Preservation of broadleaf species in Korean pine (Pinus koraiensis) plantations affects soil properties, carbon storage, biomass allocation, and available nitrogen storage

Abstract

We analyzed forest floor mass, soil properties, soil organic carbon (SOC) storage, soil available nitrogen (NO3–-N and NH4+-N) (SAN) storage, litter production and decomposition, tree biomass, and the growth rate of Korean pine ( Pinus koraiensis Sieb. et Zucc.) to determine the impacts of keeping broadleaf species in the Korean pine plantation on Korean pine growth and identify the interactions of plants and soil. Forest biomass and litter production were significantly higher in the broadleaf mixed Korean pine plantation (KBP) than in the pure Korean pine plantation (KP). Broadleaf species redistributed carbon from forest floor to mineral soil via its fast litter decomposition rate with the result of a smaller forest floor mass and a greater SOC storage in KBP than in KP. KBP had significantly higher SOC and SAN storages, SOC and SAN concentrations, and pH, and lower soil bulk density than KP. Such differences can be largely explained by the input of broadleaf litter into KBP. The Korean pine in KBP had a greater growth rate and allocated a smaller proportion of biomass below ground, indicating that the broadleaf species influenced the Korean pine growth and biomass allocation pattern by changing soil properties. There was a positive feedback among litter N release rate, SAN storage, and plant growth rates.