Field Ecosystem Research Articles

Trophic Niche Differences in Arachnid Predators Between Field and Forest Ecosystems

ABSTRACT: Arachnids are important predators in arthropod assemblages that occur from early successional old fields to mature forests. As generalist predators, they may occupy varying trophic niches in different environments that have different prey available. Given that trophic niche can be quantified by the enrichment of 15N in an organism, we tested the null hypothesis that the trophic niche is invariant between old fields and forests in three groups of arachnids: cursorial and web weaving spiders (Araneae), and harvestmen (Opiliones), by comparing the stable isotope ratios of nitrogen (δ15N) in specimens of each group collected from field and forest. Cursorial spiders fed at the highest trophic level in both habitats, and likely consumed other predators as well as herbivores in the field. Web weavers showed slightly higher δ15N in the field than in the forest. Harvestmen and cursorial spiders had significantly lower δ15N in the forest, indicating a trophic shift downward during later succession when th...

Distribution and implication of alien invasive plant species of Assam: a review

The vegetational landscape of Assam is a collage of grassland, agriculture field, wetland, wasteland, and forest ecosystems. Like many other parts of the country, this region is also infested with alien intruders which not only interfere with the growth and production of food crops but also exercise adverse effects on the biodiversity of native species. The present study attempts to catalogue the invasive alien species of the Assam state especially with reference to their habit, taxonomic position, and nativity. A total of 25 invasive alien species under 25 genera, belonging to 14 families have been recorded. Among these, majority of them belongs to dicotyledons families and very few to monocotyledons families. The analysis of invasive species reveals that 5 species have been introduced intentionally, while the remaining species established unintentionally through trade. In terms of nativity, amongst 13 geographic regions, the majority of invasive plants reported from tropical American continent (73%) and have been found to be invasive aliens as evident from their center of origin, past history, nature of aggregation, and invasion observed under field conditions. While in life form analysis, the herbs (18 species) are dominant, followed by trees (3 species), shrub & under shrub (2 species each), Grass (1 species). Most of the invasive species are perennial habit (68%). Therefore, it is very important to make an effective implication management of invasive species, knowledge about their diversity, life form, habitat, uses, is essential.

Populations of Rice Grain Bug, Paraeuscosmetus pallicomis, (Hemiptera: Lygaeidae) in Weed-free Paddy Field, Weedy Paddy Field and Paddy Dykes.

Research on the populations of rice grain bug Paraeuscosmetus pallicomis Dallas (Hemiptera: Lygaeidae) in paddy field ecosystems was performed with the aim to determine the populations of rice grain bug in weed-free paddy field, weedy paddy field, and paddy dykes. Experiment was carried out in the village of Paccellekang in the district of Patallasang of Gowa Regency in South Sulawesi, Indonesia. Observations were performed during the milky grain stage (85 days after planting), the mature grain stage (105 days after planting), and one day after harvest (115 days after transplanting). Results showed that 85 days after the transplanting, the populations of rice grain bug was significantly higher in the weedy paddy field compared to weed-free field and paddy dykes with total numbers of 1.75, 3.53, and 0.31 insects per 2 hills, respectively. Similarly, 105 days after the transplanting, 2.53, 5.53, and 0.11 insects per hill, respectively. However, one day after the harvest (115 days after transplanting) the number of insects in weed-free field decreased, while in the dykes increased, and the weedy plot still had the highest number of insects per 2 hills. Our results suggested that weeds played an important role in regulating the bug population by providing alternative shelter and foods for the insect.

长期施肥对双季稻田甲烷排放和关键功能微生物的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 长期施肥对双季稻田甲烷排放和关键功能微生物的影响 DOI: 10.5846/stxb201609041803 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31571591，31201178）；国家公益性行业（农业）科研专项（201503123） Effects of long-term fertilizer treatments on CH4 fluxes and key functional microorganisms in a double-cropping paddy field Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究不同施肥措施对双季稻田甲烷（CH4）排放特征的影响及其微生物学机理，对合理利用及评价不同施肥模式对水稻生长的影响具有重要意义。以长期施肥定位试验田为平台，采用静态箱-气相色谱法对施用化肥（MF：mineral fertilizer alone）、秸秆还田配施化肥（RF：rice residues plus mineral fertilizer）、30%有机肥配施70%化肥（LOM：30% organic matter plus 70% mineral fertilizer）、60%有机肥配施40%化肥（HOM：60% organic matter plus 40% mineral fertilizer）和无肥（CK：without fertilizer）条件下双季稻田CH4排放及其微生物学机理进行了分析。结果表明，早稻和晚稻生长期，不同施肥处理稻田CH4排放通量均显著高于CK，表现为HOM > LOM > RF > MF > CK。各处理间CH4总排放量差异达显著水平，其大小顺序与排放通量趋势一致，以HOM处理为最高，比CK处理增加105.56%，其次是LOM和RF处理，分别比CK处理增加72.97%和54.17%。关键功能土壤微生物测定结果表明，早稻和晚稻各个主要生育时期，各处理稻田土壤产甲烷古菌的数量变化范围为（3.18-81.07）×103 cfu/g，土壤甲烷氧化细菌的数量变化范围为（24.82-379.72）×103 cfu/g。稻田土壤产甲烷古菌和甲烷氧化细菌数量大小顺序为HOM > LOM > RF > MF > CK，各施肥处理均显著高于CK；HOM、LOM、RF处理显著高于MF、CK处理。双季稻田CH4排放与稻田土壤产甲烷古菌、甲烷氧化细菌数量变化关系密切。采用有机无机肥配施促进了双季稻田生态系统CH4的排放和关键功能微生物的数量。 Abstract:Methane (CH4) fluxes and their key functional microorganisms in a double-cropping paddy field are affected by long-term fertilizer treatment; thus, it was important to utilize and evaluate different fertilization regimes on rice growth. A manual static chamber-gas chromatography (GC) technique was used to verify the effects of different fertilizer treatments, which included mineral fertilizer alone (MF), rice residues plus mineral fertilizer (RF), 30% organic matter plus 70% mineral fertilizer (LOM), 60% organic matter plus 40% mineral fertilizer (HOM), and a control without fertilizer (CK), on CH4 emissions from double-cropping paddy fields in subtropical regions of China and on the microbial mechanisms driving them. The results showed that the flux of CH4 from the HOM, LOM, RF, and MF treatments was higher than that of the CK treatment, and it varied with different fertilizer treatments in the following order:HOM > LOM > RF > MF > CK. Further, CH4 emissions were significantly greater during the entire growth period for early and late rice in the HOM, LOM, RF, and MF treatments than in the CK treatment (P < 0.05). CH4 emissions from paddy fields in the HOM, LOM, and RF treatments increased by 105.56%, 72.97%, and 54.17%, respectively, compared with the CK treatment. At the main growth stages of early and late rice, the abundance of methanogens under the different fertilizer treatments ranged from 3.18×103 cfu/g to 81.07×103 cfu/g, while that of methanotrophs ranged from 24.82×103 cfu/g to 379.72×103 cfu/g. The results indicated that the abundance of the methanogens and methanotrophs were significantly greater in the HOM, LOM, RF, and MF treatments at the main growth stages of early and late rice than they were in the CK treatment. Additionally, the abundance of methanogens and methanotrophs varied under the different fertilizer treatments in the following order:HOM > LOM > RF > MF > CK. Moreover, the abundance of methanogens and methanotrophs was significantly greater in the HOM, LOM, and RF treatments at the main growth stages than they were in the MF or CK treatments. CH4 emissions were significantly correlated with the abundance of methanogens and methanotrophs during the whole growth period. Our results clearly demonstrated that CH4 emissions from paddy fields and the abundance of key functional microorganism were promoted by the application of inorganic fertilizer combined with organic manure practices in a double paddy field ecosystem. 参考文献 相似文献 引证文献

Determination of Trophic Structure in Selected Freshwater Ecosystems by using Stable Isotope Analysis.

Stable isotope analysis has been used extensively to establish trophic relationships in many ecosystems. Present study utilised stable isotope signatures of carbon and nitrogen to identify trophic structure of aquatic food web in river and rice field ecosystems in Perak, northern peninsular Malaysia. The mean δ13C values of all producers ranged from −35.29 ± 0.21 to −26.00 ± 0.050‰. The greatest δ15N values noted was in zenarchopterid fish with 9.68 ± 0.020‰. The δ15N values of aquatic insects ranged between 2.59 ± 0.107 in Elmidae (Coleoptera) and 8.11 ± 0.022‰ in Nepidae (Hemiptera). Correspondingly, with all the δ13C and δ15N values recorded, it can be deduced that there are four trophic levels existed in the freshwater ecosystems which started with the producer (plants), followed by primary consumer (aquatic insects and non-predatory fish), secondary consumer (invertebrate predators) and lastly tertiary consumer (vertebrate predators).

我国稻田系统温室气体排放及减排对策分析

近年来温室气体排放增加引起的全球气候变暖备受人们的广泛关注，缓减温室气体排放势在必行。CH4和N2O是大气中两种重要的温室气体，在全球变暖中具有非常重要的作用。稻田系统是重要的温室气体排放源，本文从品种选择、水分管理、肥料施用、耕作制度以及秸秆还田和综合利用等几个方面总结了可以减缓我国稻田温室气体排放的一些措施，为我国低碳农业的可持续发展提供一定的技术支撑，为我国温室气体减排和缓解全球气候变暖作出积极的贡献。 In recent years, the issue of increase in greenhouse gas emissions and greenhouse effect induced by them has already aroused people’s great attention. Reducing greenhouse gas emission has become an urgent problem, which should be solved as soon as possible. CH4 and N2O are two major greenhouse gases, which play very significant role in global warming. Paddy field ecosystem is the important greenhouse gases (CH4 and N2O) emission sources. For the purpose of providing technological support for the sustainable development of low carbon agriculture, and making a positive contribution in reducing China’s greenhouse gas emission and relieving global warming, several controlling methods for reducing greenhouse gas emissions in Chinese paddy field ecosystem were elaborated from the following aspects: varieties selection, irrigation, fertilizer application, cropping system, straw amendments and straw complex utilization.

Rice Intensive Cropping and Balanced Cropping in the Mekong Delta, Vietnam — Economic and Ecological Considerations

Rice intensification in Vietnam relies on the construction of high dykes in the Mekong Delta floodplain to prevent flood waters from entering fields during the flood season. This enables three rice crops to be grown annually instead of two. On the floodplain, two rice crops can be described as “balanced cropping” since it has a long fallow period, which conforms to good agricultural practices, and also takes advantage of the flood's benefits. For example, it integrates the natural fish, other aquatic animals, and flood sediments during the flood season as part of the rice field ecosystem. This study surveys agriculture practices among “three crop” and “two crop” farmers on the floodplain. It is argued that planting three crops (“intensive cropping”) cannot provide a sustainable alternative to balanced cropping, either from an economic or an ecological viewpoint. Study findings emphasise the need to recognise the ecological value of balanced cropping systems for an efficient and environmentally sound production of food. In connection with this, it is suggested a case for limiting further dyke heightening since rice intensification, which is the aim of this large-scale water control, does not make economic sense.

Effects of a mud snail Cipangopaludina chinensis laeta (Architaenioglossa: Viviparidae) on the abundance of terrestrial arthropods through rice plant development in a paddy field

The effects of a mud snail, Cipangopaludina chinensis laeta (Martens) (Architaenioglossa: Viviparidae), on terrestrial arthropods through rice plant development in a paddy field were investigated in 2013 and 2014 by a field experiment. There were no significant differences between treatments in the abundance of aquatic organisms, which comprised several functional feeding groups in both years. The presence of mud snails did not significantly affect plant height and soil plant analysis development values, either, except in June 2014, when tiller number and biomass of the rice plants tended to be larger in plots with snails versus those without. Significantly higher abundances of terrestrial organisms, including phytophagous pest insects and other insects, but not natural enemies of the pest insects, occurred in plots with snails. As shown by principal component analysis, the community structure of the terrestrial organisms was significantly different between the two treatments in both years. The results of this study indicate that mud snails play an important role in the paddy field ecosystem, in which they influence the biomass production of rice plants and the abundance of organisms in terrestrial ecosystems through direct and indirect interactions at different trophic levels.

Weather dependent dynamics of the herbicides florasulam, carfentrazone-ethyl, fluroxypyr-meptyl and fluroxypyr in wheat fields through field studies and computational simulation

A dynamic model of dynamiCROP was applied to study environmental fate and behavior of four herbicides in wheat including florasulam, carfentrazone-ethyl, fluroxypyr-meptyl, and fluroxypyr. Meantime, their residue in wheat and dissipation half-lives in plant determined by field trials using QuEChERS liquid chromatography tandem mass spectrometry were used to verify modelling results. The combination of experimental verification and modelling prediction deciphered the fate of four pesticides in wheat field ecosystem. Besides, temperature difference of 3 °C only resulted in lower than 15% half-life difference. By quantifying the contribution of temperature, the predominant role of rain on pesticide dissipation was highlighted for the first time, namely higher precipitation leaded to faster degradation and vice versa.

Exploration of Amendments and Agronomic Measures on the Remediation of Methylmercury-Polluted Rice in a Mercury Mining Area

An in situ pot method was conducted using 2-year experiments to address the issue of methylmercury (MeHg) pollution in a paddy field ecosystem that was influenced by mercury (Hg) mining activities. The reduction effect of adopted amendments and agronomic measures on MeHg-polluted rice was investigated, and positive results had been achieved in our experiments. In the first-year experiment, the reductions of 27.86–71.61 and 29.48–64.96 % (with the averages of 51.55 and 49.41 %) for rice MeHg under high and low pollution levels were observed, respectively. In our second year experiment, all selected amendments and agronomic measures still showed a stable and significant reduction effect as we found in the first year (p < 0.05), with a reduction rate ranging from 42.21 to 75.25 %. Overall, significant reduction effect was validated through the use of calcium magnesium phosphate fertilizer, farmyard manure, activated clay, ground phosphate rock, and maifanite in the 2-year experiments. Among those five treatments, activated clay showed the most stable performance, followed by ground phosphate rock and then calcium magnesium phosphate fertilizer. Moreover, the changes of irrigation water sources and fertilizer patterns had great impact on the enrichment ability of MeHg in rice. Finally, our studies also showed that the pros and cons of reduction effect by amendments or agronomic measures based on the pollutant patterns: MeHg concentrations in rice were generally reduced to a greater degree than total Hg (THg).

Agriocnemis femina (Odonata: Coenagrionidae) and its significance in environmental parameters of rice pests in northern Sumatra-Indonesia

The pattern movement and age structure influence of rice cultivation phases on A. femina aquatic organisms was investigated in the Manik Rambung rice field (MRRF) ecosystem in North Sumatra. A. femina collections of a buterfly net samples were collected in five cultivation phases (fallow, plough, transplantingyoung, tiller, mature atau preharvest). Agriocnemis femina adult (Odonata:Zygoptera), one of the rice pest predators in the adult stage, was dependent on its interactions with rice cultivation phases. There were three age classes of A. femina; teneral, juvenile and mature with sex ratio male and female is 1.7:1. It was important in regulating Agriocnemis femina population in MRRF which determined its successful emergence to a predatory adult. Rice cultivation managements that focus on enhancing the population of Agriocnemis femina would contribute to more effective biological control of rice pests.

Residue and dissipation of zinc thiazole in tobacco field ecosystem

ABSTRACTA high-performance liquid chromatography with ultraviolet (HPLC-UV) detection method after derivatisation was developed for the first time for the novel fungicide zinc thiazole residue in tobacco samples. Field trials in two different locations were conducted to investigate the dissipation and residue of zinc thiazole in tobacco leaves and soil. The average recoveries of zinc thiazole were in the range of 82.5%–93.9% with relative standard deviations (RSDs) of 1.2%–9.1%. The zinc thiazole showed a rapid dissipation rate in fresh tobacco leaves with the half-lives of 1.1–1.6 days. The terminal residues of zinc thiazole in cured tobacco leaves and soil were 2.8–28.0 mg kg−1and <0.05 mg kg−1, respectively. The results could be used to establish the maximum residue limits (MRLs) and provide guidance for the scientific use of zinc thiazole in agriculture.

Keanekaragaman Serangga Sebagai Pakan Alami Katak Tegalan (Fejervarya Limnocharis, Gravenhorst) pada Ekosistem Sawah di Desa Panggungharjo, Kecamatan Sewon, Kabupaten Bantul

Paddy field was a dynamic and biodiversity rich ecosystems. Insect diversity in paddy field ecosystem was infected by paddy plant growth stages. Grass frog (Fejervarya limnocharis) ate insects as their natural prey. Insect population dynamics during vegetative, generative and reproductive stage of paddy plants infected F. limnocharis natural prey. This research aims were to study insect diversity and F. limnocharis insect prey diversity of vegetative, reproductive and generative paddy plant growth stages at Panggungharjo village, Sewon, Bantul. Insect sampling was conducted by direct survey method while F. limnocharis collection conducted by Visual Encounter Survey (VES) method. Ninety eight insect species from 51 different families and nine orders of insect were found. The orders were Coleoptera, Diptera, Hymenoptera, Odonata, Orthoptera, Dictyoptera, Dermaptera, Hemiptera and Lepidoptera. Stomachs analysis indicated F. limnocharis ate nine insect orders. The orders were Coleoptera, Diptera, Hymenoptera, Orthoptera, Dictyoptera, Dermaptera, Hemiptera, Lepidoptera and Isoptera. Most commonly insect prey in vegetative, reproductive and generative phase paddy growth stage were the members of the Order Coleoptera, Family Acrididae (Orthoptera) and Family Formicidae (Hymenoptera) respectively. This study concluded F. limnocharis main natural prey was the easily found and easily perceived insects.

Dissipation and Residues of Dichlorprop-P and Bentazone in Wheat-Field Ecosystem.

Dichlorprop-P and bentazone have been widely used in the prevention and control of weeds in wheat field ecosystems. There is a concern that pesticide residues and metabolites remain on or in the wheat. Thus, the study of the determination and monitoring of their residues in wheat has important significance. A rapid, simple and reliable QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was modified, developed and validated for the determination of dichlorprop-P, bentazone and its metabolites (6-hydroxy-bentazone and 8-hydroxy-bentazone) in wheat (wheat plants, wheat straw and grains of wheat) using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The average recoveries of this method ranged from 72.9% to 108.7%, and the limits of quantification (LOQs) were 2.5–12 μg/kg. The dissipation and final residue of four compounds in three provinces (Shandong, Jiangsu and Heilongjiang) in China were studied. The trial results showed that the half-lives of dichlorprop-P and bentazone were 1.9–2.5 days and 0.5–2.4 days in wheat plants, respectively. The terminal residues in grains of wheat and wheat straw at harvest were all much below the maximum residue limit (MRL) of 0.2 mg/kg for dichlorprop-P and 0.1 mg/kg for bentazone established by the European Union (EU, Regulation No. 396/2005).

Vegetation damage in the vicinity of an aluminum smelter in Brazil

A primary aluminum smelter, which is responsible for releasing fluoride and other pollutants to atmosphere, is located at the vicinities of rocky field ecosystem in Brazil. We aimed to evaluate the biological effects of the smelter emissions using Spondias dulcis as a bioindicator organism. Evaluations of rainwater quality, atmospheric oxidants and toxicity visual symptomatology were performed in 4 different sites. We also collected leaflets with and without visual toxicity symptoms for anatomical studies under light and scanning electron microscopes, histochemistry, X-ray microanalysis, and fluoride quantification. The fluoride detected on leaves was present in plants at all studied sites, principally at Site 1 (park entrance) and less detected at Site 3 (forest area). However, the fluoride quantity was not the main cause of damage, but the large amount of oxidants which was detected at the atmosphere. This amount of oxidants was increased with the distance from the emission source. It was noticed two types of visual symptoms on the leaflets: a darkening at the adaxial face and a wide brownish necrosis. The anatomical studies showed three damage patterns: superficial necrosis, reaching just the palisade and spongy parenchyma, deep necrosis, reaching the entire mesophyll and a punctual necrosis perceived only at the central veins. With scanning electron microscopy it was detected a turgor loss and a flattening of the cell's external periclinal wall. In the areas where the damage was more noticeable, there was an erosion of the epicuticular wax that lead to delayering, resulting on the epidermis rupture and internal tissue exposure. S. dulcis showed visual symptoms after few days of exposure, which culminated in structural alterations, thus indicating that these pollutants are impacting this important vegetation type from a rocky field ecosystem.

Residues of carbosulfan and its metabolites carbofuran and 3-hydroxy carbofuran in rice field ecosystem in China

ABSTRACTThe fate of carbosulfan (seed treatment dry powder) was studied in rice field ecosystem, and a simple and reliable analytical method was developed for determination of carbosulfan, carbofuran, and 3-hydroxyl carbofuran in brown rice, rice straw, paddy water, and soil. The target compounds were extracted using acetonitrile or dichloromethane, cleaned up on acidic alumina or florisil solid phase extraction (SPE) cartridge, and analyzed by gas chromatography. The average recoveries of carbosulfan, carbofuran and 3-hydroxy carbofuran in brown rice, rice straw, paddy water, and soil ranged from 72.71% to 105.07%, with relative standard deviations of 2.00–8.80%. The limits of quantitation (LOQs) of carbosulfan, carbofuran and 3-hydroxy carbofuran in the samples (brown rice, rice straw, paddy water and soil) were 0.011, 0.0091, 0.014, 0.010 mg kg−1, 0.016, 0.019, 0.025, 0.013 mg kg−1, and 0.031, 0.039, 0.035, 0.036 mg kg−1, respectively. The trials results showed that the half-lives of carbosulfan, carbofuran and 3-hydroxy carbofuran in rice straw were 4.0, 2.6 days, 3.9, 6.0 days, and 5.8, 7.0 days in Zhejiang and Hunan, respectively. Carbosulfan, carbofuran and 3-hydroxy carbofuran were detected in soils. Carbosulfan and 3-hydroxy carbofuran were almost undetectable in paddy water. Carbofuran was detected in paddy water. The final residues of carbosulfan, carbofuran and 3-hydroxy carbofuran in brown rice were lower than 0.05 mg kg−1, which were lower than 0.5 mg kg−1 (MRL of carbosulfan) or 0.1 mg kg−1 (MRL of carbofuran). Therefore, a dosage of 420 g active ingredient per 100 kg seed was recommended, which could be considered as safe to human beings and animals. These would contribute to provide the scientific basis of using this insecticide.

Comparative life history characteristics of the mite predator Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) on mite and pollen diets

ABSTRACTThe food diversification strategy that can offer suitable nutrients as a diet for the natural enemies may possibly help to decrease pest populations by boosting the efficiency of predators. Therefore, my objective was to evaluate the effects of plant and animal diets on biological parameters of the phytoseiid mite Neoseiulus cucumeris (Oudemans). This predator that is a natural enemy of mites was reared on plant pollens (maize (Zea mays L.), sweet pepper (Capsicum annuum L.), mungbean (Vigna radiata L.), cucumber (Cucumis sativus L.), tomato (Lycopersicon esculentum Mill.), and rose (Rosa multiflora Thunb.), offered alone, and in combination with the prey mite Tyrophagus putrescentiae (Schrank). Results showed that N. cucumeris fed, developed and reproduced better when it was provided with plant and animal diets together, compared to pollens offered alone. The predator showed the most efficient capability for completion of life parameters (development, survival, fecundity, oviposition, longevity and instantaneous rate of increase) with maize and mungbean ingested pollens in combination with T. putrescentiae. The least competency was observed on cucumber and rose pollens used separately. The lowest developmental time of the predator from neonate larva to adult emergence, the highest immature survivorship, higher fecundity, long oviposition period, and the highest adult female's life span were observed when offered maize pollens along with T. putrescentiae compared to other treatments. Accordingly, the instantaneous rate of population increase (ri) day−1 was surpassed by N. cucumeris for the combination of pollen and T. putrescentiae diets than pollens utilized alone. It is determined that N. cucumeris can reproduce and develop more successfully on a food complex consisting of pollen and animal diets than any single diet. These findings reveal that pollen can be used by N. cucumeris as a suitable alternative food in periods when prey in the field is sparse or absent. Moreover, such propensity of predators to feed on food from plant origin increases their survival during periods when prey is locally scarce, but natural enemies might occur at the expense of an ability to utilize food as efficiently as specialized predators to boost the management strategies of pest species in field's ecosystem.

Determination of Carbendazim and Diethofencarb in Cotton and Soil by High-Performance Liquid Chromatography

ABSTRACTA simple and reliable method was developed to determine carbendazim and diethofencarb in cotton, cotton seeds, and soil. The decomposition of carbendazim and diethofencarb in the cotton field ecosystem was also studied. The analytes were extracted and quantified by high-performance liquid chromatography. The limits of detection were 0.1 ng for carbendazim and diethofencarb. The limits of quantification of carbendazim and diethofencarb were 0.1 mg kg−1 in cotton, 0.1 mg kg−1 in cotton seeds, and 0.02 mg kg−1 in soil. The average recoveries of cotton, cotton seed, and soil were measured at three fortified concentrations and were in the range of 77.5–103.9% for carbendazim and 80.9–104.6% for diethofencarb. The relative standard deviations were less than 9.0% for both pesticides. In field experiments, the half-lives of carbendazim and diethofencarb were in the range of 2.3–9.1 days and 2.3–8.9 days in cotton at two locations in China. At harvest, cotton seeds contained carbendazim and diethofencarb well below the maximum residue limit of the Japanese “Positive List System” (3 mg kg−1) following the recommended dosage with measurement 10 and 20 days following the final application.

The Diversity And Abundance Of Leafaud Planthopper (Auchenorrhyncha: Hemiptera) Along With Weeds In Rice Field Ecosystem In South Rantau Of Labuhan Batu Regency

The aim of this research is to find out the diversity, abundance, and dominance of leafaud planthopper (Auchenorrhyncha: Hemiptera) along with the types of weeds grow in rice field ecosystem in South Rantau of Labuhan Batu regency. This research was conducted by using purposive random sampling by using insect net. The collection of hopper was done by swinging the insect net for 50 times that took place in north, south, middle, east and south so that the amount of the sampling was 250 swings. The result of this research showed that there were 6 types of rice pests in vegetation period until stublade field in south Rantau of Labuhan Batu regency. They were : Nilaparvata lugens, Nephotettix sp, Cofana spectra, Recilia dorsalis, Thaia sp, Cicadulina bipunctata. The highest abundance was found in Nilaparvata lugens with 407 individuals, Nephotettix sp with 32 individuals, Cofana spectra with 38 individuals, Recilia dorsalis with 26 individuals, Thaia sp with 19 individuals, and Cicadulina bipunctata with only 1 individual, with low diversity index, it was 0,1075. While the weeds found in south Rantau of Labuhan Batu regency were 5 types, they were Cyperus iria ,Cyperus rotundus,Papalum distichum, Alternanthera philoxeroides, Cyperus pilosus. The highest density was found in Cyperus iria weed, with total 25%, whilw the lowest density was found in Papalum distichum with total only 10%. The highest presence frequency was found in Cyperus iria, Cyperus rotundus, Papalum distichum, Alternanthera philoxeroides with total 20%, while the lowest presence frequency was found in Cyperus pilosus with total 16%. The highest dominance was found in Cyperus rotundus with total 23.34%, while the lowest dominance was found in Cyperus pilosus with total 15.83%, and the highest important value index was found in Cyperus rotundus with total 64.24%, while the lowest important value index was found in Papalum distichum with total 52.69%. Keywords : Diversity, abundance, dominance, leafaud planthopper

Simultaneous enantioselective determination of phenylpyrazole insecticide flufiprole and its chiral metabolite in paddy field ecosystem by ultra-high performance liquid chromatography/tandem mass spectrometry

A novel and sensitive ultra-high performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous enantioselective determination of flufiprole and its hydrolysis metabolite in paddy field ecosystem. The separation and determination were performed using reversed-phase chromatography on a novel cellulose chiral stationary phase, a Lux Cellulose-4 (150mm×2.0mm) column, under isocratic conditions at 0.25mL/min flow rate. The effects of other four different polysaccharide-based chiral stationary phases (CSPs) on the separation and simultaneous enantioseparation of the two target compounds were also evaluated. The elution orders of the eluting enantiomers were identified by an optical rotation detector. Modified QuEChERS (acronym for Quick, Easy, Cheap, Effective, Rugged and Safe) method and solid-phase extraction (SPE) were used for the enrichment and cleanup of paddy water, rice straw, brown rice and paddy soil samples, respectively. Parameters including the matrix effect, linearity, precision, accuracy and stability were evaluated. Under the optimal conditions, the mean recoveries for all enantiomers from the above four sample matrix were ranged from 83.6% to 107%, with relative standard deviations (RSD) in the range of 1.0–5.8%. Coefficients of determination R2≥0.998 were achieved for each enantiomer in paddy water, rice straw, brown rice and paddy soil matrix calibration curves within the range of 5–500μg/kg. The limits of quantification (LOQ) for all stereoisomers in the above four matrices were all below 2.0μg/kg. The methodology was successfully applied for simultaneously enantioselective analysis of flufiprole enantiomers and their chiral metabolite in the real samples, indicating its efficacy in investigating the environmental stereochemistry of flufiprole in paddy field ecosystem.