Do Abiotic Treatments Promote Ecological Recovery?

Abstract

Restoring warm desert ecosystems is challenging due to limited microhabitat availability, propagule scarcity, and increas-ingly variable climate. We evaluated the effectiveness of simple, on-site abiotic restoration techniques in promoting plant recruitment along a decommissioned road in the Mojave Desert using two complementary approaches: (1) a retrospective assessment of a management-scale restoration, measured at two scales, that employed pitting and vertical mulch with litter, and (2) a microsite-scale field experiment testing soil decompaction, vertical mulch, and litter transfer. In the management restoration, surface manipulations created microsites that supported natural colonization by native shrubs and annuals. Shrub seedling cover and richness were highest in pitted microsites, whereas recruitment remained minimal where vertical mulch was added. Native annual cover was lower in restoration than undisturbed reference microsites, although richness increased across microsite types over time. In the field experiment, shrub seedling cover, soil moisture, and soil compaction differed across treatments. Loosening soils supported higher cover and moisture and exhibited lower compaction, whereas adding vertical mulch to decompaction treatments did not correspond with higher recruitment. Litter transfer was associated with modest but potentially meaningful differences, including higher Larrea tridentata recruitment in the management restoration and greater soil stability in experimental microsites that included both decompaction and vertical mulch. Across both studies, shrub microsites did not consistently function as nurse plants, indicating limited canopy-mediated facilitation at this site. Together, results indicate that low-cost abiotic interventions—depressions supplemented with litter—can improve microsite conditions and increase the likelihood of plant establishment under contemporary desert conditions.