北方稻田生态系统水量平衡及水分效率研究

１９９３～１９９５年研究了５种不同模式水稻田生态系统水量平衡及水分效率结果表明,不同水稻田模式其总耗水量之间有明显差异,其中节水模式和节水节肥模式较常规模式节省灌溉水达１５～２３％,水分生产效率增加３０％以上．各模式蒸发蒸腾耗水量在同一生长季内基本相同．田间结构及调控管理对其无明显影响实测水稻生育期田间蒸发蒸腾量与计算的可能蒸发蒸腾量相差不过５％。     

基于热比率法的青海云杉林蒸腾量估算

流域上游森林蒸腾量的准确估算对于干旱区水资源管理至关重要。该文采用热比率法的树干液流技术对青海云杉(Picea crassifolia)单木和林分蒸腾量进行了估算和转换, 目的在于通过该研究为不同尺度森林蒸腾量估算提供一个系统的解决方案。研究结果如下: 第一, 青海云杉胸径与边材面积间存在显著指数函数关系, R² = 0.94, p < 0.000β1; 第二, 热比率法的青海云杉蒸腾量测量中, 理论值与观测值间的比例系数为1.09, 观测值偏小; 第三, 基于单木平均液流速率和林分总边材面积的林分蒸腾量计算中, 不同胸径样树液流速率的异质会导致液流速率被高估或低估近1/3; 第四, 基于单木胸径与液流量间关系的林分液流估算技术能够更合理地对青海云杉蒸腾量进行估算。根据该文研究结果, 基于探针式液流测量技术可以更为科学地对单一树种研究区不同尺度的蒸腾量进行估算。     

西北黑河中游荒漠绿洲农田作物蒸腾与土壤蒸发区分及作物耗水规律

利用中国生态系统研究网络临泽内陆河流域研究站绿洲农田2009年小气候、湍流交换、土壤蒸发和叶片气孔导度等综合观测试验数据,应用Shuttleworth-Wallace(S-W)双源模型以半小时为步长估算了绿洲农田玉米生长季实际蒸散量,并利用涡动相关与微型蒸渗仪实测数据对田间蒸散发量和棵间土壤蒸发量计算结果进行了检验。结果表明:S-W模型较好地估算研究区的蒸散量,并能有效区分农田作物蒸腾和土壤蒸发;全生育期玉米共耗水640 mm,其中作物蒸腾累积量为467 mm,土壤蒸发累积量为173 mm,分别占总量的72.9%和27.1%;日时间尺度上,作物蒸腾和土壤蒸发分别在0—6.3 mm/d和0—4.3 mm/d之间变化,其日平均分别为2.9和1.0 mm/d;田间供水充足,作物蒸腾与土壤蒸发比值明显受作物生长过程影响,播种—出苗期、出苗—拔节期、拔节—抽雄期、抽雄—灌浆期、灌浆—成熟期,其比值分别为0.04、0.8、7.0、5.2和1.4,不同阶段的比值差异主要受叶面积指数影响。     

祁连山区青海云杉林蒸腾耗水估算

青海云杉(Picea crassifolia)林在祁连山区水量平衡中起着重要的调节作用,合理并准确地估算其冠层蒸腾量,对于了解该区的水分循环和水分平衡具有重大意义。以位于祁连山中段大野口关滩森林站的青海云杉纯林为研究对象,结合研究区微气象梯度观测塔自动记录的常规气象资料(气温、空气相对湿度、风速等)以及太阳辐射、大气中CO₂ 浓度、土壤热通量等,应用改进的Penman-Monteith修正式对研究区青海云杉林2008年生长季的冠层蒸腾量进行估算,并采用单变量敏感性分析法对模拟结果进行分析。结果表明:青海云杉林2008年生长季(5-9月)的总蒸腾量为148.8 mm,平均日蒸腾量为0.97 mm;冠层蒸腾量主要受太阳辐射的影响,使得日蒸腾量在典型晴天高达2.19 mm,而在阴雨天仅为0.016 mm;气温对冠层蒸腾量的作用也十分重要,随气温的变化,日蒸腾量从5月开始逐渐增大,在7月中上旬达最大值,从7月下旬到生长季结束其值逐渐减小;模型输入参数对模拟蒸腾量的影响强弱顺序为:林冠层截获的净辐射＞叶面积指数＞气温＞风速＞大气相对湿度;当模型输入参数在±10%变动时,模拟结果的变化范围均在±10%以内,说明该模型的模拟结果比较稳定。在积累了大量相关基础数据的条件下,通过该改进的Penman-Monteith修正式估算森林蒸腾耗水量仍是一种获得满意结果的便捷方法。     

液流径向变化对尾巨桉单株日蒸腾量估算的影响

采用Granier热扩散方法(TDP)测定了尾巨桉2个径向深度(0～2和2～4 cm)的液流速率,探讨液流径向变化对树木蒸腾估算产生的影响、不同个体大小的估算误差以及估算误差与光合有效辐射(PAR)和水汽压亏缺(VPD)的关系.结果表明: 尾巨桉的日蒸腾量在单点径向深度0～2 cm条件下估算值最大,两点综合估算值次之,单点径向深度2～4 cm最小,单点径向0～2 cm和径向2～4 cm所得的日蒸腾量分别较两点综合估算值高估了32.9%和低估了58.7%;用单点径向0～2 cm估算蒸腾量时所产生的误差随胸径的递减而减少,胸径为17.7、12.9和9.8 cm的树木产生的估算误差分别为51.7%、33.0%、18.0%,而单点径向2～4 cm所产生的估算误差则没有明显的径级差异;PAR和VPD都与单点径向0～2 cm估算误差有较好的正相关性,相比较VPD而言,PAR与单点径向0～2 cm估算误差的相关性更好.相比传统的仅用单一深度液流速率估算单株蒸腾耗水量的方法,两点估算方法一定程度上提高了日蒸腾量计算的精度,为尾巨桉人工林森林耗水量估算提供了可靠依据.     

温室甜瓜营养生长期日蒸腾量估算模型

建立了基于温室环境参数、甜瓜生长发育参数和土壤水分参数的温室甜瓜日蒸腾量估算模型,以研究温室条件下甜瓜蒸腾量的估算方法.根据温室内特定环境对Penman-Monteith方程中空气动力项进行修正,推导出了适于计算温室条件下参考作物蒸腾量的温室环境因子子模型;以甜瓜叶面积指数为自变量构建了作物因子子模型,模型形式为线性函数;以土壤相对有效含水量为自变量构建了土壤水分因子子模型,模型形式为对数函数.采用分期播种法,根据周年不同播期实测数据对模型参数进行估计和分析.采用土壤相对含水量分别为80%、70%、60%的实测蒸腾数据,对模型在充分灌溉和节水灌溉条件下的预测精度进行了检验,模拟值的平均相对误差分别为11.5%、16.2%、16.9%.所建蒸腾模型是对Penman-Monteith公式在温室环境和节水灌溉条件下的有益探索,具有重要推广应用价值.     

高尔夫球场草坪生态效益及其价值估算

通过试验测定,分析了北方草坪草叶面积与其修剪特征之间的关系,进而建立草坪不同修剪高度下的叶面积指数关系模型。结果表明,草坪草叶面积指数随着草坪修剪高度的增加而增加,叶片宽度对叶面积指数变化的影响更大。在此基础上,以天津市某高尔夫球场为例,对该球场内不同组成部分的草坪绿量进行调查统计,并结合草地早熟禾单位面积日蒸腾量、释氧固碳量、蒸腾释水量和吸热量,计算得出案例中高尔夫球场草坪的生态效益为年蒸腾总量88119744.59mol,年吸收CO2量10771.66t,年释放O2量7830.67t,年蒸腾吸热量6903753.43GJ,并运用环境效益评价法估算出该球场草坪年吸收CO2量总价值为1102.59万元,年释放O2量总价值为313.23万元,年蒸腾吸热总价值为126760.58万元,总生态价值量达128176.95万元。     

马占相思夜间树干液流特征和水分补充现象的分析

研究马占相思树干的夜间水分补充现象有助于提高总蒸腾量、冠层气孔导度估算的准确度,同时可以深化对冠层蒸腾与树干液流所代表的日蒸腾之间时滞现象的认识。在广东鹤山马占相思林,采用热扩散探针法测定液流密度,同步测定主要的环境因子,从不同的时间尺度分析其树干夜间水分补充现象。结果表明:与白天相比较,夜间马占相思液流密度较小;夜间液流密度的变化幅度旱季比雨季大,树干夜间水分补充的主要时间段是前半夜;年内各个月份夜间水分补充量之间没有显著差异,它与环境因子之间相关关系不显著,但与胸径、树高、冠幅的回归曲线拟合较好;干季夜间补充的水分对总蒸腾量的贡献与白天蒸腾量、总的蒸腾量、水蒸气压亏缺(VPD)、光合有效辐射(PAR)以及大气温度(T)显著相关;湿季夜间补充的水分对总蒸腾量的贡献与白天蒸腾量、总蒸腾量显著相关。     

大棚甜瓜蒸腾规律及其影响因子

研究大棚甜瓜的蒸腾规律和影响因子,可以为大棚甜瓜水分优化管理提供理论依据。利用大棚盆栽试验,设定了4个水分梯度,定量分析了大棚甜瓜蒸腾规律及蒸腾量与植株生理特性、气象环境因子、土壤水分含量的关系。结果表明:(1)各水分处理条件下甜瓜蒸腾强度日变化曲线均呈"双峰型",有明显的"午休"现象。(2)甜瓜生理需水系数与叶面积指数、有效积温关系显著,分别呈线性和抛物线函数关系。(3)甜瓜全生育期累计蒸腾量呈现出"慢—快—慢"的变化规律,可以用Logistic函数进行模拟。(4)甜瓜叶面积指数、日平均空气温度、日平均空气相对湿度、日太阳辐射累积、土壤相对含水量均与单株日蒸腾量呈显著性相关关系;甜瓜叶面积指数对蒸腾的综合作用最大,是决策变量;土壤水分含量是限制变量,主要通过对其他因子的影响间接作用于蒸腾。(5)气象环境因子对甜瓜蒸腾量的影响力很大程度上取决于土壤水分含量;气象环境因子与蒸腾量的相关性随土壤水分含量的增大而增大,在土壤相对含水量为70%—80%范围内达到最高值,当土壤含水量接近田间持水量时,与各因子的相关系数逐渐下降。(6)甜瓜水分胁迫指数与土壤相对有效含水量关系显著,二者呈现线性关系。     

水分胁迫对银中杨耗水特征与水分利用的影响

在不同供水条件下,采用LI-6400光合作用系统(LI-COR,1995,USA)和电子天平等仪器,对银中杨苗木气体交换、蒸腾耗水量和水分利用效率及其有关环境因子进行了测定。结果表明,在研究的诸环境因子中,土壤含水量是制约苗木蒸腾耗水的主导因子;苗木的蒸腾耗水量随土壤干旱胁迫的加重而减少,并且当土壤含水量低于田间持水量的50%时,气象因子对苗木蒸腾耗水的影响不再明显;土壤含水量为田间持水量的70%时,银中杨苗木的净光合速率和蒸腾速率下降不显著,而水分利用效率有所提高,为2.579μmol.mmol-1,在土壤含水量大于田间持水量的70%的水分条件下,银中杨苗木可以正常生长。     

Separating foliar physiology from morphology reveals the relative roles of vertically structured transpiration factors within red maple crowns and limitations of larger scale models

A spatially explicit mechanistic model, MAESTRA, was used to separate key parameters affecting transpiration to provide insights into the most influential parameters for accurate predictions of within-crown and within-canopy transpiration. Once validated among Acer rubrum L. genotypes, model responses to different parameterization scenarios were scaled up to stand transpiration (expressed per unit leaf area) to assess how transpiration might be affected by the spatial distribution of foliage properties. For example, when physiological differences were accounted for, differences in leaf width among A. rubrum L. genotypes resulted in a 25% difference in transpiration. An in silico within-canopy sensitivity analysis was conducted over the range of genotype parameter variation observed and under different climate forcing conditions. The analysis revealed that seven of 16 leaf traits had a ≥5% impact on transpiration predictions. Under sparse foliage conditions, comparisons of the present findings with previous studies were in agreement that parameters such as the maximum Rubisco-limited rate of photosynthesis can explain ～20% of the variability in predicted transpiration. However, the spatial analysis shows how such parameters can decrease or change in importance below the uppermost canopy layer. Alternatively, model sensitivity to leaf width and minimum stomatal conductance was continuous along a vertical canopy depth profile. Foremost, transpiration sensitivity to an observed range of morphological and physiological parameters is examined and the spatial sensitivity of transpiration model predictions to vertical variations in microclimate and foliage density is identified to reduce the uncertainty of current transpiration predictions.     

植物根系水力再分配模型参数分析与尺度转换

植物根系水力再分配(Hydraulic redistribution)是近几年提出的对植物根系水力提升现象一种更准确的描述。Ryel等(2002)建立的根系水力再分配模型(以下简称Ryel模型)模拟结果表明根系水力再分配是土壤水分动态的一个重要组成部分。该文基于Ryel模型,对模型中涉及的重要参数进行敏感性分析,更准确地阐述参数变化下根系水力再分配模型的行为动态,从而定量分析环境及植物自身等因素对根系水力再分配的影响。Ryel模型时间尺度和土层厚度的设定限制了模型的应用,该文通过参数调整,将模型从时间尺度为小时、土层厚度均一转换到时间尺度为天、土层厚度不等,并应用到内蒙古皇甫川流域。     

Environmental Effects on Transpiration and Leaf Water Potential in Avocado

A field study was conducted to determine how atmospheric and edaphic conditions influenced the water relations of avocado trees (Persea americana Mill. cv. Bacon). With high and low levels of incident photosynthetically active radiation (PAR, 400–700 nm wave length), and either wet or dry soil, leaf conductance decreased as the absolute humidity difference from leaf to air increased. For any water stress treatment, conductance was higher at high PAR than at low PAR. Both conductance and transpiration were higher in well-watered trees than in stressed trees, and in prestressed trees levels were intermediate to unstressed and stressed trees. A model for water flux through the soil-plant-atmosphere continuum was used to examine the relationship of leaf xylem pressure potential to transpiration in well-watered trees and in trees stressed by dry soil. There was a close linkage between leaf xylem pressure potential and transpiration in unstressed and previously stressed trees with high or low PAR, i.e. similar potentials occurred with equivalent transpiration regardless of previous treatment or time of day. In stressed trees, xylem pressure potential was lower than in unstressed trees both during the day and night, and at a given transpiration rate the potential was lower after 1400 h than before that time. The model indicated that in stressed trees xylem pressure potential was uncoupled from transpiration, presumably because of altered resistance in the soil-root portion of the transport system.     

Mathematical model of ontogenetic changes and circadian cycles of transpiration rates

A now mathematical model, representing the transpiration process during ontogenesis and a circadian transpiration cycle, analysed in detail statistically, was designed using data obtained by the new modification of the gravimetric determination of the transpiration of intact plants. Regression analysis applied to the circadian cycle makes it possible to characterize basis parameters of the intensity and of the extent of this process and may serve a s a starting point when studying transpiration methodologically in greater detail.     

Mathematical model of ontogenetic changes and circadian cycles of transpiration rates

A new mathematical model, representing the transpiration process during ontogenesis and a circadian transpiration cycle, analysed in detail statistically, was designed using data obtained by the new modification of the gravimetric determination of the transpiration of intact plants. Regression analysis applied to the circadian cycle makes it possible to characterize basis parameters of the intensity and of the extent of this process and may serve as a starting point when studying transpiration methodologically in greater detail.     

Summary method for determining the water consumption for the transpiration of woody plant seedlings

A method of calculation for determining the total transpiration (consumption of water for transpiration) of a single woody plant seedling or of their growth during periods of different length (from one day up to the whole vegetative season) is described and critically evaluated; the calculation is performed according to single transpiration intensity measuring results, by the cut-shoot method and weighing at 8, 11, 14 and 17 hours (or more often during the day).     

Biophysical models of cardiac electrical activity

A system for 3D simulation of heart electrical activity at different structural levels based on fundamental knowledge on the spatiotemporal organization of extracellular electric fields in the myocardium is being developed at the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences. The system is based on a biophysical model of the genesis of electrocardiosignals (ECSs) in the form of a double electric layer on the surface of the electrically active myocardium, which was proposed earlier and then modified. The system combines a model of the activation and repolarization of the heart ventricles, an advanced model for determining the parameters of the heart electric field, which makes it possible to obtain model ECSs both by direct calculation of the potentials and calculation of ECSs from preliminarily determined components of a multipole equivalent heart generator, a database of model parameters and their combinations in the form of cards of simulated “patients,” and a database of simulated ECSs. This paper (the first in a series of three on the subject) briefly describes simulation methods used in electrocardiology and the biophysical model of heart electrical activity that forms the basis of the system for computer simulation of direct and inverse problems concerning the heart electric field. Electrophysiological, anatomical, and biophysical characteristics of the heart are the parameters of the model.     

Leaf Water Potential Response to Transpiration by Citrus

This paper reports on further studies of a model for interpreting leaf water potential data for Citrus. Experimental data confirmed the assumption that the ratio of vapor pressure deficit to leaf diffusion resistance adequately estimates transpiration when leaf-to-air temperature differences are small. Data collected diurnally indicated that the relationship between leaf water potential and transpiration followed a sequence of steady states without hysteresis. No difference in water transport characteristics was found for Valencia orange on three rootstocks in well-watered soil, but the two rootstocks Cleopatra mandarin and Rangpur gave slightly greater leaf water stress in Valencia orange leaves than‘Troyer’ citrange rootstock at high transpiration rates under mild soil water deficits. In laboratory studies, previously unstressed seedlings had higher leaf water potentials than field trees at equivalent transpiration rates. After several drying cycles, however, leaf water potentials were similar to those observed in the field.     

Effects of Climate Change and a Doubling of CO2 on Vegetation Diversity

A model is presented for predicting the response of global familydiversity to global environmental change. The model assumesthat three primary mechanisms determine diversity: the capacityto survive the absolute minimum temperature of a site, the abilityto complete the life cycle in a given length and warmth of thegrowing season, and the capacity to expand leaves in a definedregime of precipitation and vegetation transpiration. The directeffects of CO₂ on vegetation transpiration are also included. About one-third of the floristic regions of the world exhibitincreased diversity with a 3°C increase in temperature,a 10% increase in precipitation, and a doubling of the CO2 concentration.The addition of CO₂ offsets the increased rates of transpiration,caused by global warming through its capacity to reduce transpiration.As a consequence, the diversity of dry regions displayed thegreatest increase in diversity due to increased CO₂.