华北石质山区山茱萸人工林蒸腾特征及水分供求关系

于2005年及2006年主要生长季节(4-9月),采用由热扩散植物液流技术测算得到的蒸腾速率数据,结合同步观测得到降雨量,分析华北石质山区15年生山茱萸人工林耗水规律及水分供求关系.结果表明:1)山茱萸人工林蒸腾量呈现出明显的日际变化或月变化特征.表现为4-5月逐渐升高、6月左右达到高峰值、7月以后逐渐降低.2005年及2006年4-9月蒸腾总量分别为265.3和194.9 mm,4-9月各月蒸腾总量占蒸腾总量的比例在2005年分别为10.7%、22.3%、21.6%、21.2%、12.9%和11.2%,在2006年分别为16.2%、20.2%、20.3%、17.9%、13.6%和11.2%;2)蒸腾与冠层太阳总辐射、空气温度、湿度及风速等微气象要素有很好的复相关性(α=0.01),偏相关系数表明,各月内影响蒸腾的最主要微气象因子都是冠层太阳总辐射;3)4-9月降雨总量与蒸腾总量的比值(R/Tr)＞1.0,且除4月外,其他各月R/Tr也大于或接近于1.0,说明除4月外,降水可以满足山茱萸人工林蒸腾耗水的需要.     

华北平原农田毛白杨防护林蒸腾变化规律及其与气象因子的关系

于2007年主要生长季(4—9月),采用热扩散(TDP)技术测算了华北平原农田24年生毛白杨防护林带的蒸腾速率,分析了毛白杨蒸腾变化规律及其与气象因子的关系。结果表明:(1)在晴天日和阴天日,毛白杨蒸腾速率的日内变化都为单峰曲线趋势,而在多云日受太阳辐射剧烈变化的影响,为多峰曲线趋势。在4、5、6、7、8、9月份晴天日的单株日平均蒸腾速率分别为5.44、7.84、8.05、7.87、7.26、7.17 L.h-1,在多云日分别为4.10、5.87、6.84、6.68、6.49、5.88 L.h-1,在阴天日分别为4.33、3.56、4.14、5.90、3.39、2.66 L.h-1。(2)毛白杨林带蒸腾量的日际变化或季节变化明显,从4月份开始逐渐升高,5月份由于受林网内农作物灌溉量加大的影响,蒸腾量与6、7月份基本持平,8、9月份逐渐降低。在2007年主要生长季(4—9月),林带蒸腾总量为488.016 mm,4—9月各月蒸腾量所占生长季总蒸腾量的比例分别为11.17%、18.71%、19.30%、19.29%、16.66%、14.88%。(3)主要生长期内,毛白杨蒸腾速率与同步观测得到的太阳辐射、空气温度、空气湿度和风速具有很好的复相关性,回归分析得到的相关模型可通过显著性检验(α=0.01);且计算偏相关系数表明,各月影响蒸腾速率的最主要气象因子均为太阳辐射。     

华北石质山区杜仲人工林蒸腾特征及水分供求关系

采用由热扩散树干液流技术测算得到的、周期为2个主要生长季节(4—9月)杜仲人工林蒸腾数据,结合同步观测得到降雨量以及冠层微气象数据,分析了华北石质山区10年生杜仲人工林耗水规律及水分供求关系,旨在为该地区杜仲的发展提供必要的水分生态理论依据.结果表明:(1)杜仲人工林蒸腾量(豫)呈现出明显的日内变化和日际变化特征,在晴天条件下,杜仲人工林蒸腾呈现单峰变化趋势,在多云及阴天条件下,呈现多峰变化趋势;阴天日蒸腾值明显低于晴天及多云日;杜仲蒸腾的日际变化表现为:4-5月逐渐升高,6月份左右达到高峰值,7月份逐渐降低,2005年及2006年4-9月蒸腾总量分别为268.5、212.0 mm,4-9月各月蒸腾总量所占总蒸腾量的比例在2005年分别为12.3％、20.4％、20.2％、18.2％、15.9％和13.0％,在2006年分别为10.6％、21.7％、23.3％、17.4％、14.6％和12.4％;(2)TR与冠层太阳总辐射(Ra)、空气温度、湿度及风速等微气象要素有很好的复相关性(a=0.01),各月影响豫的最主要微气象因子都是Ra;(3)4-9月降雨总量(P)与豫的比值(P/TR)都大于1.0,且除4月份外,各月P/TR也大于或接近于1.0,说明降水可以满足杜仲人工林蒸腾耗水的需要.     

阿拉善白刺生长季叶片尺度耗水特性

为优化水资源的配置,恢复或重建生态系统,以便在干旱、半干旱地区改进抗旱节水造林技术,对阿拉善盟白刺群落生长季叶片尺度耗水特性进行测定了分析。结果表明:(1)白刺生长季水分利用效率日变化最高值出现在上午,5、6、9、10月在10:00左右达最大值,而7、8月在8:00左右达最大值,最小值出现在早、晚。月变化为9、10月最大,其次7、8月,5、6月最小。其中月均值10月9月7月8月6月5月。(2)整体上光合速率上午比较强,而蒸腾速率上午呈现上升趋势,在中午达最大值,下午二者都呈现递减趋势。(3)生长季各月叶片水势与蒸腾速率呈相反趋势。(4)白刺蒸腾耗水主要是消耗深50cm土壤附近的水。     

阿拉善白刺生长季需水量估算

为了探究阿拉善白刺单株、群落生长季需水量,对阿拉善白刺群落需水量进行了研究。结果表明:(1)白刺的蒸腾量随着地径不同,表现出显著差异,地径越大,蒸腾量越大。从液流变化规律看,白刺液流高峰出现在15:00左右。(2)阿拉善盟白刺各月日均耗水量最大的月份为7月,日平均液流量为1 154.3g·cm~(-2),各月耗水量大小依次为7月>8月>6月>9月>5月>10月。(3)以地径作为纯量,计算出白刺灌丛的日蒸腾总量和单株蒸腾量估算值分别为0.065m~3和0.000 4m~3。(4)阿拉善盟白刺的最大生态需水量为4.34×10~8 m~3,实际生态需水量为3.23×10~8 m~3。     

3种生态型红叶石楠冬季光合特性研究

测定了全光照球形、柱形、遮荫球形三种生态型红叶石楠的冬季光合特性,结果表明:红叶石楠的气孔导度、蒸腾速率及蒸腾总量的日变化曲线相似,三种生态型都呈现出12:00-22:00时变化平稳,22:00后逐渐增高,4:00左右回落,6:00开始逐渐上升,8:00-12:00蒸腾活跃;全光照球形光合效率高、释放氧大于柱形,遮荫球形不能释放氧;红叶石楠适宜种植在没有任何遮荫的全日照条件。     

毛乌素沙地新疆杨蒸腾变化规律及其影响因素

利用热扩散(TDP)技术于2004年4-9月测算毛乌素沙地21年生新疆杨蒸腾速率,分析新疆杨蒸腾变化规律及其与气象因子、土壤水分、水面蒸发以及叶面积指数的关系.结果表明:1)在主要生长季节(4-9月),新疆杨单株蒸腾总量为5 300.96 L,月最大蒸腾量出现在6月,为1 073.82 L,占4-9月总量的20.26%;2)新疆杨蒸腾速率与太阳辐射、空气温度、相对湿度、风速等各气象要素有很好的复相关性,其中,影响新疆杨蒸腾的最主要气象因子为太阳辐射,蒸腾与太阳辐射之间存在时滞性;3)受地下水位影响,土壤水分与新疆杨日蒸腾量相关性不大,不是毛乌素沙地新疆杨蒸腾的限制因子;4)新疆杨日蒸腾量与叶面积指数×水面蒸发的关系用乘幂函数拟合效果较好,相关系数为0.83,利用建立的乘幂方程可以推算新疆杨日耗水量.     

金沙江干热河谷植被恢复树种盆栽苗蒸腾耗水特性的研究

采用快速称重法对金沙江干热河谷28种植被恢复树种盆栽苗蒸腾耗水规律进行了研究,结果表明:(1)在干热的3月份,在土壤水分充足的条件下,25个供试树种盆栽苗在典型晴天里全天蒸腾耗水量为171.80～731.00 g,白天蒸腾耗水量为147.10～631.70 g,白天蒸腾耗水量占全天耗水量的78.83%～91.16%,其中,24个树种的盆栽苗白天平均蒸腾耗水速率为0.95～6.91 mmol·m-2·s-1,表明不同盆栽苗的耗水能力存在明显差异.(2)在湿季10月份,14个供试阔叶树盆栽苗全天的蒸腾耗水量为204.06～303.28 g,白天平均耗水速率为0.82～2.12mmol·m-2·s-1.(3)所有供试盆栽苗在干热季节里的蒸腾耗水速率均大于湿季,干热天气加剧了参试盆栽苗的蒸腾作用,加大了蒸腾失水的速度.(4)干热胁迫推迟了大部分树种盆栽苗蒸腾耗水量日变化峰值出现的时间,对绝大多数参试盆栽苗而言,干热胁迫降低了蒸腾量的日变化幅度.(5)充分供水条件下,盆栽苗木蒸腾耗水量及耗水速率日变化的单峰分布特征不受季节变化所引起的大气干旱胁迫程度的影响,随着土壤干旱胁迫加深,苗木蒸腾耗水量的日变化峰值有所提前,单峰态类型有向多峰态类型过渡的趋势.     

不同杨树品系光合作用的研究

对13个杨树品系1 a生苗木的净光合速率、蒸腾速率进行测试与分析,结果表明:不同品系的净光合速率差异较大,杂1号、杂2号、A5-13、A5-17的净光合速率较对照大青杨分别高出15.07%、17.15%、5.25%和11.52%。长势较好的6个品系和对照的净光合速率日变化明显,杂1号、杂2号、A5-17、自选1号和对照呈现"双峰"曲线,峰值出现在10:00时和14:00时;A5-13、辉南5号呈现"单峰"曲线,峰值出现在14:00时。6个品系蒸腾速率的日变化基本相同,在11:00~13:00时达到最大值,之后迅速下降;同对照比较,A5-13、A5-17、杂1号、杂2号为高光合、高蒸腾类型,辉南5号为高光合、低蒸腾类型,自选1号为低光合、匀速蒸腾类型。在光合有效辐射为0~800μmol.m-2.s-1范围内,6个品系的净光合速率随着光合有效辐射的增加而增强,基本呈正相关;在光合有效辐射为1 500μmol.m-2.s-1左右时,达到光饱和点。     

不同热环境下国槐盆栽苗木蒸腾耗水规律

利用二氧化碳变量法(Licor-6400便携式光合测定系统)和称重法等方法,对放置于硬路面、裸露土面及草坪上的国槐盆栽苗木的蒸腾耗水特性进行了研究。结果表明,不同下垫面地温、冠层空气相对湿度差异显著(P0.05),冠层空气温度差异不显著。国槐叶片蒸腾速率(Tr)差异显著(P0.05),硬路面Tr为草坪的1.17-2.10倍;净光合速率(Pn)差异不显著,硬路面国槐叶片Pn稍大于草坪。硬路面与草坪国槐单位叶面积日耗水量差异显著(P0.05)。相关分析表明,不同下垫面的Tr与地温呈显著或极显著正相关,与冠层空气相对湿度呈显著或极显著负相关。     

银杏树干茎流变化及其对抑制蒸腾措施的响应

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.     

Tree water use and rainfall partitioning in a mature poplar-pasture system

Traditionally, poplars (Populus) have been planted to control erosion on New Zealand's hill-slopes, because of their capacity to dry out and bind together the soil, by reducing effective rainfall and increasing evapotranspiration and soil strength. However, the effect of widely spaced poplars on the partitioning of soil water and rainfall has not been reported. This study determined rainfall partitioning for 18 mid-spring days in a mature P. deltoides (Bart. ex Marsh, Clone I78)-pasture association (37 stems per hectare, unevenly spaced at 16.4 +/- 0.4 m) and compared it with a traditional open pasture system in grazed areas of a hill environment. Tree transpiration was measured by the heat pulse technique. A time-driven mathematical model was used to set a zero offset, adjust anomalous values and describe simultaneous sap velocity time courses of trees. The model showed that daylight sap flow velocities can be represented with a nonlinear Beta function (R(2) > 0.98), and differences in the parameters representing the initiation, duration and conformation of the sap velocity can be tested statistically to discern tree transpiration differences during the day. Evapotranspiration was greater for the poplar-pasture association than for the open pasture (2.7-3.0 versus 2.2 mm day(-1)). The tree canopy alone contributed 0.92 mm day(-1) as transpiration and 1.37 mm day(-1) as interception, whereas evapotranspiration of the pasture understory was only 0.4-0.6 mm day(-1). Despite the higher water use of the poplar-pasture association, soil water in the 0-300 mm soil stratum was higher than, or similar to, that of the open pasture. Tree shading decreased evapotranspiration and pasture accumulation under the trees.     

木麻黄南北方位边材液流季节动态及其对蒸腾耗水测算的影响

利用TDP径流计对福建沿海木麻黄南北方位的边材液流动态进行长期监测，并同步检测空气温湿度、太阳辐射等环境因子，分析南北方位液流速率的相互关系、对蒸腾耗水量测算的影响以及与环境因子的关系。结果显示，木麻黄南北2个方位测得的液流速率存在显著差异和线性相关。木麻黄生长季（5～10月）内单株蒸腾耗水量与日总太阳辐射和昼间平均空气水汽压亏缺的指数饱和曲线拟合效果较好。采用单方位树干液流速率测算的整株蒸腾耗水量与2个方位的测算值相差18．19％。     

Transpiration of a hybrid poplar plantation in Saxony (Germany) in response to climate and soil conditions

The aim of this study was to investigate transpiration and its main driving factors on the example of a hybrid poplar plantation with the clone Populus maximowiczii × P. nigra, cv. Max 1 on a site in the hilly loess region of Saxony (Germany). Transpiration was measured using sap flow techniques during the 2007 and 2008 growing season. At the same time, throughfall, soil moisture dynamics and soil physical properties were also measured. Total transpiration rates amounted to 486 mm and 463 mm, respectively, during the 2 years. Maximum daily transpiration rates reached 6.7 mm/day, while an average of 2.2 mm/day for the entire growing season was recorded. The main controlling factors for stand transpiration included the evaporative demand, water availability and soil temperature. The information was implemented into a simple empirical model for the prediction of transpiration. It can be concluded that large-scale establishment of poplar plantations will result in a distinct reduction in groundwater recharge. On the other hand, surface run-off and soil erosion may decrease. Due to limited water availability in the late growing season, the growth potential of the tested clone cannot fully be exploited at many sites in Germany.     

Change of trunk sap flow of Ginkgo biloba L. and its response to inhibiting transpiration treatment

For this paper, GREENSPAN sap flow system was used to monitor the dynamics of trunk sap flow of Gingkgo biloba. Results indicate that sap flow velocity is significantly different among different heights, depths, and directions of the trunk. Sap flow velocity at the upper position of the trunk is higher than that of the middle and lower position, but cumulative flux is not significantly different among the upper, middle and lower sections. Sap flow velocity at 10 mm reached the most and that at 20 mm the least. However, sap flow velocity at 5 mm and 15 mm was similar and was second among the four depths. Results also showed that sap flow velocity of the south was the highest, and that of the west was next. An Automatic Weather Station of HOBO was synchronously applied to measure these meteorological parameters, and the relationship between these parameters and the changes of trunk sap flow velocity were analyzed. We found that the change of sap flow velocity was a single-crest curve on clear days and multi-crest curve on cloudy and rainy days. In addition, it is also revealed that by stepwise regression analyses photosynthetical active radiation (PAR), temperature and wind speed are the main environmental factors affecting sap flow velocity. The efficient methods of reducing water transpiration of trees, including leaf pruning, overshadowing and antitranspirant spraying, were found by investigating the effects on inhibiting transpiration, which indicated that spraying of antitranspirants, leaf pruning and overshadowing could significantly reduce transpiration but the effects of leaf pruning and overshadowing were far better than that of antitranspirant spraying. Translated from Scientia Silvae Sinicae, 2006, 42(5): 22–28 [译自: 林业科学]     

Nocturnal sap flow characteristics and stem water recharge of Acacia mangium

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. __________ Translated from Chinese Journal of Ecology, 2007, 26(4): 476–482 [译自: 生态学杂志]     

Transpiration and canopy conductance of Caragana korshinskii trees in response to soil moisture in sand land of China

Caragana korshinskii is widely used in vegetation reestablishment programs to stabilize the shifting of sand on the Loess Plateau. This sand shifting of sand exerts pressure on the limited soil water and vice versa. However, detailed transpiration and sap flow studies that focus on water use in these stands remain limited. The hourly sap flows, along with successive soil water balance and meteorological measurements, on three trees were measured using the thermal heat balance method during the growing season period. Results showed that the midday sap flow and stand transpiration were significantly lower during the stress period (from May to July) compared with those at the beginning of August concurrently with high soil water content. The heat balance measurements underestimated the transpiration obtained from the soil water balance method. When the tree conductance was fitted with climatic variables and soil water content, the canopy conductance increased exponentially with above-canopy radiation, whereas it decreased logarithmically with decreasing vapor pressure deficit. In the absence of water stress, the tree conductance was unchanged when the relative extractable water remained above 0.4, whereas the conductance decreased linearly after the wilting point. The model was generally well fitted to the measured transpiration data in terms of the response during the dry and rainy seasons, thus demonstrating the feasibility of developing a quantity schedule for C. korshinskii transpiration on the Loess Plateau in the presence of a soil water stress.     

Seasonal and interannual variability of canopy transpiration of a hedgerow in southern England

Transpiration from a hawthorn (Crataegus monogyna L.) dominated hedgerow in southern England was measured continuously over two growing seasons by the sap flow technique. Accompanying measurements of structural parameters, microclimate and leaf stomatal and boundary layer conductances were used to establish the driving factors of hedgerow transpiration. Observed transpiration rates, reaching peak values of around 8 mm day(-1) and a seasonal mean of about 3.5 mm day(-1), were higher than those reported for most other temperate deciduous woodlands, except short-rotation coppice and wet woodlands. The high rates were caused by the structural and physiological characteristics of hawthorn leaves, which exhibited much higher stomatal and boundary-layer conductances than those of the second-most abundant woody species in the hedgerow, field maple (Acer campestre L.). Only in the hot summer of 2003 did stomatal conductance, and thus transpiration, decrease substantially. The hedgerow canopy was always closely coupled to the atmosphere. Hedgerow transpiration equaled potential evaporation (calculated by the Priestley-Taylor formula) in 2003 and exceeded it in 2004, which meant that a substantial fraction of the energy (21% in 2003 and more than 37% in 2004) came from advection. Hedgerow canopy conductance (g(c)), as inferred from the sap flow data by inverting the Penman-Monteith equation, responded to solar radiation (R(G)) and vapor pressure deficit (D). Although the response to R(G) showed no systematic temporal variation, the response to D, described as g(c)(D) = g(cref) - mln(D), changed seasonally. The reference g(c) depended on leaf area index and the ratio of -m/g(cref) on long-term mean daytime D. A model is proposed based on these observations that predicts canopy conductance for the hawthorn hedge from standard weather data.     

Stable annual pattern of water use by Acacia tortilis in Sahelian Africa

Water use by mature trees of Acacia tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan var. raddiana growing in the northern Sahel was continuously recorded over 4 years. Water use was estimated from xylem sap flow measured by transient heat dissipation. Concurrently, cambial growth, canopy phenology, leaf water potential, climatic conditions and soil water availability (SWA) were monitored. In addition to the variation attributable to interannual variation in rainfall, SWA was increased by irrigation during one wet season. The wet season lasted from July to September, and annual rainfall ranged between 146 and 367 mm. The annual amount and pattern of tree water use were stable from year-to-year despite interannual and seasonal variations in SWA in the upper soil layers. Acacia tortilis transpired readily throughout the year, except for one month during the dry season when defoliation was at a maximum. Maximum water use of about 23 l (dm sapwood area)(-2) day(-1) was recorded at the end of the wet season. While trees retained foliage in the dry season, the decline in water use was modest at around 30%. Variation in predawn leaf water potential indicated that the trees were subject to soil water constraint. The rapid depletion of water in the uppermost soil layers after the wet season implies that there was extensive use of water from deep soil layers. The deep soil profile revealed (1) the existence of living roots at 25 m and (2) that the availability of soil water was low (-1.6 MPa) down to the water table at a depth of 31 m. However, transpiration was recorded at a predawn leaf water potential of -2.0 MPa, indicating that the trees used water from both intermediary soil layers and the water table. During the full canopy stage, mean values of whole-tree hydraulic conductance were similar in the wet and dry seasons. We propose that the stability of water use at the seasonal and annual scales resulted from a combination of features, including an extensive rooting habit related to deep water availability and an effective regulation of canopy conductance. Despite a limited effect on tree water use, irrigation during the wet season sharply increased predawn leaf water potential and cambial growth of trunks and branches.     

干季核桃树干液流特征及其与气象因子的关系

我国北方存在严重的水资源短缺问题,研究干旱半干旱区域植被的液流特征,对于没有灌溉条件的丘陵山区,确定耗水量和立地水分的合理承载能力,对于当地生态植被建设和管理具有重要的作用.本文应用热脉冲技术对干旱半干旱退耕区核桃(Juglans regia L.)的液流速率、液流通量等进行分析,为植被建设模式的确定和管理提供理论依据.