The main source of nutrients for plants in terrestrial ecosystems is the soil, which provides essential elements such as nitrogen, phosphorus, and potassium. These nutrients are vital for plant growth, development, and reproduction. Soil composition and health influence the availability of these nutrients, which can be affected by factors like organic matter, soil pH, and moisture. Healthy soils support not only plant life but also the entire food web reliant on primary producers, making soil health a cornerstone of ecosystem sustainability.