173 research outputs found
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Some experiments in baiting forest land for the control of small seed eating mammals
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Effects of clearcutting a Douglas-fir stand upon small animal populations in western Oregon
An ecological study of small forest mammals was conducted
from 1964 to 1970. The objectives were to obtain chronological information
relative to the effects of current logging practices on vegetational
succession and small mammal populations.
The locale of the study was in the west-central Cascade Mountains
of Oregon. The principal timber species was Douglas-fir,
Pseudotsuga menziesii. The climate was characterized by heavy precipitation
in the winter and dry summers. Snowfall varied from slight to
heavy. Elevation was 3000 feet.
The study areas were composed of a 125-year-old timbered control
unit, a clearcut non-burned unit, and a clearcut slash-burned unit.
Density and distribution of the small mammals were determined
by live-trapping and release of marked animals. Reproductive information
of some species was noted. Home range areas was computed for the more numerous species of rodents.
More than 4530 individual small mammals of 23 mammalian
species were marked on the three areas during the six years of the
study. Over 90 percent of the total animals caught consisted of five
species: Sorex spp, Eutamias townsendii, Peromyscus maniculatus,
and Microtus oregoni.
The small mammal densities varied from year to year. They
were comparable between units on a monthly basis except for the
unburned clearcut unit which differed for a year following logging.
Shrew numbers, abundant in the forest, were less on the unburned
and sharply reduced on the slash-burned unit. Deermice,
scarce in the closed forest, increased greatly in numbers on the clearcuts.
Chipmunks were abundant in the forest, less on the slash- burned
clearcut unit, and sharply reduced in numbers on the unburned unit.
Creeping mice were scarce in the forest but their numbers erupted on
the clearcuts. Snowshoe hares were, caught periodically in the timber
but not on the clearcuts.
Some species, caught infrequently or known only by sign, are
expected to increase and become more numerous as the vegetation
becomes brushier. These include the snowshoe hare, mountain beaver,
porcupine, and the pocket gopher.
The results of this study suggest that more information is
required relative to the diet of the small mammals. Effects of vegetational manipulation, by selective cutting practices or by the use
of herbicides on small mammals should be examined
The Role of Plant Litter in Driving Plant-Soil Feedbacks
Most studies focusing on plant-soil feedbacks (PSFs) have considered direct interactions between plants, abiotic conditions (e. g., soil nutrients) and rhizosphere communities (e.g., pathogens, mutualists). However, few studies have addressed the role of indirect interactions mediated by plant litter inputs. This is problematic because it has left a major gap in our understanding of PSFs in natural ecosystems, where plant litter is a key component of feedback effects. Here, we propose a new conceptual framework that integrates rhizosphere- and litter-mediated PSF effects. Our framework provides insights into the relative contribution of direct effects mediated by interactions between plants and soil rhizosphere organisms, and indirect effects between plants and decomposer organisms mediated by plant root and shoot litter. We distinguish between three pathways through which senesced root and shoot litter may influence PSFs. Specifically, we examine: (1) physical effects of litter (layer) traits on seed germination, soil structure, and plant growth; (2) chemical effects of litter on concentrations of soil nutrients and secondary metabolites (e.g., allelopathic chemicals); and (3) biotic effects of saprotrophic soil communities that can perform different functional roles in the soil food web, or that may have specialized interactions with litter types, thereby altering soil nutrient cycling. We assess the role of litter in PSF effects via physical, chemical and biotic pathways to address how litter-mediated feedbacks may play out relative to, and in interaction with, feedbacks mediated through the plant rhizosphere. We also present one of the first experimental studies to show the occurrence and species-specificity of litter-mediated feedbacks and we identify critical research gaps. By formally incorporating the plant-litter feedback pathway into PSF experiments, we will further our understanding of PSFs under natural conditions
Competition increases sensitivity of wheat (Triticum aestivum) to biotic plant-soil feedback
Plant-soil feedback (PSF) and plant competition play an important role in structuring vegetation composition, but their interaction remains unclear. Recent studies suggest that competing plants could dilute pathogenic effects, whereas the standing view is that competition may increase the sensitivity of the focal plant to PSF. In agro-ecosystems each of these two options would yield contrasting outcomes: reduced versus enhanced effects of weeds on crop biomass production. To test the effect of competition on sensitivity to PSF, we grew Triticum aestivum (Common wheat) with and without competition from a weed community composed of Vicia villosa, Chenopodium album and Myosotis arvensis. Plants were grown in sterilized soil, with or without living field inoculum from 4 farms in the UK. In the conditioning phase, field inocula had both positive and negative effects on T. aestivum shoot biomass, depending on farm. In the feedback phase the differences between shoot biomass in T. aestivum monoculture on non-inoculated and inoculated soils had mostly disappeared. However, T. aestivum plants growing in mixtures in the feedback phase were larger on non-inoculated soil than on inoculated soil. Hence, T. aestivum was more sensitive to competition when the field soil biota was present. This was supported by the statistically significant negative correlation between shoot biomass of weeds and T. aestivum, which was absent on sterilized soil. In conclusion, competition in cereal crop-weed systems appears to increase cereal crop sensitivity to soil biota
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The porcupine in Oregon : its life history and control
This note was prepared to answer the questions most of ten asked by foresters concerned about the porcupine and its control. The literature was reviewed for information on the animal's life history and the extent of damage in other areas. Direct field work reported was done primarily near Medford, Oregon, in mixed species. Because of the increased amounts of damage occurring west of the Cascade Mountains, however, some observations were made in stands that were almost all Douglas-fir.
It should be understood that control measures are under-taken only after the porcupine has become a pest animal and is causing damage to future crop p-ees. Porcupine populations occurring in noncommercial timber-producing areas are considered as desirable components of the wilderness wildlife
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