The Phenotypic Responses Of Salsola Arbuscula And Zygophyllum Xanthoxylon To Strong Wind

Wind is an important ecological factor, seriously influencing the abovegroundgrowth and architecture of the plant. The plant can adjust the abovegroundarchitecture to change the capture of light and to regulate the resistance to the externalmechanical pressure. Salsola arbuscula Pall. and Zygophyllum xanthoxylon (Bge.)Maxim., two of native shrubs in Dabancheng, grow in the habitat with strong windand drought. However, theirs resistance capacity to wind has not been assessed. Weinvestigated the phenotype of S. arbuscula and Z. xanthoxylon under strong wind toknow how S. arbuscula and Z. xanthoxylon respond to wind disturbance in growthand architecture.1) Wind generators and pots were used to simulate, lasting for105and90days in2011and2012. The wind generators operated for6hours each dayfrom14:00to20:00. Four treatments in wind speeds0.3(control),3,7,12m/s weredesigned.2) The potted S. arbuscula and Z. xanthoxylon were exposed to two naturalwind regimes (from open and wind protected sites), lasting for90days in Dabanchengin2012.The height and the leaf area of S. arbuscula and Z. xanthoxylon in thewind-exposed site were reduced respectively, but the basal stem diameter wereincreased, compared with them from closed site. The number and diameter of S.arbuscula leaf from the open site were, on the average, greater than those sampledfrom the closed site. But the number and width of Z. xanthoxylon leaf from open sitewere lesser than those sampled from the closed site. The length and diameter of Z.xanthoxylon petiole from open site were reduced respectively, compared with themfrom wind-protected site. In the wind-exposed site, S. arbuscula showedasymmetrical canopy from windward to leeward, number of the first order branch wasincreased with wind load. In the wind-protected site, S. arbuscula showedsymmetrical canopy in four direction. The trunk angle to horizon, the branch and leafangle to trunk of S. arbuscula were reduced respectively, compared with them fromwind-protected site. While Z. xanthoxylon from open site did not have the first orderbranch, its trunk angle to horizon was reduced, but leaf angle to trunk was increased,compared with them from wind-protected site.In the experiment of simulated strong wind, S. arbuscula has the capacity tosignificantly reduce its exposed surface area and the aerodynamic drag in response tostrong wind disturbance, by reconfiguring the non-uniform canopy architecture topresent a streamlined shape to adapt the prevailing wind, and decreasing the angle ofthe primary branches and leaves. Z. xanthoxylon reduced the aerodynamic drag ofstrong wind by the way of increasing basal stem the diameter along the wind directionand flexility of the petiole, and another way of reducing height and branch and leavesexposed surface area to strong wind. The reducing extent of height, the length of theleaves, the trunk angle to horizon, the branch and leaf angle to trunk of S. arbusculawere greater than Z. xanthoxylon, which is propitious to reduce theirs exposed surfacearea. S. arbuscula had the second order branch under the wind speeds of7and12m/s,to brace and reduce impact with each other. However, Z. xanthoxylon had the shorterand thinner petiole benefit leaves swaying in the strong wind.In conclusion, this research shows that phenotypic plasticity of S. arbuscula and Z.xanthoxylon response to strong wind. It reflects that there are many adaptive mechanisms, by which these two species assure them can normally grow and survivein arid environment with strong wind, and have significant ecological consequences.All of these may be important reasons for S. arbuscula and Z. xanthoxylon to be theideal species for ecological reconstruction in environment with strong wind ofDabancheng.