Native seedling establishment in biocrust-areas of a salt desert shrubland varies by species and season of planting

Authors: MERRAN, OWEN - UTAH STATE UNIVERSITY; VEBLEN, KARI - UTAH STATE UNIVERSITY; BOETTINGER, JANIS - UTAH STATE UNIVERSITY; KOUTZOUKIS, SOFIA - UTAH STATE UNIVERSITY; Monaco, Thomas

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: n drylands, low plant productivity and seedling recruitment present considerable challenges to restoration efforts focused on reestablishing native species. Remnant biological soil crusts (biocrusts) in salt-desert shrublands of the western U.S. may provide favorable conditions for seedlings of native species due to increased water and nutrient availability and reduced abundance of exotic species. Here we investigated the effects of biocrust level of development on seedling establishment and survival of native plant species in a salt desert shrubland in southeastern Idaho, USA. Plant species included three native grasses (Indian ricegrass [Achnatherum hymenoides], bottlebrush squirreltail [Elymus elymoides], basin wildrye [Leymus cinereus]) and one native forb (gooseberryleaf globemallow [Sphaeralcea grossulariifolia]). Species were broadcast-seeded and transplanted as seedlings into microsites characterized by high vs. low biocrust level of development in two consecutive years, and establishment and survival were monitored =2 years for each sowing/planting year (Year 1 = low precipitation, Year 2 = high precipitation). Almost no seedlings were recruited by broadcast seeding regardless of year or biocrust level of development, likely due to unfavorable environmental conditions and inadequate seed bed conditions. In contrast, survival of transplants was high to moderate depending on planting season and year. First-year survival of fall-transplanted seedlings during the high precipitation year was high (60.6 ± 16.4%) regardless of biocrust level of development, and survival was notably greater for L. cinereus and E. elymoides than other species, even into the second year. In contrast, over-summer (<1 year) survival of spring-transplanted seedlings during the low-precipitation year was significantly greater in high vs. low biocrust level of development microsites (32.5 ± 7.5% vs. 9.6 ± 3.8%, respectively), suggesting crust cover ameliorated moisture limitation. Greater transplant survival for A. hymenoides and E. elymoides for spring- and fall-planted cohorts, respectively, may be related to differences in drought tolerance and/or successional status of these grasses. Overall, our results indicate that transplanting seedlings, especially during favorable precipitation years and in high-biocrust level of development microsites, offers a promising strategy for restoring native species in drylands that are notoriously difficult to restore with seeding alone.

Technical Abstract: Globally, dryland restoration is difficult due to aridity, edaphic constraints on plant growth, and generally low resilience to environmental stresses. Low productivity and seedling recruitment of salt desert shrublands in the western U.S. present a considerable challenge to restoration efforts focused on reestablishing native species and reducing exotic annual species. However, sites with remnant biological soil crusts (biocrusts) may provide favorable conditions for seedlings of native species due to increased water and nutrient availability and reduced abundance of exotic species. Here we investigated the effects of biocrust development on seedling establishment and survival of native plant species in a salt desert shrubland in southeastern Idaho, USA. Plant species included three native grasses (Indian ricegrass [Achnatherum hymenoides], bottlebrush squirreltail [Elymus elymoides], basin wildrye [Leymus cinereus]) and one native forb (gooseberryleaf globemallow [Sphaeralcea grossulariifolia]). Species were broadcast-seeded and transplanted as seedlings into microsites characterized by high vs. low biocrust development in two consecutive years, and establishment and survival were monitored =2 years for each sowing/planting year (Year 1 = low precipitation, Year 2 = high precipitation). Almost no seedlings were recruited by broadcast seeding regardless of year or biocrust level of development, likely due to unfavorable environmental conditions and inadequate seed bed conditions. In contrast, survival of transplants was high to moderate depending on planting season and year, suggesting that limitations to seeding were overcome by transplants. First-year survival of fall-transplanted seedlings during the high precipitation year was very high (60.6 ± 16.4%) regardless of biological soil crust cover, and survival was notably greater for L. cinereus and E. elymoides than other species, even into the second year. In contrast, over-summer (<1 year) survival of spring-transplanted seedlings during the low-precipitation year was significantly greater in high vs. low biological soil crust cover microsites (32.5 ± 7.5% vs. 9.6 ± 3.8%, respectively), suggesting crust cover ameliorated moisture limitation. Greater transplant survival for A. hymenoides and E. elymoides for spring- and fall-planted cohorts, respectively, may be related to differences in drought tolerance and/or successional status of these grasses. Overall, our results indicate that transplanting seedlings, especially during favorable precipitation years and in high-biocrust microsites, can mitigate moisture limitation and offers a viable strategy for restoring native species in drylands that are notoriously difficult to restore with seeding alone.