Carbon Sequestration in Sandy Soils of Arid and Semi-Arid Climates: A Review - PowerPoint Presentation

1. Carbon Sequestration in Sandy Soils of Arid and Semi-Arid Climates: A ReviewSamantha L. Colunga1*, Leila Wahab2, Engil Pereira1**1School of Earth, Environmental, and Marine Sciences, The University of Texas Rio Grande Valley2School of Natural Sciences, University of California Merced

2. Why is Carbon/SOM/SOC Important?Soil organic matter/carbon (SOM/SOC): essential in providing soil fertility, good soil structure and plant productivityIncreases in carbon storage, through sequestration in soils, can potentially restore degraded lands and desertification, as well as minimize greenhouse gases from the atmosphereSOM expands water capacity, reduces erosion, and improves nutrient composition. (Broocks et al., 2017)

3. Arid and Semi-arid Climates30% to 35% of Earth’s terrestrial environmentsHigh temperatures, low records of precipitation, and sandy soil characteristics sandy soils with little to no vegetationSlight differences between arid and semi-arid climates.  Semi-Arid ClimatesArid ClimatesPrecipitationMinimum: ≤ 300mmAverage: 200-500mmMaximum: 500-800mmMinimum: ≤ 100mmAverage: 200mmMaximum: 300mmTemperatureLowest: 15⁰ to 22⁰CAnnual: 20⁰ to 25⁰CHighest: 30⁰ to 45⁰CLowest: -30⁰ to -50⁰CAnnual: 20⁰ to 30⁰CHighest: 45⁰ to 49⁰C

4. Soil Carbon Sequestration in Sandy SoilsNearly 900 million ha (hectares) of sandy soils constitutes land globally, but mainly in arid/ semi-arid climatesSandy soils lose water quickly with increasing, extreme temperatures, lack of structure, low carbon content, low aggregates.Sandy soils resulted from extensive land management (intensive tillage/ cultivation, overgrazing, excess nutrients/ fertilizers), extreme climate, and high erosion rates.Climate affects the amount of carbon or SOM in soils.Soil texture controls carbon stabilization through formation of aggregates.Clays and silts has high specific surface area that absorbs more carbon than sand particles with a low specific surface area.http://www.bio.miami.edu/dana/330/330F19_8.html

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6. Reasons: TillageTillage: agricultural practice that involves the overturning, stirring, or degradation of soils.Conventional Tillage: results in degraded soils, more sandy soils, lost organic matter/ carbon, aggregates and other physical and chemical properties.Conservational tillage: maintains, preserves, and enhances the quality of soils by avoiding disruption of soil aggregates. Most countries are conducting less than 15% of conservational tillage practices, while very few are slightly above 20%.

7. Approaches/Methods

8. ResultsSouth America, Africa, and Australia showed the largest SOC increase with conservation tillage.Error bars overlap 0 for Europe and Asia, indicating that there is no difference between conventional and conservational tillage.

9. ResultsConsisted of NA, SA, Africa, and EuropeNo tillage had higher improvements of SOC than other conservational tillage.

10. ResultsMore than 10 years, SOC is lowerLess than 10 years, SOC is higherError bar overlaps 0, indicating that there is no significant difference between SOC percent changes and time interval

11. ConclusionsMore conservational tillage in these arid regions, means more carbon can be stored in sandy soils helps rebalance the biogeochemical carbon cycle with the atmosphere, soils, and plants/crops. From a global perspective on arid and semi-arid regions, most of the sandy soils had higher SOC increases under no tillage practices.Long-term conversion to conservational tillage (> 10 years) showed an increase in SOC with more precision (lower variability) than short term studies (< 10 years). Limitations: insufficient studies for various continents in arid or semi-arid climates, not many long-term studies, shallow soil depths.Future: more studies examining SOC at greater depths (>1m), more experiments for longer time intervals, more experiments with proper climate, soil, and tillage criteria.