Daniel M. Kashian

Carbon Storage on Landscapes with Stand-replacing Fires

Abstract Many conifer forests experience stand-replacing wildfires, and these fires and subsequent recovery can change the amount of carbon released to the atmosphere because conifer forests contain large carbon stores. Stand-replacing fires switch ecosystems to being a net source of carbon as decomposition exceeds photosynthesis—a short-term effect (years to decades) that may be important over the next century if fire frequency increases. Over the long term (many centuries), net carbon storage through a fire cycle is zero if stands replace themselves. Therefore, equilibrium response of landscape carbon storage to changes in fire frequency will depend on how stand age distribution changes, on the carbon storage of different stand ages, and on postfire regeneration. In a case study of Yellowstone National Park, equilibrium values of landscape carbon storage were resistant to large changes in fire frequency because these forests regenerate quickly, the current fire interval is very long, the most rapid changes in carbon storage occur in the first century, and carbon storage is similar for stands of different ages. The conversion of forest to meadow or to sparser forest can have a large impact on landscape carbon storage, and this process is likely to be important for many conifer forests.

VARIABILITY AND CONVERGENCE IN STAND STRUCTURAL DEVELOPMENT ON A FIRE‐DOMINATED SUBALPINE LANDSCAPE

The 1988 Yellowstone fires resulted in a complex mosaic within which post- fire lodgepole pine seedling densities varied by over five orders of magnitude. Investigators have speculated that such postfire mosaics of vegetation structure may persist until the next large disturbance, but the fate of the initial structural variability of postfire communities is currently poorly understood. We studied lodgepole pine (Pinus contorta var. latifolia Englem. ex Wats.) stands in Yellowstone National Park (Wyoming, USA) unburned by the 1988 fires to determine how variation in stand structure changes with increasing stand age. The coefficient of variation in stand density decreased from 231% in 12-yr-old stands to 91% in stands aged 50-100 yr, and to 37% for stands ages 200-250 yr. Substantial variability in age distributions both within and among age classes suggested that both gradual infilling of initially sparse stands and self-thinning of initially dense stands are important processes affecting variation in stand density. Variation in stand density was explained primarily by stand age (P < 0.0001) and by geographic location (P < 0.01). Field estimates and re- constructions of stand density trajectories suggest the importance of biotic processes and the contingent effects that produce initial patterns of stand density. Variation in stand density is substantially reduced 125 yr following fire and remains relatively unchanged beyond approximately 200 yr. These results suggest that large, infrequent fires impose a pattern of stand structural variability that may persist for centuries, but stand density likely converges within the fire-free interval in this landscape.

Postfire changes in forest carbon storage over a 300-year chronosequence of Pinus contorta-dominated forests

A warming climate may increase the frequency and severity of stand-replacing wildfires, reducing carbon (C) storage in forest ecosystems. Understanding the variability of postfire C cycling on heterogeneous landscapes is critical for predicting changes in C storage with more frequent disturbance. We measured C pools and fluxes for 77 lodgepole pine (Pinus contorta Dougl. ex Loud var. latifolia Engelm.) stands in and around Yellowstone National Park (YNP) along a 300-year chronosequence to examine how quickly forest C pools recover after a stand-replacing fire, their variability through time across a complex landscape, and the role of stand structure in this variability. Carbon accumulation after fire was rapid relative to the historical mean fire interval of 150–300 years, recovering nearly 80% of prefire C in 50 years and 90% within 100 years. Net ecosystem carbon balance (NECB) declined monotonically, from 160 g C·m−2·yr−1 at age 12 to 5 g C·m−2·yr−1 at age 250, but was never negative after disturbance....

Ecological species groups of landform-level ecosystems dominated by jack pine in northern Lower Michigan, USA

A combination of field and tabular methods and multivariate analyses were used to develop groups of ground flora species (i.e., ecological species groups) that characterize and distinguish highly disturbed, landform-level ecosystems dominated by jack pine in northern Lower Michigan. The endangered Kirtlands warbler formerly or currently occupied the large glacial landforms for which species groups were developed. Eight such ecological species groups were created using 31 woody and herbaceous species sampled in 144 plots within a 20,000 km2 geographic region of uniform climate and regional physiography. The groups were initially constructed using subjective, observation-based groupings of species with similar presence and abundance along soil moisture and fertility gradients. Species groups were corroborated using TWINSPAN and detrended correspondence analysis, and the environmental conditions indicated by each were described and contrasted based upon field observations and canonical correspondence analysis. Two of the eight species groups indicated very dry, infertile sites, and one was indicative of a very broad range of sites dominated by jack pine. The remaining five groups reflected a relatively gentle environmental gradient within the set of ecosystems we sampled, indicating small differences along a soil moisture gradient and less so along a soil fertility and light availability gradient. The groups were applied successfully for the majority of an area that had been repeatedly logged and/or burned for at least 120 years. In addition, the groups were successful when tested on sites with highly disturbed upper soil strata furrowed for the establishment of plantations between the 1960s and 1980s. Within the boundaries of the regional ecosystems for which they were developed, ecological species groups reflect the integrated effects of multiple site factors that control the height growth rates of jack pine trees that, in turn, determine the duration of Kirtlands warbler occupancy. While usually applied at the scale of ecosystem types, our results demonstrate that ecological species groups may also provide the ecological basis for distinguishing ecosystems at broader scales. When examined simultaneously in the field with physiography, microclimate, and soil factors, the groups are therefore useful in identifying and classifying ecosystem units at the scale of landforms, the appropriate scale of management for the Kirtlands warbler.

Reconciling divergent interpretations of quaking aspen decline on the northern Colorado Front Range.

Ecologists have debated over the past 65 years whether quaking aspen (Populus tremuloides Michx.) has or has not declined in abundance, vigor, or regeneration in western North America. Many studies have provided divergent interpretations of the condition of aspen forests, leading to difficulty in translating this ecological information into management recommendations. To reconcile these contrasting conclusions and to test the hypothesis that multiple types of aspen decline and persistence occur simultaneously on heterogeneous landscapes, we assessed 91 aspen stands across the northern Colorado Front Range to determine the range of ecological conditions that underlie aspen decline or persistence. Approximately 15% of aspen forest area in our sample exhibited dieback of mature stems coupled with a lack of young trees indicative of declining stands, most often at lower elevations where elk browsing is heavy and chronic, and where effects of fire exclusion have been most significant. However, 52% of the area sampled had multiple cohorts indicative of self-replacing or persistent stands. Conifer dominance was increasing in over 33% of all aspen forest area sampled, most often at high elevations among lodgepole pine (Pinus contorta var. latifolia Englem. ex Wats.) forests. Reconstructions of relative basal area and density of aspen and lodgepole pine in these stands suggest cyclical dominance of these species, where conifers gradually replace aspen over long fire intervals, and aspen vigorously re-establish following stand-replacing fires. The diversity of ecological contexts across the northern Colorado Front Range creates a variety of aspen dynamics leading to decline or persistence, and no single trend describes the general condition of aspen forests in appropriate detail for managers. Active management may be useful in preserving individual stands at fine scales, but management prescriptions should reflect specific drivers of decline in these stands.

Recent distribution of coyotes across an urban landscape in southeastern Michigan

Human–wildlife interactions in urban areas are widely reported by ecologists to be the result of human encroachment on wildlife habitat. Highly mobile species, however, have been documented by both wildlife biologists and casual observers to occupy areas heavily populated by humans. Range expansion and population growth of coyotes (Canis latrans )h as led to their increased presence in metropolitan Detroit, Michigan, where poor economic conditions over the last several decades have resulted in the reversion of numerous recreational areas and abandoned parcels to more wooded or vegetated conditions that have provided potential wildlife habitat. We performed an extensive survey for coyote evidence (i.e., carcasses, den sites, scats, sightings, or tracks) across metropolitan Detroit to examine distribution across both the general region and specific land cover types. We found 58% of all coyote evidence on unpaved trails, paths, and unimproved roads within edge habitats (e.g., grassland adjacent to urban non-vegetative land cover), with den sites and tracks the only types of evidence found strictly in interior habitats. Land cover around evidence points included more wooded land cover than expected in suburban areas, suggesting the importance of tree cover for coyote occupancy, and more open space and wooded land cover than expected in urban areas, highlighting the coyotes’ avoidance of heavily populated areas. We speculate that habitat characterized by tree cover has likely never been limiting within metropolitan Detroit, and that reoccupation of southeastern Michigan by coyotes is more likely a consequence of expanding coyote populations outside of suburban and urban areas rather than newly available habitat resulting from land cover change.

An Ecoregional Context for Forest Management on National Wildlife Refuges of the Upper Midwest, USA

To facilitate forest planning and management on National Wildlife Refuges, we synthesized multiple data sources to describe land ownership patterns, land cover, landscape pattern, and changes in forest composition for four ecoregions and their associated refuges of the Upper Midwest. We related observed patterns to ecological processes important for forest conservation and restoration, with specific attention to refuge patterns of importance for forest landbirds of conservation priority. The large amount of public land within the ecoregions (31–80%) suggests that opportunities exist for coarse and meso-scale approaches to conserving and restoring ecological processes affecting the refuges, particularly historical fire regimes. Forests dominate both ecoregions and refuges, but refuge forest patches are generally larger and more aggregated than in associated ecoregions. Broadleaf taxa have increased in dominance in the ecoregions and displaced fire-dependent taxa such as pine (Pinus spp.) and other coniferous species; these changes in forest composition have likely also affected refuge forests. Despite compositional changes, larger forest patches on refuges suggests that they may provide better habitat for area-sensitive forest landbirds of mature, compositionally diverse forests than surrounding lands if management continues to promote increased patch size. We reason that although fine-scale research and monitoring for species of conservation priority is important, broad scale (ecoregional) assessments provide crucial context for effective forest and wildlife management in protected areas.

A neutral modeling approach for designing spatially heterogeneous jack pine plantations in northern Lower Michigan, USA

ContextJack pine-dominated ecosystems in northern Lower Michigan are heavily managed using a harvesting and planting regime designed to provide breeding habitat for the federally endangered Kirtland’s warbler. These plantations do not resemble naturally-regenerated patterns of jack pine, but few data exist after which alternate planting configurations may be modeled.ObjectivesOur objective was to use quantitative analyses to construct new planting configurations that better mimic the spatial patterns of natural post-fire regeneration.MethodsWe used high-resolution color imagery of a 2000 wildfire to map jack pine saplings and the point density function in ArcMap to quantify the spatial heterogeneity that follows large wildfires in this region. Based on metrics calculated from this analysis of landscape pattern, we used a neutral modeling approach to develop prototypical planting configurations.ResultsJack pine regeneration in the burned area occurred as a series of high-density patches within a matrix of moderate- to low-density regeneration. In contrast, the planted areas were dominated by a single, high-density class with large patch sizes and little heterogeneity. We were able to construct neutral models that were not significantly different from the actual landscape using the metrics we calculated.ConclusionsThough highly successful for Kirtland’s warbler habitat, current jack pine plantations in northern Lower Michigan do not emulate natural post-fire patterns. Quantifying the spatial pattern of regeneration following wildfires may inform neutral landscape models, which will be important tools for managers as they attempt to better emulate natural patterns within plantation design.

Upland Sandpiper: A Flagship for Jack Pine Barrens Restoration in the Upper Midwest?

Fire-dependent ecosystems have been altered across much of North America, and their restoration has the potential to affect many wildlife species, including those of regional conservation priority such as the upland sandpiper (UPSA, Bartramia longicauda). In the Upper Midwest, fire-dependent jack pine (Pinus banksiana) barrens were once common and are now a focus of restoration by state, federal, and non-government agencies and organizations. Given UPSA’s association with terrestrial ecosystems such as pastures, hayfields, and barrens, we determined the location of UPSA-occupied areas across multiple states, with special focus on Michigan, to illustrate distributional relationships with specific ecoregions, soils, and land covers while considering what role the species may have as a flagship for barrens restoration. With the exception of Michigan, UPSA-occupied areas in all states studied had greater proportions of agricultural land (National Land Cover Data: pasture/hay and cultivated crops) than other openland cover types. In Michigan, 66% of long-term occupied areas were found in the northern Lower Peninsula, and most often consisted of anthropogenic grasslands providing stable habitat on higher-quality soils. In contrast, short-term occupied areas had a greater proportion of native openlands that were often located on poorer, xeric soils associated with jack pine ecosystems that succeed to closed-canopy forests or shrublands in the absence of fire. Openlands with no UPSA breeding evidence were characterized by intensive agriculture (row crops). Our data suggest that UPSA would be an appropriate flagship species for the restoration of jack pine barrens, as well as the conservation of anthropogenic grasslands.

Variation in Fractal Symmetry of Annual Growth in Aspen as an Indicator of Developmental Stability in Trees

Fractal symmetry is symmetry across scale. If one looks at a branch of a tree its branching pattern is reminiscent of the tree as a whole. Plants exhibit a number of different symmetries, including bilateral, rotational, translational, and fractal; deviations from each of these types has been associated with organisms developing in stressful environments. Here, we explore the utilization and meaning of fractal analysis on annual growth ring production in woody plants. Early detection of stress in plants is difficult and the compounding effects of multiple or severe stressors can lead to irreversible damage or death. Annual wood production was used to produce a time series for individuals from stands classified as either high vigor or low vigor (a general measure of health). As a measure of symmetry over time, the fractal dimension of each time series was determined and compared among vigor classes. We found that individuals obtained from low vigor sites had a significantly lower fractal dimension than those from high vigor sites. These results agree with patterns found in a variety of other organisms, and we argue that the reduced fractal dimension is related to a loss in system complexity of stressed individuals.