Simulation of the effect of pruning and topping on cotton growth using COTTON2K model

COTTON2K, like most other cotton production models, does not always adequately represent local growth conditions owing to the fact that it fails to take into account some indigenous cultivation practices. For instance, pruning and topping, a common practice for cotton cultivation in China is not included in the model simulation of COTTON2K. The objective of this research therefore was to: (1) modify COTTON2K source code and slot pruning and topping simulation switch on to the model, and (2) calibrate and validate the modified COTTON2K model with field data from pruning and topping cultivation practice. First, field collected data in 2003 and 2004 were compared between the treatments, with and without pruning and topping, and the COTTON2K source code updated with the ‘pruning and topping’ switch. This was followed by the calibration and validation of the updated model with field data and simulation of the effect of pruning and topping on cotton performance. It was noted from field observations that pruning and topping reduced total fruit sites, but at the same time, increased retained boll number, possibly due to significant reductions in abscised fruit sites. Though total dry matter production dropped, more dry matter allocation to reproductive organs, however, enhanced higher cotton lint yield in the pruning and topping treatment. Results of the modified model simulation showed that growth in the number of main-stem node ceased after topping. Furthermore, there was more biomass allocation to reproductive organs, such as green and open bolls under pruning and topping. Coefficient of determination above 0.8 for most of the growth factors was obtained in the calibration and validation processes under pruning and topping, a strong indication of the level of success of the model modification.     

Evaluating an environmental indicator: Case study of MERLIN, a method for assessing the risk of nitrate leaching

The need to achieve acceptable levels of nitrate in drinking water has led to the development of simulation models and indicators for assessing the environmental performance of agricultural practices. These indicators are necessarily based on simplifications in order to meet the practical constraints of feasibility, but they should nevertheless meet scientific standards, especially as regards their validation. The overall objective of this paper is to evaluate the MERLIN indicator and sub-indicators, an assessment method developed by French agricultural advisors. This tool estimates and classes the risks of water pollution by nitrates, integrating farmer practices both during crop cultivation and in between two successive crops, as well as soil sensitivity to leaching. The evaluation was performed according to the methodological framework proposed by Bockstaller and Girardin [Bockstaller, C., Girardin, P., 2003. How to validate environmental indicators? Agric. Syst. 76, 639–653]: design, output and end-use validation. Design validation involved submission of the method to experts and checking the sub-indicators against literature. Output validation was carried out by comparing real values to indicator outputs. End-use validation was based on information gathered by users. In particular we compared output data from the original method with that of users that had adapted the method to their situation, in order to assess the consequences of these changes. The first step confirmed that the assumptions of MERLIN and its sub-indicators are scientifically sound. However, the weighting of the different sub-indicators raised questions. The second output validation step gave acceptable results for the EQUIF sub-indicator but the MERLIN test highlighted the need for additional experimental data before validation. This approach also showed that improvements in the precision of parameters do not necessarily increase the accuracy of the classification. The last step confirmed that the indicator is considered useful by decision-makers but also reveals that in some cases users adapt parameter values to their situation. This has lead to the production of a user guide which defines the method more clearly to avoid numerous adaptations by users.     

A comparison of WEPP and SWAT for modeling soil erosion of the Zhangjiachong Watershed in the Three Gorges Reservoir Area

Soil and water conservation is important for the Three Gorges Reservoir Area in China, and quantification of soil loss is a significant issue. In this study, two widely used models - the Water Erosion Prediction Project (WEPP) and the Soil and Water Assessment Tool (SWAT) - were applied to simulate runoff and sediment yield for the Zhangjiachong Watershed in the Three Gorges Reservoir Area. The models were run and the simulated runoff and sediment yield values were compared with the measured runoff and sediment yield values. In the calibration period, the model efficiency (E_NS) values for the WEPP and SWAT were 0.864 and 0.711 for runoff, and 0.847 and 0.678 for sediment yield, respectively. In the validation period, the E_NS values for WEPP and SWAT were 0.835 and 0.690 for runoff, and 0.828 and 0.818 for sediment yield, respectively. The results of E_NS and the other criteria indicate that the results of both models were acceptable. WEPP simulations were better than SWAT in most cases, and could be used with a reasonable confidence for soil loss quantification in the Zhangjiachong Watershed.     

CFD-based simulation assessment of an artificial upwelling antibloom system for a salmon farming site

The proliferation of microalgae, also known as microalgal bloom or Harmful Algae Bloom (HAB), is a damaging phenomenon for the correct functioning of salmon farming systems worldwide. Several anti-HAB systems have been developed and are currently being evaluated. One type of system is based on air diffusion from below the ocean surface where the fish farms are located. However, the configuration that would yield the highest efficiency of these systems has yet to be determined. In this work, the effectiveness of current and potential new anti-HAB systems configurations is assessed through computational fluid dynamics (CFD) modeling. The model of the section of the ocean and the air diffusion system was implemented in OpenFOAM representing the zone where the fish farm of Salmones Blumar S.A. is placed. The HAB is assumed to behave as a tracing substance, so the model becomes a three-phase system, which uses an Euler-Euler approach and a k-ε turbulence model, as well as stratified current velocities. The CFD model was validated with onsite data of water velocity at different water depths. Under these conditions, the configuration of the case study diffusers (i.e., 42 diffusers placed in two rows, with an average separation of 4 m between consecutive diffusers, and located 15 m deep) results in a 25 % decrease of the HAB penetration inside the farm. Additionally, placing the diffusers 5 m closer to the water surface increments the efficiency (i.e. HAB concentration reduction) of the system by 75 %, providing a cost-efficient solution, because the number of diffusers and their airflow remain unchanged.     

Modeling hydrodynamics and path/residence time of aquaculture-like particles in a mixed-cell raceway (MCR) using 3D computational fluid dynamics (CFD)

A three-dimensional (3D) simulation of a commercial-size mixed-cell raceway (MCR) was performed using computational fluid dynamics (CFD). Hydrodynamics of the MCR were fully characterized and validated against experimental data. A simulation of path and residence time of aquaculture-like particles was also conducted to understand solids removal mechanisms and potential efficiencies within a mixed-cell. A structured 3D grid model of one mixed-cell was constructed using 250,000 hexahedral elements, and simulations were conducted using the Realizable k–ɛ turbulence model. From the results of the CFD simulations, average cell rotational velocities, radial velocity profiles, and velocity contour and vector plots were generated at three different water depths. As observed in experimental trials conducted by the authors, predicted velocity contours and vector plots revealed the development of a strong rotational flow in each mixed-cell with lower velocity zones at the center and corners of the cells. Also, a linear trend of increasing rotational velocities from the cell's center to its circumferential perimeter was described. Good fluid-flow pattern agreement was observed between the experimental and predicted vector and contour plots. Average rotational velocities at the bottom (95 cm depth), middle (50 cm depth), and top (20 cm depth) planes of the mixed-cell (1-m water depth) were 17.2, 14.9, and 13.7 cm/s, respectively. Comparison of these velocities with the observed values revealed an overall agreement of nearly 96%. Similarly, when the average velocities at radial distances of the MCR were compared at the three depths, the correlation between the experimental and predicted data was on the range of 89–95%.Simulations of aquaculture-like particles trajectories revealed that roughly 100% of particles larger than 500 μm settled and were removed in less than 15 min through the mixed-cell’ central drain. Also, 100% of the 100-μm particles were removed within one mixed-cell hydraulic retention time (HRT) cycle, with approximately half being removed by the bottom-center drain and half being removed via the upper-side drains. Only 50% of the 10-μm particles was removed; and this mainly occurred through the upper-side drains of the mixed-cell after 17 HRT cycles. Smaller particles appeared to stay in the tank for an indefinite period of time.     

The impact of windthrow on carbon sequestration in Switzerland: a model-based assessment

Carbon sequestered in biomass is not necessarily stored infinitely, but is exposed to human or natural disturbances. Storm is the most important natural disturbance agent in Swiss forests. Therefore, if forests are taken into account in the national carbon budget, the impact of windthrow on carbon pools and fluxes should be included. In this article the forest scenario model MASSIMO and the soil carbon model YASSO were applied to assess the effect of forest management and an increased storm activity on the carbon sequestration in Swiss forests. First, the soil model was adapted to Swiss conditions and validated. Second, carbon fluxes were assessed applying the two models under various forest management scenarios and storm frequencies. In particular, the influence of clearing after a storm event on the carbon budget was analyzed. The evaluation of the model results showed that the soil model reliably reproduces the amount of soil carbon at the test sites. The simulation results indicated that, within the simulated time period of 40 years, forest management has a strong influence on the carbon budget. However, forest soils only react slightly to changes in the above-ground biomass. The results also showed that a storm frequency increase of 30% has a small impact on the national carbon budget of forests. To develop effective mitigation strategies for forest management, however, longer time periods must be regarded.     

Evaluation and use of a spatio-temporal model of cropping system effects on gene escape from transgenic oilseed rape varieties: Example of the GeneSys model applied to three co-existing herbicide tolerance transgenes

Gene flow between coexisting oilseed rape varieties and rape volunteers cannot be solely studied on field experiments. Previously, a model (GeneSys: [Colbach, N., Clermont-Dauphin, C., Meynard, J.M., 2001. GeneSys: A model of the inluence of croping system on gene escape from herbicide-tolerant rapeseed crops to rape volunteers. I. Temporal evolution of a population of rapeseed volunteers in a field. Agric. Ecosyst. Environ. 83, 235–253; Colbach, N., Clermont-Dauphin, C., Meynard, J.M., 2001. GeneSys: A model of the inluence of croping system on gene escape from herbicide-tolerant rapeseed crops to rape volunteers. II. Genetic exchanges among volunteer and cropped populations in a small region. Agric. Ecosyst. Environ. 83, 255–270]) was therefore developed to quantify the effects of cropping systems on gene flow from rapeseed varieties to rape volunteers in time and in space. In the present work, the model was improved to simulate simultaneously the spread of three different genes. Four different regions were then surveyed from 1995 to 2001: one region comprised only farmers’ fields with frequent rape crops in the rotations; the three remaining regions comprised the French experimental GMO platforms with 2–3 GM and one non-GM rape variety as well as neighbour farmers’ fields. For all these fields, cropping history was recorded during the study and for at least three previous years. In the first region, rapeseed volunteers were assessed in crops as well as on road and field margins in 1 year. In the three remaining regions, volunteer densities and genotypes were assessed each year after harvest and rape harvest genotypes determined during 2 years. The comparison of simulated and observed data showed that the model usually satisfactorily predicts volunteer densities and genotype proportions as well as harvest genotype proportions. Several problem areas were identified: volunteers in road and field margins were usually badly predicted; the model frequently underestimated volunteer densities in spring crops; gene flow via pollen dispersal was underestimated when the distance from the pollen source increased. The model was then used to simulate the spread of herbicide-tolerant rape volunteers in a region grown with one or several GM herbicide-tolerant varieties and more particularly the stacking of several resistance genes in individuals. The simulations also showed the contamination of the harvest of non-GM rape varieties by GM seeds resulting from gene flow.     

松嫩平原西部草地净初级生产力遥感估算与验证

在CASA模型基础上,根据松嫩平原西部自身特点对模型参数获取方法进行改进.以MODIS NDVI数据和气象数据为主要数据源,估算2000～2009年松嫩平原西部草地净初级生产力,并通过多种方法对估算结果进行精度验证.结果表明:利用气候经验模型估算的太阳总辐射及改进后的水分胁迫因子计算结果精度较高,所作改进在保留原始CASA模型生理生态学基础上简化了模型输入参数,对本研究区是可行的.通过与实测数据(实测值与估算值之间R2 =0.64,P＜0.05)、通量观测数据(估算精度为72％;相关系数R=0.9,P＜0.05)、MODIS NPP产品(总体精度为81.41％)及他人估算结果对比发现,本研究估算的松嫩西部草地NPP结果精度较高.2000～2009年松嫩平原西部草地年NPP总量介于8.46～11.22 TgC之间,平均值为9.92 Tg C.空间上,各年NPP均呈南低北高的分布格局;受气候因素和土壤条件影响,松嫩平原西部黑龙江省部分的草地NPP高于吉林省部分.过去10年间,松嫩西部草地NPP按降序排列依次为:2008＞2005＞2002＞2007＞2003＞2004＞2006＞2009＞2000＞2001.     

Validating mammal monitoring methods and assessing the performance of volunteers in wildlife conservation—“Sed quis custodiet ipsos custodies ?”

Many conservation organisations rely heavily on volunteers, and the government often relies on them to achieve tasks for which funding is insufficient—for example, the monitoring of trends in biodiversity on a national scale. Thus, it is critical to deploy non-professionals effectively. In this study we validated and calibrated the data collected by 155 volunteers, assisting with mammal monitoring at Wytham Woods, Oxfordshire, between April 2000 and December 2001. Tasks included small mammal trapping and handling, surveying and censusing for badgers, estimating deer population sizes from dropping counts, and transect surveys for mammal field signs. We analysed the effects of age, gender, previous experience, physical fitness and aptitude on volunteer performance using quantitative measures and qualitative scores. We found that (1) techniques that could be taught to volunteers without lengthy or specialist training were sufficiently accurate to yield reliable data, (2) with approximately half a day of training in each task, volunteers could produce reliable data, verified by professionals, and (3) volunteer teams brought considerable time savings to many tasks, compared with a single professional researcher. Our analyses show that physical fitness was a significant predictor of a volunteer's ability to perform tasks well and, in our particular sample, a male-bias in volunteer aptitude was apparent in some tasks. Previous experience as a conservation volunteer did not enhance performance over that of novices nor did age have any effect on volunteers’ ability. The overall veracity of volunteer data compared well with data collected using more specialist methods or collected by professional researchers using the same method. Volunteers required more time per task and, while they showed a tendency to underestimate population sizes, their results were consistent. Additionally, the programme helped to raise the environmental awareness of volunteers and their understanding of woodland ecology.     

Increases in the completeness of disease records in dairy databases following changes in the criteria determining whether a record counts as correct

Background

The four Nordic countries: Denmark (DK), Finland (FIN), Norway (NO) and Sweden (SE), all have national databases in which mainly records of treated animals are maintained. Recently, the completeness of locomotor disorder records in these databases has been evaluated using farmers’ recordings as a reference level. The objective of the present study was to see how previous estimates of completeness figures are affected by the criteria determining whether a recording in the database is to be judged correct. These demands included date of diagnosis and disease classification. In contrast with the previous study, a period of time between the date of disease recording in the database and by the farmer was allowed. Further, the calculations were brought to bear on individual locomotor diagnoses instead of a common locomotor disease complex code.

Methods

Randomly selected dairy herds (≥ 15 cows) were invited to participate. During two 2-month periods in 2008 the farmers recorded the diseases they observed on the farm and their recordings constituted a farmer database (FD). These recordings were compared to disease recordings in the National Databases (ND). Earlier calculations of completeness for locomotor complex cases assuming an exact match on date were compared with ±7 day and ±30 day discrepancies calculated in this study.

Results

The farmers in DK, FIN, NO and SE recorded 426, 147, 97 and 193 locomotor disorders, respectively. When a window of ±7 days was allowed there was a relative increase in completeness figures lying in the range of 24–100%. Further increases were minor, or non-existent, when the window was expanded to ±30 days. The same trend was seen for individual diagnoses.

Conclusion

In all four of the Nordic countries a common pattern can be observed: a further increase in completeness occurs when individual locomotor diagnoses recorded by the farmer are permitted to match any locomotor diagnosis recorded in the ND. Completeness increased when both time span and different diagnoses within the locomotor complex were allowed.