Seed dormancy, soil type and protective shelters influence seedling emergence at Shark Bay, Western Australia: Insight into global dryland revegetation

Abstract

Seedling emergence is a major constraint on dryland revegetation success. In this study, we investigated seedling emergence of six framework shrub species as influenced by seed treatment, soil type and protective shelters using a large field trial in arid Western Australia. We observed the main effects of seed treatment and soil type to account for the majority of the variation in emergence. For species that exhibit pronounced dormancy, we found emergence of dormancy-alleviated or treated (T) seed to be significantly greater than dormant or untreated (UT) seed, with responses varying across species (e.g. 41 times greater for Acacia ligulata Benth., and 10 times greater for Stylobasium spathulatum Desf.). For shallowly or nondormant species like Senna glutinosa (DC) Randall, UT seed emergence was slightly greater than for T seed. Compared to subsoil, topsoil was more receptive to infiltration (3.44 vs. 0.38 mm/min), and less prone to compaction (1.24 vs. 1.67 g/cm3) and crusting (0.6 vs. 1.3 kg/cm2); however, subsoil had greater moisture retention. Shelters failed to benefit soil moisture retention in either soil type, but enhanced emergence for most species. This study provides insight into how various cost-effective treatments can be utilized to manipulate seed dormancy to optimize seedling emergence, the intrinsic value of topsoil as a superior growth medium and the benefit of novel, low-cost shelters for enhancing seedling emergence. In arid environments, sowing T seed in combination with UT seed increases the likelihood of capitalizing on inherently variable precipitation events.