N and P balance from catchments with different land cover, and exportation of nutrients during storm events, in south central Chile

Carlos Oyarzun1, Pedro Herve-Fernandez
1 Ciencias Ambientales y Evolutivas, Universidad Austral de Chile

P 7.15 in Controls of dissolved organic matter fluxes in ecosystems

Poster Session 1 on Monday, 16:30-18:30

Stream nutrient loads are heavily dependent on catchment vegetation. Alteration of canopies and the soil under it, have a significant impact on nitrogen (NO3--N; NH4+-N; DON and TDN) and phosphorus (PO43+-P and TDP) reaching the stream.

The objectives of this study were: (i) to determine changes in the chemical composition of bulk precipitation while passing through canopies, (ii) to determine the annual retention of N and P and, (iii) to determine relationship between N and P export and discharge on each different vegetational land cover: native evergreen (NE); native deciduous (ND) and exotic plantation of Eucalyptus globulus (EG). We collected 36 rainfall events during the period June 2009 – March 2011 in EG and NE, 23 rainfall events during the period October 2009 – March 2011 in ND and 10 rainfall events during the period March – November 2013 in old-growth native forest.

ND forest showed the highest canopy enrichment for throughfall, while EG showed the minimum. TDN annual retention were 0.58; 0.9 and -4.79; while net annual fluxes (in kg N ha-1 yr-1) were 1.43; 9.31 and -7.14 for NE, ND and EG, respectively. TDP annual retentions were 0.7; 0.96 and -1.44; while net annual fluxes (in kg P ha-1 yr-1) were 0.08; 0.06 and 0.4, for NE, ND and EG, respectively. Low concentrations and fluxes of TDN and TDP in runoff in both, NE and ND forests emphasize the conservative nutrient cycling of these native forests under a low nutrient deposition climate. Nevertheless, the opposite was observed in EG.

Acknowledgements: Fondecyt project 1120188

Letzte Änderung 19.06.2014