Evaluating the role of biotic and abiotic factors in hardwood tree plant development in the Central Hardwood Region (CHR).

Hardwood tree growth and development can be significantly influenced by the interplay between soil microbiota and tree physiology. Soil microbial communities contribute to enhancing water retention, improving nutrient cycling, and protecting against pathogens. Thus, though the exact mechanisms are unclear, these microbes directly affect overall tree height and diameter at breast height (DBH). Here, we investigated how soil chemistry and prokaryotic communities impacted growth of growth of Quercus rubra (red oak) and Juglans nigra (black walnut) across three sites in Indiana and Michigan. We compared individuals with poor and healthy, robust growth at each site while assessing correlations with soil texture, pH, nutrients, and microbial community composition (16S rRNA sequencing). Our results revealed significant correlations between tree growth and soil texture (sand/silt), cation exchange capacity, and base saturation, particularly in Q. rubra. Microbial alpha diversity differed by species and location with J. nigra exhibiting higher diversity than Q. rubra. Interestingly, we found that plant development status did not significantly alter community composition, though species and site influenced overall microbial community structure. Mantel tests revealed weak but significant correlations between microbial communities and DBH in both species, and between microbial communities and height in J. nigra. These findings suggest that while soil properties and microbial communities are associated with tree growth, their influence varies by species and location. Identifying microbial indicators associated with superior growth could inform reforestation and silvicultural practices in temperate hardwood ecosystems.