Effects of simulated litter addition, and nitrogen and phosphorus deposition on ecological stoichiometry of Pinus koraiensis litter

Objectives  We assessed the effects of litter quality, nitrogen and phosphorus addition, microclimate factors, precipitation chemistry and topography on ecological stoichiometry of Pinus koraiensis litter to provide scientific basis for management of Pinus koraiensis forest.

Methods  We conducted a 712-day observation experiment in broad-leaved Pinus koraiensis mixed forest (natural forest) and Pinus koraiensis pure forest (plantation). After nitrogen and phosphorus addition and litter treatment, the contents of C, N and P in different litter layers and forest types, as well as the ecological stoichiometry of undecomposed layer (L layer), semi-decomposed layer (F layer) and humic litter layer (H layer) were analyzed.

Results  1) The differences in litter quality resulted in significantly different ecological stoichiometry of the litter layers. The fastest turnover of nutrients was found in the H layer but the C∶N, C∶P, N∶P in H layer were smaller than those in L and F layers. 2) The high-quality litter with complex composition inhibited N and P accumulation, but was beneficial to the deposition of C under N-P and litter addition. Although the low-quality litter with single composition produced C deposition under N-P and litter addition, the N and P addition promoted N and P enrichment. 3) Microclimate factors and precipitation chemistry were positively correlated with ecological stoichiometry, especially temperature, precipitation, and pH. 4) There were significant interaction effects of litter treatment, N-P deposition treatment, slope and temperature on ecological stoichiometry of litter.

Conclusions  This study reveales the eco-stoichiometric characteristics and seasonal variation trend of litter C, N and P in broad-leaved Pinus koraiensis mixed forest and Pinus koraiensis pure forest. We can infer that the litter decomposition in broad-leaved Pinus koraiensis mixed forest and Pinus koraiensis pure forest is mainly limited by P. At the same time, P element may be the limiting factor of Pinus koraiensis growth.