Surface mineral soil and foliage associated with Chamaecyparislawsoniana (A. Murr.) Parl. and Thujaplicata Donn ex D. Don were sampled at six sites in southwestern Oregon. Total soil nitrogen concentrations ranged from 0.08 to 0.37%. Percentage exchangeable concentrations of other soil nutrients were 0.0002–0.0020 P, 0.014–0.224 Ca, 0.002–0.018 K, and 0.002–0.023 Mg. Foliage of Chamaecyparis contained 0.9–1.9% N, 0.11–0.23% P, 0.8–1.9% Ca, 0.67–1.20% K, and 0.11–0.26% Mg. Foliage of Thuja contained 0.9–1.6% N, 0.12–0.24% P, 1.1–2.0% Ca, 0.52–0.95% K, and 0.06–0.23% Mg. Overall, foliage of Chamaecyparis contained significantly higher concentrations of K, and tended to have lower Ca:Mg ratios than that of Thuja. Concentrations of soil nutrients showed no obvious relation to species occurrence on a study-wide basis. Within sites where the two species grew together, however, Thuja was associated with higher soil Ca:Mg ratios and foliar Ca, and Chamaecyparis was associated with higher levels of soil K and foliar N. Foliar nutrient concentrations showed little relation to concentrations in soil, although low soil Ca, P, and Mg concentrations were reflected in foliage at some sites. Soils in the study area have higher Ca:Mg ratios and more available N than soils over much of Chamaecyparis' range. Given the apparent nutritional requirements of Thuja, it seems unlikely that it will significantly replace Chamaecyparis killed by root rot.
Isozyme analysis of the rare Oenothera wolfii (Wolf s evening primrose) and the garden escape, O. glazioviana, indicates that hybridization between these species may be more widespread than morphological evidence indicates. Although both species contained low amounts of genetic variation, unique alleles were identified in both taxa. Analysis of 22 populations, including pure populations of each species, identified eight populations as containing putative hybrid individuals. Four of these putative hybrid populations were considered pure O. wolfii based on morphological analysis. This study confirms that the native O. wolfii may be at risk not only from habitat destruction, but potentially from genetic swamping where it co-occurs with O. glazioviana. These results can be used as baseline information for future genetic monitoring efforts.
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