Abstract:

Ammopiptanthus mongolicus, which is an endemic and endangered species in China listed in the Red Data book, is a type of evergreen broad-leaved shrub in dry deserts of Asia. A. mongolicus is distributed mainly in the Alashan region of Inner Mongolia, but, for unknown reasons, the range of the population has been declining. We studied the distribution patterns and characteristics of A. mongolicus as a preliminary step in understanding the dynamic changes of the population and community and the factors causing the population decline. In Alashan Zuoqi, 36 quadrats (20 m×20 m) and 150 grids (5 m×5 m) were set up at 3 sites (Dongqingliang, Sumutu and Luanjingtan). There were at least 12 quadrats and 50 grids in every plot. The distribution patterns, stand density characteristics, morphological characteristics, and dynamic changes of theA. mongolicus populations at the 3 sites were compared. The results showed that A. mongolicus populations formed different distribution patterns under environmental conditions. The population was distributed evenly on flowing-sand or semi-fixed windy sand but was distributed contagiously on ancient riverbeds or stone slopes caused by seasonal floods. Individuals of A. mongolicus had different morphologies based on the population density and environment characteristics. On flowing-sand, individuals had shorter heights and smaller diameters but the relationship between height and width was not significant (R₁=0.096). There was a negative relationship between population density and the height and diameter of individuals in the population on flowing-sand (R₂=-0.214, R₃=-0.339). Individuals growing on semi-fixed windy sand and stone slopes had significantly greater heights and diameters, but there was no significant relationship between population density, and the diameter and the height. On stone slopes, the relationships between individual diameters and the heights were not significant (R₁ = 0.886), and there were no significant relationships between population density and height and width (R₂ = 0.089, R₃= 0.055). The densities of A. mongolicus populations were the highest at the flowing-sand site and the lowest at the stone slope population where seasonal floods occurred. Populations of A. mongolicus had different age structures at the different sites. At the flowing-sand site, there were even numbers of mid- to old-aged individuals but few young individuals, indicating that the population was senescing. At the semi-fixed windy sand and stone slope sites, there were also very few young individuals, and the number of individuals in the different age classes was distributed very unevenly. All three populations had limited the regeneration questioning the long-term viability of these populations.

Key words: Population, Ammopiptanthus mongolicus, Environmental heterogeneity, Distribution pattern, Endangered species