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Ecology of Corydalis aquae-gelidae, a rare riparian plantGoldenberg, Douglas M. 29 June 1992 (has links)
Corydalis aquae-gelidae is a large herbaceous perennial
in the Fumariaceae that has high habitat specificity. It is
endemic to the western Cascade Range of Oregon and
Washington, almost entirely on the Mt. Hood and Gifford
Pinchot National Forests. It is a federal C2 candidate
under the Endangered Species Act and a Forest Service
sensitive species.
This study included a niche analysis, i.e., defining
the levels of environmental factors where Corydalis aquaegelidae
grew, and relating its abundance to environmental
variation, using data from the southwestern Mt. Hood
National Forest. Corydalis grew in relatively cool habitats
(between late June and early September, diurnal means were
17.7°C for air temperature, 9.7°C for water temperature, and
10.6°C tor substrate temperature). Elevations were from 460
to 1300 m, on streams from headwaters to the fifth order
Clackamas River. The stream reaches occupied by Corydalis
had relatively small seasonal fluctuations in flow. An
estimated 90% of the plants on the Oak Grove Fork were
submerged yearly, and about 75% of the plants were between
average summer low water level and winter high water level.
The abundance of Corydalis aquae-gelidae was modeled
using principal components analysis, resulting in a
reproduction index (based on the number of seedlings and
juveniles) and a biomass index (from the number of adults,
their average leaf numbers and height, and percent cover).
The abundance of Corydalis was greatest within 5 cm vertical
distance below to 20 cm above the summer water levels, and
within 150 cm horizontal distance to the water. Optimal
water cover was within 10 to 30%. Abundance decreased with
increasing organic material and fines (material <2mm)
substrate cover. Optimal mineral and moss cover were 25 to
50% and 50 to 80% respectively. Abundance increased with
increasing gravel and cobble cover. Abundance was
suppressed where canopy cover was below 20%. GS substrates
(gravel and coarse sand) were most favorable, followed by GX
substrates (gravel and sand dominant, with other materials),
then LX substrates (soil or mud dominant).
Emergence from seeds and rootstocks occurred in late
May and early June. Plants farther from the water flowered
later than those closer to or in the water. Senescence
occurred in late August to mid-September. Temperature
differences and phenological state differences were
generally greater within sites than across the elevational
gradient.
Corydalis aquae-gelidae seeds required 6 to 7 months of
stratification before germination in the laboratory. Under
lab conditions, cold substrates (less than 5.8°C AM low,
12.6°C PM high) reduced growth of Senecio triangularis
seedlings, but not of Corydalis. Corydalis seedlings grew
as rapidly in a greenhouse as in the field, but warmer,
drier treatments produced less rapid growth than cool
treatments with saturated substrates.
Corydalis aquae-gelidae had relatively high allocation
to roots, and slightly below average reproductive
allocation, compared to data for other herbaceous species in
the literature, including species from the same region.
Development was slow; an estimated 8 years were required for
reproductive maturity. Using a growth model and growth
stage data from the field, a population age structure was
hypothesized. Based on this age structure, Corydalis
reproduction appeared to be adequate for population
maintenance.
Seed dispersal was mainly by explosive dehiscence and
flowing water. Corydalis aquae-gelidae was pollinated by
bumblebees (Apidae). VA mycorrhizae were present but
infrequent in the juveniles and seedlings investigated.
Slugs were the most frequent cause of herbivore damage.
Downy mildew (Peronospora) occurred at relatively low
elevations and under relatively low canopy cover. Both
competition with and niche differentiation among streamside
species were thought to occur. Corydalis aquae-gelidae
appeared to be a relatively late-successional plant. The
range of Corydalis aquae-gelidae may be restricted by
dispersal problems, rather than by unfavorable environments,
as apparently suitable habitat existed beyond its range.
Timber harvest and road building have damaged Corydalis
aquae-gelidae populations through direct physical
disturbance and habitat degradation. Water diversion for
the Stone Creek Hydropower Project should lead to loss of
plants from the large Oak Grove Fork populations through
drought and other habitat changes. Fisheries habitat
improvement projects and grazing may also threaten Corydalis
populations. / Graduation date: 1993
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