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Understanding the characteristics of riparian zones in low relief, sandy catchments that affect their nutrient removal potential

O’Toole, P., Chambers, J.M. and Bell, R.W. (2018) Understanding the characteristics of riparian zones in low relief, sandy catchments that affect their nutrient removal potential. Agriculture, Ecosystems & Environment, 258 . pp. 182-196.

Link to Published Version: https://doi.org/10.1016/j.agee.2018.02.020
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Abstract

Riparian zones are considered to improve stream condition by providing a buffer between waterways and agricultural land that can intercept nutrients, but is their efficacy universal? This paper develops a conceptual model comparing the interactions of slope, soil, hydrology, vegetation and nutrient dynamics between 1) the riparian zone of an intermittent stream in a low-relief (1.6%) catchment with deep sands of low reactivity (Bingham Creek) and 2) a perennial stream in a sloped (10%) catchment with reactive soils over an impermeable layer (Lennard Brook), with a view to compare and contrast their riparian functionality. This study compared the attributes of groundwater (three rows of nested piezometers) (0.5 m,1.5 m and 2.5 m depth), stream, soil and vegetation across a transect from the stream, through the riparian zone to agricultural paddocks. In the low-relief catchment, water did not flow through the riparian zone as in a sloped catchment. Porous soils, together with a lack of slope or a confining layer meant water oscillated vertically through the soil profile over the season, with minimal horizontal movement and limited interaction with the active root zone of riparian vegetation; the intermittent stream discharged P-rich water into the riparian zone during the first flush of winter rains. The highly unreactive sands resulted in trivial P or C uptake resulting in high dissolved concentrations in adjacent streams (0.6–0.9 vs 0.001–0.002 mg/L TP, 58 vs 3 mg/L DOC for flat vs sloped catchments respectively). The high DOC in slow-moving groundwater resulted in highly reducing conditions, promoting P solubility and potentially denitrification. Litterfall from vegetation marginally improved riparian soils with better P retention relative to the adjacent paddock (3620–268 kg TP/ha storage) and reduced FRP in the groundwater relative to the stream (27 vs 80%). The conceptual model developed highlights an alternative functionality of riparian zones for low-relief catchments that challenges the assumption of riparian efficacy.

Publication Type: Journal Article
Murdoch Affiliation: School of Veterinary and Life Sciences
Publisher: Elsevier B.V.
Copyright: © 2018 Elsevier B.V.
URI: http://researchrepository.murdoch.edu.au/id/eprint/40461
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