Wood density and wood shrinkage in relation to initial spacing and tree growth in black spruce (Picea mariana)

This study has quantified basic wood density and various types of wood shrinkage in relation to initial spacing (or initial planting density) and tree growth based on a 48-year-old black spruce (Picea mariana) spacing trial in eastern Canada. A total of 139 sample trees were collected from four initial spacings (3086, 2500, 2066, 1372 trees/ha) for this study. Analyses of variance (ANOVA) show that initial spacing is the most important parameter affecting wood density significantly, followed by tree diameter at breast height (DBH) class. With increasing spacing, wood density, radial and volumetric shrinkage tend to decrease, whereas longitudinal shrinkage tends to increase gradually. The largest spacing has the lowest wood density, the smallest transverse shrinkage and the largest longitudinal shrinkage. Path analysis indicates that wood density is the most important parameter affecting transverse shrinkage, followed by the distance from the pith. Furthermore, much of the variation of the transverse shrinkage with wood density may be due to the initial spacing and tree DBH class. Path analysis also reveals that longitudinal shrinkage is mainly related to log height and tree DBH class. With increasing log height, longitudinal shrinkage tends to increase, and transverse shrinkage tends to decrease. With increasing DBH class, the trees tend to have an increasing longitudinal shrinkage and a decreasing transverse shrinkage. Overall, this study suggests that a large increase in the initial spacing (e.g., 1372 trees/ha) might lead to a significant reduction in both wood density and transverse shrinkage, and a significant increase in longitudinal shrinkage in black spruce.

Springtime Drought Shifts Carbon Partitioning of Recent Photosynthates in 10-Year Old Picea mariana Trees, Causing Restricted Canopy Development

Springtime bud-break and shoot development induces substantial carbon (C) costs in trees. Drought stress during shoot development can impede C uptake and translocation. This is therefore a channel through which water shortage can lead to restricted shoot expansion and physiological capacity, which in turn may impact annual canopy C uptake. We studied effects of drought and re-hydration on early season shoot development, C uptake and partitioning in five individual 10-year old Picea mariana [black spruce] trees to identify and quantify dynamics of key morphological/physiological processes. Trees were subjected to one of two treatments: (i) well-watered control or (ii) drought and rehydration. We monitored changes in morphological [shoot volume, leaf mass area (LMA)], biochemical [osmolality, non-structural carbohydrates (NSC)] and physiological [rates of respiration (Rd) and light-saturated photosynthesis (Asat)] processes during shoot development. Further, to study functional compartmentalization and use of new assimilates, we 13C-pulse labeled shoots at multiple development stages, and measured isotopic signatures of leaf respiration, NSC pools and structural biomass. Shoot water potential dropped to a minimum of −2.5 MPa in shoots on the droughted trees. Development of the photosynthetic apparatus was delayed, as shoots on well-watered trees broke-even 14 days prior to shoots from trees exposed to water deficit. Rd decreased with shoot maturation as growth respiration declined, and was lower in shoots exposed to drought. We found that shoot development was delayed by drought, and while rehydration resulted in recovery of Asat to similar levels as shoots on the well-watered trees, shoot volume remained lower. Water deficit during shoot expansion resulted in longer, yet more compact (i.e., with greater LMA) shoots with greater needle osmolality. The 12C:13C isotopic patterns indicated that internal C partitioning and use was dependent on foliar developmental and hydration status. Shoots on drought-stressed trees prioritized allocating newly fixed C to respiration over structural components. In conclusion, temporary water deficit delayed new shoot development and resulted in greater LMA in black spruce. Since evergreen species such as black spruce retain active foliage for multiple years, impacts of early season drought on net primary productivity could be carried forward into subsequent years.

Short-term effects of wood ash application on soil properties, growth, and foliar nutrition of Picea mariana and Picea glauca seedlings in a plantation trial

Burning biomass for energy generates ash that could be applied as a soil amendment to ameliorate acidity and mitigate nutrient losses associated with biomass harvesting. These soil improvements may also enhance tree growth and foliar nutrition. In this study, we applied low- and high-carbon wood-derived ash at rates of 0 (control), 1000, and 10 000 kg·ha−1 (dry weight equivalents) to soils planted with Picea mariana (Mill.) B.S.P. and Picea glauca (Moench) Voss in a replicated (5) factorial design. We measured soil properties, tree seedling height, and foliar nutrient contents prior to and 4 mo after wood ash addition to determine the immediate effects on soil physical, chemical, and biological properties, and tree seedling performance. We conclude that there were no negative effects of applying either wood ash and that application of ash at 10 000 kg·ha−1, particularly with the low-carbon ash, produced the greatest changes. We anticipate that changes may become more evident over the longer term, especially with respect to tree growth and nutritional responses (e.g., as nutrient uptake demand increases) once the seedlings become more established.

Complete Chloroplast Genome Sequence of a Black Spruce (Picea mariana) from Eastern Canada

ABSTRACT Here, we present the chloroplast genome sequence of black spruce (Picea mariana), a conifer widely distributed throughout North American boreal forests. This complete and annotated chloroplast sequence is 123,961 bp long and will contribute to future studies on the genetic basis of evolutionary change in spruce and adaptation in conifers.

Non-uniform growth dynamics of a dominant boreal tree species (Picea mariana) in the face of rapid climate change

Northwestern Canada’s boreal forest has experienced rapid warming, drying, and changes to permafrost, yet the growth responses and mechanisms driving productivity have been understudied at broad scales. Forest responses are largely driven by black spruce – the region’s most widespread and dominant tree. We collected tree-ring samples from four black spruce-dominated sites across 15° latitude, spanning gradients in climate and permafrost. We investigated (1) differences in growth patterns, (2) variations in climatic drivers of growth, and (3) trends in water use efficiency (WUE) through ¹³C isotope analysis from 1945 – 2006. We found positive growth trends at all sites except mid-latitude, where rapid permafrost thaw drove declines. Annual growth was lowest at the tree limit site and highest at the treeline. Climatic drivers of these growth patterns varied; positive growth responses at the northerly sites were associated with warmer winters, whereas Δ¹³C trends and climate-growth responses at mid-latitude sites indicated growth was limited by moisture availability. Δ¹³C signatures indicated increased WUE at the southernmost site, with no significant trends at northern sites. These results suggest that warming will increase growth of trees at black spruce’s northern extent, but southerly areas may face drought stress if precipitation does not balance evapotranspiration.