城市河岸带芦苇根系特性及其与水土因子的关系

Root characteristics of Phragmites australis in urban riparian zone and its relationships with soil and water factors

摘要:

【目的】 分析城市河岸带典型群落优势种芦苇根系特性及其水土环境因子特征，进一步揭示植物地下根系生态过程，以期为河岸带植被管理与恢复提供参考。【方法】 以浐灞河西安段为研究区域，基于前期河岸带植物群落特征及人为干扰情况调研，选取典型样点采集优势种芦苇根系及其生境水土样品并进行室内分析，探讨城市河岸带植物群落优势种芦苇根系特性及其与生境水土因子的关系。【结果】 1）植物萌发期与营养生长期优势种芦苇根孔隙度范围分别为6.4%~43.87%、23.63%~ 35. 50%；两生长期浐河芦苇根径均存在差异，分别为0.88~1.92、0.90~1.62 mm，灞河样点基本持平；两生长期浐河样点芦苇根长规律基本一致，灞河样点基本持平，随生长期延续基本呈增长趋势；萌发期芦苇根茎节长为1.18~5.30 cm，营养生长期基本呈下降趋势。水分条件的变化显著影响芦苇根系形态结构，其以根孔隙度降低、根茎节长增加的方式适应过多的水分条件，同时人为干扰降低了芦苇根系形态特征值。2）不同生长期优势种芦苇个体根系生物量存在不同，呈现根茎远高于不定根，两生长期占比分别为76%~92%、65%~95%；浐河芦苇群落根生物量亦存在明显差异，两生长期干重范围分别为174.54~706.63和197.02~514.91 g/m2。外源营养输入促进了芦苇根系生长，增加了其根生物量；单一芦苇群落其根生物量较高，且营养生长期因藨草快速生长形成芦苇—藨草优势群落的根生物量增幅较大。3）不同生长期水土环境因子对芦苇根系特性影响不同。萌发期土壤水分、有机碳、速效磷、硝态氮、pH及水体pH、氨氮、可溶性磷对芦苇根系特性影响较大，营养生长期则有所变化。 【结论】 城市河岸带水文变化及人为干扰影响下，优势种芦苇根系特征及水土因子变化趋于复杂；植物群落物种组成显著影响优势种个体及群落根系生物量；在水文变化、外源营养输入及群落物种组成等显著变化下，植物根系特征与水土因子耦合关系亦有所不同。综上，建议在人为干扰的城市河岸带生态系统恢复过程中，减少人为干扰、优化河岸带植物群落组成可促进土壤中植物根系生态功能和土壤质量的改善。

Abstract:

【Objective】 This study aimed to elucidate the root characteristics of Phragmites australis and their response 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 vegetative 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 vegetative 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 during 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 reduce 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 vegetative 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，nitrate 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 restoration，reducing human interference and optimizing community composition are recommended.