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1

Electronic Resource

Effects of climatic variability on the annual carbon sequestration by a boreal aspen forest (1999)

Chen, W. J. ; Black, T. A. ; Yang, P. C. ; [et al.]

Oxford, UK : Blackwell Science, Ltd

Global change biology 5 (1999), S. 0

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ISSN: 1365-2486

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography

Notes: To evaluate the carbon budget of a boreal deciduous forest, we measured CO2 fluxes using the eddy covariance technique above an old aspen (OA) forest in Prince Albert National Park, Saskatchewan, Canada, in 1994 and 1996 as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). We found that the OA forest is a strong carbon sink sequestering 200 ± 30 and 130 ± 30 g C m–2 y–1 in 1994 and 1996, respectively. These measurements were 16–45% lower than an inventory result that the mean carbon increment was about 240 g C m–2 y–1 between 1919 and 1994, mainly due to the advanced age of the stand at the time of eddy covariance measurements. Assuming these rates to be representative of Canadian boreal deciduous forests (area ≈ 3 × 105 km2), it is likely they can sequester 40–60 Tg C y–1, which is 2–3% of the missing global carbon sink.The difference in carbon sequestration by the OA forest between 1994 and 1996 was mainly caused by the difference in leaf emergence date. The monthly mean air temperature during March–May 1994, was 4.8 °C higher than in 1996, resulting in leaf emergence being 18–24 days earlier in 1994 than 1996. The warm spring and early leaf emergence in 1994 enabled the aspen forest to exploit the long days and high solar irradiance of mid-to-late spring. In contrast, the 1996 OA growing season included only 32 days before the summer solstice. The earlier leaf emergence in 1994 resulted 16% more absorbed photosynthetically active radiation and a 90 g C m–2 y–1 increase in photosynthesis than 1996. The concomitant increase in respiration in the warmer year (1994) was only 20 g C m–2 y–1. These results show that an important control on carbon sequestration by boreal deciduous forests is spring temperature, via the influence of air temperature on the timing of leaf emergence.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2486.1998.00201.x

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2

Electronic Resource

Annual cycles of water vapour and carbon dioxide fluxes in and above a boreal aspen forest (1996)

BLACK, T. A. ; HARTOG, G. ; NEUMANN, H. H. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Global change biology 2 (1996), S. 0

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ISSN: 1365-2486

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography

Notes: Water vapour and CO2 fluxes were measured using the eddy correlation method above and below the overstorey of a 21-m tall aspen stand in the boreal forest of central Saskatchewan as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). Measurements were made at the 39.5-m and 4-m heights using 3-dimensional sonic anemometers (Kaijo-Denki and Solent, respectively) and closed-path gas analysers (LI-COR 6262) with 6-m and 4.7-m long heated sampling tubing, respectively. Continuous measurements were made from early October to mid-November 1993 and from early February to late-September 1994. Soil CO2 flux (respiration) was measured using a LI-COR 6000-09 soil chamber and soil evaporation was measured using Iysimetry.The leaf area index of the aspen and hazelnut understorey reached 1.8 and 3.3, respectively. The maximum daily evapotranspiration (E) rate was 5–6 mm d−1. Following leaf-out the hazelnut and soil accounted for 22% of the forest E. The estimated total E was 403 mm for 1994. About 88% of the precipitation in 1994 was lost as evapotranspiration.During the growing season, the magnitude of half-hourly eddy fluxes of CO2 from the atmosphere into the forest reached 1.2 mg CO2 m−2 s−1 (33 μmol C m−2 s−1) during the daytime. Downward eddy fluxes at the 4-m height were observed when the hazelnut was growing rapidly in June and July. Under well-ventilated night-time conditions, the eddy fluxes of CO2 above the aspen and hazelnut, corrected for canopy storage, increased exponentially with soil temperature at the 2-cm depth. Estimates of daytime respiration rates using these relationships agreed well with soil chamber measurements. During the 1994 growing season, the cumulative net ecosystem exchange (NEE) was -3.5 t C ha−1 y−1 (a net gain by the system). For 1994, cumulative NEE, ecosystem respiration (R) and gross ecosystem photosynthesis (GEP = R - NEE) were estimated to be -1.3, 8.9 and 10.2 t C ha−1 y−1 respectively. Gross photosynthesis of the hazelnut was 32% of GEP.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2486.1996.tb00074.x

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3

Electronic Resource

Theoretical determination of the surface energy balance and thermal regimes of bare soils (1985)

Novak, M. D. ; Black, T. A.

Springer

Boundary layer meteorology 33 (1985), S. 313-333

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ISSN: 1573-1472

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract An analytical theory that determines the thermal regimes in the soil and the thermal and moisture regimes in the atmosphere for bare surfaces is derived. Both soil and atmospheric thermal properties are assumed to be power functions of depth and height, respectively. Evaporation is determined using a surface resistance to vapour flow. Fourier superposition is used to represent nonsinusoidal variations in time due to effects such as variable cloud cover. The theory is in acceptable agreement with micrometeorological measurements made at two bare soil sites of contrasting surface bulk density. It is concluded that the surface resistance model for evaporation is applicable to bare soils which remain wet at depth, particularly if their surface is loosened. The theory is used to predict the diurnal thermal regimes of saturated and dry sand, loam, and peat soils.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00116682

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4

Electronic Resource

Turbulent heat transfer from a sparsely vegetated surface: Two-component representation (1993)

Otterman, J. ; Novak, M. D. ; Starr, D. O. C.

Springer

Boundary layer meteorology 64 (1993), S. 409-420

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ISSN: 1573-1472

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract The conventional calculation of heat fluxes from a vegetated surface, involving the coefficient of turbulent heat transfer, which increases logarithmically with surface roughness (commonly taken as about 0.12 of the plant height), appears inappropriate for highly structured surfaces such as desertscrub or open forest. An approach is developed here for computing sensible heat flux from sparsely vegetated surfaces, where the absorption of insolation and the transfer of absorbed heat to the atmosphere are calculated separately for the plants and for the soil. This approach is applied to a desert-scrub surface for which the turbulent transfer coefficient of sensible heat flux from the plants is much larger than that from the soil below, as shown by an analysis of plant, soil and air temperatures measured in an animal exclosure in the northern Sinai. The plant density is expressed as the sum of products (plant-height) x (plant-diameter) of plants per unit horizontal surface area (the dimensionless silhouette parameter of Lettau). The solar heat absorbed by the plants is assumed to be transferred immediately to the airflow. The effective turbulent transfer coefficientk g-eff for sensible heat from the desert-scrub/soil surface computed under this assumption increases sharply with increasing solar zenith angle, as the plants absorb a greater fraction of the incoming irradiation. The surface absorptivity (the co-albedo) also increases sharply with increasing solar zenith angle, and thus the sensible heat flux from such complex surfaces (which include open forests) is a much broader function of time of day than when computed under constantk g-eff and constant albedo assumptions. The major role that desert-fringe plants play in the genesis of convection and advection cannot be evaluated properly in the conventional calculations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00711708

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5

Electronic Resource

E-ε modelling of turbulent air flow downwind of a model forest edge (1996)

Liu, J. ; Chen, J. M. ; Black, T. A. ; [et al.]

Springer

Boundary layer meteorology 77 (1996), S. 21-44

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ISSN: 1573-1472

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract A two-dimensional E-ε model, which included the effects of plant-atmosphere interaction, was used to simulate air flow downwind of forest edges for the purpose of predicting the microclimate in forest openings. A suitable set of wall functions was selected to consider the aerodynamic effects of the ground in the opening. The model with discretization and parameter schemes was validated using a set of data from a wind-tunnel experiment. The simulated wind speed and turbulence kinetic energy closely agreed with the measured values. After validation, the model was used to predict eddy diffusivity in the lee of the forest edge. The modelled spatial distribution of the eddy diffusivity agreed in general with that calculated using wind-tunnel measurements. The usefulness and limitations of the E-ε model are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00121857

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6

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Micrometeorological changes associated with vegetation removal and influencing desert formation (1990)

Novak, M. D.

Springer

Theoretical and applied climatology 42 (1990), S. 19-25

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ISSN: 1434-4483

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Summary The effects of vegetation removal on the energy balance components, soil and air temperatures, and atmospheric vapour densities are predicted using a recently developed analytical theory. The results show that the sum of daily average sensible and latent heat flux densities decreases as the surface resistance and albedo increase and the surface roughness decreases, which according to some numerical models implies reductions in rainfall. For a dry surface daytime atmospheric heating decreases with vegetation removal because albedo and soil admittance increase and atmospheric admittance decreases; according to another model this should reduce precipitation. The results show that surface temperature is not an appropriate diagnostic measure of sensible heat flux density, even under constant meteorological conditions, when changes in surface roughness also occur. Analysis of some surface temperatures measurements made in the Negev and the Sinai suggests that understanding the turbulent processes occurring in the roughness sublayer, when the surface is partially covered with vegetation, is critical in assessing the micrometeorological changes associated with vegetation removal and desert formation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00865522

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7

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Core aeration of sand-based putting greens in the Lower Fraser Valley of British Columbia (2007)

Sorokovsky, P. ; Krzic, M. ; Novak, M D

Canadian Science Publishing

In: Canadian Journal of Soil Science. 2007; 87(1): 103-111. Published 2007 Jan 01. doi: 10.4141/s05-073.

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Publication Date: 2007-01-01

Description: Core aeration, a management practice originally developed for soil-based putting greens, is still commonly used on sand-based greens. The study objective was to determine the effects of core aeration on soil properties of sand-based putting greens in the Lower Fraser Valley of British Columbia. The experiment was laid out as a randomized complete block design with three replications. The study treatments were regular management practices, including core aeration (CA) carried out in spring and late summer, and regular management practices, but no core aeration (NCA). Each core aeration event impacted 5% of the surface area. Treatments with and without core aeration had similar soil organic matter content, root weight density, and soil bulk density. The CA treatment was generally drier than NCA. Water infiltration was greater on CA than NCA, but only for 1 mo following core aeration. Core aeration generally reduced soil penetration resistance within the mat layer relative to treatment without this practice. On both treatments, soil penetration resistance consistently exceeded 4000 kPa below about 13 cm depth preventing deeper root growth. The limited benefits of the low-surface-area-impact core aeration on the maturing sand-based putting greens in a humid maritime climate suggest that this practice might not be worth doing (at a low surface area impact); however, additional, more detailed studies are needed to confirm this. Key words: Turf management, golf course management, soil penetration resistance, water infiltration

Print ISSN: 0008-4271

Electronic ISSN: 1918-1841

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition