Arid and semi-arid systems are spatially heterogeneous where islands of fertility, hotspots of germination and establishment, are interspersed with neighboring microenvironments that may be less suitable for establishment. In the Intermountain West, current revegetation techniques typically focus on post-disturbance landscapes with little to no woody plant cover and have notoriously low rates of establishment of desirable species, especially in lower elevation, drier, and warmer areas. Failing to focus restoration efforts of understory plants into stands of Wyoming big sagebrush represents a missed opportunity to capitalize on island of fertility effects of intact canopies. Empirical studies of islands of fertility focus on spatial binaries: canopy and interspace. However, island of fertility effects may not be binary and may attenuate from the canopy to the interspace differently depending on the conditions of the site. We tested how establishment and survival of herbaceous plants varied with distance from sagebrush canopy to understand how to utilize island of fertility effects to increase understory forb and grass cover before disturbance, rather than after. We also tested if the influence of sagebrush canopy changed across the landscape with different soil moisture-temperature regimes. We planted seedlings of two grass species, Elymus elymoides and Pseudoroegneria spicata, and two forb species, Sphaeralcea munroana and Achillea millefolium. Seedlings were planted at varying distances from sagebrush canopies in random directions at 6 sites of different soil moisture and temperature regimes (warm-dry and cool-moist) across the Intermountain West.
Preliminary Results/Conclusions
Results were site and species specific, but generally, survival was higher toward the interspaces for most species at most sites, regardless of soil moisture temperature regime. Survival in the first year, depending on site and distance from sagebrush, ranged from 0.0-63.9% for P. spicata, 0.0-38.1% for E. elymoides, 0.0-63.6% for A. millefolium, and 0-82.6% for S. munroana. Better understanding the spatial distribution of island of fertility effects will allow highly targeted planting of seedlings into areas of sagebrush stands that could increase establishment and survival rates in restoration projects.