Effects of Gully and Channel Erosion on Carbon and Nitrogen Storage, Mineralization and Export in a Subtropical Catchment

Abstract

The fluxes of sediment, carbon and nutrients in rivers and consequently entering estuaries and the ocean, have been drastically altered by humans. Erosion is known to be one of the major causes of sediment flow disruption by the transfer of large quantities of soil from the terrestrial to the aquatic environment. It is also known to transport in association with sediment, a large amount of carbon and nutrients to the marine environment. Carbon and nutrient fluxes are influenced by other point and non-point sources which have been largely studied, particularly the effects of industrialized agriculture on nutrient fluxes. However, few studies have looked at the interrelation between the sediment, carbon, and nitrogen cycle disruption in eroding catchments. Gully and channel erosion are widespread across Australia as a result of land clearing and/or the introduction of livestock post-European settlement. This is a particular problem in subtropical Australia, where subsoil erosion is known to be the dominant source of sediment. The implications of gully and channel erosion for sediment budgets have been studied in detail, but its implications for carbon and nitrogen budgets remain an open question. Nitrogen is of particular importance, because it is considered to be the limiting nutrient in streams and rivers of the region and in most estuaries and coastal areas.