Acadian Region Research Articles

Can a multistage approach improve individual tree mortality predictions across the complex mixed-species and managed forests of eastern North America?

Tree mortality plays a fundamental role in the dynamics of forest ecosystems, yet it is one of the most difficult phenomena to accurately predict. Various modeling strategies have been developed to improve individual tree mortality predictions. One less explored strategy is the use of a multistage modeling approach. Potential improvements from this approach have remained largely unknown. In this study, we developed a novel multistage approach and compared its performance in individual tree mortality predictions with a more conventional approach using an identical individual tree mortality model formulation. Extensive permanent plot data (n ​= ​9442) covering the Acadian Region of North America and over multiple decades (1965–2014) were used in this study. Our results indicated that the model behavior with the multistage approach better depicted the observed mortality and showed a notable improvement over the conventional approach. The difference between the observed and predicted numbers of dead trees using the multistage approach was much smaller when compared with the conventional approach. In addition, tree survival probabilities predicted by the multistage approach generally were not significantly different from the observations, whereas the conventional approach consistently underestimated mortality across species and overestimated tree survival probabilities over the large range of DBH in the data. The new multistage approach also predictions of zero mortality in individual plots, a result not possible in conventional models. Finally, the new approach was more tolerant of modeling errors because it based estimates on ranked tree mortality rather than error-prone predicted values. Overall, this new multistage approach deserves to be considered and tested in future studies.

Geographic determinants of colorectal cancer in Louisiana

PurposeCurrently, rural residents in the United States (US) experience a greater cancer burden for tobacco-related cancers and cancers that can be prevented by screening. We aim to characterize geographic determinants of colorectal cancer (CRC) incidence in Louisiana due to rural residence and other known geographic risk factors, area socioeconomic status (SES), and cultural region (Acadian or French-speaking).MethodsPrimary colorectal cancer diagnosed among adults 30 years and older in 2008–2017 were obtained from the Louisiana Tumor Registry. Population and social and economic data were obtained from US Census American Community Survey. Rural areas were defined using US Department of Agriculture 2010 rural–urban commuting area codes. Estimates of relative risk (RR) were obtained from multilevel binomial regression models of incidence.ResultsThe study population was 16.1% rural, 18.4% low SES, and 17.9% Acadian. Risk of CRC was greater among rural white residents (RR Women: 1.09(1.02–1.16), RR Men: 1.11(1.04–1.18)). Low SES was associated with increased CRC for all demographic groups, with excess risk ranging from 8% in Black men (RR: 1.08(1.01–1.16)) to 16% in white men (RR: 1.16(1.08–1.24)). Increased risk in the Acadian region was greatest for Black men (RR: 1.21(1.10–1.33)) and women (RR: 1.21(1.09–1.33)). Rural–urban disparities in CRC were no longer significant after controlling for SES and Acadian region.ConclusionSES remains a significant determinant of CRC disparities in Louisiana and may contribute to observed rural–urban disparities in the state. While the intersectionality of CRC risk factors is complex, we have confirmed a robust regional disparity for the Acadian region of Louisiana.

Genetic Analysis of Archived Tumor Specimens for Hereditary Colorectal Cancer Syndromes in the Cajuns of Louisiana, a US Founder Population.

INTRODUCTION:The Louisiana Acadian region (population 1.2 million), home of the Cajuns, has among the highest US colorectal cancer (CRC) rates. Although Cajuns are a known genetic founder population, studies assessing for hereditary CRC have not been performed.METHODS:A retrospective review of 2 hospital cancer registries was performed to identify young (<55) Cajun CRC patients in Lafayette, Louisiana (the Acadian region population center), diagnosed from 2003 to 2016. Men were studied because of the higher likelihoods of retaining Cajun surnames for ancestry identification compared with women. Immunohistochemistry for mismatch repair proteins associated with the Lynch syndrome (LS) was performed on tumors. Germline sequencing was performed on adjacent normal tissue of these archived formalin-fixed paraffin-embedded surgical resection specimens for pathogenic variants underlying CRC-associated syndromes, including LS, familial adenomatous polyposis, and others.RESULTS:Of 9 young Cajuns, a germline analysis revealed LS in 2 (MLH1 frameshift, MLH1 missense pathogenic variants). Both had immunohistochemistry-deficient MLH1. Two others had the same adenomatous polyposis coli variant of unknown significance (2 algorithms predicting deleterious and probably damaging change), making this a potential familial adenomatous polyposis founder effect candidate.DISCUSSION:This is the first study assessing for hereditary CRC in a large US regional founder population. This small study did not identify clear Cajun founder pathogenic variants. However, larger studies are warranted, which could also help clarify the clinical significance of the adenomatous polyposis coli variant of unknown significance. This study is important because it demonstrates that a retrospective tumor analysis can be used to ascertain the prevalence of genetic susceptibility in specific populations.

Next generation DNA sequencing reveals allopolyploid origin of decaploid Isoëtes lacustris (Isoëtaceae)

Abstract Isoetes L. is a cosmopolitan genus comprising about 200 species, almost half of them being allo- or autopolyploids. We investigated the origin of decaploid I. lacustris using next generation sequencing (NGS). We sequenced the second intron of LEAFY (LFYint2) and analysed the morphology of seven samples of I. lacustris from five localities from East Europe and West Siberia. We have shown that I. lacustris is an allopolyploid having in its genome the subgenomes of the North American diploid I. prototypus, tetraploid I. tuckermanii (which contains subgenomes of diploid I. viridimontana and unknown species), and one more unknown diploid progenitor. NGS showed high reproducibility, demonstrating the same sets of LFYint2 copies in all the samples. The potential fifth subgenome has not been found, most likely due to a loss of the LEAFY gene as a result of subgenome reduction, as is characteristic of polyploids. These data imply that the ancestor of I. lacustris most likely originated in the north-east of North America (New England and Acadian region) where I. prototypus, I. tuckermanii and I. viridimontana co-occur, and that I. lacustris then spread to Eurasia via the North Atlantic Land Bridge. NGS-based amplicon sequencing has the potential to evaluate the ratio of frequency of different copies and to distinguish allopolyploidy and autopolyploidy (if the PCR efficiency of each of the copies is taken into account). This is especially useful, given that both play a prominent role in Isoetes evolution. We also demonstrate that widely adopted cloning of LFYint2 in Isoetes leads to biased results due to the amplification errors.

Evaluating and modeling variation in site-level maximum carrying capacity of mixed-species forest stands in the Acadian Region of northeastern North America

Currently no universal approach exists to estimate regional site-level maximum carrying capacity in terms of stand densityindex (SDIMAX) of mixed species stands across contrasting forest ecosystems. Regional research efforts that account forinfluential stand-level variables and species traits are needed to reliably derive SDIMAXunder varying environmental conditions and stand characteristics. This study used regionally comprehensive forest inventory data from various permanentsampling efforts to evaluate the effects of contrasting biotic and abiotic stand- and site-level factors on SDIMAXof multiple-species, structurally heterogeneous stands of the climatically diverse Acadian Forest Region of North America. Specifically,we aimed to i) quantify the stand-level maximum size-density line for an array of forest stands found across the study area,irrespective of stand structure; ii) evaluate the relationship between this stand-specific estimate of SDIMAXand various other stand-level attributes; and, iii) develop a generalized SDIMAXprediction model using SDIMAXestimates from objective i) aswell as potential regional drivers of SDIMAXfrom objective ii). The most influential stand-level factors on SDIMAXwere proportion of total stand basal area in hardwood species, basal area weighted mean specific gravity, range in stem diameter, andspecies diversity. Direct climatic variables were not included in our SDIMAXprediction model due to the limited variationexplained, but relationships with elevation and a site quality index based on these climatic variables were. Overall, we con-clude that i) variation in SDIMAX appears to be mostly driven by the softwood to hardwood ratio of the mixed species,structurally complex stands evaluated in our study and ii) the general approach offers a viable framework for estimating sitemaximum carrying capacity at a regional-scale and effectively managing stand density accordingly.

Evaluating the influence of stem form and damage on individual-tree diameter increment and survival in the Acadian Region: implications for predicting future value of northern commercial hardwood stands

Northern hardwood species display a variety of forms and defects that can reduce stem quality and complicate their timber management. However, for the most part, growth and yield models do not account for the influence of stem form and damage. This study determined the influence of stem form and damage on growth, survival, and projected future sawlog value among several northern commercial hardwood species. To accomplish this, hardwood trees on 112 permanent plots across three long-term research sites in Maine were assigned stem form and risk classes using a tree classification system developed in New Brunswick. A highly significant influence of stem form and risk on annualized individual-tree diameter increment and survival was found. Inclusion of these equations into a regional growth and yield model highlighted the importance of stem form and defects on long-term simulations as projected stand-level future value was significantly reduced by over 17%, on average (range of 13% to 28%), when compared with projections that did not include that tree-level information. The results highlight the importance of stem form and defects, as well as the need to account for them, in growth and yield applications that assess the forecasted value of commercially important hardwood stands.

Variation in the maximum stand density index and its linkage to climate in mixed species forests of the North American Acadian Region

Maximum stand density index (SDImax) is an important factor controlling stand dynamics that varies by species and region, but less is understood how it differs within a region for a given species. In this analysis, linear quantile mixed modeling (LQMM) and an extensive network of permanent plots were utilized to examine regional variation in the SDImax of 15 species (7 softwoods and 8 hardwoods) across the complex forests of the Acadian Region in North America. Observed plot-level SDImax was then linked to various stand, plant trait, site, and climatic factors and the spatial patterns throughout the region examined. Results indicated high variability of SDImax for a given species with northern hardwood species like yellow birch (Betula alleghaniensis Britt.), sugar maple (Acer saccharum Marsh.), and American beech (Fagus grandifolia Ehrh.) having the lowest values (555 – 627), while softwood species such as northern white cedar (Thuja occidentalis L.; 1014), eastern hemlock (Tsuga canadensis (L.) Carr.; 1026), and white pine (Pinus strobus L.; 967) had the highest values. Compared to the other stand and site factors examined, climate showed the strongest relationship with SDImax with R2 ranging from 82 to 98%. Of the climatic variables examined, those representing growing season length and the timing of precipitation were most influential. For the majority of the species examined, reductions in SDImax were forecasted due to changing climatic conditions. Across species, mean SDImax was found to linearly decline with wood specific gravity and increase with leaf longevity, but showed limited relationships with other species-level functional traits. Overall, the analysis highlights the strong variability of SDImax within and between species as well as the important role that climate has on this attribute within a region.

Colorectal Cancer Incidence Rates in the Louisiana Acadian Parishes Demonstrated to be Among the Highest in the United States.

Objectives:Determine whether colorectal cancer (CRC) rates are disproportionately high in the French-Acadian region (population 1.2 million) of Louisiana, home of the Cajuns, a founder population.Methods:2005–2009 cancer incidence rates were stratified by age/race/gender in the 18 Acadian parish region and 9-parish subgroup with higher proportions of French speakers and compared with Louisiana and United States rates. Parishes were identified through language census data. A total of 3,288 CRC cases were identified in the Acadian region and 11,737 in Louisiana.Results:CRC rates in whites and white males in the 18 parishes were statistically significantly higher than both Louisiana and US rates. In the 9 parishes, rates increased further; whites had an incidence of 56.1/100,000, 13% higher than Louisiana (P<0.0003) and 23% higher than US rates (P<0.0001). In white males, incidence was 72.6/100,000, 19% higher than Louisiana (P<0.0002) and 37% higher than US rates (P<0.0001). If the 9-parish regions were considered a “state,” white males would have the highest CRC incidence in the United States by 11% (P<0.0175) compared with other white male populations.Conclusions:CRC rates are among the highest in the United States, increasing with the proportion of French speakers, a marker for the Cajun population. This appears to be the first study identifying a high rate of cancer in a large, regional, US founder population, raising the possibility of a genetic predisposition. Alternatively, an unidentified, robust environmental risk factor may be present. Future studies are needed to identify genetic and/or other risk factors in this population.

Midrotation response of ground vegetation to herbicide and precommercial thinning in the Acadian Forest of Maine, USA

Silvicultural practices can directly or indirectly influence the abundance and diversity of ground vegetation, and thereby influence a vital component of forest ecosystems. As silvicultural intensity increases, understanding the effects on ground vegetation become more critical. Long-term data on the response of ground vegetation to various intensities of forest management are limited. Therefore, we used a long-term experiment to quantify how individual and combined applications of herbicide and precommercial thinning (PCT) early in stand development influenced the cover, richness, and diversity of ground vegetation at midrotation (30–40years) in spruce–fir stands of the Acadian Region. Aerial application of different herbicides (including glyphosate, triclopyr, and phenoxys) had no long-term effect (23–33years after treatment) on cover, richness, and diversity of ground vegetation. In contrast, PCT had a positive and long-lasting effect (up to 24years post-treatment) on ground vegetation cover, richness, and diversity. Our results indicated that overstory structure had a larger influence on ground vegetation than overstory species composition. Thus, manipulation of stand structure and the maintenance of a variety of stand structures across the landscape are important strategies for managing the diversity of ground vegetation. We conclude that PCT, especially following herbicide application, is an effective silvicultural tool for the maintenance of ground vegetation diversity, as well as timber production.

Assessing and modeling snag survival and decay dynamics for the primary species in the Acadian forest of Maine, USA

Snags are an important component of forest structure and a key carbon pool, but there is currently a limited understanding of their survival and decay in the Acadian region of North America. Using standing and fallen snag observations collected from permanent sample plot (PSP) remeasurements at a long-term, replicated silviculture methods experiment in central Maine, USA, the objective of this analysis was to develop quantitative models to better understand snag survival and decay dynamics. Species examined included the conifers Abies balsamea, Picea rubens, Thuja occidentalis, and Tsuga canadensis, and the hardwoods Acer rubrum and Betula papyrifera. Proportional hazards regression models that estimate the 5-year probability (Pr) of snag survival indicated that observed decay class (a measure of snag decomposition) could be used as a surrogate for years since death given the difficulties and errors associated with determining years since death for standing snags. Averaged across all species, Pr (5-year snag survival) estimated as a function of snag diameter at breast height (dbh) in decay classes 1, 2, 3, and 4 were predicted as 0.69±0.09 (mean±standard deviation), 0.36±0.09, 0.16±0.05, and 0.06±0.02, respectively. Where snag dbh was significant in estimating survival (3 of 6 species), hazard ratios indicated that snag survival would increase by as much as 24% for each 10cm increase in dbh, but was dependent on species. Probability matrices predicting the 5-year likelihood of snags transitioning to advanced decay classes or falling showed that T. canadensis and T. occidentalis snags were slowest to decay, as measured by the average time it takes for a snag to progress from decay class 1–4. Probability of snag height-loss, predicted using snag dbh and the harvest interval of the stand, was estimated to be highest for larger dbh snags found in stands with frequent harvest intervals (e.g. 40cm dbh and every 5years). Models predicting the amount of volume reduced in standing snags through time were related to the estimated total volume of a live tree with the same dbh, mode of death, and general decay stage (i.e. soft versus hard). When used together, these models quantifying snag dynamics and associated species and size differences can serve as tools for managers to estimating standing deadwood stocks in mixed-species stands found throughout the Acadian region.

Development of regional height to diameter equations for 15 tree species in the North American Acadian Region

Summary Equations that relate individual tree diameter at breast height (d.b.h.) and total height (HT) are important because HT is not widely measured and is often needed to estimate stem volume or predict HT growth. The primary goal of the study was to construct a regional HT to d.b.h. equation (H-D) for 15 tree species of the Acadian Region. Specific objectives were to (1) evaluate performance of the Forest Vegetation Simulator Northeast Variant (FVS-NE) equations, (2) explore suitable model forms and compare the influence of various tree- and stand-level variables on HT prediction and (3) develop species-specific equations that are unbiased across a broad geographic region. Data were available from an extensive database covering Maine, three provinces of the Canadian Maritimes and southern Quebec. The study showed that the widely used FVS-NE model had significant prediction biases for all species in the region. The best model form among those evaluated was the von Bertalanffy–Richards (vB-R; commonly referred to as the Chapman–Richards), with added covariates that included crown competition factor, basal area in trees larger than subject tree and a climate-derived site index.

Regional Stem Taper Equations for Eleven Conifer Species in the Acadian Region of North America: Development and Assessment

Taper models to predict upper stem diameters, as well as total tree volume, are presented for 11 major conifer species in the Acadian Forest Region of North America. The Kozak (2004. My last words on taper equations. For. Chron. 80:507‐514) Model 02 taper equation was used as the base model form. A nonlinear mixed-effects modeling approach was used to account for autocorrelation present among multiple stem analysis observations collected from the same tree. Results show that fitted taper equations can accurately predict both stem form and volume across a range of conditions. The taper models generally had slightly lower bias and root mean square error than the commonly used regional Honer refitted volume equations (1965. A new total cubic foot volume function. For. Chron. 41:476‐493). The mean absolute bias was reduced up to 28% for certain species using the fitted taper equations compared with the refitted Honer (1965) equations, although the refitted Honer's models are also quite accurate where total stemwood volumes are needed. Independent validation data sets were used to further confirm reliability and accuracy of fitted taper models in predicting tree volume. These data sets indicated that the equations performed well, in general, but were slightly biased in certain thinned stands and in some New Brunswick ecoregions. Additional data are needed to confirm this and potentially improve model behavior. Overall, the models will be useful for predicting both stem form and merchantable and total volume.

Development of height to crown base models for thirteen tree species of the North American Acadian Region

Height to live crown base (HCB) is an important input variable for several growth and yield models. Since HCB is rarely measured in the field, it is often predicted using static models. Instead of predicting HCB, the Forest Vegetation Simulator Northeastern Variant (FVS-NE) uses an equation that predicts crown ratio (CR), which has not been well validated. The main goal of the present study was to construct a regional HCB model for thirteen selected tree species of the Acadian Region of North America. The specific objectives were to: 1) evaluate FVS-NE model predictions, 2) compare suitable model forms, and 3) assess influence of various covariates to improve predictions. We evaluated three model forms, namely Holdaway (1986), logistic, and exponential. The findings indicated that FVS-NE models were significantly biased for all species as the overall mean bias and root mean square error (RMSE) were 0.11 m and 1.80 m, respectively. A logistic equation with size (diameter at breast height [DBH], total height [HT] and ratio of DBH to HT), and competition (crown competition factor [CCF] and basal area larger than subject tree [BAL]) gave the best predictions for all species in this analysis. This model had an overall mean bias &lt;0.01 m and an RMSE of 1.59 m, which represents a significant improvement in predictions compared to FVS-NE. Despite the range of species and observed variation in the data, the equations worked well and can be easily calibrated to new stands with a few local observations.

Estimating and predicting bark thickness for seven conifer species in the Acadian Region of North America using a mixed-effects modeling approach: comparison of model forms and subsampling strategies

In many situations, information on stem diameters inside bark (dib) are more desirable than on diameters outside bark (dob). However, obtaining dib measurements is usually expensive, time-consuming, and prone to significant measurement errors when done on standing trees. Many bark thickness equations have been proposed to estimate the dibs of standing trees. In this study, we compared several commonly used bark thickness equations for seven conifer species in the Acadian Region of North America. Mixed-effects modeling techniques were employed to fit linear and non-linear bark thickness equations. We found the equation proposed by Cao and Pepper (South J Appl Forestry 10:220–224, 1986; Eq. 5) performed significantly better than other equations for most of our study species. The Cao and Pepper (South J Appl Forestry 10:220–224, 1986) equation is a function of dob, relative height in the stem, tree height, and the ratio of dib to dob at breast height. The mean absolute bias was found to be reduced up to 74% compared with using a fixed ratio approach employed in the widely used Northeastern variant of the Forest Vegetation Simulator (FVS-NE) growth and yield model. Leave-one-out cross validation was further performed to determine the location of suitable prior measurements in the prediction process for three of the most well-behaved equations. Results show that no unified prior measurement can provide best predictive abilities across all species as the choice of prior dib measurements depends on both species and bark thickness equations.

Comparison of model forms for estimating stem taper and volume in the primary conifer species of the North American Acadian Region

• The performance of ten commonly used taper equations for predicting both stem form and volume in balsam fir [ Abies balsamea (L.) Mill], red spruce[ Picea rubens (Sarg.)], and white pine[ Pinus strobus (L.)] in the Acadian Region of North America was investigated.• Results show that the Kozak () and Bi () equations were superior to the other equations in predicting diameter inside bark for red spruce and white pine, while the Valentine and Gregoire () equation performed slightly better for balsam fir.• For stem volume, the Clark et al. () equation provided the best predictions across all species when upper stem diameter measurements were available, while the Kozak () and compatible taper equation of Fang et al. () performed well when those measurements were unavailable.• The incorporation of crown variables substantially improved stem volume predictions (mean absolute bias reduction of 7–15%; root mean square error reduction of 10–15%) for all three species, but had little impact on stem form predictions.• The best taper equation reduced the predicted root mean square error by 16, 39, and 45% compared to estimates from the widely used Honer (1965) regional stem volume equations for balsam fir, red spruce, and white pine, respectively.• When multiple taper equations exist for a certain species, the use of the geometric mean of all predictions is an attractive alternative to selecting the “best”equation.

Decaying wood and tree regeneration in the Acadian Forest of Maine, USA

We examined the effect of management history on the availability of decayed downed wood and the use of downed wood as a regeneration substrate in mixed-species stands in the Acadian Forest of Maine. Regeneration of red spruce ( Picea rubens Sarg.), eastern hemlock ( Tsuga canadensis (L.) Carr.), balsam fir ( Abies balsamea L. Mill), and red maple ( Acer rubrum L.) was quantified. Treatments included variants of selection cutting, commercial clearcutting (unregulated harvesting), and no harvesting for >50 years (reference). Area of wood substrate (wood ≥ Decay Class III and ≥10 cm on at least one end) was less in the commercial clearcut than in the reference; other treatments were not differentiated. Spruce and hemlock seedlings were found at higher densities on wood than paired forest floor plots of equal area, regardless of treatment. Conversely, fir and maple were less abundant on wood than forest floor plots in reference and selection treatments, but more or equally abundant on wood than forest floor plots in the commercial clearcut. These findings suggest that silvicultural treatment affects both the availability of decayed downed wood and seedling-substrate relationships, and that forest management in the Acadian Region should consider availability of downed woody material.

Long-term effects of precommercial thinning on the stem dimensions, form and branch characteristics of red spruce and balsam fir crop trees in Maine, USA

The effects of precommercial thinning (PCT) on stem dimensions, form, volume, and branch attributes of red spruce [Picea rubens Sarg.] and balsam fir [Abies balsamea (L.) Mill.] crop trees were assessed 25 years after treatment in an even-aged northern conifer stand. Treatments were a uniform 2.4 x 2.4-m spacing and a control (no PCT). The PCT treatment significantly increased individual tree diameter at breast height (DBH), height growth, crown ratio, and crown width, while it reduced the tree height to DBH ratio. PCT also significantly increased stem taper and consequently, regional volume equations overpredicted observed stem volume by 2 to 15%, particularly for the spaced trees. PCT also increased the number and maximum size of branches on the lower bole. The sizes of knots on half of the sampled spruce crop trees in the spaced plots precluded them from being used as select structural lumber; there were no other effects on log grade. Our findings indicate that PCT can have a long-term influence on the structural attributes of individual trees, and that improved stem-volume prediction equations are needed in the Acadian region of North America.

Cultural rural tourism: Evidence from Canada

Tourism has become a development tool for many rural and more isolated areas to supplement traditional industries that are often in decline. In this paper, development of cultural rural tourism is examined in a case study of a French Acadian region on an island in eastern Canada. The roles of culture and community-based partnerships are considered in a proposed framework with four evolving development stages. The findings suggest that the framework is useful for rural tourism development; that culture, which is often well preserved in rural areas, is a valuable resource to include; and that community-based partnerships such as cooperatives may be very effective.