Upper Peninsula Of Michigan Research Articles

Postglacial colonization in the Great Lakes Region by the white-footed mouse (Peromyscus leucopus): conflicts between genomic and field data

Abstract For regions that were covered by ice during the Pleistocene glaciations, species must have emigrated from unglaciated regions. However, it can be difficult to discern when and from what ancestral source populations such expansions took place, especially since warming climates introduce the possibility of very recent expansions. For example, in the Great Lakes region, pronounced climatic change includes past glaciations as well as recent, rapid warming. Here we evaluate different expansion hypotheses with a genomic study of the white-footed mouse (Peromyscus leucopus noveboracensis), which is one of the most common mammals throughout the Great Lakes region. Ecological surveys coupled with historical museum records suggest a recent range expansion of P. leucopus associated with the warming climate over the last decades. These detailed records have yet to be complemented by genomic data that provide the requisite resolution for detecting recent expansion, although some mitochondrial DNA (mtDNA) sequences have suggested possible hypotheses about the geography of expansion. With more than 7,000 loci generated using RADseq, we evaluate support for multiple hypotheses of a geographic expansion in the Upper Peninsula of Michigan (UP). Analysis of a single random single-nucleotide polymorphism per locus revealed a fine-scale population structure separating the Lower Peninsula (LP) population from all other populations in the UP. We also detected a genetic structure that reflects an evolutionary history of postglacial colonization from two different origins into the UP, one coming from the LP and one coming from the west. Instead of supporting a climate-driven range expansion, as suggested by field surveys, our results support more ancient postglacial colonization of the UP from two different ancestral sources. With these results, we offer new insights about P. leucopus geographic expansion history, as well as a more general phylogeographic framework for testing range shifts in the Great Lakes region.

Mink (Neovison vison) fecal microbiomes are influenced by sex, temperature, and time postdefecation

Abstract Gut microbiomes encode myriad metabolic functions critical to mammalian ecology and evolution. While fresh fecal samples provide an efficient, noninvasive method of sampling gut microbiomes, collecting fresh feces from elusive species is logistically challenging. Nonfresh feces, however, may not accurately represent the gut microbiome of the host due to succession of gut microbial consortia postdefecation as well as colonization by microbes from the surrounding environment. Using American mink (Neovison vison) as a model species, we examined postdefecation microbial community succession to learn how ambient temperature and temporal sampling constraints influence the reliability of nonfresh feces to represent host gut microbiomes. To achieve our goal, we analyzed fresh mink feces (n = 5 females; n = 5 males) collected at the time of defecation from captive mink at a farm in the Upper Peninsula of Michigan and we subsequently subsampled each fecal specimen to investigate microbial community succession over five days, under both warm (21°C) and cold (–17°C to –1°C) temperature treatments. We found that both temperature and time influenced fecal microbiome composition; and we also detected significant sexual dimorphism in microbial community structures, with female mink microbiomes exhibiting significantly greater variation than males’ when exposed to the warm temperature treatment. Our results demonstrate that feces from unknown individuals can be a powerful tool for examining carnivore gut microbiomes, though rigorous study design is required because sex, ambient temperature, and time since defecation drive significant microbial variation and the sample size requirements necessary for detecting statistically significant differences between target populations is an important consideration for future ecologically meaningful research.

FOOT INJURIES IN MICHIGAN, USA, GRAY WOLVES (CANIS LUPUS), 1992-2014.

The range of gray wolves (Canis lupus) in the contiguous US is expanding. Research and monitoring to support population recovery and management often involves capture via foothold traps. A population-level epidemiologic assessment of the effect of trap injuries on wolf survival remains needed to inform management. We describe the baseline rate, type, and severity of foot injuries of wolves born 1992-2013 in Michigan's Upper Peninsula, evaluate the reliability of field-scoring trap-related injuries, and the effect of injuries on wolf survival. We assessed foot injuries by physical and radiographic exam at postmortem and/or time of capture for 351 wolves using the International Organization for Standardization 10990-5 standard and the effects of injuries, sex, age, previous capture and body condition on survival using proportional hazards regression. We used ordinal regression to evaluate epidemiologic associations between sex, age, previous capture, body condition, cause of death and injury severity. Most wolves (53%) experienced no physically or radiographically discernable foot injuries over their lifetimes. Among those wolves that did experience injuries, 33% scored as mild. Foot injuries had little epidemiologically discernable effect on survival rates. Wolves with higher foot trauma scores did experience an increased risk of dying, but the magnitude of the increase was modest. Most limb injuries occurred below the carpus or tarsus, and scoring upper-limb injuries added little predictive information to population-level epidemiologic measures of survival and injury severity. There was little association between injury severity and cause of death. Based on necropsy exams, previous trap injuries likely contributed to death in only four wolves (1.1%). Our results suggest that injuries resulting from foothold traps are unlikely to be a limiting factor in recovery and ongoing survival of the Michigan gray wolf population.

RT-ddPCR Wastewater Monitoring of COVID-19 Across the Eastern Upper Peninsula of Michigan

RT-ddPCR Wastewater Monitoring of COVID-19 Across the Eastern Upper Peninsula of Michigan

Examining Access to Psychiatric Care in Michigan's Upper Peninsula.

There is a shortage of mental health services in rural America, and little research is focused on rural underserved communities. Our aim was to identify and map clinical mental health services located in the Upper Peninsula of Michigan (UP) and explore primary care physician (PCP) mental health service provision and barriers to access experienced by this population. We mapped clinically active psychiatrists and inpatient psychiatric units in the UP, and identified high-risk regions based on >30 mile distance to ambulatory services or low inpatient bed to population ratio. We surveyed PCPs in identified high-risk areas regarding provision of mental health services, comfort with providing services, and perceived barriers to care. Half of UP counties had no psychiatrists, and only two counties had inpatient psychiatric beds. PCPs are attempting to fill gaps in care, and report comfort with treating depression and anxiety, but less comfort with treating with bipolar disorder and substance use. Nearly all PCPs report barriers to accessing mental health resources; 70% report no psychiatrists to whom they can readily refer. Michigan's UP has a shortage of mental health resources. Proposed strategies to confront this shortage include additional training of PCPs for substance use and bipolar disorder, bolstering the mental health workforce, and improving access to consultative services.

Sugar maple (Acer saccharum) Seedling Bank Response to Storm Disturbance and Single Tree Selection Harvest in the Southern Keweenaw Peninsula, Michigan

This case study seeks to fill a critical knowledge gap regarding how natural wind disturbance affects stand and seedling bank diversity in mixed northern hardwood forests managed by single tree selection harvest methods. Contemporary timber harvests on state managed lands in Michigan's Upper Peninsula employ single tree selection cutting methods to promote more complex age structure in second growth stands dominated by sugar maple (Acer saccharum). However, concern exists that single tree selection harvest may result in lowered compositional diversity of seedlings as the low light conditions of small dispersed gaps exclude less shade tolerant species from gap regeneration. In July 2016 severe thunderstorms with winds in excess of 145 km/h (90 mph) caused extensive tree fall and canopy gap creation in second growth mixed northern hardwood forests in the southern Keweenaw Peninsula. We measured the species composition of overstory tree mortality and understory seedling regeneration in 14 storm gaps created in stands with and without previous single tree selection harvest. Storm gaps ranged in size from 125 to 1100 m2. American basswood (Tilia americana) was disproportionately wind-thrown. Robust seedling regeneration was released in all storm gaps, with sugar maple comprising more than 75% of mean seedling abundance, regardless of previous single tree selection harvest. Sugar maple and ironwood (Ostrya virginiana) comprised 80% of sapling abundance. Results indicate single tree selection of mixed northern hardwood stands does not exacerbate, but rather emulates, dense sugar maple regeneration found on unmanaged second growth sites.

Spatial patterning of regeneration failure in experimental canopy gaps 15–24 years post-harvest

Gap-based silviculture and legacy-tree retention are strategies that can increase structural and resource heterogeneity while maintaining forest productivity at the stand scale. Nevertheless, areas of delayed regeneration have been noted in openings with some persisting for a decade or more. To better understand the causes of localized recruitment delay and/or near-term failure, we examined spatial patterning of persistent (≥15 years) patches of regeneration failure (≤1 sapling ≥1.37 m tall per 10 m2) at two long-term experimental gap experiments in northern Wisconsin and the Upper Peninsula of Michigan. During the summers of 2018 and 2019, we surveyed 84 harvest-created canopy gaps for areas of failure and mapped 79 individual patches where regeneration had failed to establish and recruit in a total of 52 openings. Spatial attributes of these individual patches were summarized and compared to their location relative to expected within (e.g., north versus south, distance from edge) and between gap (e.g., gap size) gradients in light resource availability. Spatial analyses revealed no significant trends between north and south regions of gaps, which suggests that regeneration failure at the gap scale is likely determined by factors disentangled from expected within-gap light resource gradients. At the site without legacy-tree retention, patches that had failed to regenerate trees occupied 17.3% of the total area in gaps (≥10 m radius) and were located near gap center. In contrast, at the site with legacy trees, only 4.8% of the total area in gaps (≥11 m radius) was occupied by patches of regeneration failure and patches were located near gap edge. Furthermore, increasing gap size was associated with a higher risk of regeneration failure only at the study site without legacy-tree retention. Our results suggest that legacy-tree retention may moderate the spatial extent of regeneration failure, however, further work is needed to clarify their long-term influence on regeneration dynamics within harvest openings.

Six Decades of Growth and Yield and Financial Return in a Silviculture Experiment in Northern Hardwoods

AbstractThe Cutting Methods Study at the Ford Forest in the Upper Peninsula of Michigan, USA, was established in 1956 and has been maintained continuously on a 10-year cycle. Methods consist of three diameter limits (DL; 13, 30, and 41 cm), single-tree selection to three residual basal area limits (STS; 11, 16, and 21 m2ha−1), and light improvement (LI) focused on improving tree grade. Long-term results show that the 41 cm DL produced the greatest managed forest value and cumulative sawlog production, followed by the STS to 11 m2ha−1 residual basal area. STS treatments and LI were uniformly superior at improving standing tree grade. In contrast, treatments that emphasize removal of large diameter trees while retaining moderate residual basal area (the 41 cm DL and 11 m2ha−1 STS) produced the largest harvest volumes of high-grade sawlogs, driving financial performance. Stand density has declined in all treatments except the 30 and 41 cm DL, where it has increased, and these two treatments have larger abundance of saplings and poles. Alternative partial cutting methods such as selection to lower residual basal areas and medium-intensity diameter-limit cuts thus may provide greater financial returns and higher average quality, and could have implications on regeneration and long-term sustainability.

Limitations of the Q10 Coefficient for Quantifying Temperature Sensitivity of Anaerobic Organic Matter Decomposition: A Modeling Based Assessment

AbstractThe Q10 coefficient is the ratio of reaction rates at two temperatures 10°C apart, and has been widely applied to quantify the temperature sensitivity of organic matter decomposition. However, biogeochemists and ecologists have long recognized that a constant Q10 coefficient does not describe the temperature sensitivity of organic matter decomposition accurately. To examine the consequences of the constant Q10 assumption, we built a biogeochemical reaction model to simulate anaerobic organic matter decomposition in peatlands in the Upper Peninsula of Michigan, USA, and compared the simulation results to the predictions with Q10 coefficients. By accounting for the reactions of extracellular enzymes, mesophilic fermenting and methanogenic microbes, and their temperature responses, the biogeochemical reaction model reproduces the observations of previous laboratory incubation experiments, including the temporal variations in the concentrations of dissolved organic carbon, acetate, dihydrogen, carbon dioxide, and methane, and confirms that fermentation limits the progress of anaerobic organic matter decomposition. The modeling results illustrate the oversimplification inherent in the constant Q10 assumption and how the assumption undermines the kinetic prediction of anaerobic organic matter decomposition. In particular, the model predicts that between 5°C and 30°C, the decomposition rate increases almost linearly with increasing temperature, which stands in sharp contrast to the exponential relationship given by the Q10 coefficient. As a result, the constant Q10 approach tends to underestimate the rates of organic matter decomposition within the temperature ranges where Q10 values are determined, and overestimate the rates outside the temperature ranges. The results also show how biogeochemical reaction modeling, combined with laboratory experiments, can help uncover the temperature sensitivity of organic matter decomposition arising from underlying catalytic mechanisms.

Conservation Detection Dogs Increase Efficacy for Prey Detection at Carnivore GPS Cluster Sites During Summer

ABSTRACTCombining carnivore movements with site visits to investigate predation events can inform investigators of carnivore diets, kill rates, and risk factors for prey. However, detecting remains of prey can be challenging when prey is small or when vegetation conceals prey. Conservation detection dogs (CDDs) have assisted with wildlife surveys to locate objects of conservation interest, often improving detection over human counterparts. We hypothesized that CDDs would improve efficacy for detection of prey remains at kill locations compared to human searchers. We compared the efficacy of CDD teams (1 dog, 1 human handler) and technician teams (2 humans) for locating prey remains at 729 carnivore cluster (potential predation) sites in the Upper Peninsula of Michigan, USA, during May to August of 2015. Carnivore species included gray wolves (Canis lupus), coyotes (C. latrans), bobcats (Lynx rufus), and American black bears (Ursus americanus). Overall, CDD teams identified prey remains at 2.3 times more clusters, required 42% less search time, and handlers traveled 83% less distance per detected prey remain compared to technician teams. Within carnivore species, CDD teams detected small prey remains at a greater rate than technician teams (4.0–4.3 times greater) for all carnivores except for bobcat which had similar detection rate. Detection of large prey remains (e.g., adult ungulates) was similar between CDD teams and technician teams. Our study supports CDDs ability to outperform humans when searching for objects of conservation interest which are visually cryptic but traceable by scent. Where logistics allow, we recommend use of CDDs over human searchers when it is a priority to locate remains of small prey and when vegetation is dense and may obscure even larger prey items. © 2021 The Wildlife Society.

Editor’s Comment

Editor’s Comment

Two for One: Conservation of Aquatic Ecosystems With Buffers Protects Terrestrial Ecosystems

Abstract We evaluated how three widths of buffer zones on greater than or equal to 100-ha wetlands (240, 300, and 390 m) and rivers (10, 20, and 30 m) would help meet watershed conservation goals in the Upper Peninsula of Michigan, USA, and whether doing so also would protect each of the predominant types of terrestrial natural communities across the landscape. The use of buffer zones (even the narrowest widths assessed) around wetlands and riparian zones met or exceeded conservation targets in 75% of watersheds and greater than or equal to 85% of subwatersheds evaluated. Wetlands and riparian zones with buffers captured each of the predominant types of terrestrial natural community in Michigan's Upper Peninsula, but not proportionately to their availability across the entire landscape. Our work demonstrates that a landscape-conservation approach focused on wetlands and riparian zones with buffers can conserve terrestrial, wetland, and riparian ecosystems across Michigan's Upper Peninsula and may also be applicable in other areas where mapping of wetlands and rivers occurs.

A tale of two habitats: whole-watershed comparison of disturbed and undisturbed river systems in northern Michigan (USA), based on adult Ephemeroptera, Plecoptera, and Trichoptera assemblages and functional feeding group biomass

To test the differences in aquatic insect assemblages between otherwise similar habitats, adult genera of Ephemeroptera, Plecoptera, and Trichoptera (EPT) were sampled using ultraviolet lights during summer and early autumn at 15 sites each throughout the undisturbed Pine River watershed and the agricultural Charlotte River watershed, both of the Upper Peninsula of Michigan (USA). The percentage of intact watershed-scale terrestrial habitat upstream of each sampling site was the best of 32 candidate variables at predicting differences in both EPT taxonomic assemblages and functional feeding group (FFG) biomass. Relative to the Pine, streams of the Charlotte had lower intact habitat, lower genus richness, lower biomass of nearly all individual genera, and lower biomass of all FFGs, with scrapers and shredders decreasing more than filtering collectors. Both watersheds followed general trends of river continuity, although the Pine contained double the relative abundance of shredders than is typically reported. This study demonstrates that watershed-scale habitat disturbance decreases nearly all EPT taxa, regardless of FFG. It also demonstrates the importance of biomass values rather than simple specimen counts when calculating metrics, and the utility of sampling EPT adults with ultraviolet lights relative to sampling benthic specimens.

Rural Community Health: Keeping Michigan's Upper Peninsula Informed During the COVID‐19 Pandemic

During the COVID‐19 pandemic, public health departments and healthcare systems are working to navigate the crisis and protect the community. Those communities in rural areas, where health and communication infrastructure are often limited, face additional challenges in keeping individuals informed, safe, and healthy. Moreover, the amount of misleading information circulating is making it even more difficult to convey critical and rapidly evolving public health recommendations. Michigan Technological University is located in Michigan's rural Upper Peninsula which accounts for 30% of the State's land mass but only 3% of the total population. Our goal was to increase campus and community awareness about COVID‐19 and its impact on health and society.For our rural community, we offered a 1) COVID‐19 public town hall series and 2) COVID‐19 university wide academic course. The public town hall series was delivered weekly and broadcasted live through a webinar (Zoom), social media, and local radio. Each week a speaker panel consisting of public health officials, clinicians, educators, and/or other local experts discussed a COVID‐19 topic theme and answered questions from the community. The academic course was presented as a 1‐credit seminar‐based online course open to any student. Each week students explored a COVID‐19 related topic, participated in the weekly town hall, and engaged in follow‐up discussion and reflection. Primary course learning objectives were for students to locate credible COVID‐19 information sources and describe what is known about the general health impacts of the disease.Twelve public town halls, that included more than 35 different presenters, were delivered. Number of attendees on the Zoom webinars ranged between 20‐75 individuals with many others interacting with content through social media, radio, and the recorded content. Town hall themes included the role of public health to protect community health, impact of disease on physical and mental health, health disparities, mechanisms to interrupt and halt transmission, and strategies for adapting to lifestyle changes. Undergraduate and graduate students (n=37) from a variety of majors (biology, exercise science, chemistry, engineering, business, forestry) enrolled in the course. Nearly all students (96%) reported that the course increased their awareness about COVID‐19 and the majority (61%) indicated that the course was the most effective way to obtain COVID‐19 related information. All students recommended that other students take this course in the future.The public town hall series provided a robust platform to deliver critical, real‐time health information to our campus and broader community during the COVID‐19 pandemic. Additionally, students perceived that the academic course increased their awareness of COVID‐19. Increased public health messaging is a critical step to keeping Michigan's rural Upper Peninsula informed, safe, and healthy during the COVID‐19 pandemic and may serve as a model for other rural university‐community partnerships.

Breeding Bird Occurrence Across a Gradient of Graminoid- to Shrub-Dominated Fens and Fire Histories

Population declines of birds affiliated with grasslands and grass-shrub habitats have been identified as a critical conservation concern. The effects of woody encroachment into grassland-dominated systems, which may contribute to species declines, has been examined mainly in upland systems. We examined occurrence of bird species across a gradient of graminoid- to shrub-dominated wetlands in the Upper Peninsula of Michigan and describe the habitat characteristics associated with their probability of occurrence at segment (100 × 100 m) and landscape (200 m buffer) scales. Because fire can suppress woody encroachment, we also examined the role of fire history, extending from 50 y on birds and habitat characteristics. We focused on seven species closely affiliated with grassland and grass-shrub habitats, but also found in wetlands: Sedge Wren (Asio flammeus), LeConte's Sparrow (Ammodramus leconteii), Savannah Sparrow (Passerculus sandwichensis), Bobolink (Dolichonyx oryzivorus), Common Yellowthroat (Geothlypis trichas), Swamp Sparrow (Melospiza georgiana), and Alder Flycatcher (Empidonax alnorum). We used nonparametric, multiplicative regression models to relate habitat variables and fire history to probability of species occurrence. Unlike studies in upland grasslands, none of the top models included measures of litter or graminoid height, and the highest probability of occurrence often was where graminoid cover was at intermediate rather than highest levels. Measures of woody cover or structure were important to all seven species modeled. We observed few clear differences in habitat metrics across fire history categories beyond the first year of burning. Years since last burned was in the best model for four of the seven species, despite high variability of habitat metrics within fire history categories; those species were more likely to occur in segments burned 15–19 y earlier. Infrequent light- to moderate-severity fires in fens had little effect on focal species occurrence beyond the first year after burning and little long-term effect to suppress woody cover.

A System to Evaluate Prime Farmland Reclamation Success Based on Spatial Soil Properties

Abstract. Scholars, governmental agencies, and concerned citizens are interested in developing empirical predictive models to quantitatively assess the vegetative productivity potentials of reconstructed soils (neo- sols). This research presents equations for a northern Michigan mining region in the Upper Peninsula of Michigan, based on data derived from the National Resources Conservation Service. We employed principal component analysis to develop models to predict the vegetative productivity of corn, corn silage, oats, alfalfa/hay, Irish potatoes, red maple (Acer rubrum L.), white spruce (Picea glauca [Moench] Voss), red pine (Pinus resinosa Aniton), eastern white pine (Pinus strobus L.), jack pine (Pinus banksiana Lamb.), and lilac (Syringa vulgaris L.). Soil attributes that were examined in this research include: available water holding capacity, moist bulk density, % clay, % rock fragments, hydraulic conductivity, % organic matter, soil reactivity, % slope, and topographic position. Four predictive equations based on landscape topography have been developed and are described as an all-mesic woody plant and crop equation, a xeric equation, an equation specific to jack pine, and a wet environment equation. The models were highly significant (p<0.0001) and explained 87.93%, 74.52%, 65.33%, and 87.68% of the variation in site productivity of the respective landscape setting. These equations are intended to assist in efforts to assess the vegetative productivity potentials of reconstructed soils on post-mined landscapes and other disturbed landscapes.

Changes in Population Size and Clustering Behavior of Hibernating Bats in the Upper Peninsula of Michigan After Arrival of White-Nose Syndrome

We examined populations of bats hibernating in 50 abandoned mines in Michigan during the 3 years before and 4–6 years after arrival of the fungal disease white-nose syndrome. Overall size of the regional population fell by 89.9%. Myotis lucifugus (Little Brown Bat), which represented 90% of the pre-epidemic population, declined by 89.9%. Myotis septentrionalis (Northern Long-eared Bat) and Perimyotis subflavus (Tricolored Bat) decreased by 98.5% and 93.9%, respectively, and both species appear threatened with regional extinction. Eptesicus fuscus (Big Brown Bat), in contrast, increased by 11.7%. The disease also impacted social patterns, with the proportion of Little Brown Bats that were solitary during hibernation in 10 of the mines increasing from 23% to 46% after onset of the disease.

New State, Upper Peninsula, and County Records of Mayflies (Ephemeroptera) from the Upper Peninsula of Michigan

New state, Upper Peninsula, and county records of mayflies from the Upper Peninsula of Michigan, U.S.A., are provided. Included are the first Michigan records of eleven species of mayflies, including five from the Family Baetidae [Acentrella nadineae McCafferty, Waltz, and Webb, Anafroptilum minor (McDunnough), Labiobaetis frondalis (McDunnough), Plauditus cestus (Provonsha and McCafferty), and Procloeon rivulare (Traver)], two from Caenidae [Caenis hilaris (Say), and Caenis tardata McDunnough], two from Heptageniidae [Maccaffertium mexicanum integrum (McDunnough), Nixe inconspicua (McDunnough)], one from Isonychiidae [Isonychia sicca (Walsh)], and one from Leptohyphidae [Tricorythodes robacki (Allen)]. In addition, the first Upper Peninsula records are given for eight mayfly species with previously published records from elsewhere in Michigan.

Selection of influential variables in ordinal data with preponderance of zeros

Presence of excess zero in ordinal data is pervasive in areas like medical and social sciences. Unfortunately, analysis of such kind of data has so far hardly been looked into, perhaps for the reason that the underlying model that fits such data, is not a generalized linear model. Obviously some methodological developments and intensive computations are required. The current investigation is concerned with the selection of variables in such models. In many occasions where the number of predictors is quite large and some of them are not useful, the maximum likelihood approach is not the automatic choice. As, apart from the messy calculations involved, this approach fails to provide efficient estimates of the underlying parameters. The proposed penalized approach includes ℓ1 penalty (LASSO) and the mixture of ℓ1 and ℓ2 penalties (elastic net). We propose a coordinate descent algorithm to fit a wide class of ordinal regression models and select useful variables appearing in both the ordinal regression and the logistic regression based mixing component. A rigorous discussion on the selection of predictors has been made through a simulation study. The proposed method is illustrated by analyzing the severity of driver injury from Michigan upper peninsula road accidents.

Regeneration patterns of key pine species in a mixed-pine forest indicate a positive effect of variable retention harvesting and an increase in recruitment with time

BackgroundMany fire-dependent forests have experienced significant declines in species, structural, and functional diversity. These changes are attributed in part to traditional management approaches that were dominated by even-aged regeneration methods such as clearcutting. Variable retention harvesting (VRH) is an ecologically based forestry practice that involves retention of some mature overstory trees and other biological structures in the postharvest stand to emulate the effects of natural disturbance events. In this study, we examined the effect of a VRH treatment on recruitment of historically dominant pine species and understory vegetation two- and six years after its implementation in a naturally regenerated mixed pine forest in the Upper Peninsula of Michigan, USA.ResultsWe found greater regeneration of red pine (Pinus resinosa L.) and eastern white pine (Pinus strobus L.) in VRH stands compared to the unharvested controls. Although red pine recruitment was very low during the first 2 years, both species increased significantly from year two to year six. Recruitment responses for the two species did not differ significantly between the aggregated and dispersed retention treatments. We also found high recruitment of deciduous tree species, consisting primarily of sprouts, and red pine exhibited a negative correlation with these sprouts. Treatment, time, and the interaction of treatment and time were significant factors in red pine recruitment. Time had a strong effect on the understory vegetation, with significant decreases in shrubs and ferns over time.ConclusionsThe results suggest that VRH enhanced recruitment of red pine and eastern white pine and that this recruitment increased with time. We identify competition from sprouts and unfavorable seedbed conditions as the main factors that limited recruitment of red pine during the first 2 years. To reduce competing vegetation and improve seedbed conditions, we suggest following the VRH with a prescribed fire, mechanically removing sprouts, and implementing herbicide treatments. At a time when changes in global climate exacerbates the effects of traditional drivers of forest degradation, and with the need to maintain biodiversity, new ecologically based forest practices such VRH have the potential to facilitate regeneration of native trees and enhance the resilience of many fire-dependent forests.