Impact of stand density on soil quality in Chinese Fir (Cunninghamia Lanceolata) monoculture

Abstract

It is known that forest management practices and land use affect soil quality worldwide. This study was conducted to assess the potential effects of stand density on soil quality in Chinese fir plantations. Low- (1,450 trees/ha with 2.36 × 2.36 m spacing), intermediate- (2,460 trees/ha with 1.83 × 1.83 m spacing), and high-density (3,950 trees/ha with 1.44 × 1.44 m spacing) stands in a 10-year-old Chinese fir monoculture plantation were examined, and different soil quality indicators were measured. The results indicated that stand density affected nitrogen (N), phosphorous (P), and magnesium (Mg) content, whereas potassium (K) and calcium (Ca) were not affected. Total N and total P contents were higher in the low-density stands, whereas total Mg was higher in the intermediate-density stands. Available N was higher in the low-density stands, whereas available P was higher in the intermediate-density stands. No significant difference was observed in the contents of available K, total K, and total Ca among all densities. Soil organic matter was significantly higher in the intermediate-density stand than in the high- and low-density stands. Soil bulk density increased from the surface layer to the 40-60 cm soil layer. Soil pH was lowest in the surface layer of soils of all three densities and increased from the 0-20 cm layer to the 20-40 cm layer; however, it decreased from the 20-40 cm layer to the 40-60 cm layer. Soil pH differed significantly between soils of different densities but remained within an optimum range (4.1-4.5) for Chinese fir plantations. Soil moisture content was significantly higher in the high-density stand than the other stands. The observed effects of stand density on soil quality may be useful for policy makers and forest managers to implement improved forest conservation practices for preserving soil quality and stand production.