Description of vegetation and soil properties in sagebrush steppe following pipeline burial, reclamation, and recovery time

- Sagebrush steppe vegetation and soil patterns are inherently heterogeneous.
- After drastic disturbance, vegetation recovers in a predictable manner.
- Soil properties are not universally homogenized following disturbance.
- Spatial correlation structure of soil and vegetation properties was weak.
- Sagebrush steppe may require in excess of 55 years for recovery.

Sagebrush (Artemisia tridentata Nutt.) steppe displays a high degree of heterogeneity in vegetation structure and in the spatial distribution of soil properties. Sagebrush steppe in south central Wyoming, USA, is experiencing a multitude of surface disturbances that involve vegetation removal and soil mixing. We hypothesized that drastic disturbance associated with pipeline burial would result in homogenization of above- and below-ground properties and that soil variability would be higher in areas with longer recovery time. We established a spatially explicit sampling design (< 15 m scale) on neighboring reclaimed pipelines of different ages (1, 5, 36, and 55 years), and two adjacent undisturbed areas. We used descriptive statistics and Bayesian geostatistical models to quantify and compare the plant community and soil properties (soil moisture, organic carbon concentration, total microbial abundance, and electrical conductivity) across plots. Disturbance initially resulted in uniform cover of weedy plant species; older plots had uniform cover of grasses. Shrub and forb cover was highest in the 55 year old plot, but lower than the undisturbed reference areas. Soil properties in the youngest plots had increased soil moisture and salinity and decreased microbial abundance; these differences were less apparent in the older treatments. Disturbance did not result in universal homogenization of soil properties, and variability did not necessarily increase with recovery age for all properties. At the scale sampled, vegetation and soil properties did not display strong spatial correlation structures. Vegetation and soil properties in the 55 year old plot were most similar to the undisturbed sagebrush steppe, indicating greatest degree of recovery, compared with younger recovery ages.