共查询到18条相似文献，搜索用时 161 毫秒
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热技术方法测算树木茎流的发展及应用 总被引：23，自引：0，他引：23
热技术方法根据其设计原理可分为热脉冲法、热平衡法、热扩散法和激光热脉冲法.回顾利用热技术方法测算树木茎流的历史,概述热技术方法的产生和发展过程,重点论述4种热技术方法的设计原理、最新研究成果和概况,及实际应用中需注意的问题.基于热技术法的特殊优点,对其拓展性应用前景进行了展望:应用热技术方法对林木耗水进行尺度扩展,扩展模型中主导环境因子的导入,不同树种群体耗水量的估测等难点问题的深入研究和解决,将推动热技术理论和研究方法的进步.对现有的研究成果和研究目标进行分析认为,热扩散方法将成为未来几年研究树木液流的重要测算方法. 相似文献
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银杏树干茎流变化及其对抑制蒸腾措施的响应 总被引：13，自引：2，他引：13
利用GREENSPAN茎流测定系统监测银杏树干茎流动态变化.结果表明:树干不同高度、不同深度和不同方位的茎流速率存在差异.上位的茎流速率高于中位和下位,但通过上中下位截面的累积茎流通量差异不显著;在不同深度上的茎流速率存在差别,10 mm位点的茎流速率最大,20mm位点最小;不同方位的茎流速率是树干南侧最大,西侧次之,北侧最小.使用HOBO气象站同步测定各种气象因子,分析树干茎流日变化、日际变化及其与气象因子的关系,逐步回归分析表明:太阳有效辐射、气温和风速是影响茎流的主要气象因子.通过干预处理研究不同的抑制蒸腾措施对树干茎流的影响,结果表明喷抗蒸腾剂、摘叶和遮荫处理能有效地降低蒸腾耗水,但摘叶和遮荫处理的效果较为明显. 相似文献
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将实测的杨树液流速率和林木边材厚度(或胸径)经尺度扩展得到林分蒸腾,已成为常用的野外测定方法,但此法没有考虑其他树形因子的影响,当林分密度大、光竞争激烈时,会导致蒸腾估计误差偏大。为认识主要树形因子对液流速率的影响,并为改进样树液流向林分蒸腾的尺度扩展方法提供依据,在六盘山北侧半干旱区华北落叶松人工林内,利用热扩散探针对5株不同优势度样树的液流速率进行了连续观测,研究了生长季中期(叶面积指数达到峰值并保持稳定)不同土壤水分条件下不同优势度树木的液流速率差异。结果表明:优势度越大的树木,其液流在日内的启动越早,结束越晚,到达峰值越早,峰值也越大;日均液流速率明显比优势度小的树木高;液流速率对太阳辐射和饱和水汽压差瞬时变化的响应敏感性比优势度小的树木高,而对土壤水分条件的响应敏感性则弱于后者,但整体上对环境条件的响应趋势一致,不同优势度树木间液流速率的相对差异比较稳定。相关分析表明:液流速率与优势度(或相对树高)、树高呈极显著正相关,与冠长、胸径显著正相关,而与冠幅、边材面积正相关但不显著。利用拟合的优势度与液流速率之间的线性关系(R2=0.95)计算了样地内所有树木的液流速率及其平均值,即林分平均液流速率,该值比常用方法计算结果低16%。建议今后在利用样树液流速率测定结果进行尺度扩展计算林分液流速率和蒸腾时,增加考虑优势度等主要树形因子的影响。 相似文献
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本文介绍一种较为简便地测定树木蒸腾耗水量的方法,即在树干的木质部安装热脉冲发生器,定时发出热脉冲,在热源上方一定距离安装热电偶探测器,探测热脉冲到达的时间,确定液流速度,再用生长锥取木芯,测树干心材与边材的直径,计算边材输导面积,其液流速度与边材面积之积即为树冠蒸腾耗水速率,多日连测可以看出树木耗水日进程及季节进程的变化规律。 相似文献
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用热扩散式茎流计测定园林树木蒸腾耗水量 总被引：2，自引：0，他引：2
采用热扩散式边材液流探针和环境自动监测系统对北京3种园林树木的树干液流及主要环境因子进行了一个生长季的同步观测.结果表明,3树种树干液流的日变化呈明显的单峰曲线,晴天的液流速率大于多云天和阴天,紫叶李和悬铃木的日耗水量明显大于元宝枫;对不同天气3树种每h的液流速率与相应的环境因子进行逐步回归分析.结果显示,影响3树种液流速率的主要环境因子是空气温度、空气相对湿度、辐射强度和5 cm土层温度,在不同天气里起主导作用的因子不同,环境因子与树干液流之间的数量关系能较好地预测树木的蒸腾耗水量. 相似文献
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不同方法测定三倍体毛白杨整树蒸腾的比较 总被引：2，自引：0，他引：2
为了解热扩散法测定速生林蒸腾耗水的准确性,以整树容器法为对照,利用热扩散式边材液流探针（ TDP-30）对5年生三倍体毛白杨整树蒸腾进行测定。结果表明,TDP 法与整树容器法测得的整树蒸腾速率具有一致的“单峰型”日变化趋势,且极显著线性相关（R2＝0.955）。TDP 法较整树容器法测得的整树蒸腾量偏低5.58％。三倍体毛白杨夜间蒸腾显著,两种方法测定的夜间蒸腾量分别为白天的21.24％和31.60％。利用 TDP 法研究三倍体毛白杨蒸腾耗水规律准确、可靠,日间蒸腾耗水量与实际相符而夜间蒸腾量偏小。 相似文献
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不同坡向对栓皮栎耗水规律的影响 总被引：3，自引：0，他引：3
利用热扩散探针配合自动气象站,于2004年度在北京林业大学妙峰山试验林场对不同立地条件下栓皮栎的水分运移规律进行了研究.结果表明：栓皮栎水分运移规律受天气状况和立地条件的影响很大.在晴天,阳坡的液流峰值达到0.007 cm/s,是阴坡液流峰值0.001 5 cm/s的5倍;在阴天,阳坡栓皮栎的液流峰值为0.000 2 cm/s,而阴坡为0.000 3 cm/s,坡向的影响减小.林木的耗水量受到树种本身的遗传因素和外界气候因子的制约,其中太阳辐射、大气温度、风速与液流呈正相关,空气相对湿度、土壤温度对液流的影响表现为负向相关. 相似文献
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O Sperling O Shapira S Cohen E Tripler A Schwartz N Lazarovitch 《Tree physiology》2012,32(9):1171-1178
In a world of diminishing water reservoirs and a rising demand for food, the practice and development of water stress indicators and sensors are in rapid progress. The heat dissipation method, originally established by Granier, is herein applied and modified to enable sap flow measurements in date palm trees in the southern Arava desert of Israel. A long and tough sensor was constructed to withstand insertion into the date palm's hard exterior stem. This stem is wide and fibrous, surrounded by an even tougher external non-conducting layer of dead leaf bases. Furthermore, being a monocot species, water flow does not necessarily occur through the outer part of the palm's stem, as in most trees. Therefore, it is highly important to investigate the variations of the sap flux densities and determine the preferable location for sap flow sensing within the stem. Once installed into fully grown date palm trees stationed on weighing lysimeters, sap flow as measured by the modified sensors was compared with the actual transpiration. Sap flow was found to be well correlated with transpiration, especially when using a recent calibration equation rather than the original Granier equation. Furthermore, inducing the axial variability of the sap flux densities was found to be highly important for accurate assessments of transpiration by sap flow measurements. The sensors indicated no transpiration at night, a high increase of transpiration from 06:00 to 09:00, maximum transpiration at 12:00, followed by a moderate reduction until 08:00; when transpiration ceased. These results were reinforced by the lysimeters' output. Reduced sap flux densities were detected at the stem's mantle when compared with its center. These results were reinforced by mechanistic measurements of the stem's specific hydraulic conductivity. Variance on the vertical axis was also observed, indicating an accelerated flow towards the upper parts of the tree and raising a hypothesis concerning dehydrating mechanisms of the date palm tree. Finally, the sensors indicated reduction in flow almost immediately after irrigation of field-grown trees was withheld, at a time when no climatic or phenological conditions could have led to reduction in transpiration. 相似文献
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Tree water storage and its diurnal dynamics related to sap flow and changes in stem volume in old-growth Douglas-fir trees 总被引：2，自引：0，他引：2
Diurnal and seasonal tree water storage was studied in three large Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees at the Wind River Canopy Crane Research site. Changes in water storage were based on measurements of sap flow and changes in stem volume and tissue water content at different heights in the stem and branches. We measured sap flow by two variants of the heat balance method (with internal heating in stems and external heating in branches), stem volume with electronic dendrometers, and tissue water content gravimetrically. Water storage was calculated from the differences in diurnal courses of sap flow at different heights and their integration. Old-growth Douglas-fir trees contained large amounts of free water: stem sapwood was the most important storage site, followed by stem phloem, branch sapwood, branch phloem and needles. There were significant time shifts (minutes to hours) between sap flow measured at different positions within the transport system (i.e., stem base to shoot tip), suggesting a highly elastic transport system. On selected fine days between late July and early October, when daily transpiration ranged from 150 to 300 liters, the quantity of stored water used daily ranged from 25 to 55 liters, i.e., about 20% of daily total sap flow. The greatest amount of this stored water came from the lower stem; however, proportionally more water was removed from the upper parts of the tree relative to their water storage capacity. In addition to lags in sap flow from one point in the hydrolic pathway to another, the withdrawal and replacement of stored water was reflected in changes in stem volume. When point-to-point lags in sap flow (minutes to hours near the top and stem base, respectively) were considered, there was a strong linear relationship between stem volume changes and transpiration. Volume changes of the whole tree were small (equivalent to 14% of the total daily use of stored water) indicating that most stored water came from the stem and from its inelastic (sapwood) tissues. Whole tree transpiration can be maintained with stored water for about a week, but it can be maintained with stored water from the upper crown alone for no more than a few hours. 相似文献
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Processes preventing nocturnal equilibration between leaf and soil water potential in tropical savanna woody species 总被引：1，自引：0，他引：1
Bucci SJ Scholz FG Goldstein G Meinzer FC Hinojosa JA Hoffmann WA Franco AC 《Tree physiology》2004,24(10):1119-1127
The impact of nocturnal water loss and recharge of stem water storage on predawn disequilibrium between leaf (psiL) and soil (psiS) water potentials was studied in three dominant tropical savanna woody species in central Brazil (Cerrado). Sap flow continued throughout the night during the dry season and contributed from 13 to 28% of total daily transpiration. During the dry season, psiL was substantially less negative in covered transpiring leaves, throughout the day and night, than in exposed leaves. Before dawn, differences in psiL between covered and exposed leaves were about 0.4 MPa. When relationships between sap flow and psiL of exposed leaves were extrapolated to zero flow, the resulting values of psiL (a proxy of weighted mean soil water potential) in two of the species were similar to predawn values of covered leaves. Consistent with substantial nocturnal sap flow, stomatal conductance (gs) never dropped below 40 mmol m(-2) s(-1) at night, and in some cases, rose to as much as 100 mmol m(-2) s(-1) before the end of the dark period. Nocturnal gs decreased linearly with increasing air saturation deficit (D), but there were species-specific differences in the slopes of the relationships between nocturnal gs and D. Withdrawal and recharge of water from stem storage compartments were assessed by monitoring diel fluctuations of stem diameter with electronic dendrometers. Stem water storage compartments tended to recharge faster when nocturnal transpiration was reduced by covering the entire plant. Water potential of covered leaves did not stabilize in any of the plants before the end of the dark period, suggesting that, even in covered plants, water storage tissues were not fully rehydrated by dawn. Patterns of sap flow and expansion and contraction of stems reflected the dynamics of water movement during utilization and recharge of stem water storage tissues. This study showed that nighttime transpiration and recharge of internal water storage contribute to predawn disequilibrium in water potential between leaves and soil in neotropical savanna woody plants. 相似文献
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We report on diurnal and seasonal variations in sap flow rate and stem water potential of Fraxinus excelsior L. saplings growing at the edge of a Fraxino-Aceretum forest in western Germany. Because of shallow soil, the trees were subjected to drought in summer. When soil water availability was not limiting, sap flow rate was related to changes in solar radiation and vapor pressure deficit. Maximum transpiration rates per leaf area were 3.5-7.4 mmol m-2 s-1, and maximum daily totals were 1.7-3.3 kg m-2 day-1. Under drought conditions, stem water potential dropped to midday minima of -2.6 to -3.5 MPa and sap flow rate was strongly related to this parameter. After the drought period, reduced apparent (whole-plant) hydraulic conductance was observed, which was attributed to a continued reduction in stomatal conductance after the drought stress had ceased. A model was developed that linked sap flow rate directly to climatic variables and stem water potential. Good correlation between measured and simulated sap flow rates allowed the model to be used for data interpretation. 相似文献
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大青山油松人工林树干液流动态及其蒸腾耗水规律研究 总被引：2，自引：0，他引：2
应用TDP(Thermal Dissipation Probe)技术对大青山古路板林场的30a生油松人工林树干液流以及不同林分密度下的树木蒸腾耗水规律进行了研究。结果表明:1)在生长季内,树干径向断面形成层以下不同部位输水能力差异较大,最大流速位于形成层下3cm。2)油松树干液流的日进程呈现明显的昼夜变化规律。在11:00左右达到峰值,其值可达0.286 6~0.306 0cm3/s。3)树干液流量(Y)与树木的胸径(X)之间的关系可用Y=0.0053EXP(0.4823X)的指数函数模型表达。4)在相同立地条件下,随着阴坡林分密度从2 147株/hm2增加到4 463株/hm2,单株蒸腾耗水量从0.543 4cm3/s降低到0.319 7cm3/s,而林分蒸腾耗水量变化幅度较小,平均蒸腾耗水量为0.3710±0.0489(5)mm/h。结果指出,大青山30a生油松人工林经营密度应控制在3 307株/hm2左右。 相似文献
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The magnitude and direction of water transport by the roots of eight dominant Brazilian savanna (Cerrado) woody species were determined with a heat pulse system that allowed bidirectional measurements of sap flow. The patterns of sap flow observed during the dry season in species with dimorphic root systems were consistent with the occurrence of hydraulic redistribution of soil water, the movement of water from moist to drier regions of the soil profile via plant roots. In these species, shallow roots exhibited positive sap flow (from the soil into the plant) during the day and negative sap flow (from the plant into the soil) during the night. Sap flow in the taproots was positive throughout the 24-h period. Diel fluctuations in soil water potential, with maximum values occurring at night, provided evidence for partial rewetting of upper soil layers by water released from shallow roots. In other species, shallow roots exhibited negative sap flow during both the day and night, indicating that hydraulic redistribution was occurring continuously. A third sap flow pattern was observed at the end of the dry season after a heavy rainfall event when sap flow became negative in the taproot, and positive in the small roots, indicating movement of water from upper soil layers into shallow roots, and then into taproots and deeper soil layers. Experimental manipulations employed to evaluate the response of hydraulic redistribution to changes in plant and environmental conditions included watering the soil surface above shallow roots, decreasing transpiration by covering the plant and cutting roots where probes were inserted. Natural and manipulated patterns of sap flow in roots and stems were consistent with passive movement of water toward competing sinks in the soil and plant. Because dry shallow soil layers were often a stronger sink than the shoot, we suggest that the presence of a dimorphic root system in deciduous species may play a role in facilitating leaf expansion near the end of the dry season when the soil surrounding shallow lateral roots is still dry. 相似文献
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Hua Wang Ping Zhao Quan Wang Xian Cai Ling Ma Xingquan Rao Xiaoping Zeng 《Frontiers of Forestry in China》2008,3(1):72-78
In this paper, we studied the nocturnal stem water recharge of Acacia mangium. It is helpful to improve the precision of canopy transpiration estimation and canopy stomatal conductance, and to further
understand the lag time of canopy transpiration to stem sap flow. In this study, the whole-tree sap flow in an A. mangium forest was measured by using Granier’s thermal dissipation probe for over two years in the hilly land of South China. The
environmental factors, including relative humidity (RH), precipitation, vapor pressure deficit (VPD), photosynthetically active radiation (PAR), and air temperature (T
a) were recorded simultaneously. The stem water recharge of A. mangium was analyzed on both daily and monthly scales. Sap flux density was lower at night than during the day. The time range of
nighttime sap flux density was longer in the dry season than in the wet season. The water recharging mainly occurred from
sunset to midnight. No significant differences were observed among inter-annual nighttime water recharges. Nighttime water
recharge had no significant correlation with environmental factors, but was well correlated with the diameter at breast height,
tree height, and crown size. In the dry season the contribution of nighttime water recharge to total transpiration had significant
correlations with daytime transpiration, total transpiration, VPD, PAR and T
a, while in the wet season it was significantly correlated with daily transpiration and total transpiration.
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Translated from Chinese Journal of Ecology, 2007, 26(4): 476–482 [译自: 生态学杂志] 相似文献