Root Traits and Erosion Resistance of Three Endemic Grasses for Estuarine Sand Drift Control

In southern Taiwan, rivers sporadically cease to flow and dry up in winter. The exposed dry riverbeds are very vulnerable to wind erosion. The strong northeast monsoon often induces serious estuarine sand drift and fugitive dust, which cause damages to agricultural crops, human health and infrastructures. Giant reed (Arundo formosana), common reed (Phragmite australis) and the wild sugarcane (Saccharum spontaneum) are pioneer grass species in estuary areas. They have great potential to reduce wind erosion and control windblown dust on agricultural lands. Nevertheless, their root traits, biomechanical characteristics and wind erosion resistance have not been investigated. In this research, the root traits were investigated utilizing the hand digging technique and the WinRHIZOPro System. Root pullout resistance and root tensile strength were estimated using vertical pullout and root tensile tests. Wind tunnel tests were executed to evaluate the wind erosion resistance using six-month-old plants. The results demonstrated that the growth performance and root functional traits of S. spontaneum are superior to those of A. formosana and P. australis. Additionally, the root anchorage ability and root tensile strength of S. spontaneum plants are notably greater than those of A. formosana and P. australis plants. Furthermore, the results of the wind tunnel tests showed that the wind erosion resistance of A. formosana is remarkably higher than those of S. spontaneum and P. australis. This study demonstrates that A. formosana and S. spontaneum are superior to P. australis, considering root traits, root anchorage ability, root tensile strength and wind erosion resistance. Taken together, our results suggest that S. spontaneum and P. australis are favorable for riverbed planting, while A.formosana is applicable for riverbank planting in estuary areas. These results, together with data on the acclimation of estuarine grasses in waterlogged soils and brackish waters, provide vital information for designing planting strategies of estuary grasses for the ecological engineering of estuarine sand drift control.