Potential Benefits of Biochar and Mycorrhizal Fungi on Shortleaf Pine
(Pinus echinata) Restoration in Northcentral Alabama
Abstract
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 the adaptability to grow on post-mined sites due to being
able to tolerate soils with a low pH. It also has the largest native
range of pines 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 these 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 Spring 2021 we planted
Shortleaf pine in a complete randomized block design with 30.5x30.5 m
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. 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. Prior to soil
treatments and planting, soil pH was 5.55 ± 0.54 pH, dry bulk density
was 1.46 ± 0.14 g/cm3, wet bulk density was 1.74 ±
0.12 g/cm3, and electrical conductivity was 273.19 ±
141.33 µS. Soil nitrogen content was 0.15 ± 0.04% and soil carbon
content was 2.31 ± 0.76%. The average C:N ratio was 15.8:1. Survival of
planted seedlings after three months was 98%. Changes in soil physical
and chemical conditions relative to restoration treatments are pending.
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.