Effects of soil crusts on the population distribution pattern of Limonium aureum in degraded Haloxylon ammodendron forests

To determine the effect of subsoil crusts on the distribution pattern of Limonium species in Haloxylon ammodendron forest, we chose L. aureum in a degraded H. ammodendron forest in Shiyang River basin as the research subject and determined the distribution pattern of L. aureum in the no crust stage (NCS), physical crust stage (PCS), and biological crust stage (BCS). The results showed that (1) the formation of soil crusts played a positive role in seed capture, germination, and settlement of L. aureum. Owing to the high ground mobility, it was difficult to obtain suitable germination conditions for seeds in non-crusted areas. Therefore, the population density of L. aureum in the NCS plot was significantly lower than that in the PCS and BCS plots (P < 0.05). (2) The height of L. aureum was not significantly different in the different soil crust types (P > 0.05). The average crown width of L. aureum in the PCS and BCS plots was significantly lower than that in the NCS plot (P < 0.05), whereas the population coverage of L. aureum in the PCS and BCS plots was significantly higher than that in the NCS plot (P < 0.05). Soil crust formation caused a redistribution of precipitation, which affected the growth of the population. (3) The population distribution of L. aureum in the NCS plot was sparse and uneven, and was the small plant type. The population distribution of L. aureum in the PCS and BCS plots was dense, forming a stable population, and the number of large plants was higher than the number in the NCS plot. (4) In the NCS, PCS, and BCS plots, the spatial distribution pattern of the population of L. aureum showed aggregation distribution; however, the aggregation intensity was different. The order of the aggregation intensity was as follows: BCS > PCS > NCS. Thus, the crust type influenced the basic characteristics, age structure, and spatial distribution pattern of the L. aureum population significantly. Crust formation promotes the settlement and distribution of the L. aureum population. The population density is large and relatively stable. The study provides a reference for the restoration of artificial vegetation of degraded H. ammodendron.