Cacti in the desert
Desert Restoration

 

California is home to several distinct desert regions, including the Mojave Desert, the Colorado Desert (which is part of the larger Sonoran Desert), and the Great Basin Desert. Each of these regions is characterized by unique plant communities and climates, but they face similar threats including the invasion of nonnative plant species, altered fire regimes, damage from off road vehicles, energy development, and urban expansion [1]. Restoring these diverse desert ecosystems presents significant challenges [2]. The extreme of desert environments makes plant establishment difficult, with water availability being a critical factor in the success of restoration efforts. Additionally, desert species typically exhibit very slow growth rates, meaning they do not recover quickly from disturbances, and successful restoration can take many years or even decades. Soil degradation from historical land use—such as compaction, erosion, salinity, and altered soil biology—further complicates plant establishment. Furthermore, a lack of native plant propagules in the soil seedbank and from nearby remnant vegetation poses a major obstacle. The development and availability of native plant material, including both seeds and nursery stock, are therefore essential to meeting restoration goals in California’s deserts.

Despite these challenges, significant progress has been made to advance techniques for the restoration of these sensitive ecosystems. Transplanting nursery-grown seedlings is the most reliable approach for restoring desert perennials, since germination of seeds in the field is highly variable and dependent on precipitation. Plants should be irrigated if possible and protected from herbivores to ensure survival [3]. Deploying water to restoration sites can be challenging, especially in remote sites, but this can make the difference between success and failure. Several approaches can be used, including manual watering, traditional irrigation systems, or the installation of PVC pipes or buried clay pots to deliver water directly to the rooting zone of transplanted individuals [4]. Transplanting individuals into slight depressions can aid in capturing water from both rainfall and irrigation. Making use of larger rainfall catchments can also substantially improve survival [5]. Outplanting of perennial nurse plants can also facilitate recruitment of herbaceous species through the creation of “fertile islands”, which are fundamental for vegetation establishment in drylands. Similarly, the addition of vertical mulch (e.g., dead branches, brush, or small woody debris) can create favorable microhabitats for native plant establishment. These methods may facilitate weed establishment, however, so ongoing weed management may be required [6]. Seed-based restoration in California's deserts can be effective in some instances, but this approach requires careful planning due to unpredictable precipitation, competition from nonnatives, and seed loss through predation. Timing seeding efforts to coincide with rainfall events is critical, but even then seedlings establishment is prone to failure. Incorporating soil surface treatments and introducing seeds to the site at multiple time points can enhance recruitment [7].

Seed transfer zones based on climate [8] can be useful for guiding the selection of plant material that will perform well at a given site. California’s deserts support threatened and endangered wildlife, such as the Mojave desert tortoise. Native plant palettes can be tailored in order to support habitat for this species and other wildlife such as pollinators [9].

Resources

References

  1. Allen, M. F., Barrows, C. W., Bell, M. D., Jenerette, G. D., Johnson, R. F., & Allen, E. B. (2014). Threats to California’s desert ecosystems. Fremontia, 42, 3-8. PDF
  2. Lovich, J. E., & Bainbridge, D. (1999). Anthropogenic degradation of the southern California desert ecosystem and prospects for natural recovery and restoration. Environmental management, 24, 309-326. PDF
  3. Scoles-Sciulla, S. J., DeFalco, L. A., & Esque, T. C. (2015). Contrasting long-term survival of two outplanted Mojave Desert perennials for post-fire revegetation. Arid Land Research and Management, 29(1), 110-124. https://doi.org/10.1080/15324982.2014.901994
  4. Bainbridge, D. A. (2002). Alternative irrigation systems for arid land restoration. Ecological Restoration, 20(1), 23-30. PDF
  5. Edwards, F. S., Bainbridge, D. A., Zink, T. A., & Allen, M. F. (2000). Rainfall catchments improve survival of container transplants at Mojave Desert site. Ecological Restoration, 18(2), 100-103. PDF
  6. Abella, S. R., & Chiquoine, L. P. (2019). The good with the bad: when ecological restoration facilitates native and non‐native species. Restoration Ecology, 27(2), 343-351. https://doi.org/10.1111/rec.12874
  7. Shryock, D. F., DeFalco, L. A., & Esque, T. C. (2018). Spatial decision‐support tools to guide restoration and seed‐sourcing in the Desert Southwest. Ecosphere, 9(10), e02453. https://doi.org/10.1002/ecs2.2453
  8. Farrell, H.L., Munson, S.M., Butterfield, B.J., Duniway, M.C., Faist, A.M., Gornish, E.S., Havrilla, C.A., Larios, L., Reed, S.C., Rowe, H.I. and Laushman, K.M. (2023) . Soil surface treatments and precipitation timing determine seedling development across southwestern US restoration sites. Ecological Applications, 33(4), p.e2834. https://doi.org/10.1002/eap.2834
  9. Esque, T. C., DeFalco, L. A., Tyree, G. L., Drake, K. K., Nussear, K. E., & Wilson, J. S. (2021). Priority species lists to restore Desert Tortoise and pollinator habitats in Mojave Desert shrublands. Natural Areas Journal, 41(2), 145-158. https://doi.org/10.3375/043.041.0209