Stephen J. Colombo

Frost hardiness gradients in shoots and roots of picea mariana seedlings

Frost hardiness of tissues along the length of the stem and the root was investigated in first‐year black spruce (Picea mariana (Mill.) B.S.P.) seedlings. Frost hardiness of 1 cm long stem and root...

Influence of Nursery Cultural Practices on Cold Hardiness of Coniferous Forest Tree Seedlings

In many parts of the world the production of coniferous tree seedlings in nurseries is dependent on surviving the effects of freezing temperatures in winter. In some northern temperate forest regions, seedlings are grown outdoors and can be exposed to potentially damaging freezing temperatures any month of the year. Elsewhere, seedlings in nurseries may experience freezing temperatures outside during the winter or may be protected by cold or frozen storage in a controlled environment. In each of the above cases, the ability to withstand freezing and the overall stress resistance associated with cold hardening of conifer seedlings make cold hardiness an important attribute for nursery stock production.

Frost hardening spruce container stock for overwintering in Ontario

Difficulties overwintering container stock in northern Ontario led to the development of the “extended greenhouse culture” hardening regime for spruce seedlings. Laboratories to measure shoot frost hardiness and evaluate terminal bud development were established to monitor nursery crops being hardened using this regime. Information on frost hardiness and bud development provided by these laboratories has been used by nursery managers to determine readiness of container seedlings for overwintering. Since 1982, over 200 stock lots have been monitored by these operational laboratories. This database can be used to determine the importance of nursery cultural factors and seed source on frost hardening. The database shows large differences between nurseries in approach to hardening seedlings which were reflected in levels of freezing damage, winter desiccation and overwintering success. Rates of frost hardening (i.e., the interval between terminal bud initiation and attainment of a --15°C level of shoot frost hardiness) of crops produced in north central Ontario failed to show significant seed source effects. The rate of frost hardening was faster in crops producing fewer needle primordia in terminal buds.

An overview of Ontario's Stock Quality Assessment Program

Since 1992, the Stock Quality Assessment Program at the Ontario Forest Research Institute (OFRI) has offered seedling physiological testing services to foresters and nursery managers. The purpose of this program is to improve nursery stock quality and plantation performance by developing and applying procedures for assessing the physiological quality of nursery stock. Two levels of testing are available: Seedling Certification and Problem Stock Testing. Testing at both levels involves a visual assessment, measurement of chlorophyll fluorescence of the foliage and root growth potential. Applying these tests has directly improved plantation establishment between 1992 and 1995 by preventing over 3 million damaged seedlings from being planted, at an estimated regeneration cost savings of over

Carbon debt repayment or carbon sequestration parity? Lessons from a forest bioenergy case study in Ontario, Canada.

2 million (Can). Consideration of cost-benefits for both direct and indirect values demonstrates the merits of a stock testing program. Testing has been conducted either at OFRI or at a private lab, providing clients with an impartial assessment of their stock. Consistent test results, comparable from year-to-year and between laboratories, are achieved by the use of controlled environment testing, trained personnel and duplicate testing on selected stocklots. A database comprised of physiological test information for over 1100 stocklots provides a basis for comparing and ranking seedlings grown throughout the province. This database may be used to refine operational nursery practices, to evaluate changes in seedling quality over time, and to relate seedling quality to field performance.

Timing of cold temperature exposure affects root and shoot frost hardiness of Picea Mariana container seedlings

Forest bioenergy can contribute to climate change mitigation by reducing greenhouse gas (GHG) emissions associated with energy production. We assessed changes in GHG emissions resulting from displacement of coal with wood pellets for the Atikokan Generating Station located in Northwestern Ontario, Canada. Two contrasting biomass sources were considered for continuous wood pellet production: harvest residue from current harvest operations (residue scenario) and fibre from expanded harvest of standing live trees (stemwood scenario). For the stemwood scenario, two metrics were used to assess the effects of displacing coal with forest biomass on GHG emissions: (i) time to carbon sequestration parity, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in regenerating forest equalled the amount of forest carbon without harvest for energy production; and (ii) time to carbon debt repayment, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in the regenerating forest equalled forest carbon at the time of harvest. Only time to carbon sequestration parity was used for the residue scenario. In the residue scenario, carbon sequestration parity was achieved within 1 year. In the stemwood scenario, times to carbon sequestration parity and carbon debt repayment were 91 and 112 years, respectively. Sensitivity analysis showed that estimates were robust when parameter values were varied. Modelling experiments showed that increasing growth rates for regenerating stands in the stemwood scenario could substantially reduce time to carbon sequestration parity. We discuss the use of the two metrics (time to carbon sequestration parity and time to carbon debt repayment) for assessing the effects of forest bioenergy projects on GHG emissions and make recommendations on terminology and methodologies for forest bioenergy studies.

Amino Acid, Carbohydrate, Glutathione, Mineral Nutrient and Water Potential Changes in Non-water-stressed Picea mariana Seedlings After Transplanting

Seventeen‐week‐old black spruce seedlings were hardened under short daylengths and one of three short day length environments, which were either warm (24/16°C, day/night) throughout a 10 week hardening period (WW), cool (10/5°C) throughout hardening (CC), or warm for three weeks followed by seven weeks of cool temperatures (WC). Greatest root and shoot frost hardiness resulted from the exposure of seedlings to three weeks of warm followed by seven weeks of cool temperatures. Seedlings receiving warm temperatures throughout hardening increased in root and shoot frost hardiness, but to a lesser extent than seedlings exposed to cool temperatures. The frost hardiness of woody roots was generally greater than that of fine roots, but the extent of the difference in frost hardiness depended on the time since bud initiation and on the hardening treatment.

Carbon Profile of the Managed Forest Sector in Canada in the 20th Century: Sink or Source?

Monthly changes in amino acids, carbohydrates, glutathione and minerals in needles and roots, and the growth of transplanted and non - transplanted black spruce [Picea mariana (Mill) B.S.P.] seedlings during one growing season were compared. Seedlings were watered throughout the growing season. Shoot water potential did not differ significantly between control and transplanted seedlings. However, growth reduction in transplanted seedlings suggests that other transplant - induced effects reduced growth. Compared with control seedlings, needles of transplanted seedlings showed significantly lower levels of all macronutrients and some micronutrients, certain individual and total amino acids and sucrose. Needles of transplanted seedlings showed higher concentrations of tryptophan and certain carbohydrates. Transplanted seedling roots had relatively minor differences in nutrient and biochemical constituents compared with control seedling roots. The total amino acid content of the needles appeared to have poten...

Effects of harvesting on spatial and temporal diversity of carbon stocks in a boreal forest landscape

Canada contains 10% of global forests and has been one of the worlds largest harvested wood products (HWP) producers. Therefore, Canadas managed forest sector, the managed forest area and HWP, has the potential to significantly increase or reduce atmospheric greenhouse gases. Using the most comprehensive carbon balance analysis to date, this study shows Canadas managed forest area and resulting HWP were a sink of 7510 and 849 teragrams carbon (TgC), respectively, in the period 1901-2010, exceeding Canadas fossil fuel-based emissions over this period (7333 TgC). If Canadian HWP were not produced and used for residential construction, and instead more energy intensive materials were used, there would have been an additional 790 TgC fossil fuel-based emissions. Because the forest carbon increases in the 20th century were mainly due to younger growing forests that resulted from disturbances in the 19th century, and future increases in forest carbon stocks appear uncertain, in coming decades most of the mitigation contribution from Canadian forests will likely accrue from wood substitution that reduces fossil fuel-based emissions and stores carbon, so long as those forests are managed sustainably.

Frost hardening in first-year eastern larch (Larix laricina) container seedlings

Carbon stocks in managed forests of Ontario, Canada, and in harvested wood products originated from these forests were estimated for 2010–2100. Simulations included four future forest harvesting scenarios based on historical harvesting levels (low, average, high, and maximum available) and a no-harvest scenario. In four harvesting scenarios, forest carbon stocks in Ontarios managed forest were estimated to range from 6202 to 6227 Mt C (millions of tons of carbon) in 2010, and from 6121 to 6428 Mt C by 2100. Inclusion of carbon stored in harvested wood products in use and in landfills changed the projected range in 2100 to 6710–6742 Mt C. For the no-harvest scenario, forest carbon stocks were projected to change from 6246 Mt C in 2010 to 6680 Mt C in 2100. Spatial variation in projected forest carbon stocks was strongly related to changes in forest age (r = 0.603), but had weak correlation with harvesting rates. For all managed forests in Ontario combined, projected carbon stocks in combined forest and harvested wood products converged to within 2% difference by 2100. The results suggest that harvesting in the boreal forest, if applied within limits of sustainable forest management, will eventually have a relatively small effect on long-term combined forest and wood products carbon stocks. However, there was a large time lag to approach carbon equality, with more than 90 years with a net reduction in stored carbon in harvested forests plus wood products compared to nonharvested boreal forest which also has low rates of natural disturbance. The eventual near equivalency of carbon stocks in nonharvested forest and forest that is harvested and protected from natural disturbance reflects both the accumulation of carbon in harvested wood products and the relatively young age at which boreal forest stands undergo natural succession in the absence of disturbance.