Community Characteristics And Population Dynamics Of Artemisia Ordosica At Different Fixation Stages Of Dunes In The Mu Us Desert

The harsh habitat conditions in arid and semi-arid regions are disadvantageous for plant growth and survival, which influence the process of population growth, reproduction and survival directly. In-depth analysis of the relationships between the community characteristics and environmental factors during sand stabilization can provide important information related to the internal mechanism of the formation and maintenance of desert plant biodiversity in sand dune ecosystems.We choose a dominant shrub, Artemisia ordosica, at three stages of dune fixation:semi-fixed dunes (SF), fixed dunes (FD) and fixed dunes covered with microbiotic crust (FC), as the research object. We studied the community characteristics, species composition, relationships between plant and environmental factors and the changes in demography of A. ordosica by using canonical correspondence analysis (CCA) and integral projection models (IPM). The results showed that:(1) The mean height and coverage of plants increased with sand dune stabilization, while species diversity and richness increased initially and then reduced; The dominance value of typical steppe species increased significantly following sand dune stabilization and relations between species and samples in CCA ordination biplots showed that perennial grasses could invade the A.ordosica community on FC, indicating A. ordosica communities had tendency changing into typical steppe vegetation with the further fixation.(2) Correlation analysis and CCA revealed that slope, soil organic carbon and nutrient contents, proportion of fine soil particles, soil moisture, and thickness of biological soil crust were all highly correlated with vegetation characteristics. These environmental factors could explain 40.42% of the vegetation-environment relationships at the three habitats. The distribution of plant species was positively related to soil moisture in the SF dune. Soil moisture, soil nutrient, and fine particle contents mainly affected plants distribution in the F dune. In the FC dune, distribution of plant species was mainly affected by the thickness of biological soil crust and soil moisture.(3) Population growth rate (λ) declined substantially with dune fixation:from rapid expansion in semi-fixed dunes(λ=1.016-1.036) to moderate decline in fixed dunes with microbiotic crust (λ=0.763-0.783); Fast expansion in semi-fixed dunes is enabled by high seed production and effective recruitment, seedlings and small plants were critical for population growth in this condition, whereas moderate to large-sized plants were most important at later dune fixation stages, populations are maintained through frequent plant shrinkage.We conclude that:the relationship between environment and desert plant distribution patterns is a complex balance among varying dune fixation stages. So, the restoration of degraded dune ecosystem should be considering the habitat conditions and ecological needs; the adaptive changes in vital rates and life history traits of A. ordosica over the course of the dune fixation process may explain its dominance in the vast inland dune area of Mu Us desert; Integral projection models are highly appropriate tools, for analyzing the changes in demography of A. ordosica, to solve the limitation of previous research which required many years of observation of population change information.