAs ranked as follows: CBMF > CHF > MBF (P CHF (0.66) > CBMF (0.49) (P CHF > MBF, P

Carbonate minerals are extensively distributed across China, and their special rock structures make them vulnerable to land damage through mining, leading to rocky desertification. Soil microorganisms play an important role in mineral weathering. However, little is known about the utilization of the mineral-weathering microorganisms to alleviate the problem of rocky desertification in mines. In the present study, the mineral-solubilizing bacterium NL-11 was isolated from soil around weathered dolostones and identified as Bacillus thuringiensis (B. thuringiensis) based on the Biolog identification system and 16S rDNA sequence analysis. The mineral dissolution experiments revealed that inoculation with the live bacterium significantly increased the mineral sample dissolution via significantly enhancing Ca and Mg release, with increase values of 303.27 and 50.55 mg·L-1, respectively, compared to that with the inactivated bacterium. Moreover, the acetic acid secreted by strain NL-11 markedly decreased the size of particle diameter (quantified with a laser diffraction particle size analyser) through reducing pH value. The eroded traces were observed by scanning electron microscopy (SEM) analysis, and the results further verified the erosional effects of this strain. In addition, this bacterium contributed to the establishment and proliferation of plants by providing nutrient elements, such as phosphorus (P) and potassium (K). Our study not only provided an efficient bacterial strain NL-11, but also enriched the technologies to mitigate problems associated with ecological restorations of carbonate mines.

Background Dendrobium moniliforme (Linnaeus) Swartz is a well-known plant used in traditional Chinese medicine due to bioactive constituents. Polysaccharides are the main medicinal ingredients, yet no studies have been published on polysaccharide biosynthesis in D. moniliforme. To comprehensively investigate the polysaccharide at the transcription level, we performed de novo transcriptome sequencing for the first time to produce a comprehensive transcriptome of D. moniliforme. Results In our study, a database of 562,580 unigenes (average length = 1115.67 bases) was generated by performing transcriptome sequencing. Based on the gene annotation of the transcriptome, we identified 1204 carbohydrate-active related unigenes against CAZy database, including 417 glycosyltransferase genes (GTs), 780 glycoside hydrolases (GHs), 19 carbohydrate esterases (CEs), 75 carbohydrate-binding modules (CBMs), and 44 polysaccharide lyases (PLs). In the cellulose synthase family, 21 differential expression genes (DEGs) related to polysaccharide were identified. Subsequently, the tissue-specific expression patterns of the genes involved in polysaccharide pathway were investigated, which provide understanding of the biosynthesis and regulation of DMP at the molecular level. The two key enzyme genes (Susy and SPS) involved in the polysaccharide pathway were identified, and their expression patterns in different tissues were further analyzed using quantitative real-time PCR. Conclusions We determined the content of polysaccharides from Dendrobium moniliforme under different tissues, and we obtained a large number of differential genes by transcriptome sequencing. This database provides a pool of candidate genes involved in biosynthesis of polysaccharides in D. moniliforme. Furthermore, the comprehensive analysis and characterization of the significant pathways are expected to give a better insight regarding the diversity of chemical composition, synthetic characteristics, and the regulatory mechanism which operate in this medical herb.

The Chinese honey locust tree Gleditsia sinensis Lam. (Fabaceae) is a precious ecological and economic tree species that has wide-ranging usage. However, knowledge regarding seedling cultivation (especially the use of arbuscular mycorrhizal fungi (AMF)) is scarce, which limits the developent of Gleditsia plantations. A pot experiment was carried out under greenhouse conditions to estimate the effects of three AMF strains (Funneliformis mosseae 1, Funneliformis mosseae 2, and Diversispora tortuosa) on the growth, photosynthetic rate, and nutrient content of G. sinensis seedlings. Results showed that the growth parameters (seedling height, basal diameter, dry biomass) of the seedlings were significantly increased by each of the three AMF strains, associated with high root colonization rates (greater than 75%). Chlorophyll concentrations and photosynthetic rates were also increased by AMF, and phosphorus (P), and potassium (K) content in the three organs (leaf, stem, and root), and nitrogen (N) content in the leaf and stem of arbuscular mycorrhizal (AM) seedlings were significantly higher than in non-AM seedlings. Mycorrhizal dependency of the AM seedlings was greater than 350%, and significantly correlated with the increased P and K content in all three organs and increased N content in the leaf and stem. Positive effects of F. mosseae on growth and the nutrient content of seedlings were higher than those of D. tortuosa, but no significant different effects on G. sinensis seedlings were observed between the two strains of F. mosseae. Hence, growth of G. sinensis seedlings was effectively enhanced by AMF, with F. mosseae being more suitable for the inoculation of G. sinensis seedlings. These results indicate that arbuscular mycorrhization is beneficial for the growth of young G. sinensis plants. Further research is needed to determine whether the effects can be reproduced in a forest situation.

Arbuscular mycorrhizal fungi (AMF) play an important role in the establishment and maintenance of plant communities in forest ecosystems. Most previous studies about AMF have been conducted in natural forests, and little attention has been paid to trees in planted forests. This study investigated AMF associated with tree species and the relationships between edaphic factors and AMF communities in a planted forest of eastern China. We found high total AMF colonization rates in the roots of Carya illinoensis (Wangenh.) K. Koch, Zelkova serrata (Thunb.) Makinoz, Taxodium &lsquo, zhongshansha&rsquo, Eucommia ulmoides Oliv., and Elaeagnus pungens Thunb., ranging from 62.07% to 100%, indicating that AMF can establish effective symbiotic relationships with these tree species. The AMF colonization rate was significantly and negatively correlated with soil phosphorus, while AMF colonization intensity was significantly and negatively correlated with soil moisture content, total carbon, and organic matter content. Spore density was in the range of 4.38 to 76.38 spores per g soil. In total, 35 AMF species from 10 genera were identified. Glomus and Acaulospora were the dominant genera. Acaulospora foveata and Septoglomus constrictum were the dominant species. AMF communities differed among the tree species and were closely related to edaphic factors, and AMF diversity was significantly related to soil carbon and pH. Our results revealed the colonization, community, and diversity of AMF associated with tree species, as well as their relationships with edaphic factors, in planted forests. Our findings can be used to provide insight on the utilization and management of AMF to maintain sustainable management of planted forests.

Dendrobium, an important medicinal plant, is a source of widely used herbal medicine to nourish the stomach and treat throat inflammation. The present study is aimed at distinguishing and evaluating three major Dendrobium species by comparing physiochemical characteristics and understanding differences between different growth years in the Ta-pieh Mountains. Polysaccharides and total alkaloids of Dendrobium were determined, and the amino acids and trace elements were determined by UPLC (Ultra High-Performance Liquid Chromatography) and ICP-MS (Inductively coupled plasma mass spectrometry). It can be seen from the results that the polysaccharide content of these three kinds of Dendrobium in different growth years ranges from 249.31 mg·g-1 to 547.66 mg·g-1, and the highest content is in the 3-year-old Dendrobium huoshanense. The total alkaloid content ranges from 0.21 mg·g-1 to 0.54 mg·g-1, and the highest content is also the 3-year-old Dendrobium huoshanense. We determined the amino acid content of these three Dendrobium in different growth years, and we can see that each of the three kinds of Dendrobium contain seven kinds of amino acids required by the human body. We conducted a safety evaluation of the essential trace elements of Dendrobium, and the results showed that the dosage of 12g·d-1 Dendrobium prescribed in China Pharmacopoeia is in accordance with the recommended daily intake of trace elements recommended by the Food and Drug Administration of the United States, and will not cause trace element poisoning. Linear discriminant analysis was carried out on the basis of amino acids and trace elements and confirmed the applicability of multi-elemental analysis for identifying different Dendrobium species.

The harm of acid rain (AR) to plants foliage is mainly manifested by changing their physiological and biochemical processes, such as chlorosis, nutrient loss, enzyme activity changes, etc., which in turn impacts plant growth. Since the types of AR in China is changing, the response of plants to different types of AR has become a research hotspot. In this research, we investigated the responses of Q. acutissima foliage to simulated AR with different SO42−/NO3−(S/N) ratios and pH through chlorophyll contents, chlorophyll fluorescence characteristics, malondialdehyde content and antioxidant enzyme activities. The results showed that the maximal photochemical efficiency of PSⅡ (Fv/Fm) and superoxide dismutase (SOD) activity of Q. acutissima gradually decreased as the increase of NO3− concentration. With the decrease of AR pH, the inhibitory effect of simulated AR on growth rate and photochemical quenching coefficient (qP) gradually increased, and it also induced the increase of SOD and catalase (CAT) activities. Besides, pure NAR with low acidity (pH = 4.5) significantly increased basal diameter growth rate (DGR), chlorophyll content, peroxidase (POD) activity and qP, while decreased Chla/Chlb, fluorescence efficiency, non-photochemical quenching coefficient (NPQ), malondialdehyde (MDA) content and SOD activity. Correlation analysis indicated that the growth rate, chlorophyll content and fluorescence characteristics of Q. acutissima were highly correlated with foliar antioxidant enzyme activities under simulated AR stress. Our results indicated that different types of simulated AR had discrepant influences on the foliage physiological characteristics and above-ground growth of Q. acutissima, but not always negative, which made the protection of Q. acutissima plantation more complicated.

There has been a rapid increase in abandoned mines across China, Consequently, external-soil spray seeding technologies have emerged as a common method for their remediation. However, slope soils are typically unstable and easily collapsed and the nutrients absorbed by plants are insufficient, which complicate ecological restoration. For this study, we added mineral-solubilizing microbes and a water retaining agent to an external-soil spray seeding substrate in Lespedeza bicolor pots. We investigated the soil nutrients, soil enzyme activities, root growth parameters, root tensile properties, and root-reinforced soil shear strengths. The results revealed that the addition of microbes enhanced soil nutrients, soil enzyme activities, and the content of lignin and hemicellulose, which promoted root growth. Further, the addition of a water retaining agent promoted Lespedeza bicolor root growth but decreased the root tensile strength and force. Shear stress under the microbe treatment was more robust than without it. Finally, root growth was correlated with soil nutrients and enzyme activities, whereas the root tensile force and strength were correlated with lignin and cellulose. Our results suggested that the addition of mineral-solubilizing microbes had the capacity to enhance the quality of soils to facilitate the growth of plants. These results provide a new and viable strategy for the ecological restoration of abandon mine sites.

Background: Abandoned mining sites are becoming increasingly common due to anthropogenic activities. Consequently, external-soil spray seeding technology has attracted increasing attention as a strategy to remediate them. However, significant challenges remain that greatly inhibit the efficacy of such technologies, such as insufficient nutrients available for plants. Methods: For this study, we designed an experiment, which involved the addition of mineral-solubilizing microorganisms and R. pseudoacacia seedlings to the external-soil spray seeding (ESSS) substrate, and measured the soil nutrients, enzyme activities, and root growth of R. pseudoacacia. Results: First, the combination of certain mineral-solubilizing microorganisms with ESSS advanced its efficiency by increasing the availability of soil nutrients and soil enzymatic activities in association with R. pseudoacacia. Furthermore, the improvement of root growth of R. pseudoacacia was intimately related to soil nutrients, particularly for soil total nitrogen (TN) and total sulfur (TS). In general, the effects of the J2 (combined Bacillus thuringiensis and Gongronella butleri) treatment for soil nutrients, enzyme activities, and plant growth were the strongest. Conclusion: In summary, the results of our experiment revealed that these mineral-solubilizing microorganisms conveyed a promotional effect on R. pseudoacacia seedlings by increasing the soil nutrient content. These results provide basic data and microbial resources for the development and applications of mineral-solubilizing microorganisms for abandoned mine remediation.

As a well-known Chinese important medicine, Dendrobium resources are increasingly scarce. In order to avoid the quality problems caused by blind cultivation, we predicted the ecologically suitable areas for three species of important Dendrobium species. In this paper, using the maximum entropy model and ArcGIS, we used a database and literature search to collect the known distribution information of Dendrobium, combined with the relevant ecological factors such as climate, elevation and soil, to divide the geographical distribution of Dendrobium into categories, and find out the main ecological factors that affect the distribution of Dendrobium and thus the most suitable regions in China. The results showed that Dendrobium is mainly distributed south of the Yangtze River And the distribution of the most suitable regions was different for each of these three species of Dendrobium species. The potential suitable areas of Dendrobium nobile Lindl, Dendrobium officinale Kimura et Migo, Dendrobium moniliforme (L.) Sw. were approximately 134.19 × 104 km2 (accounting for 13.98 %), 229.08 × 104 km2 (accounting for 23.86 %) and 188.33 × 104 km2 (accounting for 19.62 %) of China’s land area, respectively. Based on our model, annual temperature annual range and annual precipitation are the main ecological variables controlling the distribution of the three species of Dendrobium species, but these three species also have slightly different characteristics. All in all, these species prefer a warm, stable and humid climate and loose soil that is sufficiently aerated and with appropriate moisture properties in order to grow. This will provide a reference for the subsequent introduction, cultivation and local adaptation.

Background The distribution and use of camphor (Cinnamomum camphora L.) trees are constrained by increasing soil salinity in south-eastern China along the Yangtze River. However, the response mechanism of this species to salinity, especially in team of photosynthesis, are unknown. Methods Here, we analysed themorphological, physiological, ultrastructural, and proteomic traits of camphor seedlings under NaCl (103.45 mM) treatment in pot experiments for 80 days. Results The growth was limited because of photosynthetic inhibition, with the most significant disturbance occurring within 50 days. Salinity caused severe reductions in the leaf photosynthetic rate (An), stomatal conductance (gs), maximal chlorophyll fluorescence (Fm), maximum quantum yield of PSII (Fv/Fm), non-photochemical quenching (NPQ), relative quantum efficiency of PSII photochemistry (ΦPSII), photochemical quenching coefficient (qP) and photo-pigment contents (chlorophyll a (Cha), chlorophyll b (Chb), total chlorophyll (Chl)); weakened the antioxidant effects, including those of malondialdehyde (MDA), superoxide dismutase (SOD) and peroxidase (POD); and injured chloroplasts. The physiologicalresults indicated that the main reason for photo-inhibition was oxidative factors induced by NaCl. The proteomic results based on isobaric tags for relative and absolute quantitation (iTRAQ) further confirmedthat photosynthesis was the most significant disrupted process by salinity (P C. camphor.

Acid rain (AR) is a serious issue in China, particularly in the Yangtze River Delta region where the economy has undergone rapid development. Over the last few years, the composition of acid rain in the Yangtze River Delta region has gradually changed from sulfuric acid rain (SAR) to nitric acid rain (NAR) due to controls on SO2 emissions, but increased NOx emissions. These changes have made ecosystems more complex. For this study, we halted AR treatments in Quercus acutissima forest plots that had received simulated AR for one year and monitored them from the following February to November. We investigated their soil resident enzyme and microbial metabolic activities, as well as community functional diversity. The results revealed that AR treatments negatively affected both the soil microbial activity and soil microbial community functional diversity; however, both managed to recover over time, once the AR treatments were stopped. During the AR treatment and recovery periods, four main categories (carbohydrates, carboxylic acids, amino acids, and polymers) were dominantly utilized. The utilization of pyruvic acid, which was affected by the AR treatments, as well as d-mannitol and tween 80, accounted for changes in the peak values of the C substrate groups during the AR treatment recovery period. Finally, changes in the activities of soil enzymes recorded following AR recovery, were closely related to the utilization of six C substrate groups. Our results suggested that the recovery of soils following the cessation of NAR stress was more rapid than from SAR. Further, that short-term NAR could be easily treated during the transformation from SAR to NAR in the Yangtze River Delta region. These results might also enrich the basic data relating to post-AR treatments on the soil environment, while having significance toward guiding further studies on the recovery of ecosystems from AR.

Long term land-use change, such as forest conversion, has been shown to strongly affect soil pore properties. The soil pores mediate soil processes and determine how soil functions. Despite their importance for understanding biological, water, and carbon stability, the properties of soil pores following long term forest conversion remain unclear in subtropical forests. We examined soil nanoscale pores in response to conversion from native forests to plantations and addressed how bacterial and fungal communities influenced soil pore properties. We found significant changes in soil pores 40 years after the conversion from native forests to Chinese fir forests or bamboo forests. The pores in mixed forest soils were similar to those in native forests, while Chinese fir forest soils contained the most pores, followed by bamboo forest soils. Chinese fir forests also had a higher surface area and volume of both total soil pores and macropores, whereas bamboo forests had a higher volume of mesopores and larger specific surface areas of the total, macro-, and mesopores. Both soil bacteria and fungi significantly influenced soil pore properties. The relative abundance of soil bacterial phyla (Planctomycetes and Verrucomicrobia), fungal phylum (Chytridiomycota), and bacterial and fungal diversity negatively affected average pore diameter. In addition, soil fungal phylum (Basidiomycota) and the total sequencing number positively affected soil mesopore volume and the specific surface areas of both total pores and mesopores. Our study demonstrated that forest conversion drove the changes in soil pores at the nanoscale. Changes in soil microbial abundance and diversity may be one of the factors that affect soil nanoscale pores, while soil fungal compositions influence soil mesopores and soil specific surface area.

Dendrobium is widely used in traditional Chinese medicine, which contains many kinds of active ingredients. In recent years, many Dendrobium transcriptomes have been sequenced. Hence, weighted gene co-expression network analysis (WGCNA) was used with the gene expression profiles of active ingredients to identify the modules and genes that may associate with particular species and tissues. Three kinds of Dendrobium species and three tissues were sampled for RNA-seq to generate a high-quality, full-length transcriptome database. Based on significant changes in gene expression, we constructed co-expression networks and revealed 19 gene modules. Among them, four modules with properties correlating to active ingredients regulation and biosynthesis, and several hub genes were selected for further functional investigation. This is the first time the WGCNA method has been used to analyze Dendrobium transcriptome data. Further excavation of the gene module information will help us to further study the role and significance of key genes, key signaling pathways, and regulatory mechanisms between genes on the occurrence and development of medicinal components of Dendrobium.

Cyclobalanopsis glauca is an important afforestation tree species that is widely used for revegetating the karst region of southwest China. Vegetation in this region is regularly commonly subjected to drought stress because of the geology and water shortages. Here, we investigated the influence of two arbuscular mycorrhizal fungi (AMF) Glomus mosseae and Glomus intraradices on the drought tolerance of C. glauca seedlings under greenhouse conditions. AMF-treated and non-AMF-treated C. glauca seedlings were maintained under two different water regimes (well watered: 80 % field capacity; drought stress: 40 % field capacity) for 90 days. The AMF colonization rate was higher under well-watered conditions compared to drought stress conditions. The growth and physiological performance of C. glauca seedlings were significantly affected by drought stress. Under drought stress conditions, mycorrhizal seedlings had greater height, base diameter, leaf area, and biomass compared to non-mycorrhizal seedlings. In addition, under drought conditions, AMF-inoculated seedlings had greater superoxide dismutase and peroxidase activity, higher soluble sugar content, and lower proline content compared to non-inoculated seedlings. Furthermore, AMF colonization increased the phosphorus and potassium content of seedling shoots under both well-watered and drought stress conditions. Therefore, AMF colonization enhanced the drought tolerance of C. glauca seedlings by improving growth performance, nutrient content, the quantity of osmotic adjustment compounds, and antioxidant enzyme activity. The results indicate that AMF are of potential use for the restoration of vegetation in the karst region of southwest China.

Arbuscular mycorrhizal fungi (AMF) inoculation have been shown to enhance host plant growth and rhizosphere soil aggregates largely due to the combined effect of extraradical hyphae and glomalin-related soil proteins but their effects on rocky desertified soils remain unknown. Extensive karst area of southwest China has undergone rocky desertification because of soil erosion and vegetation degradation. Karst soils in this area are mainly composed of silty clay loam developed from carbonate rock erosion under subtropical humid monsoon climate. We tested the hypothesis that AMF colonization of tree seedlings would improve water stable aggregates of degraded karst soil and enhance seedling growth. Seedlings of two tree species, Toona sinensis and Delavaya toxocarpa suitable for afforestation in karst area, were inoculated separately with three AMF, Funneliformis mosseae, Glomus versiforme and Rhizophagus intraradices in pots containing rocky desertified soil. Non-inoculated seedlings were used as control. After 12 months we found that the percentage of water stable aggregates (diameter >0.25 mm; WSA>0.25) in the rhizosphere soil of the inoculated seedlings was increased by 15.6–20.5% compared to control. AMF colonization significantly increased the quantity of aggregates with diameter > 2 mm compared to control but soil aggregates of size class 0.25 – 0.5 mm decreased significantly in inoculated seedlings, regardless of tree species. Shoot biomass of inoculated T. sinensis and D. toxocarpa seedling was increased by 15.7–21.2% and 8.5–20.4%, respectively compared to non-inoculated seedlings. In contrast, AMF inoculation minimally influenced the root biomass of the two tree species. The easily extractable glomalin (EEG) content and mean weight diameter (MWD) of rhizospheric soil of the inoculated seedlings increased by 28.9–75.1% and 31.7–48.1%, respectively compared to control. The AMF colonization was highly correlated with WSA>0.25, EEG and MWD. Overall results support our hypothesis that AMF colonization enhance the quantity of rhizospheric soil aggregates and improve the growth of host seedlings. We conclude that planting tree species inoculated with AMF has a potential for restoration of degraded karst ecosystem. In future research other locally adapted tree and shrub species should be tested following AMF inoculation to prepare a wider planting stocks to be used in restoration of degraded karsts.

Salinity is the primary restriction factor for vegetation conservation and the rehabilitation of coastal areas in Eastern China. Arbuscular mycorrhizal fungi (AMF) have been proved to have the ability to alleviate salt stress in plants. However, the role of AMF in relieving salt stress among indigenous trees species is less well known, limiting the application of AMF in the afforestation of local area. In this study, a salt-stress pot experiment was conducted to evaluate the effects of AMF on Zelkova serrata (Thunb.) Makino, a tree species with significant potential for afforestation of coastal area. The Z. serrata seedlings inoculated with three AMF strains (Funneliformis mosseae 1, Funneliformis mosseae 2, and Diversispora tortuosa) were subjected to two salt treatments (0 and 100 mM NaCl) under greenhouse conditions. The results showed that the three AMF strains had positive effects, to a certain extent, on plant growth and photosynthesis under normal condition. However, only F. mosseae 1 and F. mosseae 2 alleviated the inhibition of growth, photosynthesis, and nutrient uptake of Z. serrata seedlings under salt stress. The two AMF strains mitigated salt-induced adverse effects on seedlings mainly by increasing the leaf photosynthetic ability and biomass accumulation by reducing Na+ content, increasing P, K+, and Mg2+ content, as well as by enhancing photosynthetic pigments content and the stomatal conductance of leaves. These results indicated that AMF inoculation is a promising strategy for the afforestation of coastal areas in Eastern China.

Canopy transpiration is an important component of evapotranspiration, integrating physical and biological processes within the water and energy cycles of forests. Quercus acutissima and Cunninghamia lanceolata are two important, fast‐growing and commercial tree species that have been extensively used for vegetation restoration, water conservation and building artificial forests in the Yangtze River Delta region of China. The primary objective of this study was to characterize sap flow densities of the two species by comparing daytime and nocturnal sap flow patterns and their relationships with environmental factors. Sap flow densities (Sd) were measured between September 2012 and August 2013 using the commercially‐available thermal dissipation probes. Hourly meteorological data were measured in an open field, located 200 m away from the study site, including photosynthetically‐active radiation (Par), air temperature (Ta), relative air humidity (Rh), vapor pressure deficit (Vpd) and precipitation (P). Soil water content (Swc) data were logged hourly in different layers at Q. acutissima and C. lanceolata forests. Results indicated that the mean Sd in summer was higher than that in spring and autumn. Both the Sd of Q. acutissima and C. lanceolata showed distinct diurnal patterns. Nocturnal sap flow densities (Sdn) were noticeable, and both species followed similar declining patterns during our study period. The daytime sap flow density (Sdd) was more sensitive to environmental factors than Sdn. Sap flow density was significant linearly correlated with Par, Vpd and Ta, and Par and Vpd explained the greatest amount of variation in daytime sap flow of Q. acutissima and C. lanceolata, respectively. Our study will enrich knowledge of plantation forest physical and biological processes and provide valuable information for plantation forest management in the Yangtze River Delta region of China.