Researchers in China found that a large-scale desert solar park increased soil carbon content by 125.89% compared with undisturbed land. The study also identified how PV mounting systems, soil depth, and environmental factors influence carbon accumulation and its threshold effects.
A research team in China has investigated how large-scale solar installations affect soil organic and inorganic carbon pools in desert environments, aiming to identify the main drivers of carbon accumulation and the threshold effects governing soil carbon dynamics. Soil organic carbon (SOC) helps retain water and nutrients, supporting vegetation growth, while soil inorganic carbon (SIC), stored mainly in carbonate minerals, represents a major carbon reservoir in arid regions.
“The coupling of large-scale photovoltaic arrays with native ecosystems has formed photovoltaic ecosystems with unique energy and material exchanges, impacting key ecological processes like carbon cycling,” the researchers explained. “Deserts are a critical carbon pool with high ecological sensitivity; their stability is vital for the global carbon balance. However, disturbances from PV power stations may alter soil structure, resulting in the destabilization of carbon pools and changes in nutrient availability.”
The researchers conducted field measurements in 2023 and 2024 at the Talatan photovoltaic power station on the northeastern edge of China’s Qinghai–Tibet Plateau. The 1 GW facility covers 67 km2 and sits at an average elevation of 2,910 meters. Soil sampling took place in March, August, and December to capture freeze-thaw, non-freezing, and freezing conditions, respectively.
The team compared areas equipped with fixed, semi-tracking, and tracking mounting systems, selecting three random sampling points for each configuration. At each point, the researchers established 1 m × 1 m sampling plots beneath the panels, along their front drip lines, and between the arrays. They collected soil samples at depths of 0-10 cm, 10-20 cm, and 20-40 cm. Two nearby undisturbed desert plots served as control sites.
The researchers measured soil moisture, temperature, and pH on site and analyzed composite soil samples for carbon content, nutrients, and particle-size distribution. They used statistical comparisons and random forest models to identify key environmental drivers, while structural equation modeling helped assess direct and indirect relationships. They also applied XGBoost and SHAP analysis to investigate nonlinear responses and threshold effects.
“The results demonstrate that photovoltaic development significantly enhanced the carbon sink potential of desert soils, with the content of soil total carbon (STC) in the on-site area increasing by 125.89% compared to the off-site pristine control area,” the researchers said. “The content of soil carbon under the tracking bracket was higher than that under the semi-tracking bracket and fixed bracket, exhibiting a distinct under-panel enrichment effect.”
The findings also showed that SIC content increased slightly with soil depth, while SOC content declined significantly, resulting in an overall decrease in total soil carbon. The researchers also identified a threshold effect in the relationship between soil carbon content and its main environmental drivers.
“Notably, the response of STC to the dominant controlling factors exhibits a significant threshold effect: when STC content exceeds the critical threshold, its feedback to the dominant factors shifts from negative to positive,” they said.
The findings are presented in “Threshold effects and driving mechanisms of desert photovoltaic power stations on soil carbon pools,” published in Environmental Technology & Innovation. The research team included scientists from China’s Xi’an University of Technology and the State Power Investment Group Qinghai Photovoltaic Industry Innovation Center.
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