Effects of groundwater depth on soil environmental factors and root biomass of typical plant communities in sandy grassland

Evaporation is severe in arid and semi-arid areas, and vegetation growth in these areas depends on the groundwater supply. The growth of the underground part of vegetation is limited by the depth of the groundwater table. To determine if the underground part of vegetation (root biomass), growth environmental factors (soil nutrients and pH), and their relationship are affected by the groundwater table depth, a controlled experiment with an increasing groundwater table depth (0.5, 1.0, and 2.0 m) was conducted in Horqin sandy grassland. The results were as follows: 1) soil total nitrogen, total phosphorus, and pH increased as the groundwater table depth changed in the control tests, and there were significant differences among the treatments (P < 0.05). However, the soil organic carbon content showed a downward trend, and there was no significant difference among the treatments. The soil organic carbon, total nitrogen, and total phosphorus contents all decreased as the groundwater table depth increased, whereas the pH increased as the soil depth increased, but the difference was not significant. 2) The root biomass decreased as the soil depth increased at different groundwater depths. 3) Soil organic carbon, total nitrogen, and total phosphorus were positively correlated with the root biomass, whereas the pH was not negatively correlated with the root biomass. Therefore, this study shows that different groundwater table depth treatments have different effects on different soil nutrient types, but the groundwater table depth in Horqin sandy grassland will accelerate the loss of soil organic carbon, total nitrogen, and total phosphorus contents and the increase in root biomass.