Root biomass distribution of planted Haloxylon ammodendron in a duplex soil in an oasis: desert boundary area

Abstract

AbstractDuplex soils, consisting of a sandy surface soil (A‐horizon) and silty‐clay subsoil (B‐horizon), occur in a boundary area between oasis and desert in northwestern China and create a challenging habitat for restoration of plant growth. We conducted an experiment in a 10‐year‐old H. ammodendron plantation forest to determine the influence of physical properties of duplex soil on water infiltration and plant root growth. We used a trenching method to assess root biomass, and classified roots into two diameter classes: fine (<2 mm) and coarse (>2 mm). Following a 26.7 mm rain event, water infiltrated to the B‐ horizon; further deep percolation was hindered by low hydraulic conductivity, so that B horizon remained at high available soil moisture for an extended period of time. Root biomass increased rapidly in, or very close to the B horizon, especially for coarse roots. The subsoil formed a barrier to root penetration, but may also reflect the accumulation of water resources at the boundary between the A‐ and B‐horizon. Shoot growth and root distribution, shrub height and canopy area, and total root biomass were negatively correlation with depth to the B horizon, and that was reflected by quadratic functions. We conclude that the texture and structure of duplex soils influenced the soil environment for water infiltration and storage, indicating that the B‐horizon underlying sand in duplex soils is advantageous for the growth, and development of planted sand‐stabilizing vegetation. These results have important implications for sustainable development of sand‐fixing plantations in desert ecosystems.