Abstract:

Aims Vegetation and soil surveys were conducted in the summer of 2004 to study the relationship between vegetation types and soil of inter-dune lowland of Otindag sand land. Of 102 vegetation samples collected, 99 were herb-dominated, the others shrub-dominated. We analyzed soils for total nitrogen, soil organic matter, soluble sodium, soluble potassium and pH. Vegetation samples were classified based on species composition and species functional groups. We used detrended canonical correspondence analysis (DCCA) to determine the main environmental factors related to the distribution of plant communities.

Methods The 102 samples were classified into twenty-eight groups dominated by Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis, A. scoparia, A. frigida, Carex duriuscula, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Leymus chinensis, L. secalinus, Bromus inermis, Saussurea amara, Potentilla tanacetifolia, Achnatherum splendens, Iris lactea, Salix microstachya, Phragmites australis, Calamagrostis epigejos, Potentilla anserine, Halerpestes ruthenica, Puccinellia tenuiflora, Scirpus tabernaemontani and Suaeda glauca.

Importunt findings The Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis and A. scoparia associations are mostly distributed on sites often covered by quicksand. The level of the groundwater is low, the lixivium of the soil is neutral and the average soluble K⁺, Na⁺, total nitrogen and organic matter are low. Artemisia frigida, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Potentilla tanacetifolia, Leymus secalinus, Carex duriuscula and L. chinensis associations are rooted mostly in stable sand, where soil water, organic matter and total nitrogen are high. Bromus inermis, Saussurea amara, Puccinellia tenuiflora, Phragmites australis and Potentilla anserine associations grow in wet sites, where organic matter and total nitrogen are relatively high. Achnatherum splendens, Iris lacteal, Calamagrostis epigejos, Salix microstachya and Halerpestes ruthenica associations are on saline sites that have high groundwater and alkalinity. The Suaeda glauca association occurs in a highly saline lake, where water and salinity levels are very high. The Scirpus tabernaemontani association occurs in a marsh. The first DCCA axis denoted gradients in ground water level (GWL) and factors related to ground water level such as pH, soluble sodium and soluble potassium. The second axis reflected gradients of total nitrogen and soil organic matter. The third axis reflected a pH gradient. Ground water level, pH, soluble sodium, soluble potassium, total nitrogen and soil organic matter significantly correlated with the distribution of plant communities.

Key words: Otindag sand land, plant community, ordination