Comparison of humus horizons from two ecosystem phases on northern Vancouver Island using ¹³C CPMAS NMR spectroscopy and CuO oxidation

Much forested land in the wetter zones of northern Vancouver Island is characterized by thick humus layers, with two distinct ecosystem phases: the younger "HA' phase arising from disturbance and the old-growth "CH' phase. Solid-state ¹³C nuclear magnetic resonance spectroscopy and CuO oxidation were used examine chemical differences in the humus after clearcutting. The differences between CH and HA sites were: higher tannin content in the CH sites, most likely from salal inputs; and higher ratio of carbohydrate to lignin C, indicating less effective decomposition in CH sites. Oxidation with CuO also showed more advanced decomposition in the non-woody horizons of HA than of CH sites. Less effective decomposition possibly due in part to tannin accumulation could contribute to the lower forest productivity on salal-dominated CH sites in this region. -from Authors