Study On Root Distribution And Habitat Flexibility Of Artemisa Ordosica In Mu Us Sandy Land

Mu Us Desert is one of the largest sandy areas in China, where the seldom precipitation and little soil water content both go against growth of the majority of sandy plant. It is the basic reason of sparse vegetation and simply species for sandy areas. To master the spatial-temporal variability of soil water of different sandy land types, vertical distribution of root, and relationship of soil water content and plant root growth, it plays an important role for the vegetation recovery and regeneration, the choice of suitable species, and improving afforestation survival, preserving rate, and benefit. In order to characterize the root distribution, physiology traits and its relationship with soil water of the dominant species Arternisia ordosica, the spatial-temporal root distribution of the Arternisia ordosica in moving dune, semi-fixed dune, and fixed dune of Mu Us sandy land were studied by embedding reticular bag soil core, layered excavating, and analysis system of root. Meanwhile, the dynamic change of soil water were also studied by neutron probe and drying method for a long period. The results showed that:(1) The range of Arternisia root biomass were varied by the ages and the distributions in the soil layers were different. The root biomass was increased by the ages, and come to the maximum in a certain period of time, then gradually decreased and kept to stable. The roots extended to the deeper soil along with the age increased, and the root biomass exponential declined with the depth of soil. The roots biomass of Arternisia in the age of one to five years were mainly in 0～60 cm soil layer, which percentage were 99.06%, 97.71%, 94.31%, 93.82%, 84.35%. In 0～20cm, the percentage of the root biomass of total root (PBT)reduced by the ages. In 20～60cm, the PBT was increased at first then decreased.(2) The variation and the distribution of the root length were similar to the biomass, and the root length difference in different soil layers increased with the ages, but the root length exponential declined with the depth of soil.(3) Specific root length (SRL) can reflect the characteristics of habitat flexibility of plants. The variation of SRL of Arternisia showed that the means of SRL decreased with the ages in 0～200 cm soil layer and the one year was the largest in five age stages. The five year input the most carbon but has the least SRL. The efficiency of inputting carbon for root length construction decreased with the ages increase. Although in the same age, the SRL was different in different soil layers. It was indicated that the plants had a high plasticity to their living environment and reflected the difference among the soil conditions.(4) There are difference in soil water content of different type dunes along with the soil depth. In 0～60cm soil layer, the soil water content moving dune, semi-fixed dune and fixed dune respectively for 8.08%, 8.00% and 8.03%. The differences were not significant in this soil layer. In 60～200cm soil layer, the soil water content moving dune, semi-fixed dune and fixed dune respectively for 8.65%, 8.57% and 8.53%. The differences was significant more than 60cm. In 60～140cm soil layer, he soil water content moving dune, semi-fixed dune and fixed dune respectively for 8.76%, 8.62% and 8.54%. The differences were significant significant in 60～140cm. Because that the evaporation was much larger than the precipitation in desert area and comprehensive effect of the sandy soil characteristics, superadded the transpiration of the plants, the performance of soil water content was moving dune > semi-fixed dune> fixed dune.(5) The surface and position of slopes had obvious impact on the soil water content. The soil water content in most leeward side of fixed and semi-fixed dunes were higher than those in windward side, however, moving dunes were just the opposite. The soil water content deceased with slope position rise, and the soil water content among dunes was significant higher than that on the top of dunes. Compared with the fixed or semi-fixed dunes, the lowland among moving dunes showed high soil water content, and this explained that plant transpiration and soil evaporation of fixed dunes were larger than the moving dunes. As the thinning of sand dunes, there was humified soil at 140cm depth of dune bottom and the soil water content rapidly increased, but due to the thickness of sand layer, those in leeward side of moving dune were not the case.(6) As the changes of climate, the sandy soil water content showed obviously seasonal variability. In three different types of dunes, the largest of soil volumetric moisture content was moving dune, followed by semi-fixed dune and fixed dune. The largest variation of soil water content was fixed dune and the smallest was moving dune, and this explained that plant transpiration and soil evaporation of fixed dunes were larger than the moving dunes. Because that rainfall mainly concentrated in the spring and autumn, the soil water content was higher in May, September and October, and it was also indicated that the rainfall was the mainly supply for soil water content. Due to the littleness of rainfall and high evaporation in July and August, the soil water content was low. Therefore, the spring or autumn, the period with higher soil water content, was the preference for artificial afforestation in arid desert area.(7) The vertical change of soil water content and vertical change of roots growth of Arternisia ordosica is closely related. Soil water content influence the growth and distribution of root system. At the same time, because soil water uptake with root systems, root system also affects the redistribution of soil water content.