Restoration of abandoned agricultural fields in Great Basin salt desert ecosystems is critical for improved wildlife and water resources. Soil conditions are highly altered in these sites, and successful restoration will depend on identifying plants that can grow in former agricultural soils. Salt desert plants must survive in environments with extreme temperatures, aridity, and low productivity, and soil properties can strongly influence how these conditions affect plant establishment and survival. We hypothesized that seedling establishment in old fields could be predicted by describing edaphic characteristics that are related to shrub abundance and composition in native sites. We described plant-soil relationships at a restored field and 15 adjacent native shrubland sites in the Walker River Basin, Nevada. We assessed vegetation characteristics as well as physical, and chemical soil characteristics. Success of restoration treatments (irrigation, seeding year, co-seeding with grasses, weed control) was measured by quantifying establishment of four shrub species, and we measured soil characteristics in areas of high and low seedling success. Non-metric multidimensional scaling and hierarchical variance partitioning were used to determine associations between edaphic characteristics and native shrub composition and cover, and the relative importance of soil factors and restoration strategies on shrub seedling establishment.
Results/Conclusions
Shrub community characteristics were strongly related to soil environment in native areas. Both soil chemical (R2=0.87) and physical properties (R2=0.76) were related to total native shrub cover, and several soil characteristics were correlated with gradients in community structure (EC, P, %N, %C, δ13C, %sand, %silt). Counter to our hypothesis, soil properties were less explanatory (R2=0.32; R2=0.21, respectively) for total shrub seedling establishment in the old field, where more variance was explained by restoration treatments (R2=0.41). Gradients identified from the native ordination were not predictive of establishment in the old field. Results suggest that soil physical and chemical characteristics, while important in long-term development of shrub communities, are less important than other factors, which may include water availability and weed competition, for seedling establishment. The association of shrubs with edaphic conditions in native sites may be a consequence of established plants influencing their environment. There may be a decoupling of plant-soil relationships during the earliest stages of plant establishment, with biogeochemical feedbacks becoming more developed and more strongly influencing survival with age. Native community structure and long-term restoration outcomes therefore may result from relationships that emerge throughout plant life cycles.