Dried cattail and bulrush plant pieces in mesh bags were incubated in the
constructed wetland treating Pope & Talbot pulp mill effluent. Two ponds
planted with each species and two depth ranges in each pond were chosen, to
determine decomposition rates. Bags were withdrawn and analyzed at five time
points for the cattail and three for the bulrush. Also a laboratory study was
conducted, where ground cattail and bulrush material was incubated aerobically
and anaerobically. Both species and control were sampled at five time points.
The remaining dry mass and the contents of hemicellulose, cellulose, lignin, and
silica was examined. Decomposition rates were determined by fitting the data to
the single exponential model with the intercept fixed in 1 (100%). An asymptotic
model was used to obtain better fit. The sum of squared errors (SSE) was used
as a measure of fit.
In the field study the ANOVA revealed no change in decomposition with
depth. Neither was there a difference between cattail and bulrush ponds. During
the first two days only the cell compounds are drastically reduced. Cellulose and
hemicellulose start to decline later. Lignin increased slightly during the first half
of the experiment. Decay rates from the single exponential model with the
intercept fixed were higher than the ones listed for wetlands by Webster &
Benfield (1986). The asymptotic model indicates, that there is a fraction, which
does not decompose significantly during the time frame of the experiment. It
predicts 36% cattail and 53% bulrush material to be left after one year of
decomposition.
All samples in the laboratory incubation showed strong leaching during
the first day (26.5% for cattail, 23% for bulrush). After this the t-test (95%
confidence) showed a significant decay coefficient only for the aerobic cattail
samples the model with the best fit. These same samples had an increased cell
component, and a very small particle size at the last sampling time (120 days).
Neither bulrush nor the anaerobic cattail incubations showed the same effect.
Cattail and bulrush plants in the field were labeled to observe the
senescence. Their height and in the case of cattail the amount of green and dry
leaves was recorded monthly. Plants were harvested once a month until
February, and the fiber composition was measured. Cattail was completely dry in
January, while bulrush still showed green spots in February. Cattail entered the
aquatic system mainly by dropping pieces of leaf tips, less by breaking off and
losing the outside leaves. In February the average height of cattail plants was
64.7% of the maximum average height in August. Bulrush plants shortened to
84.1% of the maximum average height from September. Most of the bulrush
plants died through nutria, a rodent, which is chopping off the plants. Less
material was lost by dropping small pieces off the plant tips. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35898 |
| Date | 09 August 1993 |
| Creators | Walz, Anita |
| Contributors | Moore, James A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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