木材干燥导水系数和换水系数的研究

木材(板、方材)的导水系数和换水系数是反映木材干燥或存放过程中水分迁移的重要物性参数。然而,我国对木材导水系数和换水系数的研究和测定工作十分有限。木材干燥有关的理论计算中,常用原苏联的数据。由于这些数据本身可能存在的误差及用于我国树种的可靠程度难以估计,故使理论结果的实际运用受到限制。本文采用等厚试件系数分离法研究和测定了木材干燥过程动态导水系数和换水系数。     

水稻中系8541与中系8240光合特性的比较研究

本文通过光合作用参数的测定,详细的研究了中系8541和8240两种不同产量水平的水稻品种的光合特性.论述了在含等量叶绿素的条件下,中系8541和中系8240之间在对光谱的吸收、叶片的光合作用量子转化效率,叶绿体的PSⅡ(光系统Ⅱ)潜在活性(Fv/F_0)和原初光能转化效率(Fv/Fm等的主要区别.实验结果说明,上述各光合作用参数中系8541都优于中系8240.不仅如此.在Mg~(2+)作用下,Fv/Fo和Fv/Fm比值的提高以及Mg~(2+)对两个光系统激发能分配的调节能力中系8541也强于中系8240.     

亚硫酸氢钠处理减轻低温对温州蜜柑光合作用的影响

 低温胁迫使温州蜜柑叶片的净光合速率(Pn)、光系统Ⅱ的光化学效率(Fv/Fm)及光合电子传递速率(ETR)下降，反映跨膜质子动力势的叶绿素毫秒延迟发光(ms-DIE)减弱，叶片中的ATP含量降低。低温胁迫前，用NaHSO₃ 5 mmol/L涂于叶片表面，可使处理植株叶片的Pn和Fv/Fm分别少下降了11.5%和11.6%，ETR和ATP含量几乎没有下降，ms-DLE的下降幅度减少。可见，在柑橘上施用NaHSO₃能够减轻短期低温对光合机构及光合作用的影响。     

Effect of cyclodextrin diallyl maleate on methane production, ruminal fermentation and microbes in vitro and in vivo

Effects of β‐cyclodextrin diallyl maleate (CD‐M) on methane production, ruminal fermentation and digestibility were studied both in vitro and in vivo. In in vitro study, diluted ruminal fluid (30 mL) was incubated anaerobically at 38°C for 6 and 24 h with or without CD‐M using hay plus concentrate (1.5:1) as a substrate. The CD‐M was added at different concentrations (0, 1.25, 2.5, 5.0 and 7.5 g/L). The pH of the medium and numbers of protozoa were not affected by the addition of CD‐M. Total volatile fatty acids were increased and ammonia‐N was decreased, molar proportion of acetate was decreased and propionate was increased (P < 0.05) by CD‐M. Methane was inhibited (P < 0.05) by 14–76%. The effect of CD‐M on methane production and ruminal fermentation was further investigated in vivo using four Holstein steers in a cross‐over design. The steers were fed Sudangrass hay and concentrate mixture (1.5:1) with or without CD‐M (2% of feed dry matter) as a supplement. Ruminal proportion of acetate tended to decrease and that of propionate was increased (P < 0.05) 2 h after CD‐M dosing. Total viable counts, cellulolytic, sulfate reducing, acetogenic bacteria and protozoa were unaffected while methanogenic bacteria were decreased (P < 0.05) by CD‐M. The plasma concentration of glucose was increased, whereas that of urea‐N was decreased (P < 0.05). Methane was inhibited (P < 0.05) from 36.4 to 30.1 L/kg dry matter intake by the addition of CD‐M. Apparent digestibilities of dry matter and neutral detergent fiber were not affected while that of crude protein was increased (P < 0.05) in the medicated steers. These data suggested that dietary supplementation of CD‐M decreased methane production and improved nutrient use.     

Effects of cyclodextrin-iodopropane complex on methane production, ruminal fermentation and microbes, digestibility and blood metabolites in steers

The effects when adding cyclodextrin‐iodopropane complex (CD‐IP) to a diet, on ruminal fermentation and microbes, digestibility, blood metabolites and methane production, were evaluated using four Holstein steers in a cross‐over design. The steers were fed Sudangrass hay plus concentrate mixture at a ratio 1.5:1, and CD‐IP (1% of dry matter) was given twice daily by mixing with concentrate mixture. Rumen and blood samples were collected at 0, 2, and 5 h after morning dosing. Ruminal pH and numbers of protozoa were unaffected by CD‐IP treatment. Ruminal molar proportion of acetate was decreased (P < 0.05), and propionate was increased (P < 0.01) at 2 h after CD‐IP dosing. Proportion of butyrate was increased (P < 0.05) and ammonia‐N was decreased (P < 0.05) at 2 and 5 h after CD‐IP dosing. Adding CD‐IP had no effect on the feed intake and digestion of nutrients. Plasma glucose was increased and urea‐N was decreased (P < 0.05) at 2 and 5 h after CD‐IP dosing. Methane production was decreased (P < 0.05) by approximately 18% in the treatment steers. Numbers of methanogenic bacteria were decreased (P < 0.05), while total viable counts, cellulolytic, sulfate reducing and acetogenic bacteria were unaffected. The present results are the first to show that CD‐IP can partially inhibit in vivo ruminal methanogenesis without adverse effects on digestion of nutrients.     

Effects of three short-term pasture allocation methods on milk production,methane emission and grazing behaviour by dairy cows

Two short-term grazing experiments were conducted with Norwegian Red cows. In Exp 1, 24 cows were randomly assigned to one of the following three pasture allocation methods (PAM): weekly pasture allowance (7RG), grazing 1/7 of 7RG each day (1SG), or grazing as 1SG but had access to grazed part of the paddock within one week (1FG). In Exp 2, 7RG was shortened to 5 days (5RG). We hypothesized that PAM will affect sward quality, quantity, intake and production differently. Pasture chemical composition changed with advancing grazing days but were not different between treatments. Pasture intake, milk yield, and methane emission were not affected by PAM. In Exp 1, 7RG cows spent less time on grazing, whereas in Exp 2, 1FG cows spent longer on grazing than others. Patterns observed in sward quality, and behavioural and physiological adaptations of cows to short-term changes in nutrient supply may explain the observed effects.     

More evidence that anaerobic oxidation of methane is prevalent in soils: Is it time to upgrade our biogeochemical models?

Estimating future fluxes of CH₄ between land and atmosphere requires well-conceived process-based biogeochemical models. Current models do not represent the anaerobic oxidation of methane (AOM) in land surface soils, in spite of increasing evidence that this process is widespread. Our objective was to determine whether AOM, or potential AOM, commonly occurs in 20 hydromorphic soils spanning a wide range of chemical properties. Bulk soil samples were collected under shallow water near the shoreline of 15 recently drained fish ponds in southern Bohemia (Czech Republic), as well as from below the water table at 3 peatland locations in northeast Scotland and 2 acid sulfate soils on the southern coast of Finland. Each soil slurry was incubated under both oxic and anoxic conditions, with or without the addition of alternative electron acceptors (SO₄²⁻ and NO₃⁻) or H₂PO₄⁻. Here, “oxic” and “anoxic” conditions refer to anoxic soil respectively incubated in a headspace containing air or argon. Using the isotope dilution method, we determined the gross production and oxidation rates of CH₄ after 2 days incubation under oxic headspace conditions, and after 2, 21 and 60 days incubation under anoxic conditions. Large differences in net CH₄ fluxes were observed between soil types and between incubation conditions. AOM was detected in each of the 20 bulk soil samples, which spanned >6 pH units and 2 orders of magnitude in organic C content. Significant positive relationships were found between AOM and gross CH₄ production rates under anoxic conditions, resulting in AOM rates that were sometimes higher than CH₄ oxidation rates under oxic headspace conditions. There was no relationship between net and gross CH₄ production rates, such that 2 soil types could display similar low net rates, yet conceal very large differences in gross rates. The effects of alternative electron acceptors on AOM were idiosyncratic and resulted in no net trend. We did find, however, a negative effect of SO₄²⁻ and H₂PO₄⁻ on gross CH₄ production rates under anoxic and oxic conditions respectively. Under oxic headspace conditions, CH₄ oxidation was related to soil organic C content. Taken collectively, our results suggest that AOM, or potential AOM, is prevalent over a wide range of soil types, that AOM may contribute substantially to CH₄ oxidation in soils, and that AOM in soils should be integrated to current process-based CH₄ cycling models.     

水分条件对巴音布鲁克高寒湿地CO_2排放的影响

在新疆天山中部巴音布鲁克天鹅湖高寒湿地,以苔草(Carex tristachya)为主要建群种的样地为研究对象,利用英国PP-systems公司生产的便携式土壤呼吸测定系统(CIRAS-2-SRC)研究了不同地表水分条件对天鹅湖高寒湿地夏季土壤CO2排放的影响。结果表明,1)湿润区的生物量大于干燥区;干燥区土壤CO2排放高于湿润区,干燥区土壤CO2排放日变化曲线为单峰曲线,CO2排放最高点出现在当地14:00-16:00,最高值为1.185 0g CO2·m-2·h-1;湿润区土壤CO2排放日变化曲线为双峰曲线,两个峰值分别出现在12:00和16:00,最高值为1.024 0g CO2·m-2·h-1。2)不同水分条件下生物量中凋落物含量影响土壤CO2排放。土壤温度是CO2排放的主要限制因子,且地表干燥区CO2排放与土壤温度的相关性更显著(P0.01)。土壤湿度与CO2排放相关性不显著(P湿润区=0.997,P干燥区=0.409)。     

Mechanisation of organic fertiliser spreading,choice of fertiliser and crop residue management as solutions for maize environmental impact mitigation

The environmental impact of crop production is mainly related to fossil fuels consumption and to fertilisers application. Emissions arising from the spreading of organic and mineral fertilisers are important contributors for impact categories such as eutrophication and acidification. The choice of the fertilisers and of the spreading techniques as well as the crop residues management can deeply affect the environmental impact related to crop cultivation.In this study, seven scenarios describing fertilising schemes characterised by different organic and mineral fertilisers and by different mechanisation were compared. The aim is to evaluate, using the Life Cycle Assessment (LCA) method, how the environmental performances of grain maize production were affected by these different fertilisers schemes. The study was carried out considering a cradle to farm gate perspective and 1 t grain maize was selected as functional unit. Inventory data were collected on a farm located in Po Valley (Northern Italy) during year 2013 and were processed using the composite method recommended by the International Reference Life Cycle Data System (ILCD). The compared scenarios involved organic and mineral fertiliser distribution and were: pig slurry incorporation after >3 days after spreading (BS), fast pig slurry incorporation within 2 h from spreading (AS1), direct soil injection of pig slurry (AS2), pig slurry incorporation (after >3 days) with straw collection (AS3), digestate spreading instead of pig slurry (after >3 days) (AS4), only mineral fertilisers (i.e. urea and superphosphate) distribution (AS5) and only mineral fertilisers (i.e. calcium ammonium nitrate and superphosphate) distribution (AS6).The results were not univocal, since climate and soil conditions as well as physical and chemical fertiliser characteristics differently affected the environmental load, especially for particulate matter formation, terrestrial acidification and terrestrial eutrophication impact categories. AS1 and AS2 showed the most beneficial results for these impact categories (between ↙67% and ↙73% respect to worst scenario). AS6, on the opposite, showed the highest environmental impact for those impact categories mainly affected by energy and fossil fuel consumption (climate change, ozone depletion, human toxicity with carcinogenic effect, particulate matter, freshwater eutrophication, freshwater ecotoxicity and mineral, fossil and renewable resources depletion), categories on which AS3 and AS4 were the best solutions. AS3 was the most impacting for terrestrial acidification and eutrophicationA sensitivity analysis was carried out varying grain maize yield (mostly affected: marine eutrophication) and ammonia volatilisation losses due to organic fertilisers (mainly affected: terrestrial acidification and eutrophication).The achieved results can be useful for the development of ⬓spreading rules⬽ that drive the application of organic fertilisers in agricultural areas where there is an intense livestock activity.     

干燥器法与穿孔萃取法测定中密度纤维板甲醛释放量的相关性研究

分别采用GB 18580标准中的干燥器法和穿孔萃取法检测中密度纤维板的甲醛释放量，并根据两种方法检测出的结果分析其相关性。结果表明，两种检测方法呈显著线性相关。