Vertical distribution and seasonal variation of nitrogen, phosphorus elements in Spartina alterniflora wetland of Jiaozhou Bay, Shandong, China

In order to study the vertical distribution and the seasonal variation of N and P in Spartina alterniflora wetland of Jiaozhou Bay, soil samples in S. alterniflora wetland and bare flat in April, July, September, October, November and December 2015 were collected, and TN, NH -N, TP, AP, TOC, pH, salinity and water content were tested. The average values of soil TN, NH -N, TP and AP contents in S. alterniflora wetland were 0.396 g·kg , 12.14 mg·kg , 0.385 g·kg and 16.52 mg·kg respectively, while those in bare flat were 0.419 g·kg , 8.13 mg·kg , 0.423 g·kg and 19.57 mg·kg respectively. Generally, they decreased gradually with the increase of the soil depth (0-60 cm). The contents of N and P in S. alterniflora wetland had obvious variations with season. The maximum and minimum of soil TN contents in S. alterniflora wetland were in spring and autumn respectively, while the content of soil TN in bare flat decreased with the change of season. Compared with the bare flat, the content of TP in S. alterniflora wetland