Summary

The Long-Term Soil Productivity (LTSP) study was established to demonstrate how alteration of soil porosity and organic matter (two of the more alterable soil properties) would affect soil processes and site productivity throughout these forest types. In BC, four fully replicated LTSP installations now exist and a fifth set is currently being installed. The experimental design is a 3 x 3 factorial with 3 levels of organic matter loss and 3 levels of soil compaction. There are three replicate blocks in the Sub-boreal Spruce (SBS) biogeoclimatic zone with one replicate in each of the Prince Rupert, Prince George, and Cariboo Forest Regions. The replicated site in the Boreal White and Black Spruce (BWBS) biogeoclimatic zone is in the Dawson Creek Forest District, Prince George Forest Region. The fully replicated Interior Douglas-fir (IDF) installation on common, acidic forest soil is in the Kamloops Forest Region. The fully replicated IDF installation on the more sensitive calcareous soils is in the Invermere Forest District, Nelson Forest Region. Two replicates are being installed in the ICH to complete an installation initiated by the USDA Forest Service in Idaho.

The LTSP is a full rotation length study of the impacts of soil disturbance on site productivity, therefore short-term responses to soil disturbance treatments need to be interpreted with caution. After 5 years in the SBS, we could not detect a treatment effect on white spruce or lodgepole pine tree height, although some trends were starting to appear for white spruce height increment. In the BWBS, where forest floor was retained, the tallest aspen regeneration was found on the treatments with the least amount of soil disturbance. Organic matter removal appeared to stimulate production of a greater numbers of aspen suckers, but they were shorter than those found on the treatments where organic matter was retained. Our short-term results have confirmed that sites and species respond differently to the same disturbance and that soil properties change over time after disturbance. This supports the need to establish and monitor these soil disturbance studies over a range of species and sites and over the long-term.

The Long-Term Soil Productivity Study is the only replicated long-term study of soil productivity and the effects of soil disturbance in the world. The Long-Term Soil Productivity program is the world's largest co-ordinated effort to understand how soil disturbance affects long-term forest productivity. To be competitive in the greener global market, BC must demonstrate that it is carrying out research on the impacts of site disturbance on forest productivity. To better manage the forest resource, BC must invest in long-term studies that provide concrete results that can be applied to the refinement of forest practices, regulations, guidebooks, and 'best management practices'.

The overall benefits to BC's forest sector of the Long-Term Soil Productivity Study will include increased certainty about soil disturbance and site productivity so that undue detrimental disturbance can be avoided and non-detrimental disturbance can avoid censure. The LTSP serves as a formal test for soil disturbance provisions in the Forest Practices Code Act of B.C. and also serves to demonstrate to the international scientific and environmental community that B.C. is serious about sustainable development.