Molecular techniques have provided novel insights and significant advances in research on soil fungal ecology and have been applied to various soils in different ecosystems , such as forests ( Perkiomaki et al . , 2003 ) , grasslands ( Brodie et al . , 2003 ) , dunes ( Kowalchuk et al . , 1997 ) , stream sediments ( Nikolcheva et al . , 2003 ) and agricultural fields ( Gomes et al . , 2003 ) .