Terrestrial and Aquatic Ecology Commons^™

Changes In True-Prairie Vegetation During Drought As Determined By List Quadrats, J. E. Weaver, Joseph H. Robertson, Robert L. Fowler

Papers of John E. Weaver (1884-1956)

The drought of 1934 was not only the most severe on record for the true-prairie association but was also of the earliest inception. On June 8, Kincer ('34) stated that "pastures are the poorest ever known, and the hay crop will be extremely short, regardless of future weather." The stress increased as the summer advanced. Stoddart ('35) tood advantage of these conditions to investigate the relation of osmotic pressure and water content of prairie plants to environmental factors in the vicinity of Lincoln, Nebraska. Simultaneously, Nedrow ('37) was conducting trenching experiments in his study of the efficiency of absorption at …

Increase Of Sporobolus Cryptandrus In Pastures Of Eastern Nebraska, J. E. Weaver, Walter W. Hansen

Papers of John E. Weaver (1884-1956)

The severe drought of 1934 to 1938 has resulted in great losses in the plant
populations of native pastures. In Nebraska, little bluestem, Andropogon scoparius, and Kentucky bluegrass, Poa pratensis, have almost disappeared, while big bluestem, Andropogon furcatus, and numerous other important pasture grasses have suffered heavy losses. In addition to shiftings within the plant populations to compensate these losses, such as an enormous increase in side-oats grama, Bouteloua curtipendula, notable and widely spread local extensions have occurred. Over thousands of pastures western wheat grass, Agropyron smithii, has spread widely, and in similar numbers sand …

Relative Efficiency Of Roots And Tops Of Plants In Protecting . The Soil From Erosion, Joseph Kramer, J. E. Weaver

Papers of John E. Weaver (1884-1956)

An increasing realization of the importance of preventing or controlling soil erosion has resulted in numerous scientific investigations. Some of these are concerned with soil characteristics which promote or retard erosivity (Middleton, '30; Middleton et al., '34; Lutz, '34; and Bouyoucos, '35). Many have to do with engineering methods of reducing soil wastage (Bates and Zeasman, '30; Ramser, '30; Roe, '33; and Bartel, '35). But perhaps most were planned to discover the effects of plants in protecting and binding the soil, reducing runoff, and consequent loss of soil and subsoil (Sampson and Weyl, '18; Duley and Miller, '23; Lowdermilk, …

Some Monogenetic Trematodes From The Galapagos Islands And The Neighboring Pacific, Frank Grose Meserve

School of Biological Sciences: Dissertations, Theses, and Student Research

Introduction

Trematodes are parasitic, unsegmented, flattened (rarely cylindrical) worms. They have ventral, anterior, posterior or median attachment organs. The sense organs are poorly developed. The mouth is terminal or ventral and subterminal. The intestine is usually forked with or without lateral branches. The animals, with few exceptions, are hermaphroditic. The ovary is usually single. They have one, two, or more testes. The development is direct with only one host in the ectoparasitic Monogenea and indirect in the Digenea which have two or more hosts. The digenetic trematodes usually parasitize vertebrates which serve as their primary hosts and invertebrates (Mollusca) which …

Comparison Of Runoff And Erosion In Prairie, Pasture, And Cultivated Land, J. E. Weaver, Wm. C. Noll

Papers of John E. Weaver (1884-1956)

Soil erosion resulting from runoff water has come to be recognized as a national menace. The determination and evaluation of all factors influencing runoff and erosion are studies of fundamental importance, especially insofar as they may be made to yield information upon methods of control over this insidious tendency of washing away the land.

"Fully 75 per cent of the crop-producing and grazing areas of the United States is sloping enough to set in motion, moderately or violently, these wasteful processes of accelerated soil-removal and excessive runoff. That 35 million acres of formerly cultivated land have been essentially ruined by …

Quantity Of Living Plant Materials In Prairie Soils In Relation To Run-Off And Soil Erosion, J. E. Weaver, George W. Harmon

Papers of John E. Weaver (1884-1956)

The menace of soil erosion did not appear in the west until much of the prairie was broken for cropping or weakened by continuous overgrazing. The grassland sod is a great conserver of rainfall; the amount of run-off water is relatively small, and the soil is firmly held against the forces of erosion. This study is concerned with the role that the living underground plant parts play in promoting the absorption of water by the soil, and especially their importance in reducing run-off. Their holding of the soil against the forces of water erosion has been experimentally determined. A study …

Root Behavior And Crop Yield Under Irrigation, Frank C. Jean, John E. Weaver

Papers of John E. Weaver (1884-1956)

More than half of the surface of the earth receives insufficient precipitation
for the most favorable growth of crops. The, best method of making up this deficiency is through the application of water by irrigation. Hence the economical use of irrigation water is one of the chief problems of agriculture in arid regions. Since much more land is available than can be irrigated by the supply of water, even when methods of greatest economy are employed, the welfare of these regions demands that the irrigation water be used as efficiently as possible (cf. Harris, 1916). It has been estimated that …

The Ecological Relations Of Roots, John E. Weaver

Papers of John E. Weaver (1884-1956)

Although considerable progress has been made in the study of root systems of desert plants (Cannon, 1911, 1913; Markle, 1917), very little information is available concerning the roots of other native species. During 1914 the writer investigated the root systems of the prairie plants of southeastern Washington, where the annual precipitation is only 21.6 inches and occurs mostly in the period of rest: Since that time it has been planned to make a comparative study of the roots of prairie plants growing in a more humid region and where the precipitation occurs mostly during the season of plant growth. The …

Natural Reforestation In The Mountains Of Northern Idaho, Harry B. Humphrey, John Ernst Weaver

Papers of John E. Weaver (1884-1956)

The factors affecting the natural reforestation of a fire-denuded area may, in general, be said to be the same in Idaho and Oregon as in Maine or Minnesota. There may be and actually are differences in detail as to what species of herbaceous and shrubby plants may prepare the way for the more delicate seedlings of those trees native to the particular locality. But the principle prevails everywhere that certain plants or plant societies. are antecedent and probably essential to the appearance and permanent establishment of a forest. The first step in the reforestation of a fire-swept area is the …

A Study Of The Root-Systems Of Prairie Plants Of Southeastern Washington, John Ernest Weaver

Papers of John E. Weaver (1884-1956)

While carrying on a study of the plant formations and associations of semi-arid southeastern Washington in 1912-1914, it soon became apparent that for a proper understanding of the development and structure of these associations a knowledge of the root-systems of the more important prairie species was imperative. Consequently, during the fall, winter, and spring of 1913--1914, more than 350 root-systems of 25 of the most important ecological species were examined. This paper contains descriptions of these, together with a discussion of the conditions under which the plants grow.

The prairies of southeastern Washington, and their eastward extension into adjacent Idaho, …

The Phytogeography Of Nebraska, Roscoe Pound, Frederic E. Clements

Papers in Systematics & Biological Diversity

From the preface we learn that this work is the result of nearly five years of active study of the floral covering of Nebraska, carried on by the members of the Botanical Seminar in the Botanical Survey of the State of Nebraska. The systematic study of the vegetation of Nebraska was begun by Dr. Bessey in 1884, and has since been carried on by him and his students, all previous collecting having been more or less desultory and unreliable. The Botanical Survey was organized in 1892, and its work has been directed to the collecting of specimens and observations for …

A New Method For The Quantitative Determination Of Plankton Hauls, Henry B. Ward

Studies from the Zoological Laboratory: The University of Nebraska

Only two methods of estimating the quantity of plankton obtained in a haul of the vertical net are known to me. These two may be called the volumetric and the gravimetric. Both have been used by observers in various parts of the world, but so far as I know have never been comparatively tested in order to ascertain the relative value of results obtained by the two. The experience of the past year has shown some disadvantages in the first method, while the second has certain evident objections which rendered its employment in this case out of the question. In …