|Publication Type:||Journal Article|
|Year of Publication:||2008|
|Authors:||Longhi, D., Bartoli, M., Viaroli P.|
Decomposition rates of Phragmites australis, Carex riparia, Nuphar luteum and Salvinia natans and benthic processes were measured from December 2003 to December 2004 in a shallow wetland (Paludi di Ostiglia, Northern Italy) by means of litter bags and intact cores incubations. Decay rate was highest for N. luteum (k = 0.0152 d(-1)), intermediate for S. natans (k = 0.0041 d(-1)) and similar for P. australis (k = 0.0027 d(-1)) and C riparia (k = 0.0028 d(-1)). Benthic metabolism followed a seasonal pattern with summer peaks of O-2 demand and TCO2, CH4 and NH4+ efflux whilst soluble reactive phosphorus (SRP) fluxes were negligible also under hypoxic conditions, indicating that P was mainly retained by sediment. The initial C:P ratio was similar in N. luteum and S. natans (similar to 170) and significantly lower than that of P. australis and C. riparia (similar to 360). During the detritus decay P was progressively lost by N. luteum and S. natans tissues, whereas, after an initial leaching, it was probably re-used during the microbial decomposition of the more refractory P. australis and C riparia detritus. Nuphar luteum, A australis and S. natans had comparable initial C:N mass ratio (similar to 15), significantly lower than that of C riparia (similar to 26). The C:N ratio was rather constant for N. luteum (12.9 +/- 1.5)and S. natans (14.6 +/- 0.9), decreased slightly to below 20 for C. riparia and increased up to 30 for P. australis. Overall, differences among species were likely due to the recalcitrance of decomposing detritus, whilst process rates were controlled by limitation of microbial processes by nutrients and electron acceptor availability. (C) 2008 Elsevier B.V. All rights reserved.