Changes of soil hydraulic properties under early-stage natural vegetation recovering on the Loess Plateau of China

• Early-stage vegetation recovering increases soil bulk density.
• Early-stage vegetation recovering decreases soil porosity and hydraulic conductivity.
• It takes at least 20 years to reverse the decreasing trend of hydraulic conductivity.

The changes of soil hydraulic properties under early-stage (from several years to a few decades) natural vegetation recovering are not well understood in semiarid zones. We hypothesized that early-stage vegetation recovering can change measurably soil hydraulic properties and this would behave differently from long-term (from several decades to hundreds of years) vegetation recovering. This study investigated the dynamics of soil hydraulic properties under natural vegetation recovering of different ages (1, 5, 9, and 16–20 years) as compare to cropland and 30-year-old secondary grassland (two controls) on the semiarid Loess Plateau. The hydraulic properties included dry bulk density, total porosity, and near-saturated hydraulic conductivity at the potential of − 0.5, − 1, − 3 and − 5 cm of water. The results showed that the increases of vegetation species, coverage and aboveground biomass did not improve soil hydraulic properties. Specifically, dry bulk density increased while total porosity and near-saturated hydraulic conductivity at various potentials decreased with the increase of abandonment years. Moreover, we found that it would take at least 20 years to reverse the decreasing trend for soil hydraulic conductivities. These results suggest that vegetation recovering may not necessarily ameliorate soil hydraulic properties.