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Hyon K Choi - One of the best experts on this subject based on the ideXlab platform.

  • op0247 persistent premature mortality gap in idiopathic inflammatory myopathy a general population based cohort study
    Annals of the Rheumatic Diseases, 2020
    Co-Authors: Kristin M Dsilva, A Ogdie, A Avina, Hyon K Choi
    Abstract:

    Background: Idiopathic inflammatory myopathy (IIM) is associated with significant premature mortality; however, whether the mortality gap has improved over recent years is unknown. Objectives: To determine trends in premature mortality in patients with IIM in a large cohort, representative of the United Kingdom (UK) general population. Methods: Using The Health Improvement Network (THIN), an electronic medical record database representative of the UK general population, we identified patients with incident IIM between 18 and 89 years of age (defined by at least one Read diagnosis code for dermatomyositis, polymyositis, or interstitial myositis with at least one year of continuous enrollment in THIN prior to the cohort entry date) and up to 10 controls without IIM matched on age, sex, birth year, and database entry year. The cohort was divided in two based on the year of IIM diagnosis: the early cohort (1999-2006) and the late cohort (2007-2014). We calculated adjusted hazard ratios for death using a multivariable Cox-proportional hazards model and adjusted rate differences using an additive hazard model. Results: The early cohort consisted of 355 patients with IIM and 3182 matched controls, while the late cohort consisted of 396 IIM patients and 3551 matched controls. In both cohorts, IIM patients had excess mortality compared to matched controls [57.4 vs. 15.2 deaths/1000 person-years (PY) in the early cohort and 43.2 vs. 14.1 deaths/1000 PY in the late cohort] (Table). The corresponding multivariate mortality hazard ratios were 2.73 (95% CI, 1.85 to 4.03) vs. 2.61 (95% CI, 1.75 to 3.89) in the early and late cohorts, respectively (p-value for interaction = 0.63) (Figure). The absolute multivariate mortality differences were 36.6 (95% CI, 20.4 to 52.8) and 25.8 (95% CI, 13.7 to 37.9) deaths/1000 PY, in the early and late cohorts, respectively (p-value for interaction = 0.24). Conclusion: In this general population-based cohort study, patients with IIM had over 2.5 times the risk of death compared to matched controls, even after adjusting for comorbidities and medications. Unlike trends seen in rheumatoid arthritis and granulomatosis with polyangiitis, there appears to be no improvement in mortality in IIM in recent years. This highlights the need for improved strategies for the management of patients with IIM and its comorbidities. Disclosure of Interests: Kristin D’Silva: None declared, Leo Lu: None declared, Alexis Ogdie Grant/research support from: Pfizer to Penn, Novartis to Penn, Amgen to Forward/NDB, Consultant of: Abbvie, Amgen, Bristol-Myers Squibb, Celgene, Corrona, Janssen, Eli Lilly, Novartis, Pfizer, Antonio Avina: None declared, Hyon Choi Grant/research support from: Ironwood, Horizon, Consultant of: Takeda, Selecta, Horizon, Kowa, Vaxart, Ironwood

  • thu0020 no causal association of serum urate or gout with alzheimer s disease a mendelian randomization analysis
    Annals of the Rheumatic Diseases, 2020
    Co-Authors: S Marozoff, Natalie Mccormick, J Choi, Hyon K Choi
    Abstract:

    Background: Several epidmiologic studies have found a lower risk of Alzheimer’s disease (AD) among individuals with a history of gout1 or high serum urate levels2, which are the precursor to gout. Serum urate may have neuroprotective benefits for AD, however it is possible that reverse causation and residual confounding could explain the observational evidence. Objectives: To study the causal associations of serum urate and gout with Alzheimer’s disease using Mendelian Randomization (MR) methods. Methods: Two-sample MR was performed to examine the causality of: 1) serum urate on Alzheimer’s disease and 2) gout on Alzheimer’s disease. Single nucleotide polymorphisms (SNP) identified from a genome-wide association study of 457,690 adults described 183 SNPs associated with serum urate and gout, which were used as instrumental variables3. Additional single-SNP analyses were conducted using SNPs from three genes identified as major determinants of urate levels (SLC2A9, SLC22A12, and ABCG2). SNPs for AD came from the International Genomics of Alzheimer’s Project, comprised of 35,274 AD cases and 59,163 cognitively normal elderly controls4. Inverse-variance weighted (IVW) models were the primary method used to examine the associations between each exposure and risk of AD. Additional analyses examined the potential impact of pleiotropy via MR-Egger models. Single-SNP analyses used the Wald ratio. All analyses were performed using R. Results: There was no evidence of a causal association between genetically-determined serum urate or gout and risk of AD from IVW analyses (both p>0.1) (Table 1). MR-Egger analyses yielded similar estimates (both p>0.1) and the intercepts of the MR-Egger regressions did not suggest the presence of directional pleiotropy (p=0.64 for serum urate exposure and p=0.98 for gout exposure) (Table 1). Additionally, none of the three individual SNPs were significantly associated with risk of AD (all p>0.05) (Table 2). Conclusion: Using both serum urate and gout as instrumental variables in MR analysis, these findings suggest that serum urate and gout are not causal determinants for the development of AD. The inverse associations described in observational studies may in part be due to confounding or reverse causality. References: [1]Lu N, et al. Gout and the risk of Alzheimer’s disease: a population-based, BMI-matched cohort study. Annals of the Rheumatic Diseases, 2016. doi:10.1136/annrheumdis-2014-206917 [2]Scheepers LEJM, et al. Urate and risk of Alzheimer’s disease and vascular dementia: A population-based study. Alzheimer’s & Dementia, 2019. doi:10.1016/j.jalz.2019.01.014 [3]Tin A, et al. Target genes, variants, tissues and transcriptional pathways influencing human serum urate levels. Nature Genetics, 2019. doi:10.1038/s41588-019-0504-x [4]Kunkle BW, et al. Genetic meta-analysis of diagnosed Alzheimer’s disease identifies new risk loci and implicates Aβ, Tau, immunity and lipid processing. Nature Genetics, 2019. doi: 10.1038/s41588-019-0358-2 Disclosure of Interests: Shelby Marozoff: None declared, Natalie McCormick: None declared, Jeewoong Choi: None declared, Hyon Choi Grant/research support from: Ironwood, Horizon, Consultant of: Takeda, Selecta, Horizon, Kowa, Vaxart, Ironwood

  • thu0020 no causal association of serum urate or gout with alzheimer s disease a mendelian randomization analysis
    Annals of the Rheumatic Diseases, 2020
    Co-Authors: S Marozoff, Natalie Mccormick, J Choi, Hyon K Choi
    Abstract:

    Background: Several epidmiologic studies have found a lower risk of Alzheimer’s disease (AD) among individuals with a history of gout1 or high serum urate levels2, which are the precursor to gout. Serum urate may have neuroprotective benefits for AD, however it is possible that reverse causation and residual confounding could explain the observational evidence. Objectives: To study the causal associations of serum urate and gout with Alzheimer’s disease using Mendelian Randomization (MR) methods. Methods: Two-sample MR was performed to examine the causality of: 1) serum urate on Alzheimer’s disease and 2) gout on Alzheimer’s disease. Single nucleotide polymorphisms (SNP) identified from a genome-wide association study of 457,690 adults described 183 SNPs associated with serum urate and gout, which were used as instrumental variables3. Additional single-SNP analyses were conducted using SNPs from three genes identified as major determinants of urate levels (SLC2A9, SLC22A12, and ABCG2). SNPs for AD came from the International Genomics of Alzheimer’s Project, comprised of 35,274 AD cases and 59,163 cognitively normal elderly controls4. Inverse-variance weighted (IVW) models were the primary method used to examine the associations between each exposure and risk of AD. Additional analyses examined the potential impact of pleiotropy via MR-Egger models. Single-SNP analyses used the Wald ratio. All analyses were performed using R. Results: There was no evidence of a causal association between genetically-determined serum urate or gout and risk of AD from IVW analyses (both p>0.1) (Table 1). MR-Egger analyses yielded similar estimates (both p>0.1) and the intercepts of the MR-Egger regressions did not suggest the presence of directional pleiotropy (p=0.64 for serum urate exposure and p=0.98 for gout exposure) (Table 1). Additionally, none of the three individual SNPs were significantly associated with risk of AD (all p>0.05) (Table 2). Conclusion: Using both serum urate and gout as instrumental variables in MR analysis, these findings suggest that serum urate and gout are not causal determinants for the development of AD. The inverse associations described in observational studies may in part be due to confounding or reverse causality. References: [1]Lu N, et al. Gout and the risk of Alzheimer’s disease: a population-based, BMI-matched cohort study. Annals of the Rheumatic Diseases, 2016. doi:10.1136/annrheumdis-2014-206917 [2]Scheepers LEJM, et al. Urate and risk of Alzheimer’s disease and vascular dementia: A population-based study. Alzheimer’s & Dementia, 2019. doi:10.1016/j.jalz.2019.01.014 [3]Tin A, et al. Target genes, variants, tissues and transcriptional pathways influencing human serum urate levels. Nature Genetics, 2019. doi:10.1038/s41588-019-0504-x [4]Kunkle BW, et al. Genetic meta-analysis of diagnosed Alzheimer’s disease identifies new risk loci and implicates Aβ, Tau, immunity and lipid processing. Nature Genetics, 2019. doi: 10.1038/s41588-019-0358-2 Disclosure of Interests: Shelby Marozoff: None declared, Natalie McCormick: None declared, Jeewoong Choi: None declared, Hyon Choi Grant/research support from: Ironwood, Horizon, Consultant of: Takeda, Selecta, Horizon, Kowa, Vaxart, Ironwood

  • sat0703 racial disparities in gout and hyperuricemia a united states general population study
    Annals of the Rheumatic Diseases, 2018
    Co-Authors: Michael Chenxu, Chio Yokose, Hyon K Choi
    Abstract:

    Background Although African-Americans (AAs) have a higher prevalence of risk factors for gout and hyperuricemia (e.g., hypertension, obesity, and chronic kidney disease [CKD]) than Whites, data on their disease burden of gout and hyperuricemia remains scarce. Objectives To examine potential racial/ethnic disparities in the prevalence of gout and hyperuricemia, using a nationally-representative sample of United States (US) adults over the past 10 years (The National Health and Nutrition Examination Survey [NHANES] 2007–16). Methods Using data from 26 332 participants aged ≥20 years (13 539 females and 12 793 males) from NHANES 2007–16, we calculated the age-standardised prevalence of gout and hyperuricemia by race/ethnicity. Gout was defined by report of a diagnosis by a health professional, and hyperuricemia as a serum urate >7.0 mg/dL (0.42 mmol/L) from participants’ blood samples. Logistic regression was used to adjust for covariates, while taking into account clusters and strata of the complex survey design of NHANES. Results The age-standardised prevalence of gout was 3.7% for Whites and 4.7% for AAs, with the age-standardised prevalence of hyperuricemia being 12.7% and 14.9% for Whites and AAs, respectively. Compared to Whites, AAs had a 65% higher odds of gout among females (age-adjusted OR, 1.65; 95% CI, 1.14 to 2.38) and a 31% higher odds of gout among males (age-adjusted OR, 1.31; 95% CI, 1.05 to 1.63). Further adjustment by body-mass index (BMI) attenuated these associations to non-significance for both sexes (table 1). AA females had a higher odds of hyperuricemia than White females (age-adjusted OR, 2.17; 95% CI, 1.72 to 2.73), but not males (age-adjusted OR, 1.08; 95% CI, 0.95 to 1.22; P for interaction=0.002) (table 1). Among females, this association attenuated after further adjustment for BMI, hypertension, CKD, type 2 diabetes mellitus, household income, and education, but remained significant (adjusted OR, 1.52; 95% CI, 1.19 to 1.95). Conclusions These nationally-representative data indicate that AAs have a larger disease burden of gout and hyperuricemia than Whites, particularly among women. This burden appears to be at least partly due to a higher prevalence of risk factors for hyperuricemia in AAs. 1 Reference [1] Flegal KM, et al. JAMA2016Jun 7;315(21):2284–2291. Disclosure of Interest M. Chen-Xu: None declared, C. Yokose: None declared, H. Choi Grant/research support from: Ironwood and Ardea/AstraZeneca, Consultant for: Horizon and Selecta

Megan S. Matonis - One of the best experts on this subject based on the ideXlab platform.

  • modelling for forest management synergies and trade offs northern hardwood tree regeneration timber and deer
    Ecological Modelling, 2013
    Co-Authors: James D. A. Millington, Michael B Walters, Megan S. Matonis
    Abstract:

    In many managed forests, tree regeneration density and composition following timber harvest are highly variable. This variability is due to multiple environmental drivers – including browsing by herbivores such as deer, seed availability and physical characteristics of forest gaps and stands – many of which can be influenced by forest management. Identifying management actions that produce regeneration abundance and composition appropriate for the long-term sustainability of multiple forest values (e.g., timber, wildlife) is a difficult task. However, this task can be aided by simulation tools that improve understanding and enable evaluation of synergies and trade-offs between management actions for different resources. We present a forest tree regeneration, growth, and harvest simulation model developed with the express purpose of assisting managers to evaluate the impacts of timber and deer management on tree regeneration and forest dynamics in northern hardwood forests over long time periods under different scenarios. The model couples regeneration and deer density sub-models developed from empirical data with the Ontario variant of the US Forest Service individual-based forest growth model, Forest Vegetation Simulator. Our error analyses show that model output is robust given uncertainty in the sub-models. We investigate scenarios for timber and deer management actions in northern hardwood stands for 200 years. Results indicate that higher levels of mature Ironwood (Ostrya virginiana) removal and lower deer densities significantly increase sugar maple (Acer saccharum) regeneration success rates. Furthermore, our results show that although deer densities have an immediate and consistent negative impact on forest regeneration and timber through time, the non-removal of mature Ironwood trees has cumulative negative impacts due to feedbacks on competition between Ironwood and sugar maple. These results demonstrate the utility of the simulation model to managers for examining long-term impacts, synergies and trade-offs of multiple forest management actions.

  • combined long term effects of variable tree regeneration and timber management on forest songbirds and timber production
    Forest Ecology and Management, 2011
    Co-Authors: James D. A. Millington, Michael B Walters, Edward J Laurent, Megan S. Matonis, Kimberly R Hall
    Abstract:

    The structure of forest stands is an important determinant of habitat use by songbirds, including species of conservation concern. In this paper, we investigate the combined long-term impacts of variable tree regeneration and timber management on stand structure, songbird occupancy probabilities, and timber production in northern hardwood forests. We develop species-specific relationships between bird species occupancy and forest stand structure for canopy-dependent black-throated green warbler (Dendroica virens), eastern wood-pewee (Contopus virens), least flycatcher (Empidonax minimus) and rose-breasted grosbeak (Pheucticus ludovicianus) from field data collected in northern hardwood forests of Michigan’s Upper Peninsula. We integrate these bird-forest structure relationships with a forest simulation model that couples a forest-gap tree regeneration submodel developed from our field data with the US Forest Service Forest Vegetation Simulator (Ontario variant). Our bird occupancy models are better than null models for all species, and indicate species-specific responses to management-related forest structure variables. When simulated over a century, higher overall tree regeneration densities and greater proportions of commercially high value, deer browse-preferred, canopy tree Acer saccharum (sugar maple) than low-value, browse-avoided subcanopy tree Ostrya virginiana (Ironwood) ensure conditions allowing larger harvests of merchantable timber and had greater impacts on bird occupancy probability change. Compared to full regeneration, no regeneration over 100 years reduces merchantable timber volumes by up to 25% and drives differences in bird occupancy probability change of up to 30%. We also find that harvest prescriptions can be tailored to affect both timber removal volumes and bird occupancy probability simultaneously, but only when regeneration is adequate. When regeneration is poor (e.g., 25% or less of trees succeed in regenerating), timber harvest prescriptions have a greater relative influence on bird species occupancy probabilities than on the volume of merchantable timber harvested. However, regeneration density and composition, particularly the density of Acer saccharum regenerating, have the greatest long-term effects on canopy bird occupancy probability. Our results imply that forest and wildlife managers need to work together to ensure tree regeneration density and composition are adequate for both timber production and the maintenance of habitat for avian species over the long-term. Where tree regeneration is currently poor (e.g., due to deer herbivory), forest and wildlife managers should pay particularly close attention to the long-term impacts of timber harvest prescriptions on bird species.

James D. A. Millington - One of the best experts on this subject based on the ideXlab platform.

  • modelling for forest management synergies and trade offs northern hardwood tree regeneration timber and deer
    Ecological Modelling, 2013
    Co-Authors: James D. A. Millington, Michael B Walters, Megan S. Matonis
    Abstract:

    In many managed forests, tree regeneration density and composition following timber harvest are highly variable. This variability is due to multiple environmental drivers – including browsing by herbivores such as deer, seed availability and physical characteristics of forest gaps and stands – many of which can be influenced by forest management. Identifying management actions that produce regeneration abundance and composition appropriate for the long-term sustainability of multiple forest values (e.g., timber, wildlife) is a difficult task. However, this task can be aided by simulation tools that improve understanding and enable evaluation of synergies and trade-offs between management actions for different resources. We present a forest tree regeneration, growth, and harvest simulation model developed with the express purpose of assisting managers to evaluate the impacts of timber and deer management on tree regeneration and forest dynamics in northern hardwood forests over long time periods under different scenarios. The model couples regeneration and deer density sub-models developed from empirical data with the Ontario variant of the US Forest Service individual-based forest growth model, Forest Vegetation Simulator. Our error analyses show that model output is robust given uncertainty in the sub-models. We investigate scenarios for timber and deer management actions in northern hardwood stands for 200 years. Results indicate that higher levels of mature Ironwood (Ostrya virginiana) removal and lower deer densities significantly increase sugar maple (Acer saccharum) regeneration success rates. Furthermore, our results show that although deer densities have an immediate and consistent negative impact on forest regeneration and timber through time, the non-removal of mature Ironwood trees has cumulative negative impacts due to feedbacks on competition between Ironwood and sugar maple. These results demonstrate the utility of the simulation model to managers for examining long-term impacts, synergies and trade-offs of multiple forest management actions.

  • combined long term effects of variable tree regeneration and timber management on forest songbirds and timber production
    Forest Ecology and Management, 2011
    Co-Authors: James D. A. Millington, Michael B Walters, Edward J Laurent, Megan S. Matonis, Kimberly R Hall
    Abstract:

    The structure of forest stands is an important determinant of habitat use by songbirds, including species of conservation concern. In this paper, we investigate the combined long-term impacts of variable tree regeneration and timber management on stand structure, songbird occupancy probabilities, and timber production in northern hardwood forests. We develop species-specific relationships between bird species occupancy and forest stand structure for canopy-dependent black-throated green warbler (Dendroica virens), eastern wood-pewee (Contopus virens), least flycatcher (Empidonax minimus) and rose-breasted grosbeak (Pheucticus ludovicianus) from field data collected in northern hardwood forests of Michigan’s Upper Peninsula. We integrate these bird-forest structure relationships with a forest simulation model that couples a forest-gap tree regeneration submodel developed from our field data with the US Forest Service Forest Vegetation Simulator (Ontario variant). Our bird occupancy models are better than null models for all species, and indicate species-specific responses to management-related forest structure variables. When simulated over a century, higher overall tree regeneration densities and greater proportions of commercially high value, deer browse-preferred, canopy tree Acer saccharum (sugar maple) than low-value, browse-avoided subcanopy tree Ostrya virginiana (Ironwood) ensure conditions allowing larger harvests of merchantable timber and had greater impacts on bird occupancy probability change. Compared to full regeneration, no regeneration over 100 years reduces merchantable timber volumes by up to 25% and drives differences in bird occupancy probability change of up to 30%. We also find that harvest prescriptions can be tailored to affect both timber removal volumes and bird occupancy probability simultaneously, but only when regeneration is adequate. When regeneration is poor (e.g., 25% or less of trees succeed in regenerating), timber harvest prescriptions have a greater relative influence on bird species occupancy probabilities than on the volume of merchantable timber harvested. However, regeneration density and composition, particularly the density of Acer saccharum regenerating, have the greatest long-term effects on canopy bird occupancy probability. Our results imply that forest and wildlife managers need to work together to ensure tree regeneration density and composition are adequate for both timber production and the maintenance of habitat for avian species over the long-term. Where tree regeneration is currently poor (e.g., due to deer herbivory), forest and wildlife managers should pay particularly close attention to the long-term impacts of timber harvest prescriptions on bird species.

Bambang Irawan - One of the best experts on this subject based on the ideXlab platform.

  • effects of indole acetic acid iaa and indole butyric acid iba to the growth and rooting of Ironwood eusideroxylon zwageri teijsm binn air layering
    Jurnal Manajemen Hutan Tropika (Journal of Tropical Forest Management), 2019
    Co-Authors: Bambang Irawan, Rike Puspitasari Tamin, Rizky Ayu Hardiyanti
    Abstract:

    Due to over exploitation, the population of Eusideroxylon zwageri is decreasing drastically. One simple technique to conserve the last remaining genetic resources of E. zwageri is by air layering. The experiment was divided into two. The experiment was conducted from July 2018 to February 2019. The first experiment was conducted using branches that grew from coppices while the second experiment using twigs that grew from normal adult trees. Randomized Block Design was applied with three replicates. The treatments were consisted of nine concentration of auxin namely 0 ppm of auxin; 1, 000 ppm; 1,500 ppm; 2,000 ppm and 2,500 ppm of IAA and 1,000 ppm; 2,000 ppm; 3,000 ppm and 4,000 ppm of IBA. The result of experiment shows that the IBA growth regulator seems to be more effective in regulating growth and rooting of E. zwageri air layering compared to IAA. Results for air layering which was taken from coppices revealed that 1,000 ppm of IBA obtained the best results. Air layering of branches taken from coppice is possible even without any additional growth regulator. While, air layering of twigs which was taken from normal trees revealed that the best treatment is 3,000 ppm of IBA.

  • Linking indigenous knowledge, plant morphology, and molecular differentiation: the case of Ironwood (Eusideroxylon zwageri Teijsm. et Binn.)
    Genetic Resources and Crop Evolution, 2016
    Co-Authors: Bambang Irawan, Franz Gruber, Reiner Finkeldey, Oliver Gailing
    Abstract:

    The analysis of indigenous knowledge, morphological observations, and molecular variation are valid approaches to study plant biodiversity. A combination of these complementary methods allows a better understanding of the diversity within Ironwood ( Eusideroxylon zwageri Teijsm. et Binn.), an endangered ‘wild’ tropical tree species, at molecular and important functional traits. Ironwood belongs to the Lauraceae family. It is one of the most important species for construction wood in Indonesia because it is not vulnerable to termites and other ubiquitous tropical wood-destroying insects and fungi. Due to over-exploitation, populations of Ironwood are decreasing and the species is included in the list of threatened tree species. Morphological variability of Ironwood has been discussed and studied since the middle of the 19th century. However there is no comprehensive taxonomic assessment to the present time. The variability is mostly recognized by local people based on bark, wood and fruit characteristics. The present study has been conducted to answer whether the variation that is recognized by local people has a genetic basis. AFLPs were chosen as molecular markers best suited for this study due their capacity to estimate genome-wide genetic diversity. Morphological structure assessment was conducted to confirm specific characteristics of each variety. The percentage of polymorphic fragments was 52 %. UPGMA cluster analysis showed that 98 % of individual Ironwood samples formed clusters according to their variety as recognized by local people. There was strong correspondence between clusters identified by AFLP analysis and morphological analyses.

  • soil properties and the abundace of Ironwood eusideroxylon zwageri teijsm binn varieties in jambi indonesia
    Jurnal Manajemen Hutan Tropika (Journal of Tropical Forest Management), 2015
    Co-Authors: Bambang Irawan
    Abstract:

    Two series of a study on the correlation between soil properties and distribution of Ironwood (Eusideroxylon zwageri Teijsm.& Binn.) varieties had been conducted in Senami, a natural forest stand, Jambi, Indonesia. The first was using purposive random sampling. The samples were taken from the locations where the E. zwageri varieties naturally grow in the depth of 0–30 cm and 30–60 cm. The number of composite samples was 18 which were analyzed for chemical soil properties. The second study was conducted using systematic sampling where 64 soil cores were collected from 3 different soil depths namely 0–20 cm, 20–40 cm, and 40–60 cm. The physical soil properties were analyzed from the 64 soil samples. The research results revealed that the drainage among E. zwageri varieties varied from poor conditions to moderate, while the bulk density was slightly different, from very low to low. The results also show that E. zwageri varieties are able to grow in almost any soil textures. There is no specific correlation between chemical soil properties and distribution of E. zwageri varieties. All varieties grow at almost the same condition of chemical soil properties except var. grandis.

  • soil properties and the abunda ce of Ironwood teijsm binn n varieties n jambi indonesia i
    2015
    Co-Authors: Bambang Irawan
    Abstract:

    Two series of a study on the correlation between soil properties and distribution of Ironwood (Eusideroxylon zwageri Teijsm.& Binn.) varieties had been conducted in Senami, a natural forest stand, Jambi, Indonesia. The first was using purposive random sampling. The samples were taken from the locations where the E. zwageri varieties naturally grow in the depth of 0-30 cm and 30-60 cm. The number of composite samples was 18 which were analyzed for chemical soil properties. The second study was conducted using systematic sampling where 64 soil cores were collected from different soil depths namely 0-20 cm, 20-40 cm and 40-60 cm. The physical soil properties were 3 , analyzed from the 64 soil samples. The research results revealed that the drainage among E. zwageri varieties varied from poor conditions to moderate, while the bulk density was slightly different, from very low to low. The results also show that E. zwageri varieties are able to grow in almost any soil textures. There is no specific correlation between chemical soil properties and distribution of E. zwageri varieties. All varieties grow at almost the same condition of chemical soil properties except var. grandis.

  • growth performance of one year old seedlings of Ironwood eusideroxylon zwageri teijsm binn varieties
    Jurnal Manajemen Hutan Tropika (Journal of Tropical Forest Management), 2012
    Co-Authors: Bambang Irawan
    Abstract:

    Four Eusideroxylon zwageri Teijsm. & Binn. varieties had been described. A study on growth performance of one-year old seedlings of E. zwageri varieties had been conducted to study the comparison of shoot growth performance and survival among E. zwageri varieties.  The varieties were exilis, grandis, ovoidus, and zwageri. The study was conducted in Jambi, Indonesia for one year using complete randomized design. Four E. zwageri varieties were used as factor with 6 replications. Each consists of 6 seedlings therefore, the total number of seedlings were 144.  The results showed that survival and shoot growth performance of E. zwageri seedlings were significantly different among varieties. Stem height of E. zwageri seedlings was significantly different among some varieties. The results related to stem diameter showed different characteristics among E. zwageri seedlings, zwageri variety had the biggest diameter. It was significantly different from ovoidus and exilis, but not significantly different from grandis. The differences among E. zwageri seedlings in shoot dry weight parameter were identical to the parameter of stem diameter. The lowest value of branch angle belonged to zwageri. Based on Duncan multiple range test, it was significantly different from other varieties except grandis. Generally, zwageri shows the best growth performance among seedlings of E. zwageri varieties.

Michael B Walters - One of the best experts on this subject based on the ideXlab platform.

  • modelling for forest management synergies and trade offs northern hardwood tree regeneration timber and deer
    Ecological Modelling, 2013
    Co-Authors: James D. A. Millington, Michael B Walters, Megan S. Matonis
    Abstract:

    In many managed forests, tree regeneration density and composition following timber harvest are highly variable. This variability is due to multiple environmental drivers – including browsing by herbivores such as deer, seed availability and physical characteristics of forest gaps and stands – many of which can be influenced by forest management. Identifying management actions that produce regeneration abundance and composition appropriate for the long-term sustainability of multiple forest values (e.g., timber, wildlife) is a difficult task. However, this task can be aided by simulation tools that improve understanding and enable evaluation of synergies and trade-offs between management actions for different resources. We present a forest tree regeneration, growth, and harvest simulation model developed with the express purpose of assisting managers to evaluate the impacts of timber and deer management on tree regeneration and forest dynamics in northern hardwood forests over long time periods under different scenarios. The model couples regeneration and deer density sub-models developed from empirical data with the Ontario variant of the US Forest Service individual-based forest growth model, Forest Vegetation Simulator. Our error analyses show that model output is robust given uncertainty in the sub-models. We investigate scenarios for timber and deer management actions in northern hardwood stands for 200 years. Results indicate that higher levels of mature Ironwood (Ostrya virginiana) removal and lower deer densities significantly increase sugar maple (Acer saccharum) regeneration success rates. Furthermore, our results show that although deer densities have an immediate and consistent negative impact on forest regeneration and timber through time, the non-removal of mature Ironwood trees has cumulative negative impacts due to feedbacks on competition between Ironwood and sugar maple. These results demonstrate the utility of the simulation model to managers for examining long-term impacts, synergies and trade-offs of multiple forest management actions.

  • combined long term effects of variable tree regeneration and timber management on forest songbirds and timber production
    Forest Ecology and Management, 2011
    Co-Authors: James D. A. Millington, Michael B Walters, Edward J Laurent, Megan S. Matonis, Kimberly R Hall
    Abstract:

    The structure of forest stands is an important determinant of habitat use by songbirds, including species of conservation concern. In this paper, we investigate the combined long-term impacts of variable tree regeneration and timber management on stand structure, songbird occupancy probabilities, and timber production in northern hardwood forests. We develop species-specific relationships between bird species occupancy and forest stand structure for canopy-dependent black-throated green warbler (Dendroica virens), eastern wood-pewee (Contopus virens), least flycatcher (Empidonax minimus) and rose-breasted grosbeak (Pheucticus ludovicianus) from field data collected in northern hardwood forests of Michigan’s Upper Peninsula. We integrate these bird-forest structure relationships with a forest simulation model that couples a forest-gap tree regeneration submodel developed from our field data with the US Forest Service Forest Vegetation Simulator (Ontario variant). Our bird occupancy models are better than null models for all species, and indicate species-specific responses to management-related forest structure variables. When simulated over a century, higher overall tree regeneration densities and greater proportions of commercially high value, deer browse-preferred, canopy tree Acer saccharum (sugar maple) than low-value, browse-avoided subcanopy tree Ostrya virginiana (Ironwood) ensure conditions allowing larger harvests of merchantable timber and had greater impacts on bird occupancy probability change. Compared to full regeneration, no regeneration over 100 years reduces merchantable timber volumes by up to 25% and drives differences in bird occupancy probability change of up to 30%. We also find that harvest prescriptions can be tailored to affect both timber removal volumes and bird occupancy probability simultaneously, but only when regeneration is adequate. When regeneration is poor (e.g., 25% or less of trees succeed in regenerating), timber harvest prescriptions have a greater relative influence on bird species occupancy probabilities than on the volume of merchantable timber harvested. However, regeneration density and composition, particularly the density of Acer saccharum regenerating, have the greatest long-term effects on canopy bird occupancy probability. Our results imply that forest and wildlife managers need to work together to ensure tree regeneration density and composition are adequate for both timber production and the maintenance of habitat for avian species over the long-term. Where tree regeneration is currently poor (e.g., due to deer herbivory), forest and wildlife managers should pay particularly close attention to the long-term impacts of timber harvest prescriptions on bird species.