| The construction of solar photovoltaic(PV)power plants is one of the mainstream directions of new energy development and utilization worldwide.In recent years,construction sites of PV power plants in China have gradually expanded to grassland areas.As a result,the distributions of PV power stations have become a kind of “new landscape” in the Songnen Grassland.The construction and operation of PV power plants can cause a series of environmental impacts,such as damage to the disturbance of vegetation and soil and alteration of the local microclimate.However,little is known about how PV panel arrays affect grassland ecosystems;in detail,the effects on soil ecological functions,including soil enzyme activities in degraded grasslands,are rarely reported.Therefore,studying the response of soil enzyme activities and enzyme stoichiometry characteristics in degraded grasslands to PV panel arrays and their mechanisms is essential for the scientific assessment of the impacts of PV plants on grassland ecosystems.Our study site is located at the Honghua PV power station in the Songnen Plain in northeastern China.The power station was completed and started operation in 2018,and the grassland was severely degraded before the construction of the station.A two-factor(i.e.,PV panel factor and plant community type factor)randomized block design was used.In this study,the first factor consisted of three treatment levels,the ambient zones outside the PV arrays(control group,A),the gap zones between the PV panels(G),and the sheltered zones under the PV panels(U).The second factor consists of three levels: the Leymus chinensis community,the Artemisia scoparia community,and the Forb community.The PV plant and surrounding areas are fenced and free from grazing and other human interference.This study aims to answer the following questions:(1)What are the effects of PV panels and community types and their interaction on soil enzyme activities and soil enzyme stoichiometric characteristics?(2)Can the PV panel treatment mitigate the soil microbe phosphorus(P)limitation in the degraded grassland?(3)What are the key characteristics in the plant community and soil affecting the soil enzyme activities and the enzyme stoichiometry ratios?The main conclusions of this study are as follows:(1)The PV panel arrays increased the soil enzyme activities in the grassland.Compared with the ambient zones outside the PV arrays,the PV panel arrays significantly increased the activity of α-1,4-glucosidase(αG),β-1,4-glucosidase(βG),β-1,4-xylosidase(βX),cellobiohydrolase(CBH),β-1,4-N-acetylglucosaminidase(NAG),L-leucine aminopeptidase(LAP)and acid phosphatase(a P)in the soil of the three plant communities.(2)The PV panel treatment was able to mitigate the soil microbe P limitation.Among them,the sheltered zones under the PV panel treatment(U)more significantly alleviated the soil microbe P limitation than the gap zones between the PV panel treatment(G)in the three plant communities.(3)The key soil parameters affecting the soil hydrolase activities were soil p H,soil water content(SWC),carbon(C),and nitrogen(N)availability.Simultaneously,the key plant community characteristics were plant height,community cover,plant density,aboveground biomass,and belowground biomass.The key soil characteristics affecting the soil enzyme stoichiometry ratios were soil p H,SWC,C and N content,and C:N.The key plant community characteristics were the same as those affecting hydrolase activities.However,there were differences in the key soil parameters and plant characteristics affecting the soil hydrolytic enzyme activities and the enzyme stoichiometry ratios in the different PV panel treatments.In conclusion,the PV panel arrays had significant effects on the soil hydrolase activities and the enzyme stoichiometry characteristics and alleviated the soil microbe P limitation in the different plant communities in the Songnen Grassland.Overall,the PV power station improved the soil nutrient status to some extent and positively restored soil functions in the degraded grassland.This study has important theoretical implications for the in-depth understanding of the effects and mechanisms of PV power stations on the soil ecological functions in degraded grassland ecosystems,which can provide some theoretical references for the planning,environmental assessment,and construction of PV power stations in the Songnen Plain in the future.In addition,this study confirmed that the soil enzyme stoichiometric ratio C:N:P can be an effective indicator for monitoring soil recovery in the Songnen Grassland. |
