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Biological soil crusts (biocrusts) typically cover open spaces on soils in arid and semi-arid regions globally. Biocrusts can have positive, negative, or neutral effects on vascular plant germination. We are conducting complimentary experiments (field and semi-controlled environment) to determine if grass seed morphology (e.g., size, shape, mass and appendages) interacts with biocrust characteristics (e.g., species composition, microtopography, and integrity) to differentially affect the germination and establishment of native and non-native grasses. Our experiments are being conducted on the Colorado Plateau, where biocrusts are pinnacled, and in the Sonoran Desert, where biocrusts are comparatively smoother. Standardizing for seed viability, germination/emergence of warm-season grasses in the Sonoran Desert show higher mean (� SE) emergence among seeds placed in fissures of biocrusts or soil stabilizing polyacrylamide gel (PAM) crusts (53% � 3) compared to seeds placed on the surface of intact crusts (22% � 1). Fissure-placement effects may be biotic, abiotic, or a combination. Emergence was also significantly higher on broken PAM crusts and biocrusts (34% � 2) compared to intact crusts. Cool-season grasses in the Sonoran Desert show similar trends. Autumn establishment trials on the Colorado Plateau show that cheatgrass was more likely to establish (mean � SE) on bare soil and PAM crusts (18% � 2) when compared to cyanobacteria or lichen biocrusts (10% � 1). Cheatgrass was also more likely to establish in disturbed PAM crusts and biocrusts (18% � 2) compared to intact crusts (7% � 1). Experiments with seed awns intact and removed are being conducted to determine the effect of appendages. Manipulation of seed appendages is part of our goal to understand if there are seed characteristics that might predict which grasses are more likely to establish on biocrusts and if those characteristics differ between native and non-native grasses.