Nature and Place of Transition from True Prairie to Mixed Prairie

As a memorial to Dr. Frederic E. Clements, it is a pleasure to present this paper on the midcontinental grasslands of North America. Born and reared at Lincoln, Nebraska, he developed a remarkable interest in and love for the prairie. He has often stated to the first author that of all the vegetation of North America, he liked the grassland best. Clements was the first to recognize the Mixed Prairie as a distinct plant association and to describe its nature and range and the grouping of the dominants ( 1920). When one examines the prairies of western Iowa and then proceeds some distance westward, he is impressed by several changes. The vegetation is reduced in height, it becomes less dense, ant1 takes on a distinctly more xeric impress. These changes result from gradually increasing unfavorable water relations as the vegetation of True Prairie gives way to that of Mixed Prairie. Along the Nebraska-Kansas interstate line, for example, the 33-inch annual precipitation near the Missouri River decreases westward at an average rate of about an inch every 15 miles. Conversely, rate of evaporation rapidly increases. In Nebraska, the transition from True to Mixed Prairie occurs over three types of topography. South of the Platte Valley Lowland it has been traced over the nearly level portion of the Loess Plain Region (Fig.1) . Northward, the transition takes place in the greatly dissected Loess Hills and Plains. East of the northern Sandhill Region, it occurs on the Holt-Pierce Plain and Boyd Shale Plain

A Seven-Year Quantitative Study of Succession in Grassland

The study of plant succession has contributed more than any other single line of investigation to a deeper insight into the nature of vegetation. Earlier studies of succession, especially in grassland, were largely those of the primary sere. But with the utilization of the prairies for grazing, and the abandonment of submarginal land after a short period of cropping, numerous investigations of secondary successions were made. The earlier studies have been discussed by Clements (1916) in Plant Succession. Sampson\u27s plant succession in relation to range management appeared in 1919. Many of the more recent investigations of subseres in grassland and on abandoned lands have been reviewed by Drew (1942). Costello (1944) has studied the grassland subsere in northeastern Colorado. Weaver and Albertson (1944) have traced the subsere following the recent great drought over a vast central area of both true and mixed prairie. Information on the rate and nature of natural re-vegetation of depleted ranges and abandoned cultivated land is of basic importance to many problems of soil conservation and land use

Nature and Place of Transition from True Prairie to Mixed Prairie

As a memorial to Dr. Frederic E. Clements, it is a pleasure to present this paper on the midcontinental grasslands of North America. Born and reared at Lincoln, Nebraska, he developed a remarkable interest in and love for the prairie. He has often stated to the first author that of all the vegetation of North America, he liked the grassland best. Clements was the first to recognize the Mixed Prairie as a distinct plant association and to describe its nature and range and the grouping of the dominants ( 1920). When one examines the prairies of western Iowa and then proceeds some distance westward, he is impressed by several changes. The vegetation is reduced in height, it becomes less dense, ant1 takes on a distinctly more xeric impress. These changes result from gradually increasing unfavorable water relations as the vegetation of True Prairie gives way to that of Mixed Prairie. Along the Nebraska-Kansas interstate line, for example, the 33-inch annual precipitation near the Missouri River decreases westward at an average rate of about an inch every 15 miles. Conversely, rate of evaporation rapidly increases. In Nebraska, the transition from True to Mixed Prairie occurs over three types of topography. South of the Platte Valley Lowland it has been traced over the nearly level portion of the Loess Plain Region (Fig.1) . Northward, the transition takes place in the greatly dissected Loess Hills and Plains. East of the northern Sandhill Region, it occurs on the Holt-Pierce Plain and Boyd Shale Plain

Dynamic evolution of the source volumes of gradual and impulsive solar flare emissions

This study compares flare source volumes inferred from impulsive hard X-rays and microwaves with those derived from density sensitive soft X-ray line ratios in the O VII spectrum. The data for this study were obtained with the SMM Hard X-Ray Burst Spectrometer, Earth-based radio observatories, and the SOLEX-B spectrometer on the P78-1 satellite. Data were available for the flares of 1980 April 8, 1980 May 9, and 1981 February 26. The hard X-ray/microwave source volume is determined under the assumption that the same electron temperature or power law index characterizes both the source of hard X-rays and the source of microwaves. The O VII line ratios yield the density and volume of the 2 X 10 to the 6th K plasma. For all three flares, the O VII source volume is found to be smallest at the beginning of the flare, near the time when the impulsive hard X-ray/microwave volume reaches its first maximum. At this time, the O VII volume is three to four orders of magnitude smaller than that inferred from the hard X-ray/microwave analysis. Subsequently, the O VII source volume increases by one or two orders of magnitude then remains almost constant until the end of the flare when it apparently increases again

Music and drama in primary schools in the Madeira Island - Narratives of ownership and leadership

Este artigo foi uma das publicações resultantes do projeto financiado pela FCT "Música e Drama no 1º ciclo do Ensino básico – o caso da Região Autónoma da Madeira" (PTDC/CED/72112/2006).A three-year-case study funded by the Foundation for Science and Technology (FCT) from the Portuguese Ministry of Science, Technology and Higher Education was designed to study a 30-year project of music and drama in primary schools in Madeira. This article reports on the narratives of the three main figures in the project as they elaborate on its construction according to the following themes: innovation, philosophies of music education and teacher education. Through the lens of a narrative inquiry, the discourses produced are analysed, taking into account the emerging concepts of ownership and leadership.

Complexity-based learning and teaching: a case study in higher education

This paper presents a learning and teaching strategy based on complexity science and explores its impacts on a higher education game design course. The strategy aimed at generating conditions fostering individual and collective learning in educational complex adaptive systems, and led the design of the course through an iterative and adaptive process informed by evidence emerging from course dynamics. The data collected indicate that collaboration was initially challenging for students, but collective learning emerged as the course developed, positively affecting individual and team performance. Even though challenged, students felt highly motivated and enjoyed working on course activities. Their perception of progress and expertise were always high, and the academic performance was on average very good. The strategy fostered collaboration and allowed students and tutors to deal with complex situations requiring adaptation

Agency as the Acquisition of Capital: the role of one-on-one tutoring and mentoring in changing a refugee student's educational trajectory

Current research into the experiences of refugee students in mainstream secondary schools in Australia indicates that for these students, schools are places of social and academic isolation and failure. This article introduces one such student, Lian, who came to Australia as a refugee from Burma, and whom the author tutored and mentored intensively during his final year of schooling. The article provides an empirically derived understanding of how one-on-one tutoring and mentoring became a platform through which this student was able to succeed in a structure which systematically tried to exclude him. Here, agency is conceptualised in terms of Bourdieu's concept of capital. The analysis highlights the ways in which one-on-one tutoring and mentoring provided the necessary platform by which this refugee student was able to acquire the necessary capital that effected a positive change in his educational trajectory

The energetics of the gradual phase

Reseachers compare results with those in the chapter by Moore et al. (1980), who reached five main conclusions about the gradual phase: (1) the typical density of the soft X-ray emitting plasma is between 10 to the 11th power and 10 to the 12th power cm-3 for compact flares and between 10 to the 10th power and 10 to the 11th power cm-3 for a large-area flare; (2) cooling is by conduction and radiation in roughly equal proportions; (3) continual heating is needed in the decay phase of two-ribbon flares; (4) continual heating is probably not needed in compact events; (5) most of the soft-X-ray-emitting plasma results from chromospheric evaporation. The goal was to reexamine these problems with the data from the Solar Maximum Mission (SMM) and other supporting instruments as well as to take advantage of recent theoretical advances. SMM is capable of measuring coronal temperatures more accurately and with a better cadence than has been possible before. The SMM data set is also unique in that the complete transit of an active region was observed, with soft X-ray and UV images being taken every few minutes. Researcher's were therefore able to establish the pre-flare conditions of the region and see whether anything has changed as a result of the flare. The assumptions made in attempting to determine the required plasma parameters are described. The derived parameters for the five prime flares are presented, and the role of numerical simulations is discussed

The fundamental cycle of concept construction underlying various theoretical frameworks

In this paper, the development of mathematical concepts over time is considered. Particular reference is given to the shifting of attention from step-by-step procedures that are performed in time, to symbolism that can be manipulated as mental entities on paper and in the mind. The development is analysed using different theoretical perspectives, including the SOLO model and various theories of concept construction to reveal a fundamental cycle underlying the building of concepts that features widely in different ways of thinking that occurs throughout mathematical learning

Calculus-enhanced energy-first curriculum for introductory physics improves student performance locally and in downstream courses

Here we demonstrate the benefits of a new curriculum for introductory calculus-based physics that motivates classical mechanics using a modified version of Hamiltonian mechanics. This curriculum shifts the initial focus of instruction away from forces and the associated vector mathematics, which are known to be problematic for students, to the scalar quantity energy, which is more closely aligned with their previously established intuition, and associated differential and integral calculus. We show that implementation of this calculus-enhanced “energy-first” curriculum resulted in higher normalized gains on the Force Concept Inventory exam for all students and improved performance in downstream engineering courses for students with lower ACT math scores. In other words, the downstream benefits were largest for students with lower math abilities who also pose a larger retention risk. This new curriculum thus has the potential to improve student retention by specifically helping the students who need help the most, including traditionally underserved populations who often have weaker mathematics preparation. We propose future work to investigate whether this new curriculum has lowered the math transference barrier to learning in introductory physics, resulting concomitantly in improvements in student learning of classical mechanics and in student fluency with applied mathematics.Northrop Grumman Foundatio