Fertilization and watering are important nursery cultural practices for seedling production, though few studies have investigated the combined effects of fertilizer and watering rates on nursery attributes and field performance of container-grown pine seedlings. Four subirrigation rates ranging from 55 to 85 per cent gravimetric water content (θ_g) and three rates of controlled-release fertilizer (CRF) from 50 to 150 mg N·seedling⁻¹ were examined on Pinus tabuliformis in this study. Seedling attributes were assessed at the end of the nursery growing season. Field performance was monitored over four years. In the nursery, seedling shoot growth and N loading increased with CRF and subirrigation rates. Root mass, and total P and K content declined at 150 mg·N·seedling⁻¹ rate when combined with 55 or 65 per cent θ_g. After field planting, initial seedling attributes, especially root mass and plant P and/or K content, strongly affected seedling survival and growth. Maximum field survival and the largest seedlings were achieved at the combined rates of 100 mg N·seedling⁻¹ CRF and 75 per cent θ_g after four years. We concluded that optimal fertilization and irrigation rates should be considered together to produce P. tabuliformis container-grown seedlings with desirable seedling attributes for field performance.

Changes in forest stand structure may alter the activity of invertase, urease, catalase and phenol oxidase after thinning Pinus tabuliformis (Carriére) plantations in Yanqing County of Beijing, China. We examined changes in these soil enzymes as influenced by time since thinning (24, 32, and 40 years since thinning) for 3 seasons (spring, summer and autumn) following harvesting at two depths in the mineral soil (0–10 cm and 10–20 cm). Invertase and urease increased significantly with time since thinning. Catalase activity was highest in the 24-year-old stand and there were no statistically significant differences between the 32- and 40-year-old stands. In addition, maximum invertase, urease, catalase, and phenol oxidase activities occurred during the summer; minimum activities occurred in autumn. Invertase and urease were positively correlated with each other, as were catalase and phenol oxidase. Most soil enzyme activity was higher in the 0–10 cm layer than at the 10–20 cm depth. As time from thinning increased, differences among soil depth became less significant. These results suggest that seasonal changes of these enzymes have different roles, as the time since thinning and thinning treatments may have both short- and long-term impacts on soil microbial activity.