Figure 4
From: Water quality in New Zealand’s planted forests: a review
Range of TN, NO3-N (a), TP and DRP (b) mean and median concentrations recorded in pasture (Pa) (n = 33), mature planted forest (PF) (n = 53) and indigenous forest (IF) (n = 35) streams. NOx-N values have been aggregated with NO3-N as nitrite is rapidly oxidised to nitrate and typically comprises a small portion of oxidised-N. Similarly Amm-N values have been aggregated with NH4-N values as NH3-N comprises a small component of Amm-N. Mean and median concentrations derived from tables and text or estimated from figures in references (Fahey and Stansfield 2006; Friberg et al. 1997; Macaskill et al. 1997; Matheson et al. 2011; Parkyn et al. 2006; Thompson and Townsend 2004b; Townsend et al. 1997; Young et al. 2005). The anomaly of a wider range of NO3-N/NOx-N concentrations than TN concentrations in planted forest streams (Figure 4a) was influenced by Fahey & Stansfield’s (2006) Hawke’s Bay study and probably due to the lower sampling intensity of TN, capturing a smaller range of concentrations compared with NO3-N (sample size for NO3-N and TN, 62-64 and 3-4 respectively).