[Nitrogen and phosphorus release from herbaceous vegetation under simulated inundation experiment of water-level fluctuation zone in the Three Gorges Reservior Area].

Nitrogen and phosphorus release from herbaceous vegetation of water-level fluctuation zone in the Three Gorges Reservior (TGR) area could become a crucial source which may deteriorate water quality of TGR. Stems and leaves of the dominant herbaceous plants from water-level fluctuation zone were collected and inundated in the laboratory for measuring nitrogen and phosphorus release along with decay process. Results show that: (1) The differences of initial carbon and nitrogen content among herbaceous plants of water-level fluctuation zone are remarkable, except intial phosphorus content. (2) The decomposition of vegetation under inundation causes the increase of pH, the decrease of Eh of the overlying water and the release of nitrogen and phosphorus. The release amount of total nitrogen (TN) and total phosphorus (TP) are (3.85 +/- 2.53), (1.33 +/- 0.73) mg x g(-1) respectively. The release process of TN and ammonia nitrogen (NH4(+) -N) shows a parabolic curve, whereas TP releases fits in a logarithmic curve. The average peak time of TN and TP concentration is in the 15th day of inundation, while NH4(+) -N is in the 33th day. The release amount and rate of nutrients follow the sequence in TN > TP > NH4(+) -N. The average loads of TN, TP and NH4(+) -N release from vegetation decay in three months' inundation are 22.4, 8.9 and 4.5 kg x hm(-2) respectively. (3) The lower initial C and higher initial N and P content of plant, make an advantage for nitrogen and phosphorus release when plants are inundated in flooding period of TGR.