Long-term photovoltaic succession promotes preferential ammonium accumulation in desert ecosystems

While nitrogen rigidly constrains productivity in desert ecosystems, the long-term impacts of rapidly expanding utility-scale photovoltaics (PVs) on soil nitrogen dynamics remain poorly understood. Here, we quantified the trajectories and environmental drivers of total nitrogen (TN), nitrate (NO₃ ^--N), and ammonium nitrogen (NH₄ ⁺-N) across three panel microhabitats over a 14-year desert chronosequence. Soil nitrogen accumulated progressively with increasing array age, with TN rising by 37%-54% after 12-14 years of operation. Crucially, NH₄ ⁺-N accumulated preferentially within 2-3 years and remained persistently elevated under panels (UPs). Although NO₃ ^--N also accumulated in this zone, it fluctuated in exposed areas (between-panel, BP and runoff, FL), indicating potential leaching losses. These findings highlight the decoupling of inorganic nitrogen dynamics, underscoring UP soils as persistent nitrogen sinks. Accordingly, we propose targeted interventions to optimize sustainable nitrogen management and mitigate environmental risks in desert PV ecosystems.