Seed longevity and seeding strategies affect sagebrush revegetation

Abstract

Three hypotheses were tested relating to Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) revegetation on coal-mined land in Wyoming: (1) that fourwing saltbush (Atriplex canescens (Pursh) Nutt.) seeded > 2.2 kg pure live seed (pls)/ha would exclude sagebrush, (2) the contrasting view that the saltbush, as a "pioneer plant", facilitated sagebrush stand development [by promoting beneficial soil microbiological activity], and (3) that sagebrush stand development would be greater on fresh-stripped, than on stored, topsoil. The hypotheses were tested by comparing stand development on field plots: 1) seeded to sagebrush in February 1992, and March 1993; 2) fallowed in 1992, and sagebrush seeded in March 1993; 3) seeded to 'Wytana' fourwing saltbush in November, 1991, with sagebrush over-seeded in March, 1993, and; 4) no seeding. The experimental design was a randomized complete block with split plots of stored and fresh-stripped topsoil and with 3 replications. New sagebrush were detected annually through 4 post-seeding spring counts. Seed efficiency was affected by seeding strategy, but efficiency, density, and height were not affected by topsoil source. Proximity to saltbush did not affect sagebrush heights. The results imply that a 'Wytana' density less than or equal to 5 seedlings/m2 is unlikely to deter or promote development of the sagebrush stand, but it will significantly increase total-shrub seed efficiency and density. Seeding strategies, particularly pre-sowing fallow and mixed-species seedings, will likely have a greater influence on sagebrush revegetation than will topsoil source when topsoils are handled as they were in this study.