Limitations to sub-boreal forest growth and carbon sequestration from tree to forest scale before and after natural and anthropogenic disturbances.

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Forests in central British Columbia have been and remain a tremendously important and sustainable resource for employment, local to national economies, bioenergy, fibre and wood product production and export, biodiversity, recreation, non-timber products, and greenhouse gas mitigation to name a few. However, the future of these forests is dependent upon our understanding of the relationships between forest health, growth, and a changing environment (e.g. climate change: notably temperature and water). Also important are changes in forest diversity and interactions in and between tree and non-tree species, nutrient dynamics (e.g. nitrogen (N) inputs such as from N2-fixing organisms), disturbance regimes (e.g. fire), harvesting systems, and others. My proposed research will address a range of questions that will be critical for understanding how limitations and changes in past, present and future have affected/affect/will affect important sub-boreal forest types and their productivities. My research objectives are:***1. To use forest stand-level CO2 and H2O exchange to corroborate and calibrate tree- to stand-level growth and productivity of sub-boreal forests. CO2 and H2O exchange at the tree-level, daily to annual stem diameter changes (radial growth), and CO2 and H2O flux measurements for stem (e.g. sap flux and/or gas-exchange) for key over- and under-story plants will be measured. These will be scaled up to stand-level (e.g. using approaches taken in Bowler et al. 2012). I will have 9 to 10 years of continuous forest-scale eddy-covariance CO2 and H2O flux measurement, canopy measurement (e.g. live versus dead, fall-down rates of dead trees) and belowground respiration for the an eddy-covariance flux tower site by 2016, with measurements continuing for the duration of my proposed research based on a 2015 CFI award to collaborators at UBC. ***2. To examine the impact of arboreal N2-fixing cyanolichens (low to high tree-level abundance) on growth of spruce and fir by examining radial growth (e.g. dendrochronology and/or dendrometer). Tree- to stand-level growth and N content will be examined relative to epiphytic cyanolichen biomass loading and tree-level N inputs and N conditions of the soil and host trees. Importance of deciduous (non-crop) species such as in the genus Populus adjacent to conifer species will be examined for their roles in facilitating cyanolichen loading and conifer growth rates from tree to landscape scale. Atmospheric N deposition (wet and dry) will be determined at the experimental tree and site or landscape level. I plan to use stable isotopes (natural abundance and/or possibly enrichment) to clarify directions and magnitudes of nutrient exchanges. Long-term manipulations of epiphyte loadings on trees, particularly cyanolichen, will be established in the field and changes to N inputs evaluated, as well as subsequent epiphyte succession.**