Potential benefits of biochar and mycorrhizal fungi on shortleaf pine restoration in northcentral Alabama

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Casey Iwamoto, Courtney M. Siegert, Joshua Granger, Krishna Poudel and Adam Polinko, Department of Forestry, Mississippi State University, Starkville, MS

Background/Question/Methods
Coal strip mining has left degraded soils throughout the southeastern United States. These soils tend to have low pH, high bulk density, impacted hydraulic processes, and an accumulation of heavy metals that limit revegetation and reforestation efforts. Shortleaf pine (Pinus echinata) has a natural ability to grow on post-mined sites and has the largest native range in the southeastern United States, making it an ideal species for such restoration efforts. Furthermore, soil restoration using a combination of biochar and mycorrhizal amendments can provide many benefits for degraded soils ranging from increasing carbon sequestration, reducing erosion, promoting plant growth, and immobilizing heavy metals. However, limited empirical field trials have been conducted on the success of soil amendments on both soil health and tree productivity. To provide restoration recommendations to land managers and landowners, we established a field trial in Winston County, Alabama at a reclaimed mining site. In 2021 we planted Shortleaf pine in a complete randomized block design with 10x10-foot spacing with two treatments: biochar and microbial inoculation in four replicates. We measured soil bulk density, pH, heavy metal content, electrical conductivity, carbon content, and nitrogen content both before and after planting every three months. We will also monitor shortleaf pine survival and growth.
Results/Conclusions
Our preliminary results for pH, bulk density, and electrical conductivity are within the expected range for shortleaf pine to do well on this post-mined site. The pH ranged from 4.72 pH to 6.09 pH with a mean of 5.55 pH. Dry bulk density ranged from 1.02 g/cm3 to 1.72 g/cm3 with a mean of 1.46 g/cm3. Wet bulk density ranged from 1.36 g/cm3 to 1.96 g/cm3 with a mean of 1.74 g/cm3. Electrical conductivity ranged from 156.72 µS to 545.80 µS with a mean of 273.19 µS. Nitrogen content ranged from 0.07% to 0.27% with a mean of 0.15%. Carbon content ranged from 1.13% to 3.91% with a mean of 2.31%. 3-month post-planting data is pending. We expect future results to show a more productive environment than the original reclaimed mining site for shortleaf pine to be restored to. This study will help support our understanding of biochar’s interaction with mycorrhizal fungi inoculation, role in restoration, and use in southeastern United States soils.