科尔沁温带草甸能量平衡的日季变化特征

利用2011年9月—2012年10月涡度相关数据和气象观测资料,对科尔沁温带草甸能量平衡的日季变化特征进行分析.结果表明:研究区涡度相关系统全年的能量平衡闭合度为0.77,不同时期能量平衡闭合度的大小顺序为:生长季裸土期积雪期.能量平衡各分量日变化均呈单峰曲线形式,净辐射日变化峰值出现在12:00前后,其余分量的峰值出现时间都稍有滞后.净辐射季节变化呈单峰曲线形式,年平均值为5.71 MJ·m-2·d-1.潜热通量季节变化趋势与净辐射相似,年平均值为2.84 MJ·m-2·d-1.感热通量季节变化呈双峰曲线形式,峰值分别出现在4月和9月,年平均值为1.87 MJ·m-2·d-1.土壤热通量的最大值(3.47 MJ·m-2·d-1)出现在4月,9月以后开始转为负值.全年能量平衡各分量收支比例的大小顺序为:潜热通量感热通量土壤热通量,潜热通量、感热通量和土壤热通量分别占净辐射的49.8%、35.8%和3.1%.全年波文比的季节变化近似"U"型,平均值为1.61;生长季数值较小且较为平稳,平均值为0.18;非生长季数值较大且波动较大,平均值为2.39.     

我国亚热带毛竹林生长季能量通量过程及闭合度分析

为探讨我国亚热带毛竹林(Phyllostachys edulis)生长季的能量平衡关系,利用开路涡度相关法,对2011年毛竹林生长季的能量通量的变化特征进行了研究,并应用能量平衡比率法和线性回归2种方法,分析了能量闭合的特点。结果表明,我国亚热带毛竹林生长季的净辐射总量为1738.2 MJ m–2,显热通量为354.3 MJ m–2,潜热通量为1146.0 MJ m–2,土壤热通量为58.9 MJ m–2,土壤为热汇,显热通量占净辐射的20.4%,潜热通量占65.9%,土壤热通量占3.4%。毛竹林生长季的能量闭合度为0.89,月平均闭合度为0.91,但仍有11%的能量不闭合。可见,毛竹林生长季以潜热能量散失形式为主,各能量分量均以净辐射变化为基础,且日变化基本呈单峰型曲线。     

黄土高原农牧交错带稀疏自然植被生态系统的地表能量特征

基于2011-2012年黄土高原农牧交错带稀疏自然植被生态系统的地表能量通量以及气象数据,对该地区能量平衡各分量(净辐射、感热、潜热和土壤热通量)以及波文比进行日、季节动态的特征分析,研究了潜热通量和感热通量对不同强度降雨事件响应程度的差异,并分析了潜热通量和感热通量的主控因子.结果表明:该地区净辐射、感热、潜热和土壤热通量的日、季节动态曲线均为单峰型曲线,净辐射、感热通量、潜热通量和土壤热通量的年平均值分别为78.19、33.32、24.91和2.65 W·m-2.在全年能量收支平衡中,感热通量占净辐射的43％,潜热通量占32％,土壤热通量占3％,表明对于黄土高原农牧交错带自然稀疏灌木生态系统,全年能量主要以感热的形式交换.生长季感热和潜热占净辐射的比例相同(36％);而在非生长季,感热占主导,占净辐射的比例高达54％.潜热通量在强、弱降雨事件发生后明显升高,感热通量则明显下降.潜热通量与净辐射、水汽压差及植被参数均显著相关,感热通量与净辐射及空气温度梯度显著相关.     

亚热带-暖温带过渡区天然栎林的能量平衡特征

利用开路涡度相关系统和常规气象观测仪器观测了我国北亚热带-暖温带气候过渡带(河南南阳)的一片锐齿栎天然林的能量通量及常规气象。以一个完整年(2016年10月—2017年9月)的观测数据为依据,定量分析了此锐齿栎林的能量通量的日变化、季节变化以及各能量分量的分配特征,并计算了能量闭合度以及波文比。结果表明:锐齿栎林观测期间一整年净辐射为2626.17 MJ/m~2,感热通量为867.1 MJ/m~2,潜热通量为1417.25 MJ/m~2,土壤热通量为-2.60 MJ/m~2,土壤为热源;各能量分量日变化基本呈单峰型曲线,季节变化特征明显。非生长季,锐齿栎林的能量主要分配给感热通量,占净辐射的54.18%;生长季,能量主要分配给潜热通量,占净辐射的67.48%。观测期间研究区年降雨量较平均值稍大(1231.8 mm),森林蒸散量为579 mm,仅为降雨量的47%。波文比受森林物候变化影响较大,在非生长季平均值约为2.1,生长季约为0.2。土壤热通量在生长季2017年4—9月份为正值,土壤表现为热汇,其余月份皆为热源。土壤热通量的变化过程主要受净辐射调控,森林物候也起了一定的作用。河南宝天曼锐齿栎森林通量观测站全年能量闭合度为67%,在国际同类观测站的范围之内(55%—99%)。不能完全闭合的原因可能与通量源区面积不匹配、计算能量平衡时忽略冠层热存储等有关。     

亚热带毛竹林生态系统能量通量及平衡分析

利用开路涡度相关系统和常规气象观测仪器,对亚热带(浙江省)毛竹林生态系统2011年的净辐射、显热通量、潜热通量、土壤热通量以及气温、地温、降雨量等气象要素进行了连续观测,定量分析了毛竹林生态系统能量通量的变化和各能量分量的分配特征,并计算了能量闭合度以及波文比。结果表明:毛竹林全年净辐射为2628.00 MJ/m2,显热通量为576.80 MJ/m2,潜热通量为1666.77 MJ/m2,土壤热通量为-7.52 MJ/m2,土壤为热源,各能量分量季节变化明显,日变化基本呈单峰型曲线变化。显热通量占净辐射的22.0%,潜热通量占63.4%,毛竹林生态系统潜热通量为能量散失的主要形式。波文比逐月变化规律不明显,波动较大,在0.07—1.77之间变化,能量平衡比率法得出毛竹林年能量闭合度为0.85,月平均闭合度为0.84,能量闭合度高于线性回归法计算结果,但仍有15%的能量不闭合。     

黄土高原半干旱草地地表能量通量及闭合率

利用兰州大学半干旱气候与环境观测站(简称SACOL站)2008年的湍流、辐射、土壤温度和通量梯度观测资料,分析了地表能量通量的日变化、季节变化及能量分配特征,讨论了典型黄土高原沟壑区土壤热量储存对地表能量闭合率的影响.结果表明:黄土高原半干旱草地全年获得的净辐射约为2.269×103 MJ/m2,感热、潜热和土壤热通量年总量分别为1.210×103 MJ/m2、1.117×103 MJ/m2和0.069×103 MJ/m2;能量平衡各分量季节变化明显,日变化呈单峰型.从各能量分量占净辐射的比例来看,黄土高原半干旱草地净辐射主要以感热形式加热大气.草原生长期的能量闭合率为86.8％,非生长期的能量闭合率为76.5％.与未考虑0-5cm深度的土壤热量储存相比,草原生长期能量闭合率提高了11.3％,非生长期能量闭合率提高了12.0％.     

西双版纳热带季雨林通量分配及能量平衡问题北大核心CSCD

为了探讨我国西双版纳热带季雨林的能量分配和平衡问题,利用涡度相关系统和常规气象仪器的连续监测结果,分析了不同季节的能量通量特征和闭合特点。结果表明,西双版纳热带季雨林全年的净辐射、潜热通量、显热通量、土壤热通量和热储存量分别是4546.07、2453.24、492.22、-10.47和45.93 MJ/m^(2),土壤为热源,潜热年总值占净辐射的54.0%,显热占10.8%,能量以蒸发散为主要的耗损形式。辐射和能量有明显的日变化和季节动态,各能量分量的日变化几乎都呈白天高夜间低的单峰趋势,反照率整体为0.10~0.12,波动不大;波文比季节差异明显,为0~0.8。热带季雨林的全年闭合度为0.67,未考虑热储量时,闭合度为0.51~0.79,考虑热储量为0.53~0.80。可见,在林冠茂密的热带季雨林中,热储量对能量闭合度的贡献不大,忽略热储量并不是导致能量不闭合的主要原因。     

东北阔叶红松林能量平衡特征

采用涡度相关法,结合小气候观测,对东北阔叶红松林的能量平衡特征进行了研究。结果表明,森林全年获得的辐射能量为2.3×109J/m2,平均净辐射(Rn)强度为72.1 W/m2,12月最小,平均为5.8W/m2,6月最大,平均为127 W/m2。除了受太阳高度角的支配,Rn对中小尺度天气变化响应显著。非生长季,森林主要能量支出项为感热通量(H),约占Rn的72%,H最大值出现在5月份;生长季,主要能量支出项为潜热通量(LE),约占Rn的60%,LE最大值出现在7月份。全年因蒸散消耗的能量为1.2×109J/m2,占净辐射的52%,森林蒸散的水量为493mm,占降水量的88%。波文比β近似呈U字型变化,其值受森林物候变化影响显著,在非生长季平均值约为3.0,生长季为0.5左右。土壤热通量(G)在非生长季表现为能量平衡方程的收入项,约占有效能量的5.0%;生长季表现为支出项,约占有效能量的4.0%,其变化过程与土壤温度梯度及叶面积指数密切相关。长白山通量观测站能量平衡收支闭合度为86%,不闭合的原因有待于进一步的研究。     

内蒙古温带荒漠草原生态系统水热通量动态

基于2008年全年内蒙古温带荒漠草原的水热通量观测数据,对荒漠草原水、热通量的日、季动态进行了分析.结果表明：温带荒漠草原感热通量和潜热通量的日动态均呈单峰型曲线,在12:00-13:30左右达最大值,其与地表净辐射的日变化趋势基本一致,但感热和潜热的峰值出现时间较地表净辐射峰值出现时间滞后约1 h;温带荒漠草原感热通量和潜热通量的日累积最大值分别为319.01和425.37 W·m^-2,分别出现在5月30日和6月2日;月均感热通量与潜热通量的最大值分别出现在5月和6月,最小值分别出现在1月和12月.研究区土壤含水量与降水的相关性较好,表层土壤含水量对降水的反应最敏感,深层土壤水分对降水的反应存在位相滞后.感热通量和潜热通量的季节动态与地表净辐射基本一致,均受降水影响.感热通量受地表净辐射的影响明显,而潜热通量对降水的反应较敏感,且土壤含水量在潜热通量中起主要作用.     

高效经营雷竹林生态系统能量通量过程及闭合度

利用开路涡度相关系统和常规气象仪,对高效经营的雷竹林生态系统2011年的显热通量、潜热通量、净辐射、土壤热通量以及气温、地温、降雨量进行了观测,分析该生态系统能量通量的变化,以及各能量分量的分配特征,并计算了波文比及能量闭合.结果表明：雷竹林全年净辐射为2928.92 MJ·m^-2,潜热通量、显热通量和土壤热通量分别为1384.90、92754和-28.27 MJ·m^-2,各能量分量的日变化和月变化基本呈单峰曲线.潜热通量为能量散失主要形式,占净辐射的47.3%,显热通量占31.7%,波文比呈“U”型曲线,在0.285～2.062之间变化,土壤为热源.雷竹林年能量闭合度为0.782,月平均闭合度为0.808.
     

九寨沟针阔混交林能量平衡特征

青藏高原及其周边地区的能量交换过程是推动我国及东亚地区天气过程演变与气候变化的重要因素。青藏高原及其周边山谷地区与青藏高原—四川盆地过渡区具有独特的大气边界层热力结构,其能量收支研究不可忽视,但由于长期观测数据的缺失,该地区的能量平衡特征尚未解明。以青藏高原东北边缘向四川盆地陡跌的过渡地带的典型亚高山河谷九寨沟的针阔混交林为研究对象,利用涡度相关系统,对九寨沟典型针阔混交林2014—2015年各能量通量进行了连续观测,分析了该生态系统能量平衡各分量的变化特征,讨论其能量闭合状况。结果表明:能量平衡各分量均与净辐射有相似的日变化、季节变化特征。与萌芽期、生长期、生长后期相比,冻土期各分量峰现时间均延迟2—3 h;而且各项绝对值大小在不同季节占比不同:冻土期和萌芽期显热通量为能量主要支出项;而生长期与生长后期潜热通量占主导地位。九寨沟2014与2015年生长期潜热通量占净辐射比值分别为0.69、0.75,远高于青藏高原其他地区。两年间研究区能量不闭合,能量闭合度分别为0.75,0.71。对于更好地理解高原山区和从高原到盆地的能量循环机理和动力学有着重要意义。     

哺乳动物生物钟与能量代谢的相关研究进展

生物钟广泛存在于各种生物体中,是生命体的一种内源调节机制。哺乳动物生物钟系统与机体营养代谢和能量平衡有着密切的关系。概述了生物钟系统通过营养途径、限速酶途径、核受体途径对哺乳动物机体代谢活动和能量平衡的调控,以及哺乳动物代谢稳态对生物钟系统的影响,从而为从生物钟调控的角度治疗和防控代谢综合征提供新的思路。     

How NOT to Approach the Obesity Problem

FLATT, JP. How NOT to approach the obesity problem. The emphasis given to the energy balance equation has fostered the widespread belief that obesity is a problem of energy balance. This mistaken view has led to many unjustified and unfortunate interpretations, because obesity is, rather, a problem of the interaction between body composition and food intake regulation.     

Effects of forest management on the carbon dioxide emissions of wood energy in integrated production of timber and energy biomass

The aim of this work was to study the sensitivity of carbon dioxide (CO₂) emissions from wood energy to different forest management regimes when aiming at an integrated production of timber and energy biomass. For this purpose, the production of timber and energy biomass in Norway spruce [Picea abies (L.) Karst] and Scots pine (Pinus sylvestris L.) stands was simulated using an ecosystem model (SIMA) on sites of varying fertility under different management regimes, including various thinning and fertilization treatments over a fixed simulation period of 80 years. The simulations included timber (sawlogs, pulp), energy biomass (small‐sized stem wood) and/or logging residues (top part of stem, branches and needles) from first thinning, and logging residues and stumps from final felling for energy production. In this context, a life cycle analysis/emission calculation tool was used to assess the CO₂ emissions per unit of energy (kg CO₂ MWh^?1) which was produced based on the use of wood energy. The energy balance (GJ ha^?1) of the supply chain was also calculated. The evaluation of CO₂ emissions and energy balance of the supply chain considered the whole forest bioenergy production chain, representing all operations needed to grow and harvest biomass and transport it to a power plant for energy production. Fertilization and high precommercial stand density clearly increased stem wood production (i.e. sawlogs, pulp and small‐sized stem wood), but also the amount of logging residues, stump wood and roots for energy use. Similarly, the lowest CO₂ emissions per unit of energy were obtained, regardless of tree species and site fertility, when applying extremely or very dense precommercial stand density, as well as fertilization three times during the rotation. For Norway spruce such management also provided a high energy balance (GJ ha^?1). On the other hand, the highest energy balance for Scots pine was obtained concurrently with extremely dense precommercial stands without fertilization on the medium‐fertility site, while on the low‐fertility site fertilization three times during the rotation was needed to attain this balance. Thus, clear differences existed between species and sites. In general, the forest bioenergy supply chain seemed to be effective; i.e. the fossil fuel energy consumption varied between 2.2% and 2.8% of the energy produced based on the forest biomass. To conclude, the primary energy use and CO₂ emissions related to the forest operations, including the production and application of fertilizer, were small in relation to the increased potential of energy biomass.     

Relationship between transpiration and respiration in plants during the dark period

Energetic aspects of the relation between transpiration and respiration during the dark period were evaluated. One-year old seedlings of three trees, one bush and one annual plant were grown in controlled conditions. Experiments were performed under uniform environment during the day and two regimes of air relative humidity (RH) during the night, low (50 - 65 %) and high (95 %). For all investigated plant species the dark transpiration rate (E), the free energy of respiratory substrate, the entropy production and the free energy balance (FEB) of the dark respiration were higher at low than at high RH. E was linearly related to the FEBr ² ranged between 0.63 and 0.90)     

Physiological changes during colony establishment in the termite Hodotermes mossambicus (Hagen): Water balance and energy content

The changes in dry mass, wet mass and energy content were determined during the establishment of the incipient colony. The winged reproductives of H. mossambicus are weak fliers. It is postulated that the alates compensate for the large quantity of reserve material by reducing their body water. The wet mass of both males and females increased significantly (twice original mass) from emergence until the first larvae appeared which tends support to this view. Furthermore, although the termites maintained in groups imbibed water, it is also clear that the reproductives, as long as they remain social, maintain the same low body-water content. This desiccated physiological condition appears to be and adaptation which assists flight and dispersal. In contrast with sterile eggs, fertile eggs absorbed water during development. The paired females (normal and homosexual) maintained the same energy/unit wet mass from egg production until the first workers appeared. Thus the possibility exists that the hydrophobic reserves (e.g. triglycerides) were converted to the hydrophilic reserves (e.g. carbohydrates). The same applied to the eggs and offspring.The changes in dry mass, wet mass, body water and energy content of females per unit of eggs (specific mass) produced were 0.005, 8.696, 21,276 and 12.820 respectively. The small specific dry mass value can probably be ascribed to the use of small amounts of glycerides and the increase in dry mass by the conversion from relatively light and “compact” glycerides to relatively heavy and “bulky” glycogen.Females utilised far more dry mass and energy in comparison to males to survive until the first workers appeared. Wet mass, body water and energy used in rearing of the offspring shows clearly that males made a larger contribution to the water and energy requirements of the offspring.     

Circadian rhythms and the gut microbiome synchronize the host’s metabolic response to diet

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