Responses of N and P stoichiometry on mulching management in the stand of Phyllostachys praecox

To approach the impact of intensive and mulching management on nitrogen (N) and phosphorus (P) concentration and the ratio of N:P in soil and bamboo leaf, and clarify the degradation mechanism of Phyllostachys praecox plantation, the concentration of N and P elements in soil and leaf of Ph. praecox as well as its stoichiometry from bamboo stand with different mulching management treatments (6a, 3a and CK) were analyzed, and this research will provide theoretical guidence for regeneration of degraded bamboo plantations. The results showed that with soil depth increasing, soil N, P concentration among soil layers decreased. While with the time of mulching management extending, the concentration of N and P in soils increased significantly, and the ratio of N:P in soil 0--20cm increased significantly for mulching management stands; and N, P contents were enriched in 0--20cm soil layers. However N decreased significantly in leaf and P decreased much significantly for leaf in stands of 3a and 6a. The ratio of N:P was 14.05--18.39 in Ph. praecox leaves, and increased in 3a and 6a, which indicated that the function of P as key factor to limit the growth was enhanced. Furthermore the ratio of N:P in leaves had positive significant correlation with soil P content, and was negatively significant correlation with soil N:P ratio and P content in leaves, but had no significant correlation with soil N concentration. Thus it was concluded that with the time of mulching management extending, the coefficient between soil N and soil P, and the coefficient between leaf N and leaf P both decreased. The changes of soil N, P stoichiometry were caused by long-term mulching management which led to enhance the function of P as limit factor, make imbalance of the relationship between N and P, and inhibit absorption of N and P by bamboo leaf, which might be the main reason causing bamboo plantation degradation.