Two psammophile-dominated Artemisia semi-shrubs (A. wudanica and A. halodendron) and two annual Artemisia forbs (A. sieversiana and A. scoparia) bear significant ecological functions in Horqin Sandy Land, but systematical information on their achenes' germination is very limited. A set of studies were conducted to evaluate seed germination responses to storage periods and methods, different temperatures, lights conditions and sand burial depths, in order to determine inter-specific germination variation in the same genus and to explain how the species adapt to its microhabitat. Fresh achenes of A. wudanica, A. halodendron and A. sieversiana showed high germination capacities, but those of A. scoparia had obvious innate dormancy, which could be broken by chilling and dry storage, especially long-term dry storage. Achene germination of the two semi-shrubs preferred lower temperature fluctuation (10 to 22ºC) and was not sensitive to light. But the two annuals preferred higher temperature fluctuation (34 to 22ºC) and strong light for their achene germination. These four Artemisia species showed similar responses to sand burial, i.e. soil surface was most favorable for seedling emergence, and the deeper the sand burial, the fewer the seedling emergence. For the two semi-shrubs, their microhabitats are sand dunes with high temperature and intense light, which are not favorable for germination and seedling survival. Only rainfall contributes to temporary decrease of temperature and then triggers germination. We deduced that germination is not the main but a supplementary reproductive mode for the two semi-shrubs in sand dunes. For the two annuals, achene germination is the only reproductive mode, but different responses have been developed for microhabitat adaptation. For A. sieversiana, high germination capacities in wide temperature ranges and all light conditions could improve its competition and advancement in the wettest microhabitats. For A. scoparia, obvious innate dormancy of fresh achenes and germination inhabitation under unfavorable conditions are important adaptation to environmental disturbances.
Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. This paper aims to explain the qualitative and quantitative relationships between species diversity pattern and grain size (i.e. size of the sampling unit), and species diversity pattern and sampling area, and to analyze species diversity variability on active sand dunes in the Horqin Sandy Land, northeastern Inner Mongolia, China. A 50 m×50 m sampling plot was selected on the windward slope, where the dominant species was annual herb Agriophyllum squarrosum. Species composition and abundance at five grain sizes were recorded, and the species-area curves were produced for thirteen grain sizes. The range of values for species abundance tended to increase with increasing grain size in the study area, whereas, generally, species richness did not follow this rule because of poor species richness on the windward slope of active sand dunes. However, the homogeneity of species richness increased significantly. With the increase in sampling area, species abundance increased linearly, but richness increased logarithmically. Furthermore, variograms showed that species diversity on the windward slope of active sand dunes was weakly anisotropic and the distribution pattern was random, according to the Moran Coefficient. The results also showed that species richness was low, with a random distribution pattern. This conflicts with the results of previous studies that showed spatial aggregation in lower richness in a sampling area within a community and inferred that the physical processes play a more important role in species diversity than distribution pattern on active sand dunes. Further research into different diversity patterns and mechanisms between active sand dunes and interdune lowlands should be conducted to better understand biodiversity conservation in sand dune fields.
We simulated P leaching on active dune (AD), semi-stabilized dune (SSD) and stabilized dune (SD) under 140, 700 and 1400 mm of rainfall in Horqin Sandy Land Inner Mongolia, China. The results showed that the available phosphorus (AP) pool decreased by 5–50% in topsoil (0–10 cm), and increased by -5–220% in subsoil (10–20 cm) in AD, SSD, and SD soil. The total P (TP) pool in topsoil (0–10 cm) decreased by 1.8–5.0%, and increased by -5–4.6% in subsoil (10–20 cm) in AD, SSD, and SD soil. The P loss in the soils (0-20 cm) was 0.5–4.5% in AD, SSD, and SD soil. These data indicated that significant downward movement of P occurred during soil leaching. And, the movement of soil P by leaching can cause P loss and changes in vertical distribution of P. Moreover, the difference in P concentration, drawn up by plant roots, between topsoil and subsoil can buffer the P loss at the start of leaching. Therefore, vegetation restoration is essential to reduce P loss in sandy lands.
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