Morphological Characteristics Of Artemisia Ordosica Nebkhas And Their Physicochemical Properties At Different Evolvement Stages

The formation and evolvement of nebkhas, one of common wind-accumulated landforms in arid and semiarid regions, were inextricably connected with the process of land desertification. However, the characteristics of soil physical and chemical properties at different evolution stages of nebkhas is still unclear.A. ordosica nebkhas, widely spread at the study area of Yanchi research station in the Mu Us Desert, were selected as the research objects to be investigated their morphological characteristics, such as length, width, height and coverage. Based on it, the nebkhas evolution were divided three stages: developing stage, stabilizing stage and degrading stage, and each A. ordosica nebkhas at different evolvement stages sampled of soil in different habitat (inside, edge and outside of canopy projection area). The effects of morphological characteristics on soil physical and chemical properties were analyzed. The main conclusions are as follows:(1) A. ordosica nebkhas of research area were mainly at developing and stabilizing stages. The shrub length and nebkhas length, width significantly increased with the nebkhas evolvement, while the shrub height kept unchanged. There were good relationships among morphological parameters of A. ordosica nebkhas. Meanwhile the morphological parameters of A. ordosica were significantly correlated with that of nebkhas at developing and stabilizing stage, which all showed a significant liner relationship of shrub length and nebkahs length, shrub width and nebkahs width, shrub crown area and nebkhas basal area.(2) The fertile island were found under the canopy of A. ordosica nebkhas. Different evolution stages of A. ordosica nebkhas owned different magnitudes of physical and chemical properties. The enrichment ratio of stabilizing stage were stronger than developing stage and degrading stage. The effective enrichment ranges of stabilizing stage were from 67.6 cm to 107 cm, which were less than shrub and sand radius. So the fertile island range of A. ordosica nebkhas was no more than its size.(3) Soil fractal dimensions were significant positive linear correlation with clay, silt, soil organic matter, total nitrogen, total phosphorus and electrical conductivity, but showed a significant negative linear correlation with sand. Furthermore, Soil fractal dimensions were stronger relation with soil particle composition than soil nutrients.Our results indicated that the A. ordosica nebkhas evolvement was influenced by environmental factors and the coordinated effect between canopy and nebkhas, which made the nebkhas morphological characteristics significant differences among three evolvement stages. The evolvement process of A. ordosica nebkhas improved soil particle composition slowly, but had a positive effect on soil nutrients enrichment. Thus, soil fractal dimensions as a composite indicator on soil fertility had limited behaviors on small spatial scale. Therefore, this paper provides an important theoretical basis of monitoring and evaluating land desertification, and protecting of the regional ecological construction.