Average Daily Transpiration Research Articles

Comparison of transpiration activity of Quercus robur L. and Acer campestre L. trees under different conditions of moisture supply in the Viiskova ravine

Determining the role of trees in the water cycle and their impact on soil moisture and atmospheric humidity is crucial. This study aimed to investigate the patterns of leaf transpiration in Quercus robur and Acer campestre in a maple-oak forest under varying water supply conditions. The research was conducted in the lower third of the lower third of the north-facing slope and the middle third of the south-facing slope in the Viiskova ravine. A silvicultural and taxation survey of model trees was conducted on both sample plots, where the plantations are moderately dense. The diurnal course of transpiration patterns of these deciduous species was studied throughout the vegetation period. This physiological process reached its highest values in both species on the north-facing slope during the summer months, especially in Quercus robur. On the south-facing slope, in May and June, the average daily transpiration values in both species were almost indistinguishable. During the remaining months of the vegetation period, the intensity of water evaporation by Quercus robur leaves was statistically higher than that of Acer campestre. It was established that on the south-facing slope, under more arid conditions, this process is less active. This pertains to the daily transpiration loss of water by leaves per unit of their mass, monthly transpiration, and the intensity of this process per tree. The difference between the results of water loss by the leaves of a single Quercus robur and Acer campestre tree is significant and is attributed to the lower transpiration rate of Acer campestre, except in May and June under xerophytic conditions, as well as the smaller leaf mass of this species. Both Quercus robur and Acer campestre are hydrostable medium-transpiring species. The maple forest on the north-facing slope evaporates 30.6% more moisture per 1 ha per vegetation period than on the south-facing slope. The results obtained indicate that Acer campestre in a maple-oak forest, under fresh and dry forest-growing conditions, does not pose a significant competition for moisture for Quercus robur when they grow together. The results obtained can be used to develop effective forest management strategies in maple-oak forest

Mounding technique improves physiological performance and yield of oil palm on Spodosols

Spodosols have been widely used for oil palm plantations, specifically in Kalimantan, Indonesia. However, they are sub-optimal for agriculture due to a lack of water and nutrient-holding capacity and a spodic layer that limits plant root development. Therefore, proper agriculture practices are needed for oil palm to enhance its potential yield. This study aims to determine the effect of the mounding technique on the physiological performance and yield of oil palms in spodosol. The study location was well-managed, with eight blocks of oil palm plantations planted in 2008 on spodosols (Typic Haplohumod) in Central Kalimantan. The mounding technique was applied to four blocks of oil palm planted in 2015, while the remaining four were left without mounding. The parameters observed were soil moisture, transpiration, number of bunches, bunch weight, and yield. The results showed that the average moisture in the mounded soil was 4% greater than the control. Additionally, the average daily transpiration of oil palm with the mounding was up to 2.30 mm day<sup>-1</sup> or three times higher than the control. The implication was that the average yield of oil palm increased from approximately 1.84 to 3.71 tons ha<sup>-1</sup> year<sup>-1</sup> compared to no-mounding treatments. Furthermore, the average yield was 19-66% higher than the block without the mounding application.

黄土高原油松冠层气孔导度和蒸腾变化特征与模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土高原油松冠层气孔导度和蒸腾变化特征与模拟 DOI: 10.5846/stxb202106041484 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0501603） Characteristics and modeling of canopy stomatal conductance and transpiration of Pinus tabuliformis on the Loess Plateau Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:油松是黄土高原重要的造林树种，模拟其冠层气孔导度和蒸腾对区域水量平衡计算和人工林可持续经营具有重要意义。基于2015-2018年TDP （Thermal dissipation probes）方法所测得液流数据，分析了黄土高原地区油松冠层平均气孔导度（gc）与冠层蒸腾（Tr）的变化特征与影响因素，并采用Penman-Monteith公式和Jarvis型气孔导度模型模拟了其gc和Tr的变化过程，结果表明：（1）该地区油松gc和Tr日内变化均呈现单峰型，日均蒸腾耗水量为（1.25±0.57） mm/d，生长季（4-10月）总蒸腾耗水量均值为195.47 mm。（2）gc的日内变化受太阳辐射（Rad）驱动（偏相关系数为0.65），当Rad高于300 W/m2时，驱动作用减弱；gc的日内变化受水汽压亏缺（VPD）控制（偏相关系数为-0.41），随VPD的增加而降低；gc的日际变化受土壤水分限制（偏相关系数为0.46），当根区相对有效含水率（REW）低于0.45时，限制作用明显。（3）结合Penman-Monteith公式与Jarvis型模型能有效模拟黄土高原油松gc与Tr变化，小时尺度gc与Tr模拟的纳什效率系数（NSE）分别为0.80和0.78，日尺度Tr模拟的NSE为0.76。 Abstract:Pinus tabuliformis is an important afforestation tree species on the Loess Plateau. Accurate estimation of its canopy stomatal conductance and transpiration is of great significance for regional water balance and sustainable forest management. Previous studies have simulated the daily variation of the transpiration of Pinus tabuliformis based on the response of its stomatal conductance to environmental factors, but the influence of soil moisture has not been considered. Soil moisture is one of the most important factors that limit plant transpiration in this region. Considering the response of stomatal conductance to soil moisture is crucial for modeling transpiration. To estimate the transpiration of Pinus tabulaeformis, the trunk sap flow velocity was measured by the thermal dissipation probes (TDP) method from 2015 to 2018. The meteorological factors and soil moisture were also monitored simultaneously. We analyzed the characteristics and controlling factors of the mean canopy stomatal conductance (gc) and transpiration (Tr) of Pinus tabuliformis on the Loess Plateau. Then the Penman-Monteith formula and Jarvis-type stomatal conductance model were used to simulate the process of its gc and Tr. The results showed that:(1) The daily variation of gc and Tr displayed a unimodal curve. The average daily transpiration rate of Pinus tabuliformis was (1.25±0.57) mm/d, and the mean annual total water consumption in the growing season (April to October) was 195.47 mm. (2) Solar radiation (Rad) was the main driving factor of the diurnal variation of gc (the partial correlation coefficient was 0.65), while the driving effect was weakened when the Rad was higher than 300 W/m2. Vapor pressure deficit (VPD) was the main controlling factor of gc diurnal variation (the partial correlation coefficient was -0.41) and gc decreased with the increase of VPD. Soil moisture was the main limiting factor of the daily variation of gc (the partial correlation coefficient was -0.46). When the relative extractable water content (REW) of the root zone was lower than 0.42, gc would decrease rapidly with the decrease of soil moisture. (3) Combining the Penman-Monteith formula and Jarvis-type model could accurately simulate the variation of gc and Tr. The Nash-Sutcliffe efficiency coefficient (NSE) of hourly gc and Tr simulations were 0.80 and 0.78, respectively, while the NSE of daily Tr simulation was 0.76. The parameters of the model obtained in this study were consistent with the basic characteristics of drought tolerance of Pinus tabuliformis, and could provide an important reference for evaluating the canopy stomatal conductance and transpiration variation of the Pinus tabuliformis on the Loess Plateau. 参考文献 相似文献 引证文献

The transpiration characteristics and heat dissipation analysis of natural leaves grown in different climatic environments

Because vegetation is one of the typical backgrounds on land, it is necessary to investigate the transpiration characteristics and heat dissipation processes of the leaves grown in different natural environments to optimize the thermal infrared camouflage performance of the bionic materials for countering the thermal infrared detection. Considering ambient temperature and relative air humidity as the dominant environmental factors, daily transpiration rates of various kinds of leaves grown in Wuxi (summer and winter, moderate relative air humidity) and Xishuangbanna (summer, high relative air humidity) were measured respectively, and a thermophysical model was established to investigate the heat dissipation processes of the leaves. Results show that the average daily transpiration rates of the leaves are 1.42, 0.42 and 0.92 kg/m2∙day in Wuxi summer, Wuxi winter and Xishuangbanna summer respectively, indicating that the daily transpiration rates vary significantly with different environments. In Wuxi summer and winter, the daily transpirative heat flow accounts for approximately 55.8% and 24.3% of the total heat dissipation of the Cinnamomum camphora leaves respectively, revealing the significant effect of the transpirative heat transfer on the temperature of the leaves grown in the environment of high ambient temperature and the weakened effect in the environment of low ambient temperature. In Xishuangbanna summer, the daily transpirative heat flow accounts for approximately 37.3% of the total heat dissipation of the Ailanthus leaf, which is significantly lower than that in Wuxi summer, indicating that relative air humidity also dominates the effect of transpirative heat transfer on the temperature of the leaves.

Transpiration and Drought Stress Recovery of Three Zinnia Cultivars1

Abstract Transpiration and drought stress recovery were investigated in three container-grown zinnia cultivars [Zinnia elegans Jacq. (‘Lilliput' and ‘Thumbelina') and Z. haageana Reger (‘Persian Carpet')] by measuring daily changes in the normalized transpiration ratio (NTR) of well-watered (control), water-stressed, and water-stressed/re-watered plants. Transpiration of plants grown in gradually drying substrate did not decline until the fraction of transpirable substrate water (FTSW) reached 0.16 to 0.12. Symptoms of plant-water stress (i.e. foliar wilt) were first observed on the leaves of ‘Persian Carpet', which was also the cultivar with the highest average daily transpiration rate. By comparison, the remaining two cultivars (‘Lilliput' and ‘Thumbelina') exhibited lower average daily transpiration rates and took significantly longer to reach the same dry-down endpoint (NTR ≤0.15). Drought stress recovery was assessed by comparing xylem water potential and root and shoot dry weight in well-watered and in drought-stressed plants following a 7-day stress amelioration period. Xylem water potential of all three drought-stressed cultivars increased (i.e. became less negative) one week after re-watering. Root biomass and root:shoot ratio were both significantly greater in water-stressed plants than in well-watered plants of the same cultivar, a finding that suggests the likelihood of osmotic adjustment in response to drought. Index words: normalized transpiration ratio, fraction of transpirable substrate water, foliar wilt, containerized horticultural crops. Species used in this study: ‘Lilliput' and ‘Thumbelina' zinnia (Zinnia elegans Jacq.), ‘Persian Carpet' zinnia (Zinnia haageana Reger).

Growth and Transpiration Responses of Elephantgrass and Energycane to Soil Drying

ABSTRACTElephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp.) are promising perennial bioenergy crops in the southeastern United States. Despite plentiful rainfall in this region, these perennial grasses have a long growing season and are subject to intermittent drying cycles frequently during summer and fall, yet there is little information on their response to intermittent drought stress. The objectives of this study were to investigate water relations of elephantgrass and energycane genotypes under optimal water inputs and in response to progressive soil drying. Three elephantgrass genotypes (‘UF‐1’, ‘Merkeron’, and ‘PI‐300086’) and three energycane genotypes (‘L79‐1002’, ‘US84‐1047’, and ‘875‐3’) were grown in a greenhouse. Under well‐watered conditions, elephantgrass and energycane exhibited similar daily and total water use, but energycane possessed greater average daily transpiration per unit leaf area (EAVE,leaf) and lower shoot transpiration efficiency (TEshoot) than elephantgrass. Consistent with EAVE, leaf, energycane demonstrated higher stomatal conductance than elephantgrass, but lower assimilation to transpiration ratio (A/T). Among all genotypes, UF‐1 elephantgrass exhibited relatively high A/T, shoot mass production, and TEshoot. In response to progressive soil drying, elephantgrass genotypes closed their stomata at a lower fraction of transpirable soil water and produced higher shoot mass during the drying cycle than energycane genotypes. The different plant water use patterns indicated a species difference in the sensitivity to mild drought stress and could be correlated with their stomatal density and size. The results from this study indicated that elephantgrass is more suited to the frequent mild drought stress between rainfall events common during summer in the southeastern United States.

Environmental controls on sap flow in black locust forest in Loess Plateau, China

Black locust accounts for over 90% of artificial forests in China’s Loess Plateau region. However, water use of black locust is an uphill challenge for this semi-arid region. To accurately quantify tree water use and to explain the related hydrological processes, it is important to collect reliable data for application in the estimation of sap flow and its response to environmental factors. This study measured sap flow in black locust in the 2015 and 2016 growth seasons using the thermal dissipation probes technique and laboratory-calibrated Granier’s equation. The study showed that the laboratory calibrated coefficient α was much larger than the original value presented by Granier, while the coefficient β was similar to the original one. The average daily transpiration was 2.1 mm day−1 for 2015 and 1.6 mm day−1 for 2016. Net solar radiation (Rn) was the key meteorological factor controlling sap flow, followed by vapor pressure deficit (VPD) and then temperature (T). VPD had a threshold control on sap flow at threshold values of 1.9 kPa for 2015 and 1.6 kPa for 2016. The effects of diurnal hysteresis of Rn, VPD and T on sap flow were evident, indicating that black locust water use was conservative.

鼎湖山针阔叶混交林4种优势树种树干液流特征

PDF HTML阅读 XML下载 导出引用 引用提醒 鼎湖山针阔叶混交林4种优势树种树干液流特征 DOI: 10.5846/stxb201310202533 作者: 作者单位: 中国科学院华南植物园;中国科学院大学,中国科学院华南植物园;中国科学院大学,中国科学院华南植物园;中国林业科学研究院热带林业实验中心,中国科学院华南植物园,中国科学院华南植物园,中国科学院华南植物园 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31170375); 中国科学院知识创新工程重要方向项目(KZCX2-YW-GJ01); 广东省自然科学基金项目(9151008901000130) Sap flow characteristics of four dominant tree species in a mixed conifer-broadleaf forest in Dinghushan Author: Affiliation: South China Botanical Garden,Chinese Academy of Sciences,South China Botanical Garden,Chinese Academy of Sciences,South China Botanical Garden,Chinese Academy of Sciences,South China Botanical Garden,Chinese Academy of Sciences,South China Botanical Garden,Chinese Academy of Sciences,South China Botanical Garden,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:运用Granier热消散式探针法,对鼎湖山自然保护区针阔叶混交林4种优势树种(马尾松、木荷、锥栗和广东润楠)的树干液流密度进行了长期连续观测,并同步监测林分的环境因子(光合有效辐射(PAR)、空气温度(T)、空气湿度(RH)、土壤含水量)。结果表明:(1)4种优势树种的边材面积(As)与胸径(DBH)均存在显著相关关系(P < 0.05);(2)各优势树种树干液流均呈现"昼高夜低"单峰曲线,且液流速率存在明显的季节性差异;(3)无论湿季还是干季,光合有效辐射(PAR)和水汽压亏缺(VPD) 均为控制蒸腾的主要驱动因子;(4) 4种优势树种湿季平均日蒸腾量高于干季,马尾松、木荷、锥栗、广东润楠湿季平均日蒸腾量分别为29.52、39.29、30.40、9.41 kgH2O/d,干季分别为20.91、24.84、24.26、8.43 kgH2O/d,干季和湿季的平均日蒸腾量(kgH2O/d)大小均为木荷>锥栗>马尾松>广东润楠,这种种间差异是由边材面积大小和树种本身的生物学特性共同决定的。 Abstract:The plant water use efficiency is not only crucial for plant to maintain a relatively high growth rate but also an important metric of water balance in forest ecosystem. Recent years, sap flow measurement has been widely used as a basis for assessing the water exchange between tree crown and ambient atmosphere for it can keep trees in natural condition without damaging the growth of trees. Many studies on trees' sap flow in single species plantations have been carried out across China, but the studies in natural forests are still few. We measured sap flow of four dominant tree species (Pinus manssoniana, Schima suerba, Castanopsis chinensis and Machilus kwangtungensis) in a mixed conifer-broadleaf natural forest in the Dinghushan Reserve of South China using the Granier's thermal dissipation probe method. The sap flow was measured daily in July and November, 2010, which represented the wet and dry seasons in the region, respectively. The environmental factors such as photosynthetically active radiation (PAR), air temperature (T), relative air humidity (RH) and soil moisture were also recorded. The aims of this study were (1) to investigate the characteristics of sap flow of four dominant tree species, (2) to estimate their relationships with the driving factors of transpiration, (3) and to compare the transpiration rates of different tree species calculated from sap flux density combing with trees' morphological characteristics. The results showed that sapwood area of the four dominant tree species had a significantly (P < 0.05) positive relationship with diameter at breast height (DBH). The coefficient of determination R2 of four trees species were 0.99、0.96、0.93、0.81 respectively. Sap flux density displayed an obvious pattern with higher values during daytime and also showed a significant seasonal variation with higher value in wet season. The average sap flow velocity of P. manssoniana, S. superba, C. chinensis and M. kwangtungensis were (10.07±1.47), (10.07±1.51), (12.20±1.73), (8.35±1.28) gH2O m-2 s-1 in wet season, and were (7.22±1.33), (6.41±1.15), (9.78±1.64), (7.37±1.34) gH2O m-2 s-1 in dry season. Contrast to previous study in Dinghushan Reserve of South China at an altitude of 50m, our research found that sap flow velocity displayed a significant variation along the gradient of altitude, which was induced by the differentiation of microenvironment and plant morphological characteristics. Partial correlation analysis indicated that photosynthetically active radiation (PAR) and vapor pressure deficiency (VPD) were the two main environmental factors determining the tree transpiration in both seasons. Transpiration of the four dominant tree species was much higher during the wet season than in the dry season. The average daily transpiration rates of P. manssoniana, S. superba, C. chinensis and M. kwangtungensis during the wet season were 29.52, 39.29, 30.40, 9.41 kgH2O/d, respectively, while those during the dry season the rates were 20.91, 24.84, 24.26 and 8.43 kgH2O/d, respectively. The order of the average daily transpiration was: S. superba > C. chinensis > P. manssoniana > M. kwangtungensis both in wet and dry seasons. Such difference in daily transpiration among tree species was mainly determined by the sapwood area and biological characteristics. 参考文献 相似文献 引证文献

Validation of canopy transpiration in a mixed-species foothill eucalypt forest using a soil–plant–atmosphere model

Summary Studies of the hydrology of native eucalypt forests in south-east Australia have focused on ash-type eucalypt species that are largely confined to Victoria and Tasmania. Mixed species foothill forests comprise the largest proportion of the forest estate in south-east Australia, yet are poorly known hydrologically. The ability to predict forest transpiration, both with reasonable accuracy and in response to changes in the environment, is essential for catchment management. A soil–plant–atmosphere model (SPA) was validated for 222 days in a mature, mixed species forest of north-east Victoria using measurements of overstorey transpiration (Eucalyptus radiata and Eucalyptus goniocalyx) and site-specific climate and vegetation parameters. There was a stronger relationship between average daily transpiration (0.71 mm day−1) and daily minimum relative humidity (R2 = 0.71), than between average daily transpiration and daily maximum temperature (R2 = 0.65). Stand water use could be predicted best from vapour pressure deficit (R2 = 0.89). SPA successfully predicted stand transpiration (R2 = 0.85) over a range of soil water and climatic conditions. A sensitivity analysis suggests that among the various required inputs, leaf area index (LAI) was the most important, and accurate estimates of LAI could significantly improve estimation of stand transpiration.

Water availability and genetic effects on water relations of loblolly pine (Pinus taeda) stands

The effect of water availability on water relations of 11-year-old loblolly pine stands was studied over two growing seasons in material from two contrasting seed sources. Increasing soil water availability via irrigation increased transpiration rate, and maximum daily transpiration rate on irrigated plots was similar for both seasons, reaching values of 4.3 mm day(-)(1). Irrigation also changed soil water extraction patterns. In the rain-fed control plots, 73% of the average daily transpiration was extracted from the upper 0.75 m of the soil profile. Under irrigated conditions, 92% of transpired water was extracted from the upper 0.75 m of soil, with 79% of transpired water coming from the upper 0.35 m of the profile; only 10% of total transpiration in this treatment was extracted from the soil below 1 m. There was an irrigation x seed source interaction in the response of canopy conductance to water vapor (G(C)) to vapor pressure deficit (D). Under water-limited conditions, trees from the South Carolina seed source (SC) had stronger stomatal control than trees from the Florida seed source (FL), but this difference was not present when water was not limiting. The transpiration-induced water potential gradient from roots to shoots (DeltaPsi) was relatively constant across treatments (P = 0.52) and seed sources (P = 0.72), averaging 0.75 MPa. This reflects strong stomatal control that maintains relatively constant DeltaPsi but at the same time allows leaf water potential (Psi(l)) to fluctuate dramatically in synchrony with soil water potential (Psi(s)). The two seed sources evaluated also showed differences in foliar N and delta(13)C, possibly reflecting differences in adaptation to ambient humidity and water availability regimes in their respective ranges. These differences among seed sources under different water availability scenarios may be informative to natural resource managers and breeders as they design tree improvement and genetic deployment programs for future climate scenarios. For example, the increased stomatal control of SC under decreased soil moisture availability may make this taxon a more conservative deployment choice than FL under future, drier climate scenarios but perhaps at the risk of lower productivity.

Seasonal patterns of carbon dioxide, water vapour and energy fluxes in pineapple

For five consecutive seasons (i.e., 840 days), fluxes of latent ( λE) and sensible heat ( H) and carbon dioxide (i.e., net ecosystem flux, NEF) were measured by eddy covariance over a fertilized pineapple [ Ananas comosus (L.) Merr. cv. Red Spanish] field in the Orinoco lowlands. The large flat and windy experimental site seemed ideal for eddy covariance. For the total number of measurements, the energy balance closure was R a (W m −2) = 0.99( λE + H) − 7, R 2 = 0.91, where R a was the available energy. Results indicate that water deficit limited evapotranspiration and production rates. Thus, the proportion of available energy used for evapotranspiration reached a maximum of 0.84 and declined sharply with soil water content from field capacity (0.052 m 3 m −3) to a minimum of 0.09 at θ < 0.013 m 3 m −3. During the dry seasons and rainless periods, soil moisture status was always below field capacity, which results in moisture stress. During the 1997 dry season, the seasonal average daytime Bowen ratio increased from 0.7 to 4.1 which was associated with increase in air humidity deficit and temperature. The seasonal average daily transpiration over pineapple was 2.5 ± 0.5, 0.6 ± 0.1, 2.4 ± 0.5, 1.0 ± 0.1 and 2.2 ± 0.4 mm, respectively. The cumulative λE (1725 mm) was 61% of the rainfall (2789 mm) and 0.39% of the Class A pan evaporation (4428 mm). During the influence of the southern oscillation phenomena corresponding to 0–340 days after plating (DAP), the sparse crop was a net carbon source with net ecosystem production (NEP) of −66 g(C) m −2. From 340 DAP onwards, it became a net carbon sink with NEP of 142 g(C) m −2. For the growth period (0–840 DAP), the maximum net ecosystem exchange and soil CO 2 flux were 9.9 and 13.0 μmol m −2 s −1, respectively. Soil CO 2 efflux was related to soil temperature depending on soil water content. Bursts of net CO 2 were evident after the dry soil was re-wetted by rainfall. Apparent CO 2 flux in the daytime and nighttime were calculated by adding net ecosystem exchange to soil heterotrophic respiration. The CAM activity (i.e., proportion of net daily primary productivity, NPP, in nocturnal apparent CO 2 flux) varied from 0.00 to 0.93 throughout the pineapple life cycle stages. However, nocturnal uptake was the greater contributor to NPP (ratio >0.50) in only 2.7% of the days. Therefore, NPP depended mainly on apparent photosynthetic flux. For the growth period, the cumulative NPP and yield were 1722 and 247 g(C) m −2. In the Orinoco lowlands, the crop was successful because during the growth period it tolerates seasonal rainless conditions and makes efficient use of water with high CAM activity. The description of the analyzed system provides clues for understanding pineapple productivity and water use in the Orinoco lowlands and comparable landscapes under similar climatic and edaphic conditions.

Estimating water use of sclerophyllous species under East-Mediterranean climate: III. Tabor oak forest sap flow distribution and transpiration

The annual course of daily transpiration and the hydrological balance of a Tabor oak forest were determined. The study was done in a representative forest within the natural geographical range of the species in the lower Galilee region of Israel. The climate is sub-humid with a rainless dry season from May to October. A partial water balance of a 0.1 ha area supporting an average of 14 trees was calculated from: (a) soil water content (SWC) measured by a Neutron Probe at depths of from 0.2 to 8 m, and (b) daylight transpiration rate measured with sap flow sensors by the heat pulse technique. Soil–bedrock complex water content (%) in the first 2 m of the profile fluctuated strongly between 5 and 20% depending on the season. The water content increased with depth from about 10% at 2.0 m depth to more than 20% at 5.0 m depth. For depths exceeding 5.5 m seasonal fluctuations in water content were negligible and water content ranged from 30 to 35%. After a dry winter, water content generally decreased within the main root zone down to about 2.0 m depth. Monthly changes in water content (mm) were greatest at depths of 0.35–1.0 m. Only minor changes in the soil–bedrock complex water content were recorded at greater depths. After a very rainy winter (2002/2003), decreases in soil–bedrock complex water content in the upper 2 m were much larger than after a dry winter. Fluctuations of soil–bedrock complex water content in deeper regions were larger in the wetter year, probably the result of drainage. Sap velocity was measured at six depths in the sapwood, from 4 to 44 mm, at 8 mm intervals. Sap velocity declined with depth, hence, sap flux density too. Based on sap velocity measurements performed during 4 years, the annual average daily transpiration ( T) was 0.796 mm/day. This sums up to 239 mm during ∼300 days of leaf carriage, i. e. 41.3% of the 578 mm average annual rainfall for the area in the last 50 years. In a relatively dry year (rainfall of 432.7 mm) total water withdrawal from the 8 m soil–bedrock profile was 81% of the annual rainfall; of this amount 69% were transpired by the oak trees (239.0 mm), or 55% of the annual rainfall. In a relatively wet year (annual rainfall 801.4 mm) total water withdrawal was 67%; of this amount 45% would be transpired by the oak trees, or 30% of the annual rainfall.

Transpiration of Cupressus sempervirens L. as influenced by canopy structure

We hypothesized that for similar trunk circumferences and leaf masses, under similar climatic conditions, the canopy structure of Cupressus sempervirens L. influences transpiration rate such that the faster transpiring var. horizontalis exhausts the winter's allocation of rainfall earlier, to its own subsequent detriment. To verify this assumption, heat pulse velocity measurements, by means of the heat pulse method, were done at eight periods during the year in the stem xylem of eight matched pairs of trees, each pair composed of a var. horizontalis and a var. pyramidalis tree of similar dimensions. Results showed that during the daylight hours in winter and spring, midday sap flow velocity of var. horizontalis trees was greater than that of var. pyramidalis trees of similar trunk circumferences and foliage mass. Hence, the calculated average daily transpiration of var. horizontalis trees was nearly 50% greater than that of var. pyramidalis trees. During the wet period (November to May), mean daily transp...

Estimating water use by sclerophyllous species under east Mediterranean climate: II. The transpiration of Quercus calliprinos Webb. in response to silvicultural treatments

The water use by a stand of Quercus calliprinos Webb. maquis, growing on Mount Carmel Israel, was estimated by means of the heat pulse method. Hourly heat pulse velocity (HPV) measurements on eight or 16 trunks, each being the main trunk in its stool, were done continuously for between 96 and 240 h, approximately every 3 weeks. The measured trunks were selected to represent the circumference distribution of the 240 trunks at the site. The HPV was measured with a probe carrying six thermistors along its axis, 8 mm apart. The six-thermistor probe was inserted into a hole drilled radially into the trunk exactly 15 mm above the heater, and the reference probe into a hole drilled at least 100 mm lower and aside from the heater. This kind of a probe facilitates measurement of the decline in the pulse velocity with the depth under the bark. Hourly and daily sap flow rates, i.e., transpiration were calculated by means of known procedures and equations. The highest average daily transpiration rate of about 28.1 l per tree per day occurred in May, and the lowest, of 5.0 l per tree per day in October. The estimated total yearly transpiration of the 0.1 ha plot containing 240 oak trunks in 47 stools ranged between 44 and 75% of the preceding winter rainfall, i.e., between 234 and 358 mm. In drier years the trees had used a higher proportion of the annual rainfall than in wetter years. The estimated water consumption by the oak trees in the early years after thinning which left only the 47 main trunks, one per stool, was only 13–20% of the preceding annual rainfall. Thinning caused increased transpiration of the single main trunk, but the estimated overall water use by the remaining trees (47 out of 240) was very much reduced. Thinning of most of the trunks in several stools enhanced the growth rate of the remaining trunks. The circumferences of the trunks in the thinned stools increased to 115.4% of their initial value in 3 years compared with to only 107% by those of the trunks in the non-thinned stools.

Estimating the water use of a sclerophyllous species under an East-Mediterranean climate: I. Response of transpiration of Phillyrea latifolia L. to site factors

Water use by vegetation is the most important parameter which is directly related to plant anatomical and eco-physiological characters, and to soil–bedrock water availability. This basic parameter is important in decision making, planning and management of the open areas under semiarid climatic conditions like those of Israel. Attempts were made to quantify the water use by Phillyrea latifolia L. by means of the heat pulse method. This method provides continuous monitoring of the convective heat pulse velocity (HPV) in the trunk xylem, thus facilitating the quantification of the transpiration flux per tree. The daily and annual water use by this species was estimated by extrapolations from the single-tree transpiration rates, based on the relationship between the leaf area of the measured trees and the entire area. The lithological properties of the bedrock formations in each of the research sites caused significant differences between sites in the average daily transpiration rate and, hence, in the total water use by the P. latifolia scrub formation. The daily transpiration, averaged over a year, ranged between 4.00 and 8.15 l per day per tree, and the estimated annual water use ranged between 179.4 and 365.5 mm, i.e., between 30 and 61% of the annual rainfall in the winter preceding the measurements in 1993.

A comparative analysis of the flooding and fire effects on the energy exchange in a wetland community (Morichal) of the Orinoco Llanos

This work analyzes the effects of flooding and fire stress on a wetland energy balance during the dry season of the Orinoco lowlands. The effect of flooding for burning conditions is evaluated by comparing flux measurements in a flooded/burned (T1) and an unflooded/burned (T3) stand, and the effect of burning for flooding conditions by distinguishing between a flooded/burned (T1) and a flooded/unburned (T2) stand. These examined factors affect the canopy features related to coverage and aerodynamic forcing conditions. The effect of flooding on the average daily radiative budget for the burned stands is to decrease the average daily albedo from 0.14 for the unflooded stand (T3) to 0.08 for the flooded stand (T1). Whereas, the effect of burning for the flooded stands decreases the average daily albedo from 0.16 for the unburned stand (T2) to 0.08 in the burned stand (T1). Furthermore, changes in surface temperature determine variations in the average daily output of long-wave ratios between stands with the most average daily net loss of long-wave radiation (−36.3 MJ m −2 day −1) corresponding to the flooded/burned stand (T1). In the stands, the changes in albedo and surface temperature lead to variation in the available energy. Thus, the average daily net radiation ( R n) is affected by burning of the flooded stands, being 15.2 MJ m −2 day −1 in T1 and 14.7 MJ m −2 day −1 in T2. The effect of flooding on the average daily R n is evident when compared T1 to T3 (13.1 MJ m −2 day −1). The partitioning of R n into sensible ( H) and latent (LE) heat flux over the three stands is measured simultaneously using the Bowen ratio/gradient method, which is temporally corroborated by means of the eddy covariance approach. Results indicate that average daily LE to average daily R n ratio is 0.78, 0.78 and 0.80 for T1, T2 and T3, respectively. However, the partitioning of average daily LE into transpiration and evaporation is affected clearly by the analyzed factors. Thus, burning reduces the transpiration rate from −8.5 to −3.3 MJ m −2 day −1 for the flooded stands (T2 and T1, respectively). Whereas, flooding varies only a small amount the average daily transpiration rate in the burned stands (T1 and T2) (−3.3 and −3.4 MJ m −2 day −1). Over the stands, the average daily H in relation to R n for T1, T2 and T3 was 0.19, 0.21 and 0.22, respectively. In relation to the net storage heat flux (ΔSH), the water table at or above the sediments is a small heat sink as the radiation intercepted by the canopies is relatively large. The average daily net storage heat flux is enhanced slightly in the flooded stand (T1) as compared to that for the unflooded/burned stand (T3). Whereas, in the surface of the unburned stand, ΔSH is in thermical equilibrium. Evaluation of evapotranspiration models as a function of the of hourly LE measured over the three stands, indicates that the Penman evapotranspiration model for equilibrium is appropriated for modeling long-term evapotranspiration, and therefore LE is controlled mainly by the available energy and temperature. However, the slope is above 1 (1.11, 1.12 and 1.04 for T1, T2 and T3, respectively). This possible surface control on the results is corroborated by the Penman–Monteith and Slatyer-McIlroy model for a negligible surface resistance. The modeled values are over-predicted and consequently surface resistance affects partially the results. The effect of the areal surface resistance on wetland potential evapotranspiration is assessed as the wetland is surrounded by a dry savanna environment. The relationship between wetland potential evaporation and savanna evaporation is evaluated using the Lhomme closed-box model of the convective boundary layer. The results indicate that the savanna surface resistance enhances the wetland potential evaporation at equilibrium. The results reported in this analysis are pertinent to similar Orinoco wetlands, nevertheless the controls and functioning of herbaceous wetlands under the described land-use practices are revealing common features for wetlands surrounded by regional savannas in South America.

Transpiration of cottonwood/willow forest estimated from sap flux

Cottonwood/willow forests in the American Southwest consist of discrete, even-aged vegetation patches arranged in narrow strips along active and abandoned stream channels of alluvial flood plains. We used the heat-pulse velocity technique in this study to estimate transpiration in 12 such forest patches along a perennially flowing reach of the San Pedro River in southeastern Arizona, USA during five periods from April to October 1997. Transpiration per unit sapwood area was consistently higher for the larger cottonwood trees found on outer secondary channels compared to that of smaller cottonwood trees along the active channel, but statistically significant differences were found only in August and October. Conversely, transpiration per unit sapwood area in willow was markedly higher for trees along the primary channel than for those few larger trees that were sampled on the outer margins of the forest. Average daily transpiration at the canopy scale among the patches in July was 4.8±0.7 mm per day and ranged from 5.7±0.6 mm per day in young forest patches adjacent to the primary stream channel to 3.1±0.6 mm per day in more successionally advanced patches on secondary channels. Differences in our estimates of transpiration between forest patches along primary and secondary stream channels were related to differences in the ratio of sapwood area to ground area of the forest patches, and leaf area index. Estimates of transpiration from this forest type, and projections of transpiration and groundwater flux over larger areas on the San Pedro River, should take into account structural variation in these forests that relate to population dynamics of dominant trees.

Transpiration from sorghum and soybean growing under ambient and elevated CO 2 concentrations

The increasing concentration of carbon dioxide in the atmosphere ([CO 2]) has several direct effects on plants and these effects may be different for C 3 and C 4 plants. Our objective was to measure hourly and daily whole-plant transpiration rates from the C 4 plant grain sorghum ( Sorghum bicolor (L.) Moench) and the C 3 plant soybean ( Glycine max (L.) Merr.) grown under ambient (359 μmolCO 2 mol −1 dry atmospheric air) and elevated (705 μmol mol −1)[CO 2] values. Transpiration measurements were made for 22 days in August 1994 at Auburn, Alabama, USA, using stem flow gauges on plants growing in open top chambers, n = 8 for each [CO 2] and species. Leaf area averaged slightly more than 0.1 m 2 per plant for sorghum and about 0.2 m 2 per plant for soybean. Averages (15 min and daily) of transpiration, per unit leaf area, were consistently greater from plants growing under the ambient [CO 2] for both sorghum and soybean. Average daily transpiration from plants growing under the elevated [CO 2] was significantly smaller ( P = 0.05) on all but 2 days for soybean and on 9 of the 22 days of measurements for sorghum. Average daily sorghum transpiration was 1128 gm −2 day −1 and 772g m −2 day −1 from plants growing under an ambient and elevated [CO 2], respectively. Corresponding soybean averages were 731g m −2 day −1 and 416g m −2 day −1. The transpiration reduction under elevated [CO 2] was greater for the C 3 plant soybean than for the C 4 plant sorghum. These results support previous studies showing that transpiration, per unit leaf area, from sorghum and soybean will both be reduced if atmospheric [CO 2] continues to increase, although the reduction may be greater for C 3 plants.

Honey Mesquite Transpiration along a Vertical Site Gradient

Honey mesquite (Prosopis glandulosa Torr.) occurs on a variety of sites varying in soil depth and moisture availability. The objective of this study was to compare water use by honey mesquite on upland, lowland, and riparian sites which were assumed to represent increasing levels of available soil moisture within a single watershed. Effects of the upland and lowland sites were evaluated in 1985. The riparian site was evaluated with the other 2 sites in 1986. Soil moisture and average daily transpiration were greater (P < 0.05) on the upland than on the lowland site from mid-May to July in both years, and from mid-August through September 1986. These differences were attributed mainly to soil surface characteristics which created greater infiltration on the upland site. The riparian site was near an ephemeral stream and had a water table as shallow as 1.5 m. Soil water content was much greater for this site compared to the other 2 sites throughout 1986. Mesquite transpiration was greater on the riparian site than on the other sites during July 1986, when seasonal vapor pressure deficit was at maximum. However, transpiration was less on the riparian site than on the upland site during May and June 1986. Soil temperature was significantly lower on the riparian than on the upland site and potentially inhibited transpiration on the riparian site in May and June. The study demonstrated a positive relationship between water availability and transpiration by mesquite but did not support the hypothesis that water availability or transpiration was lowest on upland sites.

Quantidade de água transpirada pelo cafeeiro sombreado e pelo ingazeiro

The present paper discusses the amount of water lost by the soil through the transpiration of coffee plants and shade trees in shaded coffee plantation. All methods and techniques employed in the study of transpiration of the shade tree Inga edulis Mart, were exactly the same as those described in a paper recently published (4). It was determined previously (3) that a shaded coffee plant receiving 55% of full sunlight transpired 80% as much as when in 100% full sunlight. The amount of water transpired by a coffee plant was calculated by taking 80% of the amount transpired in unshaded plantation (4). Comparing the water lost by transpiration of shaded coffee plants and shade trees with the average rainfall in Campinas, Sao Paulo, Brazil, it is seen that from April to September the amount of water transpired exceeds the average rainfall. This finding seems to agree with our previous conclusion (1, 2, 5) that water competition between shade trees and coffee plants is the factor that controls the success of growing coffee under shade in the State of Sao Paulo, Brazil. The highest daily rate of transpiration encountered, for Inga edvlis was 36.7 milligrams per square decimeter per minute. The average daily transpiration was found to be 9.90 grams per square decimeter per day. The total amount of water transpired by an Inga tree was calculated to be 71,140 liters per plant per year. Since the plants submited to the experiment did not suffer a water shortage at any time, the present results show the approximate amount of water lost by the Inga tree and shaded coffee plant under optimal soil-water conditions.