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1.INTRODUCTIONThe rapid development of the global economy has accelerated the dwindling reserves of non-renewable energy sources, promoting the urgent need for sustainable alternative energy sources. Today, fossil fuels are losing their value for exploitation due to their high cost or the ecological issues they cause during extraction and use. However, our energy demand is enormous. Therefore, it is necessary to develop green renewable energy sources1. The energy radiated by the sun is vast, making solar energy the most reliable source for humanity’s future. Large-scale construction of photovoltaic power stations inevitably impacts the ecological environment. Therefore, facing the new requirements of ecological civilization construction, it is crucial to quantitatively analyze the ecological environment impact of photovoltaic power stations, and find methods to protect the ecological environment while reasonably constructing photovoltaic power stations, which is of great practical significance2. Currently, both domestic and foreign scholars have relatively few studies on the ecological environment effects of photovoltaic power station construction. The construction of photovoltaic power stations inevitably impacts regional climate. Some scholars have analyzed the environmental impact of large-scale photovoltaic power stations in the United States, indicating that the construction of photovoltaic power stations does not adversely affect the climate. On the contrary, it can lower urban temperatures and significantly reduce sensible heat flux. Many domestic scholars have studied the impact of photovoltaic power station construction in desert areas on the ecological environment, suggesting that the construction of photovoltaic power stations has regulated the local climate, manifested in reduced net radiation received by the ground, decreased temperatures of air and soil, reduced evaporation of soil moisture, thereby increasing soil moisture content and air humidity, making the local microclimate more suitable for vegetation growth, and therefore, increasing vegetation coverage in areas with photovoltaic power stations3. Vegetation restoration is related to local microclimate and various soil elements, which are not influenced by a single factor but are interrelated and influenced by climate factors and vegetation communities, that is, climate, soil, and other environmental factors and vegetation interact with each other4. In general, photovoltaic power stations contribute to energy conservation and emissions reduction, regulate surface radiation and air temperature in the construction area, and have a profound impact on the ecosystem of the Gobi area. Qinghai is a typical ecologically fragile area in China, housing the country’s largest photovoltaic base. This study takes the photovoltaic power station area in Gonghe County, Hainan Prefecture, Qinghai Province, as the research area, analyzes the climate, soil, and vegetation conditions of the Gonghe photovoltaic industrial park, explores the impact of photovoltaic power station construction on the natural environment, and explains the mechanisms of impact, quantitatively studying the ecological environment conditions of the photovoltaic power station on spatial and temporal scales. It aims to understand the impact of desert photovoltaic development on the ecological environment, providing a reference for the ecological environment evaluation of desert photovoltaic areas and a theoretical basis for the protection and construction of photovoltaic power stations5. Integrating domestic and foreign research on the impact of photovoltaic development on the ecological environment, the main effects of photovoltaic development on the ecological environment start from regional climate, soil, and vegetation aspects. 2.MATERIALS AND METHODS2.1Overview of the research areaThe research area for this study is the solar energy industrial park in Gonghe County, Hainan Prefecture, Qinghai Province, located in the Tala Desert Gobi in the northeastern part of Qinghai Province, with coordinates ranging from 100°26’0.67”E to 100°38’51.52”E and from 36°0’0.07”N to 36°12’50.91”N. The elevation ranges from 2700-3028 m. The research area is depicted in Figure 1. The Tala Desert is divided into three areas based on elevation: Tala I, Tala II, and Tala III. The research area has an average elevation of 2910 m, flat terrain, and a dry climate with little annual rainfall, significant diurnal temperature variations, an average annual temperature of about 3℃, annual precipitation of 3200-3800 mm, annual evaporation of 1550-3200 mm, annual sunshine hours of 2300-3500 h, high annual total solar radiation of 55-80 MJ/cm2. The Gonghe photovoltaic park’s ecosystem is a typical desert ecosystem in Northwestern China, with a plateau continental climate characterized by cold and arid sandy grasslands and low TOC content6. The Tala Desert covers an area of 29.53 hectares, with the land gradually desertifying year by year. The ecological base is poor, the ecosystem structure is simple, and the ecology is sensitive and fragile. Today, the Tala Desert is the area with the most severe salinization in Hainan Prefecture, Qinghai Province, and is also one of the main desertification areas in the upper reaches of the Yellow River. 2.2Data source and methodology
3.RESULTS AND ANALYSIS3.1Impact analysis of photovoltaic power stations on climate3.1.1Study on the impact of photovoltaic power stations on solar radiation field.Based on real-time monitoring data from three fixed monitoring stations within the Gonghe County Photovoltaic Industrial Park (2019-2020), a statistical analysis of the seasonal variation in net radiation was conducted. The construction of the photovoltaic power station had an impact on net radiation in the construction and operation area, the planned construction area, and the external control area, as shown in Figure 4. The net radiation seasonal variation process in these three areas from 2019 to 2020 shows that in spring and summer, the net radiation value in the construction and operation area is lower than that in the external control area, while in autumn and winter, it is higher. There is a significant difference in net radiation among the three stations during spring and summer, whereas, in autumn and winter, the differences are smaller, indicating that the variation in net radiation is relatively minor across seasons. 3.1.2Study on the impact of photovoltaic power stations on temperature.Based on real-time monitoring data from three fixed monitoring stations within the Gonghe photovoltaic station (2019-2020), a statistical analysis of seasonal changes in air temperature was conducted, as shown in Figure 5. The process of seasonal changes in air temperature for the three areas from 2019 to 2020 shows that the air temperature in the construction and operation area of the Gonghe photovoltaic station was the lowest, followed by the planned construction area, with the external control area having the highest air temperature. The daily average air temperature in the construction and operation area of the photovoltaic station was 10.65% lower than that in the planned construction area and 11.215% lower than that in the external control area during 2019-2020. The average air temperature in the construction and operation area decreased annually, with smaller differences in air temperature between the external control area and the construction and operation area in spring, summer, and autumn, and larger differences in winter. It can be concluded that the air temperature difference between the external control area and the construction operation area is obvious in winter, while the difference between the external control area and the construction operation area is small in summer. 3.1.3Study on the impact of photovoltaic power stations on humidity.Based on real-time monitoring data from three fixed monitoring stations within the Gonghe photovoltaic station (2019-2020), a statistical analysis of the seasonal variation in air relative humidity was conducted, as shown in Figure 6. The process of seasonal changes in air relative humidity for the three monitoring stations from 2019 to 2020 shows that the relative humidity was highest inside the construction and operation area, followed by the planned construction area, with the external control area having the lowest relative humidity. In 2019-2020, the relative humidity in the construction and operation area of the Gonghe County photovoltaic station was 4.56% higher in winter than in the planned construction area. There were higher differences in relative humidity between the external control area and the construction and operation area in spring and winter, with smaller differences in summer and autumn8. Therefore, it can be concluded that the relative humidity difference between the external control area and the construction and operation area in winter is obvious, while the difference between the external control area and the construction and operation area in summer is small. 3.2Analysis of the impact of photovoltaic power stations on soil3.2.1Study on the impact of photovoltaic power stations on soil temperature and humidity.(1) Impact of photovoltaic power stations on soil temperature Based on real-time monitoring data from three fixed monitoring stations within the Gonghe photovoltaic station: the construction and operation area (Station 1), the planned construction area (Station 2), and the external control area (Station 3) for 2019-2020, a statistical analysis of the seasonal variation in soil temperature was conducted, as shown in Figure 7. The soil temperature in the research area exhibited clear seasonal variations, with temperatures increasing from spring to summer before decreasing towards winter. The highest soil temperatures were observed in summer, with the lowest in winter9. From 2019 to 2020, the average soil temperatures at different depths within the construction and operation area of the Gonghe County photovoltaic station were lower than those in the external control area, with reductions of 34.56%, 34.05%, and 30.69% at 10 cm, 20 cm, and 40 cm depths, respectively. The soil temperature difference between the 10 cm layer in the external control area and the construction operation area was the highest in summer and the lowest in winter, and the soil temperature difference between the 20 cm layer was the highest in summer and the lowest in spring, and the soil temperature difference of the 40 cm layer was the highest in summer and the lowest in spring. Therefore, the temperature difference between different layers of soil in summer is large. (2) Impact of photovoltaic power stations on soil humidity Based on data from the three fixed stations for 2019-2020, the seasonal variation in soil humidity at different depths within the construction and operation area, planned construction area, and external control area is shown in Figure 8. The analysis indicates that soil moisture also shows significant seasonal variation, similar to soil temperature. Soil moisture at different depths in the construction and operation area, planned construction area, and external control area all demonstrate an increasing trend from spring to winter, peaking in summer before decreasing to its lowest point in winter, with the pattern of change generally mirroring that of soil temperature. During 2019-2020, the difference in soil moisture levels between the external control area and the construction and operation area at various depths was highest in autumn and lowest in winter. Hence, the impact on soil moisture is more pronounced in autumn, with a lesser impact observed in winter. 3.2.2Study on the impact of photovoltaic power stations on soil particle size.Laboratory analyses conducted in 2020 reveal that the soil particle size frequency in the planned construction area and the external control area of the Gonghe County photovoltaic station was consistent, hence the study focused on soil particle size inside and outside the photovoltaic field10. Figure 9 presents the cumulative frequency distribution of soil particle size inside and outside the photovoltaic field. The analysis shows that soil texture in the photovoltaic field is primarily coarse silt (0.02-0.05 mm), accounting for 27.85%, while the area outside the photovoltaic field is dominated by very fine sand (0.05-0.10 mm), accounting for 26.09%. Inside the photovoltaic field, the content of clay particles, fine silt, coarse silt, and medium sand is higher than outside, increasing by 2.96%, 8.26%, 3.93%, and 4.17%, respectively, while the content of very fine sand, fine sand, and coarse sand is lower, decreasing by 9.17%, 6.73%, and 3.11%. This indicates a general trend towards finer soil particles within the photovoltaic field. 3.2.3Study on the impact of photovoltaic power stations on soil nutrients.Table 1 presents the comparison of soil nutrient changes (0-20 cm) inside and outside the photovoltaic field in 2020. The data show that the contents of total nitrogen, total phosphorus, and total potassium—all essential nutrients—are higher outside the photovoltaic field than inside, indicating higher levels of nitrogen, phosphorus, and potassium available outside the field. Among readily available nutrients, the content of available potassium is higher outside the field than inside, while the content of alkali-hydrolyzable nitrogen and available phosphorus is lower outside than inside, suggesting that the photovoltaic field overall has higher levels of readily available nutrients, conducive to plant growth. The total carbon content is lower outside the field than inside by 19.88%, and organic carbon content is lower outside than inside by 10.13%, indicating that the construction of photovoltaic stations enhances the soil’s carbon sequestration capacity11. The pH levels of soil inside and outside the photovoltaic field are above 8.5, classified as strongly alkaline, with pH values of 9.03 and 8.96, respectively. Table 1.Soil nutrient index.
3.3Impact analysis of photovoltaic power stations on vegetation3.3.1Study on the impact of photovoltaic power stations on vegetation life forms.Plant life forms are the result of long-term adaptation to specific habitats and are reflected in the appearance of biological groups12. This study conducted two surveys of 13 plant communities in the research area and three surveys of small-scale treatment area communities, investigating the species composition of 23 community sample bands under 10 community types. The composition of each plant community, the analysis of each species’ life form, and the proportion of life forms at different scales are shown in Table 2. Table 2.Proportion of life forms at different scales.
From Table 2, it is evident that the medium-scale planning area and the large-scale control area have a higher proportion of annual herbs, indicating lower ecological stability in these communities. In the small-scale treatment area under three types of photovoltaic panels, plant life forms are mainly perennial herbs and densely tufted perennial herbs, suggesting that plant community composition in the photovoltaic station treatment area is stable, with high functional stability of plant communities13. The photovoltaic station construction area has the highest proportion of perennial cushion herbs, reflecting higher functional stability in plant communities. The proportion of densely tufted perennial herbs promotes the improvement of ecological service functions. In the large-scale habitat, medium-scale control area, and small-scale photovoltaic panel treatment area, the proportions of perennial cushion herbs are respectively 8.33%, 11.12%, and 11.24%, indicating a stronger function of sand prevention in the small-scale photovoltaic panel treatment area due to the higher presence of crustose plants. 3.3.2Study on the impact of photovoltaic power stations on community species diversity.The diversity of a community reflects its richness and is measured using various indices. The Simpson index measures the dominance of species, while the Shannon-Wiener diversity index represents the evenness of individuals within a community. The evenness index measures the uniformity of a community14. A comprehensive analysis of species diversity indices at different scales is presented in Table 3. Table 3.Species diversity analysis of community at different scales.
The data in Table 3 indicate that the large-scale habitat area and the medium-scale control area have higher species richness, species diversity indices, and species evenness indices, suggesting a richer biodiversity in these areas. In the small-scale treatment area, the slanted single-axis area has a high species richness (10 species) and diversity index (0.84), close to that of the large-scale habitat area (0.9). The large-scale habitat area, with a dominant presence of shrubs and semi-shrubs, has a simple community structure, an average species composition of 19 species, high species diversity, and an average Shannon-Wiener diversity index of 2.56. The small-scale study area with a slanted single-axis has a relatively high diversity index (0.84), close to the large-scale habitat area (0.9). The medium-scale control area, located 600 m from the treatment area, has the lowest species composition and diversity index. In the small-scale treatment area, the diversity index is highest under the slanted single-axis photovoltaic panel area (0.84), and lowest under the fixed panel area (0.66). This suggests a need for community optimization in the small-scale treatment area to enhance community diversity. The main issue in the photovoltaic power station construction and operation area is the need for optimization of plant community structure, as the community tends to evolve into a monoculture of dominant plants. Therefore, future work should focus on optimizing the plant community in the photovoltaic power station construction area. 3.3.3Study on the impact of photovoltaic power stations on plant community biomass.Based on surveys of different plots, Table 4 details the biomass of plant communities in the study area. The small-scale treatment area’s above-ground biomass (264.182) shows greater productivity than that of the large-scale habitat area (254.485), which in turn is greater than the medium-scale control area (214.46); in the medium-scale control area, the total biomass comparison is as follows: plot 3 > plot 6 > plot 2 > plot 1, indicating that the closer to the small-scale treatment area, the higher the biomass; the underground biomass is highest in the medium-scale control area, mainly because the dominant plant community in the medium-scale control area consists of shrubs or semi-shrubby herbaceous plants, accumulating the highest underground biomass over time; the small-scale treatment area’s total biomass productivity is higher than that of the large-scale habitat area, with the fixed photovoltaic panel area’s plant community biomass being the highest, reaching 1340.8 g/m2,15. Table 4.Biomass analysis of plant community in study area.
4.CONCLUSIONFocusing on the photovoltaic power station in the high-altitude desert area of Gonghe County as the research area, this study explored the ecological environment effects of photovoltaic power station construction. Based on field vegetation surveys, indoor soil analysis tests, and data from outdoor monitoring stations, it analyzed the spatiotemporal heterogeneity characteristics of climate, soil, and vegetation in the Gonghe photovoltaic park. The conclusions are as follows: From 2019 to 2020, the net radiation inside and outside the photovoltaic power station showed minor seasonal changes; the construction of the photovoltaic power station had seasonal differences in its impact on temperature, with more significant cooling effects in winter; the impact on air humidity also showed seasonal differences, with the most significant humidifying effects in winter, where the construction and operation area increased humidity by 4.56%. Furthermore, the construction and operation area’s soil temperatures at 10 cm, 20 cm, and 40 cm depths were significantly lower than those in the external control area, with reductions of 34.56%, 34.05%, and 30.69%, respectively, indicating that the construction of the photovoltaic power station significantly lowered soil temperatures, with a greater impact on surface temperatures. Soil moisture in the construction and operation area was higher than in the planned construction area and the external control area, suggesting that the photovoltaic power station has a moisture-preserving effect. The effects of the photovoltaic power station construction on soil moisture showed seasonal differences and were more pronounced in autumn. Soil particles within the photovoltaic field area were finer than those outside; the construction of the photovoltaic power station led to an improvement in soil nutrients. Lastly, the construction of photovoltaic panels in the operation area resulted in higher functional stability of plant communities; however, it reduced community species diversity and increased plant community biomass. ACKNOWLEDGEMENTSThis work was supported by the Qinghai Province Major Science and Technology Projects (grant number 2021-SF-A7-2); and the Scientific Research Program Funded by the Shaanxi Provincial Education Department (grant number 23JY060). REFERENCESAjami, M., Heidari, A., Khormali, F., Gorji, M. and Ayoubi, S.,
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