Alnus maritima ssp. oklahomensis Performance in Non-Irrigated Landscapes in the Intermountain West

Alnus maritima (Marsh.) Muhl. ex Nutt. ssp. oklahomensis Schrader & Graves has potential for ornamental use in the Intermountain West. Because this taxon is native to low-elevation wetlands, we sought to determine its response to the dry soils and climate of northern Utah. Although seeds sown directly at three non-irrigated sites in northern Utah either did not germinate or germinated and died, seeds planted in a greenhouse in soils from the three sites did germinate and survive. Hardened plants grown from these seeds and installed at the same three sites overwintered, broke bud and leafed out, but none survived longer than four weeks after bud break without irrigation. Ratings of progression of bud break were greatest (3.5 to 3.8 out of 5), and leaf scorch least (16.0 to 16.7%), in areas with either low light or wet soils. Plants from the same crop left in their containers on an irrigated gravel pad under partial shade showed no signs of stress. Our results suggest that A. maritima ssp. oklahomensis cannot survive under non-irrigated outdoor conditions in Intermountain West landscapes and may require irrigation and protection from sun and wind for optimal performance.

Nodulation and Growth of Alnus nitida and Alnus maritima Inoculated with Species-specific and Nonspecific Frankia

Actinorhizal plants form N2-fixing symbioses with soil-borne bacteria of the genus Frankia. Potential exists for development of sustainable, actinorhizal nursery crops that obtain most of their required N through N2 fixation, but information on host-symbiont specificity, presence of compatible Frankia in soils, and techniques to inoculate during plant production is lacking. Our objectives were to determine the effect of inoculum type and source and the effect of supplemental N on nodulation, growth, and N content of two actinorhizal species, Alnus nitida (Spach) Endl. and Alnus maritima (Marsh.) Muhl. ex Nutt. Plants of both species were subjected to one of four inoculum treatments (two crushed-nodule inocula: species-specific and cross inoculation, and two soil inocula: soil collected beneath native Alnus rubra Bong. in Washington state and native prairie soil from Iowa), were supplied fertilizer with or without N, and were grown in a greenhouse for 22 weeks. Inoculated plants nodulated, grew larger and faster, and accrued greater N content than uninoculated controls in both fertilizer treatments. Plants that received species-specific inoculum grew larger, acquired more dry weight from symbioses, and accumulated higher N content than cross-inoculated plants. Plants of A. nitida inoculated with soil from Washington state grew larger and accumulated more dry weight from symbioses than those inoculated with prairie soil, but A. maritima grew similarly with soil inoculum from both sources. Our results demonstrate that A. nitida and A. maritima can benefit from N2-fixing symbiosis during production and that potential exists for development of superior inocula and inoculation techniques.