Final answer:
The loss of fungi in a forest would slow down biogeochemical cycles, lead to nutrient accumulation in undecomposed matter, and impair plant growth due to reduced nutrient uptake.
Step-by-step explanation:
The loss of fungi in a forest ecosystem would slow down nutrient cycling. Fungi play a crucial role in breaking down dead organic matter and waste, releasing nutrients such as carbon, nitrogen, phosphorus, and sulfur back into the soil where they can be reused by plants and other organisms. Without fungi, these nutrients would accumulate in the form of undecomposed material, and plants would struggle to access them. Moreover, the intake of nitrogen by plants would be affected, as many fungi are involved in the nitrogen cycle, especially through mycorrhizal associations with plant roots that help in nitrogen uptake. Treating an area with fungicide would similarly alter the carbon and nitrogen cycles by removing these essential decomposers from the ecosystem. Additionally, the absence of symbiotic fungi, particularly mycorrhizae, would impair plant growth due to insufficient nutrient uptake.