Young Jack Pine Research Articles

Low Kirtland’s Warbler fledgling survival in Wisconsin plantations relative to Michigan plantations

Abstract The Kirtland’s Warbler (Setophaga kirtlandii) is a formerly endangered habitat specialist that breeds mainly in young jack pine (Pinus banksiana) forests in northern Lower Michigan, USA. The species is conservation-reliant and depends on habitat management. Management actions have primarily focused on creating jack pine plantations, but the species also breeds in red pine (Pinus resinosa) plantations in central Wisconsin, USA. However, the plantations were not intended as breeding habitat and have suboptimal pine densities. While nesting success is similar between low-density red pine plantations and optimal jack pine habitat, it is not clear if low-density red pine plantations support high fledging survival. If high-quality nesting and post-fledging habitat are not synonymous, fledgling survival and breeding population recruitment may be low. We characterized survival, habitat use, and movement patterns of dependent Kirtland’s Warbler fledglings in Wisconsin red pine plantations and compared fledgling survival between Wisconsin and Michigan. Mayfield cumulative survival estimates at 30 days post-fledging were 0.20 for Wisconsin fledglings and 0.43–0.78 for Michigan fledglings. Logistic exposure cumulative survival estimates for Wisconsin fledglings were 0.23–0.34 at 30 days post-fledging. Fledglings in Wisconsin used areas where vegetation cover and density of red and jack pine were high relative to available areas but not at greater proportions than what was available. Our findings demonstrate that red pine plantations with low pine densities were not equally suitable as nesting and post-fledging habitat, as fledgling survival rates were low. We hypothesize that reduced habitat structure, and not particular pine species, likely contributed to reduced fledgling survival in Wisconsin. Thus, we recommend including red pine as a component in managed Kirtland’s Warbler habitat only if tree densities approach optimal levels.

Spatially Explicit Kirtland’s Warbler Habitat Management Scheduling in Michigan’s Upper Peninsula

A spatially explicit management strategy is presented for Kirtland’s Warbler (Setophaga kirtlandii) habitat on the Hiawatha National Forest in Michigan’s Upper Peninsula. The Hiawatha National Forest has a goal of continuously providing large patches of dense young jack pine for Kirtland’s warbler breeding habitat. The problem is challenging as patches of suitable habitat are relatively short lived, forcing large shifts in the location of large patches in the future. In this study, alternative management strategies for providing habitat are described, explicitly mapped, and compared on a 70,600 ha landscape in the context of implementing many desired conditions of the forest’s land management plan. Strategies are developed by using two interacting scheduling models. Comparisons address overall habitat levels, habitat spatial arrangement through time, and financial trade-offs. The financial cost of managing habitat is high and there are further financial trade-offs associated with aggregating habitat into large patches. Furthermore, the marginal cost of habitat increases as more habitat is added to the management system. Managers may use information about the added costs of spatially explicit habitat management to help evaluate the added benefits to the species. It is often expensive to establish wildlife habitat and desirable ecological conditions, but results show that there are potential benefits from using detailed computer-aided management scheduling tools to support the decision-making process.

A probabilistic risk assessment for the Kirtland's warbler potentially exposed to chlorpyrifos and malathion during the breeding season and migration.

Two organophosphate pesticides, chlorpyrifos and malathion, are currently undergoing reregistration in the United States and were recently used by the US Environmental Protection Agency (USEPA) as case studies to develop a national procedure for evaluating risks to endangered species. One of the endangered bird species considered by the USEPA was the Kirtland's warbler (Setophaga kirtlandii). The Kirtland's warbler is an endangered migratory species that nests exclusively in young jack pine stands in Michigan and Wisconsin, and winters in the Bahamas. We developed probabilistic models to assess the risks of chlorpyrifos and malathion to Kirtland's warblers during the breeding season and the spring and fall migrations. The breeding area model simulates acute and chronic exposure and risk to each of 10 000 birds over a 60-d period following initial pesticide application. The model is highly species specific with regard to the foraging behavior of Kirtland's warblers during the breeding season. We simulated the maximum application rate and number of applications allowed on the labels for representative use patterns that could be found within 3 km of the breeding areas of Kirtland's warbler. The migration model simulates 10 000 birds during the course of their 12- to 23-d migration between their breeding area and the Bahamas. The model takes advantage of more than a century of observations of when, where, and for how long Kirtland's warblers forage in different habitats during the course of their migration. The data indicate that warblers only infrequently stop over in habitats that could be treated with chlorpyrifos and malathion. The breeding area and migration models resulted in predictions of very low acute and chronic risk for both pesticides to Kirtland's warblers. These results were expected, given that field observations indicate that the Kirtland's warbler has dramatically increased in abundance in recent decades. Integr Environ Assess Manag 2018;14:252-269. © 2017 SETAC.

Replacement of wildfire by whole-tree harvesting increases nitrification and nitrate movement in jack pine forest soils

Forest types that were once naturally maintained by stand-replacing wildfires are typically managed with clearcut harvesting; however, we know relatively little about how well clearcutting mimics the effects of stand-replacing wildfire on the availability and cycling of nitrogen (N) in forest soils. We compared net N mineralization, nitrification and NO3− movement in soils from young (2–9 y) jack pine (Pinus banksiana) stands that had been regenerated by either stand-replacing wildfire or clearcut harvesting. We located four pairs of burned and harvested stands that were otherwise similar in age, soil type and geographic location. Net N mineralization, measured both in situ and in the laboratory, was nearly 2 times higher in young stands of clearcut origin compared to stands of wildfire origin. Differences between disturbance types were much more pronounced for net nitrification, which was more than 20 times greater, on average, in clearcut-origin sites. Burned sites rarely exhibited any net nitrification in field incubations, and at nearly 2/3 of the sampling times burned sites exhibited net immobilization of NO3−. This lack of nitrification occurred despite the fact that we always observed net N mineralization across all of our in-situ incubations in wildfire-origin stands. Finally, we observed nearly four times greater NO3− movement through the soil profile in clearcut stands, as evidenced by capture on ion-exchange resins at a depth of 25cm. Together, these results clearly indicate that replacement of wildfire disturbance by clearcut harvesting promotes nitrification and NO3− movement in jack pine ecosystems of northern Lower Michigan. The exact mechanism underlying this response in our sites remains uncertain; however, it appears that some factor that restricts net nitrification in young stands of wildfire origin is not present in clearcut-origin stands. Our finding of increased nitrification and NO3− movement in the years following clearcutting could lead to increased losses of N and base cations, and could also favor plant species with greater preference for NO3− as a N source.

Influence of residual forest patches on post-fire bird diversity patterns in jack pine-dominated ecosystems of northern Lower Michigan

Stand-replacing fires are part of the natural disturbance regime that maintain jack pine (Pinus banksiana Lamb.) forests of northern Lower Michigan. Currently, the occurrence and extent of wildfire is much reduced relative to the past and young jack pine plantations specifically managed for Kirtland’s warbler (Setophaga kirtlandii Baird) are a prominent feature on the landscape. Stringers, or patches of residual pre-fire forest, are a unique feature left behind after wildfires which are not often accounted for in plantation management. In this study, we examined the ecological value of stringers from an avian biodiversity perspective by comparing bird assemblages found within stringers to those in the surrounding forest (non-stringers). Our objective was to answer two research questions: (1) do stringers have unique bird communities relative to the surrounding vegetation (forest or plantation)?; and (2) how much of the variation in bird communities can be explained by differences in vegetation structure and composition between stringers and non-stringers? We conducted breeding and non-breeding season point counts and used abundance data to compare bird species found within stringers and non-stringers at seven sites grouped by time since disturbance. Species richness was significantly higher (P=0.01) in the stringers when the non-stringers were 30–40years old, with 32 species discovered in the stringers and 29 species in the non-stringers. During the breeding season, bird assemblages differed between stringers and non-stringers when the non-stringers were <12years old (multi-response permutation procedures; T=−10.11, A=0.07, P=<0.00), but no differences were observed when non-stringers were 30–40years old or >40years old. Non-breeding bird communities differed between stringers and non-stringers only when the non-stringer was a recently planted (<5years old) plantation (T=−2.15, A=0.09, P=0.02). Differences in bird assemblages appear to be driven by the vegetation structure of stringers and non-stringers where fires were recent, but increasing similarity in vegetation structure occurs with time since fire; over time the importance of stringers for avian biodiversity is reduced. Our results suggest that stringers are important for bird communities, especially in recently disturbed areas, and that these biological legacies should be considered where jack pine management attempts to emulate natural patterns and processes.

Kirtland's Warbler (Setophaga kirtlandii)

Spring travelers from around the world are attracted to the young jack pine forests of Michigan for a chance to hear the loud distinct song of the endangered Kirtland's Warbler. This blue-gray-backed warbler with a yellow underside can be heard singing from its perch in the tops of standing snags or jack pine trees, or seen hopping from tree to tree or to the ground, pumping its tail while searching for insects and blueberries.

Young jack pine and high severity fire combine to create potentially expansive areas of understocked forest

Jack pine is a fire adapted species considered to regenerate well after fires of all severities. The Richardson Fire was an extreme megafire event that burned 576,000ha of jack pine dominated boreal forest in 2011 in northern Alberta, Canada. Initial scouting immediately after the fire identified a great deal of variability in jack pine regeneration seemingly related to fire severity and pre-fire stand composition. We sampled tree regeneration in 56 pure jack pine stands across the range of fire severity and pre-fire stand ages 1year post-fire. We found that jack pine regeneration density was greater in older stands (>60years old) compared to younger stands (<30years old) and in moderate severity burns compared to high severity burns. In young stands with high severity burns, jack pine regeneration averaged only 1164 seedlings per hectare which is well below current stand densities indicating a potentially understocked future forest. At the landscape level, we extrapolated fire severity to the entire fire area using pre and post-fire satellite imagery and found that the area of young jack pine stands which had a high severity burn, and therefore likely low seedling regeneration, was greater than 130,000ha with most of this area occurring in patches greater than 500ha in size. Overall, our results suggest that young jack pine may not be as resilient to high severity fires as previously thought and that a large area of burned boreal forest may be at risk of conversion from a closed canopy forest to a more open canopy woodland ecosystem given the predicted changes in fire regime.

Potential of L-Band Radar for Retrieval of Canopy and Subcanopy Parameters of Boreal Forests

In this paper, we study the radar retrieval of soil moisture as well as canopy parameters in a range of boreal forests. The retrieval is formulated as an optimization problem where the difference between data and prediction of a forward scattering model is minimized. The forward model is a discrete scatterer radar model, and the optimization algorithm is a global optimization scheme known as simulated annealing. The inversion method is first applied to synthetic data assuming hypothetical allometric relationships to make the retrieval possible by reducing the number of unknown vegetation parameters. The inversion algorithm is then validated using the data acquired with the National Aeronautics and Space Administration (NASA)/Jet Propulsion Laboratory (JPL) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in June 2010 in central Canada boreal forests in support of the prelaunch calibration and validation activities of NASA's Soil Moisture Active and Passive (SMAP) mission. The inversion results for synthetic data show that the absolute retrieval error in soil moisture and relative retrieval error in canopy height are small, while the relative output error in trunk density could be large. The inversion results for actual field data show a great accuracy in soil moisture retrieval for Old Jack Pine and Young Jack Pine forests but show large retrieval errors for many of the radar pixels in the Old Black Spruce site. This paper shows that L-band radar is capable of retrieving surface soil moisture in forests with a high biomass where the forest structure allows soil moisture information to be carried by scattering mechanisms.

Energy balance closure at the BERMS flux towers in relation to the water balance of the White Gull Creek watershed 1999–2009

The eddy-covariance method has become a cornerstone in the study of the surface energy and water balances, yet the oft-reported lack of energy-balance closure adds uncertainty to its measurements of evapotranspiration. This study explores the issue of closure based on 10 years of energy and water balance measurements at seven flux-tower sites in the southern boreal forests of western Canada. The sites include mature aspen, black spruce and jack pine forests, three young jack pine forests following harvesting, and one fen. Careful attention was paid to the measurement of evapotranspiration E, surface available energy (net radiation minus storage), precipitation P, and soil water storage S including root-zone soil water and water table elevation. Stand-level outflow O at the flux-tower sites was estimated annually as a residual term in the vertical water balance (O=P−E−ΔS), with and without energy-closure adjustments to E. Six of the flux towers were located within or near the gauged White Gull Creek watershed (603km2). The comparison of measured streamflow from the White Gull Creek with estimated outflow, scaled from the flux towers to the watershed, provides an independent test of the need for energy-closure adjustments to flux-tower E.Measured streamflow from the White Gull Creek watershed had a long-term mean (S.D.) of 101 (54)mmy−1 but was highly variable among years, ranging from 30mmy−1 during an extreme dry year to 204mmy−1 during an extreme wet year. Stand-level outflow, estimated with an energy-closure adjustment to E, varied by land-cover type, from a mean (S.D.) of 30 (35)mmy−1 at the mature aspen forest and 52 (125)mmy−1 at the fen to 108 (85)mmy−1 at the mature black spruce forest and 187 (55) and 250 (64)mmy−1 at the mature and young (harvested) jack pine forests, respectively. The dominant land-cover type, mature black spruce forest, typified the hydrology of the boreal forest landscape, with outflow similar to the watershed mean.The warm-season, eddy-covariance sensible and latent heat fluxes were 15±4% (annual mean±S.D.) smaller than surface available energy, with reasonable similarity among sites and years. When scaled from stand to watershed, the tower-based estimates of outflow agreed with measured streamflow only when outflow was calculated with an energy-closure adjustment to E. The annual means for the 2002–2009 hydrologic years were: 131mmy−1 (measured streamflow); 182mmy−1 (tower-based outflow calculated without energy-closure adjustments to E); and 112 and 127mmy−1 (tower-based outflow calculated with energy-closure adjustments to E from two different schemes). This result corroborates the need for energy-closure adjustments to eddy-covariance measurements of E, but it does not provide guidance about how the adjustments should be implemented.

Replacement of wildfire by whole-tree harvesting in jack pine forests: Effects on soil fertility and tree nutrition

Large areas of northern coniferous forests once naturally maintained by stand-replacing wildfires have shifted to an anthropogenic disturbance regime of clearcut harvesting followed by natural or artificial regeneration, with unknown consequences for soil biogeochemical processes. We used a comparative approach to investigate the effects of whole-tree harvesting (WTH) vs. stand-replacing wildfire (WF) on soil C and nutrient availability, and nutrition and growth of the succeeding stand, in jack pine ( Pinus banksiana) forests of northern Lower Michigan. We compared total carbon (C), total nitrogen (N), potential N mineralization, and extractable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) among stands regenerated via WTH or WF in two age classes (4–7 years and 12–18 years). We also measured jack pine foliar nutrition and height growth in these same stands, as well as estimating the contribution of legacy dead wood to ecosystem nutrient capital in young stands. We found some evidence in support of our hypothesis that WTH would leave behind greater pools of soil C and N, but lower pools of P and base cations. However, the differences we observed were confined entirely to surface organic horizons, with the two disturbance regimes indistinguishable when viewed cumulatively to our maximum sampling depth of 30 cm. Estimates of nutrient pools in legacy wood inherited by young jack pine stands were also small in comparison to total soil pools (ranging from 1 to 9% depending on the element), suggesting that decomposition and nutrient release from this material is not likely to result in noticeable differences in soil fertility later in stand development. Similar levels of soil nutrients between WTH- and WF-origin stands were reflected in our measures of jack pine foliar nutrition and height growth, which were both unaffected by mode of stand origin. Results from this study suggest that soil nutrient levels following WTH fall within the natural range of variation produced by WF in these jack pine forests; however, comparison with a similar study on boreal jack pine suggests that latitudinal effects on O-horizon nutrient capital may influence the degree to which WTH matches the effects of WF on soil nutrient availability.

Ecological forestry at National Wildlife Refuges: Experiences from Seney National Wildlife Refuge and Kirtland’s Warbler Wildlife Management Area, USA

Although land management over much of the history of the U.S. Fish and Wildlife Service’s National Wildlife Refuge System (NWRS) has emphasized single-species management, recent policy has encouraged land managers to focus on broader ecosystem restoration goals. One framework for forest ecosystem management that is becoming more popular in the NWRS and other federal and state resource agencies has been termed “ecological forestry”—an approach to forest ecosystem management where the focus is on incorporating an understanding of the outcomes of natural disturbances and stand development processes into designing silvicultural practices. This approach stresses understanding the effects of natural disturbances on biological legacies, structural and compositional heterogeneity, and the recovery periods between disturbance events (including how this recovery period influences stand complexity). Recently, resource managers and ecologists from Seney National Wildlife Refuge, The Ohio State University, and Central Michigan University have partnered to examine how these guiding principles can be integrated into NWRS forest ecosystem management. Specifically, we are partnering to develop management strategies to help: 1) restore the once extensive mixed-pine forest ecosystems of eastern Upper Michigan; 2) mitigate the effects of the beech-bark disease complex on American beech (Fagus grandifolia Ehrh.), a foundation species in northern hardwood forests of eastern North America; and 3) promote more natural forest patterns for wildlife species of young jack pine (Pinus banksiana Lamb.) forest ecosystems, including the federally endangered Kirtland’s warbler (Dendroica kirtlandii). These efforts are ongoing and will continue to be monitored over time. However, initial collaborations suggest that the NWRS provides an excellent crucible to study the application of ecological forestry principles and develop novel ways to manage forest ecosystems. Key words: ecological forestry, forest restoration, Kirtland’s warbler, National Wildlife Refuge, U.S. Fish and Wildlife Service

Long-Term Wet and Dry Deposition of Total and Methyl Mercury in the Remote Boreal Ecoregion of Canada

Although a positive relationship between atmospheric loadings of inorganic mercury (Hg(II)) to watersheds and concentrations of methyl mercury (MeHg) in fish has now been established, net wet and dry deposition of Hg(II) and MeHg to watersheds remains challenging to quantify. In this study, concentrations and loadings of total mercury (THg; all forms of Hg in a sample) and MeHg in open area wet deposition, throughfall, and litterfall were quantified atthe remote Experimental Lakes Area in the boreal ecoregion, NW Ontario, Canada. Between 1992 and 2006, mean annual THg and MeHg loadings in the open were 36 +/- 17 and 0.5 +/- 0.2 mg ha(-1), respectively. Throughfall THg and MeHg loadings were generally 2-4 times and 0.8-2 times higher, respectively, than loadings in the open. Loadings of both THg and MeHg were highest under an old growth spruce/fir canopy and lowest under a deciduous maple canopy, whereas loadings under young jack pine and wetland spruce/pine/alder canopies were intermediate. Litterfall generally represented the largest input of THg (86-105 mg ha(-1)) and MeHg (0.7-0.8 mg ha(-1)) to the landscape on an annual basis. Using the "direct" method of estimating dry deposition (thoughfall + litterfall - open loadings), we calculated that annual dry deposition of THg and MeHg under forest canopies ranged from 105 to 201 mg ha(-1), whereas dry deposition of MeHg ranged from 0.7 to 1.2 mg ha(-1). Photoreduction and emission of wet-deposited Hg(ll) from canopy foliage were accounted for, resulting in 3-5% (5-6 mg ha(-1)) higher annual estimates of dry deposition than via the direct method alone. NetTHg and MeHg loadings to this remote landscape were lower than at any other previously studied forested site globally. This study shows that THg and MeHg loading can be extremely variable within a heterogeneous boreal landscape and that processes such as Hg photoreduction and emission from foliage should be considered when estimating dry deposition of Hg.

Comparison of height growth and growth intercept models of jack pine plantations and natural stands in northern Ontario

Accurate estimates of forest productivity are required for sustainable forest management. Sixty-five jack pine (Pinus banksiana Lamb.) plantations (&lt;50 years of age) were sampled to develop height growth and variable growth intercept (GI) models for jack pine plantations in northern Ontario, Canada. Based on the residual plots and model-fitting statistics, these models can be recommended for estimating site index (SI) of young (&lt;40 years) jack pine plantations. To compare SI of plantations with that of natural stands, we used stem-analysis data from 383 plots of natural jack pine stands (aged 50–157 years) from the same geographic region to develop the GI models for natural stands. Also, polymorphic SI curves were developed for young (&lt;40 years) plantations in northern Ontario. These SI curves were different from those for natural stands. Jack pine plantations had a higher site quality (SI) than did the original natural stands on the similar sites. The SI curves developed from natural stands should not be used to predict growth and yield of jack pine plantations before they are calibrated for jack pine plantations. These GI models will be used to estimate SI for silviculture and forest-management planning.

Carbon fluxes in a young, naturally regenerating jack pine ecosystem

Within the FLUXNET network of tower stations for performing long‐term measurements of CO2 exchange between forest ecosystems and the atmosphere, most research has focused on mature forests that are strong carbon sinks. Nevertheless, it is just as valuable to quantify fluxes from recently disturbed forests so that we can recognize and predict the impact of disturbance on carbon fluxes. We measured carbon fluxes and microclimatic variables within a naturally regenerating, young (12–14 years of age) jack pine ecosystem in northern Michigan. During the months June to October of 2001–2003, this ecosystem exhibited a low net uptake of approximately 17.8–18.3 g C m−2 5 months−1. Soil respiration was independently measured and then modeled on the basis of soil temperature and soil moisture. Model estimates of soil respiration were 627, 583, and 681 g C m−2 5 months−1 from June to October in 2001, 2002, and 2003, respectively. Net ecosystem exchange (NEE) and soil respiration were inversely correlated in midsummer (r = −0.6, p = 0.001) during the period of lowest NEE (greatest uptake) and highest soil respiration rates. In the spring, NEE and soil respiration were positively correlated (r = 0.4, p = 0.01). During the fall, when soil temperatures remained fairly steady and air temperatures fluctuated, this coefficient between NEE and soil respiration declined to an average −0.25 (p = 0.2). Our results indicate that 12–14 years following disturbance this ecosystem displays a small net uptake during the June to October months but respiratory losses during the snow season (mid‐October to April) could possibly counterbalance this carbon gain.

Effect of Soil Water Content on Carbon Dioxide Flux at a Sparse-Canopy Forest in the Canadian Boreal Ecosystem

The relationship between soil moisture and ecosystem-level carbon budget was investigated for a BERMS (Boreal Ecosystem Research and Monitoring Sites) site in Saskatchewan, Canada, using eddy covariance flux measurements obtained during 2001 and 2002. The site was located in a young jack pine stand (Pinus banksiana Lamb.) characterized by a sparse low canopy. The site was harvested in 1994 and young trees from ages one year to ten years were regenerating naturally. Total ecosystem respiration (Rec) at the site was sensitive to volumetric soil water content (VWC), and increased exponentially with VWC and soil temperature in warm seasons. Under daytime light-saturated conditions, gross primary production (GPP) had a positive linear correlation with VWC, with enhancement occurring under high soil temperatures. In contrast to GPP and Rec individually, net ecosystem CO2 exchange (NEE) was less sensitive to VWC. Under VWC > 0.03, the VWC-dependence was hardly detectable for NEE, irrespective of temperature range.

Retrieval of the canopy leaf area index in the BOREAS flux tower sites using linear spectral mixture analysis

This paper reports on the use of linear spectral mixture analysis for the retrieval of canopy leaf area index (LAI) in three flux tower sites in the Boreal Ecosystem-Atmosphere Study (BOREAS) southern study area: Old Black Spruce, Old Jack Pine, and Young Jack Pine (SOBS, SOJP, and SYJP). The data used were obtained by the Compact Airborne Spectrographic Imager (CASI) with a spatial resolution of 2 m in the winter of 1994. The convex geometry method was used to select the endmembers: sunlit crown, sunlit snow, and shadow. Along transects for these flux tower sites, the fraction of sunlit snow was found to have a higher correlation with the field-measured canopy LAI than the fraction of sunlit crown or the fraction of shadow. An empirical equation was obtained to describe the relation between canopy LAI and the fraction of sunlit snow. There is a strong correlation between the estimated LAI and the field-measured LAI along transects (with R 2 values of 0.54, 0.71, and 0.60 obtained for the SOBS, SYJP, and SOJP sites, respectively). The estimated LAI for the whole tower site is consistent with that obtained by the inversion of a canopy model in our previous study where values of 0.94, 0.92, and 0.63 were obtained for R 2 for the SOBS, SYJP and SOJP sites, respectively. The CASI 2-m summer data over the SOBS site was also employed to investigate the possibility of deriving canopy LAI from the summer data using linear mixture analysis. At a spatial resolution of 10 m, the correlation between the field-measured LAI and the estimated LAI along transects is small at R 2 less than 0.3, while R 2 increases to 0.6 at a spatial resolution of 30 m. The difficulty in canopy LAI retrieval from the summer data at a spatial resolution of 10 m is likely due to the variation of the understory reflectance across the scene, although spatial misregistration of the CASI data used may also be a possible contributing factor.

Population increase in Kirtland's warbler and summer range expansion to Wisconsin and Michigan's Upper Peninsula, USA

The threatened Kirtland's warbler Dendroica kirtlandii breeds in stands of young jack pine Pinus banksiana growing on well-drained soils in Michigan, USA. We summarize information documenting the range expansion of Kirtland's warbler due to increased habitat management in the core breeding range in the Lower Peninsula of Michigan during 1990–2000. We collected records and conducted searches for the species in Michigan's Upper Peninsula and Wisconsin over 1978–2000. During that time 25 males were found in Wisconsin and 90 males in the Upper Peninsula. We documented colonization of Michigan's Upper Peninsula by six ringed males from the Lower Peninsula of Michigan. Four ringed birds also moved back to the core breeding range, including two males that made two-way movements between the core breeding range and the Upper Peninsula. Thirty-seven females were observed with males from 1995 to 2000, all in Michigan. Nesting activities were noted for 25 pairs and at least nine nests fledged young. One male ringed as a fledgling returned to breed in two subsequent years. After a 19-year period of population stability, the Kirtland's warbler population increased four-fold during 1990–2000, most likely in response to a tripling in habitat area. This increase in sightings and documented breeding may be related to habitat availability in Michigan's Upper Peninsula and to saturation of habitat in the main breeding range. The increase in extra-limital records during 1995–1999 corresponds to the time when the population went from the minimum to the maximum projected population densities, and a decline in natural wildfire habitat was just offset by new managed habitat for the Kirtland's warbler.

Modelling evapotranspiration at three boreal forest stands using the CLASS: tests of parameterizations for canopy conductance and soil evaporation

AbstractThe performance of the Canadian Land Surface Scheme (CLASS) was evaluated in off‐line runs, using data collected at three boreal forest stands located near Thompson, Manitoba: young jack pine, mature jack pine, and mature black spruce. The data were collected in the late spring through autumn of 1994 and 1996, as part of the Boreal Ecosystem–Atmosphere Study (BOREAS).The diurnal range in modelled soil heat flux was exaggerated at all sites. Soil evaporation was modelled poorly at the jack pine stands, with overestimation common and a step change to low evaporation as the soil dried. Replacing the soil evaporation algorithm, which was based on the estimation of a surface relative humidity value, with one based on soil moisture in the top soil layer reduced the overestimation and eliminated the step changes. Modelled water movement between soil layers was too slow at the jack pine stands. Modifying the soil hydraulic parameters to match an observed characteristic curve at the young jack pine stand produced a soil water suction that agreed more closely with measurements and improved drainage between soil layers.The latent heat flux was overestimated and the sensible heat flux underestimated at all three stands. New Jarvis–Stewart‐type canopy conductance algorithms were developed from stomatal conductance measurements. At the jack pine stands, stomatal conductance scaled by leaf area index reproduced canopy conductance, but a reduction in the scaled stomatal conductance by one half was necessary at the black spruce stand, indicating a nonlinearity in the scaling of stomatal conductance for this ecosystem. The root‐mean‐squared error for daily average latent heat flux for the control run of the CLASS and for the best test run are 49 W m−2 and 14 W m−2 respectively at the young jack pine stand, 50 W m−2 and 15 W m−2 respectively at the old jack pine stand, and 48 W m−2 and 13 W m−2 respectively at the old black spruce stand. Copyright © 2003 Royal Meteorological Society

Landscape Ecosystems of the Mack Lake Burn, Northern Lower Michigan, and the Occurrence of the Kirtland's Warbler

Abstract The Kirtland's warbler (Dendroica kirtlandii Baird) is a federally endangered songbird that nests only in ecosystems dominated by young jack pine (Pinus banksiana Lamb.) in northern Michigan. Although considerable research has focused on the bird, comparatively little information is available on the specific landscape ecosystems occupied by the warbler. The 9,700 ha Mack Lake burn provided an opportunity to track the pattern of Kirtland's warbler occurrence in relation to the ecosystems of a highly diverse and productive area of its breeding range. Using a multifactor landscape ecosystem approach, two high-elevation and four low-elevation landform-level ecosystems were identified, described, and mapped. The spatial pattern of warbler occurrence over time was strongly mediated by the physical and biotic components of the ecosystems. During the first 3 yr of warbler occupation (1986–1988), the high-elevation landforms, characterized by relatively warm temperatures, moister, more fertile soils, and faster growing jack pines, supported 62% of the population. Thereafter, a major shift occurred to the low-elevation landforms. During the last 3 yr of record (1995–1997), the low-elevation landforms, characterized by colder temperatures, drier, less fertile soils, and slow-growing jack pines, supported 86% of the population. The juxtaposition of high- and low-elevation landforms, and the fine-scale ecosystem diversity within them, prolonged the duration of warbler occupancy beyond what would be expected in less heterogeneous conditions. As demonstrated here, the landscape ecosystem approach provides a sound, ecological framework for understanding patterns of Kirtland's warbler occurrence and for assisting managers in identifying appropriate management areas for the continued recovery of the species. FOR. SCI. 49(1):119–139.

Landscape Ecosystems of Northern Lower Michigan and the Occurrence and Management of the Kirtland's Warbler

Abstract The Kirtland's warbler (Dendroica kirtlandii Baird) is an endangered songbird that nests in northern Lower Michigan in ecosystems dominated by young jack pine (Pinus banksiana Lamb.). An ecological, multifactor approach was used to determine the range and characteristics of landform-level ecosystems supporting the warbler and to compare the spatial and temporal patterns of warbler occupation among these ecosystems. Using an ecosystem rather than a strictly biological approach, the landforms occupied by the warbler are very diverse. Twelve landforms were identified based on 61 sites currently or formerly occupied by the warbler. Average annual jack pine height growth, an indicator of stand structural features that influences initial warbler colonization and duration of occupancy, differed significantly among landforms, resulting in marked differences in warbler occurrence in time and space across the breeding range. Landforms with favorable growing conditions for jack pine were colonized earliest and were occupied for the shortest duration, whereas landforms with unfavorable growing conditions were colonized relatively late but were occupied longest. Different ecological factors, such as the spatial position of landforms, microclimate, soil texture, or a combination of these factors, may account for favorable or unfavorable growing conditions for jack pine, which in turn affects the timing and duration of warbler occupancy. The classification and description of ecosystems occupied by the warbler provides an ecological framework for warbler management, especially when plantations rather than wildfire are the primary source of warbler habitat. FOR. SCI. 49(1):140–159.