Non-Herbaceous Biochars Exert Neutral to Negative Influences on Arbuscular Mycorrhizal Fungal Abundance.

Both biochar and mycorrhizae are potentially important components in soil carbon sequestration. As both factors are subject to management, understanding and exploiting their interactions may be advantageous. To date, a majority of the observed positive interactions between biochar and arbuscular mycorrhizal fungi (AMF) resulted from small to medium additions of herbaceous biochars to soils. Additionally, many of these experiments have focused almost exclusively on the ability of AMF to colonize plant roots. Results on how non-herbaceous biochars e.g., those made from wood or nutshells, affect the abilities of AMF to colonize plant roots and surrounding soils remain scarce. Here we present results from three different biochar addition experiments. In two of the three experiments, we employed multiple addition rates of wood derived biochars, while our third experiment featured the incorporation of three different peanut shell biochars. Lastly, we used a different kind of soil in each of the three different experiments. Through these experiments, we tested how non-herbaceous biochars can affect plant growth, AMF root colonization, and soil AMF hyphal abundance. Results show that although small additions of non-herbaceous biochars may exert some neutral effects on plants and AMF, their effects at higher addition rates can be strongly negative. In comparison to prior experiments showing positive plant and AMF responses to herbaceous biochars, these three experiments show that similar additions of some non-herbaceous biochars may produce opposite effects. Our results illustrate the importance of considering biochar type (i.e. woody vs. herbaceous), generation temperature and addition rate when attempting to stimulate biomass production by both AMF and their host plants in any efforts to increase soil C sequestration rates.