The earthworm population in the meadow is likely to decline as the soil pH decreases outside the optimum range, entering the zone of stress on the graph.
As the soil pH in the meadow gradually decreases from the optimum range into the zone of stress for earthworms, the most likely effect on the earthworm population is a decline. Earthworms are highly sensitive to changes in soil pH, and their population tends to thrive within a specific pH range. When the pH falls outside this optimal range and enters the stress zone depicted on the graph, it indicates that the soil conditions may become less suitable for the earthworms.
Changes in pH can impact soil quality, nutrient availability, and microbial activity, all of which influence the earthworm habitat. The decline in the earthworm population is indicative of their sensitivity to environmental conditions, highlighting the importance of maintaining suitable pH levels for their well-being and overall ecosystem health in the meadow.