Recovery of plant communities and soil organic matter pools in sagebrush steppe ecosystem of south central Wyoming

Background/Question/Methods

Semi-arid sagebrush steppe areas of the western U. S. are experiencing intense increases in oil and gas development over the past few decades. Reclamation of oil and gas wells requires knowledge about the long term patterns of natural recovery in this system. Our research addresses the pattern of community and soil organic matter (SOM) recovery following abandonment of wells without reclamation, over nearly a century. We used a chronosequence of 29 well sites that were abandoned during a period that extended from 1918 to 1980, across a broad region that encompassed significant soil variability.  On each of the well sites, we compared sagebrush cover, biomass and herbaceous community composition, and soil organic matter (SOM) characteristics in disturbed and adjacent undisturbed areas. We measured active (microbial), intermediate, and passive pools of soil carbon and nitrogen at multiple increments to a 60 cm depth.

Results/Conclusions

Sagebrush cover increased  since the disturbance (R² =0.56, p=0.008) on soils with a sandy texture, while sagebrush cover on more fine-textured soils did not show any trend of change with time.  Only the active fraction of SOM showed significant recovery (less difference between control and disturbed), and only in the surface soils, with intermediate and passive pools not increasing over this time period.  Our results suggest that vegetation recovery may occur over ninety years following abandonment without reclamation, but only on sandy soils. Soil organic matter recovery in the absence of reclamation requires a longer time in these semi-arid shrublands, and the rates are likely highly dependent on site specific practices.