Deposition is a phosphorus source for Fallopia japonica during early-stage primary succession

Phosphorus is a key plant nutrient linked to plant growth during the early stages of primary succession in volcanic soils. Available phosphorus is thought to include soil and atmospheric phosphorus, but it is not well understood. Here, we focused on deposition as a potential phosphorus source. We evaluated the contribution of deposition to phosphorus uptake and growth in Fallopia japonica, a key pioneer species of primary succession. When we experimented with growing F. japonica under field conditions, F. japonica not covered by a roof absorbed more phosphorus than that covered by the roof, suggesting the influence of total (dry + wet) deposition. Furthermore, we tested the effects of deposition by treating F. japonica seedlings with wet deposition or distilled water in six volcanic soils. Plants that received the wet deposition treatment exhibited higher phosphorus contents and growth rates than those treated with distilled water. The phosphorus from wet deposition and the phosphorus from soil contributed nearly equally to F. japonica development. Our findings suggest that F. japonica grows during primary succession and builds up the phosphorus cycle by absorbing a trace amount of phosphorus from deposition and volcanic soils.