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Depletion of white spruce (Picea glauca) in mixedwood forest is a frequent problem, particularly in stands that were high-graded as a result of inadequate silviculture and spruce budworm (Choristoneura fumiferana) epidemics. To provide information that will help guide restoration efforts, we assessed the effect of four seed-tree retention (STR: 0, 10, 40 and 60 trees/ha) levels and two scarification (SC: patch scarification and disk-trenching) types on white spruce reintroduced by planting in a high-graded yellow birch (Betula alleghaniensis)–conifer stand. We present the 9-year results from the seedling physiology, nutrition and morphology. Physiology and nutrition changed with years, but did not vary with STR levels and SC types. Significant increases in the number of internodal branches, height growth, and total height at the two lowest STR levels and after release suggest that the performance of white spruce in terms of morphology and growth is sensitive to small variations in available light. Because seedling morphology and growth were similar between SC types, a moderate disturbance of the forest floor by disk-trenching would be sufficient at a relatively low cost. Our findings highlight that the STR levels influenced the morphology and growth of planted white spruce seedlings more than the SC types. [ABSTRACT FROM AUTHOR]

We employ a dendrochronological approach to examine spatial variation in radial tree growth-climate relationships and responses to global climate oscillations across the geographic ranges of Picea glauca and Picea engelmannii. Tree-ring chronologies were constructed for 77 sites and analyzed using correlation coefficients for monthly climatic variables. In general, for Picea glauca, stands in the western portion of its range had significant negative correlations with temperature during fall, winter, and spring; only summer temperature was positively correlated with tree growth. In eastern North America, Picea glauca growth was negatively correlated with winter and spring temperature. Across the north-south range of Picea engelmannii, growth of northern populations was positively correlated with temperature in most seasons except spring, which had negative correlations, and response to winter precipitation differed between northern and southern populations. However, some monthly values for both species correlations were altered due to decadal oscillation phase, especially for the Pacific Decadal Oscillation. [ABSTRACT FROM AUTHOR]

Tree species identification is important in forest management. The multispectral lidar Titan of Teledyne Optech Inc. can improve tree species separation by providing classification features computed from the three-channel intensities, ratios and normalized differences. However, the value of features used in classification algorithms (e.g., random forest, RF) may vary with tree size. The focus of the present study is to show how tree height influences the 3D and intensity features, how this relationship may affect the species classification accuracy, and how different classification strategies may circumvent this problem. Six needleleaf species (Pinus resinosa, Pinus strobus, Pinus sylvestris, Larix laricina, Picea abies and Picea glauca), found in plantations of different ages, were sampled to train classifiers. Some features yielded a good discriminatory power for species identification, despite their relation to tree height (r2 up to 0.6). Two classification strategies—a) using only size-invariant features (SIF) and b) training separate classifiers per tree height strata (HSC)—were compared to a standard classification (STD: all features, without height stratification). The accuracy of the SIF approach was lowest, useful variables being removed due to their relationship to tree height. The HSC provided only a minor improvement over the STD results. [ABSTRACT FROM AUTHOR]

The 19-20-year effects of mechanical site preparation, windrow burning, chemical site preparation, and postplanting vegetation control on survival and growth of planted white spruce are reported from two boreal sites in British Columbia, Canada. Survival differed between treatments at both sites, but was relatively good (≥77%) even in untreated plots. Current data regarding the proportion of spruce that were physically overtopped by vegetation and previous results from related soils and vegetation studies suggest that lasting reductions in tall shrub and aspen abundance were more important to spruce growth than early microenvironmental effects associated with manipulating the rooting environment. At Inga Lake, postplanting vegetation control produced a 13-fold increase in spruce volume over the control after 19 years, which was statistically equivalent to increases resulting from fine mixing, plow-inverting and windrow burning site preparation treatments. At Iron Creek, chemical site preparation and plow-inverting quadrupled spruce volume, whereas mounding, patch scarification and disc trenching were ineffective. Growth and yield simulations using treatment-specific site index curves for Inga Lake suggested that rotation length could be shortened by 12-16 years through the use of site preparation or postplanting vegetation control. However, untreated areas, due to the relatively good survival of white spruce at age 19, were predicted to produce equivalent volume if left to grow to mean annual increment culmination age. [ABSTRACT FROM AUTHOR]

The impact of freezing temperatures and exposure times during budbreak and shoot elongation on 10-month-old containerized white spruce seedlings [ Picea glauca (Moench) Voss] was studied. Seedlings were exposed to 0, -2, -4, -6, -8 and -10°C for 0, 1, 2, 3, 4, 5 and 6 h at four stages of budbreak and shoot elongation (stage 1: unswollen bud; stage 2: swollen bud; stage 3: bud scales parted by emerging needles; stage 4: 1-5 cm of terminal shoot growth). Seedling and terminal bud survival, viability of first-year needles (developed before frost exposure), terminal shoot length, stem diameter and aerial dry mass were measured 90 days after freezing exposure. Frost severity had a much greater influence on seedling survival, damage and subsequent growth than exposure time. The bud development stage at which freezing temperatures were applied also affected survival and subsequent growth. [ABSTRACT FROM AUTHOR]