COS 91-2 - Ecosystem service tradeoffs in a highly degraded semi-arid grassland restoration

Background/Question/Methods

Domestic livestock grazing provides ecosystem services to support human livelihoods around the globe. However, historic and current livestock overgrazing is a major degradation pathway in dry rangeland ecosystems. Degradation can trigger a shift to an alternative stable state, which is often accompanied by a reduction or change in the portfolio of ecosystem services provided by the land. Decisions regarding restoration and management of degraded land are challenged with how to maximize ecosystem services under a changing climate. In this study, we evaluate restoration strategies to reduce soil loss and increase native vegetation while maintaining cattle grazing. This study was conducted over four years at a semiarid grassland in SE Utah that had been converted to degraded alternative stable state. We applied three restoration treatments: 1) restoration of the seedbank by drill seeding native seed mix, 2) stabilization of soils with artificial barriers (“ConMods”) plus hand seeding, 3) drillseeding treatment plus application of an organic soil stabilizer (psyllium) in combination with inoculation of biological soil crusts, and compared them to 4) untreated controls. Half of the treatment plots were rested from grazing for the entire experiment. Cattle were reintroduced to half of the restoration treatment plots after a two-year rest period.

Results/Conclusions

We found that ConMods were initially effective at reducing wind erosion but this effect disappeared over time. Soil stability declined over the experiment but the psyllium plus biocrust treatment significantly increased stability compared to other treatments. None of the treatments were effective at establishing native vegetation, and changes in total cover were driven by climate and not restoration treatments. Reintroducing cattle grazing after a two-year rest period reduced total plant density the year of grazing. One year after grazing, in an extremely dry year, the grazed plots had significantly increased total cover primarily driven by non-seeded, weedy or invasive species rather than native species. There was not a large tradeoff in soil stability associated with grazing. Overall, no restoration treatments were able to move the degraded land into a restored stable state. Under a changing climate, strategies that manage for ecosystem services and functions, rather than strategies that restore to a previous intact state, are likely to be most successful.