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RESEARCH ARTICLE

Relationships between land use and nitrogen and phosphorus in New Zealand lakes

Jonathan M. Abell A C , Deniz Özkundakci A , David P. Hamilton A and Steven D. Miller B
+ Author Affiliations
- Author Affiliations

A Centre for Biodiversity and Ecology Research, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.

B School and Mathematical and Computing Sciences, University of Waikato, Hamilton 3240, New Zealand.

C Corresponding author. Email: jma27@waikato.ac.nz

Marine and Freshwater Research 62(2) 162-175 https://doi.org/10.1071/MF10180
Submitted: 1 July 2010  Accepted: 17 December 2010   Published: 24 February 2011

Abstract

Developing policies to address lake eutrophication requires an understanding of the relative contribution of different nutrient sources and of how lake and catchment characteristics interact to mediate the source–receptor pathway. We analysed total nitrogen (TN) and total phosphorus (TP) data for 101 New Zealand lakes and related these to land use and edaphic sources of phosphorus (P). We then analysed a sub-sample of lakes in agricultural catchments to investigate how lake and catchment variables influence the relationship between land use and in-lake nutrients. Following correction for the effect of co-variation amongst predictor variables, high producing grassland (intensive pasture) was the best predictor of TN and TP, accounting for 38.6% and 41.0% of variation, respectively. Exotic forestry and urban area accounted for a further 18.8% and 3.6% of variation in TP and TN, respectively. Soil P (representing naturally-occurring edaphic P) was negatively correlated with TP, owing to the confounding effect of pastoral land use. Lake and catchment morphology (zmax and lake : catchment area) and catchment connectivity (lake order) mediated the relationship between intensive pasture and in-lake nutrients. Mitigating eutrophication in New Zealand lakes requires action to reduce nutrient export from intensive pasture and quantifying P export from plantation forestry requires further consideration.

Additional keywords: agriculture, catchment connectivity, catchment management, eutrophication, GIS, nutrients, water quality, watershed.


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