Black locust coppice stands homogenize soil diazotrophic communities by reducing soil net nitrogen mineralization

Background:Black locust(BL,Robinia pseudoacacia)is considered a promising tree species for reforestation due to its great ability to fix nitrogen.However,after two or three coppice-harvesting rotations,the productivity of BL declines.Whether soil microbial communities are affected and how these groups correlate with the nitrogen mineralization process across multi-generation stands remains unclear.Methods:We investigated the composition and structure of free-living nitrogen-fixing microorganisms(diazotrophs)by sequencing the marker gene nifH and compared these results to levels of soil nitrogen mineralization in the bulk soil and rhizosphere in black locust plantations on Mount Tai,China.Results:The results showed multi-generation BL coppice plantations decreased the total soil nitrogen(N),soil phosphorus(P),soil microbial biomass N(MBN),soil microbial biomass C(MBC),soil nitrification rate(Rn),soil ammonification rate(Ra),and net soil N mineralization rate(Rm),but significantly increased the concentration of soil NH_(4þ)-N to maintain sufficient NO_(3)^(-)N.The dominant species in bulk soil and rhizosphere changed from Rhodopseudomonas(22.62%and 15.76%),unclassified_c_Alphaproteobacteria(22.37%and 29.28%),unclassified_o_Rhizobiales(15.40%and 13.31%),Bradyrhizobium(12.00%and 11.74%)in seedling plantations to Bradyrhizobium(45.95%and 47.86%)and Rhodopseudomonas(43.56%and 41.84%)in coppice plantations,respectively.Mantel test and Redundancy analysis(RDA)revealed that Rn,Ra,and Rm were the most important factors shaping the diazotrophic communities.Conclusions:Our results suggest that the multi-generation BL coppice plantation can homogenize soil diazotrophic communities,which is mainly regulated by the available N loss caused by nitrogen mineralization.Strengthening the management technology of coppice plantations will provide more beneficial external consumption.

Cloning and expression analysis of the FvNCED3 gene and its promoter from ash(Fraxinus velutina)

The 9-cis-epoxycarotenoid dioxygenase(NCED)gene is rate-limiting in abscisic acid(ABA) biosynthesis.In this study, an NCED gene, designated FvNCED3(KY008746), was cloned from velvet ash(Fraxinus velutina Torr.) with a RACE method. The full length c DNA of FvNCED3 encodes a 573-amino acid polypeptide.Sequencing analysis showed that the FvNCED3 protein was highly homologous to other NCED proteins. The expression patterns of FvNCED3 in different ash organs were analyzed by real-time PCR which revealed that FvNCED3 expression levels were highest in leaves and lowest in roots. The gene expression patterns of FvNCED3 under abiotic stress indicated that its expression increased under drought, salt and ABA stress and decreased due to high and low temperatures. There were no obvious changes under ultraviolet light. The 1094-bp upstream sequence 5' flank regulation region of the FvNCED3 gene was also cloned from ash using the Genome Walking method. To assess the activity of the FvNCED3 promoter, a p FvNCED3 p::GUS plant expression vector was constructed for tobacco transformation. GUS expression of the FvNCED3 GUS enzyme activity was detected in almost all transgenic tobacco tissues, especially in the young leaves,stigma, anther, ovule and ovary. After treating the transgenic tobacco with NaCl and placing it under drought stress, GUS staining of tobacco leaves increased compared with that under normal growth conditions. This result indicates that gene expression driven by the FvNCED3 promoter can be induced by salt and drought stress.

Impact of Robinia pseudoacacia stand conversion on soil properties and bacterial community composition in Mount Tai,China

Background:Robinia pseudoacacia is a widely planted pioneer tree species in reforestations on barren mountains in northern China.Because of its nitrogen-fixing ability,it can play a positive role in soil and forest restoration.After clearcutting of planted stands,R.pseudoacacia stands become coppice plantations.The impacts of shifting from seedling to coppice stands on soil bacterial community and soil properties have not been wel described.This study aims to quantify how soil properties and bacterial community composition vary between planted seedling versus coppice stands.Methods:Nine 20 m×20 m plots were randomly selected in seedling and coppice stands.The bulk soil and rhizosphere soil were sampled in summer 2017.Bulk soil was sampled at 10 cm from the soil surface using a soil auger.Rhizosphere soil samples were col ected using a brush.The soil samples were transported to the laboratory for chemical analysis,and bacterial community composition and diversity was obtained through DNA extraction,16 S r RNA gene amplification and high-throughput sequencing.Results:The results showed that,compared to seedling plantations,soil quality decreased significantly in coppice stands,but without affecting soil exchangeable Mg^(2+) and K^(+).Total carbon(C)and nitrogen(N)were lower in the rhizosphere than in bulk soil,whereas nutrient availability showed an opposite trend.The conversion from seedling to coppice plantations was also related to significant differences in soil bacterial community structure and to the reduction of soil bacterialα-diversity.Principal component analysis(PCA)showed that bacterial community composition was similar in both bulk and rhizosphere soils in second-generation coppice plantations.Special y,the conversion from seedling to coppice stands increased the relative abundance of Proteobacteria and Rhizobium,but reduced that of Actinobacteria,which may result in a decline of soil nutrient availability.Mantel tests revealed that C,N,soil organic matter(SOM),nitrate nitrogen(NO^(-)+(3)-N)and available phosphorus positively correlated with bacterial community composition,while a variation partition analysis(VPA)showed that NO^(-)+(3)-N explained a relatively greater proportion of bacterial distribution(15.12%),compared with C and SOM.Surprisingly,N showed no relationship with bacterial community composition,which may be related to nitrogen transportation.Conclusions:The conversion from seedling to coppice stands reduced soil quality and led to spatial-temporal homogenization of the soil bacterial community structure in both the rhizosphere and bulk soils.Such imbalance in microbial structure can accelerate the decline of R.pseudoacacia.This may affect the role of R.pseudoacacia coppice stands in soil and forest restoration of barren lands in mountain areas.

Effects of 1-aminobenzotriazole on the growth and physiological characteristics of Tamarix chinensis cuttings under salt stress

vegetation restoration is a main ecological remediation technology for greening saline and alkaline soils.The objectives of this study were to determine the effect of1-aminobenzotriazole(ABT-1) on the growth and physiology of Tamarix chinensis under salt stress and to determine a suitable ABT-1 concentration and soil salinity(Sc) for propagating T.chihehsis-cuttings.Cuttings were soaked in water and ABT-1 solutions at three concentrations(50,100,and 200 mg L^(-1)) and propagated in pots containing four soil salinity levels,mild(0.3%),moderate(0.6%),and severe(0.9% and 1.2%),and compared with a control.The cuttings were measured to determine growth indices and physiological and biochemical indices(e.g.,chlorophyll content,superoxide dismutase activity,peroxidase activity,and malondialdehyde content).ABT-1 was effective in improving survival,growth,and physiological processes of cuttings under salt stress.However,there was a threshold effect when using ABT-1 to facilitate propagation under salt stress.ABT-1 effects were insignificant when applied at low concentrations(<100 mg L^(-1)).At a high concentration(> 100 mg L^(-1)),ABT-1 limited growth and physiological activities.Under a salt stress level(Sc ≤0.9%),ABT applied at a 100 mg L^(-1)concentration increased chlorophyll content and superoxide dismutase and peroxidase activities in the leaves and reduced malondialdehyde accumulation and membrane lipid peroxidation effects.As a result,ABT-1 enhanced the resistance of T.chinensis to salt stress.However,under high salt stress(>0.9%) and ABT-1 concentration(> 100 mg L^(-1)),the physiological regulatory ability of T.chinensis seedlings weakened.T.chinensis grew well at a salt stress ≤0.9% and ABT ≤100 mg L^(-1) and exhibited relatively high physiological regulatory ability and high salt adaptability.

Phytoremediation Potential of Three Species of Macrophytes for Nitrate in Contaminated Water

Three species of aquatic plants (Scirpus validus, Phragmites australis and Acorus calamus) were used as experimental materials to study their capacity to purify contaminated water and their effects on water pH and dissolved oxygen (DO). The water was contaminated with different concentrations of nitrate (5 mg/L, 15 mg/L and 25 mg/L). The results indicated that the concentration of nitrate, species of aquatic plant and their interaction significantly impacted denitrification (P = 0.00). Under the same concentrations, the three species of aquatic plants provided varying degrees of purification. Acorus calamus provided effective purification under all three concentrations of nitrate wastewater, with removal percentages of 87.73%, 83.80% and 86.72% for nitrate concentrations of 5 mg/L, 15 mg/L and 25 mg/L, respectively. In terms of the purification ability by unit fresh weight, Acorus calamus exhibited the worst purification capacity, whereas the capacities of Scirpus validus and Phragmites australis were higher. The purification capacity of Scirpus validus for the three concentrations was as follows: 0.08 mg/(L&middot;g FW), 0.29 mg/(L&middot;g FW), and 0.51 mg/(L&middot;g FW). The capacity of Phragmites australis was 0.07 mg/(L&middot;g FW), 0.25 mg/(L&middot;g FW), and 0.53 mg/(L&middot;g FW). The capacity of Acorus calamus was 0.04 mg/(L&middot;g FW), 0.12 mg/(L&middot;g FW), and 0.21 mg/(L&middot;g FW). Under increased concentrations of nitrate, the three species of aquatic plants exhibited various degrees of increased purification capacity. Under the different concentrations of nitrate, the three species exhibited the same trends with respect to water pH and DO, increasing first and then falling. The pH remained at approximately 7.5, and the DO fell to 4.0 mg/L. A comprehensive analysis reveals that Acorus calamus provides excellent nitrate purification, although by unit fresh weight, both Scirpus validus and Phragmites australis provide superior purification capacity.

T-S Fuzzy Remote Sensing Monitoring Model of Snail Distribution by Landsat 8 and Sentinel 2 Data

Approximately half of the world’s population is at the risk of at least one vector-borne parasitic disease.The survival of intermediate hosts of vector-borne parasitic diseases is governed by various environmental factors,and remote sensing can be used to characterize and monitor environmental factors related to intermediate host breeding and reproduction,and become a powerful means to monitor the vector-borne parasitic diseases.Schistosomiasis is a parasitic disease that menaces human health.Oncomelaniahupensis(snail)is the unique intermediate host of Schistosoma,so monitoring and controlling the number of snail is key to reduce the risk of schistosomiasis transmission.In this paper,Landsat 8 OLI and Sentinel 2 MSI data had been used to obtain the environmental factors(vegetation,soil,temperature,terrain et al.),which are related to the multiplying and transmission of intermediate host.Then this study used T-S(Takagi-Sugeno)Fuzzy RS model to establish a new suitable index membership function due to the different RS data,and a long time series monitoring of snail distribution in Dongting Lake from 2014 to 2018 was achieved.A comparative analysis was performed to validate the predicted results against the field survey data.The results demonstrated the accuracy of the developed model in predicting the distribution of snails.

Evaluation on the fresh eating quality of tree peony flowers

Tree peony(Paeonia suffruticosa)is an ornamental and medicinal plant in China.The fresh eating of flower petals has gradually become a new idea for further development.This study analyzed the sensory indexes,nutritional indexes and antioxidant indexes of fresh flowers of five cultivars,namely,‘Fengdan’(P.ostia‘Fengdan’),‘Xiangyu’(P.suffruticosa‘Xiangyu’),‘Zhaofen’(P.suffruticosa‘Zhanfen’),‘Luoyanghong’(P.suffruticosa‘Luoyanghong’)and‘High Noon’(P.‘High Noon’),to provide a theoretical basis for eating fresh tree peony flowers.The aroma volatiles of petals mainly comprised terpenes,alcohols and alkanes.‘Luoyanghong’and‘High Noon’have brighter colors.The taste test showed that‘Luoyanghong’,‘High Noon’and‘Xiangyu’were the most palatable.‘High Noon’contained the highest soluble sugar content,‘Luoyanghong’contained the highest starch and vitamin C(VC)levels,and‘Zhaofen’contained the highest soluble protein content.The contents of bioactive compounds were the highest in‘Luoyanghong’,and superoxide dismutase(SOD)activity was the highest in‘Xiangyu’.The petals were rich in essential amino acids,with the highest amount in‘Xiangyu’.‘Luoyanghong’and‘High Noon’showed strong antioxidant capacity.Therefore,tree peony flowers have excellent sensory qualities,abundant nutrients and strong antioxidant activity and could be further developed as a food to be eaten fresh.The results showed that tree peony flowers had great edible potential.Flowers of red and yellow cultivars can be considered for fresh eating on the basis of the traditional consumption of white and pink tree peony flowers.

Estimating leaf water content at the leaf scale in soybean inoculated with arbuscular mycorrhizal fungi from in situ spectral measurements

Leaf water content(LWC)of crops is a suitable parameter for evaluation of plant water status and arbuscular mycorrhizal effect on the host plant under drought stress.Remote sensing technology provides an effective avenue to estimate LWC in crops.However,few LWC retrieval models have been developed specifically for the arbuscular mycorrhizal inoculated crops.In this study,soybean with inoculation and non-inoculation treatments were planted under the severe drought,moderate drought and normal irrigation levels.The LWC changes under different treatments at the 30 th,45 th and 64 th day after the inoculation were investigated,and the spectral response characteristics of inoculated and non-inoculated soybean leaves under the three drought stresses were analyzed.Five types of spectral variables/indices including:raw spectral reflectance(R),continuum-removed spectral reflectance(R C),difference vegetation index(DVI),normalized difference vegetation index(NDVI)and ratio vegetation index(RVI)were applied to determine the best estimator of LWC.The results indicate that LWC decreased as the aggravating of drought stress levels.However,LWC in inoculated leaves was higher than that in the counterparts under the same drought stress level,and the values of raw reflectance measured at inoculated leaves were lower than the non-inoculated leaves,especially around 1900 nm and 1410 nm.These water spectral features were more evident in the corresponding continuum-removed spectral reflectance.The newly proposed DVI C(2280,1900)index,derived from the continuum-removed spectral reflectance at 2280 nm and the raw spectral reflectance at 1900 nm in DVI type of index,was the most robust for soybean LWC assessment,with R 2 value of 0.72(p<0.01)and root mean square error(RMSE)and mean absolute error(MAE)of 2.12%and 1.75%,respectively.This study provides a means to monitor the mycorrhizal effect on drought-induced crops indirectly and non-destructively.