荒漠草原柠条引入后根系拓扑结构演变及对土壤碳氮组分的影响OA

[Objective]This study aims to investigate the dynamic changes of root systems after artificial planting of Caragana korshinskii in desert steppe and the action mechanisms of these changes on soil nutrients,thereby providing a scientific basis for improving soil quality and nutrient cycling in desert transition zones.[Methods]This study was conducted in a typical desert steppe area of Yanchi County,Ningxia,with natural grassland and Caragana korshinskii plantations of 9,14,24 and 35 years old selected as the research objects.Using CT scanning and image processing techniques,root system architecture was obtained and root topology parameters were quantified to investigate the changes in root system architecture and topology after the introduction of Caragana korshinskii,as well as the effects of these changes on soil carbon and nitrogen components.[Results](1)Overall,with the increase of stand age after Caragana korshinskii introduction,coarse roots gradually increased,while fine roots increased significantly from 24 to 35 years.(2)In the 0-20 cm soil layer,stand age significantly affected root equivalent diameter(p<0.05).Compared with the 14-and 24-year-old stands,the 35-year-old stand showed a significant decrease of 28.1%and 24.5%,respectively,but a pronounced increase of 15.3%compared with the 14-year-old control grassland.As stand age increased,root number density and root length density first decreased and then increased,but both were lower than those of the control grassland,following the order of CK>35 a>9 a>14 a>24 a.On the contrary,the root equivalent diameter of each plot first increased and then decreased,and the 35-year-old stand was even lower than the control grassland.In the 0-10 cm soil layer,stand age significantly affected root volume density(p<0.05).Compared with the 9-year-old stand,the 24-year-old and 35-year-old stands showed a significant decrease of 22%and 44%,respectively.(3)In the 0-20 cm soil layer,root volume density was significantly positively correlated with soluble organic carbon(p<0.05).Root equivalent diameter was significantly positively correlated with easily oxidizable organic carbon and total organic carbon(p<0.05),and extremely significantly positively correlated with particulate organic carbon and total nitrogen(p<0.001).(4)PLS-SEM results showed that root system topology had an extremely significant positive effect on nitrogen components(p<0.001),and carbon components also had an extremely significant positive effect on nitrogen components(p<0.001).[Conclusion]After the artificial introduction of Caragana korshinskii in the desert steppe,the development of coarse shrub roots initially inhibits the growth of herbaceous fine roots,and the fine roots of herbaceous plants partially recover in the later stage.The optimization of root system topology significantly improves the soil nitrogen supply capacity,establishing a positive soil-plant interaction mechanism.