Contribution of crop model structure, parameters and climate projections to uncertainty in climate change impact assessments

Climate change impact assessments are plagued with uncertainties from many sources, such as climate projections or the inadequacies in structure and parameters of the impact model. Previous studies tried to account for the uncertainty from one or two of these. Here, we developed a triple-ensemble probabilistic assessment using seven crop models, multiple sets of model parameters and eight contrasting climate projections together to comprehensively account for uncertainties from these three important sources. We demonstrated the approach in assessing climate change impact on barley growth and yield at Jokioinen, Finland in the Boreal climatic zone and Lleida, Spain in the Mediterranean climatic zone, for the 2050s. We further quantified and compared the contribution of crop model structure, crop model parameters and climate projections to the total variance of ensemble output using Analysis of Variance (ANOVA). Based on the triple-ensemble probabilistic assessment, the median of simulated yield change was -4% and +16%, and the probability of decreasing yield was 63% and 31% in the 2050s, at Jokioinen and Lleida, respectively, relative to 1981-2010. The contribution of crop model structure to the total variance of ensemble output was larger than that from downscaled climate projections and model parameters. The relative contribution of crop model parameters and downscaled climate projections to the total variance of ensemble output varied greatly among the seven crop models and between the two sites. The contribution of downscaled climate projections was on average larger than that of crop model parameters. This information on the uncertainty from different sources can be quite useful for model users to decide where to put the most effort when preparing or choosing models or parameters for impact analyses. We concluded that the triple-ensemble probabilistic approach that accounts for the uncertainties from multiple important sources provide more comprehensive information for quantifying uncertainties in climate change impact assessments as compared to the conventional approaches that are deterministic or only account for the uncertainties from one or two of the uncertainty sources.

A Model of Leaf Coordination to Scale-Up Leaf Expansion from the Organ to the Canopy

Process-based crop growth models are popular tools with which to analyze and understand the impact of crop management, genotype-by-environment interactions, or climate change. The ability to predict leaf area development is critical to predict crop growth, particularly under conditions of limited resources. Here, we aimed at deciphering growth coordination rules between wheat (Triticum aestivum) plant organs (i.e. between leaves within a stem, between laminae and sheaths, and between the mainstem and axillary tillers) to model the dynamics of canopy development. We found a unique relationship between laminae area and leaf rank for the mainstem and its tillers, which was robust across a range of sowing dates and plant densities. Robust relationships between laminae and sheath areas also were found, highlighting the tight control of organ growth within and between phytomers. These relationships identified at the phytomer scale were used to develop a simulation model of leaf area dynamics at the canopy level that was integrated in the wheat model SiriusQuality. The model was then evaluated using several independent experiments. The model accurately predicts leaf area dynamics under different scenarios of nitrogen and water limitations. It accounted for 85%, 64%, and 73% of the variability of the surface area of leaf cohorts, total leaf area index, and total green area index, respectively. The process-based model of the dynamics of leaf area described here is a key element to quantify the value of candidate traits for use in plant breeding and to project the impact of climate change on wheat growth.

[Can the postoperative pain level be predicted preoperatively?]

PURPOSE OF THE STUDY

We searched for factors present preoperatively which could be used to predict the intensity of postoperative pain.

MATERIAL AND METHODS

We undertook a prospective study among all patients aged over 18 years who underwent shoulder surgery from January to September 2004 in our unit. The study included 86 patients for which the following data were noted preoperatively: past history of pain, intensity and duration of prior pain, triggering factors, localization, psychological context. The intensity of the postoperative pain was measured on a visual analog scale (VAS); measurements were noted up to 24 hours postop then at one month. Data processing was performed with Statview5.5.

RESULTS

Significant postoperative pain was correlated with a prior history of surgical pain, with duration of prior pain, with intensity of preoperative pain, and with depression.

DISCUSSION

Significant sustained preoperative pain can favor memory of pain leading to postoperative sensitivization of nociception neurons. Intense postoperative pain can favor the development of refractory chronic pain.

CONCLUSION

Significant postoperative pain can be expected in the following situations: pain after prior surgery, presence of chronic pain sustained for more than six months, intense preoperative pain, state of depression.

[Metaphyseal and diaphyseal modular femoral stems implanted without cement]

PURPOSE OF THE STUDY

We assessed outcome after total hip arthroplasty (THA) using a dual metaphyseal-diaphyseal modular femoral stem with hydroxyapatite coating on the metaphyseal portion only. Implanted without cement, this stem was adaptable to all the anatomic morphotypes defined by the Noble canal flare index.

MATERIAL AND METHODS

THA was performed in 116 patients (124 hips), mainly for degenerative joint disease (80% for dysplasia). Mean age was 61.2 years. Follow-up was 6.9 years (72-108 months).

RESULTS

There were no preoperative complications excepting 3 cases of neck fissuration without clinical consequence. There was no trochanteric fracture. We had two early and one late dislocations. The Postel Merle d'Aubigné score improved from 8.09 to 17.27. Clinical outcome was not influenced by patient age, weight or morphotype. Radiologically, signs of bone ingrowth were found in more than 80% of the cases. Lucent lines were seen in only 3 cases. There was a single case of migration. No revision was needed among the cases with ossifications (23%, 22% Brooker I) and no femur revisions were required. There was no mechanical problem involving the metaphyseal-epiphysial junction.

DISCUSSION

The dual metaphyseal-diaphyseal modular stem was found to be a safe and effective implant adaptable to all anatomic variations of the femur and providing good primary stability. In our series, 58% of the femurs were "standard" but for one-third of the femurs, the modular stem enabled implantation without cement, particularly in young adults with a dysplasic or funnel-shaped femur.

CONCLUSION

The dual metaphyseal-diaphyseal modular stem was found to be most useful for optimizing total hip arthroplasty without cement.

[Poor results in 183 threaded acetabular cups at a mean 7 years follow-up]

We reviewed 183 threaded rings at a mean 7 years follow-up. Poor résults are frequent: 34 % had been revised and 50 % have radiographic migration, essentially with proximal migration of the cup. Generally, we reoperated with other cememtless implants. The type of threaded cup does not matter (spheric or conic). Only the duration of follow up seems significant. We think that biomecanical strains, rather than physiology, explain these numerous migrations. We have therefore abandoned threaded cups in favour of porous-coated impacted cups.