Temporal dynamics of PVPP ecological restoration benefits and their response to grazing pressure shifts: A UAV and plot survey-based quantitative assessment

Quantifying time-series changes in ecological parameters is essential for assessing the ecological restoration benefits resulting from the construction of photovoltaic power plants and subsequent on-site grazing. This paper quantitatively assessed the ecological restoration effects of photovoltaic power plants in the Gonghe County photovoltaic park, Qinghai Province, using unmanned aerial vehicle imagery, plot-based field survey data, and local grazing-pressure raster datasets. Using spectral indices, texture features, flight altitude, and an XGBoost model, we estimated above-ground biomass (R2 = 0.96; RMSE = 3.92) and analyzed changes in the ecological restoration effects under different grazing-pressure scenarios by jointly evaluating biomass alongside field measurements of soil organic carbon, soil moisture, and biodiversity. The results show that the operation of photovoltaic power plants has a significant restorative effect on ecosystems, but this effect is mainly concentrated in the early to middle stages. The recovery benefits of soil organic carbon and aboveground biomass begin to weaken around the 10th year, while those of soil moisture and biodiversity begin to decline around the 4th year. In addition, moderate grazing does not affect these restorative benefits, whereas continuously increasing grazing pressure shortens their duration. These findings provide an objective basis for assessing the ecological restoration benefits of photovoltaic power plants, and also offer a reference for the adaptive management of grazing in local photovoltaic parks.