Print PageMany plants use mycorrhizae to acquire nutrients, but relationships between plants and mycorrhizal fungi can range from mutualistic to parasitic depending on the availability of certain resources within the environment. In high resource patches it is more beneficial for plants to allocate fixed carbon to root structures that can obtain resources without the cost of maintaining mycorrhizae. This condition sets up a dynamic for behavior that should follow optimal foraging theory. We collected 227 root samples for the prairie bunchgrass Schizachyrium scoparium at 5 sites along a latitude gradient from Minnesota to Texas, USA. Sites sampled are part of the Nutrient Network, a global research cooperative testing replicate and combination treatments of nitrogen (N), phosphorus (P), and potassium (K) on grassland plant communities. We measured percent mycorrhizal colonization to test for differences with colonization in relation to nutrient availability.
Results/Conclusions
Treatment effects differed among sites by increasing percent mycorrhizal colonization at some sites and decreasing it at others. Nutrient addition at the site in Texas tended to decrease mycorrhizal colonization whereas addition of P increased colonization at the Kansas site and decreased colonization at the site in Nebraska. Possible drivers of differences among sites include local edaphic factors, mean annual precipitation, and differences in nutrient limitation at each site. Edaphic factors may cause differences in nutrient availability and limitation, which may lead to differential responses in mycorrhizal colonization among sites. Similarly, the addition of one nutrient could cause the limitation of another resource that may potentially have a greater influence on mycorrhizal investment. Understanding how plant resource acquisition strategies respond to increased nutrient loads is important because of increasing rates of nutrient deposition and may be important for studying resource competition strategy.
