In order to explore the seasonal variations of carbon (C)

nitrogen (N) and phosphorus (P) stoichiometric features in leaves of different natural secondary forests and understand the strategies of plant adaptation to the environment

we chose Piuns tabulaeformis and Quercus liaotungensis natural forests in Ziwuling Forest district as study area

and subsequently investigated their C

N and P stoichiometric parameters in leaves from April to October. The results showed: (1) Leaf C

N and P contents and stoichiometric ratios of Q. liaotungensis were 43.16%

2.10%

0.19% and 25.47

380.18

14.49

respectively

and the same parameters for P. tabulaeformis were 48.06%

1.15%

0.11% and 42.58

473.22

11.02

respectively. There were less seasonal dynamics in leaf C contents and more seasonal dynamics in leaf P contents than others through the whole growth season. (2) Leaf C content of P. tabulaeformis significantly decreased from April to June

then remained stable

but it significantly increased from August to October

which was almost equal to April; while leaf C content of Q. liaotungensis was almost constant. Leaf N content of P. tabulaeformis remained stable before June

then significantly decreased from June to August

then it significantly increased from August

and in October it was almost equal to April. Leaf N content of Q. liaotungensis significantly decreased from April to June

then remained stable

but it significantly decreased again from August and reached the lowest value in October. Leaf P content of P. tabulaeformis remained stable before August

then significantly increased and reached the maximum value in October. Leaf P content of Q. liaotungensis significantly decreased from April to June

then remained stable. The changes of C/N

C/P of two species were averse to their N

P content. Leaf N/P of P. tabulaeformis significantly decreased from April to June

then significantly increased

and it significantly decreased from August to October. The N/P of Q. liaotungensis increased significantly and reached the maximum value before June and then significantly decreased. (3) Factorial analysis showed that leaf C content and C/N mainly determined by tree species. For other parameters

they were mainly affected by the interaction between tree species and month. (4) Leaf C content of P. tabulaeformis significantly higher than that of Q. liaotungensis

however

leaf N content of P. tabulaeformis was significantly lower than that of Q. liaotungensis

therefore

leaf C/N of P. tabulaeformis was significantly higher than that of Q. liaotungensis. However

leaf N/P of Q. liaotungensis was significantly higher than that of P. tabulaeformis. There was no significant difference in leaf P content and C/P between these two species. The coefficient of seasonal variation of leaf N

P contents and C/N

C/P

N/P of P. tabulaeformis were smaller than those of Q. liaotungensis. The results could enrich the study of ecological stoichiometry in natural forests

and provide a theoretical basis for the forest restoration and management in the hilly and gully region of Loess plateau.