Stream exports of coarse matter and phosphorus following wildfire in NE Victoria, Australia

Abstract

Abstract:The temporal change in total phosphorus (TP) export from two burnt upland catchments is reported. Following wildfire in January 2003, two burnt forested headwater catchments (136 and 244 ha) in the East Kiewa valley, Victoria, were instrumented to measure discharge, turbidity and to collect stream water samples. In addition, samplers were positioned in the stream bed at the outlet of each catchment to continuously sample material transported along the bed of the stream. Approximately, every 2 weeks, the material collected by the stream bed samplers was weighed and sub-sampled. The percentage of coarse (>1 and <5 mm in diameter) mineral (including soil aggregates) and organic matter was determined and then analysed for TP. Between the first and third years after fire, sampled coarse matter and associated TP loads decreased by an average of 53% and 62%, respectively. Over the 3-year study, the amount of coarse matter exported during winter/spring decreased considerably, whereas export rates during summer/autumn remained relatively constant. Coarse matter exports were estimated to be approaching pre-fire levels after 3-4 years. Results on total suspended solids (TSS) TP and total dissolved phosphorus (TDP) from a parallel study are incorporated to explore TP partitioning. TP exported with TSS dominated the total TP export loads, with coarse matter TP and TDP each contributing approximately 10% over the study period.

Phosphorus transfer across boundaries: from basin soils to river bed sediments

“…In the second part of the study, the concentrations of total and bioavailable P in the soil-suspended sediments-river bed sediments transition system were studied in order to identify the major P sinks at a watershed scale. Comprehensive studies involving P transfer across these three matrixes are scarce (House et al 1998;Noske et al 2010;Pöthig et al 2010), highlighting the innovative nature of the present study. The results obtained will allow comparison of the effects of different types of land use on the total and bioavailable phosphorus concentrations in an aquatic ecosystem at a catchment scale.…”

Impacts of wildfire and salvage harvesting on water quality and nutrient exports from radiata pine and eucalypt forest catchments in south-eastern Australia

“…This difference in P exports largely reflects low sediment losses from Ella associated with lower rainfall and runoff as well as less relief compared to the wet eucalypt catchments (Lane et al, 2008;Noske et al, 2010). Furthermore, average seasonal particulate P concentrations (mg kg À1 ) measured on suspended material exported during storms from the wet eucalypt catchments were 2-3 times higher than particulate P concentrations on storm TSS samples from Ella for the second and third years after fire (Noske et al, 2010).…”

“…Ash may also make an important contribution to nutrient transfer soon after fire (Spencer and Hauer, 1991;Earl and Blinn, 2003;Ferreira et al, 2005). As a result, stream concentrations and catchment exports of various constituents (including suspended sediment, nutrients, solutes and trace elements) may experience substantial increases compared to unburnt conditions (Lane et al, 2006(Lane et al, , 2008Reneau et al, 2007;Mast and Clow, 2008;Noske et al, 2010;Smith et al, 2011a). Such changes may be most pronounced during short-duration stormflow events or snowmelt periods, and some constituents may remain elevated over background levels for a few years after fire or longer (Mayor et al, 2007;Bladon et al, 2008;Emelko et al, 2011;Rhoades et al, 2011;Ryan et al, 2011).…”

A critical review of the science underpinning fire management in the high altitude ecosystems of south-eastern Australia

“…On-going soil disturbance could hinder recovery of nutrient stocks given the steep slopes and friable soils of much of the alpine and montane region, and known relationships between fire severity and propensity for soil and nutrient loss via erosion (e.g. Lane et al, 2006;Sheridan et al, 2008;Noske et al, 2010).…”