Which of the following processes limits net primary productivity in terrestrial ecosystems?

Moisture availability is a critical factor that influences net primary productivity in terrestrial ecosystems. Plants require water for photosynthesis, nutrient uptake, and overall growth. In regions where moisture is limited, the ability of plants to photosynthesize is reduced, leading to lower rates of biomass production. This can result in lower productivity in both arid and semi-arid environments where water scarcity limits the growth and survival of plant species.

While temperature fluctuations, carbon dioxide levels, and soil pH can also affect plant growth and productivity, moisture availability is often the more immediate and limiting factor in many ecosystems, especially in areas where drought or insufficient rainfall occurs. This makes it vital for understanding and managing ecosystems and agricultural practices where water resources are a concern.