Temperature responses of NO and N2O emissions from boreal organic soil

Both NO and N₂O are produced in soil microbial processes and have importance in atmospheric physics and chemistry. In recent years several studies have shown that N₂O emissions from organic soils can be high at low temperatures. However, the effects of low temperature on NO emissions from soil are unknown. We studied in laboratory conditions, using undisturbed soil cores, the emissions of NO and N₂O from organic soils at various temperatures, with an emphasis on processes and emissions during soil freezing and thawing periods. We found no soil freezing- or thawing-related emission maxima for NO, while the N₂O emissions were higher both during soil freezing and thawing periods. The results suggest that different factors are involved in the regulation of NO and N₂O emissions at low temperatures.     

覆盖对盐渍土壤冻融特性与秋浇灌水质量的影响

在河套灌区进行不同覆盖措施秋浇田间冻融试验,研究其对盐渍土壤冻融特性及秋浇灌水质量的影响,试验设5个处理,分别为秸秆覆盖量0.9kg/m2(F0.9)、秸秆覆盖量0.6kg/m2(F0.6)、玉米整秆覆盖(YZ)、地膜覆盖(DM)、未覆盖(CK)。研究表明:覆盖秋浇后,不同地面覆盖的输热能力对地层的热响应有着不同的影响,不同覆盖影响了土壤冻结融化推进过程,改变了土壤冻结深度对气温负积温的响应关系,通过初步确定冻结期冻土深度与负积温变化的定量关系,可用气温负积温来判断和预测冻结期内土壤冻结深度的变化。从冻融期结束后春玉米播期的土壤水、盐、热3方面综合考虑不同地面覆盖对秋浇灌水质量的影响,各覆盖处理均较CK显著提高了春玉米播期0~10、0~40和0~120cm的土壤储水量,但覆盖使得土层0~20cm土壤含水率偏高,不利于春玉米播种及出苗。覆盖处理均较CK显著降低了表层0~10cm及耕层0~40cm土壤含盐量,整秆覆盖YZ的控盐效果最好。地膜覆盖下春玉米的适宜播期较CK提前了7d,而秸秆覆盖较CK延后了6~7d。覆盖措施显著提高了玉米的出苗率,处理YZ与F0.9出苗率显著高于F0.6和DM。     

冷冻-溶解联合外源酶处理香草兰鲜豆荚对香气成分的影响研究

香草兰是兰科多年生藤本攀缘植物,经过发酵后散发出多种芳香成分成为重要的风味原料。然而,传统发酵生香时间长,香气成分转化率低。本试验考察冷冻-溶解联合不同外源酶处理对香草兰鲜豆荚主要香气成分的影响。结果表明：外源酶不仅可以提高香兰素的含量,还可提高其前体物质-葡糖香草醛的转化率。在此基础上,对比空白样品,所有冷冻-溶解联合外源酶处理后的香草兰中香兰素、对羟基苯甲醛、对羟基苯甲酸和香兰酸含量均显著增加,经过纤维素酶-果胶酶-β葡萄糖苷酶处理后的香兰素、对羟基苯甲醛、对羟基苯甲酸和香兰酸含量最高为5.660％、0.089％、0.069％和0.101％;相比于传统发酵和普通外源酶处理,所有冷冻-溶解联合外源酶处理香草兰鲜豆荚均显著增加香兰素含量（p<0.05）,而纤维素酶-果胶酶-β葡萄糖苷酶、果胶酶-β葡萄糖苷酶、纤维素酶-β葡萄糖苷酶、纤维素酶-果胶酶、果胶酶显著增加对羟基苯甲醛、对羟基苯甲酸和香兰酸含量（p<0.05）。     

冻融作用对农田黑土有机氮组分的调控效应

为深入了解非生长季农田土壤有机氮库组成及转化特征,采用Bremner氮素分级法研究了室内模拟冻融条件下(冻融温度、冻融频数、水分含量)农田黑土有机氮组分含量的变化行为。结果表明:冻融作用对农田黑土有机氮组分及其转化过程影响显著,氨态氮和氨基酸氮是土壤酸解有机氮的主要组分。随着冻结温度降低,土壤氨基酸氮含量显著增加,氨态氮和未知氮含量均显著降低,而氨基糖氮含量变化行为因融化温度而异。随着融化温度升高,土壤酸解有机氮组分无规律性变化。随着冻融频数增加,冻融土壤氨基酸氮含量显著降低,未知氮含量显著增加,氨态氮含量先增加后降低,而氨基糖氮含量则无显著性变化。随着水分含量增加,冻融土壤氨态氮和未知氮含量均显著增加,这与氨基酸氮的变化趋势正好相反,而氨基糖氮含量则无显著性变化。可见,较大的冻融温差、适宜的冻融频数和水分含量是影响土壤有机氮库转化的主要驱动因子。冻融作用能够提高土壤酸解有机氮中氨态氮和氨基酸氮的含量及其分配比例,增加土壤可矿化氮量,促进土壤氮素转化,有利于土壤有效氮的累积,为春季作物生长提供足够的氮素。     

景电灌区次生盐渍化土壤冻融特征

通过对景电灌区一个冻融周期的现场观测,发现盐渍化土壤冻结期缩短,冻结深度减小,冻结起始位置不是地表,而是位于地表以下某个深度,这导致在冻结发展期间有两个冻结锋面出现,使水热盐动态更为复杂。     

运用液态水分信息分析土壤的冻融特性(英文)

本文运用从TDR数据估算得到的液态水分量分析了内蒙古河套灌区土壤的冻融行进过程。根据液态水分量的变化,将冻土层区分为"完全冻结层"和"部分冻结层"。一方面,完全冻结层保持着0.05～0.1cm3cm-3的液态水分量垂直向下推进,而在其下方30～40cm厚的土壤为部分冻结土层,液态水分量出现了由0.1cm3cm-3到0.35～0.4cm3cm-3的剧烈变化,这部分土层随着时间的推移平行向下方推进的趋势。融解过程的速度要比冻结过程大得多。分析结果表明,部分冻结层在4月末到5月初,深度为70cm～90cm的剖面依然存在。     

Kinetics of inorganic and organic P release from red clover (Trifolium pratense L.) and ryegrass (Lolium multiflorum L.) upon frost or drying

An incubation study with fresh, frozen, and dried clover and rye-grass shoots gathered in autumn was performed in the laboratory (43 days). The aim was to study inorganic and organic phosphorus (P) release from plant material during decomposition without soil. Plant materials (2?cm size) were mixed with small glass beads and placed in large syringes for consecutive water extractions on 7 occasions. Leachates were analysed for inorganic and total P. At the first leaching event, 8% of total crop P was released from fresh, 24% from frozen and 27% from dried plant material. During decomposition, both inorganic and organic P was released following first order kinetics, with grass releasing mostly inorganic P and clover mostly organic P. After 43 days, 42%–50% of total crop P from fresh, 49%–51% from frozen and 57%–69% from dried material was released, with significant differences between treatments. Using the results in calculations on field scale showed that P released from overwintering crops under cold climate conditions can amount to several kg P ha^?1. Thus, senescence of overwintering aboveground biomass can be a significant source for P leaching from soils.     

冻融交替对农田棕壤氮素转化过程的调控效应

通过室内培养模拟试验,研究了农田棕壤可溶性氮(可溶性无机氮,DIN;可溶性有机氮,DON;可溶性全氮,DTN)含量、微生物生物量氮(MBN)含量和净氮矿化速率(NNMR)对不同冻融温度和冻融频数的响应。结果表明:冻结温度和冻融频数是影响农田棕壤氮素转化过程的主要因子。随着冻结温度降低,土壤NO3–-N、NH4+-N、DIN、DON、DTN和NNMR均显著增加,而MBN先降低后增加。随着冻融频数增加,土壤NO3–-N、NH4+-N、DIN和DTN均显著增加,这与NNMR的变化趋势正好相反;MBN则呈现降低–增加–降低的变化趋势,这与DON的变化正好相反。可见,冻融交替显著促进非生长季农田棕壤的氮素转化,增加土壤无机氮含量,提高土壤供氮能力。     

地表水中浮游植物叶绿素a提取方法的改进研究

[目的]优化地表水中浮游植物叶绿素a的提取方法。[方法]以新配制的90%丙酮为提取液,在低温与室温下反复地冻融浮游植物以破碎细胞,多次震摇后冷藏静置以提取叶绿素a,并与规范法进行对比。[结果]改进法提取的叶绿素a含量较规范法明显提高,且重复测定的精密度较高。两种方法的测定结果存在明显差异,但在含量测定的趋势上具有较强的一致性。改进法可以满足750 nm处吸光值低于0.005的要求,而规范法不能。镜检表明,改进法的植物细胞破碎情况比规范法更佳。[结论]改进法提取浮游植物叶绿素a含量明显高于规范法且重复性较好,具有人为误差小、稳定性好、提取率高、结果准确、操作简便安全等特点。