We estimated aboveground and belowground net primary productivity (NPP) for two reaches of a montane riparian ecosystem in the eastern Sierra Nevada Mountains of California with differing stream flow regimes resulting from varying degrees of stream flow diversion for hydroelectric power generation. Total understory productivity (herbaceous and shrub) was 2.5 times higher (P < 0.001) at the high-flow site than at the low-flow site (22.4 and 8.9 g C m⁻² yr⁻¹, respectively). Annual litterfall was also higher (P = 0.03) at the high-flow (235 g C m⁻² yr⁻¹) than at the low-flow site (180 g C m⁻² yr⁻¹). However, tree and total aboveground NPP, as well as annual soil respiration and belowground NPP, were all statistically similar between sites. Furthermore, total (above- plus below-ground) NPP was statistically similar between sites (903 and 643 g C m⁻² yr⁻¹ for the high- and low-flow sites, respectively). These productivity estimates are, to our knowledge, the first ever reported for a western montane riparian ecosystem. Our results suggest that NPP of montane riparian ecosystems located along gaining stream reaches is only loosely coupled to stream flow, and understory aboveground NPP may be the most sensitive productivity measure to altered stream flow.

We tested the host efficiency of an abundant non-native annual grass Parapholis incurva for the rare and endangered hemiparasite Cordylanthus maritimus subsp. maritimus. Flower production in C. m. maritimus was significantly less when P. incurva was the sole host (average 1 flower), than when the native perennial grass host, Distichlis spicata, was present (average 13 flowers). When C. m. maritimus was prevented from parasitizing either the native or non-native host, flower production results were similar to that of the non-native host (average 1 flower). Formation of haustoria did not differ between host identity treatments (average 270 haustoria per pot), but was significantly less in treatments that did not allow root contact between the host and hemiparasite (average 10 haustoria per pot). The “pseudo-host” effect of the non-native annual grass could result in high energetic cost to the endangered hemiparasite. Management decision-makers should factor in the costs of non-competitive mechanisms when prioritizing non-native species removal in areas with rare hemiparasites.

We used Random Amplified Polymorphic DNA (RAPD) to investigate genetic variation in eight populations of the vernal pool endemic Navarretia leucocephala Benth. in eastern Washington. Five of the populations were subspecies minima, collected in Spokane County. The other three populations were subspecies diffusa, a recently described taxon known only from adjacent Lincoln County in eastern Washington. We also sampled a nearby vernal pool population of N. intertexta (Benth.) Hook., a closely related species whose range overlaps with N. leucocephala. Distances among the sampled pools ranged from a few tens of meters to 80 km. The populations differed in their levels of genetic variation, with proportions of polymorphic loci ranging from 10% to 55% and mean gene diversities from 0.05 to 0.30. Analysis of Molecular Variance (AMOVA) among the eight N. leucocephala populations showed significant spatial structuring, with 52% of the observed genetic variation due to differences between the Spokane County and Lincoln County populations. Within each county, 10% − 34% of the genetic variation was due to differences among populations. Estimates of Φ_ST indicated significant population differentiation among all populations of N. leucocephala (Φ_ST = 0.65), but the degree of differentiation varied with interpopulation distance. Populations 35–250 m apart were generally not differentiated. At a distance of 1100–1800 m, some populations showed significant differentiation and others did not. Populations 80 km apart were significantly differentiated. On a distance-based phenogram, N. intertexta separated clearly from the N. leucocephala populations, which also grouped by subspecies, suggesting that the morphological features used to differentiate the taxa are paralleled by genetic differences.

Lupinus polyphyllus and L. wyethii are closely related members of a species complex widely distributed in western North America. Principal components analysis of morphological characters showed that these two taxa intergrade extensively, with many intermediate forms occurring. DNA sequences of the internal transcribed spacer (ITS) region in 28 individuals were variable at five base positions, both within and between taxa; some of these sequences have also been reported from related species. Molecular variation showed a geographic pattern but did not strongly reflect morphological differences. Morphological features that have been used to separate species in this group may primarily reflect local adaptation rather than underlying phylogenetic divergence. The lack of clear differentiation between these two lupines suggests that they are best treated as varieties of a single species, L. polyphyllus.

Tree-ring data from Chamaecyparis lawsoniana (A. Murr.) Parl. (Port Orford cedar; Cupressaceae) were used to create a standardized chronology, assess the local, limiting factors on radial growth, and investigate the extent of a unique climatic event. We produced a 580-year tree-ring chronology (A.D. 1420 to 2000) from a large number of cedars (n = 1537) sampled in one 37 km² area in the Siskiyou Mountains of southwestern Oregon and northern California. This chronology represents an area with few long-term climatic studies and a species with no dendrochronological data. We found radial growth to be positively correlated with year-round soil moisture conditions, specifically with cool, wet conditions in summer and warm, wet conditions in winter. The year 1739 stood out as a climatic pointer year with the smallest ring width index for the entire chronology and anatomically distinctive damage to the latewood of 1738 and earlywood of 1739. This pointer year was consistently identified across watersheds, topographic position (e.g., streamside, hillslope), and the range of the cedar, corresponding to an extreme, single-year drought occurring throughout the Pacific Northwest.