By Jessalyn Bachler
Jay Norton, Extension Soils Specialist Director at the University of Wyoming Soil Resource Laboratory, presented “Rangeland Soil Health: Interactions With Vegetative Recovery” during the breakout session at the Range Beef Cow Symposium XXVII on Nov. 16, 2021. Norton highlighted the importance of soil health on rangelands, and the correlation the two have between soil degradation and loss of forage production. He reviewed several studies to demonstrate the resiliency of degraded and disturbed rangelands.
Healthy Rangelands Support Soil Functions
For rangelands to maintain productivity and produce adequate levels of forage, soil health must be sustained and function properly. A healthy rangeland ecosystem will support several diverse soil functions, including:
- Nutrient Cycling - Holding and releasing an optimal amount of plant nutrients.
- Water Properties - High water storage potential and movement for plant growth and resistance to erosion.
- Physical Stability - Porous soil structure.
- Filtering and Buffering - Absorbing and degrading toxic substances.
- Resistance and Resilience - Stable soil that resists changes from unusual events (drought, flooding).
- Biodiversity and Habitat - Supports numerous plant and animal species and functions.
Assessing Soil Health on Rangelands
To assess soil health on rangelands, several levels of soil health indicators can be tested. The first level of indicators (Level 1 - Observations) can start with comparing observations between a degraded ecological site and a healthy, well-functioning ecological site, such as the amount of bare soil present, surface horizon depth, signs of erosion, soil structure and aggregation, soil texture, penetration resistance, salt accumulation and moisture content.
The second level of indicators (Level 2 - Field Tests) compares field tests from a degraded site to a healthy site, including tests on soil bulk density, ponded infiltration, aggregate stability, soil pH, soil electroconductivity (EC), lime content, and plant-available nitrogen and phosphorus.
The third and final level (Level 3 – Lab Tests) of soil health indicators analyzes lab tests from soil sampling, looking at soil organic matter (SOM) and carbon, plant available nutrients, active carbon, biologically available nitrogen, and soil salinity and sodicity to compare differences between degraded and healthy sites in range ecosystems.
Potential for Recovery After Disturbance
When rangelands are drastically or chronically disturbed from events, such as mining or drilling, long-term weed infestation, or heavy or season-long grazing patterns, soils begin to degrade and not function properly. Norton conducted a study that showed when soils have undergone drastic disturbance from oil drilling, it can take up to seven years post-reclamation to see recovery in soil organic matter, with carbon and nitrogen levels recovering more slowly. Recovery and establishment of planted native grasses, forbs and shrubs have also been recorded by the seven-year post-reclamation mark.
Norton reviewed two more studies looking at chronically degraded rangelands. The first study looked at a long-term cheatgrass invaded rangeland site. To restore the site that was dominated with cheatgrass back to healthy rangeland soils and native plant species, management included targeting grazing for fire prevention. Another study by Norton examined 150 years of continuous and season-long grazing in the riparian meadows of central Wyoming. The study demonstrated that chronic continuous-use grazing created a pedestalled plant community with bare space in between established plants. However, with a properly managed grazing system in place, soil health functions began to recover (pedestalled plants still present, but interspaces filled with sediment and organic matter) within eight to 30 years.
Summary
Once a rangeland ecological site has been assessed and determined to not be functioning properly, management changes should be initiated to improve soil health conditions, which will ultimately impact forage production. Generally, once a disturbance causes rangeland degradation, recovery is slow, but it is still possible when the drivers of the degradation are removed. Western rangelands have seen huge disturbances since settlement; the healthy and recovered sites that we see today demonstrate how resilient rangeland ecosystems are.
Source : sdstate.edu