Microbial Community and Enzyme Activities in Prairie Soil Ecosystems Under Different Management

The aim of this study was to evaluate the effects of long-term management practices on microbial properties and biochemical processes related to C, N, and P cycling of semiarid prairie soil ecosystems. The management systems included undisturbed, abandoned from cultivation, moderately grazed, heavily grazed and cultivated soils. Soil chemical and microbial properties, enzyme activities involved in C, N and P cycling, microbial diversity and community structure were tested in surface soil samples taken from nine randomly selected plots for each treatment. The spatial variability and dependency of organic C and microbial biomass and activity were also evaluated. The moderately grazed system had similar chemical properties, and microbial biomass and activity to the undisturbed soil ecosystem. More intensive grazing reduced organic C and total N. Grazed systems showed similar activities for most enzyme activities tested to the undisturbed system. Long-term cultivation decreased organic C, total N, total P, and microbial biomass and activity, while increasing the concentrations of labile nutrients. Enzyme activities were the least in the cultivated system, indicating its lower potential for C, N and P transformations, and resulted in accumulation of organic P. The abandoned from cultivation system had intermediate organic matter, microbial biomass, and enzyme activities between the cultivated and the undisturbed and grazed systems. The undisturbed soils had the most diverse microbial communities with relatively higher proportions of k-strategists, while the cultivated had the least diverse microbial communities with high proportions of r-strategists. Microbial biomass C and N were the most spatially variable, especially in cultivated soils. The spatial structure of microbial biomass in cultivated soils revealed a periodicity caused by cultivation operations. Overall, through secondary succession the abandoned soil ecosystem indicated slow recovery from cultivation, and that it can regain its capacity to sequester C and to recycle nutrients. Grazing did not degrade soil chemical and microbial properties, sustains the biochemical capacity of the soil ecosystem for nutrient cycling, and in particular moderate grazing can be a sustainable management alternative for the semiarid soil ecosystems of the Southern Great Plains.Department of Plant and Soil Science

Impacts of zero tillage on soil enzyme activities, microbial characteristics and organic matter functional chemistry in temperate soils

Zero tillage management of agricultural soils has potential for enhancing soil carbon (C) storage and reducing greenhouse gas emissions. However, the mechanisms which control carbon (C) sequestration in soil in response to zero tillage are not well understood. The aim of this study was to investigate the links between zero tillage practices and the functioning of the soil microbial community with regards to C cycling, testing the hypothesis that zero tillage enhances biological functioning in soil with positive implications for C sequestration. Specifically, we determined microbial respiration rates, enzyme activities, carbon source utilization and the functional chemistry of the soil organic matter in temperate well drained soils that had been zero tilled for seven years against annually tilled soils. Zero tilled soils contained 9% more soil C, 30% higher microbial biomass C than tilled soil and an increased presence of aromatic functional groups indicating greater preservation of recalcitrant C. Greater CO2 emission and higher respirational quotients were observed from tilled soils compared to zero tilled soils while microbial biomass was 30% greater in zero tilled soils indicating a more efficient functioning of the microbial community under zero tillage practice. Furthermore, microbial enzyme activities of dehydrogenase, cellulase, xylanase, β-glucosidase, phenol oxidase and peroxidase were higher in zero tilled soils. Considering zero tillage enhanced both microbial functioning and C storage in soil, we suggest that it offers significant promise to improve soil health and support mitigation measures against climate change

Academic vocabulary in teaching greek for academic purposes

Academic vocabulary is an important component of academic discourse. However, acquisition of academic vocabulary is not an easy task. Additional difficulties arise from the fact that there are no tools to map the Greek academic vocabulary. This dissertation aims at defining the Greek academic vocabulary by compiling a Greek academic vocabulary word list, describing the features of the Greek academic vocabulary, and considering the pedagogical implications in teaching Modern Greek for academic purposes. The theoretical approach followed is based on the principles and methods of corpus linguistic analysis. This research made use of an academic sub-corpus of the Corpus of Greek Texts of 1,500,000 words. The sub-corpus includes texts representing three scientific disciplines: humanities, socio-economics and science. The analysis was carried out using the software Wordsmith Tools 4. The Greek Academic Word List consists of 249 word forms that occur frequently in academic texts of all disciplines. These are words that refer to activities that characterize the academic work (research, data analysis, evaluation), shape the rhetoric of academic texts and organize scientific discourse. The lexicogrammatical and semantic characteristics of academic words are revealed by using the concordancer, a computing tool which is able to recover from the text all contexts for a particular item. The analysis of the first 20 word forms of the Greek Academic Word List by using concordances reveals the richness of such linguistic information. The Greek Academic Vocabulary List can be an indispensable component in a program of direct instruction of academic vocabulary. A corpus-based teaching approach could improve academic vocabulary acquisition and thus facilitate comprehension and production of academic discourse.Το ακαδημαϊκό λεξιλόγιο αποτελεί ένα από τα στοιχεία που συμβάλλουν στη σύνθεση και την οργάνωση του επιστημονικού λόγου, ωστόσο η εκμάθηση και η διαχείρισή του δεν αποτελεί εύκολη υπόθεση. Το πρόβλημα γίνεται πιο δύσκολο, καθώς δεν υπάρχουν εργαλεία που να χαρτογραφούν αυτή την περιοχή του λεξιλογίου για την ελληνική γλώσσα. Η διατριβή αυτή έχει ως στόχο τον προσδιορισμό του ακαδημαϊκού λεξιλογίου της Ελληνικής με τη δημιουργία σχετικού καταλόγου, την περιγραφή των χαρακτηριστικών του λεξιλογίου αυτού και τη διερεύνηση των δυνατοτήτων αξιοποίησης του Καταλόγου στη διδασκαλία της Ελληνικής για ακαδημαϊκούς σκοπούς. Η θεωρητική προσέγγιση της διατριβής στηρίζεται στις αρχές και τις μεθόδους της γλωσσικής ανάλυσης με σώματα κειμένων. Για τη δημιουργία του Καταλόγου χρησιμοποιήθηκε σώμα κειμένων ακαδημαϊκού λόγου 1.500.000 λέξεων που προέρχεται από το Σώμα Ελληνικών Κειμένων και περιλαμβάνει κείμενα από τρία πεδία επιστημών: ανθρωπιστικές, κοινωνικο-οικονομικές και θετικές. Για την επεξεργασία των δεδομένων και τη δημιουργία του Καταλόγου Ακαδημαϊκού Λεξιλογίου της Ελληνικής χρησιμοποιήθηκε το λογισμικό Wordsmith Tools 4. Ο Κατάλογος περιλαμβάνει 249 λεξικούς τύπους που εμφανίζονται με αυξημένη συχνότητα στα ακαδημαϊκά κείμενα, ανεξαρτήτως επιστήμης. Πρόκειται για λέξεις που αφορούν και πραγματώνουν λεξικά την ερευνητική διαδικασία σε όλα τα στάδιά της (έρευνα, ανάλυση δεδομένων, αξιολόγηση), συμβάλλουν στην οργάνωση των ακαδημαϊκών κειμένων και στη διαμόρφωση της ταυτότητας και της ρητορικής τους. Σημαντικό εργαλείο για την ανάδειξη των λεξικογραμματικών και σημασιολογικών χαρακτηριστικών του ακαδημαϊκού λεξιλογίου αποτελούν οι συμφραστικοί πίνακες, καθώς θέτουν στη διάθεση του ερευνητή ή/και μελετητή τα συμφραζόμενα αυθεντικού λόγου στα οποία εμφανίζονται οι λέξεις. Η ανάλυση των 20 πρώτων λεξικών τύπων του Καταλόγου με τη χρήση των συμφραστικών πινάκων αποκαλύπτει των πλούτο των γλωσσικών πληροφοριών που εμπεριέχεται σε αυτούς. Πολλές μάλιστα από αυτές τις πληροφορίες δεν είναι καταγεγραμμένες σε λεξικά και γραμματικές. Η αξιοποίηση του Καταλόγου Ακαδημαϊκού Λεξιλογίου της Ελληνικής σε ένα πρόγραμμα άμεσης διδασκαλίας και η εφαρμογή μιας διδακτικής μεθόδου που βασίζεται σε δεδομένα και περιλαμβάνει τη χρήση ηλεκτρονικών σωμάτων κειμένων ως διδακτικού υλικού μπορεί να συμβάλλει στην κατάκτηση του ακαδημαϊκού λεξιλογίου, διευκολύνοντας την κατανόηση και την παραγωγή του ακαδημαϊκού λόγου

Optimal disinfection times for seeds of Mediterranean orchids propagated on nutrient media

A time-consuming yet mandatory step during in vitro sexual propagation of orchids is the treatment of seeds with a disinfecting solution that also serves to scarify the seeds. If the seeds are not properly disinfected, microorganisms grow within the culture vessel, thus reducing the efficacy of the process and burdening the operation with unnecessary materials and labour. On the other hand, a long period of disinfection may damage the seed. The literature is inconclusive with respect to the proper combination of solution strength and duration of the treatment, especially with respect to Mediterranean orchids. The objective of this research is to determine optimal disinfection/scarification times for two species with thin and thick seed coats, respectively. Seeds of Anacamptis laxiflora (Lam.) and Himantoglossum robertianum (Loisel.) were treated in 1% NaClO solution for 5, 15, 25, 35 and 45 minutes and sown in modified organic Malmgren medium. Logistic regression models were fitted to the results. Due to the small number of observations per treatment, regression models of infection rates on treatment duration had no more predictive ability than the mean infection rate. On the other hand, regression models of germination rates on treatment duration proved statistically significant or nearly so. Treatment of only a few minutes in 1% NaClO seems to be optimal for seeds with relatively permeable seed coats such as those of A. laxiflora (Lam.). Conversely, treatment of 45 minutes in 1% NaClO may be inadequate for seeds with relatively impermeable seed coats such as those of H. robertianum (Loisel.)