What does nutrient cycling refer to in sustainable ecosystems?

Nutrient cycling in sustainable ecosystems refers to the natural processes that recycle nutrients through both biotic (living organisms) and abiotic (non-living environmental factors) components. This cycle is essential for maintaining ecosystem health, as it ensures that vital nutrients, such as nitrogen, phosphorus, and potassium, are available to plants and other organisms that rely on them for growth and development.

In this context, nutrients are constantly exchanged among organisms, the soil, water, and the atmosphere. For instance, plants absorb nutrients from the soil, herbivores consume plants and thus take in those nutrients, and when these animals die or produce waste, the nutrients are returned to the soil, where they can be reused by plants. This ongoing cycle is fundamental for ecosystem sustainability, as it supports productivity and reduces dependence on external inputs.

The other options do not accurately reflect the nature of nutrient cycling. The consumption of nutrients by top predators is a part of the food web but does not encompass the broader processes of nutrient recycling. The linear movement of nutrients into a system ignores the cyclical nature of nutrient availability and reuse. The reliance on chemical fertilizers is contrary to the principles of sustainable ecosystems, which aim for self-sufficiency and resilience rather than dependency on external chemical inputs