Dynamics of transpiration, sap flow and use of stored water in tropical forest canopy trees

In large trees, the daily onset of transpiration causes water to be withdrawn from internal storage compartments, resulting in lags between changes in transpiration and sap flow at the base of the tree. We measured time courses of sap flow, hydraulic resistance, plant water potential and stomatal resistance in co-occurring tropical forest canopy trees with trunk diameters ranging from 0.34-0.98 m, to determine how total daily water use and daily reliance on stored water scaled with size. We also examined the effects of scale and tree hydraulic properties on apparent time constants for changes in transpiration and water flow in response to fluctuating environmental variables. Time constants for water movement were estimated from whole-tree hydraulic resistance (R) and capacitance (C) using an electric circuit analogy, and from rates of change in water movement through intact trees. Total daily water use and reliance on stored water were strongly correlated with trunk diameter, independent of species. Although total daily withdrawal of water from internal storage increased with tree size, its relative contribution to the daily water budget (approximately 10%) remained constant. Net withdrawal of water from storage ceased when upper branch water potential corresponded to the sapwood water potential (Psi(sw)) at which further withdrawal of water from sapwood would have caused Psi(sw) to decline precipitously. Stomatal coordination of vapor and liquid phase resistances played a key role in limiting stored water use to a nearly constant fraction of total daily water use. Time constants for changes in transpiration, estimated as the product of whole- tree R and C, were similar among individuals (~0.53 h), indicating that R and C co-varied with tree size in an inverse manner. Similarly, time constants estimated from rates of change in crown and basal sap flux were nearly identical among individuals and therefore independent of tree size and species.     

枣树蒸腾速率变化与气象因子的关系

为了提高水分利用率,以7年生壶瓶枣为材料,利用热扩散式茎流仪,结合对土壤和气象因子的同步检测,动态地研究枣树单木整株的蒸腾耗水规律.结果表明,枣树蒸腾速率的日变化呈单峰曲线,13:00达到最大值,夜间枣树树干也有微弱的茎流,其大小在0～18.64 g/(株·h).枣树在晴天、多云天、阴雨天的平均蒸腾速率分别为436.4...     

Effect of crop load on fruiting and leaf photosynthesis of 'Braeburn'/M.26 apple trees

Four-year-old apple (Malus x domestica Borkh.) trees cv. 'Braeburn' on M.26 rootstock were thinned at full bloom to establish six crop loads ranging from a heavy crop to a deflowered treatment. At harvest, mean yield per tree varied from 0 to 38 kg and mean fruit weight ranged from 225 g in the heaviest cropping treatment to 385 g in the lightest cropping treatment. Light cropping resulted in a significant advance in fruit maturity as indicated by background color, starch/iodine score and soluble solids. There were small differences in leaf photosynthetic rate among the treatments when shoot growth was active. However, in early January, coincident with cessation of shoot growth and maximum rate of accumulation of fruit weight, leaf assimilation rate was reduced by as much as 65% on the deflowered trees compared to the trees carrying the heaviest crop. Leaf assimilation rate showed a curvilinear response to crop load at this time, with little increase in leaf assimilation when crop load exceeded 12 fruit m(-2) leaf area.     

苹果的盆栽技术

1特征特性 　　苹果 (Malus pumila)属于蔷薇科、苹果属的落叶小乔木，幼枝、叶片和冬芽均长有柔毛，叶为卵形或椭圆形，先端尖，边缘具钝锯齿状。伞房花序，有花 3～ 7朵，花呈淡红色或淡紫红色，边缘色泽较深，大多数品种自花不孕，需种植授粉品种，果实有子房和花托两部分发育而成，子房形成果心，花托形成果肉。因品种而言，果实呈圆、扁圆、长圆、椭圆形等，果皮有青、黄、红色等。果期 8～ 11月份，是集花果并美的优良观赏树种之一。 　　苹果为温带树种，在我国东北南部、华北、西北等地广泛栽培，耐寒、不耐湿热，寿命较长。 3～ 5…     

果树光合作用研究进展

综述了近年来国内外果树光合作用的研究进展。涉及的内容有：果树光合作用的基本特性；影响果树光合作用的内外因素；果树光合作用的测定方法，简述了叶绿素荧光动力学技术。     

Interspecific variation of photosynthesis and leaf characteristics in canopy trees of five species of Dipterocarpaceae in a tropical rain forest

Photosynthetic rate, nitrogen concentration and morphological properties of canopy leaves were studied in 18 trees, comprising five dipterocarp species, in a tropical rain forest in Sarawak, Malaysia. Photosynthetic rate at light saturation (Pmax) differed significantly across species, varying from 7 to 18 micro mol m(-2) s(-1). Leaf nitrogen concentration and morphological properties, such as leaf blade and palisade layer thickness, leaf mass per area (LMA) and surface area of mesophyll cells per unit leaf area (Ames/A), also varied significantly across species. Among the relationships with leaf characteristics, Pmax had the strongest correlation with leaf mesophyll parameters, such as palisade cell layer thickness (r2 = 0.76, P < 0.001) and Ames/A (r2 = 0.73, P < 0.001). Leaf nitrogen concentration and Pmax per unit area also had a significant but weaker correlation (r2 = 0.46, P < 0.01), whereas Pmax had no correlation, or only weakly significant correlations, with leaf blade thickness and LMA. Shorea beccariana Burck, which had the highest P(max) of the species studied, also had the thickest palisade layer, with up to five or more layers. We conclude that interspecific variation in photosynthetic capacity in tropical rain forest canopies is influenced more by leaf mesophyll structure than by leaf thickness, LMA or leaf nitrogen concentration.     

Effects of varying crop load on photosynthesis, dry matter production and partitioning of Crispin/M.27 apple trees

Fruit load was altered by flower thinning on three- and four-year-old, field-grown apple trees. Increasing fruit load led to increases in dry matter production per unit leaf area and partitioning to fruit and to decreases in fruit size, percentage fruit dry matter, dry matter partitioning to new shoot growth, thickening of existing woody tissue and root growth. Flower bud production for the following spring was also negatively affected by an increase in fruit load. Leaf photosynthesis was increased in cropping trees in July and August at the time of maximum fruit dry weight increase. Calculated light interception was linearly related to leaf area. The efficiency of conversion of intercepted photosynthetic active radiation to dry matter energy equivalents was 3.3% in heavily cropping trees and 1.8% in non-cropping trees. Total dry matter production was linearly related to both leaf area and light interception, but the variance accounted for by the regression was more than doubled if fruit dry matter or fruit number was included in the regression.     

喀斯特森林宜昌润楠蒸腾耗水规律及其与环境因子的关系

使用热扩散液流探针,于2015年7月至2016年8月连续测定茂兰喀斯特森林宜昌润楠的树干液流,同步测定气温、太阳辐射、相对湿度、降水量、土壤含水量和风速等环境因子,分析不同天气、季节、时间尺度下宜昌润楠蒸腾的变化规律及其与环境因子的关系。结果表明:宜昌润楠树干液流速率呈现昼高夜低的变化规律,各季节日间树干液流速率平均值分别是夜间的8.95倍、14.32倍、10.0倍、5.24倍;不同天气下宜昌润楠日蒸腾速率(g·m-2s-1)依次为晴天(41.93±1.43)>阴天(12.73±0.63)>雨天(8.82±0.29);宜昌润楠日均蒸腾量为(5.75±0.31)kg/d,各季节日均蒸腾量(kg/d)表现为夏季(7.57±0.57)>秋季(6.75±0.72)>春季(4.00±0.54)>冬季(2.35±0.20);小时尺度上,各环境因子对蒸腾影响最大的是太阳辐射,影响最小的是降水量、土壤含水量,其中直接影响因素是相对湿度、太阳辐射(除雨天外),间接影响因素是风速(晴天、阴天)和太阳辐射(雨天);日尺度下因季节不同主要影响因子不同,月尺度下主要影响因子只有太阳辐射;随着时间尺度的增大,影响蒸腾的因素减少,且月尺度下环境因子对蒸腾的解释程度最高(78.9%)。各环境因子对蒸腾量的影响程度随天气条件、昼夜、季节、时间尺度等不同而不同,在任何尺度下太阳辐射都是影响蒸腾的主要环境因子。     

Effects of slope and canopy trees on light conditions and biomass of dwarf bamboo under a coppice canopy

Dwarf bamboo, Pleioblastus chino, grows extensively in abandoned coppice woodlands on the Kanto Plain in central Japan and suppresses other understory plants. In order to clarify the factors determining the growth of P. chino, we considered the effect of light conditions under a coppice canopy and examined its relationship with slope aspect, slope angle, and basal area of the trees. The relative photon flux density under the canopy was highly correlated with canopy coverage (R ² = 0.97). The light conditions under the canopy were almost the same at all sites in the summer leafy season regardless of the stand type, while they were remarkably different among the sites and depended on the basal area of evergreen trees in the winter leafless season. The biomass of P. chino on the forest floor was described by the equation: y = 3.18 x ₁ – 0.05 x ₂ + 3.11 (R ² = 0.77, P < 0.01), where y is the log-transformed value of P. chino biomass (gdrymassm^–2), x ₁ is cos at solar noon at the winter solstice, and x ₂ is the canopy coverage during the winter leafless season. is the angle between the suns rays and the normal to the surface and changes with slope aspect and angle. We concluded that light conditions under the canopy in the leafless season had a great effect on P. chino biomass, and that the basal area of evergreen trees and slope characteristics can provide useful guidelines in the control and management of P. chino.     

Response of canopy stomatal conductance of Acacia mangium forest to environmental driving factors

Granier’s probes were applied to measure the sap flow of 14 sample trees in an Acacia mangium forest on the hilly lands in Heshan City, Guangdong, during the time period of October, 2003. The photosynthetically active radiation (PAR), air relative humidity (RH) and temperature of air (T) above the forest canopy were recorded. The sap flow measurement was used in combination with morphological characteristics of tree and forest structure to calculate the whole-tree transpiration (E), stand transpiration (E _t), and mean canopy stomatal conductance (g _c). Analyses on the relationships between tree morphological characters and whole-tree water use, and on the responses of g _c to PAR and vapor pressure deficit (D) were conducted. The results showed that whole-tree transpiration correlated significantly and positively with tree diameter at breast height (DBH) (p<0.0001), with sapwood area (p<0.0001), and with canopy size (p = 0.0007) logarithmically, but exponentially with tree height (p = 0.014). The analyses on the responses of canopy stomatal conductance showed that the maximum g _c (g _cmax) changed with PAR in a hyperbolic curve (p<0.0001) and with D in a logarithmic one (p<0.0001). The results obtained with sap flow technique indicate its reliability and accuracy of the methods of estimation of whole-tree and stand transpirations and canopy stomatal conductance. __________ Translated from Chinese Journal of Applied Ecology, 2006, 17(7): 1149–1156 [译自: 应用生态学报]     

石灰岩山地坡位对侧柏光合蒸腾特性的影响

为分析困难山地不同坡位侧柏光合和蒸腾作用等生理特性的差异,利用Li-6400便携式光合仪对石灰岩山地4种坡位侧柏的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、光合有效辐射(rPAR)、空气相对湿度(Hr)、气温(Ta)等指标进行测定.结果表明:不同坡位侧柏净光合速率最大值均出现在8:00,底坡和中坡侧柏在中午都出现午休现象;坡位越高,侧柏日均净光合速率越低.各样地侧柏蒸腾速率日变化均呈双峰曲线,日均蒸腾速率由大到小依次为顶坡＞平地＞中坡＞底坡.底坡侧柏气孔导度在中午时值最小,且日均水分利用效率最高.相关性分析表明,研究区侧柏光合蒸腾作用的主要影响因子是气孔导度、光合有效辐射和空气相对湿度,底坡是最适合侧柏生长的位置.     

Influence of canopy light environment and nitrogen availability on leaf photosynthetic characteristics and photosynthetic nitrogen-use efficiency of field-grown nectarine trees

Relationships between CO(2) assimilation at light saturation (A(max)), nitrogen (N) content and weight per unit area (W(A)) were studied in leaves grown with contrasting irradiances (outer canopy versus inner canopy) and N supply rates in field-grown nectarine trees Prunus persica L. Batsch. cv. Fantasia. Both A(max) and N content per unit leaf area (N(A)) were linearly correlated to W(A), but leaves in the high-N treatment had higher N(A) and A(max) for the same value of W(A) than leaves in the low-N treatment. The curvilinear relationship between photosynthesis and total leaf N was independent of treatments, both when expressed per unit leaf area A(maxA) and N(A)) and per unit leaf weight (A(maxW) and N(W)), but the relationship was stronger when data were expressed on a leaf area basis. Both A(maxA) and N(A) were higher for outer canopy leaves than for inner canopy leaves and A(maxW) and N(W) were higher for leaves in the high-N treatment than for leaves in the low-N treatment. The relationship between A(max) and N resulted in a similar photosynthetic nitrogen-use efficiency at light saturation (A(max)NUE) for both N and light treatments. Photosynthetic nitrogen-use efficiency was similar among treatments throughout the whole light response curve of photosynthesis. Leaves developed in shade conditions did not show higher N-use efficiency at low irradiance. At any intercellular CO(2) partial pressure (C(i)), photosynthetic CO(2) response curves were higher for outer canopy leaves and, within each light treatment, were higher for the high-N treatments than for the low-N treatments. Consequently, most of the differences among treatments disappeared when photosynthesis was expressed per unit N. However, slightly higher assimilation rates per unit N were found for outer canopy leaves compared with inner canopy leaves, in both N treatments. Because higher daily irradiance within the canopies of the low-N trees more than compensated for the lower photosynthetic performances of these leaves compared to the leaves of high-N trees, daily carbon gain (and N-use efficiency on a daily assimilation basis) per leaf was higher for the low-N treatment than for the high-N treatment in both outer and inner canopy leaves.     

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.     

叶面喷施"施丰乐"对板栗光合、蒸腾及保护性酶活性的影响

在板栗膨大期使用10 mg/L、20 mg/L、30 mg/L 3种不同浓度的“施丰乐”进行叶面喷施（清水对照）,并进行光合速率、蒸腾速率和几种保护性酶（超氧化物歧化酶SOD、过氧化物酶POD、多酚氧化酶PPO和过氧化氢酶CAT）活性的测定.结果表明：10 mg/L和20 mg/L的“施丰乐”可以提高板栗叶片光合速率,降低蒸腾速率.10 mg/L和20 mg/L的“施丰乐”可以显著地提高板栗叶片中的SOD, POD和PPO的活性,而30 mg/L却对SOD和POD起到抑制作用.同时,这3种浓度的“施丰乐”均提高了CAT的活性,但是效果不太明显.与10 mg/L和30 mg/L的喷施浓度比较,20 mg/L是最佳浓度,效果最为显著.     

杨树与栅锈菌互作过程中光合、蒸腾作用变化研究

利用LI-6400便携式光合仪对受落叶松-杨栅锈菌 Melampsora larici-populina Kleb.侵染后的杨树寄主的光合、蒸腾作用进行了动态监测.通过对不同抗性的杨树寄主在不同接种时间段的光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)以及蒸腾速率(Tp)活体监测后发现,在受到栅锈菌侵染后,抗病品种和感病品种的净光合速率、胞间CO2浓度均随接种时间的延长而逐渐下降.其中抗病品种内下降的幅度要比感病品种小.蒸腾速率在寄主受侵后开始逐渐下降直到开始产孢,但是在产孢后蒸腾速率就开始持续上升并超过健康寄主,并在产孢高峰达到最大值.气孔导度在接种后迅速增加,在产孢前后又开始大幅度的下降.这4个基本生理指标变化说明,栅锈菌侵染寄主后对寄主的光合、蒸腾作用均有影响,而且在亲合性组合中影响显著.     

小青花金龟成虫对苹果树危害的初步研究

为了有效防治苹果园内小青花金龟Oxycetonia jucunda Faldermann,作者系统地调查了成虫对苹果树Malus pumila花、叶的危害情况及其在苹果园浅土层内的种群分布规律。结果表明:小青花金龟成虫对苹果叶的平均危害率为32.02%,严重时达70%,显著高于对苹果花的平均危害率18.50%;小青花金龟成虫在浅土层内主要分布在以苹果树为中心0~40 cm半径内,随着半径的增加,虫口密度逐渐下降,半径0~40,40~80,80~120 cm范围内的虫口密度分别为28.03,12.79,8.95头/m2。     

山旱塬区花牛苹果树干茎流及其与环境因子的关系

为探明山旱塬区苹果园耗水规律以及影响果树耗水的主导因子,确定水分承载力,合理配置有限的水资源,于2014~2015年采用SF-L树干茎流仪和Watch Dog 2900ET自动气象站对山旱塬区花牛苹果树干茎流及环境因子进行了连续观测,分析了花牛苹果树干茎流速率的变化规律及其与环境因子的相关关系。结果表明,在果树生长周期,各月份根据日均茎流速率由大到小排列依次为5月、6月、7月、8月、9月,随着月份的递增,茎流峰值出现时间逐渐延迟;5~9月份苹果树干茎流速率变化规律表现为昼高夜低,7:00~9:00树干茎流速率开始急速上升,12:00~15:00达到最大值,17:00~18:00开始逐步下降,21:00趋于稳定;不同天气条件下苹果树干茎流速率为晴天大于雨天;对茎流速率与环境因子的相关性分析结果表明,太阳辐射强度、相对湿度、空气温度、饱和水气压差、露点温度与树干茎流速率呈极显著性相关,风速对茎流速率也有一定影响。     

4个苹果良种在兰州半干旱山地栽培适应性观察

经10年引种栽培试种，苹果良种新红星、长富2、皇家嘎拉、新乔纳金等4个品种在兰州半干旱山地栽培条件下，表现出生长结果良好，幼树生长旺、结果早、果实品质优良，丰产、稳定、越冬性好，生态适应性强的特点，可在生产上推广应用，栽培中应注意园地选择，适时补充灌溉，增施有机肥料等技术措施。     

Root and transpiration studies on young Norway spruce trees with die back symptoms in Sweden

In the spring of 1977, scattered trees in young plantations of Norway spruce showed discoloration and loss of 1976 needles on twigs just below the apex. The main roots of damaged trees were smaller than those of healthy trees, and the extension roots lacked short roots and mycorrhizae. The transpiration rate of the current shoots of damaged trees was also higher. The damage was assumed to be the result of drought during the two previous years; the trees were thought to differ genetically in their ability to withstand water stress.     

Impacts of seasonal air and soil temperatures on photosynthesis in Scots pine trees

Seasonal courses of light-saturated rate of net photosynthesis (A360) and stomatal conductance (gs) were examined in detached 1-year-old needles of Scots pine (Pinus sylvestris L.) from early April to mid-November. To evaluate the effects of soil frost and low soil temperatures on gas exchange, the extent and duration of soil frost, as well as the onset of soil warming, were manipulated in the field. During spring, early summer and autumn, the patterns of A360 and gs in needles from the control and warm-soil plots were generally strongly related to daily mean air temperatures and the frequency of severe frost. The warm-soil treatment had little effect on gas exchange, although mean soil temperature in the warm-soil plot was 3.8 degrees C higher than in the control plot during spring and summer, indicating that A360 and gs in needles from control trees were not limited by low soil temperature alone. In contrast, prolonged exposure to soil temperatures slightly above 0 degrees C severely restricted recovery of A360 and especially gs in needles from the cold-soil treatment during spring and early summer; however, full recovery of both A360 and gs occurred in late summer. We conclude that inhibition of A360 by low soil temperatures is related to both stomatal closure and effects on the biochemistry of photosynthesis, the relative importance of which appeared to vary during spring and early summer. During the autumn, soil temperatures as low as 8 degrees C did not affect either A360 or gs.