冬小麦不同生育期最上冠层阻力的估算

作物最小冠层阻力是研究农田蒸发和作物缺水的一个重要参数.使用作物的冠层红外温度信息,将作物在充分灌溉情况下冠层温度与空气温度之差与空气的饱和水汽压差的经验关系同其理论解释相结合,通过实验数据,估算了在华北平原气候条件下的冬小麦(Triticum aestivum L.)的平均最小冠层阻力,为基于这种阻力的应用提供基础.研究表明冬小麦最小冠层阻力随发育期而不同,并且抽穗前后差异明显,给出了冬小麦不同生育阶段的平均最小冠层阻力.     

华北平原冬小麦农田蒸散量

以华北平原冬小麦农田为研究对象,采用涡度相关技术和热红外遥感技术,研究了不同环境条件下土壤含水量与农田蒸散量及作物冠层温度的关系.结果表明,冬小麦在农田郁闭(LAI≥3)、晴天和土壤相对含水量低于田间持水量65%的情况下,蒸发比值日变化正午前后出现相对较低且平稳的变化趋势.在晴天情况下,农田潜热通量与作物冠层温度日变化和季节变化均呈极显著的非线性相关关系,而冠气温差、农田相对蒸散量则与0～100 cm土层的土壤相对含水量密切相关.以13:30～14:00的平均冠层温度值T_c、日最高气温T_{a max}和日净辐射总量Rn_d为统计数据,确立了冬小麦农田日蒸散量ET_d （mm）估算简化模式参数.     

冠层温度与冬小麦农田生态系统水分状况的关系

1　引　　言通过表面温度遥感监测作物和土壤水分一直是一个共同关注的问题,而该问题解决的一个基础是冠层温度与农田土壤湿度和作物水分状况的关系的研究.国内这方面的研究起步于80年代并已取得一些结果[1～3].但主要集中在冠层空气温度差与农田土壤湿度的关系上,对于冠层温度     

南方现代化温室黄瓜冬季蒸腾测量与模拟研究

 温室作物蒸腾直接影响到温室内空气温湿度,是进行温室温度和湿度优化调控所必需的信息。通过冬季温室小气候和蒸腾速率与气孔阻力的实验观测,分析了冬季南方温室黄瓜(Cucumis sativus)蒸腾速率的变化特征及其与温室小气候要素之间的定量关系,确定了南方现代温室冬季黄瓜冠层阻力rc和边界层动力学阻力ra的特征值和作物蒸腾消耗的潜热占到达冠层上方的净辐射的比例,并采用Penman-Monteith方法模拟计算了冬季温室内黄瓜作物蒸腾速率。结果表明,冬季温室内作物蒸腾速率的日变化趋势与净辐射的日变化基本一致,在正午达一天中的最大值。而空气饱和水汽压差（VPD）的日最大值则基本出现在午后1～2 h。在我国南方温室冬季高湿的环境下（VPD<2 kPa）,作物蒸腾速率日变化主要取决于太阳辐射日变化。冠层上方的净辐射和VPD及作物冠层蒸腾速率日最大值分别在350 W·m－2、2.0 kPa和200 W·m－2以下。冬季温室作物蒸腾消耗的潜热占到达冠层上方的净辐射的比例为46%。冬季黄瓜作物的rc和ra特征值分别为100 s·m-1和600 s·m-1。采用实际变化的rc与ra值和rc与ra的特征值计算的作物蒸腾速率和累积蒸腾量均与实测值基本一致。作物蒸腾消耗的潜热占到达冠层上方的净辐射的比例及rc和ra特征值的确定为研制基于作物蒸腾模型的温室环境和肥水灌溉的优化控制系统奠定了基础。但研究所确定的这些特征值在其它地区和其它类型温室是否适用,尚需进一步的实验资料来证明。     

开放式空气CO2浓度增高对水稻冠层微气候的影响

利用位于江苏省无锡市安镇的我国唯一的农田开放式空气CO₂浓度增高(FACE)系统平台,于2001年8月26日至10月13日(水稻抽穗至成熟期)进行水稻作物冠层微气候连续观测,以研究FACE对水稻冠层微气候特征的影响.结果表明,FACE降低了水稻叶片的气孔导度,FACE与对照水稻叶片气孔导度的差异上层叶片大于下层叶片,生长前期大于生长后期.FACE使白天水稻冠层和叶片温度升高,这种差异生长前期大于生长后期;但FACE对夜间水稻冠层温度的影响不明显.在水稻旺盛生长的抽穗开花期,晴天正午前后FACE水稻冠层温度比对照高1.2℃;从开花至成熟期,FACE水稻冠层白天平均温度比对照高0.43℃.FACE对冠层空气温度也有影响,白天水稻冠层空气温度FACE高于对照,这种差异随太阳辐射增强而增大且冠层中部大于冠层顶部;冠层中部空气温度FACE与对照的差异(T_face-T_ambient)日最大值在0.47～1.2℃之间,而冠层顶部的T_face-T_ambient日最大值在0.37～0.8℃之间.夜间水稻冠层空气温度FACE与对照差别不大,变化在±0.3℃之内.而FACE对水稻冠层空气湿度无显著影响,表明FACE使水稻叶片气孔导度降低,从而削弱了植株的蒸腾降温作用,导致水稻冠层温度和冠层空气温度升高,改变了整个水稻冠层的温度环     

水分胁迫与光照条件对棉花干物质和产量形成影响的数学模型

从作物冠层净同化速率入手,通过引入对CO2浓度、空气湿度、光照强度和土壤含水量反映较敏感的光能利用系数（β）,建立了考虑水分胁迫和光照条件对作物干物质积累与产量形成影响的数学模型,模型考虑了水分胁迫与低光照下冠层阻力增加的设定,将反映作物冠层水分状况的功能叶水势（Ψl）作为参数纳入本模型,通过对土壤相对含水量（Aw)、气温（Ta）、水汽压差（VPD）的多元回归估算出Ψl,并将空气动力学阻力（Ra）简化为风速（u）的函数,盆载试验应用实例和敏感性分析表明,该模型在诊断环境因子特别是土壤水分与光照因子对作物生长和产量构成的影响具有一定的实用性。     

开放式空气CO2浓度增高对水稻冠层微气候的影响

利用位于江苏省无锡市安镇的我国唯一的农田开放式空气CO2 浓度增高 (FACE)系统平台 ,于2 0 0 1年 8月 2 6日至 10月 13日 (水稻抽穗至成熟期 )进行水稻作物冠层微气候连续观测 ,以研究FACE对水稻冠层微气候特征的影响 .结果表明 ,FACE降低了水稻叶片的气孔导度 ,FACE与对照水稻叶片气孔导度的差异上层叶片大于下层叶片 ,生长前期大于生长后期 .FACE使白天水稻冠层和叶片温度升高 ,这种差异生长前期大于生长后期 ;但FACE对夜间水稻冠层温度的影响不明显 .在水稻旺盛生长的抽穗开花期 ,晴天正午前后FACE水稻冠层温度比对照高 1.2℃ ;从开花至成熟期 ,FACE水稻冠层白天平均温度比对照高 0 .4 3℃ .FACE对冠层空气温度也有影响 ,白天水稻冠层空气温度FACE高于对照 ,这种差异随太阳辐射增强而增大且冠层中部大于冠层顶部 ;冠层中部空气温度FACE与对照的差异 (Tface-Tambient)日最大值在 0 .4 7～ 1.2℃之间 ,而冠层顶部的Tface-Tambient日最大值在 0 .37～ 0 .8℃之间 .夜间水稻冠层空气温度FACE与对照差别不大 ,变化在± 0 .3℃之内 .而FACE对水稻冠层空气湿度无显著影响 ,表明FACE使水稻叶片气孔导度降低 ,从而削弱了植株的蒸腾降温作用 ,导致水稻冠层温度和冠层空气温度升高 ,改变了整个水稻冠层的温度环     

冠层温度在水稻抗旱性基因型筛选中的应用及其测定技术

本文综述了冠层温度在水稻抗旱性基因型筛选中的应用及其研究进展,并介绍了利用红外测温仪测定冠层温度的方法。作物不同基因型之间存在冠层温度的差异,并且从理论上讲,冠层温度与作物水分利用相关,因而把冠层温度用于作物基因型筛选是有价值而且是可行的。利用红外测温仪测定水稻冠层温度是一项非接触性测温法,为水稻抗旱性基因型的筛选提供了一种简便、快速、非破坏性的技术。     

冠层温度在水稻抗旱性基因型筛选中的应用及其测定技术

本文综述了冠层温度在水稻抗旱性基因型筛选中的应用及其研究进展,并介绍了利用红外测温仪测定冠层温度的方法。作物不同基因型之间存在冠层温度的差异,并且从理论上讲,冠层温度与作物水分利用相关,因而把冠层温度作于作物基因型筛选是有价值而且是可行的。利用红外测温仪测定水稻冠层温度是一顶非接触性测温法,为水稻抗旱性基因型的筛选提供了一种简便、快速、非破坏性的技术。     

旱地冬小麦灌浆期冠层温度与产量和水分利用效率的关系

利用红外测温仪,于2005～2006年在甘肃陇东旱原研究了我国北方冬麦区域的23个小麦品种(系)灌浆不同时期冠层温度的差异及其与产量和水分利用效率的关系。结果表明,不同基因型小麦在籽粒灌浆结实期存在着冠层温度高度分异的现象,其分异程度随灌浆过程的进行明显加大,到灌浆中后期达到最大。无论灌浆初期还是中期或中后期,旱地冬小麦产量、水分利用效率与冠层温度均呈极显著的负相关(R2=0.445-0.812),并且随着灌浆期推移,相关性增大,灌浆中后期冠层温度每升高1℃,旱地冬小麦产量减少近280 kg hm-2,水分利用效率下降约0.6 kg hm-2mm-1。灌浆中期以后不同基因型小麦冠层温度保持较高的一致性,冠层温度偏低的品种具有较高的产量和水分利用效率。灌浆中后期的冠层温度在评价小麦产量和水分利用效率上具有较高的可靠性,可作为一个田间选择指标应用。     

Genotypic difference in canopy diffusive conductance measured by a new remote-sensing method and its association with the difference in rice yield potential

There have been few practical ways of measuring physiological determinants of rice yield. Rapid evaluation of yield determination traits may expedite breeding of high-yielding rice. Here, we report a new remote-sensing technique for the evaluation of canopy ecophysiological status under field conditions developed based on simultaneous measurements of sunlit and suddenly shaded canopy temperatures. This technique has the advantage of instantaneous estimation of aerodynamic resistance (r(a)) and canopy diffusive resistance (r(c) without measuring wind velocity. Canopy diffusive conductance (1 / r(c)) estimated by the remote sensing method was closely related to leaf stomatal conductance (g(s)) measured with a portable gas exchange system. This result supported the validity of this new method for quantitative estimation of canopy physiological characteristics. Significant genotypic differences were obtained in canopy-air temperature difference (Tc-Ta), r(c) and 1 / r(c) during the 2-week period preceding full heading for two years, and 1 / r(c) was highly correlated with crop growth rate (CGR), which was closely related to the final yield. These results suggest that 1 / r(c) can be an effective criterion for the selection of high-yielding rice genotypes, and the remote sensing technique proposed here can be a powerful tool for the rapid evaluation of 1 / r(c) under field conditions.     

田间小麦群体内叶片气孔阻力垂直差异研究

根据田间实测资料, 本文给出了田间小麦群体中叶片不同部位和冠层不同层次叶面气孔阻力的差异, 及其与环境因素特别是土壤水分含量关系的分析结果。结果表明, 小麦冠层各不同层次和叶片不同部位的气孔阻力有明显差异。就冠层上部单个叶片而言, 由叶尖到叶基气孔阻力逐渐增大;叶片正面的气孔阻力小于叶片反面对应部位的气孔阻力。对于水汽和CO₂传导的贡献70%是由冠层上部的两片叶子给出的;群体内不同层次叶片相应部位的气孔阻力是由冠层上部向下逐渐增大, 冠层不同层次叶片和叶片不同部位的气孔对环境因素变化的反空不同, 如当土壤水分不足时, 群体下部叶片和叶片反面的气孔张度首先变小, 且变小的程度较大。     

Microclimate and fluxes of water vapour, sensible heat and carbon dioxide in structurally differing subalpine plant communities in the Central Caucasus

Effects of canopy structure on microclimate, energy budget and CO₂ exchange were analysed in a pasture, two hay meadows, a tall herb community and a dwarf shrub community in the subalpine belt of the Central Caucasus. The results show that canopy structure exerts a marked influence on the distribution of photon flux density, temperature and canopy photosynthesis A_c. Three canopy types were distinguished. Type 1 (pasture) has a small LAI (leaf area index) and more than two-thirds of the phytomass is concentrated in the lowest few cm of the canopy, mainly as planophile leaves. This results in (1) a low degree of utilization of photosynthetic photon flux density (PPFD) by assimilatory plant components, (2) high leaf temperatures and a high soil heat flux during the phase of incoming radiation, and (3) a relatively low A_c/ LAI ratio. Type 2 (meadows), in spite of its erect leaves, which at high solar elevations permit light to penetrate to the lower canopy layers, is characterized by (1) marked effects of mutual shading in the lower canopy layers for most of the day, and thus (2) only slight variations in air and leaf temperatures and (3) a comparatively low A_c/LAI ratio. In canopies of type 3 (tall herb and dwarf shrub communities), there is a concentration of flat leaves in the upper layers. This results in (1) very good utilization of PPFD; (2) no strong fluctuations in canopy temperature as the flat leaves act as a buffer, reducing the amounts of incoming and outgoing radiation in lower canopy layers, and (3) high values of the A_c/LAI ratio. The energy budgets of the canopies investigated are governed not so much by their spatial structure, but rather indirectly by LAI and the degree of coupling of the canopy with the atmosphere.     

黄土高原苹果园蒸腾导度大气驱动规律比较

植物蒸腾导度是表征土壤-植物-大气连续体（SPAC）中植物-大气间水汽传导过程、反映植物水分调控能力的一类重要变量,常见有冠层导度（G_c）、冠层气孔导度（G_s）与叶片气孔导度（g_s）,明确三者在反映冠层蒸腾过程时的异同或关联性对于理解植物水分利用机制具有重要意义。本研究基于对黄土高原果园苹果树生长季内树干液流（J_s）及环境因子的连续观测,计算了G_c、G_s及脱耦联系数（Ω）等变量,并与短期连续观测的叶片气孔导度（g_s）比较,分析了G_c、G_s和g_s在反映冠层蒸腾特征方面的异同及其关系。结果表明,日变化过程中G_s、g_s呈"单峰"型曲线,而G_c则呈"先增后减,午后抬升"的"双峰"型曲线。g_s与G_s存在较紧密的线性关系（R²=0.80）,但与G_c的线性关系较弱（R²=0.02）。G_c、G_s均随大气水汽压亏缺（VPD）的变化呈现确定的规律,其中,上边界函数呈递减的对数函数关系,平均值则符合先增后减的Log-Normal函数关系（R²>0.95）,拐点对应的VPD值分别为1.33和1.16 kPa。在一日内,G_s对VPD变化的响应过程与g_s对VPDL （基于叶片温度计算的水汽压亏缺）变化的响应过程总体一致,其一致性高于G_c对VPD变化的响应。整个生长季（4-10月）中果树的Ω平均值为0.12,随着Ω递减,G_c与G_s的线性相关性愈趋紧密,其斜率呈递增趋势,G_c越来越趋近于G_s。研究结果表明,在北方地区,基于树干液流的监测能较准确的推导整株并估算林分的冠层蒸腾导度。与实测g_s的变化过程比较,G_s比G_c具有更高的一致性,G_s可以作为描述苹果树水分利用过程响应大气驱动的更为恰当的变量。     

Three-dimensional soil heterogeneity modulates responses of grassland mesocosms to an experimentally imposed drought extreme

Heterogeneity is an intrinsic characteristic of soils, which regulates plant diversity and ecosystem functioning. However, whether soil heterogeneity also modulates responses of plant communities to climate change, including climate extremes, remains largely an open question. Here, we explore responses of plant communities to drought extremes across four levels of spatial soil heterogeneity, with cell sizes varying from very small to very large, i.e. 0, 12, 24 and 48 cm. These were created in mesocosms by alternating nutrient-rich and nutrient-poor substrate in three dimensions. A seed mixture of 24 grassland species was evenly sown on each mesocosm in spring. In late summer, a three-week drought was imposed with a rainout shelter. During the drought, soil water content at the mesocosm scale decreased more at intermediate (12 and 24 cm) than at small or large (0 and 48 cm) cell sizes, which was reflected in increased senescence and drought-induced heat stress. These responses could be traced to greater plant biomass coupled with higher water demand at those intermediate cell sizes, likely related to between-cell access to nutrients and effects of diversity and community composition. Our results indicate that soil heterogeneity can modulate the impact of drought extremes on plant communities, though more research is needed on the transition between intermediate and extreme cell sizes, where heterogeneity effects seem to change most. We propose that soil heterogeneity be considered more explicitly in studies of changing precipitation regimes.     

基于Penman-Monteith方程模拟青海云杉生长季日蒸腾过程

青海云杉（Picea crassifolia）作为我国黄土高原与青藏高原地区的主要造林树种,对其林分蒸腾耗水特征的研究,能够更合理的指导该地区植被重建与林分调控,以加强林分的稳定性,提高水分利用效率。为了揭示青海云杉在生长季内的冠层蒸腾规律以及冠层整体气孔阻力与环境因子的响应,评价Penman-Monteith方程在青海云杉冠层尺度上的适用性,采用探针式热扩散茎流计（TDP）进行测定,同步长期监测了环境数据,利用反推法建立冠层整体气孔阻力（r_sT）与环境因子之间的回归模型,结合Penman-Monteith方程模拟出青海云杉生长季的日蒸腾量,采用均方根误差、平均绝对误差和平均相对误差对蒸腾量的实测值与模拟值进行误差分析,以验证模型的准确性。得出的主要结论有：（1）生长季内青海云杉日蒸腾量随月份变化呈先增高后降低的趋势;各月蒸腾量占潜在蒸散量的比例为7月（79.68%） > 8月（72.71%） > 6月（72.53%） > 5月（67.08%） > 9月（66.48%） > 10月（64.29%）;（2）树干液流对气象因子的滞后时间为0.5 h;（3）不同月份云杉冠层整体气孔阻力（r_sT）与空气相对湿度（RH）呈正相关关系,与大气温度（T）、饱和水汽压差（VPD）呈负相关关系;（4）应用所建立的多因素回归模型结合Penman-Monteith方程对青海云杉蒸腾量进行模拟验证,累计平均相对误差为14.381%,平均绝对误差为0.160 mm,均方根误差为0.2。综上所述,Penman-Monteith方程在林分冠层尺度上有较好适用性根据所建立的多因素回归模型并结合Penman-Monteith方程,可以利用饱和水汽压差、温度和空气相对湿度三个气象因子较好地模拟日蒸腾过程。     

森林冠层昆虫多样性研究方法

森林冠层是森林昆虫栖息、取食、避敌的重要生境,其中生活着十分丰富的昆虫物种。但由于乔木树体高大,冠层难于接近,在很大程度上限制了冠层昆虫多样性的研究。冠层昆虫类群结构的划分和冠层昆虫取样技术也是冠层昆虫多样性研究的重要基础。文章综述当前冠层接近和冠层昆虫抽样技术的最新进展,并评述冠层昆虫类群结构划分的方法。     

云南亚高山云冷杉林林窗的研究

研究了云南碧塔海两块亚高山云冷杉（Ｐｉｃｅａ－Ａｂｉｅｓ）林内中小尺度林窗的干扰体系,结果表明：林窗和扩展林窗分别占林地面积的１９％和４１％,平均面积为４４ｍ２和１３９ｍ２,林窗的形成频率为０．００５～０．００７／ｙ。估计平均林窗周期为１６７年。大多数林窗（占８７％）的制造林窗树木（ｇａｐ－ｍａｋｅｒ,简记为ＧＭ）为１个以上,平均每个林窗的ＧＭ为２．９个,同一林窗内的ＧＭ常常死于不同的时间。在所有调查的ＧＭ中,折断占６０％,而根拔和直立死亡分别为２８％和１２％     

Vertical stratification of feeding guilds and body size in beetle assemblages from an Australian tropical rainforest

Abstract The vertical stratification of insect species assemblages inhabiting tropical rainforests is well established but few have examined whether these patterns are reflected in vertical stratification of body size or feeding guilds. We used Malaise and Flight Interception Traps to sample beetle assemblages from five locations, at both canopy and ground zones of a tropical lowland rainforest site near Cape Tribulation, Australia. Beetles from 4 years of sampling were sorted to Family and morphospecies, and allocated to one of five feeding guilds. Within feeding guilds the number of species and individuals, from canopy‐ and ground‐caught traps were compared. The body lengths of species were measure and compared within feeding guilds and families. Herbivores was the dominant guild but was not the majority of all species or individuals. Most beetle species (69%) were less than 5 mm in length and the mean size of canopy‐caught species was greater than that for ground‐caught species. This was probably due to slightly more species of plant feeders (herbivores and xylophages) present in the canopy, which were significantly larger than saprophages, fungivores and predators. Among feeding guilds, there were few overall canopy–ground differences. These results contrast with species composition results presented elsewhere where strong differences between the canopy and the ground were evident. We suggest that our guild groupings may have been too coarse to detect fine‐scale differences and that resource partitioning may have also masked faunal stratification. We propose that fine‐scale differences in resources between the canopy and the ground, together with strong microclimate gradients, are likely to be important in structuring the vertical stratification of insect assemblages at the level of species, but not with respect to functional groups.