We began our research looking to see if there could be a connection between the presence of fungi near waterways and the health of the stream specifically for salmon spawning. There are several stream characteristics that can help to identify a healthy stream. In order to have a realistic observation and interpretation of data, we narrowed the scope of our research to the similarities in the average pH of a healthy stream and the soil pH that is most conducive to aiding in reproductive activity in fungal species.
To discuss pH and its affect on soil and organisms, we need to define it. The city of Vancouver has this to say: “pH is the measurement of hydrogen ions on a logarithmic scale from 0-14. The value of 7 is considered neutral, values greater than 7 are basic and below 7 is acidic. Average soil pH ranges are from 4-8. Each plant has a specific pH range for optimal growth. Phosphorous, one of the three main soil nutrients, is strongly dependent upon soil pH. Conditions that are overly acidic or basic decrease phosphorous availability to plants. A higher pH may also help to immobilize heavy metal contaminants within the soil. Soil can also help to regulate the pH of water entering the stream.”
The optimal pH of fungi varies somewhat across species. Takashi Yamanaka did a study on the preferred pH, and discovered, “Many of the saprotrophic species grew well at pH 7 or 8; the ectomycorrhizal species showed optimum growth at pH 5 or 6. The pH suitable for the in vitro growth of these fungi was correlated with the pH of forest soil where these fungi occur." Saprotrophic species typically live on live (or recently alive) wood, whereas ectomycorrhizal species typically grow from a mycorrhizal network beneath the surface of the soil. Yamanaki’s claim is that in both types of species the soil of the area they are found is matched to the pH preference of the fungi.
In his paper, Johann Rousk speaks to this connection. “The soil microbial community is responsible for most nutrient transformations in soil, regenerating minerals that limit plant productivity. Fungi and bacteria are the two groups that dominate the microbial decomposer community, and, crudely defined, they share the function of decomposing organic matter in soil, indicating that there is a strong potential for interaction.” (Rousk, 2020). The import of fungal growth in soil is so great in this context that we believe that the presence of fungi in the soil near streams may be able to help indicate a healthy pH in nearby waterways.
As such, we may present a question that has been narrowed down from the beginning of our curiosity. Can fungal fruiting bodies be an indicator of stream health as a function of pH?
