关键词: 几何平均直径, 分形维数, 甘肃引黄灌区, 耕作方式, 平均重量直径, 土壤团聚体

Abstract: Seed dispersal is an important pathway for the invasion of alien invasive plants. A clear understanding of dispersal mechanism is the basis for more effective prevention and ecological management of invasive species. Based on the analysis of the main parameters influencing the dispersal process by wind, we examined the effects of those parameters on different diffusion processes, summed up the influencing parameters which should be chosen in the simulation process of different diffusion, and explained the calculation of these parameters. Specially, we introduced the excellent simulation models of dispersal by wind and analyzed the selection basis of simulation models of dispersal in combination with the characteristics of invasive plants. Among all the influencing parameters, the height of seed release and the horizontal wind velocity have direct and obvious effects on the dispersal process by wind. For invasive herbs and shrubs, the height of plants in the invasive area is an important parameter that must be concerned. In the study of long distance dispersal, the effects of turbulence caused by leaf and horizontal wind profile within and above the canopy should be considered for trees and large shrubs. For small shrubs and herbaceous plants, the impacts of rising warm air mass caused by surface temperature should be concerned. Among the simulation models, the 2Dt model and the mixed Weibull model can more effectively describe the dispersal curves of the proximal and distal diffusers of the dispersal kernel. For more detailed selection of long-distance dispersal simulation models, it is necessary to consider different atmospheric turbulence types, disperser size, vegetation type, dispersal kernel dimension, and simulation accuracy requirements.

Key words: tillage method, Gansu Yellow River irrigation area, soil aggregate, fractal dimension, geometric mean diameter, mean weight diameter