Black carbon estimation in French calcareous soils using chemo‐thermal oxidation method

We studied the black carbon (BC) content of ca. 405 samples from French topsoil and artificial soil and carbonate mixtures. Our protocol involved three main steps: (i) decarbonation by HCl, (ii) elimination of non‐pyrogenic organic carbon in a furnace at 375 °C, and (iii) quantification of residual carbon by CHN analysis. BC content increased for calcareous soils according to their carbonates content. Subsequent analyses confirmed the existence of a methodological artefact for BC determination only in calcareous soils. Decarbonation changes the thermal properties of organic matter, creating more recalcitrant carbon than in the initial sample. Higher CaCO₃ and organic carbon content results in a more pronounced artefact. The reversal of the first two steps of the chemo‐thermal oxidation method (i.e. thermal oxidation before soil decarbonation) eliminates this artefact. Overall, our results suggest that BC content may have been overestimated in a large number of studies on calcareous soils.     

Can soil moisture deficit be used to forecast when soils are at high risk of damage owing to grazing animals?

A potentially significant cause of damage to grassland soils is compaction of unsaturated soil and poaching of saturated or nearly saturated soil by animal hooves. Damage is caused when an applied stress is in excess of the bearing strength of the soil and results in a loss of soil structure, macroporosity and air or water conductivity. Severely damaged soils can cause reduced grassland productivity and make grazing management very difficult for the farmer. The actual amount of soil damage that can occur during grazing is dependent on the grass cover which acts as a protecting layer, the soil water content and the characteristics of the grazing animal (weight and hoof size). Assuming that the farmer is knowledgeable about the characteristics of the grazing animal and grass cover, it would be very useful for short‐term operational farm planning to be able to predict when soil water contents were likely to be in a critical range with respect to potential hoof damage. In this study soil moisture deficits (SMDs) which can be derived from meteorological forecasts are evaluated for predicting when soil water conditions are likely to lead to hoof damage. Two contrasting Irish grassland soils were analysed using a Hounsfield servo‐mechanical vertical testing machine to simulate static (285.4 N) and dynamic (571 N) hoof loads on the soil over a range of estimated SMDs (0, 5, 10 and 20 mm). The deficits were analysed with respect to the soil volumetric water content, compression (displacement) and change in dry bulk density. The SMDs imposed in the laboratory were similar to those under field conditions and thus the methods used in this study are applicable elsewhere. The change in dry bulk density following loading (0.2–0.7 g/cm³) was linearly related to SMD (R² ranged from 0.90 to 0.99), leading to the conclusion that a forecast of SMD can be used to predict when grassland soils are likely to be at risk of damage from grazing.     

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.     

5‐Aminolevulinic Acid Activates Antioxidative Defence System and Seedling Growth in Brassica napus L. under Water‐Deficit Stress

The present study assesses the effects of 5‐aminolevulinic acid (ALA, 0, 0.1, 1 and 10 mg l^?1) on the growth of oilseed rape (Brassica napus L. cv. ZS758) seedlings under water‐deficit stress induced by polyethylene glycol (PEG 6000, 0 and ?0.3 MPa). Water‐deficit stress imposed negative effects on seedling growth by reducing shoot biomass, cotyledon water potential, chlorophyll content and non‐enzymatic antioxidants (glutathione and ascorbic acid) levels. On the other hand, water‐deficit stress enhanced the malondialdehyde (MDA) content, reactive oxygen species (ROS) production, enzymatic antioxidants activities, reduced/oxidized glutathione ratio (GSH/GSSG) and reduced/oxidized ascorbic acid (ASA/DHA) ratio in seedlings. Application of ALA at lower dosages (0.1 and 1 mg l^?1) improved shoot weight and chlorophyll contents, and decreased MDA in rape seedlings, whereas moderately higher dosage of ALA (10 mg l^?1) hampered the growth. The study also indicated that 1 mg l^?1 ALA improved chlorophyll content, but reduced MDA content and ROS production significantly under water‐deficit stress. Lower dosages of ALA (0.1 and 1 mg l^?1) also enhanced GSH/GSSG and ASA/DHA as compared to the seedlings under water‐deficit stress. The antioxidant enzymes (ascorbate peroxidase, peroxidase, catalase, glutathione reductase and superoxide dismutase) enhanced their activities remarkably with 1 mg l^?1 ALA treatment under water‐deficit stress. It was also revealed that 1 mg l^?1 ALA treatment alone induced the expression of APX, CAT and GR substantially and under water‐deficit stress conditions ALA treatment could induce the expression of POD, CAT and GR to a certain degree. These results indicated that 0.1–1 mg l^?1 ALA could enhance the water‐deficit stress tolerance of oilseed seedlings through improving the biomass accumulation, maintaining a relative high ratio of GSH/GSSG and ASA/DHA, enhancing the activities of the specific antioxidant enzymes and inducing the expression of the specific antioxidant enzyme genes.     

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。     

酸改性麦麸挂面配方的研究

为改善挂面制品的营养保健功能,研发谷物加工副产物的深加工产品,将经过超声波-酸解法改性处理后的麦麸粉添加到面粉中用于制作酸改性麦麸挂面。通过单因素试验及正交试验优化确定酸改性麦麸挂面的最优配方。结果表明,在面粉100 g的基础上,酸改性麦麸粉添加量为6%（相当于面粉质量的百分比）、水添加量为56%、食盐添加量为3.5%、食碱添加量为0.4%、羧甲基纤维素钠添加量为0.4%,此条件下制得的挂面品质良好,且外观、适口性较好。     

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.     

Optimum Soil Water Content for Chickpea Emergence in Heavy‐Textured Soils of North‐West Bangladesh

Sowing of chickpea in the heavy‐textured soils of north‐west Bangladesh with minimum tillage technology aims to increase the timely planting of large areas during a relatively short sowing window before soil water deficit limits germination and emergence. However, the seedbed conditions into which chickpea is sown need to be better quantified, so that limiting factors which affect germination and emergence can be identified. Two of the soil physical characteristics of importance are soil water and aeration. Growth cabinet studies have identified the fastest germination and emergence of chickpea on representative soils for this area at gravimetric water contents of 17–18 %, whilst soil water contents above and below this delayed germination and emergence. Emergence was recorded at soil water potentials between field capacity (?10 kPa) and wilting point (?1500 kPa). Emergence was possible at lower soil water potentials in the finer textured soil, whilst in coarser textured soil, emergence was still possible at higher soil water potentials.     

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.     

基于叶气温差的生育中期冬小麦水分亏缺诊断研究

为了获取叶片尺度基于叶气温差的冬小麦生育中期水分亏缺诊断阈值,分析了冬小麦叶气温差的典型日变化及其与土壤水分、空气温度及太阳辐射等因子的相互关系,揭示了冬小麦叶气温差对光合气体交换参数的影响,确定了冬小麦叶片水分利用效率较适宜的非气孔限制值及叶气温差范围。结果表明,冬小麦叶气温差在不同的土壤水分条件下表现出不同的日变化规律,随光量子通量增加而升高,随土壤水分、气温增加而降低;4、5和6月冬小麦叶片水分利用效率较适宜的非气孔限制值范围分别为0.7~1.3、1.1~2.0和0.9~1.5,叶气温差控制范围分别为-1.2~0.4、-1.5~-1和-1.25~-0.9℃。