北方稻田生态系统养分渗漏规律研究

 1994～ 1 996年开展了 5种不同模式水稻田生态系统主要养分 N、P、K在整个生育期间随渗漏水淋失规律的研究。结果表明 :不同模式的水稻田生态系统中 ,淋失的 N素养分主要以 NO- 3- N为主 ,NH+ 4 - N淋失仅占很少部分 ,并且随着深度的增加 ,NO- 3- N的淋失逐渐增大 ,而NH+ 4 - N的淋失则逐渐减小。淋失的 P、K养分量很小 ,且随深度的变化其变化量亦不大     

长期施用不同有机肥对土壤各粒级复合体中C、N、P含量与分配的影响

 通过田间试验研究了长期定位施用不同有机肥种类对土壤各粒级复合体组成及其中C、N、P含量与分配的影响。结果表明 ,经过 1 4年 2 9茬连续施肥 ,土壤的复合体组成较对照发生了改变 ,0～ 2 μm粒级的含量减少 ,2～ 1 0 μm粒径颗粒所占的比重增加 ,其它粒级变化较小。不同粒级复合体中有机碳、全氮及全磷含量的高低顺序为 :<2μm>2～ 1 0μm>50～ 1 0 0μm >1 0～50 μm,尽管 1 0～ 50 μm粒级有机碳、全氮与全磷的含量都最低 ,但因该粒级占土壤固相的比重最多 ,因此该粒级中 C、N、P对土壤肥力的贡献较大。长期连续施肥后土壤及不同粒级中 C、N、P的含量都增加 ,但不同元素在不同粒级中的增幅因肥料种类而异。从分配系数上看 ,长期施入土壤的N、P肥主要进入 2～ 1 0 μm粒级的颗粒中 ,说明该粒级对土壤养分的循环、转化和保存起重要作用     

PP333对中晚熟水蜜桃品种生长结果影响的研究

对3个中晚熟品种进行不同浓度PP333处理,每品种设每株叶面喷施PP3338000mg/L、10000 mg/L、12000 mg/L和喷清水对照4个处理,单株为一小区,重复3次,随机区组设计,处理1分 2次喷,第一次在5月9日,第二次在6月9日,其余在5月9日喷1次。研究表明,PP333能极显著地抑制枝梢生长。从控制枝梢生长、产量提高、果实形状及圆整度、花芽形成等综合性状分析,4年生大团蜜露以每株喷PP33312000 mg/L、5年生湖景蜜露和6年生西浦1号以每株PP3338000 mg/L喷2次的处理效果最好。     

植物生长调节剂对延边地区不同基因型 烤烟化学成分的影响

以烤烟(Nicotiana tobacum L.)品种吉烟9号和云烟87为试材,研究了植物生长调节剂对不同基因型烤烟化学成分的影响。试验结果表明,植物生长调节剂对不同基因型烤烟化学成分影响不同,其中云烟87表现好于吉烟9号,并以云烟87品种打顶当天喷施植物生长调节剂各化学成分协调性最好,有利于改善烟叶内在品质。     

饲料中豆粕蛋白替代鱼粉蛋白对花(鱼骨)生长的影响

配制豆粕蛋白对鱼粉蛋白的替代量分别为:0、12.5%、25%、37.5%、50%、62.5%和75%的7种等氮等能的半精制饲料,饲养初始体重为(2.25±0.01)g的7组(三重复)花(鱼骨)6周,以评估花(鱼骨)饲料中豆粕的适宜用量.试验结果表明:豆粕蛋白对鱼粉蛋白替代量为75%饲料组的鱼体末体重和增重率均显著低于其它6组饲料组(P＜0.05),而其它6组饲料组间的鱼体末体重和增重率无显著差异(P＞0.05),各饲料组间花(鱼骨)的存活率、饲料系数、肥满度、脏体比、肝体比及蛋白质积累没有显著差异(P＞0.05),花(鱼骨)全鱼粗脂肪含量随着饲料中豆粕蛋白含量的增加而降低,而豆粕蛋白对鱼粉的替代对全鱼水分、粗蛋白、灰分无显著影响(P＞0.05),本实验花(鱼骨)配合饲料中豆粕蛋白对鱼粉蛋白的最大替代量为625%.     

Gate-variable optical transitions in graphene

Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions and that their optical transitions can be substantially modified through electrical gating, much like electrical transport in field-effect transistors. This gate dependence of interband transitions adds a valuable dimension for optically probing graphene band structure. For a graphene monolayer, it yields directly the linear band dispersion of Dirac fermions, whereas in a bilayer, it reveals a dominating van Hove singularity arising from interlayer coupling. The strong and layer-dependent optical transitions of graphene and the tunability by simple electrical gating hold promise for new applications in infrared optics and optoelectronics.     

Effects of sheet and rill erosion on soil aggregates and organic carbon losses for a Mollisol hillslope under rainfall simulation

Purpose

Characterizations of soil aggregates and soil organic carbon (SOC) losses affected by different water erosion patterns at the hillslope scale are poorly understood. Therefore, the objective of this study was to quantify how sheet and rill erosion affect soil aggregates and soil organic carbon losses for a Mollisol hillslope in Northeast China under indoor simulated rainfall.

Materials and methods

The soil used in this study was a Mollisol (USDA Taxonomy), collected from a maize field (0–20 cm depth) in Northeast China. A soil pan with dimensions 8 m long, 1.5 m wide and 0.6 m deep was subjected to rainfall intensities of 50 and 100 mm h^?1. The experimental treatments included sheet erosion dominated (SED) and rill erosion dominated (RED) treatments. Runoff with sediment samples was collected during each experimental run, and then the samples were separated into six aggregate fractions (0–0.25, 0.25–0.5, 0.5–1, 1–2, 2–5, >?5 mm) to determine the soil aggregate and SOC losses.

Results and discussion

At rainfall intensities of 50 and 100 mm h^?1, soil losses from the RED treatment were 1.4 and 3.5 times higher than those from the SED treatment, and SOC losses were 1.7 and 3.8 times greater than those from the SED treatment, respectively. However, the SOC enrichment ratio in sediment from the SED treatment was 1.15 on average and higher than that from the RED treatment. Furthermore, the loss of <?0.25 mm aggregates occupied 41.1 to 73.1% of the total sediment aggregates for the SED treatment, whereas the loss of >?0.25 mm aggregates occupied 53.2 to 67.3% of the total sediment aggregates for the RED treatment. For the organic carbon loss among the six aggregate fractions, the loss of 0–0.25 mm aggregate organic carbon dominated for both treatments. When rainfall intensity increased from 50 to 100 mm h^?1, aggregate organic carbon loss increased from 1.04 to 5.87 times for six aggregate fractions under the SED treatment, whereas the loss increased from 3.82 to 27.84 times for six aggregate fractions under the RED treatment.

Conclusions

This study highlights the effects of sheet and rill erosion on soil and carbon losses at the hillslope scale, and further study should quantify the effects of erosion patterns on SOC loss at a larger scale to accurately estimate agricultural ecosystem carbon flux.

     

重金属对水稻田土壤中藻类数量和种类的影响

研究表明水稻田土壤中藻类种群丰富,其中蓝藻11属、硅藻5属、绿藻7属、裸藻1属,数量上以蓝藻占优势,硅藻次之,绿藻、裸藻很少。经重金属铜、镍、铅、锌分别处理的土壤样品藻类数量变化很大,在低浓度时起促进作用,高浓度时起抑制作用,其临界值为铜10mg·kg~(-1),锌100mg·kg~(-1),镍>100mg·kg~(-1)。多种金属混合总体毒害增加,但铜、铅、毒害呈减弱趋势。除铜以外,这些重金属对藻类种群结构未有剧烈的影响,但铜在高浓度时对蓝藻的抑制作用比对硅藻的抑制作用强烈。     

不同储藏条件下稻谷脂肪酸值变化和霉变相关性研究

对不同水分、温度下模拟储藏的晚粳稻谷和晚籼稻谷进行定期的脂肪酸值测定和霉变情况观察。结果表明:储藏温度越高,稻谷含水量越大,其脂肪酸值上升速度越快,也越容易发生霉变。相比较而言,含水量分别为14.5%、13.5%晚粳稻谷和晚籼稻谷,在20℃储藏3个月,脂肪酸值变化很小,也未发生霉变。在相同储藏温度下,同一水分晚粳稻谷的脂肪酸值比晚籼稻谷更容易上升,也更容易发生霉变。脂肪酸值与稻谷霉变相关,一般而言,当稻谷脂肪酸值超过25 mgKOH/100g,开始霉变,所以脂肪酸值可作为稻谷是否发生霉变的指标。     

西宁盆地黄土区荷载条件下植被护坡力学效应

为探讨西宁盆地黄土区边坡在荷载条件下植物根系对边坡稳定性的影响,该项研究以西宁盆地西山长岭沟流域为试验区,在自建边坡上种植草本植物垂穗披碱草（Elymus nutans）和灌木植物柠条锦鸡儿（Caragana korshinskii）,通过在边坡坡顶施加载荷,边坡坡面布设位移计与土压力盒的方式,监测荷载条件下边坡坡面土体位移与土压力变化;在此基础上,对边坡植被根-土复合体开展剪切试验,分析荷载条件下边坡坡面不同位置处根-土复合体抗剪强度及其变化特征。试验结果表明：在坡顶荷载条件下,在边坡相同位置处的根-土复合体粘聚力c值均大于施加载荷前;3种植物边坡的根-土复合体粘聚力c值均大于相同条件的未种植素土边坡;在荷载条件下,组合植被边坡的坡面土体位移量显著小于单一植被边坡和素土边坡,组合植被边坡在竖直和水平方向的位移量与草本植被边坡相比减小1.60～1.77 mm,与灌木植被边坡相比减小3.78和4.11 mm,与素土边坡相比减小7.39和6.29 mm。研究结果对防治高寒半干旱地区坡面水土流失、浅层滑坡等地质灾害,具有参考价值和指导意义。