Engelmann Spruce Seedlings Research Articles

Heterotrophic and Autotrophic Soil Respiration under Simulated Dormancy Conditions

Carbon cycling research has increased over the past 20 years, but less is known about the primary contributors to soil respiration (i.e. heterotrophic and autotrophic) under dormant conditions. It is understood that soil CO2 effluxes are significantly lower during the winter of temperate ecosystems and assumed microorganisms dominate efflux origination. We hypothesized that heterotrophic contributions would be greater than autotrophic under simulated dormancy conditions. To test this hypothesis, we designed an experiment with the following treatments: combined autotrophic heterotrophic respiration, heterotrophic respiration, autotrophic respiration, no respiration, autotrophic respiration in vermiculite, and no respiration in vermiculite. Engelmann spruce seedlings and soil substrates were placed in specially designed respiration chambers and soil CO2 efflux measurements were taken four times over the course of a month. Soil microbial densities and root volumes were measured for each chamber after day thirty-three. Seedling presence resulted in significantly higher soil CO2 efflux rates for all soil substrates. Autotrophic respiration treatments were not representative of solely autotrophic soil CO2 efflux due to soil microbial contamination of autoclaved soil substrates; however, the mean autotrophic contributions averaged less than 25% of the total soil CO2 efflux. Soil microorganism communities were likely the primary contributor to soil CO2 efflux in simulated dormant conditions, as treatments with the greatest proportions of microbial densities had the highest soil CO2 efflux rates. Although this study is not directly comparable to field dormant season soil CO2 effluxes of Engelmann spruce forest, as snowpack is not maintained throughout this experiment, relationships, and metrics from such small-scale ecosystem component processes may yield more accurate carbon budget models.

Linking carbon balance to establishment patterns: comparison of whitebark pine and Engelmann spruce seedlings along an herb cover exposure gradient at treeline

There is increasing evidence that landscape vegetation patterns near species’ range limits are associated with positive biotic interactions, such as in the alpine-treeline ecotone. In the northern Rocky Mountains, whitebark pine (Pinus albicaulis) is considered an early-successional species, able to establish in exposed microsites, while late-successional species such as Engelmann spruce (Picea engelmannii) are more dependent on neighboring vegetation to facilitate establishment. We compared ecophysiological traits associated with carbon balance of newly germinated seedlings of whitebark pine and Engelmann spruce along an herb cover gradient to (1) infer which ecophysiological properties explain the establishment success of seedlings, and (2) to assess differences in establishment patterns with respect to distance from neighboring vegetation. We measured survival over 2 years, and concurrently measured gas exchange and water relations (photosynthesis, respiration, and transpiration), morphology [specific leaf area (SLA)], and biochemistry [chlorophyll fluorescence (F v /F m) and nonstructural carbohydrates]. Both species initially established in the most exposed microsites away from vegetation during their first growing season, but only pine persisted in exposed microsites to the end of the second growing season. Pine exhibited phenotypic traits to increase stress tolerance (e.g., higher soluble sugar concentrations, lower SLA) and improve carbon balance (e.g., greater water use efficiency, lower respiration, higher F v /F m) compared to spruce in exposed sites, but had lower carbon balance under herb cover. Superior establishment success of pine in exposed microsites at treeline could thus be attributed to a suite of intrinsic physiological advantages that are apparent at the earliest stage of development.

Photoprotection, not increased growth, characterizes the response of Engelmann spruce (Picea engelmannii) seedlings to high light, even when resources are plentiful.

• To investigate the effects of resource limitation on the use of light by Engelmann spruce seedlings (Picea engelmannii), we examined the effects of nitrogen (N) supply on growth and physiological acclimation. • Seedlings were grown under a factorial combination of two levels of light (100%, 33% full light) and two levels of N-supply (100mg l-1 and 10mg l-1 ). Biomass, foliage physiology, and pigment composition were measured. • No significant differences were found in growth or photosynthetic capacity between seedlings grown under high and low light, regardless of whether seedlings were grown under conditions of high or low N-supply. Both a decrease in the capacity for light capture and an increase in the capacity for thermal dissipation of excess absorbed light occurred with growth at high relative to low light as well as at low relative to high N-supply. • Damage to foliage from excess light appeared to be avoided through a combination of downward adjustments in chlorophyll and upward adjustments in photoprotective xanthophyll cycle carotenoids.

Tree Shelters Improve the Survival and Growth of Planted Engelmann Spruce Seedlings in Southwestern Colorado

Abstract Shade-tolerant Engelmann spruce (Picea engelmannii) is a difficult species to reforest successfully in the high-elevation spruce-fir forests of the Rocky Mountains. This study investigated the use of plastic tree shelters as a form of shade protection and a means to improve the growth and survival of planted Engelmann spruce seedlings in southwest Colorado. A total of 1500 seedlings were planted into a 48 ha clearcut site at an average elevation of 3273 m. Treatments included four different colors of tree shelters and a control where seedlings were planted using the traditional shading method. This consisted of shading the seedlings using logging slash, stumps, and vegetation within the site. After two growing seasons, survival was 58% for the control treatment and ranged from 95 to 99% in the lighter three shelter color treatments. The darkest shelter color resulted in 95% mortality after the first growing season. Both height and diameter growth of surviving seedlings were significantly greater in the lightest two shelter color treatments as compared to the control treatment. These results indicate that tree shelters may provide an effective method of improving high-elevation Engelmann spruce reforestation programs. West. J. Appl. For. 16(3):114–120.

Nitrogen induced potassium deficiency in white spruce (Piceaglauca) and Engelmann spruce (Piceaengelmannii) seedlings

White spruce (Piceaglauca (Moench) Voss) and Engelmann spruce (Piceaengelmannii Parry ex Engelm.) seedlings grown for 2 or more years in sandy loam nursery soils in British Columbia often show yellow and necrotic shoot-tip symptoms. Chemical analysis of a white spruce and a white × Engelmann hybrid spruce provenance showed that the symptoms were associated with low needle K concentrations. After nursery growth was complete, growth tests showed that seedlings with symptoms took longer to flush and had 43% less shoot extension than normal green seedlings. To see why K fertilizer alone did not always cure the symptoms, 1.5-year-old Engelmann spruce seedlings were transplanted and grown for a further 1.5 years in a 4 × 3 × 3 factorial experiment (K level × N source × N level). Nitrogen fertilization increased growth and symptom occurrence, with sources resulting in more symptoms in the order (NH4)2SO4 < NH4NO3 < Ca(NO3)2. Potassium fertilization decreased symptoms, although not completely, but had no effect on growth. Shoot-tip NH4+ was positively correlated with symptoms, while higher levels of soil and shoot-tip K, as well as soil and shoot-tip Mg, were associated with reduction in symptoms. It was concluded that heavy N fertilization created requirements for K, and probably Mg, above the tissue concentrations normally regarded as adequate, and that K fertilization did not always eliminate symptoms because of a Mg requirement.

Physiological recovery of freezer-stored white and Engelmann spruce seedlings planted following different thawing regimes

Logistic problems of large-scale reforestation necessitate freezer-storage of conifer seedlings. Frozen stock is typically thawed slowly at low temperatures for up to several weeks before shipping to the plantation site, but the necessity of this practice is questionable. Experiments were conducted to study effects of different thawing regimes on photosynthetic recovery, frost hardiness, water relations and growth initiation in “interior spruce” (white spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmannii Parry) hybrid complex). One year-old container-grown seedlings were planted after 9 days post-storage thawing at 5–15 °C or still frozen, directly from the freezer. During a 29 day observation period after planting, both groups showed changes in xylem water potential (Ψw), carbon fixation (A), stomatal conductance (gs), chlorophyll a fluorescence and xanthophyll cycle pigments. Treatment differences in fluorescence and pigments peaked within one hour after planting. All differences in Ψw, A, gs, ratio of internal to external CO2 concentration (Ci/Ca), fluorescence, pigments and root number disappeared after 5 to 8 days. Terminal bud burst occurred 2.6 days earlier in the pre-thawed seedlings. When seedlings were rapidly thawed in the dark at 21 °C they achieved maximum Ψw (−0.2 MPa) in 3–4 hour. When evaluated 45 min after planting, A, gs, Ci/Ca and fluorescence values of rapidly thawed seedlings were intermediate between those for seedlings planted frozen or after 9 days slow thawing, showing that the recovery process was well underway a few hours after removal from the freezer. These results suggested that a suitable on-site operational protocol for rapid thawing might be to lay frozen bundles on the ground at ambient temperature overnight. In field trials of this method, rapidly thawed seedlings broke bud 3.3 days later than slowly thawed stock and also had greater frost hardiness at time of planting. Height, shoot and root mass did not differ after 3 months growth.

Effects of overtopping vegetation on light availability and growth of Engelmann spruce (Piceaengelmannii) seedlings

To examine the effects of overtopping vegetation on solar irradiance reaching Engelmann spruce (Piceaengelmannii Parry) seedlings and on crop seedling performance, neighborhood studies were established at six sites in mixed shrub–herb and fireweed communities of the Interior Cedar–Hemlock zone of southern British Columbia. These communities were dominated by mixtures of fireweed (Epilobiumangustifolium L.), thimbleberry (Rubusparviflorus Nutt.), red raspberry (Rubusidaeus L.), and (or) bracken fern (Pteridiumaquilinum (L.) Kuhn). Three hundred and eighty-eight planted Engelmann spruce seedlings, between 1 and 5 years of age, served as plot centers for measurements in 1990 and 1991. Vegetation had been clipped around 109 of these seedlings in 1988, 1989, and 1990. Seedling diameter and height were measured in the autumn of 1990 and 1991. Vegetation cover, vegetation height, and the fraction of full sunlight reaching the top branches of each spruce seedling were measured in midsummer of 1991. A simple competition index (CI), based on visually estimated percent cover, height of each species present within 1.26 m of the crop seedling, and crop-seedling height, can be used to estimate the fraction of full sunlight reaching crop seedlings. Measurements of transmittance through vegetation canopies are correlated with this competition index and could be useful as a separate, objective assessment of competition levels. Seedling growth was related to both seedling-needle biomass (at the beginning of the year) and either CI or the amount of light reaching crop seedlings during midsummer. Growth increased as needle biomass or irradiance reaching the seedling increased and decreased as CI increased. Since CI can be calculated from simple field measurements and since seedling growth is related to CI, this index has potential utility in evaluating the need for operational release treatments. Transmittance measurement provides an equally useful, and potentially more objective approach to evaluating the need for release treatment. Results from this study suggest that cumulative effects of competition result at least in part from effects on growth of seedling leaf mass.

In vitro regeneration of plantlets from embryonic and seedling explants of Engelmann spruce (Picea engelmannii Parry).

A protocol has been developed for the in vitro production of plantlets of Engelmann spruce. Embryos and various parts of Engelmann spruce seedlings formed multiple shoots when cultured on defined media containing a cytokinin. The site and time of occurrence of the shoot buds, as well as their number, differed in the various explants. The frequency of shoot-forming explants was influenced by the salt formulation used, the type and concentrations of cytokinins and their mode of application. Development of buds was achieved by transferring the explants to basal medium containing no growth regulators. Elongation of shoots was stimulated by reducing the concentration of salts and sugar, addition of activated charcoal and transferral to increased photoperiod and lower temperature regimes. Maximum rooting was induced by giving a pulse of high concentration of indolebutyric acid to the shoots. The roots developed within 8-10 weeks and the regenerated plantlets were transferred to soil under non-sterile conditions.

Taxonomic Implications of Monoterpene Compounds of Blue and Engelmann Spruces

Abstract The monoterpenes of cortical oleoresin collected from mature blue and Engelmann spruce have significant diagnostic potential in taxonomic studies of these species, while seedling cortical monoterpenes appear to be less useful. Cortical monoterpene compounds were analyzed in 38 blue and 13 Engelmann spruce in the Scotch Creek drainage in southwestern Colorado, and in their 6-months-old progeny. The objective was to explore the utility of monoterpenes in studying natural hybridization between the two species. Twenty-two compounds were detected in the cortical oleoresin of mature trees, twelve of which were identified. Species differences were generally quantitative, with most statistically significant. Blue spruce oleoresin contained higher levels of tricyclene, alpha-pinene, camphene, and bornyl acetate, while Engelmann spruce oleoresin contained higher levels of beta-pinene, 3-carene, terpinolene, and several unknown compounds. Monoterpene content of seedlings differed appreciably from that of mature parents. The large increase in beta-pinene in Engelmann spruce seedlings was the most striking. A discriminant function analysis of mature tree data distinguished between blue and Engelmann spruce with no misclassifications. Forest Sci. 32:725-734.

Estimation of cold hardiness of Douglas‐fir and Engelmann spruce seedlings by differential thermal analysis of buds*

SUMMARYLow temperature freezing points of conifer buds were determined by differential thermal analysis and were compared to results obtained in whole plant freezing tests of the same seedlings. To obtain well‐defined, meaningful exotherms, it was necessary to nucleate buds externally. The low temperature exotherms for buds occurred at temperatures very close to the lowest which seedlings tolerate with no visible injury. Thus, for Engelmann spruce and Douglas‐fir, differential thermal analysis may provide a convenient prediction of containerised tree seedling hardiness.

Stomatal control and the development of water deficit in Engelmann spruce seedlings during drought

The effects of soil drying on water relations of Engelmann spruce (Piceaengelmannii Engelm.) were studied by withholding water from 4-year-old potted seedlings in full sunlight and under a shade screen transmitting 55–60% light. During a period of 2 months, xylem pressure potential, water vapor conductance, and transpirational flux density gradually declined compared with well watered controls, with drying being more rapid in full sunlight. As drying progressed, xylem pressure potential at 0 transpiration (predawn potential) decreased and the slope of the relationship between xylem pressure potential and transpirational flux density became more negative. Hysteresis in the relationship occurred when predawn xylem pressure potential was −6 bars (1 bar = 105 Pa) or lower. Needle conductance during daylight hours decreased as the absolute humidity difference from leaf to air increased but conductances were lower in September than in August for given humidity differences. Xylem pressure potentials between −15 and −19 bars had no clear effect on conductance in August but apparently caused significant stomatal closure in September. Because of humidity-induced stomatal closure, evaporative demand had little effect on transpirational flux density over a broad range of humidity gradient. Thus increased leaf-to-air vapor gradients for transpiration are not always accompanied by increased transpiration.

Effect of light intensity during extended photoperiod on growth of amabilis fir, mountain hemlock, and white and Engelmann spruce seedlings

Abiesamabilis (Dougl.) Forbes, Tsugamertensiana (Bong.) Carr., Piceaglauca (Moench) Voss, and Piceaengelmannii Parry seedlings were grown in an outdoor container nursery using one high-pressure sodium vapor lamp to provide a 24-h photoperiod. Eight intensities of lighting were arranged, viz., 220, 80, 40, 20, 12, 8, 5, and 0 lx.Extending the photoperiod and increasing the light intensity had a significant positive effect on the length and weight of seedling shoots and delayed terminal bud set. Root growth response to these treatments was negative, although the differences were rarely significant. Seedlings grown under a light intensity of 220 lx were the largest. The minimum intensity required to produce seedling shoot lengths which were significantly larger than the controls was in the range 20–80 lx.

Chlorosis of planted Engelmann spruce seedlings unrelated to nitrogen content

Shade-tolerant Engelmann spruce (Picea engelmannii Parry) seedlings generally became chlorotic when exposed to direct sunlight under several different growing conditions, whether grown in pots, in plantations, or in transplant beds at high or low elevations. Shaded seedlings under the same growing conditions remained a normal green color. Chlorosis was attributed to solarization, not to nitrogen deficiency. That conclusion was supported by the fact that the nitrogen content of shaded and unshaded seedlings was similar regardless of the growing conditions.

OBSERVATIONS ON FOLIAGE NUTRIENT CONTENT OF SEVERAL CONIFEROUS TREE SPECIES IN BRITISH COLUMBIA

Concentration of nitrogen, phosphorus, potassium, calcium, magnesium and sulphur in needles of alpine fir, amabilis fir, western red cedar, Douglas fir, western hemlock, lodgepole pine, Engelmann spruce and Sitka spruce trees growing in a number of areas of British Columbia was determined.Concentration of N, P, K, Ca, Mg and S in current needles of three groups of alpine fir seedlings was 1.05-1.85, 0.18-0.26, 0.70-1.08, 0.29-.044, 0.07-0.11, and 0.12-0.16 per cent, respectively. The nutrient content in the same order was 0.99, 0.16, 1.20, 0.30, 0.08, and 0.12 per cent in a single group of amabilis fir samples.In the lone set of western red cedar samples the concentrations of N, P, K, Ca, Mg and S were in the order of 0.73, 0.13, 0.52, 1.16, 0.10 and 0.07 per cent.The percentage of the six nutrients in current Douglas fir needles from seven locations was 0.88-1.37, 0.12-0.22, 0.38-0.70, 0.16-0.44, 0.07-0.18, and 0.14-0.25 for N, P, K, Ca, Mg and S, respectively.The nutrient content of current needles of western hemlock from three sites was N = 0.86-1.17, P = 0.11-0.19, K = 0.28-0.57, Ca = 0.18-0.27, Mg = 0.08-0.12 and S = 0.10-0.15 per cent.Nitrogen, P, K, Ca, Mg and S concentration in current needles from three lots of lodgepole pine seedlings was 1.18-1.77, 0.15-0.18, 0.45-0.62, 0.16-0.26, 0.11-0.14 and 0.12-0.21 per cent, respectively. The corresponding values in needles from older trees were in the order 0.97-1.12, 0.09-0.12, 0.35-0.39, 0.15-0.16, 0.08-0.12 and 0.09-0.11.Per cent N, P, K, Ca, Mg and S in current needles of three groups of Engelmann spruce seedlings was in the order 1.26-1.72, 0.21-0.29, 0.71-0.80, 0.44-0.58, 0.13-0.15 and 0.13-0.19. Concentration of these nutrients in older trees was 0.92-1.08, 0.20, 0.70-0.88, 0.28-0.33, 0.11-0.12 and 0.12-0.14 per cent, respectively.