The effects of beaver in riverbank forest succession

1988 ◽  
Vol 66 (1) ◽  
pp. 40-44 ◽  
Author(s):  
William J. Barnes ◽  
Eric Dibble
Keyword(s):  
Woody Plants ◽  
Forest Succession ◽  
Tree Density ◽  
Future Generations ◽  
Concomitant Increase ◽  
Silver Maple ◽  
West Central ◽  
Major Reduction

The effects of beaver cutting on forest succession were studied on the banks of the lower Chippewa River in west central Wisconsin, U.S.A. Beavers were often found to be selective in their choice of woody plants, preferring ash and yellowbud hickory over all other species present. The effect of beaver cutting on tree density was substantial, with greatly reduced densities of trees in areas inhabited by beavers. The effects of beaver on the predicted composition of future generations of trees was also substantial. A major reduction in density is predicted for future populations of ash, hickory, and hackberry in areas of beaver activity, with a concomitant increase in the density of basswood and elm and possibly silver maple and prickly ash.

scholarly journals Differential seedling establishment of woody plants along a tree density gradient in Neotropical savannas

2012 ◽  
Vol 100 (6) ◽  
pp. 1411-1421 ◽  
Author(s):  
Ana Salazar ◽  
Guillermo Goldstein ◽  
Augusto C. Franco ◽  
Fernando Miralles-Wilhelm
Keyword(s):  
Density Gradient ◽  
Seedling Establishment ◽  
Woody Plants ◽  
Tree Density ◽  
Neotropical Savannas

scholarly journals Successional trajectories and rates of change in sub-tropical Quercus forests in west-central Mexico: evidences from a permanent plot network

2018 ◽  
Vol 24 (3) ◽  
Author(s):  
Miguel Olvera-Vargas ◽  
Blanca Lorena Figueroa-Rangel
Keyword(s):  
Time Scales ◽  
Forest Succession ◽  
Detrended Correspondence Analysis ◽  
Rate Of Change ◽  
Environmental Drivers ◽  
Permanent Plots ◽  
Central Mexico ◽  
Contributing Factors ◽  
West Central ◽  
Different Time Scales

Forest succession was studied in sub-tropical high-altitude, Quercus-dominated forest in west-central Mexico in order to address the following research questions: (1) How do successional trajectories progress in three contrasting floristic zones? (2) Which is the magnitude of successional rate of change at different time-scales? (3) What are the major environmental drivers contributing to the observed patterns of forest succession? Data was derived from 86 non-managed permanent plots, 500 m2 each, established along a 10 km floristic gradient, ranging from xeric to mesic sites. In portraying successional trajectories over time and to measure the magnitude of rate of change in three floristic zones, Detrended Correspondence Analysis (DCA) was developed. In order to represent the most significant environmental drivers on patterns of successional trajectories and successional rate of change, we used generalized linear models with gaussian error. Results showed that successional trajectories were not deterministic in each of the floristic zones over the different time-scales analysed; instead we observed four successional trajectories i) plots with an outstanding displacement between time periods, accompanied by an erratic migration over the DCA diagram; ii) plots with a moderate rate of change and uniform movement across the ordination space; iii) a small number of plots with slight change and; iv) few plots with no changes. Soil related variables such as pH, P, N, Mg and Mn, together with slope and catena, were predicted as important contributing factors related to successional processes.

scholarly journals Do Woody Tree Thinning and Season Have Effect on Grass Species’ Composition and Biomass in a Semi-Arid Savanna? The Case of a Semi-Arid Savanna, Southern Ethiopia

2021 ◽  
Vol 9 ◽  
Author(s):  
Malicha Loje Hare ◽  
Xin Wen Xu ◽  
Yong Dong Wang ◽  
You Yuan ◽  
Abule Ebro Gedda
Keyword(s):  
Species Composition ◽  
Woody Plants ◽  
Species Abundance ◽  
Control Plot ◽  
Tree Density ◽  
Grass Species ◽  
Southern Ethiopia ◽  
Forage Production ◽  
Multivariate Technique ◽  
Semi Arid

Encroachment of woody plants has negative effects on grass species and seriously challenging livestock production and pastoral livelihood in semi-arid savanna. The effect of thinning and season on grass species composition and biomass was investigated in lowland grazing area for three seasons. The study consisted of 15 plots (each 50 m × 50 m), thinned to differing intensities. The plots were located next to each other on a homogeneous area of 3.8 ha. Five thinning intensities (0, 25, 50, 75, and 100%) were allocated randomly to the plots and replicated three times. The 0% plot was left unthinned referred to as the control plot. The remaining plots were thinned to the equivalents of 25, 50, 75, and 100% of the tree density of that of the control plot. A two-way analysis of variance and Tukey Honest Significant Differences tests were used to compare responses of grass species. Ordination of variables was carried out by multivariate technique using correspondence analysis to explore the similarity relationship of plots, seasons and species. The differences in species composition and biomass in the control and the thinned plots were significant (p < 0.05). Higher grass species composition and biomass were documented in thinned plots than in the control plot. Species abundance in thinned plots ranged from 11 to 12, while that of the 0% plot was six species. Grass biomass (Kg ha-1) varied from 2,688.4 ± 736.8 to 5,035.8 ± 743.9 across thinned plots, whereas in the control plot the yield was 885.8 ± 369.1. The result showed that grass species composition and biomass increased with the increasing intensity of thinning. Grass values appeared to be optimum at the heavy intensity of thinning woody plants. Seasons were also significant with the highest values recorded in the rainy season. Rainfall played an important role by interacting with thinning and influenced total grass values. Overall, thinning that combined improved soil moisture negatively influenced woody cover and enhanced grass species composition and biomass production. Thinning of bushes to the 75% of tree density would sustain the original savanna and maximize forage production for grazers.

Comparison of Choriocarcinoma and Normal Placenta

1971 ◽  
Vol 29 ◽  
pp. 324-325
Author(s):  
John C. Garancis ◽  
Roland A. Pattillo ◽  
Robert O. Hussa ◽  
Jon V. Straumfjord
Keyword(s):  
Cell Lines ◽  
Small Cells ◽  
Tissue Cultures ◽  
Glycogen Depletion ◽  
Cell Surfaces ◽  
Intercellular Spaces ◽  
Concomitant Increase ◽  
Gestational Choriocarcinoma ◽  
Cytoplasmic Glycogen ◽  
Normal Placenta

Two different cell lines (Be-Wo and Jar) of human gestational choriocarcinoma have been maintained in continuous tissue culture for a period of four and two years respectively without losing the ability to elaborate human chorionic gonadotropin (HCG). Tissue cultures, as revealed by electron microscopy, consisted of small cells with single nuclei. In some instances cell surfaces were provided with microvilli but more often the intercellular spaces were narrow and bridged by desmosomes. However, syncytium was not formed. Endoplasmic reticulum (ER) was poorly developed in both cell lines, except in some Be-Wo cells it was prominent. Golgi complex, lysosomes and numerous free ribosomes, as well as excessive cytoplasmic glycogen, were present in all cells (Fig. 1). Glycogen depletion and concomitant increase of ER were observed in many cells following a single dose of 10 ugm/ml of adrenalin added to medium (Fig. 2).

Effects of Noise and Increased Vocal Intensity on Stuttering

1977 ◽  
Vol 20 (2) ◽  
pp. 233-240 ◽  
Author(s):  
Sharon F. Garber ◽  
Richard R. Martin
Keyword(s):  
Normal Level ◽  
Auditory Feedback ◽  
Concomitant Increase ◽  
Vocal Intensity ◽  
Presence And Absence

The present study was designed to assess the effects of increased vocal level on stuttering in the presence and absence of noise, and to assess the effects of noise on stuttering with and without a concomitant increase in vocal level. Accordingly, eight adult stutterers spoke in quiet with normal vocal level, in quiet with increased vocal level, in noise with normal level, and in noise with increased level. All subjects reduced stuttering in noise compared with quiet conditions. However, there was no difference in stuttering when subjects spoke with normal compared with increased vocal level. In the present study, reductions in stuttering under noise could not be explained by increases in vocal level. It appears, instead, that reductions in stuttering were related to a decrease in auditory feedback. The condition which resulted in the largest decrease in auditory feedback, speaking in noise with a normal level, also resulted in the largest decrease in stuttering.

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