Response of Forest Productivity to Organic-Matter Removal Depends on Soil Properties at Six Long-Term Soil Productivity (LTSP) in British Columbia, Canada.

Maintaining long-term forest productivity is legally mandated due to its importance for future timber production and ecosystem services. The Long-Term Soil Productivity (LTSP) project monitors the response of forest productivity to organic-matter removal (OMR) throughout North America. In the first 10-years, tree growth response to OMR vary among sites. Some of this variability in tree growth response is linked to soil and climate properties, yet it is unknown whether or how variability in forest health response is linked to soil and climate properties. At six LTSP sites in the interior of British Columbia, Canada we test the influence of soil (C, P, N, pH, Ca and ectomycorrhizae) and climate (mean annual temperature and precipitation) properties on the response of lodgepole pine growth and health to whole-tree harvesting (WTH) and forest-floor removal (FFR) relative to bole-only harvesting. Soil carbon (kg/ha) increase resilience of tree growth to WTH. Soil phosphorus (kg/ha) increased the resilience of tree health to FFR. Soil nitrogen (kg/ha) increased the resilience of tree growth but decreased the resilience of tree health to FFR. These findings extend the use of soil P as an indicator of tree growth sensitivity to include forest health sensitivity to OMR. Further, the opposite effect of soil N on tree growth and health response suggests management practices based on tree growth could have negative consequences for tree health.