Characteristics of Climate Change and its Response in the Qinghai-Tibet Plateau during 1971-2010

Climate data during 1971-2010 showed that mo st areas of Qinghai-Tibet Plateau showed warm wet climate change type dominated by temperature and humidity increase.Temperature increase magnitude was the smallest in spring and the largest in winter,and the precipitation increased at the low-altitude area and decreased at high altitude.The warm wet climate change caused Qinghai-Tibet Plateau alpine grassland degradation,reduction of glacier and frozen soil,wetland reduction and other environmental problems.

Soil amendment strategies determining microbial community composition and their assembly processes in a continuously cropped soil

Reductive soil disinfestation(RSD)is an important tool for sustainable agricultural productivity.However,the differences in soil bacterial communities and their community assembly processes among RSD and other treatment strategies(e.g.,biochar and chemical fumigation)are still subject to open questions.In this study,soils subjected to various treatments–un-treated control(CK),chemical soil fumigation with CaCN_(2)(CF),1% biochar(1%B),3% biochar(3%B),and reductive soil disinfestation(RSD)are investigated.Soil samples were collected,incubated,and then used for growth of tomato plants.The Sloan neutral community model indicates that stochastic processes dominate in bacterial community assembly for both biochar and CF amendments.In contrast,this work shows that RSD treatment can have a strong impact on soil bacterial community composition.The relative abundance of Firmicutes increased during unplanted soil incubation,whereas Proteobacteria and Bacteroidetes dominated in the rhizosphere after planting of tomatoes.Normalized stochasticity ratio reveals that deterministic selection played an important role in the bacterial assembly under RSD amendment.We found that RSD amendment yielded lower biomass than that for other treatments after 28 days of tomato growth.Our results suggest that although RSD treatment has great potential to rebuild soil bacterial ecology by shaping bacterial communities and their assembly processes,it is important to monitor and manage soil conditions(e.g.,soil nutrients or physical properties)before planting to ensure plant productivity.

Prevention and Control of Continuous Cropping Obstacle of Watermelon by Reductive Soil Disinfestation (RSD)

This study aimed to explore whether reductive soil disinfestation（RSD） is an effective method of controlling continuous cropping obstacle of watermelon. Samples of watermelon continuous cropping soils were treated by RSD in laboratory tests and pot experiments in August 2015 and from December 10,2016 to April 10,2017. The soil samples for the laboratory test were divided into 16 groups,and each group comprised three parallel samples of 100 g（dry soil weight）. Except for the original and control（CK） samples,the 14 other groups of soil samples were treated with different combinations of 1% or 3% alfalfa powder,1% or 3% ammonia（NH3） water,and 1% or 3% acetic acid. The soil samples were placed inside size-five self-styled plastic bags and incubated in a constant-temperature biochemical incubator at 35°C for 14 days after blending,flooding,and sealing. Seven groups of soil samples were designed for the pot experiments based on the laboratory test results. Each group consisted of 30 parallel samples of 3 kg（dry soil weight）. These samples were incubated outdoors for 4 months after mixing with alfalfa powder and/or NH3 and/or acetic acid according to the experimental design,blending,flooding,and sealing. Watermelon seedlings were planted in the air-dried soil samples from May to July in 2017. The results showed that the p H of the soil samples treated by RSD were elevated except for those samples with acetic acid. In addition,the electrical conductivities of the soil samples treated by RSD were effectively adjusted. The presence of soil-borne pathogenic Fusarium oxysporum f.sp. niveum was significantly suppressed（p 0.05） in soil samples treated by RSD,and the incidence and mortality rate of watermelons planted in these samples were remarkably lower than those planted in the CK and flooded CK soil samples. Therefore,continuous cropping obstacle of watermelon can be controlled by RSD.

Effect of liming on sulfate transformation and sulfur gas emissions in degraded vegetable soil treated by reductive soil disinfestation

Reductive soil disinfestation（RSD）, namely amending organic materials and mulching or flooding to create strong reductive status, has been widely applied to improve degraded soils.However, there is little information available about sulfate（SO4^2-） transformation and sulfur（S）gas emissions during RSD treatment to degraded vegetable soils, in which S is generally accumulated. To investigate the effects of liming on SO4^2-transformation and S gas emissions,two SO4^2--accumulated vegetable soils（denoted as S1 and S2） were treated by RSD, and RSD plus lime, denoted as RSD0 and RSD1, respectively. The results showed that RSD0 treatment reduced soil SO4^2-by 51% and 61% in S1 and S2, respectively. The disappeared SO4^2-was mainly transformed into the undissolved form. During RSD treatment, hydrogen sulfide（H2S）,carbonyl sulfide（COS）, and dimethyl sulfide（DMS） were detected, but the total S gas emission accounted for 〈 0.006% of total S in both soils. Compared to RSD0, lime addition stimulated the conversion of SO42-into undissolved form, reduced soil SO4^2-by 81% in S1 and 84% in S2 and reduced total S gas emissions by 32% in S1 and 57% in S2, respectively. In addition to H2S, COS and DMS, the emissions of carbon disulfide, methyl mercaptan, and dimethyl disulfide were also detected in RSD1 treatment. The results indicated that RSD was an effective method to remove SO4^2-, liming stimulates the conversion of dissolved SO4^2-into undissolved form,probably due to the precipitation with calcium.

Biogeochemical reductive release of soil embedded arsenate around a crater area (Guandu) in northern Taiwan using X-ray absorption near-edge spectroscopy

This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic absorption spectrometry.Total arsenic （As） concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite （As（III）） and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.

Resistance reduction by bionic coupling of the earthworm lubrication function

Based on the biological coupling theory, the resistance reduction characteristic of the surface morphology and surface wettability of the earthworm were studied in this paper. The parameters of surface dorsal pore and corrugation were extracted. According to these parameters, the lubrication mechanism of the earthworm surface was analyzed. The distribution of the pores and surface morphology were designed and the bionic coupling samples were prepared. The positive pressure, lubricant flow rate and advancing velocity were selected as the experiment factors while the soil friction resistance as observed object. According to the obtained data of bionic coupling samples from the testing system of biologic signal for tiny soil adhesion test, the optimal samples from the bionic coupling resistance reduction tests were selected through the range analysis. Compared to the normal ones, the soil resistance of bionic coupling samples was reduced by 76.8%. This is of great significance and offers bright prospects for reducing energy loss in terrain mechanics.

Accelerated anaerobic dechlorination of DDT in slurry with Hydragric Acrisols using citric acid and anthraquinone-2,6-disulfonate(AQDS)

The application of electron donor and electron shuttle substances has a vital influence on electron transfer,thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis（p-chlorophenyl）ethane（DDT） in anaerobic reaction systems.To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate（AQDS） in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide,a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of（1） control,（2） citric acid,（3） AQDS,and（4） citric acid ＋ AQDS.Results showed that DDT residues decreased by 78.93%-92.11% of the initial quantities after 20 days of incubation,and 1,1-dichloro-2,2-bis（4-chlorophenyl）-ethane（DDD） was the dominant metabolite.The application of citric acid accelerated DDT dechlorination slightly in the first 8 days,while the methanogenesis rate increased quickly,and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased.The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe（III） oxides to generate Fe（II）,which was an efficient electron donor,thus enhancing the reductive dechlorination rate of DDT.The addition of citric acid ＋ AQDS was most efficient in stimulating DDT dechlorination,but no significant interaction between citric acid and AQDS on DDT dechlorination was observed.The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites.