| Summary: | This study compared and contrasted fine root and fungal biomass production estimates using sand-filled in-growth bags, native-soil-filled in-growth bags, and sequential soil cores in xeric, mesic, and hygric stands of 50-year-old Douglas-fir on Vancouver Island. Although no significant differences in overstorey fine-plus-small (≤5 mm) root production could be found between the three sites, proportional allocations of net primary production to the belowground ecosystem decreased with increasing site productivity. The total annual overstorey biomass production on the low-productivity xeric site was 15.7 t ha⁻¹ yr⁻¹. Of this total, 26.5 percent was allocated to belowground components. On the mid-slope mesic site, total overstorey biomass production increased to 22.9 t ha⁻¹ yr⁻¹, while allocation to the belowground decreased to 24.5 percent. On the high-productivity hygric site, total overstorey production increased to 25.0 t ha⁻¹ yr⁻¹, of which the belowground component represented 20.0 percent.
Large differences were found in the estimates of standing crop of roots between in-growth bags and sequential soil cores. Estimates of annual fine root production, however, were much more similar for native-soil-filled in-growth bags and sequential soil cores.
The quality of growth medium within the in-growth bags was also found to have a significant effect on estimates of standing crop and annual production of roots. Greater amounts of root biomass were found in the in-growth bags which contained nutrient-rich growth media. === Forestry, Faculty of === Graduate
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