Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

A large scale mismatch exists between our understanding and quantification of ecosystem atmosphere exchange of carbon dioxide at local scale and continental scales. This paper will focus on the carbon exchange on the regional scale to address the following 5 question: What are the main controlling factors determining atmospheric carbon dioxide content at a regional scale? We use the Regional Atmospheric Modelling System (RAMS), coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C), and including also sub models for urban and marine fluxes, which in principle include the main controlling mechanisms and capture the relevant dynamics 10 of the system. To validate the model, observations are used which were taken during an intensive observational campaign in the central Netherlands in summer 2002. These included flux-site observations, vertical profiles at tall towers and spatial fluxes of various variables taken by aircraft. The coupled regional model (RAMS-SWAPS-C) generally does a good job in sim15 ulating results close to reality. The validation of the model demonstrates that surface fluxes of heat, water and CO2 are reasonably well simulated. The comparison against aircraft data shows that the regional meteorology is captured by the model. Comparing spatially explicit simulated and observed fluxes we conclude that in general simulated latent heat fluxes are underestimated by the model to the observations which exhibit 20 large standard deviation for all flights. Sensitivity experiments demonstrated the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same test also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations

Isoprenoid emission in trees of Quercus pubescens and Quercus ilex with lifetime exposure to naturally high CO2 environment

The long-term effect of elevated atmospheric CO2 on isoprenoid emissions from adult trees of two Mediterranean oak species (the monoterpene-emitting Quercus ilex L. and the isoprene-emitting Quercus pubescens Willd.) native to a high-CO2 environment was investigated. During two consecutive years, isoprenoid emission was monitored both at branch level, measuring the actual emissions under natural conditions, and at leaf level, measuring the basal emissions under the standard conditions of 30 degreesC and at light intensity of 1000 mumol m(-2) s(-1). Long-term exposure to high atmospheric levels of CO2 did not significantly affect the actual isoprenoid emissions. However, when leaves of plants grown in the control site were exposed for a short period to an elevated CO2 level by rapidly switching the CO2 concentration in the gas-exchange cuvette, both isoprene and monoterpene basal emissions were clearly inhibited. These results generally confirm the inhibitory effect of elevated CO2 on isoprenoid emission. The absence of a CO2 effect on actual emissions might indicate higher leaf temperature at elevated CO2, or an interaction with multiple stresses some of which (e.g. recurrent droughts) may compensate for the CO2 effect in Mediterranean ecosystems. Under elevated CO2, isoprene emission by Q. pubescens was also uncoupled from the previous day\u27s air temperature. In addition, pronounced daily and seasonal variations of basal emission were observed under elevated CO2 underlining that correction factors may be necessary to improve the realistic estimation of isoprene emissions with empirical algorithms in the future. A positive linear correlation of isoprenoid emission with the photosynthetic electron transport and in particular with its calculated fraction used for isoprenoid synthesis was found. The slope of this relationship was different for isoprene and monoterpenes, but did not change when plants were grown in either ambient or elevated CO2. This suggests that physiological algorithms may usefully predict isoprenoid emission also under rising CO2 levels

Sensible and latent heat flux from radiometric surface temperatures at the regional scale: methodology and validation

The CarboEurope Regional Experiment Strategy (CERES) was designed to develop and test a range of methodologies to assess regional surface energy and mass exchange of a large study area in the south-western part of France. This paper describes a methodology to estimate sensible and latent heat fluxes on the basis of net radiation, surface radiometric temperature measurements and information obtained from available products derived from the Meteosat Second Generation (MSG) geostationary meteorological satellite, weather stations and ground-based eddy covariance towers. It is based on a simplified bulk formulation of sensible heat flux that considers the degree of coupling between the vegetation and the atmosphere and estimates latent heat as the residual term of net radiation. Estimates of regional energy fluxes obtained in this way are validated at the regional scale by means of a comparison with direct flux measurements made by airborne eddy-covariance. The results show an overall good matching between airborne fluxes and estimates of sensible and latent heat flux obtained from radiometric surface temperatures that holds for different weather conditions and different land use types. The overall applicability of the proposed methodology to regional studies is discusse

In-vitro application of pentoxifylline preserved ultrastructure of spermatozoa after vitrification in asthenozoospermic patients

Abstract PURPOSE: To evaluate the effect of in vitro application of pentoxifylline (PX) on sperm parameters and ultrastructure after vitrification in asthenozoospermic patients. MATERIALS AND METHODS: A total of 30 asthenozoospermic semen samples (aged 25-45 years) were divided into four groups before vitrification, after vitrification, control (without PX) and experimental (with PX). In experimental group, each sample was exposed for 30 min to 3.6mmol/l PX and the control group without any treatment apposing in 370C for 30 min. After incubation, the samples were washed and analyzed again. Vitrification was done according to straw method. Eosin-nigrosin and Papanicolaou staining were applied for assessment of sperm viability and morphology, respectively. The samples without PX and post treatment with PX were assessed by transmission electron microscopy (TEM). RESULTS: A significant decrease in sperm motility (P ≤ .001), morphology (11.47 ± 2.9 versus 6.73 ± 2.01) and viability (73.37 ± 6.26 versus 54.67 ± 6.73) was observed post vitrification, but sperm motility (19.85 ± 4.75 versus 32.07 ± 5.58, P ≤ .001) was increased significantly following application of PX. This drug had no significant (P >.05) detrimental neither negative effect on ultrastructure acrosome, plasma membrane and coiled tail statues of spermatozoa. CONCLUSION: Vitrification had detrimental effects on sperm parameters, but PX reversed detrimental effects on sperm motility. However, PX had no alteration on ultrastructure morphology of human spermatozoa after vitrification

Cyclic response of masonry piers retrofitted with timber frames and boards

The quasi-static in-plane cyclic response of two single-leaf calcium silicate unreinforced masonry piers was investigated to show the effectiveness of an innovative timber retrofit solution. The aim of the intervention is to increase the pier in-plane and out-of-plane strength and displacement capacity, thus reducing the seismic vulnerability of this typology of unreinforced masonry construction with a light, cost-effective, sustainable and reversible approach. The retrofit technique consists of a timber frame mechanically connected by means of steel fasteners to the masonry pier and building floors. Oriented strand timber boards are then nailed to the frame. In-plane quasi-static shear-compression cyclic tests were performed on two single-leaf calcium silicate brick piers with identical geometry and masonry mechanical properties: one was tested unstrengthened while the other was tested in the retrofitted configuration. The experimental results showed evident improvements in the lateral force-displacement response of the retrofitted specimen. More specifically, compared with the bare masonry pier, the retrofitted pier exhibited slightly higher stiffness, larger strength and significantly greater displacement capacity

Simulation of wheat ontogenesis

The main purpose of this study is to understand wheat ontogenesis and to formulate a simulation model of the development of wheat for application under field conditions. The basic idea that is behind this work is that plant development can be accurately simulated on the basis of leaf appearance provided that the final number of leaves is known. Apex and leaf development are in fact coordinated and in plants with terminal flowers, flowering occur when all the leaves are appeared on the stem. Wheat ontogenesis, apical and phenological development of wheat are described at first in the introductory chapter. A brief review of current knowledge about factors affecting wheat development and some information about existing ontogenetic models are also given.Subsequently, data of some experiments in the literature are compared and statistically analysed to confirm the assumption of independence of wheat leaf initiation from daylength, and to evaluate the effect of temperature. Independence for any daylength treatement is demonstrated by the strict proportionality between the total number of initiated leaf primordia and the time to double ridges. The temperature response of leaf initiation rate is evaluated as the slope of a regression line between these two variables for different thermal treatments. On such a basis a linear model is constructed where daily leaf primordium initiation rates are calculated as a function of temperature. Data from a specific field experiment are then used to test the model. In the experiment, two varieties (Maris Huntsman and Creso) and two sowing dates (late November and early February) are compared. Predicted and observed dates of double ridge appearance and the predicted number of initiated primordia match rather accurately for both sowing dates and varieties, confirming the previous hypothesis. It is concluded that vmost of the genotypic variabIlity in wheat ontogenesis is accounted for by the effect of photoperiod on earliness of floral induction and, therefore, on the final main stem leaf number.However, rate of leaf appearance differs among wheat crops sown in the field at different dates. This can be interpreted either as a direct effect of the date of sowing on the rate of leaf appearance or as an indirect effect of an ontogenetic decline in the rate of leaf appearance as the plant ages. This decline is attributed to the increasing distance that has to be traversed the youngest leaf in the apparent stem that is formed by the leaf sheets of the older leaves. Analysis of data from both laboratory and field experiments leads to the conclusion that the second hypothesis is more likely. A simulation model of leaf appearance is formulated on the basis of this hypothesis, and tested using experimental results from the literature and 2 original experiments carried out in Italy. A good agreement between experimental data and simulation results is found. The model simplifies the problem of simulation of leaf appearance considerably compared with existing models that are based on a spurious relation between the rate of change in daylength at crop emergence and the rate of leaf appearance, which does not have a physiological base.The problem of the prediction of the final number of leaves is then approached. The role of photoperiod in the regulation of wheat development and on final main stem leaf number is analysed by means of literature data from a number of laboratory experiments. A procedure is developed to calculate the final number and the date of heading of plants that do not require vernalisation. Subsequently, differences between calculations and field observation are ascribed to an effect of vernalisation. This allows the formulation of a model to predict the final number of leaves and date of heading of any given wheat variety. The model involves the following assumptions: (1) wheat varieties have different sensitivities to the daylength; (2) wheat varieties that require vernalisation are vernalised at a very early stage of growth if sown at the beginning of the coldest period of the year; (3) wheat varieties that are vernalised at a very early stage of growth immediately respond to external photoperiodic conditions; (4) wheat crops sown within a range of sowing dates tend to synchronize time of flowering. It is concluded that if the final main stem leaf number of a crop sown at a given date is known, the date of heading and the corresponding final leaf number of main stem leaves of every other sowing can be found. The model is validated using field data from 58 experimental trials performed in the USA and Europe.In the last part of the work, the effect of nitrogen fertilization, water shortage and of the genotype on both the rate of leaf appearance and the final leaf number are considered. Results of field experiments conducted in USA and of original experiments performed in Italy are used for such a purpose. Data analysis shows that leaf appearance, final leaf number and phasic development of wheat are independent of nitrogen fertilization and water shortage and that genotypic effect is restricted to the control of the final number of leaves but not of the rate of leaf appearance.Finally, the formulated models are extensively validated on basis of data recorded in field experiments and it is concluded that these appear to be well suited for monitoring wheat ontogenesis under field conditions. The models can be used in agronomy, for analyses of the influence of weather on the development of wheat and of the adaptation of varieties to different environments and for studying the impact of climatic changes on agriculture