Freshwater Umbrella Research 2004-7

WP 3: Nitrate leaching

Potential N leaching_pathwaysTask 3.5 — Carbon-Nitrogen ratio (C:N) survey of AWMN sites

While Tasks 3.1 - 3.4 above provide information on the controls of rapid N leaching via pathways 1 and 2 in Figure 1, at least two thirds of N inputs enter the terrestrial N cycle (Curtis et al., submitted) and contribute to increased N content and reduced C:N ratio of soils and vegetation. Soil surface organic matter C:N ratio has been shown to have potential for the prediction of microbial nitrate leaching (i.e. nitrate produced by mineralisation of organic N and subsequent nitrification) via pathway 3 in previous DEFRA (Curtis et al., 2004) and NERC (Evans et al., in press) funded studies.

In order to test the relationship between nitrate leaching and C:N ratio of surface organic matter in moorlands, samples will be collected concurrently with the mosses in Task 3.4 above. These samples will be dried and analysed for CHN content at the University of Wales, Bangor, along with the moss samples from Task 3.4. This Task will provide C:N data for UKAWMN sites with existing water chemistry data for testing the parameterisation of N dynamics within MAGIC, using C:N ratio as the key predictor of N leaching.

The moss survey fieldwork was completed during July and August 2006.