UBC Theses and Dissertations
Incorporating stand-health metrics into monitoring the effects of soil disturbance during logging on long-term forest productivity Reid, Anya Martina
Stand volumes at rotation are usually predicted from models based on tree growth, assuming that fast-growing trees are, and will remain, healthy. However, greater-than-expected disease occurrence on dominant trees has been reported in regenerating forests in British Columbia (BC), suggesting that forest-productivity monitoring should include health measurements. In this thesis, I assess growth and health of lodgepole pine at six installations of the Long-Term Soil Productivity (LTSP) project 15 to 20 years after soil-disturbance treatments (organic-matter removal and soil compaction). To determine treatment effects on forest health, 5400 lodgepole pine seedlings at six sites were examined for vigour and pest occurrence. Treatment effects differed among sites, suggesting that the effects of the soil-disturbance treatments on forest health are context-dependent. Larger trees generally had higher frequency of disease, contradicting the assumption that fast-growing trees are healthy. Spectral-reflectance indices of greenness calculated from aerial images correlated with ground-based measures of tree vigour and foliar disease, indicating a role for remote-sensing techniques in forest health monitoring. Topsoil-nutrient content was reduced in the forest-floor removal treatment plots, with foliar phosphorus and potassium concentrations (%) being reduced in the three older sites in the sub-boreal spruce zone. The forest-floor removal treatment was also associated with lower abundance of ectomycorrhizae, but greater abundance Suillus sp., a fungus that is associated with nitrogen-fixing diazatrophic bacteria. The main predictive growth-and-yield model used in BC (called TASS with the interface TIPSY), underestimated tree height (m) but overestimated stand density (stems/ha) at the six sites, suggesting greater-than-predicted tree mortality. Monitoring forest health in conjunction with tree growth after free-to-grow standards are met is recommended for more accurate management of long-term forest productivity.
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