Scant information is available on how soil phosphorus (P) availability responds to atmospheric nitrogen (N) deposition, especially in the tropical zones. This study examined the effect of N addition on soil P availability, and compared this effect between forest sites of contrasting land-use history. Effects of N addition on soil properties, litterfall production, P release from decomposing litter, and soil P availability were studied in a disturbed (reforested pine forest with previous understory vegetation and litter harvesting) and a rehabilitated (reforested mixed pine/broadleaf forest with no understory vegetation and litter harvesting) tropical forest in southern China. Experimental N-treatments (above ambient) were the following: Control (no N addition), N50 (50 kg N ha-1 yr-1), and N100 (100 kg N ha-1 yr-1). Results indicated that N addition significantly decreased soil P availability in the disturbed forest. In the rehabilitated forest, however, soil P availability was significantly increased by N addition. Decreases in soil P availability may be correlated with decreases in rates of P release from decomposing litter in the N-treated plots, whereas the increase in soil P availability was correlated with an increase in litterfall production. Our results suggest that response of soil P availability to N deposition in the reforested tropical forests in southern China may vary greatly with temporal changes in tree species composition and soil nutrient status, caused by different land-use practices.
Lu X, J Mo, FS Gilliam, H Fang, F Zhu, Y Fang, W Zhang, and J Huang. 2012. Nitrogen addition shapes soil phosphorus availability to nitrogen addition in two reforested tropical forests in southern China. Biotropica 44:302-311.