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
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29971 |
| Date | 18 April 2002 |
| Creators | Heichen, Rachel S. |
| Contributors | Cromack, Kermit Jr |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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