Diurnal Course Research Articles

Diurnal dynamics of oxygen and carbon dioxide concentrations in shoots and rhizomes of a perennial in a constructed wetland indicate down-regulation of below ground oxygen consumption.

Wetland plants actively provide oxygen for aerobic processes in submerged tissues and the rhizosphere. The novel concomitant assessment of diurnal dynamics of oxygen and carbon dioxide concentrations under field conditions tests the whole-system interactions in plant-internal gas exchange and regulation. Oxygen concentrations ([O2]) were monitored in-situ in central culm and rhizome pith cavities of common reed (Phragmites australis) using optical oxygen sensors. The corresponding carbon dioxide concentrations ([CO2]) were assessed via gas samples from the culms. Highly dynamic diurnal courses of [O2] were recorded, which started at 6.5-13 % in the morning, increased rapidly up to 22 % during midday and declined exponentially during the night. Internal [CO2] were high in the morning (1.55-17.5 %) and decreased (0.04-0.94 %) during the rapid increase of [O2] in the culms. The observed negative correlations between [O2] and [CO2] particularly describe the below ground relationship between plant-mediated oxygen supply and oxygen use by respiration and biogeochemical processes in the rhizosphere. Furthermore, the nocturnal declining slopes of [O2] in culms and rhizomes indicated a down-regulation of the demand for oxygen in the complete below ground plant-associated system. These findings emphasize the need for measurements of plant-internal gas exchange processes under field conditions because it considers the complex interactions in the oxic-anoxic interface.

Diurnal to annual changes in latent, sensible heat, and CO2 fluxes over a Laurentian Great Lake: A case study in Western Lake Erie

AbstractTo understand the carbon and energy exchange between the lake surface and the atmosphere, direct measurements of latent, sensible heat, and CO2 fluxes were taken using the eddy covariance (EC) technique in Western Lake Erie during October 2011 to September 2013. We found that the latent heat flux (LE) had a marked one‐peak seasonal change in both years that differed from the diurnal course and lacked a sinusoidal dynamic common in terrestrial ecosystems. Daily mean LE was 4.8 ± 0.1 and 4.3 ± 0.2 MJ m−2 d−1 in Year 1 and Year 2, respectively. The sensible heat flux (H) remained much lower than the LE, with a daily mean of 0.9 ± 0.1 and 1.1 ± 0.1 MJ m−2 d−1 in Year 1 and Year 2, respectively. As a result, the Bowen ratio was <1 during most of the 2 year period, with the lowest summer value at 0.14. The vapor pressure deficit explained 35% of the variation in half hourly LE, while the temperature difference between the water surface and air explained 65% of the variation in half hourly H. Western Lake Erie acted as a small carbon sink holding −19.0 ± 5.4 and −40.2 ± 13.3 g C m−2 in the first and second summers (May–September) but as an annual source of 77.7 ± 18.6 and 49.5 ± 17.9 g C m−2 yr−1 in Year 1 and Year 2, respectively. The CO2 flux ( ) rate varied from −0.45 g C m−2 d−1 to 0.98 g C m−2 d−1. Similar to LE, had noticeable diurnal changes during the months that had high chlorophyll a months but not during other months. A significantly negative correlation (P < 0.05) was found between and chlorophyll a on monthly fluxes. Three gap‐filling methods, including marginal distribution sampling, mean diurnal variation, and monthly mean, were quantitatively assessed, yielding an uncertainty of 4%, 6%, and 10% in LE, H, and , respectively.

Validation of modeled daily erythemal exposure along tropical and subtropical shipping routes by ship‐based and satellite‐based measurements

AbstractThe Personal ERythemal EXposure (PEREX) model for seafarers working on decks of vessels has been developed to be used for retrospective estimates of personal occupational erythemal exposure in dependence of work profile, time period, and sea route. Extremely high UV index values up to 22 and daily erythemal exposure up to 89 standard erythemal dose have been derived from ship‐based measurements in tropical oceans. Worldwide climatological maps of daily solar erythemal exposure derived from 10 year (2004–2013) hourly grid point radiative transfer model calculations for both cloudless sky and cloudy sky serve as the database of PEREX. The PEREX database is compared with ship‐based measurements taken along four routes of merchant vessels, continuous UV radiation measurements taken on the research vessel Meteor on its mainly tropical and subtropical routes for 2 years, daily cloudless‐sky erythemal exposure derived from 10 min LibRadtran radiative transfer model calculations, and 2 years of satellite‐based erythemal exposure data of the Ozone Monitoring Instrument on the Aura satellite along the ship routes. Systematic differences between PEREX model data, ship‐based data, and satellite‐based daily erythemal exposure for all‐sky conditions are only 1 to 3%, while short‐term variations of cloudiness result in standard deviations of differences around 30%. Measured ratios between cloudless‐sky erythemal radiation at vertical to horizontal incidence decrease with decreasing solar zenith angle, while clouds flatten their diurnal course.

Stable isotope variations in precipitation: simulations and comparison with observations (Yunnan Plateau, High Asia)

Stable isotopes in precipitation, both liquid (rain) and solid (snow), can be suitable tracers for hydrological cycles because their concentrations reflect the cumulative record of physical phase changes. Distribution of stable isotopes in precipitation over High-Asian monsoon regions, including Yunnan Plateau is investigated. It has two noticeable features: firstly, the stable isotopes in precipitation distinctly decrease; and secondly, the stable isotopes in precipitation demonstrate smaller concentrations during rainy seasons and higher values during dry seasons. These features were found by the MUGCM simulation developed in the Melbourne Univertisty. Quantitative effect of the stable isotopes in precipitation takes place at different time scales, i.e. in diurnal, monthly or annual variations. Relative to observations, the simulated δ¹⁸O in precipitation shows stronger dependence on precipitation. In the diurnal course, the simulated regression equations of δ¹⁸O in precipitation versus precipitation amount are in good agreement with the observed values at Tengchong and Simao, except that the simulated δ¹⁸O/P curve slope is slightly smaller than the observed one at Mingzi. In the monthly and annual courses both, the simulated and observed δ¹⁸O/P slopes are smaller than it is in the diurnal course. For individual station, the local meteoric water line (LMWL) is simulated well at Mengzi and Tengchong. However, the simulated result does not reproduce truly the observed relationship between δD and δ¹⁸O in precipitation at Simao and Kunming where the LMWL inclination is larger 8.0, and a shift along the y-axis higher 10.0. In addition, all simulated LMWL slopes are higher the observed ones at four stations, suggesting that the GCM can overestimate the decreasing of Hydrogen Deuterium Oxide and, thus, underestimate the second-order parameter, i.e. the deuterium excess, in a particular region Yunnan.

Diurnal and seasonal variations in photosynthetic characteristics of switchgrass in semiarid region on the Loess Plateau of China

In order to use rationally switchgrass (Panicum virgatum L.) introduced in a large scale in semiarid regions on the Loess Plateau of China, we investigated and compared soil water storage dynamics, diurnal and seasonal changes in leaf photosynthetic characteristics, and biomass production of switchgrass grown under three different row spacing (20, 40, and 60 cm). Results indicated that photosynthetic parameters showed a pronounced seasonality. Diurnal course of net photosynthetic rate (PN) was bimodal, showing obvious midday depression, which was mainly due to stomatal limitation in May and June, by nonstomatal limitation in August, and both stomatal and nonstomatal factors in September. Generally, PN, stomatal conductance, instantaneous water-use efficiency, light-saturated net photosynthetic rate, saturation irradiance, and compensation irradiance increased with increasing row spacing. Plant height, leaf width, and a relative growth rate of biomass accumulation were significantly higher at the row spacing of 60 cm, while 20 cm spacing showed significantly higher aboveground biomass production and the biomass water-use efficiency. All these confirmed that soil water is the key limiting factor influencing switchgrass photosynthesis, and suggested that the wide row plantation (i.e., 60 cm) was more beneficial to switchgrass growth, while narrow spacing was in favor of improving switchgrass productivity and water-use efficiency.

Sensitivity of thermal imaging and infrared thermometry to detect water status changes in Euonymus japonica plants irrigated with saline reclaimed water

The potential of thermal imaging and infrared thermometry for monitoring the effects of salinity on Euonymus japonica (euonymus) plants was assessed using the following irrigation treatments: Control (electrical conductivity (EC) −1 ) and reclaimed water, RW (EC ≈ 4 dS m −1 ). The experiment was conducted for more than eight months in a plastic greenhouse. The diurnal course of canopy temperature ( T c ) and the difference between canopy and air temperature ( T c − T a ) for both sunlit and shaded sides was influenced by high concentration of salts in the reclaimed water. The negative relationship between T c and stomatal conductance ( g s ) and between T c − T a and g s in April was significant during most of the day, but specifically at midday. Regarding the effect of canopy side, better regression coefficients were obtained between T c and g s , and between T c − T a and g s on the sunlit side of the canopy than on the shaded side. However, except for the crop water stress index on the sunlit side of the canopy, few differences during the day were reported for thermal indices. From April onwards, canopy temperatures were higher in RW plants than in the control, indicating the dependence of canopy temperature on salinity. Comparing the sensitivity of discrete (stem water potential and g s ) and continuous ( T c and thermal-derived parameters measured by infrared thermometers) indicators of saline stress, it was shown that T c and T c − T a were the most suitable plant-based indicators for precise irrigation scheduling.

Wordsworth Learns to Write Elegy

Previous articleNext article No AccessWordsworth Learns to Write ElegyPamela WoofPamela Woof Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Wordsworth Circle Volume 46, Number 2Spring 2015 Article DOIhttps://doi.org/10.1086/TWC24888058 Views: 27Total views on this site © 2015 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Turbulent Heat Fluxes above a Suburban Reservoir: A Case Study from Germany

Abstract With the objective of quantifying turbulent sensible QH and latent QE heat fluxes above a suburban reservoir, a micrometeorological turbulence measurement campaign using the eddy covariance technique was carried out between June and November 2012 on the Baldeneysee, an artificial lake (2.64 km2 area with up to 4-m depth) located in Germany. The study was conducted at this site because there is little information on this type of lake and the findings are important for the local water management system. Sensible heat fluxes show a mean diurnal course with maximum positive values during the early morning hours (maximum = +31.3 W m−2) and negative values in the afternoon (minimum = −12.3 W m−2). During daytime, average QH/Q* ratios (where Q* is the radiation balance) are, in general, smaller than 0.20. Sensible heat fluxes are especially affected by the product of wind speed and water–air temperature difference, as well as the magnitude of global radiation. In contrast, mean hourly values of QE are, on average, positive over the whole day, with an absolute spread between +175.1 and −0.8 W m−2. During daytime in summer, 74% of the radiation balance is transferred via QE. The measurement values show that during two summer days, 3.72 and 2.84 mm day−1 of water could be evaporated, whereas during two measurement days in autumn, evaporation rates of only 1.36 and 0.94 mm day−1 were registered. The magnitude of QE is mainly affected by four main parameters: the product of wind speed and vapor pressure deficit, followed by the magnitude of global radiation and water temperature.

On the controlling factors for the variability of carbon dioxide flux in a heterogeneous urban environment

ABSTRACTLocal heterogeneity of CO2 sources and sinks is a key factor for the variability of carbon dioxide flux (FC) in urban areas. Information on the urban structure around a site, especially the related emission characteristics, is thus of great importance to the understanding of observed FC. Strong spatially confined sources like major roads inhibit a direct correlation of FC to area‐averaged features of the urban structure and may lead to a heavily biased signal.Four years of FC measured at Basel Aeschenplatz, Switzerland, are analysed with respect to the controlling factors and the cause for variability on different time scales. The source area is segregated into equal sectors to address heterogeneous emission patterns. Residential areas to the east are bordered by business areas and major roads to the west, which leads to a fundamental dependence of FC on wind direction. Besides, its diurnal course is explainable with traffic emissions while its annual course follows heating‐related combustion emissions. Vegetation fraction is rather considered to be an indicator for urban land use types (residential/business) and the attributable emission characteristics than to be a measure for biological sink effects. Inter‐annual variability occurs as a result of anomalies in wind direction patterns or air temperature. Average yearly FC is 16.4 µmol m–2s–1 with slight variations (±0.55 µmol m–2s–1) over the 4 years. It likely originates from an average of 70% traffic and 30% heating‐related emissions with significant sectoral differences.As a continuous measure for the emissions of each sector, the expected CO2 flux (eFC) per sector is introduced, leading to an enhanced comparability. Relating sectoral eFC instead of FC to urban surface fractions of buildings and vegetation results in a better agreement (also with data from other studies).

新疆杨树干液流的径向变化及时滞特征

PDF HTML阅读 XML下载 导出引用 引用提醒 新疆杨树干液流的径向变化及时滞特征 DOI: 10.5846/stxb201401060046 作者: 作者单位: 中国林业科学研究院荒漠化研究所,中国林业科学研究院荒漠化研究所,中国林业科学研究院荒漠化研究所,甘肃省治沙研究所,中国林业科学研究院荒漠化研究所 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(31070628); 中央级公益性科研院所基本科研业务费专项资金项目(CAFYBB2012024) Radial pattern and time lag of sap flow in Populus alba var. pyramidalis Author: Affiliation: Institute of Desertification Studies, Chinese Academy of Forestry,,,, 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:利用热扩散技术, 对绿洲农田防护林新疆杨(Populus alba L.var. pyramidalis)大树边材5个深度处(1、2、3、5 cm 和8 cm)的液流速率(Js)开展了连续两年的监测, 结果表明:(1)以标准长度2 cm的探针测得的液流速率(Js-2)为参照, 形成层下1、3、5、8 cm处的液流速率(Js-1, Js-3, Js-5, Js-8)与Js-2间具有显著的相关性, 回归系数分别为0.24-0.27、1.18-1.61、0.81-1.64和0.38-0.75, 液流速率最大的位点在形成层下3-5 cm处, 液流速率最小的位点在最外侧(1 cm)或最内侧(8 cm)处, 径向差异明显。边材不同深处的液流传输具有较一致的日变化过程。(2)在同步观测的5项气象要素中, 大气水汽压亏缺(VPD)和太阳辐射(Ra)与Js的回归系数均较大, 是驱动液流进程的主导气象要素。大气蒸发潜力(ET0)集合了多种气象要素的信息, 具有与Ra一致的日变化进程(启动、峰值时刻相同), 可作为分析液流昼、夜过程的综合气象变量。(3)新疆杨边材中五个深度处Js的峰值时刻基本相同(Js-1的峰值较其它层次提前4-123 min), 均明显滞后于Ra(时滞)并提前于VPD, 在7月份的晴天, ET0、Js和VPD峰值出现的时刻分别大致在12:30、14:00和15:00。新疆杨时滞的大小存在有规律的季节变化, 从6到10月份, Js与ET0峰值的时滞(ΔJ-E)逐渐增加, 变化在70-110 min(2011)、70-128 min(2012)之间, 但VPD与Js峰值的时滞(ΔJ-V)逐渐降低, 变化在73-20 min(2011)、63-8 min(2012)之间, 这表明在生长季的早期, 热量因子(Ra)对新疆杨液流变化的驱动较强, 而在生长季的末期, 大气水汽因子VPD的驱动效应更突出。 Abstract:Scientists have widely used sap flow measurements to estimate tree transpiration and to understand the physiological and environmental factors affecting the sap flow. However, the assumption of a uniform profile of sap flux may lead to a large bias when estimating whole-tree sap flow from measurements made with a single sensor in the outer part of the xylem sapwood. In this study, the sap flow velocities (Js) were measured at five depths (1 cm, 2 cm, 3 cm, 5 cm, and 8 cm) along a radial xylem transect of three larger trees of Populus alba L. var. pyramidalis Bunge, a popular tree species often planted in farmland shelterbelts of oasis in northern China. Measurements were made with five pairs of Granier thermal dissipation probes (TDP) for each tree over two consecutive growing seasons (in 2011 and 2012) to determine the radial sap flow pattern. The results showed that: (1) Js varies with depth in the descending order from 3 cm to 2 cm, 5 cm, 8 cm, and 1 cm. Js at depths of 1 cm (Js-1), 3 cm (Js-3), 5 cm (Js-5) and 8 cm (Js-8 ) were significantly and linearly correlated with that at 2 cm depth (Js-2), and their intercept coefficients were 0.24-0.27, 1.18-1.61, 0.81-1.64, and 0.38-0.75, respectively. The greatest Js appeared at depths of 3 to 5 cm under the cambium and the lowest appeared at depths of 1 cm or 8 cm; thus, the conventional 2-cm-long probe cannot reach the peak point of sap flow. Significant differences in Js were observed along the radial sapwood despite their similar diurnal course. (2) The atmospheric vapor pressure deficit (VPD) and solar radiation (Ra), two factors expressing the level of atmospheric vapor and heat, respectively, were the most important among the five meteorological factors controlling Js. The influence of Ra and VPD on Js in the outer and inner xylem during the growing season were similar for P. alba. However, accurately differentiating their respective contributions to sap flow proved to be difficult because of the interaction between them. The atmospheric potential evapotranspiration (ET0), which is a good indicator of the effects from meteorological variables, showed nearly similar diurnal pattern to Ra and was closely correlated with Js. (3) The diurnal course of Js for each depth displayed a near-normal curve with a peak at noon on typical sunny days. Js at depths of 2 cm to 8 cm peaked simultaneously. As an exception, the peak time of Js-1 appeared 4 min to 123 min ahead of the others. The peak times of all Js lagged behind Ra and were ahead of VPD. In July, P. alba exhibited vigorous physiological activities. The peak time of ET0, Js, and VPD on typical sunny days in July appeared at 12:30, 14:00 and 15:00, respectively. However, the time lag varied with season. The time lag between Js and ET0 (ΔJ-E) increased gradually from June to October with the amplitude of 70-110 min in 2011 and 70-128 min in 2012, indicating that solar radiation affected Js more strongly during the early growing season than later in the season. In contrast, the time lag between Js and VPD (ΔJ-V) decreased from June to October and varied in the range of 20-73 min in 2011 and 8-62 min in 2012, indicating that VPD affected Js more strongly in the late growing season than early in the season. 参考文献 相似文献 引证文献

Diurnal Course of the Main Heat Balance Components of a Marshy Meadow in the Lower Biebrza River Valley

Diurnal Course of the Main Heat Balance Components of a Marshy Meadow in the Lower Biebrza River Valley

Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf.

Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO₂ concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO₂ concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO₂ on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem-leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO₂ assimilation rate over the diurnal course of evaporative demand.

Spatial Differentiation Of Global Solar Radiation in Toruń And its Suburban Area (Central Poland) in 2012

Abstract : This article investigates the spatial distribution of global solar radiation (K↓) in Toruń and its suburbs, observed in 2012. Measurements were taken at 12 points (7 within the city and 5 in the suburban area) using CNR4 net radiometers and automatic weather stations (Vantage Pro+). At all locations, the diurnal and annual courses of K↓ were typically related to the Earth’s rotational movement and changes in the sun’s declination over the year, and disturbed by clouds and atmospheric phenomena that enhance the extinction of solar radiation. A substantial spatial diversity of K↓ was observed in Toruń and its suburbs. The annual sum of K↓ at several urban locations accounted for over 70% of the solar radiation in the open space outside the city. The amount of incoming solar radiation in the urban area was more restricted in winter (<50%) than in summer (approx. 70%). The diurnal courses of K↓ were heavily disturbed by local obstacles which cast shadows (causing a considerable decrease of K↓), but there were instances of increases in K↓ (122%) augmented by radiation reflected from roofs, walls and windows surrounding the measurement point. The spatial diversity of K↓ in the urban area is heterogeneous, due to local meteorological conditions (cloudiness, fog, smog and airborne dust) and the obscuring of the horizon.

Photosynthetic characterization of three dominant plant species in the saline–alkaline soil of the Yellow River Delta, China

The diurnal variations of photosynthesis of three dominant species, including Glycine soja, Phragmites australis, and Cynanchum chinensis, in the Yellow River Delta in China have been studied under the same natural conditions using a Li-6400 portable photosynthesis system. The results showed that the curves of diurnal variations of net photosynthetic rate (PN) of the three plants were different. The diurnal variation of PN on C. chinensis was a midday depression pattern and had two peaks. However, PN of G. soja and P. australis showed single-peak curves. The transpiration rate (E) of G. soja was significantly higher than that of P. australis and C. chinensis, both showed single-peak curves. In general, the diurnal course of stomatal conductance (gs) followed the same pattern of PN. A similar diurnal pattern of intercellular CO2 concentration (Ci), vapor pressure deficit (VPD), and water use efficiency (WUE) was observed among different species. VPD showed single-peak curves, while WUE was characterized by double-peak curves, which was contrary to Ci. Linear correlations among photosynthetic variables and key environmental factors indicate high positive correlations between PN and E, PN and photosynthetic active radiation, PN and leaf temperature (Tleaf), PN and VPD, and between PN and gs except C. chinensis. Negative correlations among PN and relative humidity, PN and Ci were found. The irradiance response curves derived from the leaves were substantially affected by different species. C. chinensis showed highest apparent quantum efficiency, followed by P. australis and G. soja, while apparent dark respiration (Rd), convexity (k), light saturation point, and maximum gross CO2 assimilation rate (Pmax) of G. soja were higher than those of P. australis and C. chinensis. The irradiance response curve of PN and WUE of different plant species followed the same order: G. soja>C. chinensis>P. australis. They were both higher than most of other species. It was concluded that plant species adapting to the saline–alkaline habitat showed higher photosynthesis. In addition, G. soja is also effective to improve saline–alkaline soil quality.

Diurnal Dynamics of Wheat Evapotranspiration Derived from Ground-Based Thermal Imagery

The latent heat flux, one of the key components of the surface energy balance, can be inferred from remotely sensed thermal infrared data. However, discrepancies between modeled and observed evapotranspiration are large. Thermal cameras might provide a suitable tool for model evaluation under variable atmospheric conditions. Here, we evaluate the results from the Penman-Monteith, surface energy balance and Bowen ratio approaches, which estimate the diurnal course of latent heat fluxes at a ripe winter wheat stand using measured and modeled temperatures. Under overcast conditions, the models perform similarly, and radiometric image temperatures are linearly correlated with the inverted aerodynamic temperature. During clear sky conditions, the temperature of the wheat ear layer could be used to predict daytime turbulent fluxes (root mean squared error and mean absolute error: 20–35 W∙m−2, r2: 0.76–0.88), whereas spatially-averaged temperatures caused underestimation of pre-noon and overestimation of afternoon fluxes. Errors are dependent on the models’ ability to simulate diurnal hysteresis effects and are largest during intermittent clouds, due to the discrepancy between the timing of image capture and the time needed for the leaf-air-temperature gradient to adapt to changes in solar radiation. During such periods, we suggest using modeled surface temperatures for temporal upscaling and the validation of image data.

The AT-hook motif-encoding gene METABOLIC NETWORK MODULATOR 1 underlies natural variation in Arabidopsis primary metabolism.

Regulation of primary metabolism is a central mechanism by which plants coordinate their various responses to biotic and abiotic challenge. To identify genes responsible for natural variation in primary metabolism, we focused on cloning a locus from Arabidopsis thaliana that influences the level of TCA cycle metabolites in planta. We found that the Met.V.67 locus was controlled by natural variation in METABOLIC NETWORK MODULATOR 1 (MNM1), which encoded an AT-hook motif-containing protein that was unique to the Brassicales lineage. MNM1 had wide ranging effects on plant metabolism and displayed a tissue expression pattern that was suggestive of a function in sink tissues. Natural variation within MNM1 had differential effects during a diurnal time course, and this temporal dependency was supported by analysis of T-DNA insertion and over-expression lines for MNM1. Thus, the cloning of a natural variation locus specifically associated with primary metabolism allowed us to identify MNM1 as a lineage-specific modulator of primary metabolism, suggesting that the regulation of primary metabolism can change during evolution.

Diurnal course analysis of the WRF-simulated and observation-based planetary boundary layer height

Abstract. Weather Research and Forecasting (WRF) single-column model simulations were performed in the late summer of 2012 in order to analyse the diurnal changes of the planetary boundary layer (PBL). Five PBL schemes were tested with the WRF. From the radiometer and wind-profiler measurements at one station, derived PBL heights were also compared to the simulations. The weather conditions during the measurement period proved to be dry; the soil moisture was below wilting point 85 percent of the time. Results show that (1) simulation-based PBL heights are overestimated by about 500–1000 m with respect to the observation-based PBL heights, and (2) PBL height deviations between different observation-based methods (around 700 m in the midday) are comparable with PBL height deviations between different model schemes used in the WRF single-column model. The causes of the deviations are also discussed. It is shown that in the estimation of the PBL height the relevance of the atmospheric profiles could be as important as the relevance of the estimation principles.

Analysis of photosynthetic characteristics and its influencing factors of medicinal plant Mirabilis himalaica

To study photosynthetic characteristics and its influencing factors in leaves of medicinal plant Mirabilis himalaica, and provide an evidence for guiding artificial planting and improving the quantity. The light-response and diurnal photosynthesis course of leaves at the booting stages of 1-3 year old M. himalaica were measured with LI-6400 system. The Results showed that the light response curves were fitted well by non rectangle hyperbola equation (R2 > or = 0.98). The values of the maximum photosynthetic rate (Pmax) and light use efficiency of three-year old M. himalaica leaves were higher than those of 1-2 year old individuals. The diurnal variation of net photosynthetic rate (Pn) and stomatal conductance (Gs) of 2-3 year old M. himalaica were typical double-peak curves determinately regulated by stomatal conductance. However, transpiration rate (Tr) of 1-3 year old plants leaves were single-peak curve, which was self-protection of harm reduction caused by the higher temperature at noontime. Correlation analysis showed that the changes between photosynthetic active radiation (PFD), air temperature (T ) and Pn, were significant positive related. Therefore, M. himalaica is a typical sun plant, which should be planted under the sufficient sunshine field and prolong the growing ages suitably in order to improve the yield.

A simple method to simulate diurnal courses of PAR absorbed by grassy canopy

The fraction of photosynthetically active radiation absorbed by vegetation (FAPAR) quantifies the efficiency of absorbing PAR by plants. Accurate estimation of diurnal variation of FAPAR however remains a challenge because of the dynamic changes of incident light conditions and its interaction with canopy structure. Based on a field experiment, we characterized the effects of solar zenith angle (SZA) and fraction of diffuse light (fdPAR) on diurnal FAPAR in an alpine wetland on the Tibetan plateau. We found an obvious nonlinear change pattern of FAPAR against SZA with a maximum value of FAPAR at the SZA of about 30°, and opposite responses of FAPAR to fdPAR outside of a SZA range between 21° and 30°. A curve fitting (CF) method was proposed to estimate diurnal FAPAR in a rapid and accurate way. The CF method accounting for the interactions of SZA and fdPAR on FAPAR can successfully describe the diurnal dynamics of FAPAR under clear and cloudy sky conditions. The estimation deviation of daily FAPAR was only −0.28% for a period of about eight days with various sky conditions. The new method requires only very simple field measurements, but has higher accuracy than the widely-used light penetration model, which is expected to be widely used in grassy vegetations.

Carbon dioxide fluxes over a temperate meadow in eastern Inner Mongolia, China

Understanding the carbon dynamics in grassland is essential to precisely estimate global atmospheric carbon budget in response to climatic change. Eddy flux measurements were carried out during 2011 and 2012 to characterize seasonal and annual variability of carbon exchanges above a temperate meadow in eastern Inner Mongolia, China. The CO2 flux showed obvious diurnal variations and the monthly mean amplitudes of diurnal course followed June/July > August > May > September. The daily maximum NEE reached up to −8.0 and −7.7 g C m−2 for 2011 and 2012, respectively. CO2 uptake was mainly from May to August, with seasonal peaks of −16.0 g C m−2 day−1 in both two years. Gross primary production (GPP) and ecosystem respiration (Re) were −1,084.5, 987.1 g C m−2 year−1 in 2011, and −1,123.3, 1,040.2 g C m−2 year−1 in 2012, respectively. The meadow acted as a stable carbon sink, with integrated net ecosystem exchange (NEE) of −97.4 and −83.1 g C m−2 year−1 for 2011 and 2012, respectively. Compared with 2011, the ecosystem assimilated more carbon and meanwhile respired even more, leading to a less carbon sequestration in 2012. PAR and leaf area index (LAI) dominated the seasonal variations in NEE, with PAR explaining 61–69 % of the variance in NEE as LAI maintaining the plateau during June to July. Harvest significantly decreased ecosystem carbon uptake. The interannual variability in GPP and Re resulted primarily from the variations in temperature and its effect on biomass growth.