Deriving crop productivity indicators from satellite synthetic aperture radar to assess wheat production at field-scale.

Richter, G. M. Industrial supervisor ( Rothamsted Research) Burgess, Paul J. and Meersmans, Jeroen Associate supervisorsThe deployment of high-revisit satellite-based radar sensors raises the question of whether the data collected can provide quantitative information to improve agricultural productivity. This thesis aims to develop and test mathematical algorithms to describe the dynamic backscatter of high-resolution Synthetic Aperture Radar (Sentinel-1) in order to describe the development and productivity of wheat at field-scale. A time series of the backscatter ratio (VH/VV), collected over a cropping season, could be characterised by a growth and a senescence logistic curve and related to critical phases of crop development. The curve parameters, referred to as Crop Productivity Indicators (CPIs), compared well with the crop production for three years at the Rothamsted experimental farm. The combination of different parameters (e.g. midpoints of the two curves) helped to define CPIs, such as duration, that significantly (r = 0.61, p = 0.05) correlated with measured yields. Field observations were used to understand the wheat evolution by sampling canopy characteristics across the seasons. The correlation between the samples and the CPIs showed that structural changes, like biomass increase, influence the CPIs during the growth phase, and that declining plant water content was correlated with VH/VV values during maturation. The methodology was upscaled to other farms in Hertfordshire and Norfolk. The ANOVA identified significant effects (p<0.001) of farm management, year (weather conditions) and the interaction between soil type and year on the selected CPIs. Multilinear regression models between yields and selected CPIs displayed promising predictive power (R²= 0.5) across different farms in the same year. However, these models could not explain yield differences within high-yielding farms across seasons because of the dominant effect of weather patterns on the CPIs in each year. The potential impact of the research includes estimation of yield across the landscape, phenology monitoring and indication biophysical parameters. Future work on SAR-derived CPIs should focus on improving the correlations with biophysical properties, applying of the methodology in other crops, with different soils and climates.PhD in Environment and Agrifoo

Τραυματισμοί στο άθλημα της αντισφαίρισης - πρόληψη -αντιμετώπιση -θεραπεία

Σκοπός της εργασίας είναι η αναφορά στους τραυματισμούς της αντισφαίρισης τόσο στα άνω άκρα όσο και στα κάτω άκρα των αθλητών. Στην εργασία γίνεται αναφορά τόσο στην πρόληψη των τραυματισμών όσο και στην επιδημιολογία αλλά και στην διάγνωση και θεραπεία αυτών, καθώς και στις μεθόδους αποφυγής των τραυματισμών. Η μέθοδος που πραγματοποιήθηκε στην εργασία αυτή στηρίζεται στην βιβλιογραφική έρευνα. Η μέθοδος αφορούσε τη μελέτη της υπάρχουσας βιβλιογραφίας με σκοπό να χρησιμοποιηθεί για θεωρητικά συμπεράσματα. Οι πληροφορίες που αφορούν το βιβλιογραφικό μέρος της εργασίας ανακτήθηκαν από την αναζήτηση αρθρογραφίας από ιστοσελίδες. Τα άρθρα αφορούσαν τους τραυματισμούς των αθλητών αντισφαίρισης καθώς και την πρόληψη αλλά και την θεραπεία αυτών. Τα άρθρα που χρησιμοποιήθηκαν αφορούσαν το θέμα της εργασίας και ήταν στην αγγλική γλώσσα. Μεταφράστηκαν και χρησιμοποιήθηκαν εκείνα τα στοιχεία που εξυπηρετούσαν τους σκοπούς της εργασίας. Για την αποφυγή τυχόν τραυματισμών κατά τη διάρκεια του αγώνα ή της προπόνησης προτείνετε οι τενίστες να : ξεκινούν με σωστή προθέρμανση, κάνουν συχνά διαλείμματα, επιλογή του κατάλληλου εξοπλισμού, βελτίωση της τεχνικής, σταμάτημα εάν υπάρξει ενόχληση ή πόνος, αφιέρωση χρόνου για αποθεραπεία.The purpose of this paper is to report on tennis injuries in both the upper and lower extremities of athletes. The work refers to the prevention of injuries as well as to epidemiology but also to their diagnosis and treatment, as well as to the methods of avoiding injuries. The method carried out in this work is based on bibliographic research. The method involved the study of the existing literature in order to be used for theoretical conclusions. The information regarding the bibliographic part of the work was retrieved from the search for articles from websites. The articles concerned the injuries of tennis players as well as their prevention and treatment. The articles used were related to the topic of the paper and were in English. Those elements that served the purposes of the work were translated and used. To avoid any injuries during the match or training, suggest that tennis players: start with a proper warm-up, take frequent breaks, choose the right equipment, improve technique, stop if there is discomfort or pain, take time to recover

Modelling study to quantify the impact of future climate and land use changes on water resources availability at catchment scale

The focus of this study was to investigate the impact of climate and land-use changes on water resources and to find suitable drought indices to identify the occurrence, frequency and severity of the past and future drought events. The Ebbw catchment, Wales, UK was selected for this study. Data for the 1961–2012 period were used as input to the DiCaSM model. Following model calibration and validation, the model was run with UKCP09 future climate scenarios for three periods (30 years each) up to 2099 under three emission scenarios. The reconnaissance drought index, the standardized precipitation index, soil moisture deficit and the wetness index were able to reproduce the past drought events. The data of UKCP09, simple change factors to temperature (± �C) and rainfall (%) using Joint Probability plot and daily values of the weather generator were input to the model. The projections indicated that the streamflow and groundwater recharge are likely to increase in winter and to decrease in spring, summer and autumn. Under all emission scenarios, the greatest decrease in groundwater recharge and the streamflow is projected in the 2050s and 2080s under high emission scenario. Moreover, under medium and high emission scenarios, severity and frequency of the drought events are likely to be high. Land use change from grass and/or arable to woodland had significant impact on water resources

Deriving wheat crop productivity indicators using Sentinel-1 time series

High-frequency Earth observation (EO) data have been shown to be effective in identifying crops and monitoring their development. The purpose of this paper is to derive quantitative indicators of crop productivity using synthetic aperture radar (SAR). This study shows that the field-specific SAR time series can be used to characterise growth and maturation periods and to estimate the performance of cereals. Winter wheat fields on the Rothamsted Research farm in Harpenden (UK) were selected for the analysis during three cropping seasons (2017 to 2019). Average SAR backscatter from Sentinel-1 satellites was extracted for each field and temporal analysis was applied to the backscatter cross-polarisation ratio (VH/VV). The calculation of the different curve parameters during the growing period involves (i) fitting of two logistic curves to the dynamics of the SAR time series, which describe timing and intensity of growth and maturation, respectively; (ii) plotting the associated first and second derivative in order to assist the determination of key stages in the crop development; and (iii) exploring the correlation matrix for the derived indicators and their predictive power for yield. The results show that the day of the year of the maximum VH/VV value was negatively correlated with yield (r = −0.56), and the duration of “full” vegetation was positively correlated with yield (r = 0.61). Significant seasonal variation in the timing of peak vegetation (p = 0.042), the midpoint of growth (p = 0.037), the duration of the growing season (p = 0.039) and yield (p = 0.016) were observed and were consistent with observations of crop phenology. Further research is required to obtain a more detailed picture of the uncertainty of the presented novel methodology, as well as its validity across a wider range of agroecosystem

Learning from failure: Damage and failure of masonry structures, after the 2017 Lesvos earthquake (Greece)

On the 12th of June 2017 an earthquake of Mw = 6.3 struck SSE of Lesvos Island, causing one human fatality and severe damage to the built environment. The traditional settlement of Vrissa was the most affected area, having masonry structures as the majority of its building stock. The objective of the present study is two-fold: to present the structural damage and failure patterns induced by the Lesvos earthquake to masonry structures; to highlight the causes and weaknesses that led to damage, or the factors that prevented it. Particular attention is paid to traditional construction techniques and architectural features that contributed to the seismic response of the structures, either having beneficial or detrimental effect. To this end, a field reconnaissance has been conducted and meaningful technical conclusions are drawn by the observations. Structural systems of both unreinforced and timber-reinforced masonry are inspected. Besides the identification of frequent cases of local, out-of-plane and in-plane mechanisms, combined global mechanisms are also pointed out. Finally, insight into the performance of past interventions is also given, assisting the challenging task of engineering practice.This work was partly funded by project STAND4HERITAGE that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 833123), as an Advanced Grant

Επίδραση της προσθήκης compost στην δομή του εδάφους και στα χημικά χαρακτηριστικά του - περίπτωση της Μηλιάς Χανίων

Μη διαθέσιμη περίληψηNot available summarizatio

Factors Controlling Soil Structure Dynamics and Carbon Sequestration Across Different Climatic and Lithological Conditions

Soil organic carbon (SOC) is a strong determinant of soil fertility through its positive effects on soil structure and soil chemical and biological properties which in turn stimulate primary production. The objective of this work was to simulate field sites that represent different land uses and management practices in three continents, in order to identify the most important factors controlling soil structure dynamics and C sequestration across different climatic and lithological conditions as well as to quantify the rates of the aforementioned processes. The carbon, aggregation, and structure turnover (CAST) model was used to simulate SOC sequestration, aggregate formation, and structure dynamics in three field sites including nontilled soils of natural ecosystems and tilled soils of agricultural fields in Europe (Critical Zone Observatories (CZO) of the SoilTrEC network) and one site in North America. Derived data from the simulations’ results of SOC stocks and water-stable aggregate (WSA) particle size distribution, together with the respective results of three additional sites (Damma Glacier CZO, Milia (Greece), and Heilongjiang Mollisols (China)), were statistically analyzed in order to determine the factors affecting SOC sequestration and soil structure development. The natural ecosystems include nontilled soils covered with natural local vegetation, while the agricultural sites include cultivated and tilled soils covered with crops. The natural ecosystems were represented by Damma Glacier CZO (Switzerland), Heilongjiang Mollisols (China), Koiliaris CZO (Greece), Clear Creek (United States), and the Slavkov Forrest CZO (Czech Republic), whereas the agricultural field sites were located at Heilongjiang Mollisols (China), Koiliaris CZO (Greece), Clear Creek (United States), Marchfeld CZO (Austria), and Milia (Greece). Principal component analysis (PCA) identified clay content, bulk density, climatic conditions (precipitation and evapotranspiration), organic matter (OM), and its decomposition rates as the most important factors that controlled soil structure development. The relative importance of each of these factors differs under differing climatic and lithological conditions and differing stages of soil development. Overall, the modeling results for both natural ecosystems and agricultural fields were consistent with the field data. The model reliably simulated C and soil structure dynamics in various land uses, climatic conditions, and soil properties providing support for the underlying conceptual and mathematical modeling and evidence that the CAST model is a reliable tool to interpret soil structure formation processes and to aid the design of sustainable soil management practices