|Abstract or Summary
- Four aspects of the ecology of members of the Monotropoideae (achiorophyllous
Ericaceae, referred to here as "monotropes") are presented: (1) a clarified conceptualization
of monotrope nutrition based on a detailed literature review, (2) the relationship of
monotrope populations to the plant communities of Limpy Rock RNA, (3) a test of
Vreeland's hypothesis concerning the influence of overstory trees on the number of
Sarcodes sanguinea plants in a forest stand, (4) the population dynamics of the
northernmost known occurrence of Sarcodes san guinea.
A literature survey provides insight into the development of concepts concerning the
nutritional mode of monotropes. The experimental evidence reviewed showed that the
fungi involved have little saprobic ability but are ectomycorrhizal with autotrophic plants.
Hence, the concept "epiparasite" can be used to describe an indirect relationship in the life
history of monotropes. With consideration of the operational environment of monotropes,
however, it can be concluded that the term "epiparasite" is not appropriately used in the
context of the nutritional mode of monotropes. Members of the Monotropoideae can be
viewed as parasites of their mycorrhizal fungi. Some evidence showed growth of the fungi
was stimulated by the presence of monotropes. Since the term "parasite" has negative
connotations in general usage, the terms 'obligate mycotroph" and "mycotrophic" may be
preferred when referring to members of the Monotropoideae. "Mycotrophic" could be
strictly applied to only those organisms which depend on fungi for energy; however, the
term has long been used in a broad sense interchangeably with "mycorrhizal."
Limpy Rock Research Natural Area is located in the south central portion of the
Cascade Mountains in Oregon. The 751 ha (1879 ac.) tract encompasses most of the drainage of Dog Creek. Elevation ranges from 525 to 1305 m (1750 - 4350 ft.). The high
species diversity of the Limpy Rock area and local concentration of all eight western
monotrope species, provided excellent and possibly unique research opportunities.
Coniferous forest vegetation was classified by TWINS PAN into six community
types: Pseudotsuga menziesiilAcer circinatum (PSME/ACCI), Pseudotsuga
menziesiilCornus nuttalliilBerberis nervosa (PS ME/CONU/B ENE),
Pseudotsuga rnenziesii-Arbutus menziesii/Gaultheria shallon-Berberis
nervosa/Pleridiurn aquilinum (PS ME-A RME/GAS H- BENE/PTAQ), Pseudotsuga
menziesii-Calocedrus decurrens/Gaultheria shallo n-Berberis nervosa (PS MECADE/
GAS H-B ENE), Pseudotsuga menziesii-Calocedrus decurrens/Gauliheria
shallon-Berberis nervosa (PS ME-PILA/GAS H-B ENE), Pseudotsuga menziesii-
Abies concolor/Berberis nervosal Xerophyllurn tenax (PSME-ABCO/
BENE/XETE). Community types were related to several general environmental measures
by detrended correspondence analysis and correlation analysis.
Allotropa virgata is strongly preferential to plots at the dryer end of the moisture
gradient. Monotropa hypopithys shows a preference for higher elevation and cooler types.
Pterospora andromedea was not found in any plots but was noted to be widespread
throughout the RNA. Hernitoines con gestwn, Monotropa uniflora, Fityopus californica,
and Pleuricosporafiinbrioiata were largely restricted to dryer types. No monotropes were
found in plots of the PSME/CONU/BENE or PSME-ARME/GASH-BENE/PTAQ
Vreeland's (1980) hypothesis concerning predicting the number of Sarcodes in a
stand was reviewed and discussed. In particular, his "Influence Factor" was tested with a
data base of over 2000 measurements. The results show his hypothesis to be invalid.
Population monitoring of the northernmost known population of Sarcodes
sanguinea showed that flowering of individual plants in subsequent years was low in
frequency. Despite the low rate of flowering recurrence, population levels were relatively
stable over the five years of monitoring.