The Rhizome morphology and sensitivity to ground disturbance of Cypripedium fasciculatum : report

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United States
Department of
Agriculture

Forest

Service

Wenatchee National
Forest

Leavenworth Ranger R.D.

600 Sherboume

Leavenworth, WA 98826-1299
509-548-6977

Date: May, 1994

Reply to: 2670

REPORT:

The Rhizome Morphology and Sensitivity to Ground Disturbance of

Cypripedium fasciculatum

Richy J. Harrod, District Plant Ecologist

Introduction

Cypripedium fasciculatum is a rare terrestrial orchid found in a few scattered
locations throughout several western states. Populations are relatively abundant on the
Leavenworth Ranger District compared to other known locations; about 25 populations
have been located to date. In an attempt to better understand aspects of the species life
history, an individual clump of plants was excavated to determine if the species was
rhizomatous. The following discussion is the result of this excavation.

Results and Discussion

In the fall of 1993, we determined that C. fasciculatum was rhizomatous by
excavating the duff and an about 3-5 cm of soil away from a cluster of aerial stems. We
were careful to only remove soil about 1 cm below the main rhizome and we worked
diligently. The plant we examined showed four apparently dormant underground shoots,
one adjacent and distil to the stem of each current aerial stem. The subterranean shoots
were turgid, although the current years growth was already withering. These shoots

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ranged from 1.8 cm to 2.5 cm long. The entire rhizome was relatively shallow, and
removing the duff layer nearly exposed the structure. Also, we noted that the shoots had
a strong, musty odor, similar to that of the fresh flowers.

Each stem and shoot pair was attached to the distil end of a woody rhizome
branch with numerous stem scars. Each shoot corresponded to an adventitious root
growing down from the ventral side of the rhizome branch. Individual aerial stem scars
along the branch corresponded to individual roots, many of which were apparently
senescent.

Based on the above observations, I hypothesize that this species produces a
dormant bud during the current years growing season. This bud remains inactive through
the winter, but then bolts in April to produce an aerial stem. A the same time, a new bud
is initiated and developed during the photosynthetic period. If my assumptions are
correct, then it would be possible to age plants by counting the number of adventitious
roots or corresponding stem scars. The plant we excavated would, therefore, have been
25 to 30 years old.

These observations have led to a series of questions. Is there a correlation
between stand age and C. fasciculatum age? Is there a correlation between the size and
robustness of individuals and their age? Are large, robust individuals the result of having
large, robust rhizomes? Or, are they correlated with young rhizomes? Or, do plants
increase in size with the increasing age or the rhizome? Do plants diminish in size with
age, or do they increase for a time, then decrease?

However, it may be impossible for us to answer some or all of these questions.
Upon my return to the excavation site in early May of this year, I could find no aerial

stems and inspection of the rhizome revealed a rotting rhizome and dormant buds. We
had thought that we were as careful as possible in our excavation and had returned the
soil and duff to its original position. The woody rhizome and tough adventitious roots
appeared, at the time, to easily withstand our investigation. Fortunately, I had chosen a
population of nearly 125 stems.

This apparent sensitivity to ground disturbance is significant and something we all
must keep in mind when we are planning projects in areas were this species occurs.

Buffer areas established in timber sale areas must be sufficiently large enough so that if a
tree were accidentally to fall in the buffer, it would not fall on the plants then dragged
over the plants. Other types of ground disturbance should probably be avoided given that
the buds for next years growth is largely found in the duff layer.