Author
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Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/13/2012 Publication Date: 8/29/2012 Citation: Boyd, C.S., Davies, K.W. 2012. Differential seedling performance and environmental correlates in shrub canopy vs interspace microsites. Journal of Arid Environments. 87:50-57. Interpretive Summary: Micro-spatial variation in soil environmental properties between interspace and under shrub canopy locations can affect demographics and success of seeded perennial grasses. We investigated the influence of sagebrush on 1) soil properties following fire, 2) establishment of seeded perennial grasses, and we then 3) modeled performance of seeded grasses as a function of shrub-induced variability in soil environmental properties. We found that 1) shrubs influenced the values of 6 out of 24 soil variables, 2) tiller production and leaf area were over twice as high in under-canopy (vs. interspace) locations, and 3) shrub-induced variation in soil color and temperature explained up to 32% of the variation in seedling performance indices. Our results suggest that shrubs play an important role in performance of seeded perennial grasses post-fire, and that soil variables, particularly soil color, could be manipulated to increase success of seeded perennial grasses. Technical Abstract: Shrubs in semi-arid ecosystems promote micro-environmental variation in a variety of soil properties. We compared post-fire seeding success and soil variables between shrub (“under-canopy”) and interspace locations for hand-seeded bluebunch wheatgrass (Pseudoroegneria spicata) and crested wheatgrass (Agropyron cristatum) in Wyoming big sagebrush (Artemisia tridentata) plant communities in southeast Oregon, U.S.A. We burned 5, 20 x 20 m sites in October, 2009 and established paired under-canopy and interspace micro-transects. Transects were seeded to bluebunch wheatgrass (193 seeds/m) or crested wheatgrass (177 seeds/m). We monitored seedling density in 2010, and measured soil-related environmental variables. Seedling density was 69% higher for crested wheatgrass and 75% higher for interspace locations. Decreased density in under-canopy was associated with wind erosion of seeds. Tiller and leaf area production were over twice as high (p < 0.05) in under-canopy locations. Six of 24 soil variables differed (p < 0.10) between locations. These six variables, particularly soil color and soil temperature, explained 19 - 32% of variation in seedling performance. Shrub effects on seeding success are complex and interact with abiotic disturbances, but patterns of increased seedling performance in under-canopy locations and their relationships to soil variables may suggest tactics for increasing success of restoration practices. |
