东北落叶松属植物潜在分布对气候变化的响应

为探索气候变化对东北落叶松属植物的影响,采用logistic回归模型方法与地理信息系统,预测东北落叶松属植物目前以及未来潜在分布范围。结果表明:兴安落叶松在2050年将向北退200km,在2100年进一步向北退缩300km;长白落叶松在2050年向西北推进约200km,2100年继续推进约200 km;华北落叶松在2050年向东北方向推进280 km;2100年继续推进470 km左右。气候变化极大地改变了三种落叶松的适宜分布区。在未来气候条件下,长白落叶松和华北落叶松将可能替代目前占主导地位的兴安落叶松。

Heat capacities and thermodynamic functions of p-chlorobenzoic acid

The heat capacities of p-chlorobenzoic acid were measured in the temperature range from 80 to 580 K by means of an automatic adiabatic calorimeter equipped with a small sample cell of internal volume of 7.4cm(3). The construction and procedures of the calorimetric system were described in detail. The performance of this calorimetric apparatus was evaluated by heat capacity measurements on alpha-Al2O3. The deviations of experimental heat capacities from the corresponding smoothed values lie within +/-0.28 per cent, while the inaccuracy is within +/-0.40 per cent, compared with the recommended reference data in the whole experimental temperature range. A fusion transition at T = 512.280 K was found from the C-p-T curve of p-chlorobenzoic acid. The enthalpy and entropy of the phase transition, as well as the thermodynamic functions {G((T)) - G((298.15))}, {H-(T) - H-(298.15)} and {S-(T) - S-298.15}, were derived from the heat capacity data. The mass fraction purity of p-chlorobenzoic acid sample used in the present calorimetric study was determined to be 0.99935 by fraction melting approach. (C) 2002 Elsevier Science Ltd. All rights reserved.

过量Mg~(2+)对农作物种子萌发特性的影响

[目的]揭示过量Mg2+对玉米和大豆萌发特性的影响。[方法]设0、40、80、120、160、200、240、280、320、360、400 mmol/L11个Mg2+浓度处理,研究不同处理对玉米和大豆发芽势、发芽率、鲜重、干重、根长、株高、茎粗等指标的影响。[结果]随着Mg2+浓度的升高,玉米的发芽被延缓,而大豆发芽率降低明显,达到0.05水平的显著性差异。随着Mg2+浓度升高,玉米和大豆的鲜重和干重降低,但均表现出一定的适应性。玉米和大豆幼根和幼苗生长受Mg2+抑制明显,普遍表现出萎缩、发育不良现象。[结论]过量Mg2+胁迫对不同农作物的发芽势、发芽率影响不同,对农作物的根、茎器官生长毒害作用明显。

过量Mg~(2+)对农作物种子萌发特性的影响(英文)

[Objective] The research aimed to reveal the effects of excessive Mg2+ on the germination characteristics of maize and soybean. [Method] Eleven concentration gradients of Mg2+ including 0,40,80,120,160,200,240,280,320,360 and 400 mmol/L were set up to study the effects of different treatments on such indices as the germination potential,germination rate,fresh weight,dry weight,root length,plant height and stem diameter of maize and soybean. [Result] With the increasing of Mg2+ concentration,the germination of maize delayed and the germination rate of soybean obviously decreased,reaching the significant difference at 0.05 level. When Mg2+ concentration increased,the fresh weight and dry weight of maize and soybean decreased,but maize and soybean showed some adaptability. The growth of radicles and seedlings in maize and soybean were obviously inhibited by Mg2+,and atrophy and dysplasia phenomena appeared. [Conclusion] Excessive Mg2+ stress has different effects on the germination potential and germination rate of different crops and has obvious poisoning effects on the root and stem growth of crops.

吉林白城地区草原栗斑腹巫鸟窝卵数、营巢成功率和繁殖成功率的研究

对分布于吉林白城地区草原生境中栗斑腹巫鸟的窝卵数、营巢成功率和繁殖成功率的初步研究结果表明 ,繁殖期栗斑腹巫鸟种群的平均窝卵数为 5 .0 9± 0 .5 8枚 /巢 ;窝卵数与产卵期、出巢数与产卵期、窝卵数与卵大小之间呈负相关 ,产卵期与孵化率之间存在极显著的负相关关系 ,巢外径与窝卵数之间存在显著的正相关关系 ,巢的其余指标均与窝卵数呈正相关 ;平均孵化期为 12± 0 .4 9d ,孵化率为 36 .3% ,繁殖成功率为 11.11% ;7日龄以上的雏鸟群体大小为 2 .5 6± 1.5 3只 ,栗斑腹巫鸟的雏鸟存活率为 2 7.6 9% .

Rapid world wide depletion of predatory fish communities

Serious concerns have been raised about the ecological effects of industrialized fishing1, 2, 3, spurring a United Nations resolution on restoring fisheries and marine ecosystems to healthy levels4. However, a prerequisite for restoration is a general understanding of the composition and abundance of unexploited fish communities, relative to contemporary ones. We constructed trajectories of community biomass and composition of large predatory fishes in four continental shelf and nine oceanic systems, using all available data from the beginning of exploitation. Industrialized fisheries typically reduced community biomass by 80% within 15 years of exploitation. Compensatory increases in fast-growing species were observed, but often reversed within a decade. Using a meta-analytic approach, we estimate that large predatory fish biomass today is only about 10% of pre-industrial levels. We conclude that declines of large predators in coastal regions5 have extended throughout the global ocean, with potentially serious consequences for ecosystems5, 6, 7. Our analysis suggests that management based on recent data alone may be misleading, and provides minimum estimates for unexploited communities, which could serve as the ‘missing baseline’8 needed for future restoration efforts.

科尔沁沙地黑沙蒿人工植被土壤线虫群落特征

本文针对科尔沁沙地黑沙蒿人工植被土壤线虫的总数、群落组成、营养类群进行了研究。结果表明,随着黑沙蒿种植年限的增加,土壤线虫数量显著增加。不同年限黑沙蒿植被之间土壤线虫总数差异显著(P<0.01)。在本研究中共获得线虫13科19属,其中Acrobeles为优势属。在半流动沙丘生态系统中,植物寄生线虫为优势营养类群;而在黑沙蒿人工植被生态系统中,线虫群落逐渐向以食细菌线虫占优势的方向演替。本实验结果表明,土壤线虫群落结构对退化沙漠生态系统的恢复阶段具有很好的生物指示作用。

紫花苜蓿和短花针茅根系分布与土壤水分研究

以陕北农牧交错带人工草种紫花苜蓿(Medicago sativa L.)和天然草种短花针茅(Stipa breviflora Griseb.)为对象,采用根钻法调查两个草种的根系垂直分布以及刈割后苜蓿根系变化特征,并通过定位观测研究土壤水分动态变化。结果表明:紫花苜蓿和短花针茅根系密度随土壤深度增加而减少,而且均以直径小于等于1 mm的须根为主;0~50 cm土层紫花苜蓿和短花针茅根系量分别占0~100 cm剖面总量的67%和84%。紫花苜蓿和短花针茅根系分布与土壤水分消耗特征吻合。生长旺盛期苜蓿大量消耗0~140 cm土层土壤水分,5-9月平均有效土壤储水不足10 mm;生长季末深层(140~280 cm)土壤储水也逐渐降低,约为裸地储水量的50%。短花针茅0~280cm剖面土壤水分状况明显好于苜蓿地,比苜蓿地多储水100 mm左右;主要消耗浅层(0~50 cm)土壤水分,深层水分利用较少。

硫脲在农业中的研究和应用

硫脲既是一种硝化抑制剂也是一种脲酶抑制剂。国外的一些研究表明,硫脲与尿素或硝铵尿素(UAN)配施能有效抑制土壤中尿素的水解、减少NH3挥发损失和延缓氮素的矿化过程,同时促进作物生长、增加作物产量。

热解吸-气相色谱法测定植物源挥发性有机物

以Tenax-TA、Carboxen 1000和Carbosieve SⅢ为采样管填充料,将植物源挥发性有机物吸附于采样管内,样品通过二次热解吸仪解吸后,随载气进入气相色谱仪,采用氢火焰离子化检测器(FID)测定,建立了利用二次热解吸仪与气相色谱联用技术测定植物挥发性有机物的分析方法。载气N2流速为30 mL/min,60℃下吹扫吸附管2 min,然后在250℃下解吸吸附管5 min,冷却1 min后,在275℃下解吸聚焦管3 min,样品经传输线进入气相色谱。气相色谱载气N2压力为190 kPa,FID检测器温度280℃;进样口温度225℃;初始柱温40℃,停留5 min,以2℃/min升温至120℃,保留1 min,然后以20℃/min升温至200℃,保留10 min。方法重现性好,精密度高,线性相关系数大于0.99;检出限均低于9×10-9g/L;解吸效率大于96%,适用于植物源挥发性有机物的测定。

土地利用方式对潮棕壤磷素剖面分布的影响

采用现场采集土壤样品及室内分析测试,对中国科学院沈阳生态实验站4种土地利用方式的潮棕壤在0～150cm10个土层中全磷的垂直分布、磷储量及碳磷比进行比较研究。结果表明,不同利用方式下土体中全磷平均含量为林地>撂荒地>玉米地>水稻田,各种利用方式土壤全磷含量在0～30cm各层次差异不显著,30cm以下各层次玉米地和撂荒地差异不显著,但60cm以下各层次林地土壤全磷显著高于其他3种利用方式,表明土地利用对磷素的剖面分布产生了明显的影响。4种利用方式在20cm深度土壤磷储量差异不明显,但在100cm和150cm深度,林地和撂荒地显著高于玉米地和水稻田土壤。土壤碳磷比随剖面深度下降而降低,在40cm以下有林地和玉米地高于撂荒地和水稻田的趋势。回归分析表明,各种利用方式下土壤速效磷与全磷有较好的正相关关系,说明供试土壤中速效磷含量受全磷状况的影响较大。