Sensitivity of terrestrial water and energy budgets to CO(2)-physiological forcing: an investigation using an offline land model

Increasing concentrations of atmospheric carbon dioxide (CO(2)) influence climate by suppressing canopy transpiration in addition to its well- known greenhouse gas effect. The decrease in plant transpiration is due to changes in plant physiology (reduced opening of plant stomata). Here, we quantify such changes in water flux for various levels of CO(2) concentrations using the National Center for Atmospheric Research's (NCAR) Community Land Model. We find that photosynthesis saturates after 800 ppmv (parts per million, by volume) in this model. However, unlike photosynthesis, canopy transpiration continues to decline at about 5.1% per 100 ppmv increase in CO(2) levels. We also find that the associated reduction in latent heat flux is primarily compensated by increased sensible heat flux. The continued decline in canopy transpiration and subsequent increase in sensible heat flux at elevated CO(2) levels implies that incremental warming associated with the physiological effect of CO(2) will not abate at higher CO(2) concentrations, indicating important consequences for the global water and carbon cycles from anthropogenic CO(2) emissions.

Climate response to changes in atmospheric carbon dioxide and solar irradiance on the time scale of days to weeks

Recent studies show that fast climate response on time scales of less than a month can have important implications for long-term climate change. In this study, we investigate climate response on the time scale of days to weeks to a step-function quadrupling of atmospheric CO2 and contrast this with the response to a 4% increase in solar irradiance. Our simulations show that significant climate effects occur within days of a stepwise increase in both atmospheric CO2 content and solar irradiance. Over ocean, increased atmospheric CO2 warms the lower troposphere more than the surface, increasing atmospheric stability, moistening the boundary layer, and suppressing evaporation and precipitation. In contrast, over ocean, increased solar irradiance warms the lower troposphere to a much lesser extent, causing a much smaller change in evaporation and precipitation. Over land, both increased CO2 and increased solar irradiance cause rapid surface warming that tends to increase both evaporation and precipitation. However, the physiological effect of increased atmospheric CO2 on plant stomata reduces plant transpiration, drying the boundary layer and decreasing precipitation. This effect does not occur with increased solar irradiance. Therefore, differences in climatic effects from CO2 versus solar forcing are manifested within days after the forcing is imposed.

High Temperatures Result in Smaller Nurseries which Lower Reproduction of Pollinators and Parasites in a Brood Site Pollination Mutualism

In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3-5 degrees C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig-pollinator association across seasons. Non-pollinator parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology via the feedback cycle in this system. Climatic factors affecting plant reproductive traits cause biotic relationships between plants, mutualists and parasites to vary seasonally and must be accorded greater attention, especially in the context of climate change.

Conjugate Model for Heat and Mass Transfer of Porous Wall in the High Temperature Gas Flow

Heat and mass transfer of a porous permeable wall in a high temperature gas dynamical flow is considered. Numerical simulation is conducted on the ground of the conjugate mathematical model which includes filtration and heat transfer equations in a porous body and boundary layer equations on its surface. Such an approach enables one to take into account complex interaction between heat and mass transfer in the gasdynamical flow and in the structure subjected to this flow. The main attention is given to the impact of the intraporous heat transfer intensity on the transpiration cooling efficiency.

The variations and climatic significance of D/H ratios in the carbon-bound hydrogen of cellulose in trees

The σD values of nitrated cellulose from a variety of trees covering a wide geographic range have been measured. These measurements have been used to ascertain which factors are likely to cause σD variations in cellulose C-H hydrogen.

It is found that a primary source of tree σD variation is the σD variation of the environmental precipitation. Superimposed on this are isotopic variations caused by the transpiration of the leaf water incorporated by the tree. The magnitude of this transpiration effect appears to be related to relative humidity.

Within a single tree, it is found that the hydrogen isotope variations which occur for a ring sequence in one radial direction may not be exactly the same as those which occur in a different direction. Such heterogeneities appear most likely to occur in trees with asymmetric ring patterns that contain reaction wood. In the absence of reaction wood such heterogeneities do not seem to occur. Thus, hydrogen isotope analyses of tree ring sequences should be performed on trees which do not contain reaction wood.

Comparisons of tree σD variations with variations in local climate are performed on two levels: spatial and temporal. It is found that the σD values of 20 North American trees from a wide geographic range are reasonably well-correlated with the corresponding average annual temperature. The correlation is similar to that observed for a comparison of the σD values of annual precipitation of 11 North American sites with annual temperature. However, it appears that this correlation is significantly disrupted by trees which grew on poorly drained sites such as those in stagnant marshes. Therefore, site selection may be important in choosing trees for climatic interpretation of σD values, although proper sites do not seem to be uncommon.

The measurement of σD values in 5-year samples from the tree ring sequences of 13 trees from 11 North American sites reveals a variety of relationships with local climate. As it was for the spatial σD vs climate comparison, site selection is also apparently important for temporal tree σD vs climate comparisons. Again, it seems that poorly-drained sites are to be avoided. For nine trees from different "well-behaved" sites, it was found that the local climatic variable best related to the σD variations was not the same for all sites.

Two of these trees showed a strong negative correlation with the amount of local summer precipitation. Consideration of factors likely to influence the isotopic composition of summer rain suggests that rainfall intensity may be important. The higher the intensity, the lower the σD value. Such an effect might explain the negative correlation of σD vs summer precipitation amount for these two trees. A third tree also exhibited a strong correlation with summer climate, but in this instance it was a positive correlation of σD with summer temperature.

The remaining six trees exhibited the best correlation between σD values and local annual climate. However, in none of these six cases was it annual temperature that was the most important variable. In fact annual temperature commonly showed no relationship at all with tree σD values. Instead, it was found that a simple mass balance model incorporating two basic assumptions yielded parameters which produced the best relationships with tree σD values. First, it was assumed that the σD values of these six trees reflected the σD values of annual precipitation incorporated by these trees. Second, it was assumed that the σD value of the annual precipitation was a weighted average of two seasonal isotopic components: summer and winter. Mass balance equations derived from these assumptions yielded combinations of variables that commonly showed a relationship with tree σD values where none had previously been discerned.

It was found for these "well-behaved" trees that not all sample intervals in a σD vs local climate plot fell along a well-defined trend. These departures from the local σD VS climate norm were defined as "anomalous". Some of these anomalous intervals were common to trees from different locales. When such widespread commonalty of an anomalous interval occurred, it was observed that the interval corresponded to an interval in which drought had existed in the North American Great Plains.

Consequently, there appears to be a combination of both local and large scale climatic information in the σD variations of tree cellulose C-H hydrogen.

Avaliação das concentrações de BTEX em ambiente indoor: estudo de caso da sala de spinning de uma academia de ginástica Rio de Janeiro / RJ.

Muitos dos locais onde as atividades são realizadas nas academias de ginásticas são salas pequenas e fechadas com sistema de climatização artificial, freqüentados por um grande número de alunos realizando seus exercícios e profissionais auxiliando as atividades. Com isso, há uma intensa transpiração desses indivíduos, uma freqüente rotina de limpeza do piso e de equipamentos com pequenos intervalos, possibilitando a alterações da qualidade do ar indoor. O presente trabalho busca mostrar as tendências de variações nos valores das concentrações dos poluentes atmosféricos BTEX em ambiente indoor, especificamente na sala de spinning de uma academia de ginástica do Rio de Janeiro. Para o monitoramento da qualidade do ar foram utilizados cartuchos de carvão ativado SKC, acoplado a uma bomba KNF com vazão de 1l min. Para a extração de cada amostra foi feita a análise cromatográfica com cromatógrafo a gás modelo 6890 acoplado a um espectrômetro de massa modelo 5973 da marca Agilent. Foram analisadas 34 amostras coletadas na salas de spinning durante as aulas com atividades aeróbicas, o que intensificava a respiração dos indivíduos, possibilitando uma maior inalação destes COVs. Em contrapartida, também foram coletadas 5 amostras outdoor, 4 delas pareadas indoor/ outdoor para uma análise comparativa das concentrações destes poluentes. Dentre os compostos orgânicos voláteis analisados, o tolueno é o BTEX mais abundante obtido neste trabalho, representando 81% destes COVs indoor. Todas as amostras medidas em pares indoor/ outdoor tiveram concentrações maiores no interior, exceto para o benzeno no dia 3/12/2010. Simples atividades usualmente realizadas pelo homem, como a inserção de piso emborrachado, manutenção do sistema de climatização artificial, e limpeza podem alterar o ar indoor. As conclusões alcançadas após as medições das concentrações de BTEX foram de que o ar indoor estava mais poluído do que o outdoor. Este monitoramento da qualidade do ar indoor ainda é escasso no Brasil. Alguns esforços tem sido feito em relação a ambientes confinados como a Portaria n˚3523 do Ministério da Saúde, regulamentando o controle dos ambientes climatizados e a Resolução n˚9 da Agência Nacional de Vigilância Sanitária, além da Resolução CONAMA n ˚3 estabelecendo padrões de qualidade do ar para alguns compostos químicos, porém muitos compostos químicos ainda não são legislados ou não possuem a devida atenção, não sendo suficientes para contemplar a complexidade do assunto

拟南芥有性生殖模式和叶片特性对大气CO2浓度变化的响应

预计到本世纪末，大气CO2浓度将会增加到540～970ppm，大气CO2浓度升高所引起的全球气候变化已经受到广泛的关注。植物生长依赖CO2，并且对大气CO2浓度升高在结构和生理上产生响应。目前已有大量报道，从生态系统、群落、种群、个体、器官、组织、生理以及生化等水平上研究高浓度CO2所对植物产生的影响。但是有关高浓度CO2对植物有性生殖影响的报道却很少，同时多数实验均建立在短期的生殖响应，忽视了植物在长期高CO2浓度下具有的反馈作用和CO2浓度变化对植物的驯化作用。植物有性生殖与其生态适应性和农作物籽粒产量的关系极为密切;同时，植物有性生殖特性的变化，也可作为预测植物对全球气候变化响应的重要指标之一。为此，利用高浓度CO2对植物进行长期选择实验将很有必要。研究结果将为预测未来大气CO2浓度增加的条件下陆地生态系统的演变趋势、全球变化对植物有性生殖响应的方式和机制提供新的思路和有效方法。 　　在本研究中，我们以模式植物拟南芥(Arabidopsis thaliana)作为实验材料，利用370和700ppm CO2对其进行连续8个世代处理，首先研究高浓度CO2对每一个世代的拟南芥有性生殖特性的影响，然后比较各个世代中各种生殖特性指标变化的规律，从细胞、组织和个体尺度上揭示拟南芥有性生殖对全球变化的响应模式。此外，在700ppm CO2处理下，我们对拟南芥叶片生理、生化以及结构的变化进行了相关研究。两部分研究结果及主要结论如下： 　　首先，在每一个世代中，与370ppm CO2相比较，700ppm CO2处理显著促进了拟南芥开花，缩短生长周期，增加花、角果及种子等生殖的产量，降低种子N含量，提高种子C/N比、种子千粒重以及生殖生物量所占总生物量的比例等，而对种子萌发率、角果所含种子数目以及角果长度则无显著影响。但是， 通过对相同CO2浓度处理条件下，不同世代之间的研究结果比较发现，不同世代之间相关的生殖生物学指标并无显著差异。 　　其次，高浓度CO2显著降低叶片气孔密度、气孔指数、气孔导度以及蒸腾速率。在高浓度CO2处理下，叶肉细胞中叶绿体数目、叶绿体宽度和表观面积、淀粉粒大小和数量、叶片和细胞壁厚度等都显著增加，但是基粒内囊体膜的数量却显著下降。叶片中碳水化合物如可溶性总糖、淀粉以及纤维素含量在高浓度CO2下分别显著增加71.9%、78.7% 和 22.3%。此外，在高浓度CO2处理下，叶片中多数激素如如吲哚乙酸(indole-3-acetic acid, IAA)、赤霉素(gibberellin, GA)、玉米素核苷(zeatin riboside, ZR)、二氢玉米素核苷(dihydrozeatin riboside, DHZR)和异戊烯基腺苷(isopentenyl adenosine, iPA)均都显著地增加，而脱落酸(abscisic acid, ABA)含量却有所下降。最后，叶片中各种矿物质元素含量如N、P、K、Ca和Mg等含量在高浓度CO2处理下也都显著下降，而C/N比增加24.8％。 　　以上结果表明： 　　(1) 在每一个世代中，700ppm CO2处理对拟南芥各种有性生殖特性具有显著的影响，但是高浓度CO2处理对植物所引起的效应在多个世代以内并不能够传递给后代，所以在多个有性生殖世代内，高浓度CO2处理对植物生长、生殖没有驯化作用。 　　(2) 在高浓度CO2处理下，拟南芥叶片中叶绿体超微结构的变化，可能主要是由于叶绿体中淀粉粒数量和体积大小显著增加而引起。 　　(3) 在高浓度CO2处理下，由于拟南芥叶片内与促进细胞分裂与伸长的激素含量显著增加，从而对拟南芥植株生长发育速率的提高起了重要的作用。 　　(4) 拟南芥生长在高浓度CO2条件下，其叶片中各种矿质元素含量（如N、P、K、Ca和Mg）均显著降低，究其原因可能是，第一由于叶片中碳水化合物含量的显著增加而对矿物质元素具有稀释作用;第二由于蒸腾速率下降，引起矿质元素从根部随着蒸腾流运输到地上部分的含量相应减少。 　　

腾格里沙漠沙坡头地区几种植物水分生理生态特性的比较研究

本研究是中日合作项目“中国沙漠化机制及其控制”下的子项目“人工环境下植物抗逆性及其生理生态特性研究”的一个重要部分。研究工作选取腾格里沙漠东南缘的沙坡头地区作为研究地点和种子采集地，选择分布于不同类型沙丘的一年生草本作为供试植物。 通过对两种沙生植物沙米(Aqriophyllum squarrosum)和雾冰藜（Bassia dasyphylla)水分生理生态特性的比较研究，野外调查与控制环境下的生理生态学研究相结合，探讨了它们对不同水分生境的适应性。 结果表明，水分胁迫下沙米（流动沙丘先锋种）与雾冰藜（半固定和固定沙丘伴生种）表现出不同的生理生态特性，即沙米对水分胁迫比雾冰藜更为敏感，表现出不耐旱的水分生理生态特性;而雾冰藜则表现出旱生植物的水分生理生态特性。联系其分布生境水分条件可知，沙米和雾冰藜水分生理生态特性的差异是导致二者分布生境不同的主要原因之一。 本研究同时也从气孔功能的角度探讨了水分胁迫下植物蒸腾和光合速率下降的可能原因，并就本实验结果讨论了流动沙丘先锋植物沙米的生态类型划分及其对流动沙丘沙埋逆境的适应性。

毛乌素沙地沙生灌木的生理生态学结构与功能

毛乌素沙地处于鄂尔多斯生态过渡带，在生态学研究上具有重要的理论与实践意义。在这样一个典型的半干旱区，水分是影响生态系统功能的最主要的限制因子，在沙基质土壤条件下，灌木得到充分发育，而乔木及草本植物则处于相对次要的地位。由于自然植被的初级生产力主要由灌木形成，故对于灌木在生态系统中的功能的系统研究是十分重要的，但目前又未得到应有重视。在荒漠化防治当中，这一点显得尤其急迫。此外，为了较好地预测该地区生态系统对全球气候变化的响应模式，急需要建立对主要乡土灌木功能型的划分方案。本研究运用植物生理生态学的方法，从植物的结构与功能的统一性出发，探讨了上述若干问题。主要结果与结论如下： 1．讨论了气候及土壤基质作为基本的环境背景，对沙生灌木生态功能的塑造作用，尤其探讨了若干土壤物理特性与植物水分利用的关系问题。 2．光学显微解剖及电子显微镜的观察表明，在自东南至西北横贯毛乌素沙地的水分梯度上生长的灌木当中，存在鲜明的叶片结构与功能特征与水分胁迫程度之间的对应性，在自东南向西北随干旱胁迫强度的增加，灌木的旱生结构也明显增加，甚至于在鄂尔多斯西部可以见到不少超旱生植物。同时，对灌木水分关系的研究支持了以解剖学观察为基础的认识，即：不同的景观条件下，也存在灌木的抗旱性与其生长的土壤的水分可利用性之间的对应性。这显示了水分因素在灌木的生态功能发挥中所起的主导作用。 3．通过分析沙丘的水分平衡，得到如下认识：(1)沙地条件的蒸发散主要来自植物的蒸腾作用，而土壤蒸发只占10%稍多：(2)沙地凝结水对灌木的水分需求而言微乎其微：(3)对多数沙生灌木而言，适宜的种植密度应为30-40%，即相当于半固定沙丘的覆盖度。 4．在上述三点的基础上，探讨了在不同类型的干旱（气候干旱、基质干旱及生理干旱）影响下，灌木在种类组成及干旱适应对策方面的多样性，将毛乌素沙地的灌木概括为两个功能类型：(1)干旱忍耐者;(2)竞争消费者。上述将极其多样的灌木物种在水分生态功能的相似性这个层面上概括成较少的类别的偿试，可望促使该地区的灌木生态学基础研究走向深入。 5．本研究对个别灌木的生态特性的新认识： ● 关于沙地柏(Sabina vulgaris)：(1)现已知道其蒸腾速率极低，本研究进一步认识到，低的蒸腾速率主要来自于气孔在叶表面上局限性分布：(2)该灌木虽十分抗旱，但过大的密度常引起叶片水分亏缺，在其根系不能利用地下潜水时．叶片水分亏缺更严重。 ● 关于油蒿(Artermisia．ordosica)及籽蒿（Asphaerocephala)：现已广泛地观察到，这两种灌木在沙丘演替不同阶段呈不同的优势分布：籽蒿主要生长于流动性沙丘（这里水分条件往往很好），但随沙丘逐渐被固定，就会被油蒿取代。本研究从叶片结构与功能两方面解释了上述现象，主要依据是(l)籽蒿比油蒿往往有更大的蒸腾速率：(2)籽蒿叶片近轴面1/3以下处有极为密集的气孔分布，而在油蒿却未发现;(3)籽蒿具有极其高的零膨压时的渗透势值(ψлp)。 ● 关于蒙古岩黄芪(Hedysarum mongolicum):该灌木具有独特的 干旱适应方式（如，幼茎 可行光合作用，及叶片富含粘液细胞），但本研究提示，该灌木的抗旱性是较弱的（相比与其它同生境下的灌木而言）。主要依据是：(1)很高的零膨压时的渗透势值;(2)海绵与栅栏组织均有较充分的发育。 ● 关于沙柳(Salix psammophila):在沙基质中有广泛的适应性， 但其适应主要体现在形态上（根茎比）的可塑性，而在生理（尤其是蒸腾作用）方面的调整则不十分显著。生长于丘顶的沙柳具有极其发达的根系，这可减缓土壤水分不足对植物的不利影响;生长于丘间低地的沙柳具有好的水分供给，但在特定的微生境下，其叶片温度比生长лллл于丘顶的沙柳叶片高，尤其是在强的光照条件下，其叶片温度会大幅度升高。这有可能对植物形成不利的影响。

北京山区落叶阔叶林优势种水分生理生态研究

本文研究了北京山区落叶阀叶林优势种一辽东栎、大叶白蜡、北京丁香、核桃楸、山杏和荆条等乔灌木的稳定碳同位素比率，长期水分利用效率、植物蒸腾特性和土壤植物体的水分运动特点，并从植物解剖学的角度研究了这些植物叶片特点和其水分生理生态特性的关系。 对北京山区落叶阔叶林生态系统这几种乔、灌木植物叶片中的碳稳定性同位素比率(δ¹³C值)测定结果显示，这些植物叶片的δ¹³C值受多种因子的影响，具有较大的种间差异及时空异质性。主要表现在不同植物种叶片δ¹³C值不同，其排列顺序为山杏(- 24.75±0.85%。>大叶白蜡(- 25,94±1.52%。)=荆条(- 26.01±1.63%。)=辽东栎(一26.07±1.17%。)=北京丁香(-26.46±0.80c70。)>核桃楸(-28.11±1.52%。);生长初期叶片δ¹³C值较生长末期高，尤以核桃楸和辽东栎表现明显其生长初期和末期的叶片δ¹³C值皆相差达3‰;生境条件，特别是土壤水分含量和土层厚度，对植物叶片的813C值的高低有较大的影响，生长在于旱生境中的植物具有较高的δ¹³C值。另外，即使是同一株植物，叶片δ¹³C值也因其在冠层中所处的位置不同而异，冠层项部叶片的δ¹³C值高于林冠内部的叶片。北京山区落叶阔叶林优势种的长期水分利用效率与种的特点有关，山杏最高(4.950±0．l71mmolC0_2•mol-1H_2O)，核桃楸最低(3.760±0.203mmolC0_2•mol-1H_2O)，大叶白蜡、荆条、辽东栎和北京丁香居中(4.346- 4.530 mmolCO_2•mol-1H_2O)，大部分植物长期水分利用效率在春季（5月）较高，秋季较低，荆条由于物候期的特殊性在其生长季初期较低，而后逐渐增高。核桃楸在不存在水分亏缺情况下，树干液流速率受微气候因子的影响，液流速率的最大值达1600g•hour 左右。树干液流速率的日进程和大气相对湿度、温度的日进程具有相当好的生态学同步性。通过对核桃楸夜晚树干液流的分析可以得出其有根压存在的结论。 植物叶片和枝条中自由水和束缚水含量主要决定于植物种的特性，枝条的年龄、生境特点，特别是土壤水分特点。在落叶阔叶林I(样地2)中植物叶片自由水含量的排列顺序是：北京丁香>核桃楸>大叶白蜡>辽东栎;而杂灌丛（样地1）中植物叶片自由水含量的排列顺序是：核桃楸>大叶白蜡>山杏>荆条>北京丁香>辽东栎，可见群落类型对植物自由水含量影响是很大的，植物束缚水含量与其自由水含量的格局完全相反，荆条、山杏等植物含量高，核桃揪含量低。枝条水分含量有与叶片水分含量相类似的特点。 北京山区落叶阔叶林优势种的水分生理生态学特性和其叶片的特点有很大的关系，首先是植物叶片的特点总是和其种的特性相联系，主要表现在叶的类型、叶片上毛、气孔密度、着生方式等，如荆条叶片上下表面都密被披针形毛，气孔小，核桃楸气孔较大且凸出，大叶白蜡叶片上的气孔凹陷，辽东栎的气孔呈椭圆状，保卫细胞上有许多白色蜡质结晶。有一些种有环状的气孔外缘。生境的变化对叶片的形态特征有影响，在全光照条件下叶片小而犀，而在庇荫条件下叶片大而薄，在扫描电镜下可见全光照条件下北京丁香叶片基本无毛，庇荫条件下则有短微毛，全光条件下荆条叶片上毛有小乳头状凸起，庇荫条件下没有。本文所研究的植物种气孔都着生在叶片的下表面，气孔密度的大小排列顺序是：辽东栎>山杏>北京丁香>核桃楸>大叶白蜡。经方差分析显示种闷气孔密度存在极显著性差异。对所研究植物的气孔导度和环境因子、叶片解剖特点进行线性回归分析，得到了总体的和各个种的回归模型，结果表明光照强度、气孔密度等对气孔导度影响显著，但因种的不同相互之间存在差别。 植物的蒸腾速率受多因子的影响，主要有种的特点、微气候因子（光照强度、大气相对湿度、叶面温度、叶室温度等）和土壤水分特点。植物的蒸腾速率日进程和微气候因子日进程有相当好的生态学同步性。对辽东栎的蒸腾速率和光照强度的研究发现二者有很好的线性关系。这些植物蒸腾速率都表现出一定规律的日进程和季节进程，大多数植物蒸腾速率在一天中有数次波动，最高峰一般出现在中午12时之前;在整个生长季中，6月底至8月初的蒸腾速率高于其他月份。

鄂尔多斯高原气候变化及典型植物与环境的相互作用

鄂尔多斯高原是一个多层次、复杂的生态地理过渡带，具有复杂多样的环境条件和生态特点。因而，研究该地区植被与环境复杂多变的相互关系有助于我们认识鄂尔多斯高原生态系统的脆弱性和植被对于维持该区生态系统结构和功能过程的重要性。 降水、温度及其组合特点决定了鄂尔多斯高原特殊的生态环境格局，分析其演变趋势有助于理解鄂尔多斯高原生态环境的演变过程。从旬、月、生长季和非生长季及年四个不同的时间分辨率对鄂尔多斯高原八个气象台站近30年的气象资料进行分析。结果表明30年来年平均气温、2、9、12月均温明显增高;年降水未发生显著变化，降水分配模式变化明显。采用与植物生长密切相关的气候因子对整个鄂尔多斯高原的气候特征进行综合分析，将鄂尔多斯高原划分为三个综合气候类型，即：半湿润、低蒸发型，半干旱、半湿润、中等蒸发型和偏干旱、高蒸发型。根据不同的气候类型，确定适宜恢复的植被类型，对目前该区域进行的生态恢复工作具有重要指导意义。 在鄂尔多斯高原从东向西的降水梯度上，选取三个实验点测定柠条的光合、蒸腾和水分利用效率等主要生理生态指标，分析了同种植物对不同环境的反应。鄂托克旗柠条光合速率最高，东胜东部柠条次之，杭锦旗柠条光合速率最低而蒸腾速率最大，东胜东部柠条和鄂托克旗柠条的蒸腾速率相差不大。 植被能够降低其下垫面及其附近的地表温度，从而影响地表蒸发。以鄂尔多斯高原典型植物油蒿和柠条作为研究对象，采用先进的非接触红外测温法，并提出度量植株温度效应的影响指数，对鄂尔多斯高原两种典型植物植株附近地表温度进行了比较分析,结果表明，柠条对地表温度的影响较油蒿明显。

Kelvin-Helmholtz-like instabilities in turbulent flows over complex surfaces

Riblets are small surface protrusions aligned with the flow direction, which confer an anisotropic roughness to the surface [6]. We have recently reported that the transitional-roughness effect in riblets, which limits their performance, is due to a Kelvin–Helmholtz-like instability of the overlying mean flow [7]. According to our DNSs, the instability sets on as the Reynolds number based on the roughness size of the riblets increases, and coherent, elongated spanwise vortices begin to develop immediately above the riblet tips, causing the degradation of the drag-reduction effect. This is a very novel concept, since prior studies had proposed that the degradation was due to the interaction of riblets with the flow as independent units, either to the lodging of quasi-streamwise vortices in the surface grooves [2] or to the shedding of secondary streamwise vorticity at the riblet peaks [9]. We have proposed an approximate inviscid analysis for the instability, in which the presence of riblets is modelled through an average boundary condition for an overlying, spanwise-independent mean flow. This simplification lacks the accuracy of an exact analysis [4], but in turn applies to riblet surfaces in general. Our analysis succeeds in predicting the riblet size for the onset of the instability, while qualitatively reproducing the wavelengths and shapes of the spanwise structures observed in the DNSs. The analysis also connects the observations with the Kelvin–Helmholtz instability of mixing layers. The fundamental riblet length scale for the onset of the instability is a ‘penetration length,’ which reflects how easily the perturbation flow moves through the riblet grooves. This result is in excellent agreement with the available experimental evidence, and has enabled the identification of the key geometric parameters to delay the breakdown. Although the appearance of elongated spanwise vortices was unexpected in the case of riblets, similar phenomena had already been observed over other rough [3], porous [1] and permeable [11] surfaces, as well as over plant [5,14] and urban [12] canopies, both in the transitional and in the fully-rough regimes. However, the theoretical analyses that support the connection of these observations with the Kelvin–Helmholtz instability are somewhat scarce [7, 11, 13]. It has been recently proposed that Kelvin–Helmholtz-like instabilities are a dominant feature common to “obstructed” shear flows [8]. It is interesting that the instability does not require an inflection point to develop, as is often claimed in the literature. The Kelvin-Helmholtz rollers are rather triggered by the apparent wall-normal-transpiration ability of the flow at the plane immediately above the obstructing elements [7,11]. Although both conditions are generally complementary, if wall-normal transpiration is not present the spanwise vortices may not develop, even if an inflection point exists within the roughness [10]. REFERENCES [1] Breugem, W. P., Boersma, B. J. & Uittenbogaard, R. E. 2006 J. Fluid Mech. 562, 35–72. [2] Choi, H., Moin, P. & Kim, J. 1993 J. Fluid Mech. 255, 503–539. [3] Coceal, O., Dobre, A., Thomas, T. G. & Belcher, S. E. 2007 J. Fluid Mech. 589, 375–409. [4] Ehrenstein, U. 2009 Phys. Fluids 8, 3194–3196. [5] Finnigan, J. 2000 Ann. Rev. Fluid Mech. 32, 519–571. [6] Garcia-Mayoral, R. & Jimenez, J. 2011 Phil. Trans. R. Soc. A 369, 1412–1427. [7] Garcia-Mayoral, R. & Jimenez, J. 2011 J. Fluid Mech. doi: 10.1017/jfm.2011.114. [8] Ghisalberti, M. 2009 J. Fluid Mech. 641, 51–61. [9] Goldstein, D. B. & Tuan, T. C. 1998 J. Fluid Mech. 363, 115–151. [10] Hahn, S., Je, J. & Choi, H. 2002 J. Fluid Mech. 450, 259–285. [11] Jimenez, J., Uhlman, M., Pinelli, A. & G., K. 2001 J. Fluid Mech. 442, 89–117. [12] Letzel, M. O., Krane, M. & Raasch, S. 2008 Atmos. Environ. 42, 8770–8784. [13] Py, C., de Langre, E. & Moulia, B. 2006 J. Fluid Mech. 568, 425–449. [14] Raupach, M. R., Finnigan, J. & Brunet, Y. 1996 Boundary-Layer Meteorol. 78, 351–382.

乔木蒸腾耗水量研究方法述评与展望

参阅了大量国内外有关乔木蒸腾研究方法文献,认为乔木蒸腾量研究方法主要有二大类,即组织器官测定、单木测定;分类对典型研究方法(快速称重法、气孔计法、整株容器称重法、同位素示踪法、热脉冲法、树干热平衡法、热扩散探针法)进行了述评,对比分析了各种方法间的优缺点及其适用范围;展望了乔木蒸腾耗水作用研究方法的应用前景,认为热技术法是未来几年内的主要测定方法。

黄土丘陵区不同立地达乌里胡枝子群落水分特征及生物量研究

对黄土高原丘陵沟壑区不同立地条件下的达乌里胡枝子群落水分特征及生物量进行了研究.结果表明:(1)不同立地下的达乌里胡枝子蒸腾日变化均呈单峰型,上午呈上升趋势,于13:00达到峰值,之后均呈不同程度下降趋势.(2)不同立地达乌里胡枝子群落0~200 cm土层平均含水量为阴坡12.34%,半阳坡11.29%,半阴坡11.15%,阳坡8.96%.不同立地达乌里胡枝子叶片相对含水量和饱和亏与各立地土壤含水量关系密切.(3)不同立地下各个时期的达乌里胡枝子群落的地上生物量表现为阴坡>半阴坡>半阳坡>阳坡,地下生物量则表现为阳坡(447.39 g/m2)>半阳坡(409.12 g/m2)>半阴坡(344.92 g/m2)>阴坡(217.01 g/m2).可见,达乌里胡枝子群落的水分生理特性及生物量的积累与立地条件密切相关.

称重式蒸渗仪系统改进及在农田蒸散研究中的应用

水分是制约黄土丘陵区农作物正常生长和农业生产的关键因子。该区年平均降水量少且季节多变,研究农田土壤水分平衡对该区旱地农业生产具有重要意义。土壤蒸渗仪(Lysimeter)可测量总蒸散量、渗漏量等有关水量平衡的各个分量,具有其它装置和方法不可比拟的优越性。它为田间蒸散和降水入渗实验研究提供了一种较先进的量测方法和技术手段。它对推动我国实验水文学的发展具有重要作用,并为相关领域的科学研究提供了一种较先进的技术设备和实验环境。中国科学院安塞试验站对原建造的用于测定农田蒸腾蒸发转化的称重式蒸渗仪在2005年对称重感应系统、电源进行改造,主要对主机、采集软件进行了重新更新,使其可直接在Windows界面下工作,数据采集更加方便,将测量出来的模拟量信号转换为数字信号,经处理显示并记录在数据采集器内。改进后蒸渗仪主要有以下特点:(1)土柱重19~26t,蒸渗仪精度为152 g(0.05 mm),可测量蒸腾蒸发量和地下水对土壤水的补给量与入渗量;(2)蒸渗仪面积3 m2(1.5 m×2 m),深度3 m,可充分允许农作物根系发育与吸水,土壤水和地下水转化,地下水位变化等过程进行,蒸渗仪的供排水系统能够在蒸渗仪内模拟实际地下水...