Field Ecosystem Research Articles

Biodiversity Conservation in Rice Paddies in China: Toward Ecological Sustainability

Rice paddies are artificial wetlands that supply people with food and provide wildlife with habitats, breeding areas, shelters, feeding grounds and other services, and rice paddies play an important part in agricultural ecological systems. However, modern agricultural practices with large-scale intensive farming have significantly accelerated the homogenization of the paddy field ecosystem. Modern agriculture mostly relies on chemically-driven modern varieties and irrigation to ensure high production, resulting in the deterioration and imbalance of the ecosystem. Consequently, outbreaks of diseases, insects and weeds have become more frequent in paddy fields. This paper describes the current situation of rice paddy biodiversity in China and analyzes the community characteristics of arthropods and weedy plants. Meanwhile, we discuss how biodiversity was affected by modern agriculture changes, which have brought about a mounting crisis threatening to animals and plants once common in rice paddies. Measures should be focused to firstly preventing further deterioration and, then, also, promoting restoration processes. Ecological sustainability can be achieved by restoring paddy field biodiversity through protecting the ecological environment surrounding the paddy fields, improving paddy cropping patterns, growing rice with less agricultural chemicals and chemical fertilizers, constructing paddy systems with animals and plants and promoting ecological education and public awareness.

Dissipation of trinexapac-ethyl and its metabolite in wheat field ecosystems and microbial degradation in soil

To investigate the dissipation rate of trinexapac-ethyl and trinexapac in wheat ecosystem, field and microbial degradation experiments were designed and conducted. A simple and time-efficient analytical method for the determination of trinexapac-ethyl and trinexapac in wheat kernels, plants, straw and soil, using high-performance liquid chromatography–tandem mass spectroscopy (HPLC–MS/MS) was developed. The mean recoveries of trinexapac-ethyl and trinexapac in four matrices at three spiking levels ranged from 72.0% to 108.2%, and the relative standard deviation (RSD) ranged from 2.1% to 11.0%. In supervised field trials, the half-lives of trinexapac-ethyl in the plants were 0.93 and 2.36 d in Shandong and Tianjin, respectively; and those of trinexapac in soil and plants were 1.66 and 1.45 d in Shandong and 2.32 and 1.74 d in Tianjin. In microbial degradation experiment, the results show that the soil microbial communities have effects on their dissipation in the time scale employed.

Study on Denitrification Intensity in Rice Rhizosphere Soil under Water Management Model

A typical rice field ecosystem as the research object, using the indoor pot experiment to study the three kinds of water driven (shallow layer of continuous irrigation (C), alternating wet and dry (J), and water control mode (G)) on the effect of rice rhizosphere soil denitrification intensity. Effect of changes in soil moisture caused by the three different irrigation patterns on different growth stages of rice on rhizosphere denitrification was comparatively analyzed,referring to the rhizosphere denitrification capacity during different rice growth stage.The results showed that: soil denitrification intensity with different water managements changed significantly, showing C>J>G. And with the growth of plants, under three different water managements, denitrification intensity showed a downward trend. Mature reached to a minimum. All have to be higher than control groups.

Persistence behaviour of deltamethrin on tea and its transfer from processed tea to infusion

The dynamics and residues of deltamethrin in a tea grown in an open field ecosystem were investigated. The quantification was performed using gas chromatography–electron capture detection (GC–ECD) and confirmed by gas chromatograph–mass spectrometry (GC–MS) in selective ion monitoring (SIM) mode. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 87% to 101% with relative standard deviations (RSD) ranging of 0.7–7.1%. The residues of deltamethrin were found to dissipate following first order kinetics with half-life ranging between 3.04 and 3.54d for two different rates of foliar application. The deltamethrin residues are present in the processed tea are not transferred into the tea infusion during the infusion process, since their water solubility is extremely low. These results can be utilized in formulating the spray schedule and safety evaluation on deltamethrin tea crop.

Residues of the fungicide epoxiconazole in rice and paddy in the Chinese field ecosystem

Epoxiconazole is extensively used as fungicide in cereals, grapes and other crops worldwide. Rice is one of the world's most important food crops. Many people who depend on rice for their food live in Asia. A method employing liquid chromatography-tandem mass spectrometry was developed for determination of epoxiconazole in brown rice, straw, rice hull, paddy water and soils. Epoxiconazole residues in rice hull, brown rice, straw and soil were also determined. The limit of quantitation was set at 0.01 mg kg(-1) for the matrices studied. Epoxiconazole degradation in straw, paddy water and soil was studied. The epoxiconazole residues in brown rice, straw, hull and paddy soil were determined. Concurrent recoveries were between 89.2 and 104.1%, with relative standard deviations ranging from 4.6 to 14.4% at three fortification levels between 0.01 and 5.0 mg kg(-1). The half-lives in straw, paddy water and soils were found to be 4.7-5.9, 2.9-6.0 and 2.9-6.4 days respectively. The maximum residues in brown rice, straw, hull and paddy soil samples were 0.18, 2.47, 2.54 and 0.09 mg kg(-1) respectively. Compared with the maximum residue levels (MRLs) for epoxiconazole in rice that have been set by the European Union (0.1 mg kg(-1)) and by China (0.5 mg kg(-1)), the epoxiconazole residue on rice at an application rate of 112.5 g AI ha(-1) with two applications at an interval of 7 days, and with a 28 day preharvest interval (PHI), is below the MRL, and thus the use of epoxiconazole is considered to be safe. Epoxiconazole should be applied correctly, according to good agricultural practice, using only the recommended amounts, frequencies and appropriate PHI.

Residue and dissipation kinetics of thiamethoxam in a vegetable-field ecosystem using QuEChERS methodology combined with HPLC–DAD

The dissipation kinetics and residual levels of thiamethoxam in potato and soil under field ecosystem were determined using a QuEChERS method with HPLC–DAD. At fortification levels of 0.05, 0.1, 0.25, 0.5, 1.0 and 5.0mgkg−1, it was shown recovery was 99.4% (95.3–103.5%) for potato tubers, and 88.5% (86–91%) for soil with coefficient variation of the method (CV%) was less than 4% in potato tubers, and in soil less than 11%. For repeatability ranged from 1.27% to 4.77%. The LOD and LOQ were estimated to be 0.02 and 0.06mgkg−1, respectively. The half-lives were 2.92 and 1.4days, respectively. The terminal residues of thiamethoxam were below the maximum residue limit (MRL 0.2mgkg−1) after 6days, which considered to be safe for human beings. These results contribute to establishing the scientific basis of the dosage of thiamethoxam for use in vegetable-field ecosystems.

Carbon Storage Dynamics in Alfalfa (Medicago sativa) Fields in the Hilly‐Gully Region of the Loess Plateau, China

Alfalfa (Medicago sativa) has been widely employed in the dryland region of the Loess Plateau, China to improve soil and water conservation and to develop livestock production. Our objective was to study the dynamics of plant and soil organic carbon (SOC) pools following the conversion of sloping farmland to alfalfa fields over a period of 30 years. The succession gradient is composed of seven differently aged alfalfa fields (0, 5, 9, 13, 16, 23, 30 years). The results show that soil C storage (0–100 cm) dynamics were consistent with belowground biomass storage with increased planting years, but C storage always increased with the number of planting years in the 0–5 cm soil layer. Planted perennial alfalfa resulted in a decline in soil C storage in the 0–100 cm soil depth in the early period (nine years). During the late succession stage of alfalfa (13 years) soil C storage tends to recover, and after 16 years, storage values again dropped. However, it had recovered by 30 years at which time alfalfa productivity was very low. Vegetation C storage was mainly decided by the belowground biomass and ecosystem C storage dynamics was consistent with soil C storage. Vegetation biomass, root/shoot ratio, SOC, soil total nitrogen, and total phosphorus were the main factors affecting C storage in the entire alfalfa field ecosystem. The results suggest that C storage in vegetation is directly related to plant productivity, C storage in the soil throughout the entire alfalfa field ecosystem was not only related to plant productivity, but also to SOC and soil nutrients.

Methane emission and dynamics of methanotrophic and methanogenic communities in a flooded rice field ecosystem

Methane emissions, along with methanotrophs and methanogens and soil chemical properties, were investigated in a flooded rice ecosystem. Methane emission increased after rice transplantation (from 7.2 to 552 mg day(-1) m(-2) ) and was positively and significantly correlated with transcripts of pmoA and mcrA genes, transcript/gene ratios of mcrA, temperature and total organic carbon. Methane flux was negatively correlated with sulfate concentration. Methanotrophs represented only a small proportion (0.79-1.75%) of the total bacterial 16S rRNA gene reads: Methylocystis (type II methanotroph) decreased rapidly after rice transplantation, while Methylosinus and unclassified Methylocystaceae (type II) were relatively constant throughout rice cultivation. Methylocaldum, Methylobacter, Methylomonas and Methylosarcina (type I) were sparse during the early period, but they increased after 60 days, and their maximum abundances were observed at 90-120 days. Of 33 218 archaeal reads, 68.3-86.6% were classified as methanogens. Methanosaeta, Methanocella, Methanosarcina and Methanobacterium were dominant methanogens, and their maximum abundances were observed at days 60-90. Only four reads were characteristic of anaerobic methanotrophs, suggesting that anaerobic methane metabolism is negligible in this rice paddy system. After completing a multivariate canonical correspondence analysis of our integrated data set, we found normalized mcrA/pmoA transcript ratios to be a promising parameter for predicting net methane fluxes emitted from rice paddy soils.

A functional test platform for the Community Land Model

The realistic representation of key biogeophysical and biogeochemical functions is the fundamental of process-based ecosystem models. A functional test platform is designed to create direct linkages between site measurements and the process-based ecosystem model within the Community Earth System Models (CESM). The platform consists of three major parts: 1) interactive user interfaces, 2) functional test models and 3) observational datasets. It provides much needed integration interfaces for both field experimentalists and ecosystem modelers to improve the model's representation of ecosystem processes within the CESM framework without large software overhead.

Facilitative and inhibitory effect of litter on seedling emergence and early growth of six herbaceous species in an early successional old field ecosystem.

In the current study, a field experiment was conducted to examine effects of litter on seedling emergence and early growth of four dominant weed species from the early successional stages of old field ecosystem and two perennial grassland species in late successional stages. Our results showed that increased litter cover decreased soil temperature and temperature variability over time and improved soil moisture status. Surface soil electrical conductivity increased as litter increased. The increased litter delayed seedling emergence time and rate. The emergence percentage of seedlings and establishment success rate firstly increased then decreased as litter cover increased. When litter biomass was below 600 g m−2, litter increased seedlings emergence and establishment success in all species. With litter increasing, the basal diameter of seedling decreased, but seedling height increased. Increasing amounts of litter tended to increase seedling dry weight and stem leaf ratio. Different species responded differently to the increase of litter. Puccinellia tenuiflora and Chloris virgata will acquire more emergence benefits under high litter amount. It is predicted that Chloris virgata will dominate further in this natural succession old field ecosystem with litter accumulation. Artificial P. tenuiflora seeds addition may be required to accelerate old field succession toward matured grassland.

Drivers and regulating mechanisms of grassland and desert ecosystem services

Examining the drivers and regulating mechanisms of multiple ecosystem services has emerged as a central issue in ecology in recent years. In this paper, we start with the definition of ecosystem services, recent progresses and research priorities in the field. Then, we propose an experimental network to examine the key drivers of ecosystem services and relationships among multiple ecosystem services across grassland and desert ecosystems in northern China. The research network include conceptual diagram, research questions and objectives, field experimental design, ecosystem properties and processes observed across four grassland and desert sites. We review the major findings from the experimental network and future research directions in grassland and desert ecosystem services.

周边不同生境条件对茶园蜘蛛群落及叶蝉种群时空结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 周边不同生境条件对茶园蜘蛛群落及叶蝉种群时空结构的影响 DOI: 10.5846/stxb201308102054 作者: 作者单位: 广东省农业科学院饮用植物研究所;华南农业大学农业部热带农业环境重点实验室,广东省农业科学院饮用植物研究所,广东省农业科学院饮用植物研究所,广东省农业科学院饮用植物研究所,华南农业大学农业部热带农业环境重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划项目（2011CB100400）；国家科技支撑计划项目（2011BAD01B02-10）；国家茶叶产业技术体系专项（CARS-23）；广东省科技计划项目 （2010B031700029，2011B031400001，2012B040301041，2012B060500005） Effects of the surrounding habitat on the spider community and leafhopper population in tea plantations Author: Affiliation: Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences;The Key Lab of Agro-Environment of Tropics, Agriculture Ministry of China, South China Agricultural University,Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences,Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences,Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences,The Key Lab of Agro-Environment of Tropics,Agriculture Ministry of China,South China Agricultural University 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:为利用天敌实施害虫生态控制，田间调查了周边不同生境条件对茶园蜘蛛及叶蝉种群结构的影响。结果表明：小乔木生境茶园（Ⅰ）和相思树生境茶园（Ⅲ）影响下茶园蜘蛛及叶蝉聚集程度较强，茶园Ⅰ叶蝉聚集数最多，为692 头，但与其他生境茶园间差异不显著（P>0.05）；茶园Ⅲ蜘蛛聚集数量最多，为1155 头，并与稻田生境茶园（Ⅱ）、生活区生境茶园（Ⅳ）的差异达到显著水平（P<0.05）；从蜘蛛功能群聚集情况来看，结网型蜘蛛相对较少，为295 头；游猎型蜘蛛最多，为2957 头；其中，茶园Ⅰ与茶园Ⅲ蜘蛛多样性指数和丰富度数值较大，对叶蝉的跟随效应明显，并与Ⅱ、Ⅳ茶园有显著差异（P<0.05）。多元数据分析结果显示，茶园Ⅰ和茶园Ⅲ均能够明显提高蜘蛛群落聚集的时空分布水平；蜘蛛群落的聚集密度时空分布大小表现为：茶园Ⅰ > 茶园Ⅲ > 茶园Ⅳ > 茶园Ⅱ。由此可知周边生境结构植物丰富和相对稳定的茶园能通过和谐的生态过程影响蜘蛛和叶蝉的时空格局，提高蜘蛛对害虫叶蝉的自然控制能力。 Abstract:The issue of carbon emissions from tea plantations is currently the focus of global attention. The agricultural field ecosystem is a major factor in maintaining a balance, and plays a significant role in counteracting emissions. Our aim was to explore the aggregation indices, individual number, spatial distribution, dynamic occurrence, and principal component of arthropods, and their effects on tea plantations. Field experiments were conducted at the Drinkable Plants Research Institute, Guangdong Academy of Agricultural Sciences, Yingde County, Guangdong, China. Sampling was carried out continuously from January to December, 2009.In order to develop more effective pest control on tea plantations, four plantations were surveyed to quantify the effects of different surrounding habitats on both the pest (the leafhopper, Empoasca vitis Gothe) and predatory spider populations. No pesticides were used on the plantations. The results showed that: (1) The biggest aggregation occurred in the tea plantations surrounded by mixed natural woodland (plantation Ⅰ) or pure Acacia confusa communities (plantation Ⅲ). The greatest numbers of leafhoppers (692) occurred in plantation Ⅰ; however, this value was not significantly different from that found in the other three tea plantations (P>0.05). The number of predatory spiders in plantation Ⅲ (1155) was significantly higher than that found in the other three tea plantations (P<0.05). (2) Analysis of the behavior of all aggregated spider species showed that the number of spiders that remained in their webs was relatively small (295), which is significantly less than the 2957 spiders that were observed moving. The diversity index and species-rich value were both highest in plantations Ⅰ and Ⅲ. This had an obvious effect on leafhopper numbers, which were significantly higher than those found in plantations close to paddy fields (plantation Ⅱ) or to a village (plantation Ⅳ). Both predatory spiders and leafhoppers showed aggregated distribution, caused by their own biological habits and the common environment; different ways of managing habitats lead to significant differences in the size and diversity of the spider communities and the size of the leafhopper population. (3) Multivariate data analysis showed that the comprehensive distribution characteristics of the spider communities-both in time and space-had the potential for significant improvement in plantations Ⅰ and Ⅲ, over those in plantations Ⅱ and Ⅳ (P<0.05). These data enabled the behavior of predatory spiders in tracking their leafhopper prey to be examined. The aggregation density of spiders in the tea plantations was: plantation Ⅰ (close to mixed natural woodland) > plantation Ⅲ (close to pure Acacia confusa communities) > plantation Ⅳ (close to a village) > plantation Ⅱ (close to paddy fields). These results indicate that the habitat surrounding a tea plantation, being a relatively stable and complex structure, affects the spatial and temporal pattern of both leafhopper and spider populations through ecological processes. This leads to an increase in the quantity of spiders moving about on the tea trees, which creates a synergistic effect of leafhopper capture, hence improving the ability of predatory spiders to control leafhopper numbers. 参考文献 相似文献 引证文献

Seasonal characteristics of CO2 fluxes in a rain-fed wheat field ecosystem at the Loess Plateau

This study investigated the dynamics of CO2 flux in a rain-fed wheat field ecosystem using an eddy covariance technique during the 2011 to 2012 wheat-growing season at the Loess Plateau, China. Results showed that the daily CO2 flux was closely related to photosynthetically active radiation (PAR), growth stage, soil temperature and rainfall. The average CO2 flux at different growth stages followed the order jointing and booting &gt; erecting &gt; reviving &gt; heading &gt; wintering &gt; seeding and tillering &gt; grain filling &gt; ripening. The first four stages were carbon sinks, whereas the last four stages were carbon sources. The relationship between nighttime CO2 flux and air temperature was significant and fitted the index model (y=aebt). The relationship between daytime CO2 flux and PAR was also significant and fitted the quadratic model (y=ax2+bx+c). Moreover, daytime CO2 flux was significantly correlated with air temperature and PAR at the erecting, jointing and booting, and heading stages. Nighttime CO2 flux was also significantly correlated with soil temperature at 5 cm depth at the heading as well as jointing and booting stages. The carbon budget in the rain-fed wheat ecosystem was -401 g C m-2 yr-1, which was higher than those in other wheat ecosystems. This study implies that the ability of carbon-sequestration in different wheat field ecosystems may respond differently to climate and environment change.

Indonesia

There are approximately 1.4 million hectares of swampy area in South Sumatera, but only 12% of those are being used as farm and plantation. The purpose of this research was to investigate the similarity of arthropod community inhabiting swampy rice field and its surrounding area. This research was conducted in South Sumatera Province covering regency of Musi Banyuasin and Palembang. Four types of swampy area were selected from each location, i.e. rice field, thicket, bush, and swampy land inhabited by broad-leaf weeds. Pitfall trap used to collect arthropod and it installed at five different times. i.e. 15 days before rice planting, one month, two months, and three months after planting, and 15 days after harvest time. The result showed that relative abundance of predatory arthropod dwelling soil in rice field was 95.03%, and habitat surrounding rice field was 95.12–97.21%. The level of similarity of arthropod species between rice field ecosystem and its surrounding area ranged from 0.73 to 0.84. Thus, the surrounding area of rice field probably can be used as catchment area of predatory arthropod and other pests during planting season.

Dynamics and residues of mixed formulation of fenamidone and mancozeb in gherkin field ecosystem

The dynamics and residues of mixed formulation of fenamidone and mancozeb in a gherkin field ecosystem were investigated. The quantification was performed using gas chromatography-electron capture detection (GC-ECD) and UV–vis spectrophotometry for fenamidone and mancozeb residues, respectively. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 92 to 98 and 90 to 96 percent with relative standard deviations (RSD) ranging of 0.78–5.9 and 2.04–4.41 percent for fenamidone and mancozeb, respectively. The compound degradation followed a first order kinetics with half-lives of 2.8–2.82 and 2.02–2.26 days, for fenamidone and mancozeb, respectively. Pesticide residues in fruit were below the EU maximum residue level (MRL) after 10 days for fenamidone (0.02µg/g) and just after treatment for mancozeb (2µg/g). These results can be utilized in formulating the spray schedule and safety evaluation for these pesticides in gherkin.

The effect of planting density on carbon dioxide, methane and nitrous oxide emissions from a cold paddy field in the Sanjiang Plain, northeast China

The effect of planting density on greenhouse gas (GHG) emissions from cold paddy (Oryza sativa L.) field ecosystems deserves attention because of the increase in planting area and the application of sparse planting for rice cultivation in northeast China. To quantify its effect, we measured carbon dioxide (CO2) (via ecosystem respiration), methane (CH4) and nitrous oxide (N2O) fluxes from different planting density treatments in a cold paddy field in the Sanjiang Plain during a single growing season. Conventional (D24, 24hillsm−2), proper-sparse (D16, 16hillsm−2) and super-sparse planting (D8, 8hillsm−2) and fallow, bare soil (D0, 0hillsm−2) were used in this study. The field plots that were left fallow in the current year emitted CH4, N2O and CO2, with average fluxes of 1.9±0.4mgCm−2h−1, 51±4μgNm−2h−1 and 36.8±2.8mgCm−2h−1, respectively. Rice planting significantly (p<0.01) increased CH4 emissions and ecosystem respiration but slightly decreased N2O emissions. The cumulative emissions of CH4, N2O and ecosystem respiration in the conventional planting density treatment (i.e., D24) were 156±7kgCha−1, 1.7±0.1kgNha−1 and 5213±340kgCha−1, respectively. Significantly (p<0.05) lower CH4 emissions, total emissions of CH4 and N2O and ecosystem respiration were determined for D8 compared to D24. Lowest value of yield-based flux (i.e., 1307kg CO2eq.ton−1) was calculated at D16, which indicates proper-sparse planting might be the most appropriate planting density to balance the yield and total GHG emission in this region.

High prevalence of IncP-1 plasmids and IS1071insertion sequences in on-farm biopurification systems and other pesticide-polluted environments

Mobile genetic elements (MGEs) are considered as key players in the adaptation of bacteria to degrade organic xenobiotic recalcitrant compounds such as pesticides. We examined the prevalence and abundance of IncP-1 plasmids and IS1071, two MGEs that are frequently linked with organic xenobiotic degradation, in laboratory and field ecosystems with and without pesticide pollution history. The ecosystems included on-farm biopurification systems (BPS) processing pesticide-contaminated wastewater and soil. Comparison of IncP-1/IS1071 prevalence between pesticide-treated and nontreated soil and BPS microcosms suggested that both IncP-1 and IS1071 proliferated as a response to pesticide treatment. The increased prevalence of IncP-1 plasmids and IS1071-specific sequences in treated systems was accompanied by an increase in the capacity to mineralize the applied pesticides. Both elements were also encountered in high abundance in field BPS ecosystems that were in operation at farmyards and that showed the capacity to degrade/mineralize a wide range of chlorinated aromatics and pesticides. In contrast, IS1071 and especially IncP-1, MGE were less abundant in field ecosystems without pesticide history although some of them still showed a high IS1071 abundance. Our data suggest that MGE-containing organisms were enriched in pesticide-contaminated environments like BPS where they might contribute to spreading of catabolic genes and to pathway assembly.

Bacterial Community Structure in a Semi-Arid Haloalkaline Soil Using Culture Independent Method

Bacterial community structures in two physicochemically different soils from the coastal region of Gujarat, India were investigated using PCR, 16S rRNA gene clone libraries and sequencing methods. The aim of the study was to determine the diversity of bacterial communities inhabiting haloalkaline soil from a semi-arid coastal region. The phylogenetic diversity of bacteria in a haloalkaline soil (EC 20 dS/m; pH 9.5) was compared with a normal soil (EC 0.93 dS/m; pH 7.2). Clones representing phyla Proteobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Actinobacteria, Acidobacteria and Planctomycetes were found in both soils. Cyanobacteria, Verrucomicrobia, OP10 and Bacteria incertae sedis were detected in normal soil whereas Nitrospira was found only in haloalkaline soil. The dominant phylum in the haloalkaline soil was Bacteroidetes followed by Proteobacteria whereas normal soil was dominated by Proteobacteria and Actinobacteria. About 82% of the sequences from the haloalkaline library were related to those previously retrieved from various saline, alkaline and oil-natural gas field ecosystems whereas 50% of the sequences from normal soil resembled sequences of bacteria retrieved from agriculture-related habitats viz. agriculture fields, rhizosphere and grasslands. One third of the total sequences from both soil samples showed low BLAST identities (<95%) suggesting that these soils may harbor unique, novel taxa. Further, the correlation analysis revealed negative correlations of Shannon diversity indices and species evenness with salinity (EC) and pH but positive correlations with total carbon and total nitrogen contents of the soil samples. The haloalkaline soil exhibited less bacterial diversity and communities were significantly different from those of normal soil. In this study, the haloalkaline soil from a semi-arid region supports oligotrophic microbes. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.

Food and Feeding Habits of the Mola Carplet Amblypharyngodon mola (Hamilton, 1822) in Rice Field Ecosystem with Consideration of Water Quality Parameters

The present investigation was conducted in the Agronomy field laboratory of Bangladesh Agricultural University, Mymensingh, Bangladesh during May 1999 to August 1999 to reveal the food and feeding habits of Amblypharyngodon mola in the rice field ecosystem. Percentage of frequency of occurrence and percentage in number methods were used for the qualitative and quantitative estimation of plankton population. Results showed that, during the present study, the water quality parameters were within the suitable range for optimal fish growth and plankton population was abundant in the water of the rice plots. Gut content analysis of A. mola revealed a sum of 32 genera of phytoplankton belonging to Chlorophyceae (17), Euglenophyceae (2), Cyanophyceae (7) and Bacillariophyceae (6) and 8 genera of zooplankton under Rotifera (3), Cladocera (2) and Copepoda (3). In general, Navicula, Fragilaria, Chlorella, Chrysococcus, Closterium, Oscillatoria and Gomphosphaeria were found abundant both in the water of the rice plots and in the gut contents of A. mola indicating that, these genera are preferred food of this fish in the rice field ecosystem. Gut content analysis also exposed that, phytoplankton was the major food item constituting 94.38% of the gut contents’ composition of A. mola whereas zooplankton comprised only 5.62%. The results of this study conclude that, the A. mola is planktivorous in nature, feeding mostly on phytoplankton and could be a suitable species for integrated rice-fish farming.DOI: http://dx.doi.org/10.3126/on.v11i1.8245 Our Nature Vol.11(1) 2013: 61-75

Residues of cyantraniliprole and its metabolite J9Z38 in rice field ecosystem

A simple and reliable analytical method was developed to detect cyantraniliprole (HGW86) and its metabolite J9Z38 in rice straw, paddy water, brown rice, and paddy soil. The fate of cyantraniliprole and its metabolite J9Z38 in rice field ecosystem was also studied. The target compounds were extracted using acetonitrile, cleaned up on silicagel or strong anion exchange column, and analyzed by ultra-performance liquid chromatography–tandem mass spectrometry. The average recoveries of cyantraniliprole and J9Z38 in rice straw, paddy water, brown rice, and paddy soil ranged from 79.0% to 108.6%, with relative standard deviations of 1.1–10.6%. The limits of quantification of cyantraniliprole and J9Z38 were 18 and39μgkg−1 for rice straw, 2.8 and 5.0μgkg−1 for paddy water, 4.3 and 6.3μgkg−1 for brown rice, and 3.9 and 5.3μgkg−1 for paddy soil. The trial results showed that the half-lives of cyantraniliprole were 3.2, 4.4, and 6.3d in rice straw and 4.9, 2.0, and 6.2d in paddy water in Zhejiang, Hunan, and Shandong, respectively. The respective final residues of cyantraniliprole and J9Z38 in brown rice were lower than 0.05 and 0.02mgkg−1 after 14d of pre-harvest interval. The maximum residue limit of cyantraniliprole at 0.1mgkg−1 and dosage of 100g a.i.hm−2, which could be considered safe to human beings and animals, were recommended.