雷暴冲击风风洞设计及流场测试

鉴于雷暴冲击风试验装置的特殊性以及与低速直流风洞的共通性,参考低速直流风洞的设计方法设计完成了试验装置的洞体结构,并制作了具有调节功能的平板来模拟地面。通过调节平板,该装置能够同时改变冲击风强度、直径、射流高度、入射倾角等冲击风参数。试验测得稳态条件下射流口下竖向风速分布,以及沿竖向分布和水平分布的水平风速,研究了水平距离、高度及冲击风参数的影响。研究结果表明:最大水平风速出现的高度与其水平位置有关;射流速度Vjet与射流直径Djet在一定范围内对试验结果影响不大;射流高度h与入射倾角α对冲击风的流场有明显影响。

土壤增温和氮沉降对杉木幼树细根生物量的影响

全球变化背景下研究增温和养分有效性对细根生物量的影响,对于理解林木养分吸收、生产力和碳吸存具有重要意义。选择杉木为研究对象,通过在福建省三明市陈大镇国有林场内设置土壤增温和氮沉降双因子试验,研究杉木幼树不同月份细根生物量的变化,结果发现:1)土壤增温、氮沉降分别对总细根生物量有显著的抑制和促进作用,土壤增温与氮沉降的交互作用对总细根生物量则无显著影响。2)增温对4月、7月、11月份细根总生物量均有极显著影响,增温对细根总生物量的抑制效应以7月最大;氮沉降对7月和11月细根总生物量有显著影响,7月份的促进作用大于11月份。3)土壤增温对0~1 mm细根生物量的抑制作用大于1~2 mm细根,表明0~1 mm根系对增温的响应更加敏感。4)土壤增温对表层0~10 cm细根生物量的抑制作用大于较深层的细根生物量;而氮沉降只对表层土壤细根生物量有显著促进作用,表明土壤增温和氮沉降均能显著改变细根的垂直分布。结论表明,土壤增温显著抑制细根生物量,而氮沉降显著促进细根生物量,并引起细根生物量在不同径级、不同土层分配格局的变化,从而可能对杉木适应性和生长产生影响。

Numerical simulation of a horizontal sedimentation tank considering sludge recirculation

Most research conducted on the concentration distribution of sediment in the sedimentation tank does not consider the role of the suction dredge. To analyze concentration distribution more accurately, a suspended sediment transportation model was constructed and the velocity field in the sedimentation tank was determined based on the influence of the suction dredge. An application model was then used to analyze the concentration distribution in the sedimentation tank when the suction dredge was fixed, with results showing that distribution was in accordance with theoretical analysis. The simulated value of the outlet concentration was similar to the experimental value, and the trends of the isoconcentration distribution curves, as well as the vertical distribution curves of the five monitoring sections acquired through simulations, were almost the same as curves acquired through experimentation. The differences between the simulated values and the experimental values were significant.

桂林会仙喀斯特湿地芦苇群落土壤养分及微生物活性

为探讨桂林会仙喀斯特湿地芦苇植物群落土壤养分垂直变化趋势和微生物活性特征,测定0~80 cm剖面土壤碳、氮、磷含量,微生物生物量碳(MBC)、氮(MBN)、磷(MBP)以及基础呼吸(BR)、呼吸势(PR)、微生物熵(qMB)和代谢熵(qCO_2)等微生物活性指标,分析土壤养分含量与微生物活性特征的相关性。结果表明:(1)土壤总碳(TC)、有机碳(SOC)、无机碳(SIC)、全氮(TN)、有机氮(Org-N)均随着土壤深度的增加而减少,土壤速效氮(AN)、铵态氮(NH_4^+-N)、硝态氮(NO_3^--N)、全磷(TP)、速效磷(AP)、有机磷(Org-P)和无机磷(Inorg-P)含量在下层土壤中有所波动;SOC占TC含量比例较高,Org-N在TN中所占比例较大,Inorg-P含量略高于Org-P含量;(2)MBC、MBN、MBP主要集中在0~30 cm土层,且随剖面深度的增加,三者均逐渐降低,且土壤MBC与SOC、MBN与TN、MBP与TP均呈极显著正相关关系(P<0.01);(3)BR和PR均随土壤深度的增加而显著降低,而qMB随着土层深度的增加先升高再降低,qCO_2的垂直变化整体呈下降趋势,但在中间土层间有所波动;(4)会仙喀斯特湿地芦苇群落土壤养分和微生物活性各指标之间均呈极显著正相关关系,土壤微生物活性特征是反映会仙喀斯特湿地土壤质量状况的重要指标。

Vertical and seasonal distribution of flying beetles in a suburban temperate deciduous forest collected by water pan trap

Vertical and seasonal distributions of flying beetles were investigated in asuburban temperate deciduous forest in Kanazawa, Japan using water pan traps to determine the abundance and composition among vertical strata, change in the abundance and composition through seasons and determinant factors in generating the distributions. Traps were placed at three levels (0.5 m, 10 m, and 20 m above ground) on a tower. Samplings were carried out seasonally from May to November in 1999 and 2000. Variations in the abundance of flying beetles were observed from different layers. The results showed that the abundance and composition of flying beetles varied among strata and seasons. In both 1999 and 2000,Elateridae was consistently most abundant in the bottom layer, while Attelabidae and Cantharidae were most abundant in the upper layer. In 1999, Eucnemidae and overall scavengers were most abundance in the bottom layer, but results were not consistent with those in 2000. In general, the abundance of herbivores reaches a peak in the early season(May/June) and decreases in the following months. Peaks of abundance in predators vary vertically. In the bottom layer a peak was observed in the early season (May/June), while in the upper layer this was observed in July. Scavengers had two peaks, in May/June and September. These patterns indicated that vertical distributions in the abundance of differentfeeding guilds varied through seasons.