Anti-Scourability Of The Herbaceous Root-soil System In The Riparian Zone Of The Three Gorges Reservoir,China

Under seasonal water level fluctuation and periodic dry-wet alternation,the distribution,morphological parameters and biomass of plant roots in the riparian zone of the Three Gorges Reservoir changed significantly with the growing season and the depth of flooding.However,the response mechanism of soil anti-scouribility to them are still not clear,which can not effectively guide the selection and community construction of land-fixing and revetment plants in the riparian zone.Three typical herbaceous plants in the riparian zone of the Three Gorges Reservoir were selected as the objects,and the physical and chemical properties,roots morphological parameters and anti-scouribility indexes of root-soil systems at different growth stages were determined,to analyze roots characteristics and anti-scouribility changes of herbaceous plants at different elevations and depths of soil layers and to reveal the response mechanism of soil anti-scouribility to the temporal and spatial changes of herbaceous roots growth in the fluctuation zone.The main results are as follows:(1)The roots of the three herbaceous species were mainly distributed in the soil layer of 0-10 cm,and D≤1.00 mm had a large root proportion.The roots biomass of the three herbaceous were significantly higher at 172 m and 165 m elevations.At the early stage of growth,the roots biomass of Hemarthria compressa and Cynodon dactylon were both significantly higher than that of Xanthium sibiricum(P<0.05).The roots biomass of Hemarthria compressa and Xanthium sibiricum were both higher in the flourishing period.Compared with the early growth stage,the increase of roots biomass of Xanthium sibiricum was the largest,followed by Hemarthria compressa,and Cynodon dactylon was the smallest.(2)The root-soil systems of 0-10 cm soil layer of the three herbs had strong anti-scourability.The root-soil systems anti-scouribility of three herbaceous gradually decreased with the decrease of elevation,and this change trend was relatively insignificant in the flourishing period.In the early stage of growth,the root-soil systems anti-scouribility of Hemarthria compressa was the strongest,followed by Cynodon dactylon,and Xanthium sibiricum was the weakest.During the vigorous growth period,the root-soil systems anti-scouribility of Xanthium sibiricum and Hemarthria compressa were both stronger.Compared with the early growth stage,the root-soil systems anti-scouribility of Hemarthria compressa and Xanthium sibiricum in the flourishing stage were significantly enhanced.(3)The root-soil systems anti-scouribility indexes of 0-10 cm soil layer of three herbs were significantly positively correlated with root indexes(P<0.05).The root indexes of D≤2.00 mm was the key factor affecting soil anti-scour performance.From the early growth stage to the vigorous growth stage,the continuous growth of roots system was beneficial to the gradual improvement of soil anti-scouribility.(4)The linear regression equation can be used to fit the relationship between the anti-scouribility indexes,root indexes and basic soil physical and chemical properties indexes of root-soil systems in 0-10 cm soil layer.It can be seen that the roots growth status of typical herbaceous plants in the fluctuation zone played a leading role in the impact of soil anti-scouribility.With the continuous growth of roots system,this leading role became more and more obvious.