Heterotrophic soil respiration affected by compound fertilizer types in red pine (Pinus densiflora S. et Z.) stands of Korea

This study was conducted to evaluate the effects of fertilizer application on heterotrophic soil respiration (Rh) in soil respiration (Rs) components in red pine stands. Two types of fertilizer (N₃P₄K₁ = 113:150:37 kg·ha^-1·year^-1; P₄K₁ = 150:37 kg·ha^-1·year^-1) were applied manually on the forest floor for two years. Rs and Rh rates were monitored from April 2011 to March 2013. Mean Rs and Rh rates were not significantly affected by fertilizer applications. However, Rh in the second year following fertilizer application fell to 27% for N₃P₄K₁ and 17% in P₄K₁ treatments, while there was an increase of 5% in the control treatments compared with the first fertilization year. The exponential relationships between Rs or Rh rates and the corresponding soil temperature were significant (Rh: R² = 0.86-0.90; p < 0.05; Rs: R² = 0.86-0.91; p < 0.05) in the fertilizer and control treatments. Q₁₀ values (Rs increase per 10°C increase in temperature) in Rs rates were lowest for the N₃P₄K₁ treatment (3.47), followed by 3.62 for the P₄K₁ treatment and 3.60 in the control treatments, while Rh rates were similar among the treatments (3.59-3.64). The results demonstrate the importance of separating Rh rates from Rs rates following a compound fertilizer application.