Temporal and environmental factors drive community structure and function of methanotrophs in volcanic forest soils

Methanotrophs,organisms that obtain oxygen by oxidizing methane,are recognized as the only known biological sink for atmospheric CH_4,and forest soil methanotrophs play crucial roles in mitigating global warming.The succession patterns of methanotrophic communities and functions in Wudalianchi volcano forest soils could provide a basis for the study of evolutionary mechanisms between soil microorganisms,the environment,and carbon cycling of temperate forest ecosystems under climate change.In this study,the characteristics and drivers of methanotrophic community structure and function of two volcanic soils at different stages of development are analyzed,including an old volcano and a new volcano,which most recently erupted 300 years and 17-19×10^(5)years ago,respectively,and a non-volcano hills as control,based on space for time substitution and Miseq sequencing and bioinformation technology.The results showed that CH_(4) fluxes were significantly higher in old-stage volcano forest soils than new-stage forest soils and non-volcano forest soils.There were significant differences in the community composition and diversity of soil methanotrophs from different volcano forest soils.Methylococcus was the dominant genus in all soil samples.Additionally,the relative abundance of Methylococcus,along with Clonothrix,Methyloglobulus,Methylomagum,Methylomonas and Methylosarcina,were the important genera responsible for the differences in methanotrophic community structure in different volcano forest soils.The relative abundance of methanotroph belonging toγ-proteobacteria was significantly higher than that belonging toα-proteobacteria(P<0.05).Chao1,Shannon and Simpson indices of soil methanotrophic community were significantly lower in new-stage volcanos and were significantly affected by bulk density,total porosity,p H,nitrate,dissolved organic carbon and dissolved organic nitrogen.There were significant differences in community structure between new-stage and old-stage volcanoes.Bulk density and p H are important soil properties contributing to the divergence of methanotrophs community structure,and changes in soil properties due to soil development time are important factors driving differences in methanotrophs communities in Wudalianchi volcanic soils.

Nitrification and denitrification as sources of gaseous nitrogen emission from different forest soils in Changbai Mountain

The contributions of nitrification and denitrification to N2O and N2 emissions from four forest soils on northern slop of Changbai Mountain were measured with acetylene inhibition methods. In incubation experiments, 0.06% and 3% C2H2 were used to inhibit nitrification and denitrification in these soils, respectively. Both nitrification and denitification existed in these soils except tundra soil, where only denitrification was found. The annually averaged rates of nitrification and denitrification in mountain dark brown forest soil were much higher than that in other three soils. In mountain brown coniferous soil, contributions of different processes to gaseous nitrogen emissions were Denitrification N2O>nitrification N2O>Denitrification N2. The same sequence exists in mountain soddy soil as that in the mountain brown coniferous soil. The sequence in mountain tundra soil was Denitrification N2O>Denitrification N2.

Effect of Rock Fragments on Tracer Transport in Broadleaved and Coniferous Forest Soils: Column Study

This study investigated the effect of rock fragments on tracer transport in broadleaved and coniferous forest soils from the 0 - 100 cm depth of Gongga Mountain in eastern margin of Qinghai Tibetan Plateau. Using repacked soil columns (20 cm in height and 10 cm in diameter) with different rock fragments contents (0%, 5%, and 15% in v/v), breakthrough curves of bromide (as non-reactive tracer) were obtained under saturated condition. A two-region model was applied and the parameters were estimated by inverse modeling. Results show that with increasing rock fragment content the dispersivity (λ) generally increased while the mobile-immobile partition coefficient (β) and the mass transfer coefficient (ω) decreased. The presence of rock fragments led to an increase in the fraction of immobile domain as well as soil tortuosity. A plausible explanation is that the soil beneath the rock fragments behaved as immobile domain and soil-rock interfaces could serve as preferential flow paths.

Deadwood affects the soil organic matter fractions and enzyme activity of soils in altitude gradient of temperate forests

The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising north(N)and south(S)exposure along the altitudinal gradient(600,800,1000 and 1200 m a.s.l.)was set up.By comparing the properties of decomposing deadwood and those of the soils located directly beneath the decaying wood we drew conclusions about the role of deadwood in the shaping of soil organic matter fractions and soil carbon storage in different climate conditions.The basic properties,enzymatic activity and fractions of soil organic matter(SOM)were determined in deadwood and affected directly by the components released from decaying wood.Heavily decomposed deadwood impacts soil organic matter stabilization more strongly than the less decayed deadwood and the light fraction of SOM is more sensitive to deadwood effects than the heavy fraction regardless of the location in the altitude gradient.Increase in SOM mineral-associated fraction C content is more pronounced in soils under the influence of deadwood located in lower locations of warmer exposure.Nutrients released from decaying wood stimulate the enzymatic activity of soils that are within the range of deadwood influence.

Quantification and depth distribution analysis of carbon to nitrogen ratio in forest soils using reflectance spectroscopy

Forest soils have large contents of carbon(C)and total nitrogen(TN),which have significant spatial variability laterally across landscapes and vertically with depth due to decomposition,erosion and leaching.Therefore,the ratio of C to TN contents(C∶N),a crucial indicator of soil quality and health,is also different depending on soil horizon.These attributes can cost-effectively and rapidly be estimated using visible-near infrared-shortwave infrared(VNIR-SWIR)spectroscopy.Nevertheless,the effect of different soil layers,particularly over large scales of highly heterogeneous forest soils,on the perfor-mance of the technique has rarely been attempted.This study evaluated the potential of VNIR-SWIR spectroscopy in quantification and variability analysis of C∶N in soils from different organic and min-eral layers of forested sites of the Czech Republic.At each site,we collected samples from the litter(L),fragmented(F)and humus(H)organic layers,and from the A_(1)(depth of 2-10 cm)and A_(2)(depth of 10-40 cm)mineral layers providing a total of 2505 samples.Support vector machine regression(SVMR)was used to train the prediction models of the selected attributes at each individual soil layer and the merged layer(profile).We further produced the spatial distribution maps of C∶N as the target attribute at each soil layer.Results showed that the prediction accuracy based on the profile spectral data was adequate for all attributes.Moreover,F was the most accurately predicted layer,regardless of the soil attribute.C∶N models and maps in the organic layers performed well although in mineral layers,models were poor and maps were reliable only in areas with low and moderate C∶N.On the other hand,the study indicated that reflectance spectra could efficiently predict and map organic layers of the forested sites.Although,in mineral layers,high values of C∶N(≥50)were not detectable in the map created based on the reflectance spectra.In general,the study suggests that VNIR-SWIR spectroscopy has the feasibility of modelling and mapping C∶N in soil organic horizons based on national spectral data in the forests of the Czech Republic.

The potential for an old-growth forest to store carbon in the topsoil:A case study at Sasso Fratino,Italy

There is considerable interest devoted to oldgrowth forests and their capacity to store carbon(C)in biomass and soil.Inventories of C stocks in old-growth forests are carried out worldwide,although there is a lack of information on their actual potential for C sequestration.To further understand this,soil organic carbon(SOC)was measured in one of Italy's best-preserved old-growth forests,the Sasso Fratino Integral Nature Reserve.This reserve is on the World Heritage List along with other ancient beech forests of Europe,and it is virtually untouched due to the steepness of the terrain,even before legal constraints were imposed.Although the sandstone-derived soils are often shallow,they are rich in organic matter.However,no quantification had been carried out.By systematically sampling the topsoil across the forest,we accurately determined the average amount of SOC(62.0±16.9 Mg ha^(–1))and nitrogen(4.0±1.2 Mg ha^(–1))in the top 20 cm.Using the CENTURY model,future dynamics of SOC stocks were predicted to 2050 according to two climate scenarios,A1F1 and B2,the first of high concern and the second more optimistic.The model projected an increase of 0.2 and 0.3 Mg ha^(–1)a^(–1)by 2030 under the A1F1 and B2 scenarios,respectively,suggesting that the topsoil in old-growth forests does not reach equilibrium but continues accumulating SOC.However,from 2030 to 2050,a decline in SOC accumulation is predicted,indicating SOC net loss at high altitudes under the worst-case scenario.This study confirms that soils in oldgrowth forests play a significant role in carbon sequestration.It also suggests that climate change may affect the potential of these forests to store SOC not only in the long term but also in the coming years.

Evaluation of Soil Fertility Quality and Environmental Driving Factors in Different Soil Types of Artificial Forests

The aim was to clarify the environmental driving factors of soil fertility indicators in artificial forests of Guangxi and comprehensively evaluate the soil fertility level.By collecting data on the current status of soil in artificial forests,the spatial distribution of major soil fertility indicators was analyzed,and the distribution map of the fertility index of artificial forests in the entire region and the comprehensive fertility index of artificial forests of different soil types were obtained.Canonical correspondence analysis method was used to analyze soil fertility indicators and environmental factors,and the environmental driving factors of soil fertility indicators for artificial forests of the main soil types in Guangxi were obtained.The results showed that over 90%of the soil fertility index of artificial forests in the entire region was between 0.20 and 0.50.The order of soil fertility index of different soil types of artificial forests from high to low was yellow brown soil>yellow red soil>yellow soil>red soil>limestone soil>latosolic red soil>laterite.In artificial forests of latosolic red soil,the correlation between soil alkaline nitrogen and organic matter,annual average temperature was high,while the correlation between soil available phosphorus and organic matter,pH was high,and the correlation between soil available potassium and environmental factors such as slope,altitude,rainfall,accumulated temperature,and slope aspect was high.In artificial forests of red soil,the correlation between soil alkaline nitrogen and slope,altitude was high,while the correlation between soil available phosphorus and accumulated temperature,rainfall was high,and the correlation between soil available potassium and pH was high.In artificial forests of limestone soil,there was a high correlation between soil alkaline nitrogen and slope,organic matter,a high correlation between soil available phosphorus and accumulated temperature,rainfall,and a high correlation between soil available potassium and pH.

Effects of the type of forest alteration on gross nitrogen mineralization in soils of southern India

Change in land-use practices can result in major shifts in the cycling of various elements,particularly nitrogen(N),which is prone to anthropogenic perturbations.For quantifying these shifts,accurate measurements of rates of biogeochemical transformations of N are needed.We used the(^(15)N) isotope dilution technique to understand the effects of the types of forest alteration on(N) transformation rates by comparing gross N mineralization and ammonium(NH_(4)^(+)) consumption rates in soils of a managed forest,an unmanaged forest,and a rubber plantation in Kerala,India.Overall,nitrate(NO_3~-) dominated soils of the managed and unmanaged forests,whereas soils in the rubber plantation showed relatively higher NH_(4)^(+) concentration.Total N(TN) and total organic carbon(TOC) concentrations were the highest under the rubber canopy(TN:1.49±0.02 mg N g^(-1);TOC:7.96±0.86 mg C g^(-1)).In soils of all three forest types,gross N mineralization rates were higher compared to NH_(4)^(+) consumption rates.Despite high TN and TOC concentrations,the rates of gross N mineralization and NH_(4)^(+) consumption were considerably lower in the rubber plantation(mineralization:1.08±0.08 mg N kg^(-1)d^(-1);consumption:0.85±0.09 mg N kg^(-1) d^(-)) compared to the managed(mineralization:3.71±0.35 mg N kg^(-1) d^(-1);consumption:2.20±1.41 mg N kg^(-1) d^(-1)) and unmanaged(mineralization:2.20±1.07 mg N kg^(-1) d^(-1);consumption:1.39±0.27 mg N kg^(-1) d^(-1)) forests.The lower NH_(4)^(+) consumption rates in the rubber plantation led to significantly higher(p<0.05) residence time of NH_(4)^(+)(~4 days) compared to the managed and unmanaged forests(<2 days),possibly contributing to acidification of rubber soils(pH~4.8).These results together suggest that replacement of naturally grown forests with a mono-cropped plantation such as rubber negatively impact rates of N transformation processes in tropical soils and imply that change in tree species composition of naturally grown forests can adversely affect soil microbial activity.We recommend intercropping these plantations with commercial crops to maintain soil microbial diversity and biogeochemical cycling for sustainable forest management.

Profile distribution and seasonal dynamics of water-extractable carbohydrate in soils under mixed broad-leaved Korean pine forest on Changbai Mountain

Carbohydrate represents an important part of the soil labile organic carbon pool. Water soluble carbohydrate drives the C cycle in forest soil by affecting microbial activity and hot water extractable car- bohydrate is thought related to soil carbon sequestration due to the asso- ciation with soil aggregation. In a temperate forest region of northeast China, Changbai Mountain, we investigated the abundance, spatial dis- tribution, and seasonal dynamics of cool and hot-water extractable car- bohydrate in soils under mixed broad-leaved Korean pine forest. The concentrations of cool-water extractable carbohydrate （CWECH） in three soil layers （0-5, 5-10, 10-20 cm） ranged from 4.1 to 193.3 g.kg-1 dry soil, decreasing rapidly with soil depth. On an annual average, the CWECH concentrations in soils at depths of 5-10 and 10-20 cm were 54.2% and 24.0%, respectively, of that in the 0-5 cm soil layer. CWECH showed distinct seasonal dynamics with the highest concentrations in early spring, lowest in summer, and increasing concentrations in autumn. Hot-water extractable carbohydrate （HWECH） concentrations in three soil layers ranged from 121.4 to 2026.2 g.kgq dry soil, which were about one order of magnitude higher than CWECH. The abundance of HWECH was even more profile-dependent than CWECH, and decreased more rapidly with soil depth. On an annual average, the HWECH concentration in soils 10-20 cm deep was about one order of magnitude lower than that in the top 0-5 cm soil. The seasonality of HWECH roughly tracked that of CWECH but with seasonal fluctuations of smaller amplitude. The car- bohydrate concentrations in cool/hot water extracts of soil were positively correlated with UV254 and UV2s0 of the same solution, which has implications for predicting the leaching loss of water soluble organic carbon.

Cattle manure biochar and earthworm interactively affected CO_(2)and N_(2)O emissions in agricultural and forest soils:Observation of a distinct difference

The application of manure-derived biochar offers an alternative to avoid the direct application of manure to soil causing greenhouse gas emission.Soil fauna,especially earthworms,can markedly stimulate carbon dioxide(CO_(2))and nitrous oxide(N_(2)O)emissions from soil.This study therefore investigated the effect of cattle manure biochar(added at rates of 0,2%,or 10%,coded as BC0,BC2 and BC10,respectively)application,with or without earthworm Aporrectodea turgida,on emissions of CO_(2) and N_(2)O and changes of physic-chemical properties of agricultural and forest soils in a laboratory incubation experiment.The BC10 treatment significantly enhanced cumulative CO_(2) emissions by 27.9%relative to the untreated control in the agricultural soil.On the contrary,the BC2 and BC10 treatments significantly reduced cumulative CO_(2) emissions by 16.3%–61.1%and N_(2)O emissions by 92.9%–95.1%compared to the untreated control in the forest soil.The addition of earthworm alone significantly enhanced the cumulative CO_(2) and N_(2)O fluxes in agricultural and forest soils.Cumulative CO_(2) and N_(2)O fluxes were significantly increased when BC2 and BC10 were applied with earthworm in the agricultural soil,but were significantly reduced when BC10 was applied with earthworm in the forest soil.Our study demonstrated that biochar application interacted with earthworm to affect CO_(2) and N_(2)O emissions,which were also dependent on the soil type involved.Our study suggests that manure biochar application rate and use of earthworm need to be carefully studied for specific soil types to maximize the climate change mitigation potential of such management practices.

N_2O emissions from forest and grassland soils in northern China

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C:N:P stoichiometry as an indicator of Histosol drainage in lowland and mountain forest ecosystems

Background:Peatlands form one of the largest carbon pools in the terrestrial ecosystems,representing approximately one-third of the world’s soil carbon.The aim of this study was to evaluate C:N:P stoichiometry as an indicator of changes initialized by dehydration in Histosols of varied origins.Four types of Histosols from lowland and mountain areas were investigated:fibric Histosols,hemic Histosols,sapric Histosols and Histosols drainic.Results:We established the concentration and stoichiometry of carbon,nitrogen and phosphorous in the Histosols,and found marked differences in C:N:P stoichiometry between the different types–especially the dehydrated samples.The mean C:N:P ratio of dehydrated soil was narrower than the C:N:P ratio of soil under the influence of water,which demonstrates that dehydrating Histosols leads to a narrower C:N:P stoichiometry.This is directly related to the intensification of the organic matter mineralisation process and the resulting loss of organic carbon.We recorded a 50%lower carbon stock in the case of Histosols drainic compared to the other types of Histosols.Conclusions:The narrower C:N:P stoichiometry in Histosols drainic is the result of an decrease in the ratio of N and P to the C content.Thus,this study demonstrates that C:N:P stoichiometry is a useful indicator of the changes that occur in Histosols as a result of dehydration.

Molecular Characterization of Bacterial Community Composition in the Rhizosphere of Invasive Plant Species Amur Honeysuckle (<i>Lonicera maackii</i>) in an Urban Wetland Forest

The goal of this research was to determine the effects of the growth of invasive plant Amur Honeysuckle (Lonicera maackii) on the rhizosphere bacterial community composition, and diversity in an urban wetland forest ecosystem. Bacterial communities from the rhizosphere of 5 L. maackii plants and control bulk soils that did not have any L. maackii were investigated at Nina Mason Pulliam EcoLab (NMPE) using a culture-independent pipeline. Bacterial communities were characterized by PCR amplification and cloning 16S rRNA gene fragments following total DNA isolation from the soil samples. Microbial communities associated with both L. maackii rhizosphere and control sites showed high bacterial diversity within each site and taxa unique to individual sites were observed. Phylogenetic analyses revealed 80% of 400 16S rDNA clones were classified as α-, β- and γ-Proteobacteria, Acidobacteria, Actinobacteria, Cytophaga-Flexibacter-Bacteroides (CFB) group, and Verrucomicrobia. Members of the Proteobacteria and Acidobacterium represented 66.5% and 14.5% of the clone library, respectively, whereas the remaining bacterial divisions each comprised less than 7% of the clone library. Twenty-five 16S rDNA clones could not be classified into any known bacterial divisions. Statistical analyses showed significant differences in the presence of L. maackii on the proportions of 16S rDNA clones affiliated with Proteobacteria and Acidobacterium, suggesting bacterial community composition and structure does significantly change in the presence of L. maackii. However, sequence-based community analysis and the corresponding lack of intact microbial cultures limit understanding of the potential influences of enriched microbial taxa on plant hosts and their roles in ecosystem functioning.

Biochar Effectively Reduces Ammonia Volatilization From Nitrogen-Applied Soils in Tea and Bamboo Plantations

Intensive practices in forest soils result in dramatic nitrogen(N)losses,particularly ammonia(NH_(3))volatilization,to adjacent environmental areas.A soil column experiment was conducted to evaluate the effect of bamboo biochar on NH_(3) volatilization from tea garden and bamboo forest soils.The results showed that biochar amendment effectively reduced NH_(3) volatilization from tea garden and bamboo forest soil by 79.2%and 75.5%,respectively.The soil pH values increased by 0.53-0.61 units after biochar application.The NH_(4)^(+)-N and total N of both soils were 13.8-29.7%and 34.0-41.9%higher under the biochar treatments than under the control treatment,respectively.In addition,the soil water contents of the two biochar-amended soils were significantly higher(P<0.05),by 10.7-12.5%,than that of the soils without biochar amendment.Therefore,biochar mitigates NH_(3) volatilization from the tested forest soils,which was due to the increases in soil NH_(4)^(+)-N,total N and water contents after biochar amendment.Our main findings suggest that biochar addition is an effective management option for sustainable forest management.

Effects of soil moisture and temperature on CH_4 oxidation and N_2O emission of forest soil

Soil samples were taken from depth of 0-12cm in the virgin broad- leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L-1 and 200 μL·L-1 CH4 and N2O concentration were supplied for analysis. Laboratory study on CH4 oxidation and N2O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N2O. Air-dried soil sample could not oxidize atmospheric methane, but could produCt N2O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L-1. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N2O emissions within 2 hours. There were curvilinear correlations between N2O emission and temperature (r2=0.706, p <0.05), and between N2O emission andtwater content (r2=0.2968. p <0.05). These suggested temperature and water content were important factors controlling N2O emission. The correlation between CH4 oxidization and temperature was also found while CH4 was supplied 200 μL·L-1 (r2 =0.3573, p<0.05). Temperature was an important f8Ctor controlling CH4 oxidation. However, when 20 μL·L-1 CH4 was supplied, there was no correlation among CH4 oxidization, N2O emission, temperature and water content.

Forest Soil Management: A Mexican Experience

Forests improve the livelihoods and resilience of communities in diverse ways. In particular, soils provide important environmental services for communities in addition to performing many essential ecological functions in forest ecosystems, such as nutrient uptake, organic matter decomposition, water storage, and provision of anchorage for plant growth. The sound management of forest soils, although often disregarded, is a key element of sustainable forest management. From 2002 to 2016 the Forest Soil Conservation and Restoration Sub-Program was designed and implemented by the National Forest Commission (CONAFOR) in Mexico. Forests in Mexico have high biological diversity and are often owned, governed, and managed by communities or, in some cases, community forestry is practiced. Despite the importance of periodic monitoring to ensure that policies are both effective and suitable for diverse conditions and decision making, the policies implemented by this program were not evaluated during its years of operation. Therefore, in the present study, we aimed to identify the deficiencies of this policy as well as opportunities based on a review of the official information available on the Forest Soil Conservation and Restoration Sub-Program of CONAFOR during the 2002-2016 period and interviews with key informants. In addition, we aimed to highlight experiences that may be useful for similar soil conservation policies in tropical forest regions. The identified limitations ranged from conceptual problems such as policy weakness and lack of understanding of local drivers of soil degradation to an overly rigid implementation of soil conservation measures across diverse forest ecosystems and socio-ecological contexts. These deficiencies had several unintended outcomes: perhaps the most relevant was the inability of forest communities to build capacities for soil conservation. Another important limitation was the complete lack of monitoring of the program and its outcomes, which could have prevented its poor results. Finally, a lack of transparency in the distribution and determination of funding was noted. In conclusion, the hierarchical approach of this policy appears to have compromised its long-term efficacy.

Effects of acid rain on forest ecosystem in Southwestern China

The study of effects of acid rain in Southwestern China on forest ecosystems .has been inrestigated since 1984. The results have shown that the ecosystem of Pinus massoniana forest has been damaged severely by acid rain. Comparing the areas where the annual mean pH value is lower than 4.5 with that higher than 4.5, the productivity of the ecosystems decreased 50 percent. Both the percentages of the green leaves and the content of chlorophyll cut down; the acidity of soil increased a bit and the fertility showed the tendency to lower. The microbial population components in surface soil were changed and the total number of soil microbes reduced from 63.5 to 92.6 percent. Besides the direct effects of acid rain, the insect pest, especially, Blastophagus piniperdoz and Monochamus galloprovincialis, seized the opportunity to enter and reproduce in it so as to aggravate the forest dieback of P.massoniana in the areas where the annual average pH value is lower than 4.5.Additionally, the simulation study on the symptoms of main tree species in Southwestern China damaged by acid rain has obtained the results in the resistibility of 30 tree species, which provided a foundation for selecting suitable tree species to cultivate in the polluted areas.

Diversity of soil fungi in dry deciduous forest of Bhadra Wildlife Sanctuary,Western Ghats of southern India

Abstract： We assessed soil fungal diversity in the dry deciduous forest ofa Bhadra Wildlife Sanctuary of the Western Ghats （210.31 m a.s.1.; N 13044＇ and E75°37′）. Soil samples were collected by random mixed sampling during winter （November, 2008）, summer （March, 2009） and monsoon （August, 2009） seasons, and physico-chemical parameters were recorded. During winter, summer, and monsoon seasons, 49, 45 and 49 of fungal species belongs to 20, 18 and 19 of genera were isolated, respectively. Isolated soil fungi were mainly of the Mitosporic fungi, followed by Zygomycotina, Ascomycotina, Oomycotina and Coelomycetes. Indices of diversity, dominance and fisher alpha during winter, summer and monsoon seasons were 3.756, 3.638 and 3.738 （H）, 0.9737, 0.9694 and 0.9726 （I-D） and 18.84, 29.83 and 19.46 （a）, respectively. Spear- man＇s （r） correlation coefficient of fungal population with physicochemical parameters of soils showed significantly positive and negative correlations （p〈0.01） during winter, summer and monsoon seasons. Physico-chemical soil parameters played an important role in the occurrence, diversity, distribution, and relative abundance of fungal species in the tropical dry deciduous forest soil.

Distribution of persistent organic pollutants in aggregate fractions of a temperate forest and semi-rural soil

The fate of persistent organic pollutants (POPs) and their interactions with aggregates of forest soils are not completely understood. Our objectives here were to quantify the distribution of different POPs in water-stable aggregate fractions and to study their influence on soil organic carbon (Corg) content. Soil samples were taken from a forest-site, Gogerddan (G) and a semi-rural site, Hazelrigg (H) in Great Britain, from 0-2 and 2-5?cm and 0-4 and 8-12?cm soil depth, respectively. POPs analyzed were PAHs, PCBs, total DDT, PBDEs and HCB. The bulk soil analysis showed that the concentration of POPs was significantly higher (p?≤?0.05) in forest site G than in semi-rural site H, particularly at the surface soil levels compared to the subsurface soil depths in both sites. Total concentrations of PCBs and PAHs of both sites were positively correlated with Corg contents. POPs concentrations and Corg, Nt contents of forest site G were significantly higher (p?≤?0.05) in water-stable macro aggregates (>0.25, >1, >2?mm) than the micro aggregates (>0.053?mm). The POP concentrations of all aggregate fractions after normalizing to their respective Corg content were increased due higher contamination and strong sorption by Corg. These results showed a strong effect of Corg on the partitioning of organic pollutants to soil aggregate size fractions. The present study affirms the ecological significance of forest soils act as a potential sink of POPs. In summary, our results suggest that aggregate fractions may promote soil C storage and act as a potential POP sink in surface soil without increasing their concentration in the aggregate fraction of subsoil.

Comparison of soil bacterial diversity and community composition between clear-cut logging and control sites in a temperate deciduous broad-leaved forest in Mt. Sambong, South Korea

Deforestation or clear-cut logging affects forest ecosystems,including soil microbial communities.The purpose of this study was to investigate the effects of clearcut logging on the soil bacterial community in a temperate deciduous broad-leaved forest on Mt.Sambong,South Korea.We investigated the physicochemical characteristics and bacterial diversity of the soil in clear-cut logging and control sites.The available phosphorus(AP)level in soil was significantly lower in the clear-cut sites than in the control;however,the other physicochemical properties of soil were similar at the two sites.By examining the bacterial 16S rRNA gene using next-generation sequencing,we found that the number of bacterial taxa at the species and phylum level were similar at the control and clear-cut sites.Consistent with the high resilience of bacterial communities and absence of change in the soil physicochemical properties—with the exception of AP—we found similar levels of bacterial diversity at the two sites.Although most taxa showed similar composition ratios at the control and the clear-cut sites,some taxa such as Deltaproteobacteria,Ktedonobacteriales,Myxocccales,Polyangiaceae,Pedosphaera_f,and Solibacter showed differences after clear-cut logging.We conclude that AP was significantly associated with those bacterial taxa that showed differences in their composition ratios following clear-cut logging.