Root characteristics of Phragmites australis in urban riparian zone and its relationships with soil and water factors
[Objective]This study aimed to elucidate the root characteristics of Phragmites australis and their re-sponse to nitrogen and phosphorus in typical urban riparian habitats,providing insights into the ecological process of plant roots.The findings were intended to inform riparian vegetation management and restoration strategies.[Method]Root samples of P.australis,along with water and soil samples,were collected from typical riparian zones in the Xi'an section of the Chanba River.Root morphological characteristics of roots during germination and vegeta-tive growth stages were analyzed in relation to water and soil properties.[Results](1)The root porosity of Phrag-mites australis ranged from 6.4%～43.87%during the germination stage and 23.63%～35.50%during the vegeta-tive growth stage.Root diameters ranged 0.88～1.92 mm(germination stage)and 0.90～1.62 mm,(vegetative stage).Rhizome node length ranged from 1.18 to 5.30 cm during germination period,and showed a downward dur-ing vegetative growth.Changes in water conditions significantly affected root morphology with P.australis adapting to excessive water by reducing root porosity and increasing rhizome node length.Human interference was found to re-duce the morphological values of roots.(2)Significant differences in individual root biomass were observed between growth stages,with rhizomes was accounting for 76%～92%and 65%～95%of total biomass during the germination and vegetative growth stages,respectively.The root biomass of P.australis communities also varied significantly,with the dry weights ranging from 174.54～706.63 g/m2 during germination and 197.02～514.91 g/m2 during veg-etative growth.Exogenous nutrient input enhanced root biomass,particularly in mixed P.australis-Scirpus triqueter communities,where the rapid growth of S.triqueter significantly increased overall biomass.(3)Correlation analysis showed that the soil and water factors impacted root characteristics of P.australis differently across growth stages.During germination,root traits were strongly influenced by soil moisture,organic carbon,dissolved phosphorus,ni-trate nitrogen,and pH,as well as water pH,ammonia nitrogen,and dissolved phosphorus.These relationships shifted during the vegetative growth stage.[Conclusion]Hydrological changes and human disturbances in urban riparian zones lead to complex interactions between root characteristics and water-soil factors.Species composition within plant communities significantly affects root biomass at both individual and community levels.The coupling of plant root traits with water and soil factors varies under changing hydrological conditions,exogenous nutrient inputs,and community dynamics.To enhance plant root ecological functions and soil quality during urban riparian ecosystem res-toration,reducing human interference and optimizing community composition are recommended.
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