Projection of Abies balsamea distribution under conditions of climate change: incorporation of species plasticity to environmental change

点击翻译按钮获取中文摘要

Having intially been used strictly for silvicultural purposes, provenance tests are now being viewed as well-suited to study intra-specific variation in adaptation of trees to changes in climate. Studies which assess tree performance under changing climatic conditions, when conducted under controlled conditions are, however, limited by spatial and temporal restrictions. These limitations make long term provenance plots established in North America useful in providing data that may give reliable information on species performance outside their natural range.***An important physiological process in plant productivity is photosynthesis, the rate of which can be influenced by provenance variation. Photosynthetic response of plant species to variations in environment can be assessed at both the small, leaf-level, and large, ecosystem-level, scales. An eddy covariance tower in the Acadian Research Forest, southcentral New Brunswick (NB), will provide the data needed to characterise photosynthesis at the large, ecosystem scale. Species photosynthetic response at the ecosystem scale is determined by mathematically decomposing tower-based measurements of net CO2 exchange (or the negative of net ecosystem productivity, -NEP) into its component fluxes of gross ecosystem production, associated with light interception and assimilation, and respiration with simple NEP models and numerical optimisation. Information generated by the leaf- and ecosystem-level data collection can then be used to specify the parameters of the same models as a function of leaf-level information. This would allow the use of the models to provide an ecosystem-level characterisation of species response for forests lacking tower data, as is the case for 12 provenances currently growing at the North Star Provenance Test in northwest NB. The seeds for the provenances come from source areas within the present-day range of balsam fir, a commercially- and ecologically-important tree species in Canada. Ecosystem-level species-response functions formulated from the work will help re-define balsam fir distribution projections for a significant part of Atlantic Canada. Current species distribution models use "crisp" thresholds that are derived from assessments of range characteristics related to climate. This work will add a new level of realism (i.e., species plasticity) in balsam fir distribution projections for Atlantic Canada.******