Soil bacterial diversity based on management and topography in a silvopastoral system

Authors: GURMESSA, BIYENSA - Polytechnic University Of Marche; Ashworth, Amanda; YANG, YICHAO - University Of Arkansas; Adhikari, Kabindra; SAVIN, MARY - University Of Arkansas; Owens, Phillip; Sauer, Thomas; PEDRETTI, EASTER - Polytechnic University Of Marche; COCCO, STEPANIA - Polytechnic University Of Marche; CORTI, GIUSEPPE - Polytechnic University Of Marche

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2021
Publication Date: 2/8/2021
Citation: Gurmessa, B., Ashworth, A.J., Yang, Y., Adhikari, K., Savin, M., Owens, P.R., Sauer, T.J., Pedretti, E.F., Cocco, S., Corti, G. 2021. Soil bacterial diversity based on management and topography in a silvopastoral system. Applied Soil Ecology. 163:103918. https://doi.org/10.1016/J.APSOIL.2021.103918.
DOI: https://doi.org/10.1016/J.APSOIL.2021.103918

Interpretive Summary: Soil microbes govern soil nutrient cycling, carbon storage, and crop productivity. However, land management activities can alter their structure either negatively or positively. Therefore, researchers designed a study to identify how forage crop type, soil fertility (poultry litter), and soil moisture levels impact soil microbial communities, as well as identify how topography (e.g. slope and elevation) influences soil microbial diversity in a silvopasture (integration of animal and tree production under one integrated system). Growing native grass forage crops resulted in an advantage over introduced grass species through increased microbial abundance. Poultry litter applied for two seasons did not influence microbial diversity, indicating long-term applications might be needed to see changes. There was also a strong correlation between microbial communities and selected topographic features. For example, number of different soil microbes was reduced as elevation increased, thus indicating elevation may be an important component for defining niches of selected microbes. In conclusion, the findings emphasize the need to select appropriate grass species for sustainable silvopasture production. Native grasses might be more preferred to introduced ones for maintaining soil ecosystem function, which is reflected in a healthier soil.

Technical Abstract: Soil microorganisms play crucial roles in nutrient cycling and provisioning ecosystem services. However, little is known about how soil microbiome communities are affected by soil management and landscape position. The current study was aimed to understand effects of forage species [non-native, cool season orchardgrass (Dactylis glomerate) and a warm season native grass mix (Andropogon gerardii and Schizachyrium scoparium) planted in strips between hedgerows], soil fertility (poultry litter and a control), and soil moisture regime (aquic and udic) on soil bacterial communities in a factorially arranged design with 3 replications; and, to evaluate linkages between terrain attributes and soil microbial assemblages. Landscape positions were clustered into 4 topographic functional units (TFUs) using the k-means method, and their impact on soil bacterial diversity was evaluated. Illumina sequencing results identified a soil moisture regime x forage species interaction, with native grass species under wet (aquic) conditions resulting in the most diverse microbial assemblages relative to dry (udic) and wet soil conditions for the introduced forage (orchardgrass). These results suggest an enhanced soil microbiome under native grasses with greater available water. Overall, microbial diversity was negatively correlated with elevation, suggesting niche differentiation and microbial preference for lower elevations. Overall, TFUs and selected terrain attributes may be valid for predicting microbiome dynamics in silvopasture systems.