Effects of afforestation density on species diversity and soil physical properties under Caragana korshinskii plantations.

[Objective] This study explored the effects of stand density of Caragana korshinskii plantation on species diversity and soil physical properties of herbaceous communities in sandy areas and determined the optimal stand density to provide references for better ecological service function. [Method] In Dalat Banner plantation of Ordos in the middle of Kubuqi Desert, Caragana korshinskii plantations with same site conditions, similar age and different stand densities were selected as the research objects. Woodlands with stand densities of 2 880-3 200 plants/hm² (I), 1 800-2 000 plants/hm² (II), 1 080-1 200 plants/hm² (III) and 720-800 plants/hm² (IV) were selected and compared with bare sandy land (CK). Species diversity of understory was characterized by herb community diversity.Height, cover and canopy width of plants in different stands were recorded.Soil water content, volume mass, field water capacity and total porosity were measured at soil layers of 0-20, 20-40, 40-60 and 60-80 cm by five-point sampling method.Correlations between plant community species diversity and soil physical properties were analyzed by redundancy analysis, and the principal components were used to evaluate Caragana korshinskii plantations. [Result] (1) There were 20 species of herbaceous plants, mainly Compositae.With the decrease of stand density, the Simpson, Shannon-Wiener and Margalef indices of herbaceous communities under Caragana korshinskii stand first increased and then decreased, and the order were in the order of III>IV>II> I>CK, while the Peilou evenness index showed no significant difference from CK. (2) Soil water content, total porosity and field water capacity of Caragana korshinskii plantation reached the peak values of 5.10%, 30.77% and 19.16% at density III.There was no significant difference in soil volume and mass among different plots (P>0.05). There were significant differences in soil moisture content between 0-40 cm and 40-80 cm soil layers (P<0.05).With the deepening of soil layer, volume quality of soil increased. (3) There were certain correlations between species diversity indices and soil physical properties in each density plot. (4) Comprehensive evaluation showed that plantations were in the order of III (2.276) > IV (1.261) > II (0.294) > I (-0.815) > CK (-3.017). [Conclusion] 1 080-1 200 plants/hm² was the appropriate density for the restoration of vegetation and soil physical properties of Caragana korshinskii plantation in the study area. [ABSTRACT FROM AUTHOR]