Vegetation, water infiltration, and soil carbon response to Adaptive Multi-Paddock and Conventional grazing in Southeastern USA ranches

Ruminating on soil carbon: Applying current understanding to inform grazing management

Among options for atmospheric CO2 removal, sequestering soil organic carbon (SOC) via improved grazing management is a rare opportunity because it is scalable across millions of globally grazed acres, low cost, and has high technical potential. Decades of scientific research on grazing and SOC has failed to form a cohesive understanding of how grazing management affects SOC stocks and their distribution between particulate (POM) and mineral-associated organic matter (MAOM)-characterized by different formation and stabilization pathways-across different climatic contexts. As we increasingly look to grazing management for SOC sequestration on grazinglands to bolster our climate change mitigation efforts, we need a clear and collective understanding of grazing management's impact on pathways of SOC change to inform on-the-ground management decisions. We set out to review the effects of grazing management on SOC through a unified plant ecophysiology and soil biogeochemistry conceptual framework, where elements such as productivity, input quality, soil mineral capacity, and climate variables such as aridity co-govern SOC accumulation and distribution into POM and MAOM. To maximize applicability to grazingland managers, we discuss how common management levers that drive overall grazing pattern, including timing, intensity, duration, and frequency can be used to optimize mechanistic pathways of SOC sequestration. We discuss important research needs and measurement challenges, and highlight how our conceptual framework can inform more robust research with greater applicability for maximizing the use of grazing management to sequester SOC.

Grazing management for soil carbon in Australia: A review

The livestock industry accounts for a considerable proportion of agricultural greenhouse gas emissions, and in response, the Australian red meat industry has committed to an aspirational target of net-zero emissions by 2030. Increasing soil carbon storage in grazing lands has been identified as one method to help achieve this, while also potentially improving production and provision of other ecosystem services. This review examined the effects of grazing management on soil carbon and factors that drive soil carbon sequestration in Australia. A systematic literature search and meta-analysis was used to compare effects of stocking intensity (stocking rate or utilisation) and stocking method (i.e, continuous, rotational or seasonal grazing systems) on soil organic carbon, pasture herbage mass, plant growth and ground cover. Impacts on below ground biomass, soil nitrogen and soil structure are also discussed. Overall, no significant impact of stocking intensity or method on soil carbon sequestration in Australia was found, although lower stocking intensity and incorporating periods of rest into grazing systems (rotational grazing) had positive effects on herbage mass and ground cover compared with higher stocking intensity or continuous grazing. Minimal impact of grazing management on pasture growth rate and below-ground biomass has been reported in Australia. However, these factors improved with grazing intensity or rotational grazing in some circumstances. While there is a lack of evidence in Australia that grazing management directly increases soil carbon, this meta-analysis indicated that grazing management practices have potential to benefit the drivers of soil carbon sequestration by increasing above and below-ground plant production, maintaining a higher residual biomass, and promoting productive perennial pasture species. Specific recommendations for future research and management are provided in the paper.

Ecosystem carbon and nitrogen gains following 27 years of grazing management in a semiarid alluvial valley

Soils in semiarid riparian ecosystems have large carbon (C) stocks that promote water and nutrient availability for productive plant communities consumed by grazing animals. Changes to riparian hydrologic conditions caused by channel incision result in different edaphic conditions and a greater abundance of upland plant species that may be associated with lower soil C stocks. Using riparian meadows alongside Maggie Creek in central Nevada, we show that 27 years of modified grazing practices can repair ecosystem processes and increase the C stocks. We compared C and nitrogen (N) stocks (of soils and plant biomass) on floodplains, terraces, and uplands of reaches where grazing was either modified or excluded to reaches where no changes to grazing practices were made. Grazing management allowed beaver to establish, improving hydrology and lengthening the growing season. These changes allowed C and N to accumulate on geomorphic surfaces that extended from the stream channel to the surrounding hillslopes. A stoichiometric relationship between C and N shows carbon sequestration can reduce nutrient runoff to nearby waterways and may depend on nitrogen availability. Gains in ecosystem carbon ranged from 93 to 452 g C m^-2 y^-1 and were dominated by increases in soil C. Gains in soil C occurred across the full depth range measured (0-45 cm) and were comparable to those found in restored wetlands and meadows located in more humid ecosystems. Carbon gains exhibited substantial variability caused by microtopography and plant community composition. While grazing exclusion resulted in the largest gains in ecosystem C, managed grazing that limited consumption of riparian plants increased ecosystem C relative to reaches where management wasn't changed. We demonstrate that managed grazing that maintains ecosystem process is compatible with projects aimed at increasing soil carbon in semiarid riparian rangelands.

Exploring the most important indicators for environmental condition assessment using structural equation modeling and InVEST habitat quality model

Land degradation threatens the social welfare of human societies. In order to identify the most important indicators for land degradation assessment, this article quantified 36 vegetation and soil indicators. Ecosystem condition was determined based on the ecosystem threats using the InVEST habitat quality model, dividing the region to five degradation classes, i.e., negligible, little, medium, high, and very high degradation classes. The structural equation modeling showed that vegetation indicators were more important than soil indicators for land degradation assessment. Climate had a significant mediation on the relationships between soil and vegetation indicators and degradation (P < 0.05). Warning indicators were identified for each degradation stage. The mean changes of degradation indicators were 18, 35, 56, and 78% in little, medium, high, and very high degradation classes, respectively. Cold and semi-arid climates were more influenced by vegetation indicators which had the most variations in the early stages of degradation. Warm and arid regions were more affected by soil indicators, which had the most variations in the high and very high degradation stages. This approach provides comprehensive and necessary information about the condition of ecosystems by determining the severity of degradation in an area, the most important warning indicators of degradation, and the deviation of ecosystems from normal condition at each degradation classes, which helps a lot to managers to choose appropriate restoration plans.

Grazing Cattle, Sheep, and Goats Are Important Parts of a Sustainable Agricultural Future

Many people believe that animal agriculture should be phased out and replaced with vegetarian substitutes. The livestock industry has also been attacked because it uses vast amounts of land. People forget that grazing cattle or sheep can be raised on land that is either too arid or too rough for raising crops. At least 20% of the habitable land on Earth is not suitable for crops. Rotational grazing systems can be used to improve both soil health and vegetation diversity on arid land. Grazing livestock are also being successfully used to graze cover crops on prime farmland. Soil health is improved when grazing on a cover crop is rotated with conventional cash crops, such as corn or soybeans. It also reduces the need for buying fertilizer. Grazing animals, such as cattle, sheep, goats, or bison, should be used as part of a sustainable system that will improve the land, help sequester carbon, and reduce animal welfare issues.

Adaptive multi-paddock grazing management's influence on soil food web community structure for: increasing pasture forage production, soil organic carbon, and reducing soil respiration rates in southeastern USA ranches

Background

Measurement of two grazing management's influence on pasture productivity, soil food web structure, soil organic carbon and soil microbial respiration efficiency was conducted on five southeastern US, across-the-fence ranch pairs to compare adaptive multi-paddock grazing (AMP) management, using short grazing events with planned, adaptive recovery periods, to conventional grazing (CG) management, with continuous grazing at low stock density.

Methodology

A point-in-time experimental field analysis was conducted to compare five AMP or CG ranch pairs to better understand the influence of grazing management on (a) standing crop biomass productivity; (b) soil food web community population, structure and functionality; (c) soil organic carbon accrual; and d) soil-C (CO₂) respiration kinetics.

Results

AMP grazing systems outperformed CG systems by generating: (a) 92.68 g m^-2 more standing crop biomass (SCB), promoting 46% higher pasture photosynthetic capacity (Two sample Mann-Whitney; Z = 6.1836; no DF in MW; p = 6.26 × 10^-10; Effect size = 0.35) (b) a strong positive linear relationship of SCB with fungal biomass (R = 0.9915; F(1,3) = 175.35; p = 0.015); fungal to bacterial (F:B) biomass ratio (R = 0.9616; F(1,3) = 36.75; p = 0.009) and a soil food web proxy (R = 0.9616; F(1,3) = 36.75; p = 0.009) and a concurrent very strong inverse relationship with bacteria biomass (R = -0.946; F(1,3) = 25.56; p = 0.015); (c) significant predator/prey interactions with an inverse relationship with bacterial population biomass (R =  - 0.946; F(1,3) = 25.56; p = 0.015) and a positive relationship with total protozoa enumeration (R = 0.9826; F(1,3) = 83.68; p = 0.003) when compared to SCB; (d) a 19.52% reduction in soil C (CO₂) respiration rates (Two sample t-test; T = -2.3581; DF = 52.3541; p = 0.0221; Effect size = 0.59); and (e) a 20.6% increase in soil organic carbon (SOC) in the top 10 cm of soil profile (Two sample Mann-Whitney; Z = 2.6507; no DF in MW; p = 0.008; Effect size = 0.24). Rancher conversion to AMP grazing strategies would appear to regenerate soil food web population, structure, diversity and biological functionality helping to improve: carbon flow into plant biomass, buildup of soil carbon, predator/prey nutrient cycling and soil microbial respiration efficiency while offering improved climate resilience and a strategy to increase the capture and storage of atmospheric CO₂ in soils of the world's rangeland.