Forest Of Central Saskatchewan Research Articles

Assessing scalar concentration footprint climatology and land surface impacts on tall-tower CO2 concentration measurements in the boreal forest of central Saskatchewan, Canada

Reducing the large uncertainties in current estimates of CO2 sources and sinks at regional scales (10(2)-10(5) km(2)) is fundamental to improving our understanding of the terrestrial carbon cycle. Continuous high-precision CO2 concentration measurements on a tower within the planetary boundary layer contain information on regional carbon fluxes; however, its spatial representativeness is generally unknown. In this study, we developed a footprint model (Simple Analytical Footprint model based on Eulerian coordinates for scalar Concentration [SAFE-C]) and applied it to two CO2 concentration towers in central Canada: the East Trout Lake 106-m-tall tower (54A degrees 21'N, 104A degrees 59'W) and the Candle Lake 28-m-high tower (53A degrees 59'N, 105A degrees 07'W). Results show that the ETL tower's annual concentration footprints were around 10(3)-10(5) km(2). The monthly footprint climatologies in summer were 1.5-2 times larger than in winter. The impacts of land surface carbon flux associated with heterogeneous distribution of vegetation types on the CO2 concentration measurements were different for the different heights, varied with a range of +/- 5 % to +/- 10 % among four heights. This study indicates that concentration footprint climatology analysis is important in interpreting the seasonal, annual and inter-annual variations of tower measured CO2 concentration data and is essential for comparing and scaling regional carbon flux estimates using top-down or bottom-up approaches.

Factors controlling the interannual variability in the carbon balance of a southern boreal black spruce forest

Factors controlling the seasonal and interannual variability of net ecosystem productivity (FNEP), gross ecosystem photosynthesis (Pg), ecosystem respiration (Re) and evapotranspiration (E) of a mature boreal black spruce forest in central Saskatchewan, Canada were investigated using eight years (1999–2006) of continuous eddy covariance measurements. During 2000–2006, which included a three‐year drought, the forest was a weak sink for CO2 with annual FNEP ranging from 27 to 80 g C m‐2 (56 ± 21 g C m−2 a−1). The beginning of the growing season occurred when daily mean air temperature exceeded 4°C and the near surface soil temperature equaled or exceeded 0°C. The length of the growing season varied from 186 to 232 days. During the extreme drought year (2003), the smaller reduction in annual Pg than in Re resulted in highest FNEP of the record. Annual FNEP decreased slightly with increasing soil water content; however, there was evidence of increased FNEP due to high water table conditions in 2004 because of the slightly higher decrease in Re than Pg. Although bulk surface conductance (gs) decreased significantly during the dry conditions in 2003, the associated increase in D prevented a significant drop in E, which resulted in only a slight decline in evaporative fraction and almost no change in water use efficiency. Interannual variation inPg, Re and FNEP in the early growing season (April–June) and late growing season (July–September) was controlled by air temperature and soil water content, respectively. However, spring (April–May) mean air temperature was the main factor determining the interannual variation in annual FNEP. The effect of late growing season soil water content on annual Pg and Re was greater than its effect on annual FNEP. The results emphasize the need to consider soil moisture conditions as well as temperature when simulating the response of the carbon balance components of this ecosystems to climate change.

Biting Midges (Diptera: Ceratopogonidae) from the English Sundew, Drosera anglica Hudson (Droseraceae), at Two Fens in Saskatchewan, Canada

The plant-arthropod interactions of a native carnivorous plant, the English sundew, Drosera anglica Hudson, were studied in the Nisbet Provincial Forest of central Saskatchewan, Canada during July-August 2000 and June-August 2001. The principal insect groups collected from sundew leaves were biting and predaceous midges (Diptera: Ceratopogonidae) and non-biting midges (Chironomi- dae), in nearly equal proportions. More than 1,600 individuals of each of these primitive flies were collected each year, with each family representing 30-35% of total identifiable prey. Fifteen species of ceratopogonids were identified in seven genera, with the majority (75.7%) being either Atrichopogon websteri (Coquillett) or Dasyhelea spp. The overall sex ratio of ceratopogonids was 15:1, females to males.

The Pegogamaw Crees and Their Ancestors: History and Archaeology in the Saskatchewan Forks Region

In the period ca. A.D. 1400-1700 the Selkirk composite was present in the boreal forest of central Saskatchewan, with the Mortlach phase in the aspen parklands and grasslands to the immediate south and the Rainy River composite (Duck Bay complex) in the forests of east central Saskatchewan (and adjacent Manitoba). While there is almost certainly no exact correlation between these late precontact archaeological expressions and historically known ethnic groups, it is proposed that the Selkirk materials are largely the product of ancestral Crees, the Rainy River of ancestral Nakota, and the Mortlach of ancestral Gros Ventre.In the mid-eighteenth century, the employees of the Hudson’s Bay Company (HBC) recognized by name several named Cree groups in the western Canadian interior. Among these were the Pegogamaw Crees who were centered on a region extending through the upper Saskatchewan River and the adjacent lower South and North Saskatchewan Rivers. In the upper Saskatchewan River valley a variation of the Selkirk composite - the Pehonan complex - has been recognized. It is likely, therefore, that the Pehonan complex was the product of ancestral Pegogamaw Crees.

Inter-annual variability in the leaf area index of a boreal aspen-hazelnut forest in relation to net ecosystem production

The seasonal phenology of the leaf area index (LAI) is a major determinant of net ecosystem production in deciduous forest ecosystems. This study describes seasonal and inter-annual differences in LAI in a boreal aspen-hazelnut forest in central Saskatchewan, Canada, between 1994 and 2003, and relates the differences in LAI to annual net ecosystem production ( F NEP). A robust method is developed to fill gaps in the annual LAI cycle from systematic but sparse measurements using associated radiation and temperature indices. The ratio of the photosynthetically-active radiation reflectance to the shortwave reflectance is shown to have a particularly distinct LAI signature. Optical estimates of the fully-leafed LAI agreed well with measurements from autumn litterfall and showed moderate inter-annual variability for the trembling aspen overstory (mean ± S.D. of 2.44 ± 0.30) and the hazelnut understory (1.98 ± 0.44). Two features of the annual LAI cycle differed among years—the timing of leaf emergence in spring, which varied by up to four weeks, and the fully-leafed value for LAI, which varied between 3.66 and 5.22. The timing of leaf senescence in autumn was nearly constant among years. The seasonal cycles of F NEP and LAI were tightly coupled and the correspondence between their respective inter-annual differences was remarkable, particularly during leaf emergence in spring. Annual F NEP was positively correlated with the canopy duration and the annual maximum LAI, with increases in annual F NEP of 6.9 g C m −2 for each additional day in full leaf and 83 g C m −2 for each additional unit of LAI.

Environmental controls on ground cover species composition and productivity in a boreal black spruce forest.

Boreal black spruce forests typically have a dense ground cover of bryophytes. The two main bryophyte groups in boreal black spruce forests, feathermoss and Sphagnum, have ecophysiological characteristics that influence the biogeochemical cycles of black spruce forests differently. The objective of this study was to examine the environmental controls of ground cover composition and net primary production (NPP) of feathermoss and Sphagnum in a boreal black spruce forest in central Saskatchewan. The fraction of Sphagnum ground cover was positively correlated to canopy photosynthetically active radiation (PAR) transmittance (r 2=0.48, P=0.03), but the fraction of feathermoss ground cover was negatively correlated to canopy PAR transmittance in plots where Sphagnum was present (r 2=0.87, P<0.0001). Sphagnum presence was inversely correlated (P=0.0001) to water table index, defined as water table depth relative to the peat layer, while feathermoss occurred in a wider range of microenvironments. Average NPP for 1998 was more than three times greater for Sphagnum (77g C m-2 year-1) than feathermoss (24g C m-2 year-1), but the average bryophyte NPP for 1998 was 25g C m-2 year-1 because feathermoss was the dominant ground cover. The large, but differing, peat carbon content of Sphagnum- versus feathermoss-dominated boreal forests and peatlands necessitates the need to accurately quantify fraction ground cover. Additional validation of the empirical models between environmental variables and fraction ground cover of bryophytes is necessary, but the reported relationships offer an approach to model carbon dynamics of bryophytes in boreal forests and peatlands.

Soil respiration and photosynthetic uptake of carbon dioxide by ground-cover plants in four ages of jack pine forest

Soil carbon dioxide (CO2) emission (soil respiration), net CO2 exchange after photosynthetic uptake by ground-cover plants, and soil CO2 concentration versus depth below land surface were measured at four ages of jack pine (Pinus banksiana Lamb.) forest in central Saskatchewan. Soil respiration was smallest at a clear-cut site, largest in an 8-year-old stand, and decreased with stand age in 20-year-old and mature (60–75 years old) stands during May– September 1994 (12.1, 34.6, 31.5, and 24.9 mol C·m–2, respectively). Simulations of soil respiration at each stand based on continuously recorded soil temperature were within one standard deviation of measured flux for 48 of 52 measurement periods, but were 10%–30% less than linear interpolations of measured flux for the season. This was probably due to decreased soil respiration at night modeled by the temperature-flux relationships, but not documented by daytime chamber measurements. CO2 uptake by ground-cover plants ranged from 0 at the clear-cut site to 29, 25, and 9% of total growing season soil respiration at the 8-year, 20-year, and mature stands. CO2 concentrations were as great as 7150 ppmv in the upper 1 m of unsaturated zone and were proportional to measured soil respiration.

Environmental regulation of carbon dioxide exchange at the forest floor in a boreal black spruce ecosystem

Measurements of CO 2 exchange at the forest floor were made in shady dry areas dominated by feather mosses and open wet areas dominated by Sphagnum mosses within a 120-year-old black spruce forest in central Saskatchewan during 1996. Our objective was to study the environmental regulation of moss photosynthesis and forest floor (moss and soil) respiration, in order to calculate the contribution of moss photosynthesis to the carbon balance of the forest ecosystem. We used chamber gas exchange techniques to measure net carbon exchange at the forest floor during three periods that spanned the growing season. Measurements were also made with the clear chamber darkened, to obtain total respiration rates. Maximum measured rates of forest floor CO 2 efflux were approximately 7 μmol m −2 s −1 in both feather moss and Sphagnum areas. We developed and applied a two-term (shallow component and deep component) exponential model to describe the temperature dependence of forest floor respiration. We interpret the shallow stratum component as live moss respiration, and our field estimates of moss respiration were consistent with laboratory studies on isolated moss samples. The average (±S.D.) proportion of total respiration originating from the shallow stratum (at a uniform soil temperature of 10°C) was 7.0±15% in the feather moss community and 21±20% in the Sphagnum community. Gross photosynthesis was calculated as the difference between chamber measurements made in the light and dark. A rectangular hyperbole was fitted to the light response curves for moss gross photosynthesis. Sphagnum had higher maximum rates of gross photosynthesis than feather moss, and Sphagnum showed a pronounced seasonal change in photosynthetic capacity. The photosynthesis and respiration models were used, along with environmental data, to calculate the carbon balance for the forest floor. Our data indicated that the forest floor lost 255.4 g C m −2 during May–October. This net loss of carbon was the difference between moss gross photosynthesis of −140.7 g C m −2 and total forest floor respiration of 396.1 g C m −2 during May–October. Moss photosynthesis contributed approximately 13% of the total ecosystem gross production. We calculated moss net primary productivity to be 228 and 80 g C m −2 in Sphagnum and feather moss communities, respectively.

Soil respiration and photosynthetic uptake of carbon dioxide by ground-cover plants in four ages of jack pine forest

Soil carbon dioxide (CO2) emission (soil respiration), net CO2 exchange after photosynthetic uptake by ground-cover plants, and soil CO2 concentration versus depth below land surface were measured at four ages of jack pine (Pinus banksiana Lamb.) forest in central Saskatchewan. Soil respiration was smallest at a clear-cut site, largest in an 8-year-old stand, and decreased with stand age in 20-year-old and mature (60–75 years old) stands during May– September 1994 (12.1, 34.6, 31.5, and 24.9 mol C·m–2, respectively). Simulations of soil respiration at each stand based on continuously recorded soil temperature were within one standard deviation of measured flux for 48 of 52 measurement periods, but were 10%–30% less than linear interpolations of measured flux for the season. This was probably due to decreased soil respiration at night modeled by the temperature-flux relationships, but not documented by daytime chamber measurements. CO2 uptake by ground-cover plants ranged from 0 at the clear-cut site to 29, 25, and 9% of total growing season soil respiration at the 8-year, 20-year, and mature stands. CO2 concentrations were as great as 7150 ppmv in the upper 1 m of unsaturated zone and were proportional to measured soil respiration.

Isoprene emission inventory for the BOREAS southern study area.

An isoprene emission inventory for a section of boreal forest in central Saskatchewan was developed based on measured emission rates from the two dominant isoprene-emitting species, black spruce (Picea mariana (Mill.) BSP) and aspen (Populus tremuloides Michx.). The micrometeorological gradient technique was used to determine isoprene emission factors for establishing the inventory. Isoprene fluxes were measured during each of the three BOREAS intensive field campaigns (IFCs) during the 1994 growing season. Measured isoprene fluxes varied from 0.04 to 3.3 mg C m(-2) h(-1) over the black spruce canopy, and from 0.05 to 7.3 mg C m(-2) h(-1) above the aspen forest. Midsummer standard isoprene emission fluxes were 1.2 mg C m(-2) h(-1) and 2.3 mg C m(-2) h(-1) (at 20 degrees C and photosynthetically active radiation (PAR) of 1000 &mgr;mol m(-2) s(-1)) for black spruce and aspen, respectively. With light and temperature differences accounted for, there was an apparent seasonal effect on emissions with the highest rates in the summer months. The total amount of isoprene emitted from this section of the boreal forest was estimated to be 8.6 Gg C year(-1), which is about 1% of the net ecosystem carbon exchange for the study area. Aspen was the largest contributor, accounting for approximately 70% of the total. Branch enclosure and relaxed eddy accumulation measurements made at the black spruce site were used to define the uncertainty associated with flux measurements. Emission rates obtained by the gradient, enclosure and relaxed eddy accumulation methods showed good agreement when normalized to standard light and temperature conditions. The coefficient of variance between the three techniques was 12% for summer (IFC-2) measurements. The sensitivity of the annual isoprene emission total to the assignment of mean irradiance and temperature was also examined. If the hourly mean temperatures were increased by 1 degrees C throughout the growing season, annual carbon loss due to isoprene emission would increase by 14% from 8.6 to 9.8 Gg C.

Standing-dead tree component of the boreal forest in central Saskatchewan

The standing-dead tree component was assessed in part of the upland forests in the mixedwood boreal forest in central Saskatchewan. Comparisons of the average number of dead trees per hectare were made between softwood stands, softwood-dominant mixedwood stands, hardwood-dominant mixedwood stands and hardwood stands. General trends in snag size and density were evaluated by comparing similar stand types of various height classes. The majority of the snags within the four forest associations were of small diameter (2–10 cm), comprising from 0.6 to 18.6% of the stems in these stands with the number of small-diameter dead trees per hectare decreasing in the older, taller stands. The density of small-diameter snags ranged from 440 ha −1 in 5 m softwood stands to 55 ha −1 in 25 m hardwood stands. The density of large diameter snags (>21 cm dbh) rarely comprised more than 5% of a stand.

Effects of escaped settlement fires and logging on forest composition in the mixedwood boreal forest

The southern edge of the boreal forest in central Saskatchewan, Canada, has had its forest composition changed in the first decades of this century, primarily by logging and escaped fires from adjacent agricultural clearance. Three timber berths were established in 1884 within and immediately adjacent to the present southern half of Prince Albert National Park (established in 1927). These timber berths were selectively logged for saw timber between 1900 and 1918. Between 1907 and 1918, an average of 70 trees per hectare were removed by selective logging. Most of these trees were white spruce (Picea glauca (Moench) Voss). Since logging companies were required to remove all merchantable trees with a basal diameter greater than 25 cm, it is estimated that between 28 and 54% of the canopy trees were removed. Between 1883 and 1942, 81% of the timber berths were burned two or more times by crown fires that spread through the study area from adjacent agricultural clearances 30 km or more away. By 1945, agricultural clearance was largely complete and the clearance-caused fires stopped. The changes in tree composition were determined by transition probabilities between forest surveys taken in 1883 and 1994. Forests subjected to short-interval, clearance-caused fires but no logging were significantly reduced in their abundance of sexually reproducing trees such as white spruce, but increased in trees with either vegetative reproduction (i.e., underground stems, not just basal sprouts) or serotinous cones, such as aspen (Populus tremuloides Michx.) and jack pine (Pinus banksiana Lamb.), respectively. Transition probabilities for forests experiencing both short-interval, clearance-caused fires and logging reveal an even more marked compositional change in this direction.

An Aerial Census of Bald Eagles in Saskatchewan

An aerial census was conducted to determine the numbers and productivity, and to delineate distribution of bald eagles (Haliaeetus leucocephalus) in a 270,000-km2 area of northern Saskatchewan. Randomly located sample units were designed to contain uniform amounts of primary nesting habitat. An estimated 3,900 breeding areas, 6,900 adults, 4,700 immatures, and 2,500 nestlings were present in the summer of 1974. In southwestern regions 0.95 young per breeding area were produced, indicating reproduction above the estimated minimum required for maintenance. There was a positive correlation between breeding area density and April mean temperature. Two models for eagle distribution in the province are discussed. As a monitoring tool, the census technique could detect a population change of 27%. J. WILDL. MANAGE. 43(1):61-69 In 1969 Whitfield et al. (1974) censused the bald eagle population in approximately 20% of the boreal forest of central Saskatchewan and Manitoba. They estimated 460 to 697 breeding areas and a fall population of 1,600 to 8,000 eagles in the most densely inhabited part of their study area. Their results showed that these provinces are major inland bald eagle breeding grounds in North America. The study reported here was undertaken to estimate the size, reproductive success, and pattern of distribution of the bald eagle population in Saskatchewan in the summer of 1974, and to develop an aerial census technique suitable for monitoring the population. We are grateful to 3 agencies for financial support: Canadian Wildlife Service; Churchill River Study, Wildlife Sector (CRSWS); and Parks Canada. The CRSWS also made data available to us. We acknowledge the criticism and advice of R. W. Longley on meterological interpretations, E. Nordbrock on statistical procedures, and J. B. Gollop who reviewed the manuscript. MATERIALS AND METHODS Census Area and Sample Units The 270,000-km2 census area includes most of the boreal forest of Saskatchewan from approximately Lat. 54'N to the province's northern boundary at Lat. 60'N (Fig. 1). The area's southern boundary was chosen to eliminate from the census that portion of the province which we believed from previous work to have few breeding bald eagles (Whitfield et al. 1974). All of the census area except a strip of varying width along the southern edge is on the Precambrian Shield. The shield is covered with numerous lakes and ponds and its boundary with the more southerly sedimentary rock is marked by a series of large lakes which straddles the zone of contact. Relief is generally low and drainage is into Hudson Bay and the Arctic Ocean. The major physiographic regions are the Precambrian Shield, including the Athabasca Plains and Rock Knob Complex, and the Central Lowlands south of the shield (Richards and Fung 1969). J. Wildl. Manage. 43(1):1979 61 This content downloaded from 207.46.13.73 on Sat, 14 May 2016 06:08:52 UTC All use subject to http://about.jstor.org/terms 62 BALD EAGLES IN SASKATCHEWAN* Leighton et al.