Abundance and Structure Composition of nirK and nosZ Genes as Well as Denitrifying Activity in Heavy Metal-polluted Paddy Soils

Denitrification is an important microbial process in soils and leads to the emission of nitrous oxide (N₂O). However, studies about the microbial community involved in denitrification processes in polluted paddy fields are scarce. Here, we studied two rice paddies which had been polluted for more than three decades by metal mining and smelter activities. Abundance and community composition were determined using real-time polymerase chain reaction (PCR) assay and denaturing gradient gel electrophoresis of nitrite reductase and nitrous oxide reductase gene amplicons (nirK and nosZ), while denitrifying activities were assessed by measuring potential denitrifier enzyme activity. We found that the community structure of both nirK and nosZ containing denitrifiers shifted under pollution in the two rice paddies. All the retrieved nirK sequences did not group into either α- or β-proteobacteria, while most of the nosZ species were affiliated with α-proteobacteria. While the abundance of both nirK and nosZ was significantly reduced in the polluted soils at “Dexing” (with relatively higher Cu levels), these parameters did not change significantly at “Dabaoshan” (polluted with Cd, Pb, Cu, and Zn). Furthermore, total denitrifying activity and N₂O production and reduction rates also only decreased under pollution at “Dexing.” These findings suggest that nirK and nosZ containing denitrifier populations and their activities could be sensitive to considerable Cu pollution, which could potentially affect N₂O release from polluted paddy soils.     

综合土地利用及空间异质性的土壤有机碳空间插值模型

土壤有机碳库是陆地碳库的重要组成部分,土壤有机碳库及其动态变化对陆地生态系统碳循环有着重要的影响.土壤有机碳密度(SOCD)是土壤碳储量的重要参数,也是评价农田土壤质量的重要指标,准确预测区域SOCD空间分布对发展精确农业有重要意义.本文使用江汉平原地区242个农田土壤样本数据,探究平原地区土地利用类型对SOCD空间分布的影响,以及当SOCD空间分布规律呈现空间异质性且存在空间异常值的情况下,虚拟变量回归克里格法(DV_RK)、均值中心化克里格法(MC_OK1)和中位数中心化克里格法(MC_OK2)这3种结合土地利用的克里格法在SOCD空间预测中的应用.结果表明: 土地利用方式的差异是研究区水田和水浇地SOCD存在空间异质性的原因之一,导致SOCD存在空间非平稳特征,降低了普通克里格法(OK)的预测精度;而DV_RK、MC_OK1和MC_OK2在消除了由土地利用引起的SOCD空间异质性对建模的影响后,模型的稳定性提升,其预测精度均高于OK,其中,MC_OK2的模型可靠程度、预测精度和对SOCD总方差的解释能力最优.因此,土地利用类型作为易获取的辅助变量,可以有效减弱空间异质性和空间异常值对SOCD空间插值的影响,提升模型精度,降低不确定性,并与MC_OK2结合生成更高精度的SOCD空间分布图,帮助揭示SOCD空间分异规律,指导农业生产.     

湿地农田生态系统的特点及其调节

所谓湿地,系一个笼统的名称,直到目前并没有确切的定义。通常认为凡受地下水与地表水影响的土地均可称为湿地。它又可区分为两大类,即自然湿地与人工湿地,区别在于受不受人为活动干扰及其干扰程度。湿地包括沼泽型土壤、草甸型土壤与稻田土壤,稻田土壤在我国早期的土壤分类系统中也归为湿地族。近年来,国外对湿地研究十分活跃,从已有文献看其概念也欠确切,且因目的不同而有一定出入。例如在W.Z.Mitsh所著《湿地》一书中就引用了如下几种概念: 1.湿地系为浅水或间歇浅水层所淹没的低地,包括有植被着生的浅水湖区。2.水位接近或高于地表的土地,或者由于长期水分饱和形成的湿地,或者是具有水成土过程的土地,包括水成土以及适于水生植物     

福建稻田生态系统分析

福建地处我国东南沿海,北纬23°26′—28°22′,东经116°—120°,依山面海。土地面积1.207×10~5km~2(折1.207×10~7ha),人口2800.82万,人均0.43ha。境内山峦起伏,海拔高0—2158m,地形复杂。耕地1.2439×10~6ha,占土地面积的10.1%,人均耕地0.045ha,为山多人多耕地少的省份。稻田9.56×10~5ha,其中75.4%分布于山区,多为中低产田,平均年产6165kg·ha~(-1);24.6%分布在沿海冲积平原,平均年产10042.5kg·ha~(-1)。现将稻田生态系统综合分析如下,为提高稻作产量,解决福建粮食问题提供参考。     

太湖地区两种稻麦轮作制中营养元素的循环——Ⅱ.常规稻田生态系统中大量元素的循环状况

本文在太湖流域研究了平原地区三个不同试验点上小麦-水稻和元麦-水稻-水稻两种轮作方式下常规稻田生态系统中氮、磷、钾、钙、镁等五种大量营养元素的循环及表观平衡状况。所考虑的输入途径有施肥、灌溉、降雨、播种及移栽;输出途径有作物收获、田面排水和渗漏淋溶。此外,氮素的输出还包括了氨挥发及硝化与反硝化脱氮。三试验点两种熟制的稻田生态系统中各元素的表观平衡状况基本一致,在土壤养分库中磷、氮有盈余,钾、镁和钙有亏损。     

Application of lidar remote sensing of insects in agricultural entomology on the Chinese scene

Insect pest management is a very important aspect for plant protection in crops production. Remote sensing provides a large number of techniques that are beneficial in entomological research. Although entomological radars have been used for studying migrations of insects for many years, most of entomological radar studies have been vertically tracing high-altitude migration behaviour of insects. Light detection and ranging (lidar) is a counterpart to radar, now operating in the optical part of the electromagnetic spectrum, which has been recently applied for monitoring of insects at low altitude. Such techniques, in particular low-cost continuous-wave (CW) bi-static systems based on the Scheimpflug arrangement, have been rapidly developing during the last decade. As a result, optical methods present new and fascinating possibilities. Based on experience from a 2-week field campaign in rice paddy fields, we here present an overview of lidar remote sensing applied to the Chinese scene. The capability of a CW Scheimpflug lidar system in monitoring the insects was studied. We present results on insect abundance in relation to time of the day and weather conditions. We also identified insect species by analysing wing-beat frequencies and studied their attraction to ultraviolet (UV) lamp located close to the horizontal laser sampling path during night time. Results showed that the insect species were abundant, that insects detected by the lidar system were attracted to light and that light rain increased the insect activity. The lidar detection system had a high read-out frequency, enabling the estimation of insect wing-beat frequencies.     

钾肥用量及基追肥比例对烤烟干物质累积和钾素吸收动态的影响

采用田间小区试验研究了钾肥用量及基追肥比例对种植于红壤性水稻土上的烤烟干物质积累和钾素吸收动态的影响.结果表明,烤烟干物质累积高峰出现在烟株移栽后50～60 d,栽后30 d内以及80 d后累积较少.烤烟干物质累积总量随钾肥用量增加和追肥比例提高而增加.烟株含钾量在移栽后30～50 d最高,随后迅速降低,至成熟期仅为最高含钾量的一半.315 kg·hm^-2施钾处理在各生育期烟株平均含钾量均显著高于225 kg·hm^-2施钾处理.烟叶成熟时,225 kg·hm^-2施钾处理出现干物质累积负增长和钾素损失现象,而315 kg·hm^-2处理干物质累积和吸钾总量均呈持续增加趋势.成熟时基追肥比例为3∶7处理的烟株含钾量明显高于基追肥比例为5∶5和7∶3的处理.     

Microbial mechanism for rice variety control on methane emission from rice field soil

Rice variety is one of the key factors regulating methane (CH₄) production and emission from the paddy fields. However, the relationships between rice varieties and populations of microorganisms involved in CH₄ dynamics are poorly understood. Here we investigated CH₄ dynamics and the composition and abundance of CH₄‐producing archaea and CH₄‐oxidizing bacteria in a Chinese rice field soil planted with three types of rice. Hybrid rice produced 50–60% more of shoot biomass than Indica and Japonica cultivars. However, the emission rate of CH₄ was similar to Japonica and lower than Indica. Furthermore, the dissolved CH₄ concentration in the rhizosphere of hybrid rice was markedly lower than Indica and Japonica cultivars. The rhizosphere soil of hybrid rice showed a similar CH₄ production potential but a higher CH₄ oxidation potential compared with the conventional varieties. Terminal restriction fragment length polymorphism analysis of the archaeal 16S rRNA genes showed that the hydrogenotrophic methanogens dominated in the rhizosphere whereas acetoclastic methanogens mainly inhabited the bulk soil. The abundance of total archaea as determined by quantitative (real‐time) PCR increased in the later stage of rice growth. However, rice variety did not significantly influence the structure and abundance of methanogenic archaea. The analysis of pmoA gene fragments (encoding the α‐subunit of particulate methane monooxygenase) revealed that rice variety also did not influence the structure of methanotrophic proteobacteria, though variable effects of soil layer and sampling time were observed. However, the total copy number of pmoA genes in the rhizosphere of hybrid rice was approximately one order of magnitude greater than the two conventional cultivars. The results suggest that hybrid rice stimulates the growth of methanotrophs in the rice rhizosphere, and hence enhances CH₄ oxidation which attenuates CH₄ emissions from the paddy soil. Hybrid rice is becoming more and more popular in Asian countries. The present study demonstrated that planting of hybrid rice will not enhance CH₄ emissions albeit a higher grain production than the conventional varieties.     

红壤稻田生态系统有机物料循环对土壤有机碳转化的影响

通过对12年田间定位试验数据的分析,研究了红壤稻田生态系统有机物料循环再利用对土壤有机碳积累的贡献及其对转化的影响。结果表明,红壤稻田生态系统有机物料循环再利用可促进土壤有机碳的积累、改善腐殖质组分和改良有机质品质。红壤稻田生态系统内有机物料循环再利用,土壤有机碳的年增速率最大可达到0.37 g.kg-1;12年间易氧化有机碳最大增量达到3.8 g.kg-1,胡敏酸和富里酸最大增量分别达到3.06和1.63 g.kg-1。预测结果显示,有机物料循环再利用红壤稻田生态系统土壤有机碳50年内可提高8.3~18.9 g.kg-1,增长率达到62.0%~140.7%。     

Upscaling Regional Emissions of Greenhouse Gases from Rice Cultivation: Methods and Sources of Uncertainty

One of the important sources of greenhouse gases is the emission of methane from rice fields. Methane emission from rice fields is the result of a complex array of soil processes involving plant-microbe interactions. The cumulative effects of these processes at the level of individual plants influence the global atmospheric composition and make it necessary to expand our research focus from small plots to large landscapes and regions. However, present extrapolations (‘upscaling’) are tenuous at best because of methodological and practical problems. The different steps taken to calculate regional emission strengths are discussed and illustrated by calculations for a case-study in the Philippines. The applicability of high quality, process-based, models of methane emission at the level of individual plants is limited for regional analysis by their large data requirements. Simplified models can be used at the regional level but are not able to capture the complex emission situation. Data availability and model accuracy are therefore often difficult to match. Other common sources of uncertainty are the quality of input data. A critical evaluation of input data should be made in every upscaling study to assess the suitability for calculating regional emissions. For the case-study we show effects of differences in input data caused by data source and interpolation technique. The results from the case-study and similar studies in literature indicate that upscaling techniques are still troublesome and a cause of large uncertainties in regional estimates. The results suggest that some of the stumbling blocks in the conventional upscaling procedure are almost impassable in the near future. Based on these results, a plea is made for meso-level measurements to calibrate and validate upscaling methods in order to be better able to quantify and reduce uncertainties in regional emission estimates.