引入科研前沿对植物生理学教学方法的改进和效果分析

大学生普遍存在科研创新意识差、缺乏科研热情的现象.补充相关科研进展,将科研前沿引进课堂成为一种趋势,笔者对植物生理学光合作用这一章关于补充光合碳同化科研进展与否的教学实践结果进行对比分析,采用调查问卷的形式,围绕已讲授和未讲授光合碳同化适应性进化这一科研前沿进行调查,旨在实现学生对光合碳同化途径多元化发展进化的理解和深化,启发学生对固有知识的质疑和求解热情,达到提升科研兴趣和创新能力,实现精品课程培养满足国家和地方发展需要的高素质人才的目的.     

Sewage sludge processing determines its impact on soil microbial community structure and function

Composting and thermal drying are amongst the most commonly used post-digestion processes for allowing sanitation and biological stabilization of sewage sludge from municipal treatment plants, and making it suitable as soil conditioner for use in agriculture. To assess the impact of sludge-derived materials on soil microbial properties, fresh (LAF), composted (LAC) and thermally dried (LAT) sludge fractions, each resulting from a different post-treatment process of a same aerobically digested sewage sludge, were added at 1% (w/w) application rate on two contrasting (a loam and a loamy sand) soils and incubated under laboratory conditions for 28 days. Soil respiration, microbial ATP content, hydrolytic activities and arginine ammonification rate were monitored throughout the incubation period. Results showed that soil biochemical variables, including the metabolic quotient (qCO₂), were markedly stimulated after sludge application, and the magnitude of this stimulatory effect was dependent on sludge type (precisely LAT > LAF > LAC), but not on soil type. This effect was related to the content of stable organic matter, which was lower in LAT. Genetic fingerprinting by PCR–DGGE revealed that compositional shifts of soil bacterial and, at greater extent, actinobacterial communities were responsive to the amendment with a differing sludge fraction. The observed time-dependent changes in the DGGE profiles of amended soils reflected the microbial turnover dependent on the sludge nutrient input, whereas no indications of adverse effects of sludge-borne contaminants were noted. Our findings indicate that composting rather thermal drying can represent a more appropriate post-digestion process to make sewage sludge suitable for use as soil conditioner in agriculture.     

Earthworms increase soil microbial biomass carrying capacity and nitrogen retention in northern hardwood forests

Earthworms have been shown to produce contrasting effects on soil carbon (C) and nitrogen (N) pools and dynamics. We measured soil C and N pools and processes and traced the flow of ¹³C and ¹⁵N from sugar maple (Acer saccharum Marsh.) litter into soil microbial biomass and respirable C and mineralizable and inorganic N pools in mature northern hardwood forest plots with variable earthworm communities. Previous studies have shown that plots dominated by either Lumbricus rubellus or Lumbricus terrestris have markedly lower total soil C than uncolonized plots. Here we show that total soil N pools in earthworm colonized plots were reduced much less than C, but significantly so in plots dominated by contain L. rubellus. Pools of microbial biomass C and N were higher in earthworm-colonized (especially those dominated by L. rubellus) plots and more ¹³C and ¹⁵N were recovered in microbial biomass and less was recovered in mineralizable and inorganic N pools in these plots. These plots also had lower rates of potential net N mineralization and nitrification than uncolonized reference plots. These results suggest that earthworm stimulation of microbial biomass and activity underlie depletion of soil C and retention and maintenance of soil N pools, at least in northern hardwood forests. Earthworms increase the carrying capacity of soil for microbial biomass and facilitate the flow of N from litter into stable soil organic matter. However, declines in soil C and C:N ratio may increase the potential for hydrologic and gaseous losses in earthworm-colonized sites under changing environmental conditions.     

对我国LULUCF碳计量监测方法的探讨

围绕我国林业编制温室气体清单这一重要工作,介绍了IPCC关于LULUCF温室气体清单编制系列技术指南的技术要点和要求,阐明了我国林业温室气体清单编制工作的进展,提出了林业开展LULUCF碳监测工作未来面临的需求。同时,在分析美国、欧盟、加拿大等发达国家LULUCF温室气体清单编制做法和经验的基础上,提出了"在森林资源清查样地系统上构建"、"新布设LULUCF大样地系统"等2种开展LULUCF碳监测的思路,目的是为推动我国林业LULUCF碳监测达到国际先进水平提供建议。     

Environmental stress response limits microbial necromass contributions to soil organic carbon

The majority of dead organic material enters the soil carbon pool following initial incorporation into microbial biomass. The decomposition of microbial necromass carbon (C) is, therefore, an important process governing the balance between terrestrial and atmospheric C pools. We tested how abiotic stress (drought), biotic interactions (invertebrate grazing) and physical disturbance influence the biochemistry (C:N ratio and calcium oxalate production) of living fungal cells, and the subsequent stabilization of fungal-derived C after senescence. We traced the fate of ¹³C-labeled necromass from ‘stressed’ and ‘unstressed’ fungi into living soil microbes, dissolved organic carbon (DOC), total soil carbon and respired CO₂. All stressors stimulated the production of calcium oxalate crystals and enhanced the C:N ratios of living fungal mycelia, leading to the formation of ‘recalcitrant’ necromass. Although we were unable to detect consistent effects of stress on the mineralization rates of fungal necromass, a greater proportion of the non-stressed (labile) fungal necromass C was stabilised in soil. Our finding is consistent with the emerging understanding that recalcitrant material is entirely decomposed within soil, but incorporated less efficiently into living microbial biomass and, ultimately, into stable SOC.     

Short‐term releases of CO2 from newly mixed biochar and calcareous soil

The work aimed to quantify native organic C mobilized in one calcareous soil in the 21 days after addition of biochar at a range of large to very large applications. The experiment was carried out in unplanted microcosms, and CO₂ flux was used as a measure of net mineralization. A rapid methodological approach, which does not require ¹³C as a tracer, was used to assess any priming effects induced by the biochar. The amount of CO₂‐C mobilized was small relative to the amount of biochar C and proportional to the amount of the biochar added. The additional CO₂‐C was similar to the content of the water‐soluble organic carbon in the biochar added with each application. No interaction with native soil C, that is priming effect, was observed.     

Contribution of Different Organs to Grain Filling in Durum Wheat under Mediterranean Conditions I. Contribution of Post‐Anthesis Photosynthesis and Remobilization

Under Mediterranean conditions, drought affects cereals production principally through a limitation of grain filling. In this study, the respective role of post‐anthesis photosynthesis and carbon remobilization and the contribution of flag leaf, stem, chaff and awns to grain filling were evaluated under Mediterranean conditions in durum wheat (Triticum turgidum var. durum) cultivars. For the purpose, we examined the effects of shading and excision of different parts of the plant and compared carbon isotope discrimination (Δ) in dry matter of flag leaf, stem, chaff, awns and grain at maturity and in sap of stem, flag leaf, chaff and awns, this last measurement providing information on photosynthesis during a short period preceding sampling. Source–sink manipulations and isotopic imprints of different organs on final isotope composition of the grain confirmed the high contribution of both carbons assimilated by ears and remobilized from stems to grain filling, and the relatively low contribution of leaves to grain filling. Grain Δ was highly and significantly associated with grain yield across treatments, suggesting the utilization of this trait as an indicator of source–sink manipulations effects on grain yield. Chaff and awns Δ were better correlated with grain Δ than stem and leaf Δ, indicating that chaff were more involved in grain filling than other organs. Moreover, in chaff, sap Δ was highly significantly correlated with dry matter Δ. These results suggest the use of Δ for a rapid and non‐destructive estimation of the variation in the contribution of different organs to grain filling.     

Soil aggregation: Influence on microbial biomass and implications for biological processes

Our 1988 paper, describing the effects of cultivation on microbial biomass and activity in different aggregate size classes, brought together the ‘aggregate hierarchy theory’ and the ‘microbial biomass concept’. This enabled us to identify the relationships between microbial and microhabitat (aggregate) properties and organic matter distribution and explain some of their responses to disturbance. By combining biochemical and direct microscopy based quantification of microbial abundance with enzyme activities and process measurements, this study provided evidence for the role of microbial biomass (especially fungi) in macroaggregate dynamics and carbon and nutrient flush following cultivation. In the last ten years environmental genomic techniques have provided much new knowledge on bacterial composition in aggregate size fractions yet detailed information about other microbial groups (e.g. fungi, archaea and protozoa) is lacking.We now know that soil aggregates are dynamic entities – constantly changing with regard to their biological, chemical and physical properties and, in particular, their influences on plant nutrition and health. As a consequence, elucidation of the many mechanisms regulating soil C and nutrient dynamics demands a better understanding of the role of specific members of microbial communities and their metabolic capabilities as well as their location within the soil matrix (e.g. aggregates, pore spaces) and their reciprocal relationship with plant roots. In addition, the impacts of environment and soil type needs to be quantified at the microscale using, wherever possible, non-destructive ‘in situ’ techniques to predict and quantify the impacts of anthropogenic activities on soil microbial diversity and ecosystem level functions.     

Soil organic carbon stock variability in the Northern Gangetic Plains of India: interaction between agro‐ecological characteristics and cropping systems

Soil organic carbon (SOC) content and its spatial distribution in the Northern Gangetic Plain (NGP) Zone of India were determined to establish the cause–effect relationship between agro‐ecological characteristics, prevailing crop management practices and SOC stock. Area Spread Index (ASI) approach was used to collect soil samples from the NGP areas supporting predominant cropping systems. Exponential ordinary kriging was found most suitable geo‐statistical model for developing SOC surface maps of the NGP. Predicted surface maps indicated that 43.7% area of NGP had 0.5–0.6% SOC, while the rest of the area was equally distributed with high (0.61–0.75%) and low (< 0.5%) SOC content levels. Averaged across cropping systems, maximum SOC content was recorded in Bhabar and Tarai Zone (BTZ), followed by Central Plain Zone (CPZ), Mid‐Western Plain Zone (MWPZ), Western Plain Zone (WPZ) and South‐Western Plain Zone (SWPZ) of the NGP. The SOC stock was above the optimum threshold (> 12.5 Mg/ha) in 97.8, 57.6 and 46.4% areas of BTZ, CPZ and MWPZ, respectively. Only 9.8 and 0.4% area of WPZ and SWPZ, respectively, had SOC stock above the threshold value. The variation in SOC stock was attributed largely to carbon addition through recycling of organic sources, cropping systems, tillage intensity, crop or residue cover and land‐use efficiency, nutrient‐use pattern, soil texture and prevailing ecosystem. Adoption of conservation agriculture, balanced use of nutrients, inclusion of legumes in cropping systems and agro‐forestry were suggested for enhancing SOC stock in the region.     

不同基质活性炭对阿特拉津吸附特性研究

为了解决阿特拉津给土壤带来的污染问题以及寻找吸附效果较好的活性炭基质,本研究利用高效液相色谱(HPLC)技术检测了阿特拉津溶液和悬浮液经煤、木、果和竹质4种生物炭处理后的残留量,并对其在阿特拉津溶液和土壤中的吸附动态进行检测。结果表明,煤质活性炭对初始浓度为100 mg/L和10 mg/L的阿特拉津溶液和悬浮液的吸附效果较好,其吸附率为5.651%~68.42%;当阿特拉津初始浓度为100 mg/L时,煤质活性炭在40 min时对阿特拉津溶液的吸附率高达23.49%;与对照组相比,当阿特拉津的初始浓度为100 mg/L时,土壤中阿特拉津经煤质活性炭处理42天后的残留浓度最低,活性炭吸附率达到91.39%。综上,煤质活性炭能有效降解溶液及土壤中阿特拉津含量,这将为阿特拉津污染土壤的改良研究奠定基础。