雄溪河河岸带典型草本植物冬季温室气体排放评估OA

[Objective]This study aims to explore the role of river riparian zones in southern China as sources or sinks of greenhouse gases during winter.Traditional studies often focus on individual greenhouse gases,lacking sim-ultaneous observation and comprehensive assessment of multiple greenhouse gases such as CO2,CH4,and N2O.Therefore,the core objectives of this study are:(1)to quantify the winter fluxes of CO2,CH4,and N2O under three common riparian herbaceous plants(Ophiopogon japonicus,Allium tuberosum,and Cynodon dactylon)and in bare soil control plots;(2)to comprehensively assess the contribution of different vegetation types to the net winter greenhouse effect in riparian zones based on the global warming potential(GWP)model;(3)to identify the key environmental drivers affecting greenhouse gas fluxes;and(4)to provide a scientific basis for vegetation selection and ecological management in southern riparian zones from the practical perspective of promoting"carbon neutrali-ty".[Methods]This study took the riparian zone of the Xiongxi River,a typical river in southern China,as the study area.Three widely distributed and representative herbaceous plant communities,along with bare soil as con-trol areas,were selected.Throughout the winter,on one sunny day in the middle of each month,high-precision LI-7810 and LI-7820 trace gas analyzers were used for in-situ simultaneous observations to obtain flux data for the three greenhouse gases.Meanwhile,key environmental parameters such as air temperature,soil temperature,and soil moisture were synchronously recorded.To integrate the overall impact of the three greenhouse gases on global warming,the global warming potential model was adopted.On a 100-year time scale,with CO2 as the reference,all fluxes were uniformly converted into CO2 equivalents,thereby obtaining the daily comprehensive GWP for each study area.Data analysis was conducted using statistical methods including one-way analysis of variance(ANO-VA),Pearson correlation analysis,and regression analysis.[Results]Herbaceous plants significantly reduced the net carbon emissions in riparian zones during winter.After comprehensive assessment of CO2,CH4,and N2O,sig-nificant differences were found in winter GWP values across different areas.The average GWP in the Cynodon dac-tylon area,Ophiopogon japonicus area,Allium tuberosum area,and bare area was 3 817.77±249.24,3 963.31±265.66,6 876.89±536.17,8 653.71±756.08 mg/(m2·d),respectively.Although all areas functioned as net car-bon sources during winter,the GWP was effectively reduced in the three herbaceous plant-covered areas compared to bare land.This result,for the first time,quantified the mitigation effect of herbaceous plants on the greenhouse effect of riparian zones under a winter,multi-gas comprehensive assessment framework.The impact of different veg-etation types on greenhouse gas composition was species-specific.In-depth analysis of each gas component showed that CO2 emission fluxes in all vegetated areas were significantly lower than in bare land.CH4 fluxes mostly exhibi-ted weak absorption,with the lowest average in bare areas and the highest in Ophiopogon japonicus areas.Regarding N2O flux,bare areas showed the highest average,while the Cynodon dactylon areas had the lowest.Observations al-so indicated a distinct diurnal variation in riparian GWP,with higher values at noon and lower values in the morn-ing and evening.Pearson correlation analysis revealed that soil temperature was the key environmental factor driving this diurnal pattern,showing a highly significant positive correlation with the GWP value.This finding clarified the central role of temperature in regulating the carbon emission process of riparian zones in winter.[Conclusion](1)This study overcomes the limitations of traditional single-gas studies,systematically revealing for the first time in southern China's winter riparian environment that common herbaceous plants significantly and differentially influ-ence regional net greenhouse effects by altering CO2,CH4,and N2O emission profiles.It confirms that vegetation cover in winter also has a certain emission-reduction function.(2)From the perspective of the synergy between ripa-rian ecological engineering management and carbon neutrality goals,vegetation selection is crucial.Among the three plants examined in this study,Cynodon dactylon proves to be the optimal choice in winter due to its lowest GWP,whereas Allium tuberosum,though visually appealing,has the highest GWP and is therefore not recommended for planting from an emission-reduction perspective.(3)Soil temperature is the key environmental factor controlling the diurnal variation of winter greenhouse gas fluxes in riparian zones.This implies that under future global warming,rising winter temperatures may significantly enhance the carbon emission intensity of such ecosystems and should be fully considered in carbon cycle models.