Effects of Different Chinese Hickory Husk Returning Modes on Soil Nutrition and Microbial Community in Acid Forest Soil

Chinese hickory(Carya cathayensis Sarg.)is an important economic forest in Southeastern China.A large amount of hickory husk waste is generated every year but with a low proportion of returning.Meanwhile,intensive management has resulted in soil degradation of Chinese hickory plantations.This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment,including soil acidity,soil nutrition,and microbial community.The field experiment carried out four treatments:control(CK),hickory husk mulching(HM),hickory husk biochar(BC),and hickory husk organic fertilizer(OF).The phospholipid fatty acid(PLFA)biomarker method was employed to determine the soil microbial community.After one year of treatment,the results showed that:(i)HM and BC significantly increased soil pH by 0.33 and 1.71 units,respectively;(ii)HM,BC and OF treatments significantly increased the soil organic carbon,alkaline nitrogen,available phosphorous,and available potassium.The OF treatment demonstrated the most significant improvement in the soil nutrient;(iii)The soil microbial biomass significantly increased in the HM,BC and OF treatments,and all microbial groups showed an increasing trend.HM treatment increased the fungal/bacterial ratio(F/B).The OF treatment significantly decreased the Shannon-Wiener diversity(H’)and evenness index(J)of the microbial community(P<0.05).Considering the treatments effects,costs,and ease of operation,our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.

Analysis of spatiotemporal variations in the characteristics of soil microbial communities in Castanopsis fargesii forests

Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species.In this study,we evaluated changes in microbial communities in soil samples from C.fargesii forests.The phospholipid fatty acid(PLFA)biomarker method was used to obtain bacteria,fungi,actinomycetes,gram-positive bacteria(G?),gram-negative bacteria(G-),aerobic bacteria,and anaerobic bacteria to investigate spatiotemporal changes in microbial communities during the growing season.The results show that soil microorganisms were mainly concentrated in the upper 20-cm layer,demonstrating an obvious surface aggregation(P<0.05).Large amounts of litter and heavy rainfall during the early growing season resulted in the highest PLFA contents for various microorganisms,whereas relatively low and stable levels were observed during other times.The dominant species during each period were bacteria.G+ or aerobic bacteria were the main bacterial populations,providing insights into the overall trends of soil bacterial PLFA contents.Due to the relative accumulation of refractory substances during the later stages of litter decomposition,the effects of fungi increased significantly.Overall,our findings demonstrate that the main factors influencing microbial communities were litter,rainfall,and soil field capacity.

Decomposition of labile and recalcitrant coniferous litter fractions affected by temperature during the growing season

Temperate coniferous forest soils are considered important sinks of soil organic carbon(C).Fresh C inputs may,however,affect soil microbial activity,leading to increased organic matter decomposition and carbon dioxide production.Litter consists of labile and recalcitrant fractions which are thought to be utilized by distinct microbial communities and at different rates during the growing season.In this study,we incubated the whole litter(LC+RC),the labile(LC)and the recalcitrant(RC)fractions with the coniferous soil at two temperatures representing spring/autumn(10℃)and summer(20℃)for one month.Soil respiration and microbial community composition were regularly determined using phospholipid fatty acids as biomarkers.The LC fraction greatly increased soil respiration at the beginning of the incubation period but this effect was rather short-term.The effect of the RC fraction persisted longer and,together with the LC+RC fraction,respiration increased during the whole incubation period.Decomposition of the RC fraction was more strongly affected by higher temperatures than decomposition of the more labile fractions(LC and LC+RC).However,when we consider the relative increase in soil respiration compared to the dH2 O treatment,respiration increased more at a lower temperature,suggesting that available C is more important for microbial metabolism at lower temperatures.Although C was added only once in our study,no changes in microbial community composition were detected,possibly because the microbial community is adapted to relatively low amounts of additional C such as the amounts naturally found in litter.

Naphthalene exerts non-target effects on the abundance of active fungi by stimulating basidiomycete abundance

As an arthropod biocide,naphthalene has been used in studies of the ecological functions of soil fauna for decades.However,its potential non-target effects on soil microorganisms may affect soil mineralization and litter decomposition processes.Therefore,we conducted an experiment with naphthalene adding to soil surface at a rate of 100 g·m-2 per month to examine the potential non-target effects of this treatment on soil fungal phospholipid fatty acids(PLFAs),18 S rDNA gene copy numbers and community diversity in a subalpine forest of western Sichuan,China.The results showed that naphthalene addition significantly increased fungal PLFAs but did not significantly alter fungal gene copy numbers.A total of 16 phyla,62 genera and 147 Operational taxonomic units(OTUs)were identified through Illumina Mi Seq sequencing analysis.Basidiomycota and Ascomycota were the most abundant phyla in both the control and naphthalene addition plots.Naphthalene addition did not affect the diversity or structure of the soil fungal community,but the increase in some genera of Basidiomycota might contribute to the increase in fungal PLFAs in the naphthalene addition plots.These results suggest that naphthalene exerts non-target effects on the active fungal abundance by stimulating the abundance of specific taxa in subalpine forest soils.The non-target effects of naphthalene on the fungal community should be taken into consideration when it is used to exclude soil fauna.

Effects of Biochar Application on Soil Organic Carbon in Degraded Saline-sodic Wetlands of Songnen Plain,Northeast China

Biochar amendment is considered as an efficient practice for improving carbon storage in soils.However,to what extent that biochar application promotes organic carbon in saline-sodic soils remains poorly understood.By comparing soil organic carbon(SOC)contents change before and after biochar addition,we deciphered the driving factors or processes that control SOC change in response to biochar application.A limited increase in SOC was observed,about by 1.16%-12.80%,even when biochar was applied at the rate of 10%of bulk soil weight.Biochar application enhanced soil dissolved organic carbon(DOC)significantly by up to 67%.It was estimated that about 50%SOC was allocated to small macroaggregates(250-2000μm,CPOC),and SOC in silt and clay-sized particles(<53μm)decreased obviously after biochar addition.Microbial biomass increased with biochar amendment,of which actinomycetes(ACT),fungus(FUN),protozoon(PRO),and bacteria with straight-chain saturated fatty acids(OB)increased remarkably.Multiple linear regression models implied that DOC was governed by ACT and soil N∶P ratio,while SOC mostly depended on CPOC.The principal component analysis and the partial least square path model(PLS-PM)indicated that biochar addition aggravated nitrogen limitation in saline-sodic soils,and effects of microorganisms on regulating SOC greatly depended on nitrogen bioavailability.Biochar application had vastly changed interactions between environmental factors and SOC in saline-sodic soils.Effects of nutrients on SOC shifted to great inhibition from strong stimulation after biochar addition,meanwhile,aggregation was the only factor presenting positive effects on SOC.How to eliminate nutrient limitation and better soil aggregation process should be considered in priority when biochar was used to improve SOC in saline-sodic soils.

Agronomic performances of biodegradable and non-biodegradable plastic film mulching on a maize cropping system in the semi-arid Loess Plateau,China

Biodegradable plastic film mulch (PFM) is considered an alternative to non-biodegradable PFM to mitigate the negative impacts of residual film.However,the agronomic performance of biodegradable PFM in comparison to non-biodegradable PFM still needs to be tested.In this study,we evaluated the effects of biodegradable and non-biodegradable PFM on soil physicochemical properties,microbial community,and enzyme activities,as well as maize growth performance.Biodegradable and non-biodegradable PFM both increased soil temperature,water content,N content,and microbial biomass and maize yield by up to 30%,but decreased soil enzyme activities as compared to no mulching (control,CK).Most soil physicochemical properties,microbial community,and enzyme activities were similar under non-biodegradable and biodegradable PFM at the early stages of maize growth.However,at the late stages,soil temperature,water content,mineral N,NO_(3)^(-)-N,ammonia monooxygenase (AMO) activity,and total phospholipid fatty acids (PLFAs) decreased under biodegradable PFM owing to film fragmentation.White PFM increased soil temperature,water content,and total PLFAs at the early stages of maize growth but decreased soil mineral N and total PLFAs at the late stages,as compared to black PFM.As soil temperature and N availability were the major factors affecting soil microbial community,microbial activity decreased after the fragmentation of biodegradable PFM,owing to the decreased soil temperature,water content,and mineral N.Notably,biodegradable PFM could decrease NO_(3)^(-)-N accumulation in topsoil by decreasing N transformation due to the lower microbial and N-related enzyme (e.g.,AMO) activities,compared with non-biodegradable PFM,which may avoid negative environmental impacts,such as NO_(3)^(-)-N leaching or gas emission after harvest.Maize yield,height,aboveground biomass,and N uptake under biodegradable PFM were similar to those under non-biodegradable PFM during maize growth,implying that biodegradable PFM has no negative impact on crop growth and yield.In general,biodegradable PFM was equivalent to non-biodegradable PFM in terms of maize yield increase and N uptake,but was environmentally friendly.Therefore,biodegradable PFM can be used as an alternative to non-biodegradable PFM in semi-arid areas for sustainable agricultural practices.

Elevated atmospheric CO_(2) impact on carbon and nitrogen transformations and microbial community in replicated wetland

Background:Elevated atmospheric CO_(2) has direct and indirect influences on ecosystem processes.The impact of elevated atmospheric CO_(2) concentration on carbon and nitrogen transformations,together with the microbial community,was evaluated with water hyacinth(Eichhornia crassipes)in an open-top chamber replicated wetland.The responses of nitrogen and carbon pools in water and wetland soil,and microbial community abundance were studied under ambient CO_(2) and elevated CO_(2)(ambient+200μL L^(−1)).Results:Total biomass for the whole plant under elevated CO_(2) increased by an average of 8%(p=0.022).Wetlands,with water hyacinth,showed a significant increase in total carbon and total organic carbon in water by 7%(p=0.001)and 21%(p=0.001),respectively,under elevated CO_(2) compared to that of ambient CO_(2).Increase in dissolved carbon in water correlates with the presence of wetland plants since the water hyacinth can directly exchange CO_(2) from the atmosphere to water by the upper epidermis of leaves.Also,the enrichment CO_(2) showed an increase in total carbon and total organic carbon concentration in wetland soil by 3%(p=0.344)and 6%(p=0.008),respectively.The total nitrogen content in water increased by 26%(p=0.0001),while total nitrogen in wetland soil pool under CO_(2) enrichment decreased by 9%(p=0.011)due to increased soil microbial community abundance,extracted by phospholipid fatty acids,which was 25%larger in amount than that of the ambient treatment.Conclusion:The study revealed that the elevated CO_(2) would affect the carbon and nitrogen transformations in wetland plant,water,and soil pool and increase soil microbial community abundance.

Redox-driven shifts in soil microbial community structure in the drawdown zone after construction of the Three Gorges Dam

Soil redox is a critical environmental factor shaping the microbial community structure and ultimately alters the nutrient cycling.However,the response of soil microbial community structure to prolonged or repeated redox fluctuations is not yet clear.To study the dynamic effects of prolonged redox disturbances to the soil microbial community structure,soil samples experiencing 8,5 and 0 alternating oxic-anoxic cycles within approximately 6 months each year were collected and the microbial community structure were evaluated using phospholipid fatty acid analysis(PLFA)profiles.Prolonged redox disturbances had significant effects on soil physiochemical properties and soil microbial community structure.The relative abundance of straight chain saturated PLFAs,cyclopropyl,and terminal-and mid-branched chain saturated PLFAs increased due to prolonged redox disturbances,but there was a consistent decrease in linear monounsaturated PLFAs and polyunsaturated PLFAs in the fluctuating zone.Prolonged redox disturbances had a negative impact on the total PLFA content(a proxy for biomass).Both the fluctuating zone(8-cycle and 5-cycle plots)and the never flooded zone(0-cycle plots)were dominated by Gram-positive bacteria and a low content of fungi,actinomycetes and protozoa.The fungi and protozoa abundance decreased significantly with an increase in the occurrence of alternating flooding-dry events,suggesting that the prolonged redox disturbance leads to high stress on the fungi and protozoa populations.Moreover,total organic matter(TOC)and C:N ratio,environmental factors that can be influenced by recurring redox fluctuations,also influenced the microbial community structure.

Changes in soil faunal density and microbial community under altered litter input in forests and grasslands

Root and foliar litter inputs are the primary sources of carbon and nutrients for soil fauna and microorganisms,yet we still lack a quantitative assessment to evaluate the effects of root and foliar litter on various groups of soil organisms across terrestrial ecosystems.Here,we compiled 978 paired observations from 68 experimental sites to assess the directions and magnitudes of adding and removing foliar and root litter on the soil faunal density and microbial biomass that was evaluated by phospholipid fatty acids(PLFAs)across forests and grasslands worldwide.We found that litter addition had only a marginal effect on soil faunal density but significantly increased the soil total microbial-,fungal-and bacterial-PLFAs by 13%,14%,and 10%,respectively,across ecosystems,suggesting that the soil microbial community is more sensitive to carbon source addition than soil fauna,particularly in soils with low carbon to nitrogen ratios.In contrast,removing litter significantly decreased the soil faunal density by 17%but had few effects on soil microorganisms.Compared with foliar litter,root litter input had a more positive effect on the development of soil fungal taxa.The effect of both litter addition and removal on soil faunal density and microbial biomass did not differ between humid and arid regions,but a greater influence was observed in grasslands than in forests for soil microbial community.Our results highlight that the increasing litter production under a global greening scenario would stimulate microbial activity in grasslands more than in forests,and this stimulation would be greater for soil microbes than soil fauna.

Dynamic changes in soil chemical properties and microbial community structure in response to different nitrogen fertilizers in an acidified celery soil

To determine the effects of different kinds of nitrogen fertilizer,especially high-efficiency slowrelease fertilizers,on soil pH,nitrogen(N)and microbial community structures in an acidic celery soil,four treatments(CK,no N fertilizer;NR,urea;PE,calcium cyanamide fertilizer;and SK,controlled-release N fertilizer)were applied,and soil pH,total soil N,inorganic N,and soil microbial biomass C were analyzed.Phospholipid fatty acids(PLFAs)were extracted and detected using the MIDI Sherlock microbial identification system.The PE treatment significantly improved soil pH,from 4.80 to>6.00,during the whole growth period of the celery,and resulted in the highest celery yield among the four treatments.After 14 d application of calcium cyanamide,the soil nitrate content significantly decreased,but the ammonium content significantly increased.The PE treatment also significantly increased soil microbial biomass C during the whole celery growth period.Canonical variate analysis of the PLFA data indicated that the soil microbial community structure in the CK treatment was significantly different from those in the N applied treatments after 49 d fertilization.However,there was a significant difference(P<0.05)in soil microbial community structure between the PE treatment and the other three treatments at the end of the experiment.Calcium cyanamide is a good choice for farmers to use on acidic celery land because it supplies sufficient N,and increases soil pH,microbial biomass and the yield of celery.

Effect of rhizosphere on soil microbial community and in-situ pyrene biodegradation

To access the influence of a vegetation on soil microorganisms toward organic pollutant biogegration,this study examined the rhizospheric effects of four plant species(sudan grass,white clover,alfalfa,and fescue)on the soil microbial community and in-situ pyrene(PYR)biodegradation.The results indicated that the spiked PYR levels in soils decreased substantially compared to the control soil without planting.With equal planted densities,the efficiencies of PYR degradation in rhizosphere with sudan grass,white clover,alfalfa and fescue were 34.0%,28.4%,27.7%,and 9.9%,respectively.However,on the basis of equal root biomass the efficiencies were in order of white clover..alfalfa.sudan.fescue.The increased PYR biodegradation was attributed to the enhanced bacterial population and activity induced by plant roots in the rhizosphere.Soil microbial species and biomasses were elucidated in terms of microbial phospholipid ester-linked fatty acid(PLFA)biomarkers.The principal component analysis(PCA)revealed significant changes in PLFA pattern in planted and non-planted soils spiked with PYR.Total PLFAs in planted soils were all higher than those in non-planted soils.PLFA assemblages indicated that bacteria were the primary PYR degrading microorganisms,and that Gram-positive bacteria exhibited higher tolerance to PYR than Gram-negative bacteria did.

Soil microbial community structure and activity in a 100-year-old fertilization and crop rotation experiment

Aims Nitrogen(N)fertilization and lime addition may affect soil micro-bial and nematode communities and ecosystem functions through changing environmental conditions,such as soil pH and soil organic carbon.The objectives of this experiment were to examine the impact of N input and liming on soil microbial and nematode communities and to identify the key environmental determinant of community composition in a century-old fertilization and crop rota-tion experiment.Methods The field experiment consisting of a 3-year crop rotation regime was established in 1911 in southeastern USA.Four treatments,(i)no-input control,(ii)NPK with winter legume,(iii)PK with legume and lime and(iv)NPK with legume and lime,were included in this study.soil samples collected at the 0-5 cm depth were used to determine the bacterial growth rate by the 3H-thymidine incorporation technique.Incorporation of 13C into neutral lipids,glycolipids and phospholipid fatty acids(PlFas)was measured after incubation of soil with 13C-labeled acetate for 24 h.Free-living nematodes in fresh soil were extracted using a density sucrose centrifugal flotation method and identified to trophic group level.Important Findingsliming resulted in a 10-fold increase in bacterial growth rates compared with the no-input control,whereas N fertilization had no significant effect.multivariate analysis of PlFa profiles showed that soil microbial community composition was different among the four treatments;the difference was primarily driven by soil pH.PlFas indicative of gram-negative bacteria covaried with soil pH,but not those of fungi and actinobacteria.liming enhanced 13C incorpora-tion into neutral lipids,glycolipids and phospholipids by 2-15 times.In addition,13C incorporation into 16:0,16:1ω9,18:1ω9,18:1ω7 and 18:2ω6 were greater than other PlFas,suggesting that gram-negative bacteria and fungi were more active and sensitive to simple C input.bacterivorous nematodes were the dominant trophic group in the soil,but no significant differences in nematode communities were found among the treatments.our results suggest that soil pH had a greater impact than N fertilization on soil microbial community composition and activity in a crop rotation system including legumes.

Changes in the soil microbial communities of different soil aggregations after vegetation restoration in a semiarid grassland,China

Soil aggregate fractions can regulate microbial community composition and structure after vegetation restoration.However,there has been less focus on the effects of soil aggregate fractions on the distributions of microbial communities.Here,we used phospholipid fatty acid(PLFA)analysis to explore the effects of different years of vegetation restoration(a 35-year-old Thymus mongolicus community(Re-35yrs)and a 2-year-old nongrazing grassland(Ug-2yrs))on microbial communities within different soil aggregate sizes(<0.25 mm,0.25–1 mm,1–2 mm,2–3 mm,3–5 mm and>5 mm).The results indicated that the amount of total PLFA in Re-35yrs was 10 times greater than that in Ug-2yrs.The soil aggregate stability increased with increasing duration of vegetation restoration.In Re-35yrs,the total PLFA shown an increase as the soil aggregate size increased,and the highest values were observed in 3–5 mm.Ug-2yrs differed from Re-35yrs,the soil microbial diversity was higher in medium particle sizes(1–2 mm and 2–3 mm)and lower in microaggregates(<0.25 mm and 0.25–1 mm)and macroaggregates(3–5 mm and>5 mm).Soil microbial diversity was highest in large particle size aggregates,which resulted in low environmental stress and strong stability.The same tendency was observed in the high values of cyc/prec,S/M and soil organic matter,which indicated a lower turnover speed(F/B)of fungal energy utilization and a higher fixation rate.After years of natural restoration,the soil microbial community generally transformed from nutrient-rich to heterotrophdominant,especially in microaggregates(reflected in the G^(+)/G^(–)ratio).

Responses of soil phosphorus pools accompanied with carbon composition and microorganism changes to phosphorus-input reduction in paddy soils

In rice-wheat rotation systems, changes in soil phosphorus(P) pools and microorganisms in rice-growing seasons have been studied;however, further investigations are required to test whether these indexes exhibit different responses in wheat-growing seasons. Additionally, such studies need to include potential variations in soil carbon(C) structure and microbial community composition. In this study, a long-term rice-wheat rotation P-input reduction experiment was conducted to observe the variations in soil P pools and C composition in the 7th wheat season and to investigate the responses of soil enzyme activity and microbial communities. Four P fertilization treatments were included in the experiment, i.e., P application for rice season only(PR), for wheat season only(PW), and for both rice and wheat seasons(PR+W) and no P application in either season(Pzero). Compared with PR+W treatment, Pzero treatment significantly decreased(P < 0.05) labile and stable P pools. Different P fertilization regimes altered soil microbial community composition and enzyme activity, whereas C composition did not vary. However, PW treatment resulted in relatively more O-alkyl-C than PR treatment and the highest number of microorganisms. Besides, the higher ratios of fungi/bacteria and Gram-positive bactetia/Gram-negative bactetia were related to labile C pools, particularly O-alkyl-C, as opposed to recalcitrant C. Our results clarified the status of soil P pools, C chemistry, and the response of microorganisms under dry-farming conditions in the P input-reduced rice-wheat rotation system.