Long-term effects of ungulate browsing on forest composition and structure

2009 ◽  
Vol 258 ◽  
pp. S44-S55 ◽  
Author(s):  
M. Didion ◽  
A.D. Kupferschmid ◽  
H. Bugmann
Keyword(s):  
Forest Composition ◽  
Long Term Effects ◽  
Ungulate Browsing ◽  
Composition And Structure

scholarly journals Influence of Markets and Forest Composition on Lumber Production in Pennsylvania

2006 ◽  
Vol 23 (2) ◽  
pp. 87-93 ◽  
Author(s):  
William G. Luppold ◽  
Matthew S. Bumgardner
Keyword(s):  
Regional Differences ◽  
Forest Composition ◽  
Hardwood Lumber ◽  
Composition And Structure

Abstract In this study, we examine regional differences in the hardwood timber resources of Pennsylvania and how the combined changes in inventory volume, forest composition, and lumber prices have influenced regional lumber production. Isolation of these relationships is important because shifts in lumber production reflect changes in harvesting activity. In turn, harvesting influences long-term forest composition and structure. We define three hardwood regions in Pennsylvania based on forest composition and present a chronology of regional changes in sawtimber volumes, sawtimber composition, and lumber production. Regional changes in hardwood lumber production were found to be positively related to changes in the price of No. 1 Common lumber adjusted for changes in forest composition between 1970 and 1999. This finding supports our contention that regional changes in lumber production are influenced by a combination of changes in interspecies lumber price and changes in species availability.

Modeling the long-term effects of disturbances on forest succession, Olympic Peninsula, Washington

1986 ◽  
Vol 16 (1) ◽  
pp. 56-67 ◽  
Author(s):  
Virginia H. Dale ◽  
Miles Hemstrom ◽  
Jerry Franklin
Keyword(s):  
Leaf Area ◽  
Pacific Northwest ◽  
Forest Succession ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Forest Composition ◽  
Silver Fir ◽  
Long Term Effects ◽  
Olympic Peninsula

A model of forest development has been adapted for the Pacific Northwest. The regeneration, growth, and death of individual trees are tracked for simulated 0.2 ha plots and tree attributes are aggregated to provide stand measures. The model includes the influence of temperature, soil moisture, light tolerance, and competition on tree growth. Long-term simulations for Douglas-fir dominated forests on the western Olympic Peninsula show that the stand is eventually dominated by western hemlock with silver fir being codominant. Even after 1200 years of subsequent stand development, silver fir fails to replace western hemlock indicating that this is a self-replicating and stable community. Fire, windthrows, insect disturbance, and clear-cut logging followed by replanting are incorporated into the model as single-event disturbances to a 500-year-old forest. For those cases where large Douglas-fir survive the disturbance, stand biomass and leaf area patterns are not significantly impacted until the death of the last large Douglas-fir. The projections were all carried out to the time when the forest is dominated by western hemlock and silver fir. At that time, the differential effect of the earlier disturbance is not apparent from the forest composition, biomass, or leaf area patterns except for the insect disturbance. Following the removal of all Douglas-fir by an insect, leaf area fluctuates regularly with a period of 600 years.

Browse selection by beaver: effects on riparian forest composition

1990 ◽  
Vol 20 (7) ◽  
pp. 1036-1043 ◽  
Author(s):  
Carol A. Johnston ◽  
Robert J. Naiman
Keyword(s):  
Forest Succession ◽  
Riparian Forest ◽  
Basal Area ◽  
Forest Composition ◽  
Maximum Diameter ◽  
Long Term Effects ◽  
Selective Foraging ◽  
Biomass Structure ◽  
Preferred Species

Beaver (Castorcanadensis) herbivory has both immediate and long-term effects on biomass, structure, and composition of riparian forests. Intense beaver foraging of trembling aspen (Populustremuloides Michx.) decreased tree density and basal area by as much as 43% within ~ 1-ha forage zones surrounding two beaver ponds in northern Minnesota. Maximum diameter of trees cut was 43.5 cm; average aspen stem diameter cut was 13.9 and 10.2 cm at the two ponds. Woody biomass harvested per beaver averaged 1.4 Mg•ha−1•year−1 over a 6-year foraging period. Most wood harvested was left on site or used in dam construction, rather than consumed. Selective foraging by beaver decreased the relative importance of preferred species (i.e., P. tremuloides) and increased the importance of avoided species (i.e., Alnusrugosa (Du Roi) Spreng., Piceaglauca (Moench) Voss), with long-term implications to forest succession and dynamics.

Ovarian Dysfunction in Fetally Irradiated Beagles

1977 ◽  
Vol 35 ◽  
pp. 658-659
Author(s):  
T. M. Seed ◽  
M. H. Sanderson ◽  
D. L. Gutzeit ◽  
T. E. Fritz ◽  
D. V. Tolle ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Low Dose ◽  
Long Term Effects ◽  
Ovarian Dysfunction ◽  
Dose Rates ◽  
Highly Sensitive ◽  
Microscopic Evaluation ◽  
Ovarian Pathology ◽  
Normal Offspring

The developing mammalian fetus is thought to be highly sensitive to ionizing radiation. However, dose, dose-rate relationships are not well established, especially the long term effects of protracted, low-dose exposure. A previous report (1) has indicated that bred beagle bitches exposed to daily doses of 5 to 35 R 60Co gamma rays throughout gestation can produce viable, seemingly normal offspring. Puppies irradiated in utero are distinguishable from controls only by their smaller size, dental abnormalities, and, in adulthood, by their inability to bear young.We report here our preliminary microscopic evaluation of ovarian pathology in young pups continuously irradiated throughout gestation at daily (22 h/day) dose rates of either 0.4, 1.0, 2.5, or 5.0 R/day of gamma rays from an attenuated 60Co source. Pups from non-irradiated bitches served as controls. Experimental animals were evaluated clinically and hematologically (control + 5.0 R/day pups) at regular intervals.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Sign in / Sign up

Export Citation Format

Share Document