Emergence and early survival of early versus late seral species in Great Basin restoration in two different soil types

Authors: USELMAN, SHAUNA - University Of Nevada; Snyder, Keirith; LEGER, ELIZABETH - University Of Nevada; Duke, Sara

Submitted to: Applied Vegetation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2015
Publication Date: 6/8/2015
Citation: Uselman, S.M., Snyder, K.A., Leger, E.A., Duke, S.E. 2015. Emergence and early survival of early versus late seral species in Great Basin restoration in two different soil types. Applied Vegetation Science. doi: 10.1111/avsc.12175.

Interpretive Summary: The use of native annual and early seral species in Great Basin rangeland reseeding efforts may improve restoration/rehabilitation success by increasing ecological resistance to invasion by exotic annual grasses and by facilitating succession to desirable late seral vegetation. Early seral species may be similar to exotic annual grasses in growth rates and resource acquisition strategies. As a result, ecological theory predicts that early serals would compete more strongly against invasive like cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae). Because the invasion and success of exotic grasses appears to be associated with soil type, competitive interactions between exotic and native plants may also depend on soil type. In this study, we used a common garden approach to evaluate the performance of two exotic annual grasses (either cheatgrass or medusahead) and mixtures of native species growing in two soil types of contrasting texture (sandy loam and clay loam). Performance of an early seral seed mix (native annual forbs, early seral grasses and shrubs) was compared with that of a late seral seed mix representative of species commonly used in restoration. We found that the early serals generally outperformed the late serals when growing with exotic annual grasses, both in terms of seedling emergence and early survival, though results differed among functional groups (i.e., native grasses, forbs, and shrubs) and soil types. Performance of the native grasses was generally higher than the performance of native forbs and shrubs. During early life stages, the presence of native species did not have a suppressive effect on the exotics. In terms of soil preference, cheatgrass performance was higher in sandy loam compared to clay loam, but performance of medusahead was high on both soil types. The response of native plants to soil type depended on whether natives were growing with exotics. Given their generally higher performance, the early seral natives may have a greater chance of persisting in the presence of cheatgrass or medusahead in comparison to the late seral natives. Success of seeded natives at the seedling stage is likely critical in determining the eventual success of native reseeding efforts. Our findings suggest that use of early serals in reseeding efforts may result in greater density of natives in communities where exotics are present, though additional studies will be needed to assess whether these species are able to persist in the long-term. Differences in native performance on the two different soil types when growing with exotics suggest that use of early serals in restoration seedings may result in greater success in more coarse-textured soils, particularly when native grasses comprise a large proportion of the native seed mix. The strong performance of medusahead in both soil types underscores the need for greater efforts to prevent its further spread in the Great Basin.

Technical Abstract: Use of early seral species in Great Basin rangeland reseedings efforts may increase invasion resistance, facilitate succession, and improve restoration/rehabilitation success. Because they occupy a similar ecological niche, theory predicts early seral species would compete more strongly against exotic annual grasses. We compared seedling emergence and early survival of two native seed mixes when growing with Bromus tectorum or Taenatherum caput-medusae in soils of contrasting texture (sandy loam and clay loam). Natives were also seeded without exotics. Performance of an early seral mix (annual forbs, early seral grasses and shrubs) was compared with that of a late seral mix representative of species commonly used in restoration. Early seral species generally outperformed late seral species when growing with exotics, for emergence probabilities, survival probabilities, and earlier emergence timing, though results differed among functional groups and soil types. In contrast, survival probabilities did not differ between the early and late seral mixes when growing without exotic annual grasses. Within each seed mix, native grasses exhibited the highest emergence probabilities of the functional groups. Natives did not suppress exotics in early life stages. Emergence of all native functional groups and survival of native grasses was generally higher on sandy loam when growing with exotics, indicating that plant-plant interactions between natives and exotics affected response to soil type. Early seral species were better able to persist with exotics during early life stages, particularly native grasses in sandy loam, suggesting they may endure within native-exotic communities and help facilitate succession to later seral species.