An investigation into the ecology and distribution of Kalmiopsis leachiana (Hend.) Rehder Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/c534fs202

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  • Ecological factors associated with the relictual distribution of the endemic shrub Kalmiopsis leachiana (Ericaceae) were investigated. A prostrate evergreen species with small coriaceous leaves, K. leachiana is restricted to two disjunct populations in the Siskiyou Mountains and southern Cascade Mountains of southwestern Oregon, USA. Exact distributions of individual populations were mapped and were related to soils, geology, climate, and fire history using these factors to define in part this species' ecological range. Further investigation involved intensive sampling of associated vegetation, pressure chamber studies, seed germination and seedling growth experiments, and preliminary study of herbivore relationships and the heterostylous breeding system. Associated vegetation of Kalmiopsis populations was sampled using a nested plot technique. Analysis showed there to exist three major vegetation units: (1) low elevation Siskiyou stands (300-600 m), characterized by a conifer, broadleaf sclerophyll tree, evergreen shrub, and herb layer; (2) high elevation Siskiyou stands (900 m), differing from low elevation site by the absence of a broadleaf sclerophyll canopy; and (3) Southern Cascades vegetation, having relatively low species diversity associated with a more dense conifer canopy. In the latter stands, Kalmiopsis is found to grow almost invariably only on exposed, silicified rock outcrops. Soil in the Cascades did not prove to be inhibitory to germination and seedling development. Thus it is suggested that competition for light, water, and nutrients plays an important role in the species distribution and especially in its exclusion from surrounding vegetation of Cascades rock outcrops. In turn loss of the broadleaf sclerophyll canopy at high elevations in the Siskiyous, and related decrease in overstory canopy cover, is correlated with the much greater abundance of Kalmiopsis at high elevations there. The nature of the growth form and morphology of this plant and how they appear to be advantageous for establishment and growth in rocky, competition low microhabitats is discussed. Measurements of internal moisture stress were taken in the Siskiyou Mountains on Kalmiopsis and two sympatric sclerophyllous shrub species. Results of predawn and midday measurements at the height of the drought season indicate that Kalmiopsis undergoes higher stress levels than the other two species do in the same location, and appears to shut its stomata early in the day to avoid high stress buildup. In contrast the two sympatric shrubs appear to be able to remain photosynthesizing longer into the day, and this combined with their ability to handle higher stress, might account for their occurrence at more xeric topographic positions where K. leachiana is not found. Germination and growth experiments on natural soils showed that Kalmiopsis seeds can germinate under low light conditions, are, heat sensitive, and resulting seedlings have relatively slow growth rates. The seedlings' small size and slow growth rates are suggested to account for the low reproductive rate observed in the field and to be a contributing factor in the restricted distribution of the species. Kalmiopsis is distylous, this being the first reported case of heterostyly in the Ericaeae. In addition evidence is given that this morphological adaptation for outcrossing is strengthened by genetic self-incompatibility within and between plants of similar morphological types. Evidence of herbivory was practically absent in all populations. Two seed eating species, a lygaeid bug in the genus Kleidocerys and a species of mite in Trichoribates, were found to be associated with the persistent capsules. These may play an important role in the reproductive output of this plant.
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