Conifer-seedling success and microclimate at different levels of herb and shrub cover in a Rhododendron–Vaccinium–Menziesia community of south central British Columbia

1991 ◽  
Vol 21 (6) ◽  
pp. 858-866 ◽  
Author(s):  
K. D. Coates ◽  
W. H. Emmingham ◽  
S. R. Radosevich
Keyword(s):  
British Columbia ◽  
Soil Water ◽  
Vegetation Cover ◽  
Mineral Soil ◽  
Soil Water Potential ◽  
Pressure Potential ◽  
Engelmann Spruce ◽  
South Central ◽  
Xylem Pressure Potential ◽  
Conifer Seedling

The influence of various amounts of shrub and herb cover on microclimate and on survival and growth of Engelmann spruce (Piceaengelmannii Parry) and lodgepole pine (Pinuscontorta Dougl.) was examined in plots established in the Engelmann Spruce – Subalpine Fir zone of south central British Columbia. The planting sites varied from those with undisturbed vegetation to bare plots with exposed mineral soil. After three growing seasons, survival of both conifer species was greater than 95%, except at the highest levels of vegetation cover, where survival was 76 to 80%. Diameter was the conifer growth measure most responsive to reduction in adjacent vegetation. In the absence of adjacent vegetation, mean diameters of spruce and pine seedlings were 44 and 84% greater, respectively, than those of seedlings planted in undisturbed vegetation, and mean diameters increased still more when mineral soil was exposed. Height growth was less responsive to reduction in adjacent vegetation. Soil water potential, never more negative than −0.01 MPa, was the same at all levels of vegetation cover. Midday and predawn xylem pressure potential of spruce did not vary with the amount of vegetation. Although soil water was ample, moderate water stress occurred, most likely because uptake was restricted by low soil temperatures. Results suggest that soil temperature, air temperature, and light level are the primary factors controlling conifer seedling performance in an undisturbed vegetation community.

Comparison of Water Relations and Osmotic Adjustment in Sorghum and Cowpea Under Field Conditions

1983 ◽  
Vol 10 (5) ◽  
pp. 423 ◽  
Author(s):  
KA Shackel ◽  
AE Hall
Keyword(s):  
Soil Water ◽  
Osmotic Adjustment ◽  
Leaf Conductance ◽  
Field Conditions ◽  
Soil Water Depletion ◽  
Pressure Potential ◽  
Water Depletion ◽  
Diurnal Patterns ◽  
Diurnal Range ◽  
Xylem Pressure Potential

Seasonal and diurnal patterns of xylem pressure potential, Ψx, and osmotic potential, Ψs, were compared using contrasting genotypes of sorghum [Sorghum bicolor (L.) Moench] and cowpea [Vigna unguiculata (L.) Walp.] under frequently imgated 'wet' and water-limited 'dry' field conditions. Generally, differences in Ψx and Ψs among genotypes within each species were small compared with differences between the two species. Sorghum exhibited a larger diurnal range and larger differences between wet and dry treatments for Ψx, Ψs, and estimates of bulk leaf turgor than did cowpea. Seasonal and drought- induced osmotic adjustment occurred in sorghum, but not in cowpea. Diurnal patterns of leaf conductance indicated that, under the dry treatment, cowpea avoided the occurrence of large plant water deficits by substantial reductions in leaf conductance, especially at midday, whereas sorghum maintained moderate values of leaf conductance throughout the day. Cowpea exhibited a larger diurnal range of leaf conductance and larger differences between wet and dry treatments than did sorghum. Differences were not observed between the species in overall soil water depletion or in root activity as estimated from profiles of soil water depletion until senescence occurred in cowpea. Sorghum genotypes that had been selected on the basis of differences in Ψs did exhibit significant differences in average values of leaf conductance and total soil water depletion, but the genotype that had the lowest Ψs (M35-1) also had the lowest leaf conductance and the least soil water depletion.

Characteristics of stomatal diffusion resistance in a Douglas fir forest exposed to soil water deficits

1977 ◽  
Vol 7 (4) ◽  
pp. 595-604 ◽  
Author(s):  
C. S. Tan ◽  
T. A. Black ◽  
J. U. Nnyamah
Keyword(s):  
Soil Water ◽  
Soil Water Potential ◽  
High Stress ◽  
Vapour Pressure Deficit ◽  
Douglas Fir ◽  
Diffusion Resistance ◽  
Total Water ◽  
Pressure Potential ◽  
Relationship Of ◽  
The Relationship

As part of a 2-year study of the effect of thinning on evapotranspiration in Douglas fir (Pseudotsugamenziesii (Mirb.) Franco), the relationship between stomatal diffusion resistance (rs) and environmental variables were studied. Research was conducted in an unthinned stand (1840 stems ha−1) with negligible undergrowth and a thinned stand (840 stems ha−1) with substantial salal (Gaultheriashallon Pursh) undergrowth. During the daytime rs was mainly related to the soil water potential (ψs) and the vapour pressure deficit (v.p.d.) of the canopy air. Daytime values of rs for Douglas fir ranged from 2 to 60 s cm−1 for values of v.p.d. between 4 and 24 mb (4 and 24 × 102 Pa) and values of ψs between 0 and −12.5 bars (0 and −12.5 × 105 Pa). Although increasing rs was usually associated with decreasing pressure potential of the twig xylem (ψt), increasing rs appeared to be associated with increasing ψt when the v.p.d. was high. Stress history was found to cause a shift in the relationship of rs to ψt, but had little effect on the relationship of rs to v.p.d. and ψs. Daytime values of rs for salal ranged from 2 to 45 s cm−1. This stomatal behaviour suggests that as the soil dried out, salal transpiration accounted for an increasing fraction of the total water loss by the thinned stand.

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

1979 ◽  
Vol 9 (3) ◽  
pp. 297-304 ◽  
Author(s):  
Merrill R. Kaufmann
Keyword(s):  
Flux Density ◽  
Stomatal Closure ◽  
Absolute Humidity ◽  
Pressure Potential ◽  
Evaporative Demand ◽  
Xylem Pressure ◽  
Full Sunlight ◽  
Engelmann Spruce ◽  
Xylem Pressure Potential ◽  
The Relationship

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.

Water relations of loblolly pine trees in southeastern Oklahoma following precommercial thinning

1990 ◽  
Vol 20 (9) ◽  
pp. 1508-1513 ◽  
Author(s):  
Bert M. Cregg ◽  
Thomas C. Hennessey ◽  
Philip M. Dougherty
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Loblolly Pine ◽  
Soil Water Potential ◽  
Basal Area ◽  
Leaf Conductance ◽  
Pressure Potential ◽  
Precommercial Thinning ◽  
Xylem Pressure ◽  
Xylem Pressure Potential

Xylem pressure potential, leaf conductance, transpiration, and soil moisture were measured during three summers following precommercial thinning of a 10-year-old stand of loblolly pine (Pinustaeda L.) in southeastern Oklahoma. The stand was thinned to three target basal-area levels: 5.8, 11.5, and 23 m2•ha−1 (control). Soil water potential increased significantly in response to thinning during the summer of each year studied. However, plant water relations were relatively unaffected by the treatments. Significant thinning effects on diurnal xylem pressure potential were observed on only 7 of 55 measurement periods. Treatment differences in conductance and transpiration observed during the first year of the study appeared to be related to differences in light interception and crown exposure. Regression analysis indicated response of leaf conductance and transpiration to predawn xylem pressure potential and vapor pressure deficit was not affected by the thinning treatments. Overall, the results of this study are consistent with a hypothesis in which transpiration, leaf area, and water potential interact to form a homeostatic relationship.

Pathology of conifer seed and timing of germination in high-elevation subalpine fir and Engelmann spruce forests of the southern interior of British Columbia

1999 ◽  
Vol 29 (2) ◽  
pp. 187-193 ◽  
Author(s):  
Jianwen Zhong ◽  
Bart J van der Kamp
Keyword(s):  
British Columbia ◽  
Forest Floor ◽  
Mineral Soil ◽  
Seed Viability ◽  
Low Frequency ◽  
High Elevation ◽  
Subalpine Fir ◽  
Engelmann Spruce ◽  
Black Mold ◽  
Nurse Logs

Unstratified seed of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in nylon mesh bags was placed on various natural and disturbed forest floor seed beds in the Engelmann Spruce - Subalpine Fir Zone in the southern interior of British Columbia in September 1995 and recovered just before snow melt in June 1996. Fifty-two and 86% of the viable spruce and fir seed, respectively, had germinated before snowmelt. Germination under snow may be an adaptation of these high-elevation species to short cool growing seasons. Seed viability at recovery was significantly lower on undisturbed forest floor seed beds (spruce, 13%; fir, 12%) than on exposed mineral soil (spruce, 57%; fir, 42%). Viability of seed placed on nurse logs was 38 and 23% for spruce and fir, respectively. Isolation from ungerminated seed yielded a Rhizoctonia sp., an as yet unidentified black mold at high frequencies, and several other seed pathogens at low frequency. Multiple linear regression of the frequency of isolation of Rhizoctonia and black mold on seed viability was highly significant for both tree species. Seed pathogens appear to cause a major loss of seed and seedlings in these forests, and this may explain both the common occurrence of regeneration on nurse logs and the requirement of mineral soil seed beds for adequate regeneration.

A Cold Temperature Error in the Pressure Chamber Technique

1974 ◽  
Vol 4 (3) ◽  
pp. 413-416
Author(s):  
A. Kent Evans ◽  
C. P. P. Reid
Keyword(s):  
Pressure Chamber ◽  
Cold Temperature ◽  
Temperature Error ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Engelmann Spruce ◽  
Severe Water Stress ◽  
Xylem Pressure Potential ◽  
Temperature Heat ◽  
Soil Temperatures

Pressure chamber data for Engelmann spruce indicate that a cold temperature error causes artificially low (more negative) xylem pressure potential (Ψxp) values below −0.5 °C xylem temperature. Heat of compression in the chamber causes partial thawing of the frozen sample allowing some water to be forced from the twig at a reasonable, although artificially low, Ψxp value. It is important that the investigator know sample temperature in order not to misinterpret these low Ψxp values as indicative of severe water stress due to decreased absorption of water by root systems at low soil temperatures.

scholarly journals Post-glacial diatom-inferred aquatic changes in Sicamous Creek Lake, British Columbia, Canada

2014 ◽  
Vol 27 (3) ◽  
pp. 233-256 ◽  
Author(s):  
Andrea C. Voit ◽  
Richard J. Hebda ◽  
Julien M.J. Racca ◽  
Reinhard Pienitz ◽  
Ian R. Walker ◽  
...  
Keyword(s):  
British Columbia ◽  
Open Water ◽  
Late Glacial ◽  
High Elevation ◽  
Low Light ◽  
Subalpine Fir ◽  
Engelmann Spruce ◽  
South Central ◽  
Inferred Ph

Diatom analyses of sediments from a high elevation lake situated in an Engelmann Spruce - Subalpine Fir (ESSF) forest of south-central British Columbia, Canada, reveal long-term climate and water chemistry change. During the transition from the late-glacial / Pleistocene to the xerothermic early Holocene, small, benthic Fragilaria diatoms species that grew under low light conditions in Sicamous Creek Lake gave way to planktonic Cyclotella species that require open-water conditions. Warm temperatures in the mesothermic Holocene are indicated by smaller Cyclotella species and large, benthic pennate diatoms. Diatom communities reflected Neoglacial cooling in the late Holocene, with abundant Nitzschia fonticola and Achnanthes minutissima. Small, benthic Fragilaria regained abundance, suggesting cooling and conditions similar to the late-glacial interval. Diatom community composition responded to the deposition of the Mt. Mazama and Mt. St. Helens tephras, though the Mazama eruption caused greater change in relative abundance of various taxa within the assemblage. Correspondence analysis shows distinct communities have occurred since the initiation of sedimentation, likely due to climate controlled landscape and vegetation changes; diatom-inferred pH values using various models and training sets show limited acidification change occurred through the lake’s history.

Effects of fertilization on the nutrition and growth of a slow-growing Engelmann spruce plantation in south central British Columbia

1992 ◽  
Vol 22 (11) ◽  
pp. 1617-1622 ◽  
Author(s):  
R.P. Brockley
Keyword(s):  
British Columbia ◽  
Tree Growth ◽  
Nitrogen Nutrition ◽  
Ferrous Sulphate ◽  
Nutrient Deficiencies ◽  
Height Increment ◽  
Growth Responses ◽  
Poor Growth ◽  
Engelmann Spruce ◽  
South Central

A study was undertaken to investigate the effects of ground and foliar fertilizer applications on the growth of a 15-year-old Engelmann spruce (Piceaengelmannii Parry) plantation in the south central interior of British Columbia. The site had been broadcast burned prior to plantation establishment, and poor growth performance and pretreatment foliar analyses indicated that multiple nutrient deficiencies were likely growth limiting. Fertilization has had a very strong positive influence on height increment and branch elongation. Although growth responses were minimal in the 1st year after treatment, cumulative increases in height increment over the next 2 years averaged 41 cm (range 28–48 cm) greater than those recorded in unfertilized trees. In relative terms, these responses averaged 102% (range 90–120%). Improvements in branch increment over this 2-year period also averaged 102% (range 85–115%). Results indicate that the majority of the growth response has been due to improved nitrogen nutrition. Combined ground applications of nitrogen and a "complete mix" fertilizer were no better than nitrogen alone in stimulating tree growth. The effectiveness of 2% ferrous sulphate and sodium sulphate sprays was probably adversely affected by foliar scorching following spray application. However, despite foliar burning, results indicate that trees may respond favourably to iron applications if accompanied by ground applications of nitrogen and other deficient nutrients (likely sulphur). Because the study design did not allow distinction of cause and effect, with respect to the consequences of the prior broadcast burn, it cannot be stated conclusively that burning is responsible for inadequate stand nutrition and poor tree growth on this site. However, when combined with evidence of impaired nutrition following slash burning from other studies, it may be safely inferred that burning will exacerbate existing nutritional problems and that fertilization under these conditions may at least temporarily improve plantation performance.

Soil microclimate and nitrogen availability 10 years after mechanical site preparation in northern British Columbia

2005 ◽  
Vol 35 (8) ◽  
pp. 1854-1866 ◽  
Author(s):  
M D MacKenzie ◽  
M G Schmidt ◽  
L Bedford
Keyword(s):  
British Columbia ◽  
Soil Temperature ◽  
Soil Water ◽  
Nitrogen Availability ◽  
Mineral Soil ◽  
Growing Season ◽  
Site Preparation ◽  
Total Carbon ◽  
Significant Treatment ◽  
Mechanical Site Preparation

Mechanical site preparation (MSP) changes the distribution and character of forest floor and mineral soil and may affect soil nutrient availability, soil water content, and soil temperature. The effects of different kinds of MSP were compared to a control in the tenth growing season at two research sites in northern British Columbia. To compare MSP results with those of the natural disturbance regime, a burned windrow treatment was also included in the analysis. The bedding plow, fire, and madge treatments all had significantly greater crop-tree growth compared to the control. The bedding plow and madge treatments had significantly lower soil bulk density, higher soil temperature, and lower soil water throughout the growing season compared with that of the control. The bedding plow also resulted in significantly higher concentrations of total carbon, total nitrogen, NH4+, and NO3–than that of the control, at both the 0–10 and 10–20 cm depths. The madge rotoclear resulted in significantly greater potential mineralizable N than that of the control. Ionic resins bags, installed for one growing season, did not show any significant treatment differences in available soil nitrogen. MSP did not reduce soil fertility on these sites when compared with an untreated control, but it is difficult to say that it improved it.

Stomatal conductance patterns and environment in high elevation phreatophytes of Wyoming

1991 ◽  
Vol 69 (3) ◽  
pp. 647-655 ◽  
Author(s):  
Jeffrey R. Foster ◽  
William K. Smith
Keyword(s):  
Stomatal Conductance ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
High Elevation ◽  
Pressure Potential ◽  
Previous Night ◽  
Threshold Response ◽  
Populus Angustifolia ◽  
Xylem Pressure Potential ◽  
Air Vapor Pressure Deficit

High-elevation (2305 m) phreatophytes (cottonwood, Populus angustifolia James, and willows, Salix monticola Nutt. and Salix exigua Bebb) in southeastern Wyoming commonly showed a pattern of increasing stomatal conductance (g1) throughout the day, despite minimum leaf water potentials (ψ1) as low as −2.7 MPa. Diurnally, light and leaf temperature were the most important variables influencing g1, but there were also threshold values of ψ1 and leaf-to-air vapor pressure deficit for stomatal closure. Seasonally, maximum daily g1 (gmax) was similar between species, was positively related to minimum air temperature the previous night, and showed a threshold response to soil temperature. Two types of evidence existed for large soil-to-leaf conductances (gs–l) and for liquid water being available to the roots. The first was no change in ψ1 despite increasing transpiration during the afternoon. The second was rapid evening recovery of ψ1 often to values higher than mean soil water potential to 60-cm depth. The combination of low atmospheric pressures at high elevation, large gs–l, and access to a water table may explain how these phreatophytes attained gmax of 0.8–0.9 mol m−2 s−1, much higher than gmax of low-elevation phreatophytes or high-elevation nonphreatophytes. Key words: Populus, Salix, phreatophyte, stomatal conductance, xylem pressure potential.

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