Long-term legacy effects of cultivation on vegetation and soils in sagebrush ecosystems of the Great Basin

Background/Question/Methods

Cultivation is an exotic disturbance that can create long-term changes (“land-use legacies”) in native vegetation and soils that require decades to centuries to recover. Recovery following cultivation in sagebrush ecosystems of the Great Basin, USA remains largely unexamined even though millions of acres of land were dry farmed in the early 1900s and abandoned by the 1920s. We examined the land-use legacy of cultivation on both vegetation and soils using paired sets of historically dry-farmed land (called “old fields”) and adjacent areas that had never been cultivated (called “adjacent land”). We measured vegetation cover in old field and adjacent land using transects and quadrats. Soil samples were collected from under a sagebrush and in the interspaces between shrubs at randomized locations along transects. Large rocks and organic debris were removed using a 2mm sieve. Soil samples were air- dried, ground with an IKA MK 10 grinder with a 0.05 mesh. Calcium carbonates were removed using a hydrochloric acid wash and then rinsed and oven dried. Total C and N were determined using a LECO TruSpec with a certified soil standard (0.13 % N) for calibration.

Results/Conclusions

Vegetation recovery from cultivation was variable by plant growth form, species, and by ecological site. We found changes in shrub composition in old fields as well as lower overall cover of shrubs. Shrub recovery was different among Artemisia species. Total forb cover was generally lower in old fields, some native forb species had not recovered, while nonnative forb cover was higher. The most common grass species encountered across all ecological sites, Elymus elymoides, had higher cover in old fields. Total C and N were also variable by ecological site, and were generally lower in shrub interspaces compared to under a shrub, which is to be expected. Total N under shrubs in the old fields was significantly lower than under shrubs in adjacent land at only one ecological site. The other two sites had elevated C and N under shrubs. These results suggest that the “islands of fertility” that are known to form under shrubs in these systems can take over a century to recover. It also suggests that the land-use legacy of dry farming remains in vegetation and soils nearly a century after cultivation has ceased. This study has important implications for management and restoration efforts in sagebrush ecosystems.