排序方式： 共有69条查询结果，搜索用时 15 毫秒
61.
亚热带樟树树干液流通量变化规律 总被引：1，自引：0，他引：1
采用热脉冲技术于2013―2015 年连续测定了樟树的树干液流,并同步监测了环境因子,分析了樟树树干液流日变化和季节变化特征以及对不同环境条件的响应。结果表明：樟树树干液流速率晴天日变化为典型的单峰型曲线,季节变化明显,液流速率峰值夏季＞春季＞秋季＞冬季,峰宽随季节变化存在“窄→宽→窄”的逐步变化过程。樟树存在微弱的夜间液流,且生长季较其他月份活跃。液流启动时间夏季最早,冬季最晚,液流结束（进入夜间低值）时间夏季晚于冬季约1~2 h。上下午液流量比值均＜1,平均值为0.74。同月不同天气条件下,液流速率和液流量均为晴天＞阴天＞雨天。干旱环境下,樟树树干液流峰值下降了约95%,与2014 年相比,同期内液流总量减少了约47.8%,在干旱中液流量与气温、水汽压亏缺呈显著负相关,改变了常年中（没有干旱）液流量与气温和水汽压亏缺呈显著正相关的关系。干旱显著降低了樟树的树干液流量,也反映了樟树对干旱的适应过程。 相似文献
62.
Quantifying evapotranspiration and its components in a coniferous subalpine forest in Southwest China 总被引：1，自引：0，他引：1
Evaporation is one of the most important processes in the soil‐plant‐atmosphere‐continuum water cycle. The objectives of the present study were to (1) test the feasibility of different methods for quantifying evapotranspiration (ET) and its components and (2) investigate and quantify ET and its components in a subalpine watershed from April to October, 2009. Our research site was in the Gongga Mountains, located on the southeastern fringe of the Qinghai‐Tibet Plateau. The components of ET could be observed using the interception, sap‐flow and stable isotope techniques. The summation of these components, referred to as the summed components method, was thought to be the ET. Similar estimates of ET from April to October were obtained using the summed components (736 mm) and Eddy covariance (598 mm) methods. The mean of two ET estimates (667 mm) accounted for 50% of the total water input. ET was composed of 6% soil evaporation, 19% vegetation transpiration and 75% interception evaporation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
63.
沙漠人工植被区柠条树干液流变化及影响因子分析 总被引：3，自引：1，他引：2
于2008年5—9月利用Dynamax茎流仪测量了沙坡头地区18 a龄人工柠条的树干液流速率,并利用涡动相关系统同步监测了环境因子,分析柠条液流的变化规律及其与环境因子的关系。结果表明,观测期间柠条液流速率均表现为明显的单峰曲线,液流一般在00:00左右启动,08:30—11:30达到高峰,然后下降,在午夜时分达到最低。对液流速率与环境因子的相关分析表明,太阳辐射、相对湿度、空气温度、风速等因子显著影响到柠条的液流速率,其中太阳辐射和相对湿度的影响最为显著, 经过逐步回归建立了该区柠条液流速率与环境因子的多元线性方程。 相似文献
64.
岩溶区青冈栎树干液流特征及其与环境因子关系 总被引：3，自引：0，他引：3
为阐明岩溶区植物液流变化特征,应用Granier 热消散探针法,连续测定了桂林岩溶区植物青冈栎1年整的树干液流密度变化,并用ICT-2000TE环境气象站同步监测林地环境因子。结果表明: 不同季节青冈栎树干液流密度差异较大,液流密度峰值分别为: 1月份36. 17g H2O /m2· s, 4月份62. 01g H2O /m2· s, 7月份63. 41g H2O /m2· s, 10月份39. 03gH2O /m2· s。土壤含水量在1月份、4月份、7月份与树干液流呈极显著相关;空气湿度和水汽压亏缺在1月份、10月份与树干液流呈极显著相关;空气温度在4月份、10月份与树干液流呈极显著相关,而光合有效辐射在所有的观测月份均与树干液流呈极显著相关。对各时期树干液流密度与环境因子的多元线性回归方程进行F 值检验,均达到极显著水平。 相似文献
65.
白榆、新疆杨液流动态比较研究 总被引：3，自引：2，他引：1
运用Granier热扩散式探针(TDP)法对宁夏河东沙地主要乔木树种白榆（Ulmus pumila）和新疆杨（Populus alba）夏初边材液流变化规律进行连续观测。利用自动气象站对周围气象因子如太阳辐射（Rs）、空气温度（Ta）、空气相对湿度（RH）和风速（Ws）进行同步观测,并对气象因子与白榆、新疆杨边材液流通量(Fs)的相关性进行分析。结果表明：①白榆、新疆杨边材液流速率（Vs）变化规律存在显著差异,白榆Vs主体表现为窄小双峰型,新疆杨Vs主体表现为宽峰波动型;白榆日间液流启动时间较新疆杨提前0.0~0.8 h,峰值出现时间推迟0.0~2.0 h,峰值持续时间较新疆杨缩短2.5~6.7 h,液流消退时间提前0.0~2.5 h。②白榆边材液流通量(Fs)仅为0.50 kg·h-1,而新疆杨高达1.25 kg·h-1,为白榆的2.5倍;白榆日耗水量（W）在8.81~17.73 kg·d-1之间,而新疆杨W在22.82~34.06 kg·d-1之间。③白榆、新疆杨在夜间保持一定的液流量以补充白天所耗水分,夜间水分补充量对各自日耗水量的贡献相近,为8%左右。④白榆、新疆杨Fs与气象因子关系密切,但气象因子的作用过程表现复杂。复相关分析表明：白榆、新疆杨Fs与Rs、Ta、Ws之间呈极显著正相关,与相对湿度RH呈极显著负相关,按相关程度排序为：Rs>RH>Ta>Ws。 相似文献
66.
树干木质部中树液流密度的变化会引起树干局部电位差的变化,通过测定这种局部电位差来研究液流密度的变化过程是一种可行的方法.本次研究通过测定倾斜黄杨加水前后树干的局部电位差,同时借助小波变换方法,探讨了这种局部电位差对根系吸水过程的响应.结果表明：加水前树干液流密度相对稳定,而在加水后树干部分区域的树液便开始了明显的流动;加水后树液优先从树干的向阳面流动,而树干侧面的树液流动则明显滞后于向阳面;干旱状态下局部电位差对根系吸水过程响应的变化幅度要明显大于湿润条件;电位差的变化在短时间条件下反映树干液流的变化过程,并可据此测定液流速度,但在更长的时间尺度条件下则可能更多地反映了树干的生理变化过程. 相似文献
67.
Examination and parameterization of the root water uptake model from stem water potential and sap flow measurements 总被引：2，自引：0，他引：2
Yuting Yang Huade Guan John L. Hutson Hailong Wang Caecilia Ewenz Songhao Shang Craig T. Simmons 《水文研究》2013,27(20):2857-2863
A simple field‐based method for directly parameterizing root water uptake models is proposed. Stem psychrometers and sap flow meters are used to measure stem water potential and plant transpiration rate continuously and simultaneously. Predawn stem water potential is selected as a surrogate for root zone soil water potential to examine and parameterize the root water uptake–water stress response functions. The method is applied to two drooping sheoak (Allocasuarina verticillata) trees for a period of 80 days, covering both a dry season and a wet season. The results indicate that the S‐shape function is more appropriate than the Feddes piecewise linear function for drooping sheoak to represent the effect of soil moisture stress on its root water uptake performance. Besides, the water stress function is found to be not only a function of soil moisture but also dependent of the atmospheric demand. As a result, the water stress function is corrected for the effect of atmospheric conditions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
68.
Bananas are widely cultivated in tropical and subtropical countries and about 220 tons of biomass waste is produced per hectare of banana plantation. Banana pseudostem contains nearly 90% of moisture and about 4–5 m3 sap is generated from one ton of dried stem with high chemical oxygen demand(COD) and biological oxygen demand (BOD). The feasibility of using banana sap as a feedstock to produce ethanol is evaluated in this study. Banana sap is obtained by crushing the pseudostems and concentrated ten times and supplementing with other industrial byproducts such as corn steep liquor(CSL), spent wash (SW), and yeast extract (YE) for ethanol production. Acid and alkali hydrolyzes are performed to enhance the sugar levels of the sap before fermentation. Two different strains of Saccharomyces cerevisiae (MTCC170 and MTCC180) are used for fermentation. In general, supplementation of banana sap with industrial byproducts significantly enhanced the ethanol production. The maximum ethanol production (2.5 g ?1) is observed with concentrated banana sap supplemented with 25% SW (v/v) with MTCC170, which is 16‐fold higher than banana sap alone. Theethanol content is also higher in alkali‐hydrolyzed banana sap supplemented with 25% SW compared to control. These results suggest that banana sap can be used as a renewable source to produce ethanol by supplementing with other industrial byproducts. 相似文献
69.
Changes in evapotranspiration components following replacement of Eucalyptus regnans with Acacia species 
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下载免费PDF全文 Forest species composition may change following a disturbance. This change can affect long term water yield from forested catchments when the replaced and replacement species have different evapotranspiration rates. Following strip‐thinning experiments that removed 50% of the overstorey basal area in several Eucalyptus regnans water supply catchments in south eastern Australia, Acacia spp. (Acacia dealbata and Acacia melanoxylon) became the dominant overstorey species in most of the cut strips. More recently, low regeneration of E. regnans following wildfires in 2009 may result in mixed Acacia and E. regnans stands in some catchments. We compared transpiration of E. regnans and Acacia stands in the uncut and cut strips of a catchment that was strip‐thinned in early 1980s (Crotty Creek). We also compared transpiration and throughfall in a mixed E. regnans–A. dealbata regrowth stand 20 years after clear‐fell logging (Road 8). Sap flow was measured for 13 and 6 months at Crotty Creek and Road 8, respectively. In both studies, mean daily sap flow density of Acacia spp. was lower than of E. regnans. Estimated Leaf Area Index of E. regnans stands was slightly greater than that of Acacia spp. Stomatal conductance (gc), estimated by inverting the Penman–Monteith equation, differed between the species suggesting species‐level physiological differences with Acacia being more sensitive to vapour pressure deficit than E. regnans. Throughfall measurements at Road 8 indicated interception was slightly higher in A. dealbata but only enough to offset about 13% of the difference in transpiration. Replacement of E. regnans by Acacia dominated stands may, therefore, decrease catchment evapotranspiration and increase streamflow. 相似文献