全球变化中氮沉降日益严重,已对森林生态系统的各个过程产生了重要影响。因此,通过研究氮添加对森林生态系统土壤碳输出的影响,对分析全球变化背景下土壤碳吸存具有重要意义。对黑龙江省帽儿山实验林场白桦(Betula platyphylla)次生林,...全球变化中氮沉降日益严重,已对森林生态系统的各个过程产生了重要影响。因此,通过研究氮添加对森林生态系统土壤碳输出的影响,对分析全球变化背景下土壤碳吸存具有重要意义。对黑龙江省帽儿山实验林场白桦(Betula platyphylla)次生林,以及水曲柳(Fraxinus mandschurica)、红松(Pinus koraiensis)、长白落叶松(Larix olgensis)人工林通过2年氮添加(对照(0 kg N hm^-2 a^-1),低氮(50 kg N hm^-2 a^-1),中氮(100 kg N hm^-2 a^-1)和高氮(150 kg N hm^-2 a^-1))试验,测定根生物量密度、土壤微生物量碳浓度、土壤呼吸速率及温、湿度敏感性等指标,旨在探讨森林生态系统土壤呼吸对氮添加的短期响应。结果表明:(1)低氮处理对白桦和水曲柳林土壤呼吸速率影响不显著,但显著提高了红松和长白落叶松林土壤呼吸速率;水曲柳林分中高氮处理土壤呼吸速率显著降低于低氮和中氮处理,而其他林分高氮处理土壤呼吸速率仅显著低于低氮处理。(2)氮添加处理下,4种林分中林分土壤呼吸速率与根生物量密度呈极显著正相关,Pearson相关系数为0.81。(3)低氮处理下5 cm和10 cm处土壤呼吸温度敏感性系数Q10值较CK处理分别提高了2.65%和3.12%,高氮处理较CK处理分别降低了6.29%和5.46%。但氮添加处理对土壤呼吸和土壤湿度间的相关性无影响。综上所述,阔叶林与针叶林土壤呼吸速率对氮添加的响应存在差异。根生物量密度是影响不同林分土壤呼吸对短期氮添加响应的主要因素,同时氮添加处理显著改变了土壤温度敏感性系数。展开更多
A simple hydrodynamic model based on two-fluid theory, taking into account the effect of discrete particles on both the gas- and solid-phase momentum equations, was used to numerically investigate the pressure fluctua...A simple hydrodynamic model based on two-fluid theory, taking into account the effect of discrete particles on both the gas- and solid-phase momentum equations, was used to numerically investigate the pressure fluctuation characteristics in a gas-solid fluidized bed with the aid of CFX 4.4, a commercial CFD software package, by adding user-defined Fortran subroutines. Numerical simulations together with typical experimental measurements show that pressure fluctuations originate above the distributor when a gas pulse is injected into the fluidized bed. The pressure above the bubble gradually increases due to the presence of a rising bubble. When the bubble passes through the bed surface, the pressure near the bed surface gradually decreases to a lower value. Moreover, the pressure signals in the bubbling fluidized beds show obviously periodic characteristics. The major frequency of pressure fluctuations at the same vertical position is affected slightly by the operating gas velocity, and the amplitude of pressure fluctuations is related to both the operating gas velocity and the vertical height. In this study, the influence of the operating gas velocity on the pressure wave propagation velocity can be ignored, and only two peak frequencies in the power spectrum of the pressure fluctuations are observed which are associated with the bubble formation above the distributor and its eruption at the bed surface.展开更多
文摘全球变化中氮沉降日益严重,已对森林生态系统的各个过程产生了重要影响。因此,通过研究氮添加对森林生态系统土壤碳输出的影响,对分析全球变化背景下土壤碳吸存具有重要意义。对黑龙江省帽儿山实验林场白桦(Betula platyphylla)次生林,以及水曲柳(Fraxinus mandschurica)、红松(Pinus koraiensis)、长白落叶松(Larix olgensis)人工林通过2年氮添加(对照(0 kg N hm^-2 a^-1),低氮(50 kg N hm^-2 a^-1),中氮(100 kg N hm^-2 a^-1)和高氮(150 kg N hm^-2 a^-1))试验,测定根生物量密度、土壤微生物量碳浓度、土壤呼吸速率及温、湿度敏感性等指标,旨在探讨森林生态系统土壤呼吸对氮添加的短期响应。结果表明:(1)低氮处理对白桦和水曲柳林土壤呼吸速率影响不显著,但显著提高了红松和长白落叶松林土壤呼吸速率;水曲柳林分中高氮处理土壤呼吸速率显著降低于低氮和中氮处理,而其他林分高氮处理土壤呼吸速率仅显著低于低氮处理。(2)氮添加处理下,4种林分中林分土壤呼吸速率与根生物量密度呈极显著正相关,Pearson相关系数为0.81。(3)低氮处理下5 cm和10 cm处土壤呼吸温度敏感性系数Q10值较CK处理分别提高了2.65%和3.12%,高氮处理较CK处理分别降低了6.29%和5.46%。但氮添加处理对土壤呼吸和土壤湿度间的相关性无影响。综上所述,阔叶林与针叶林土壤呼吸速率对氮添加的响应存在差异。根生物量密度是影响不同林分土壤呼吸对短期氮添加响应的主要因素,同时氮添加处理显著改变了土壤温度敏感性系数。
基金support from National Basic Research Program of China(No.2009CB219801)National Natural Science Foundation of China(No.20976191)+1 种基金International Cooperative Program of Guizhou Province([2009]700110)Program for New Century Excellent Talents in University(NCET-09-0342)
文摘A simple hydrodynamic model based on two-fluid theory, taking into account the effect of discrete particles on both the gas- and solid-phase momentum equations, was used to numerically investigate the pressure fluctuation characteristics in a gas-solid fluidized bed with the aid of CFX 4.4, a commercial CFD software package, by adding user-defined Fortran subroutines. Numerical simulations together with typical experimental measurements show that pressure fluctuations originate above the distributor when a gas pulse is injected into the fluidized bed. The pressure above the bubble gradually increases due to the presence of a rising bubble. When the bubble passes through the bed surface, the pressure near the bed surface gradually decreases to a lower value. Moreover, the pressure signals in the bubbling fluidized beds show obviously periodic characteristics. The major frequency of pressure fluctuations at the same vertical position is affected slightly by the operating gas velocity, and the amplitude of pressure fluctuations is related to both the operating gas velocity and the vertical height. In this study, the influence of the operating gas velocity on the pressure wave propagation velocity can be ignored, and only two peak frequencies in the power spectrum of the pressure fluctuations are observed which are associated with the bubble formation above the distributor and its eruption at the bed surface.
