Effects of Different Forest Types on Stoichiometric Characteristics of Carbon, Nitrogen, and Phosphorus in Tropical Soils, China

The stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) in soil can directly reflect the level of soil fertility. In this study, a secondary forest, two kinds of plantation forests (Dacrycarpus imbricatus and Pinus caribaea Morelet), and a primary forest in tropical areas were selected for soil sample collection and analysis. We found that the soil [leucine aminopeptidase (LAP) + beta-N-acetylglucosidase (NAG)]/acid phosphatase (APho) value was less than 1, indicating that there was P limitation. In addition, we also found that compared with primary forest, the beta-glucosidase (BG) activity and (LAP + NAG) activity of the secondary forest were lower, and the microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents were higher. The contents of total nitrogen (TN) and MBN in the Dacrycarpus imbricatus forest soil were significantly higher than those in the primary forest, but the activity of (LAP + NAG) was lower. The structural equation model showed that the factors that significantly affected the total nutrients were the available nutrients (0.396**) and the enzyme activities (0.600**). For the long-term requirements of sustainable development, ecological adjustment and soil nutrient optimization of plantations should be carried out scientifically.