Martin Dovčiak - Academia.edu (original) (raw)

Papers by Martin Dovčiak

New Forests, Mar 12, 2014

Forest regrowth is expected to gradually mitigate edge effects in forest landscapes fragmented by... more Forest regrowth is expected to gradually mitigate edge effects in forest landscapes fragmented by timber harvest, but our understanding of edge effect persistence and dynamics over time is still incomplete. Our main objective was to take a critical look at the role of forest regrowth in mitigating the initial edge effects on microclimate and understory vegetation in northern hardwood forests of the eastern United States. We compared canopy closure, hourly air temperature, soil moisture, and understory vegetation at increasing distances from forest edges (0, 5, 10, 20, and 30 m) along twelve transects placed across new and older forest edges (3-4 or 16-19 years old) created by forest harvest. Open, new forest edges exhibited pronounced edge effects on microclimate and shade-intolerant plants, but these were almost completely moderated by forest regrowth on the cleared side of older edges where dense young forest developed with a new canopy comparable in cover to adjacent mature forest. There were no initial edge effects on shade-tolerant vegetation across new forest edges, but the shade-tolerant vegetation declined in mature forest near old forest edges adjacent to dense young forest that supported only sparse understory vegetation. These delayed secondary edge effects of young dense forests on adjacent mature forests have not been previously documented and they should be more explicitly included in forest management considerations. We suggest an integrated system for managing and mitigating both the immediate primary and delayed secondary edge effects in those working forest landscapes where biodiversity conservation is of high priority.

Frontiers in forests and global change, Oct 17, 2019

Acid rain in eastern North America contributed to the widespread decline of red spruce in high-el... more Acid rain in eastern North America contributed to the widespread decline of red spruce in high-elevation spruce-fir forests. With recent reductions in acid deposition and a warming climate, resurgence of red spruce growth has been reported in some mountain areas. Based on an extensive tree-ring sampling network established across elevations (600 to 1,200 m above sea level) in spruce-fir forests on 10 mountains in the northeastern US (New York, Vermont, New Hampshire, and Maine), we investigated whether this resurgence was specific only to red spruce or if it occurred also in the co-dominant balsam fir. Furthermore, we tested if tree growth changes for both species were related to recent trends in acidic deposition and climate. Sharply increasing growth rates of red spruce were evident at all elevations and most closely correlated with increasing rainwater pH. Although climate of the previous year (cool July and warm November) explained higher spruce growth in certain years, recent trends in climate did not drive observed increases in spruce growth. In contrast, balsam fir exhibited no regional growth surge during the period of spruce recovery. Thus, spruce growth resurgence appears to be mediated primarily by declining acid deposition and not climatic changes or stand dynamics that would also impact fir growth. Although high-elevation forests may ultimately be at risk for future warming-related heat and drought stress, the observed recent dramatic resurgence of spruce growth illustrates the benefits of policy-driven reductions in acidic deposition for the health and productivity of northeastern US forests.

Ecosystems, Sep 18, 2017

Sugar maple, an abundant and highly valued tree species in eastern North America, has experienced... more Sugar maple, an abundant and highly valued tree species in eastern North America, has experienced decline from soil calcium (Ca) depletion by acidic deposition, while beech, which often coexists with sugar maple, has been afflicted with beech bark disease (BBD) over the same period. To investigate how variations in soil base saturation combine with effects of BBD in influencing stand composition and structure, measurements of soils, canopy, subcanopy, and seedlings were taken in 21 watersheds in the Adirondack region of NY (USA), where sugar maple and beech were the predominant canopy species and base saturation of the upper B horizon ranged from 4.4 to 67%. The base saturation value corresponding to the threshold for Al mobilization (16.8%) helped to define the species composition of canopy trees and seedlings. Canopy vigor and diameter at breast height (DBH) were positively correlated (P < 0.05) with base saturation for sugar maple, but unrelated for beech. However, beech occupied lower canopy positions than sugar maple, and as base saturation increased, the average canopy position of beech decreased relative to sugar maple (P < 0.10). In lowbase saturation soils, soil-Ca depletion and BBD may have created opportunities for gap-exploiting species such as red maple and black cherry, whereas in highbase saturation soils, sugar maple dominated the canopy. Where soils were beginning to recover from acidic deposition effects, sugar maple DBH and basal area increased progressively from 2000 to 2015, whereas for beech, average DBH did not change and basal area did not increase after 2010.

Ecological Monographs, Aug 1, 2005

Trees slowly colonize old fields on sandy outwash in the prairie-forest ecotone of the north-cent... more Trees slowly colonize old fields on sandy outwash in the prairie-forest ecotone of the north-central United States, and in the absence of fire, succession is expected to proceed toward oak woodland. We analyzed whether a case of unusually rapid and spatially extensive invasion by white pine (Pinus strobus) could be explained by the presence of specific temporal or spatial opportunity windows suitable for such invasion. We tested whether the invasion was temporally restricted to the period immediately after abandonment or to periods of favorable climate, and whether it was spatially restricted to areas of high seed rain or high forest-edge shade. White pine invasion into the field occurred in two waves separated from each other by a 1987-1989 drought period. The first wave (1980-1985) occurred during a period of average climate and led to the establishment of dense sapling patches in shade near forest edges. The second wave (1991-1994) occurred during a period of high precipitation and cooler than normal temperature, and resulted in colonization of the unshaded field center. In addition to the two temporal windows, white pine invasion occurred within two spatial windows: in areas highly sheltered by forest edge and in areas receiving high white pine seed rain. Overall these windows produced three different successional pathways: (1) a slow, creeping white pine invasion into highly shaded areas with low seed rain near forest edges; (2) a rapid, discrete-step invasion in areas where seed rain was abundant enough to overcome mortality in lower shade and where early arrivals facilitate filling in by later arrivals; and (3) a deferred invasion in the field center where low seed rain and lack of shade allowed the persistence of a grassland stage until favorable climate resulted in a white pine recruitment pulse. Temporal variation in climate can accelerate or decelerate any of the three successional pathways.

Forest Ecology and Management, Sep 1, 2017

Abstract Understanding long-term successional changes in old growth forests affected by stand-rep... more Abstract Understanding long-term successional changes in old growth forests affected by stand-replacing disturbance is particularly important in the context of contemporary changes in climate and disturbance regimes. We analyzed seven decades of succession following a stand-replacing wind disturbance (in 1947) in Badinsky prales, one of the best preserved old-growth fir-beech forests in western Carpathians (Central Europe), and contrasted the post-disturbance development with changes that occurred in the adjacent undisturbed old-growth forest. Both the disturbed and undisturbed sections of the old-growth forest showed compositional and structural changes that differed in their starting point, magnitude, and ecological mechanisms, but forest composition, structure and light conditions appeared to be converging across the two disturbance histories. The windthrow was initially dominated by early-successional goat willow ( Salix caprea L.) that declined in abundance, basal area, and growth over time as beech ( Fagus sylvatica L.) gradually increased in both abundance and basal area to dominate all canopy layers by 2015. This increase in beech dominance over time within the windthrow mirrored increasing beech dominance in the undisturbed old-growth forest which was caused by the gradual decline of silver fir ( Abies alba Mill.). The fact that old-growth forests originally co-dominated by fir and beech appear to be transitioning to forests dominated by beech regardless of the disturbance history suggests that beech expansion may be a robust process that should be considered in both old-growth conservation and forest management where timber harvest with low canopy retention may have similar effects on forest dynamics as a stand-replacing windthrow.

Ecological Applications, Dec 1, 2012

In many regions of the world, variable retention has replaced clear-cutlogging as the principal m... more In many regions of the world, variable retention has replaced clear-cutlogging as the principal method of regeneration harvest. Partial retention of the overstory is thought to ensure greater continuity of the species and ecological processes that characterize older forests. Level (amount) and spatial pattern of overstory retention are two basic elements of forest structure that can be manipulated to achieve specific ecological or silvicultural objectives. However, experiments that elucidate the relative importance of retention level and pattern (or their interaction) are rare. Here we assess long-term (.10 yr) responses of forest understories to experimental harvests of mature coniferous forests replicated at five sites in the Pacific Northwest (PNW). Treatments contrast both the level of retention (40% vs. 15% of original basal area) and its spatial distribution (dispersed vs. aggregated in 1-ha patches). For most vascular plant groups (early seral, forest generalist, and late seral), postharvest changes in cover and richness were reduced at higher levels of retention and in dispersed relative to aggregated treatments. Although retained forest patches were stable, changes in adjacent harvested (cleared) areas were significantly greater than in dispersed treatments. Late-seral herbs were highly sensitive to level and pattern of retention, with extirpations most frequent in the cleared areas of aggregated treatments and at low levels of dispersed retention. In contrast, early-seral species were most abundant in these environments. Forest-floor bryophytes exhibited large and persistent declines regardless of treatment, suggesting that threshold levels of disturbance or stress were exceeded. Our results indicate that 15% retention (the minimum standard on federal forestlands in the PNW) is insufficient to retain the abundance or diversity of species characteristic of late-seral forests. Although 1-ha aggregates provide refugia, they are susceptible to edge effects or stochastic processes; thus, smaller aggregates are unlikely to serve this function. The ability to achieve multiple ecological or silvicultural objectives with variable retention will require the spatial partitioning of habitats to include dispersed retention and larger undisturbed aggregates along with cleared areas.

Journal of Ecology, Apr 1, 2001

1 White pines (Pinus strobus) in a c. 1 ha near-boreal aspen-red maple stand in the western Great... more 1 White pines (Pinus strobus) in a c. 1 ha near-boreal aspen-red maple stand in the western Great Lakes region, USA, were allocated to five size-classes that were tested for discordance of their spatial patterns (i.e. within-size-class spatial distribution of individuals and spatial associations among different size-classes). The size-classes were 0.5-1 m tall, 1-2 m tall, 2-4 m tall, > 4 m tall but < 20 cm diameter at breast height (d.b.h.), and > 20 cm d.b.h. The size-classes also differed in age. Their spatial patterns were analysed using formulae for spatial autocorrelation with categorical data at neighbourhood (0-14 m) and stand (0-70 m) scales. 2 Size-classes clustered in neighbourhoods that differed in size ranging from 6 m in diameter (size-class 2) to 40 m (size-class 3), suggesting that the pattern of each sizeclass is due to a different set of environmental factors. Similar size-classes tended to be randomly or positively associated at neighbourhood scales, while the most dissimilar size-classes occupied different neighbourhoods. 3 Size-classes 1 and 2 were located farther away from seed trees than size-class 3, which was farther away than size-class 4. Thus periodic seedling invasion of a deciduous matrix may be followed by the gradual retraction of older size-classes into a refuge near the mature seed source where competition from shrubs and overstorey trees is lower. Although the lack of fine-scale clustering suggests density-dependent mortality within the refuge, few older individuals were found outside this area. 4 Two regeneration bottlenecks may structure white pine populations. First, recruitment into size-class 2 is restricted to small patches (possibly in understorey gaps) within neighbourhoods with abundant size-class 1. Relatively unrestricted recruitment to sizeclass 3 follows, and after that recruitment to size-class 4 is again limited, this time to refugia with sparse canopy near adult trees.

Plant Ecology, Mar 8, 2023

Wetlands, Jun 19, 2020

Large peatland complexes at the boreal-temperate ecotone are essential habitats for boreal specie... more Large peatland complexes at the boreal-temperate ecotone are essential habitats for boreal species at their southern range limits where they are threatened by tree encroachment accelerated by climate change and nitrogen deposition. To inform vascular plant and biodiversity conservation, we studied tree encroachment patterns in a large (> 400 ha) boreal peatland complex in the northeastern United States across vegetation types and environmental gradients. We characterized vascular plant composition, environmental drivers and tree demography on 50 plots (each 25 m 2). We used non-metric multidimensional scaling (NMS) to identify two main drivers of vascular plant composition in the herbaceous layer-pH and tree canopy openness-that described three broad plant community types (open bog, forested bog, and fen). Tree demography suggested that woody encroachment (i.e., tree seedling recruitment) varied across these community types; open bog was colonized by Picea mariana seedlings, while forested bog and fen (dominated by evergreen conifers, Picea mariana and Thuja occidentalis, respectively) were colonized by deciduous tree species (Acer rubrum and Betula alleghaniensis). Our findings provide early warning signs of vegetation change in boreal peatlands near their southern range limits caused by the encroachment of temperate tree species into forested peatlands and expanding tree cover in open bogs.

Environmental Pollution, Mar 1, 2018

Changes in climate and atmospheric nitrogen (N) deposition caused pronounced changes in soil cond... more Changes in climate and atmospheric nitrogen (N) deposition caused pronounced changes in soil conditions and habitat suitability for many plant species over the latter half of the previous century. Such changes are expected to continue in the future with anticipated further changing air temperature and precipitation that will likely influence the effects of N deposition. To investigate the potential long-term impacts of atmospheric N deposition on hardwood forest ecosystems in the eastern United States in the context of climate change, application of the coupled biogeochemical and vegetation community model VSDþPROPS was explored at three sites in New Hampshire, Virginia, and Tennessee. This represents the first application of VSDþPROPS to forest ecosystems in the United States. Climate change and elevated (above mid-19th century) N deposition were simulated to be important factors for determining habitat suitability. Although simulation results suggested that the suitability of these forests to support the continued presence of their characteristic understory plant species might decline by the year 2100, low data availability for building vegetation response models with PROPS resulted in uncertain results at the extremes of simulated N deposition. Future PROPS model development in the United States should focus on inclusion of additional foundational data or alternate candidate predictor variables to reduce these uncertainties.

Agricultural and Forest Meteorology, Nov 1, 2017

Mountains contain steep but constricted climate gradients that can provide climate warming refugi... more Mountains contain steep but constricted climate gradients that can provide climate warming refugia often overlooked in coarse-scale models of species migrations. With continued climate warming, the potentially important role of mountains in maintaining suitable climate for migrating species is still not clear. To determine if mountains in the northeastern U.S. can continue to serve as refugia for species in high-elevation spruce-fir forests under warming climate, we studied climate and climate-vegetation relations along elevational gradients across 76 sites on 11 mountains in four states of this region. We calculated (a) fine-scale temperature lapse rates using in situ climate loggers on each mountain, and (b) regional long-term temperature trends using 36 meteorological stations, in order to determine (c) recent and expected future shifts in species temperature envelopes along elevational gradients by linking lapse rates with regional temperature trends and climate warming scenarios for 2100 (+1, 3, and 5°C). Since 1960, temperature regimes have shifted upslope on average by 377 m and 133 m for the monthly mean of daily minimum (T min) and maximum (T max) temperatures, respectively, although climate did not warm equally for all months. By 2100, mid-range warming of 3°C may shift monthly temperature regimes upslope relative to their 1960s locations on average by 986 m for T min (580 m for 1°C, and 1393 m for 5°C scenario) and 588 m for T max (285 m for 1°C, and 891 m for 5°C scenario). We confirmed that spruce-fir forest distribution in the northeastern U.S. is strongly related to temperature, particularly October T max that has surprisingly differed from the overall warming trend as it cooled slightly since the 1960s and thus possibly contributed to the recent downslope shifts in some species ranges documented across the region in other studies. However, the vast majority of monthly temperature variables suggest considerable climate warming since the 1960s, and, given the expected future warming, the temperature regimes characteristic of the lower range margin of spruce-fir forests are unlikely to be present on many mountains in the region by 2100. Consequently, mountains in the northeastern U.S. may not provide long-term climate refugia for species dependent on the climate currently found in spruce-fir forests unless they can adapt to warmer temperatures.

Canadian Journal of Forest Research, Nov 1, 2006

We examined first-year responses of forest-floor bryophytes to structural retention harvests at f... more We examined first-year responses of forest-floor bryophytes to structural retention harvests at four locations in western Washington. Treatments represented a range of retention levels (100%, 75%, 40%, and 15% of original basal area) and spatial patterns (dispersed vs. aggregated in 1 ha patches). Declines in bryophyte cover and species' frequencies were comparably large at 40% and 15% retention. Retention pattern had little effect on the magnitude of decline, although declines in richness tended to be greater in aggregated treatments. Changes in cover were small within forest aggregates (comparable to controls). However, richness declined relative to controls within aggregates at 15% retention; rarer taxa in these exposed patches may be susceptible to edge effects. Declines in species' frequencies and richness were consistently greater in "clear-cut" areas of aggregated treatments than in dispersed retention; liverworts were particularly sensitive to harvest. In cut areas, bryophytes responded positively to cover of understory vegetation and negatively to logging slash. The positive correlation of richness (but not cover) to tree basal area may reflect the contribution of tree boles to persistence of rarer corticolous species. Our results suggest that conservation of bryophytes in forests managed with structural retention will require large retention patches and dispersed trees at levels considerably higher than current retention standards. Résumé : Nous avons étudié les réactions des bryophytes du parterre forestier pendant la première année suivant des coupes à rétention de structurale effectuées à quatre endroits dans l'ouest de l'État de Washington aux États-Unis. Les traitements couvraient une gamme de patrons de rétention (100 %, 75 %, 40 % et 15 % de la surface terrière initiale) et de patrons spatiaux (dispersés et agglomérés en blocs d'un hectare). La diminution du couvert de bryophytes et de la fréquence des espèces était importante et du même ordre de grandeur pour les traitements de rétention à 40 % et 15 %. Les patrons de rétention ont eu peu d'effet sur l'amplitude du déclin quoique la diminution de la richesse en espèces ait eu tendance à augmenter dans les traitements agglomérés. Les changements de couverture étaient faibles dans les agrégats de forêt et similaires aux témoins. Cependant, la richesse en espèces dans les traitements agglomérés à rétention de 15 % a diminué par rapport aux témoins; les taxons rares de ces blocs exposés sont peut-être susceptibles aux effets de bordure. Les diminutions de fréquence et de richesse en espèces dans les aires coupées à blanc des traitements agglomérés étaient généralement plus grandes que celles des traitements dispersés, les hépatiques étant particulièrement sensibles à la coupe. Dans les aires coupées, les bryophytes ont réagi positivement au couvert de la végétation du sous-bois et négativement à celui des débris de coupe. Une corrélation positive entre la richesse (mais pas la couverture) et la surface terrière peut refléter la contribution du tronc des arbres à la persistance d'espèces corticoles plus rares. Nos résultats indiquent que la conservation des bryophytes dans les forêts aménagées avec une rétention structurale exigera de grands îlots de rétention et des arbres dispersés à des niveaux considérablement plus élevés que les normes actuelles de rétention. [Traduit par la Rédaction] Doviak et al. 3052

Global Change Biology, Dec 28, 2016

Climate change is expected to lead to upslope shifts in tree species distributions, but the evide... more Climate change is expected to lead to upslope shifts in tree species distributions, but the evidence is mixed partly due to land-use effects and individualistic species responses to climate. We examined how individual tree species demography varies along elevational climatic gradients across four states in the northeastern United States to determine whether species elevational distributions and their potential upslope (or downslope) shifts were controlled by climate, land-use legacies (past logging), or soils. We characterized tree demography, microclimate, land-use legacies, and soils at 83 sites stratified by elevation (~500 to~1200 m above sea level) across 12 mountains containing the transition from northern hardwood to spruce-fir forests. We modeled elevational distributions of tree species saplings and adults using logistic regression to test whether sapling distributions suggest ongoing species range expansion upslope (or contraction downslope) relative to adults, and we used linear mixed models to determine the extent to which climate, land use, and soil variables explain these distributions. Tree demography varied with elevation by species, suggesting a potential upslope shift only for American beech, downslope shifts for red spruce (more so in cool regions) and sugar maple, and no change with elevation for balsam fir. While soils had relatively minor effects, climate was the dominant predictor for most species and more so for saplings than adults of red spruce, sugar maple, yellow birch, cordate birch, and striped maple. On the other hand, logging legacies were positively associated with American beech, sugar maple, and yellow birch, and negatively with red spruce and balsam firgenerally more so for adults than saplings. All species exhibited individualistic rather than synchronous demographic responses to climate and land use, and the return of red spruce to lower elevations where past logging originally benefited northern hardwood species indicates that land use may mask species range shifts caused by changing climate.

Philosophical Transactions of the Royal Society B, Nov 5, 2012

As the climate warms, boreal tree species are expected to be gradually replaced by temperate spec... more As the climate warms, boreal tree species are expected to be gradually replaced by temperate species within the southern boreal forest. Warming will be accompanied by changes in above-and belowground consumers: large moose (Alces alces) replaced by smaller deer (Odocoileus virginianus) above-ground, and small detritivores replaced by larger exotic earthworms below-ground. These shifts may induce a cascade of ecological impacts across trophic levels that could alter the boreal to temperate forest transition. Deer are more likely to browse saplings of temperate tree species, and European earthworms favour seedlings of boreal tree species more than temperate species, potentially hindering the ability of temperate tree species to expand northwards. We hypothesize that warminginduced changes in consumers will lead to novel plant communities by changing the filter on plant species success, and that above-and below-ground cascades of trophic interactions will allow boreal tree species to persist during early phases of warming, leading to an abrupt change at a later time. The synthesis of evidence suggests that consumers can modify the climate change-induced transition of ecosystems.

Canadian Journal of Forest Research, Oct 1, 2003

We tested the effects of seed rain, safe sites, soil depth, overstory, and shrub layer on the est... more We tested the effects of seed rain, safe sites, soil depth, overstory, and shrub layer on the establishment and recruitment of white pine (Pinus strobus L.) in aspen mixedwoods of the western Great Lakes region, U.S.A. Germinant and seedling densities were positively related to seed rain and safe site characteristics that indicate moist conditions: high overstory basal area, decaying wood, and moss cover. Germinant and seedling densities were highest under dense overstory (>16 m 2 /ha) and were unrelated to shrub cover. Sapling recruitment was greatest under low overstory density (<16 m 2 /ha) and low shrub cover (<55%). On shallow soil (~14 cm), germinants and seedlings commonly occurred on soil depths <5 cm, but large saplings almost always occurred on soil depths >5 cm. On deeper soil (~21 cm), overstory white pines occupied the shallowest soils (~18 cm) of all major overstory species, indicating that competition may cause white pine recruitment into the canopy to be lower on deeper soils. White pine populations in the study were initially spatially structured by seed rain and safe sites but sapling growth and recruitment was structured by overstory density, shrub cover, and soil depth. Résumé : Nous avons testé les effets de la dispersion aérienne des graines, des refuges, de l'épaisseur du sol, de l'étage dominant et de la strate arbustive sur l'établissement et le recrutement du pin blanc (Pinus strobus L.) dans une forêt mixte de peuplier de l'ouest de la région des Grands Lacs, aux États-Unis. La densité des germinats et des semis était positivement reliée à la dispersion aérienne des graines et aux caractéristiques des refuges indicatrices de conditions humides : surface terrière élevée de l'étage dominant, bois en décomposition et tapis de mousses. La densité des germinats et des semis était la plus forte sous un étage dominant dense (>16 m 2 /ha) et n'était pas influencée par le couvert d'arbustes. Le recrutement de gaules était le plus élevé sous un étage dominant de faible densité (<16 m 2 /ha) et un faible couvert d'arbustes (<55 %). Sur sol mince (~14 cm), les germinats et les semis se trouvaient le plus souvent sur des sols de moins de 5 cm d'épaisseur mais les gaules de forte dimension se trouvaient presque toujours sur des sols de plus de 5 cm d'épaisseur. Sur les sols plus profonds (~21 cm), les pins blancs de l'étage dominant occupaient les sols les plus minces (~18 cm) comparativement à toutes les principales espèces de l'étage dominant, indiquant que la compétition peut être responsable du plus faible recrutement du pin blanc dans le couvert sur les sols plus profonds. Dans cette étude, la dispersion aérienne des graines et les refuges déterminaient initialement la structure spatiale des populations de pin blanc mais le recrutement et la croissance des gaules étaient déterminés par la densité de l'étage dominant, le couvert d'arbustes et la profondeur du sol.

Background/Question/Methods Overstory trees moderate understory microclimate through direct and i... more Background/Question/Methods Overstory trees moderate understory microclimate through direct and indirect effects of shading. Canopy shading reduces exposure to solar radiation, extremes in temperature, and changes in substrate quality, factors that may be critical to the persistence of forest-dependent species such as bryophytes (mosses and liverworts). We examined effects of increasing levels of forest canopy removal on understory microclimate and bryophyte community structure in an overstory retention experiment in mature coniferous forests of the Cascade Mountains in western Washington. We sampled understory microclimate (solar radiation and air temperature) and bryophyte abundance and diversity in three harvest treatments representing progressively lower levels of retention (100, 40, and 15% of original basal area) in each of three experimental blocks, 7-8 years after treatment. We tested (a) whether changes in bryophyte cover and richness were correlated with level of retention...

Forest Ecology and Management, Jul 1, 2022

2015 AGU Fall Meeting, Dec 15, 2015