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Biology and chemistry of a meadow-to-forest transition in the Central Oregon CascadesHeichen, Rachel S. 18 April 2002 (has links)
In this study, biological and chemical characteristics were determined for
two high-elevation meadow-to-forest transitions located in the Central Oregon
Cascades. The chloroform fumigation incubation method (CFIM) was used to
determine microbial biomass C(MBC) and the N flush due to fumigation (NF), and
meadow values were compared to forest values for each. Meadow and forest MBC
values were also compared for estimates of MBC determined with microscopy and
these values were compared to CFIM estimates. Net N mineralization and C
mineralization were determined for an 85-d incubation period and used as a
measure of labile C and N. Microbial biomass C and NF were then compared to
these labile pools in order to investigate the relationship between the amount of
each nutrient stored in biomass and the magnitude of the respective labile nutrient
pool for each. Long-term and short-term net N mineralization rates and C/N ratios
were also compared for meadow and forest soils, and the relationship between
these two characteristics was examined.
In general, microbial biomass estimates made with the CFIM method did not
show any significant differences between meadow and forest soils. Mean MBC for
both sites as determined by CFIM was estimated to be 369 and 406 μg C g⁻¹ soil in
meadow and forest soils, respectively. Mean NF was estimated to be 37 and 56 μg
N g⁻¹ soil in meadow and forest soils, respectively. MBC estimates made using
microscopy showed biomass C to be greater in the forest than in the meadow.
Mean MBC as determined by microscopy was estimated to be 529 and 1846 μg C
g⁻¹ soil in meadow and forest soils, respectively. The NF measured as a percentage
of the net N mineralized over 85 d was significantly greater in the forest than in the
meadow soils, but was a substantial percentage in both. The means of these values
were 30 and 166% in meadow and forest soils, respectively. This led to the
conclusion that biomass N may be a very important pool of stored labile N in this
ecosystem. Net N mineralization rates were almost always greater in the meadow
than in the forest soils. Net N mineralization for the 10-d incubations averaged
21 μg N g⁻¹ soil in the meadow and 8 μg N g⁻¹ soil in the forest Rates for long-term
N mineralization averaged 126 μg N g⁻¹ soil in the meadow and 52 μg N g⁻¹
soil in the forest. Net N mineralization rates were correlated with C/N ratios for
both short-term and long-term incubations. / Graduation date: 2002
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The imprint of coarse woody debris on soil biological and chemical properties in the western Oregon CascadesSpears, Julie D. H. 03 April 2002 (has links)
The abundance and spatial heterogeneity of coarse woody debris (CWD)
on the forest floor is a prominent feature of Pacific Northwest (PNW) forest
ecosystems. The effect of CWD on soil solution chemistry, nutrient cycling and
availability, soil physical structure and formation of soil organic matter,
however, remains unknown. Therefore, studies on the spatial and temporal
imprint of CWD on forest soils are timely and can fill critical gaps in our
understanding of the role of CWD in PNW forest ecosystems. I investigated the
effect of CWD on soils and soil solution at the H.J. Andrews Experimental Forest
in a two-part study. Mineral soils were sampled beneath CWD to a depth of 60
cm. The top 15 cm of soil was also repeatedly sampled for seasonal differences.
Control leachate, CWD leachate and soil solution from control soils and from
under CWD were collected from the fall of 1999 until the spring of 2001. Results
indicated that CWD leachates were much more acidic than water leaching from
the forest floor without CWD. Intermediate stages of CWD decomposition had
the highest concentrations of hydrophobic compounds and polyphenols of all
stages of decay. Correspondingly, surface soils sampled from under well-decayed
CWD were more acidic and had more exchangeable acidity and
aluminum, and a lower percent base saturation than soils under the forest floor.
Nutrient pools were not different under CWD, although nitrogen fluxes were
slower under CWD. Although we had hypothesized that the spatial variability
of CWD inputs may affect forest soils under CWD, we found that the spatial
variability is much more temporal than I had hypothesized and is limited to the
top five centimeters of the underlying soil. / Graduation date: 2002
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Soil arthropods in the Central Cascades : slash burning effects and biology of some speciesEstrada-Venegas, Edith G 01 May 1995 (has links)
Despite the recognized role of soil arthropod fauna on nutrient cycling
and decomposition processes, many aspects of the effects of sylvicultural
methods in forest ecosystems upon their biology remain poorly understood.
The long term effects of prescribed fires on soil arthropods in forest
ecosystems in the Pacific Northwest have never been studied.
Soil samples were taken from three sites located in the Willamette
National Forest in 1992: paired sites that were either clear-cut without burning
and clear-cut with burning 40 years ago. One hundred and eight samples
were processed; the arthropods were separated, identified and counted. To
study the biology and behavior of some arthropods, eight species of oribatid
mites were reared in laboratory conditions. Their life cycle, feeding behavior
and reproduction were studied.
Results indicated that there were no statistical significant treatment
differences either in terms of total numbers of organisms or biomass.
However, the majority of the commonest taxa did show offsetting treatment
responses. A total of 204 taxa were found in the three sites. The most
important groups included Collembola, mites, and insects. Other groups also
represented, but in smaller numbers, were spiders, symphylans,
pseudoscorpions, and centipedes. Of all these groups, oribatid mites was the
best represented and appears to be a useful indicator of disturbances. / Graduation date: 1995
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