Supporting evidence varies for rangeland management practices that seek to improve soil properties and forage production in California

Abstract

California is increasingly investing in policies and programs that promote soil stewardship on natural and working lands as a way to help achieve multiple goals, including improved forage production and climate change mitigation. To inform the growing expectations for rangeland management activities to promote such services, we conducted an evidence synthesis assessing how four commonly suggested practices (silvopasture, prescribed grazing, compost application and riparian restoration) affect a suite of soil properties and plant-related metrics throughout the state. We extracted data on soil properties that are potentially responsive to management and relevant to soil health. We also extracted data on aboveground forage production, forage nitrogen content and herbaceous species richness. Our search resulted in 399 individual soil observations and 64 individual plant observations. We found that the presence of oaks had the largest effects on soil properties, with soil organic carbon, microbial biomass and other measures of soil fertility increasing beneath oak canopies. The presence of grazing increased compaction and total nitrogen, and decreased pH. Compost applications did not significantly affect any of the measured soil properties, but did boost forage production. Due to a lack of published data, we were unable to characterize the influence of rangeland riparian restoration on any of the soil or plant metrics in our review.

Cattle Grazing Moderates Greenhouse Gas and Particulate Matter Emissions from California Grassland Wildfires

“…In California grasslands, the amount of carbon uptake and whether a particular site is a net carbon source or sink can vary interannually, largely due to variability in annual rainfall [23][24][25]. Cattle grazing may affect soil carbon storage in California grasslands, though any effects appear specific to site characteristics and grazing regime [26][27][28].…”

“…However, the accumulation of aboveground biomass in shrublands results in the storage of atmospheric carbon. Therefore, unlike grasslands, where research has shown mixed or uncertain results from the effect of grazing management on ecosystem carbon storage [23,[26][27][28]67], rangelands that experience shrub encroachment in the absence of grazing will accumulate aboveground carbon up to some point determined by the shrub type, ecosystem constraints, or major disturbances (such as wildfires).…”

Payments for ecosystem services within the hybrid governance model: evaluating policy alignment and complementarity on California rangelands

“…Compensating landowners for soil carbon through PES markets generally depends on additionality, with the exception of programs that compensate landowners for existing soil carbon or avoided grassland conversion. For markets that require measurable augmentation of soil carbon, additionality can be difficult to ensure on semiarid and arid rangelands because of their nonequilibrium nature (Westoby et al 1989, Vetter 2005, Booker et al 2013, with variable outcomes depending on local edaphic and climatic characteristics (Carey et al 2020). California's rangelands are notable in their heterogeneity and spatial variability, ranging from arid inland valleys to mesic grasslands along the coast (Vetter 2005, Huntsinger and Bartolome 2014, Sloat et al 2018).…”