Modelling the Long-term Nitrogen Balance of a Large Wetland in North Queensland, Australia
摘要
There is an urgent need to reduce nitrogen and sediment loads entering the Great Barrier Reef lagoon to protect this world heritage ecosystem. One method to achieve this is the restoration and construction of coastal wetlands that can remove significant amounts of nitrogen and sediment. However, the capacity of wetlands to do this is currently uncertain due to the paucity of comprehensive wetland studies of sufficient duration. This study reports the results of a combined water and nutrient balance model that has been used to estimate the long term (10-year) removal of nitrogen and sediment in the Mungalla wetland in north Queensland, Australia. We found that annual nitrogen removal in this wetland can vary by a factor of four (37 to 147 kg ha−1 year−1) depending on its hydrology and water residence time; both driven by rainfall. Short-term (1 to 3 years) monitoring of the water and nutrient balances of wetlands therefore give results that are particular to the rainfall in the period studied. However, more representative long-term balances can be obtained from a combination of short-term monitoring with water and nutrient balance modelling over much longer periods. Such results are required to provide wetland nutrient balance figures for many years, which are required for selecting wetland types and locations with the best nitrogen removal capacity. Loads of nitrogen and sediment to the Great Barrier Reef lagoon could be reduced significantly if relatively small areas of sugar cane were converted to wetlands like Mungalla.