Marek J. Krasowski

Effects of soil moisture manipulations on fine root dynamics in a mature balsam fir (Abies balsamea L. Mill.) forest

We tested the hypothesis that moisture stress affects fine root dynamics during and after the stress. To this end, we investigated the effects of soil moisture on annual and seasonal fine root production and mortality over 4 years in a mature balsam fir (Abies balsamea L. Mill.) stand using a minirhizotron and soil coring. Droughting and irrigating treatments were imposed for 17 weeks during the third year of the study, and post-treatment recovery was measured during the fourth year. Monthly fine root production was often reduced by low soil water content (SWC) during July-September in the pre-treatment years and by imposed drought. Irrigation resulted in higher summer fine root production than in pre-treatment years. In the recovery year, increased fine root production was observed in the previously droughted plots despite low SWC in August and September. Droughting decreased year-end fine root biomass in the treatment year, but biomass returned to pre-treatment levels during the recovery year. Droughting and irrigating did not affect foliage production during the treatment and recovery years. Our results suggest that for balsam fir, establishment and maintenance of a functional balance between foliage and fine root biomass, with respect to moisture supply and demand, can depend on fine root dynamics occurring over more than one growing season. In addition, our findings provided insights into tree growth responses to interannual variation in moisture supply.

Comparisons of protein profiles of beech bark disease resistant and susceptible American beech (Fagus grandifolia)

BackgroundBeech bark disease is an insect-fungus complex that damages and often kills American beech trees and has major ecological and economic impacts on forests of the northeastern United States and southeastern Canadian forests. The disease begins when exotic beech scale insects feed on the bark of trees, and is followed by infection of damaged bark tissues by one of the Neonectria species of fungi. Proteomic analysis was conducted of beech bark proteins from diseased trees and healthy trees in areas heavily infested with beech bark disease. All of the diseased trees had signs of Neonectria infection such as cankers or fruiting bodies. In previous tests reported elsewhere, all of the diseased trees were demonstrated to be susceptible to the scale insect and all of the healthy trees were demonstrated to be resistant to the scale insect. Sixteen trees were sampled from eight geographically isolated stands, the sample consisting of 10 healthy (scale-resistant) and 6 diseased/infested (scale-susceptible) trees.ResultsProteins were extracted from each tree and analysed in triplicate by isoelectric focusing followed by denaturing gel electrophoresis. Gels were stained and protein spots identified and intensity quantified, then a statistical model was fit to identify significant differences between trees. A subset of BBD differential proteins were analysed by mass spectrometry and matched to known protein sequences for identification. Identified proteins had homology to stress, insect, and pathogen related proteins in other plant systems. Protein spots significantly different in diseased and healthy trees having no stand or disease-by-stand interaction effects were identified.ConclusionsFurther study of these proteins should help to understand processes critical to resistance to beech bark disease and to develop biomarkers for use in tree breeding programs and for the selection of resistant trees prior to or in early stages of BBD development in stands. Early identification of resistant trees (prior to the full disease development in an area) will allow forest management through the removal of susceptible trees and their root-sprouts prior to the onset of disease, allowing management and mitigation of costs, economic impact, and impacts on ecological systems and services.

Advantages of long-term measurement of fine root demographics with a minirhizotron at two balsam fir sites

We used 15 site-years of minirhizotron observations (1998–2006 at one site; 1998–2000 and 2004–2006 at second site) from two mature balsam fir (Abies balsamea (L.) Mill.) sites to quantify interann...

Frost-Related Problems in the Establishment of Coniferous Forests

Cold hardiness has been rarely measured on plants growing on forest sites under different forest management practices. Some researchers measured changes in conifer cold hardiness on detached shoots freezer-tested in the laboratory (Sheppard and Cannell 1985; Sheppard et al. 1989). Others carried portable freezing chambers to forest sites (Strimbeck et al. 1991). In this chapter, we focus on the relationship between forest management practices, the climate, and seedling microclimate characteristics related to the occurrence of frost on forest sites, frost damage to young conifers, and on ways of ameliorating such problems. Indirect frost damage from desiccation and from frost heaving is included here for they are important to forest regeneration. Frost injury to large trees, damage to seedlings from hoar frost, and ice glazing are not discussed.

Managing genetic gain and diversity in clonal deployment of white spruce in New Brunswick, Canada

When selecting a clonal mixture for clonal forestry, a common practice is to specify a minimum acceptable genetic diversity for the mixture, and under that constraint, to maximize its genetic gain. Three selection methods—combined index selection (CIS), clonal mean selection (GMS), and family plus within-family clonal selection (FWFGS)—together with various restrictions on family contributions (family restrictions) were used to estimate gain at a given effective population size (Ne) of clonal mixtures selected from a clonally replicated genetic test of white spruce. The designated target trait for improvement was individual tree volume at age 14 after planting. Regardless of selection method, all genetic gains were >30% at given Ne from five to 20, suggesting that implementing clonal forestry was a very effective deployment strategy. Genetic gain at a specified Ne could be enhanced by using appropriate selection methods: CIS was the most effective, followed by GMS and FWFGS. With an Ne of 15, CIS resulted in an average gain of 43.2%, which corresponded to an increase by 8.1% and 17.3% relative to GMS and FWFGS, respectively. Imposing family restriction increased gain at an Ne. Compared with the respective unrestricted selection, family restrictions increase genetic gain by 3.3%, 7.7%, and 54% for CIS, GMS, and FWFGS, respectively. The optimal family restriction level for each selection method varied with the specified Ne.

Allocation of varietal testing efforts for implementing conifer multi-varietal forestry using white spruce as a model species

Abstract• IntroductionMulti-varietal forestry (MVF) is the deployment of tested tree varieties in plantation forestry. Computer simulation using POPSIM Simulator identified optimal combination of numbers of families, varieties per family and ramets per variety (nf, nc and nr, respectively) yielding the largest genetic gain for a specific status number (NS) in a varietal test (VT) intended for MVF of conifers.• Results and discussionTesting 40 to 80 full-sib families and 20 to 30 varieties per family would be optimal for a VT. This nf interval was insensitive to the number of candidate varieties planted, ratio of genetic variances and selection restriction. It was influenced somewhat by individual narrow-sense heritability (h2), required NS and mating design. Lower h2, lower NS and designs with fewer matings per parent tree favoured the lower range of the nf interval. The optimal nr was 6. It was not markedly affected by the required NS, family size or selection restriction but was strongly influenced by h2 and the ratio of genetic variances. Larger h2 or an introduction of non-additive genetic variance allowed planting fewer ramets per variety.

Age-related changes in survival and turnover rates of balsam fir (Abies balsamea (L.) Mill.) fine roots

Fine-root (≤2 mm) demographics change as forests age, but the direction and extent of change are unknown. Knowledge of the change and understanding of causes will improve predictions of climate change impacts. We used minirhizotrons at three young and three mature balsam fir (Abies balsamea (L.) Mill.) sites to measure median lifespan (MLS) for each site and for annual cohorts. We computed turnover rate from the inverse of MLS (Tinv) and calculated a second turnover rate (T) from annual mortality, annual production and previous year-end standing crop. Median lifespan at mature sites (436 days) was half that at young sites (872 days). Median lifespan of annual cohorts varied widely at all sites. Age-class distributions of fine roots seen by minirhizotrons changed with increasing years of observation, with older age classes accumulating more slowly at mature sites. Our findings highlight the need to determine whether the proportional contributions of absorbing and transporting fine roots to annual production and their median lifespans change during stand development. Due to its variation among annual cohorts, we believe robust estimates of MLS at our sites require 5-7 years of observation, and reliable estimates of Tinv are reached earlier than T.