Objective In this study, the stoichiometric characteristics of litter and its response to stand characteristics, topographic factors and species diversity will be revealed in Pinus massoniana plantations in karst areas.

Method Middle-aged forest, near mature forest and over mature forest of P. massoniana plantation were used as research objects, organic carbon (OC), total nitrogen (TN), total phosphorus (TP), the stoichiometric characteristics and influencing factors were analyzed through the combination of field investigation and laboratory test.

Result (1) The average contents of OC, TN and TP in the litter of P. massoniana plantation in the study area were 346.92, 11.22 and 0.21 g/kg, respectively, and the average values of C/N, C/P and N/P were 31.31, 4 296.96 and 148.73, respectively. (2) There was no significant difference in OC, TN content and C/N of litter among different age groups (p > 0.05), and the content of TP increased first and then decreased with the growth of forest age (p < 0.05). The C/P and N/P of middle-aged forest were significantly higher than those of near mature forest and over mature forest (p < 0.05). (3) Significant positive and linear correlations were found between TN and TP (p < 0.001), significant linear correlations were observed between C/N and OC content, C/N and TN content, but significant power relationship was observed between C/P and TP content, N/P and TP content. (4) The TP content of litter was mainly affected by the Simpson index of shrubs and arborous layers, N/P and C/P were mainly influenced by Simpson index, Margalef index, Pielou index of shrubs and the density of plantation.

Conclusion The TP content, C/P and N/P of the litter are significantly different among varied age groups of P. massoniana plantations, and the diversity of arborous and shrubs is the main factor affecting OC, TN, TP and their stoichiometric ratio of the litter of P. massoniana plantation in the karst area of southwestern China.