A method to assess the performance of growth intercept models in British Columbia

2001 ◽  
Vol 77 (3) ◽  
pp. 491-499 ◽  
Author(s):  
Gordon D. Nigh ◽  
Patrick J. Martin
Keyword(s):  
British Columbia ◽  
Measurement Errors ◽  
Sampling Error ◽  
Site Index ◽  
Model Error ◽  
Good Precision ◽  
Interior Spruce ◽  
Validation Procedure ◽  
Growth Intercept ◽  
The Impact

An active program of developing growth intercept models in British Columbia is underway. In lieu of a proper validation procedure, we devised a method of assessing the growth intercept models, which we describe and demonstrate for interior spruce. Four sources of error in the site index predictions of the growth intercept models are examined: measurement, sampling, model, and application error. The impact of the measurement errors tend to be intolerably large at young ages, decreasing to acceptable levels as the trees near the index age. Sampling error was small in our example. The tested models were unbiased and have good precision. An analysis of the application error indicated that the growth intercept models may underestimate site index. Key words: Application bias, measurement error, model error, sampling error, spruce, validation

scholarly journals Juvenile Height Development in Interior Spruce Stands of British Columbia

2000 ◽  
Vol 15 (3) ◽  
pp. 117-121 ◽  
Author(s):  
Gordon D. Nigh ◽  
Bobby A. Love
Keyword(s):  
Decision Making ◽  
British Columbia ◽  
Site Index ◽  
Timber Supply ◽  
Breast Height ◽  
Forest Region ◽  
Interior Spruce ◽  
Spruce Stands ◽  
Age Model ◽  
Height Model

Abstract Good estimates of juvenile heights are important for silviculture and timber supply decision-making. These height estimates are particularly important for estimating the number of years it takes a stand to reach green-up and breast height. Thirty-nine 0.04 ha plots were established in managed juvenile stands of interior spruce in the Prince Rupert Forest Region. Four sample trees in each plot were split longitudinally and height-age data were obtained from the exposed pith nodes or branch whorls. The height-age data were fit to a combined exponential and power function to create a juvenile height model for interior spruce. This model is a function of age and site index. Years to breast height and green-up age models were developed with data generated from the juvenile height model. Forecasts from these models indicate that the time to reach breast height and green-up age is less than previously expected. The juvenile height model, years to breast height model, and green-up age model should be used for site indices above 14.2 m. In addition, the height model should only be used up to total age 20. West. J. Appl. For. 15(3):117-121.

scholarly journals A system for estimating height and site index of western hemlock in the interior of British Columbia

1998 ◽  
Vol 74 (4) ◽  
pp. 588-596 ◽  
Author(s):  
Gordon D. Nigh
Keyword(s):  
British Columbia ◽  
Site Index ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Index Model ◽  
Breast Height ◽  
Age Model ◽  
Site Index Model ◽  
Growth Intercept ◽  
Height Model

The focus of recent site productivity research in British Columbia has been to develop height-breast height age, growth intercept, and ecosystem-site index models. These models, together with a years-to-breast-height model, form a system for estimating site index and height. This system is described for western hemlock (Tsuga heterophylla (Raf.) Sarg.) in the interior of British Columbia. Forty-four western hemlock stem analysis plots were used in the construction of this system. As there are three models for estimating site index, the appropriate model for a given stand depends largely on the stand condition and the precision of the models. A graph of model precision against breast height age gives some assistance in deciding which model should be used to estimate site index. Key words: western hemlock, site index, height-age model, growth intercept model, years-to-breast-height model, ecosystem-site index model, model precision

scholarly journals Preliminary Evaluation of the Error Budgets in the TALIS Measurements and Their Impact on the Retrievals

2020 ◽  
Vol 12 (3) ◽  
pp. 468 ◽  
Author(s):  
Wenyu Wang ◽  
Zhenzhan Wang ◽  
Yongqiang Duan
Keyword(s):  
Measurement Errors ◽  
Chemical Constituents ◽  
A Priori ◽  
Local Oscillator ◽  
Antenna Pattern ◽  
Preliminary Evaluation ◽  
Good Precision ◽  
Science Center ◽  
The Impact ◽  
Hot Target

The THz Atmospheric Limb Sounder (TALIS) is a Chinese sub-millimeter limb sounder being designed by National Space Science Center of the Chinese Academy of Sciences to measure the temperature and chemical constituents vertically in the middle and upper atmosphere, with good precision and vertical resolution. This paper presents a simulation study that assesses the measurement errors and their impacts on the retrievals. Three error sources, including instrument uncertainties, calibration errors and a priori errors, are considered. The sideband weight uncertainty, the local oscillator, the pointing angle offsets and the measurement noise (NEDT), are considered as instrument uncertainties. Calibration errors consist of the hot target offset, the nonlinearity residual of the two-point calibration, use of the Rayleigh–Jeans (R–J) approximation and the choice of the antenna pattern. A priori profile errors of temperature, pressure and species are also considered. The results suggest that the antenna pattern mainly affects the retrievals in the troposphere. The NEDT is a major error source affecting all of the retrievals. The R–J approximation has a great impact upon the retrievals at 643 GHz, and should not be used. The local oscillator offset leads to an obvious error above 50 km. The effect of nonlinearity residuals cannot be neglected above 70 km. The impact of the sideband weight uncertainty and the hot target offset are relatively small. The pointing and the a priori errors can be neglected in most observation regions.

Assessing the impact of current and projected climates on Douglas-Fir productivity in British Columbia, Canada, using a process-based model (3-PG)

2010 ◽  
Vol 40 (3) ◽  
pp. 511-524 ◽  
Author(s):  
Nicholas C. Coops ◽  
Robbie A. Hember ◽  
Richard H. Waring
Keyword(s):  
British Columbia ◽  
Pseudotsuga Menziesii ◽  
Site Index ◽  
Douglas Fir ◽  
Climatic Variation ◽  
Climate Forecasts ◽  
Fine Spatial Resolution ◽  
Viable Approach ◽  
The Impact ◽  
Process Based Models

Predicted climate change is expected to significantly affect tree growth in many areas. We used a process-based model (Physiological Principles for Predicting Growth, 3-PG) to evaluate how climatic variation might alter growth of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco and Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) across biogeoclimatic zones in British Columbia. The results indicate that there will be significant changes in site index (defined as the height (in metres) of dominant trees at 50 years) over this century. In the interior, a reduction in site index is likely, particularly in stands with mid-range values of site index (25–30 m), with many of the interior bioecoclimatic zones predicted to experience a gradual mean decrease in site index by up to 10%. Individual sites may decrease by as much as 40% from current values. In contrast, site index along the coast overall is predicted to increase to a maximum of 43 m by 2080. In the Coastal Western Hemlock zone, however, mean site index is likely to increase from 26 m to only 34 m. We believe that combining process-based models with fine-spatial resolution climate forecasts offers a viable approach to assess future changes in forest productivity.

A height-growth and site-index model for interior spruce in the Sub-Boreal Spruce biogeoclimatic zone of British Columbia

2010 ◽  
Vol 40 (6) ◽  
pp. 1175-1183 ◽  
Author(s):  
Zhengjun Hu ◽  
Oscar García
Keyword(s):  
British Columbia ◽  
Full Range ◽  
Site Index ◽  
Height Growth ◽  
Site Quality ◽  
Growth Equation ◽  
Index Model ◽  
Interior Spruce ◽  
Height Prediction ◽  
Site Index Model

Height growth was modelled for spruce-dominated, even-aged stands in the Sub-Boreal Spruce biogeoclimatic zone of British Columbia, Canada, using both stem analysis (SA) and permanent sample plot (PSP) data. The model is based on a stochastic differential equation (SDE) formulation of the Bertalanffy–Richards growth equation. The SDE approach accounts for serial correlation and heterogeneous variance and makes hypothesis testing possible. Statistically significant differences in height–age trends between SA and PSP data were found that may be attributed to bias caused by dominance changes in SA trees. Error structure in SA and PSPs was also significantly different. Combining both data sources in a way that respects these different error structures reduced bias and increased precision. Four parametrizations were tested; the best was a polymorphic version. The final model fit the data well with no appreciable bias over the full range of ages and site qualities. The currently used spruce site-index model was found to underestimate growth and overestimate site index in young stands. The new model can be recommended for height prediction and site-quality assessment in interior spruce.

scholarly journals Incidence of diabetes mellitus among people living with and without HIV in British Columbia, Canada between 2001 and 2013: a longitudinal population-based cohort study

BMJ Open ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. e048744
Author(s):  
Andreea Bratu ◽  
Taylor McLinden ◽  
Katherine Kooij ◽  
Monica Ye ◽  
Jenny Li ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
British Columbia ◽  
Cohort Study ◽  
Population Based ◽  
Incidence Rates ◽  
Trend Test ◽  
People Living With Hiv ◽  
Age Related ◽  
Hiv Serostatus ◽  
The Impact

IntroductionPeople living with HIV (PLHIV) are increasingly at risk of age-related comorbidities such as diabetes mellitus (DM). While DM is associated with elevated mortality and morbidity, understanding of DM among PLHIV is limited. We assessed the incidence of DM among people living with and without HIV in British Columbia (BC), Canada, during 2001–2013.MethodsWe used longitudinal data from a population-based cohort study linking clinical data and administrative health data. We included PLHIV who were antiretroviral therapy (ART) naïve at baseline, and 1:5 age-sex-matched persons without HIV. All participants had ≥5 years of historic data pre-baseline and ≥1 year(s) of follow-up. DM was identified using the BC Ministry of Health’s definitions applied to hospitalisation, physician billing and drug dispensation datasets. Incident DM was identified using a 5-year run-in period. In addition to unadjusted incidence rates (IRs), we estimated adjusted incidence rate ratios (IRR) using Poisson regression and assessed annual trends in DM IRs per 1000 person years (PYs) between 2001 and 2013.ResultsA total of 129 PLHIV and 636 individuals without HIV developed DM over 17 529 PYs and 88,672 PYs, respectively. The unadjusted IRs of DM per 1000 PYs were 7.4 (95% CI 6.2 to 8.8) among PLHIV and 7.2 (95% CI 6.6 to 7.8) for individuals without HIV. After adjustment for confounding, HIV serostatus was not associated with DM incidence (adjusted IRR: 1.03, 95% CI 0.83 to 1.27). DM incidence did not increase over time among PLHIV (Kendall trend test: p=0.9369), but it increased among persons without HIV between 2001 and 2013 (p=0.0136).ConclusionsAfter adjustment, HIV serostatus was not associated with incidence of DM, between 2001 and 2013. Future studies should investigate the impact of ART on mitigating the potential risk of DM among PLHIV.

scholarly journals Lipemia in the Plasma Sample Affects Fentanyl Measurements by Means of HPLC-MS2 after Liquid-Liquid Extraction

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4514
Author(s):  
Marta Tikhomirov ◽  
Tomasz Śniegocki ◽  
Błażej Poźniak
Keyword(s):  
Forensic Toxicology ◽  
Liquid Extraction ◽  
Rabbit Plasma ◽  
Chromatography Method ◽  
Method Performance ◽  
Liquid Liquid Extraction ◽  
Normal Plasma ◽  
Validation Procedure ◽  
Liquid Chromatography Method ◽  
The Impact

Examination of fentanyl levels is frequently performed in certain scientific evaluations and forensic toxicology. It often involves the collection of very variable blood samples, including lipemic plasma or serum. To date, many works have reported the methods for fentanyl detection, but none of them have provided information about the impact on the assay performance caused by an excessive amount of lipids. This aspect may be, however, very important for highly lipophilic drugs like fentanyl. To address this issue, we developed the liquid chromatography method with mass spectrometry detection and utilized it to investigate the impact of lipids presence in rabbit plasma on the analytical method performance and validation. The validation procedure, conducted for normal plasma and lipemic plasma separately, resulted in good selectivity, sensitivity and linearity. The limits of detection and quantification were comparable between the two matrices, being slightly lower in normal plasma (0.005 and 0.015 µg/L) than in lipemic plasma (0.008 and 0.020 µg/L). Liquid–liquid extraction provided a low matrix effect regardless of the lipid levels in the samples (<10%), but pronounced differences were found in the recovery and accuracy. In the normal plasma, this parameter was stable and high (around 100%), but in the lipemic matrix, much more variable and less efficient results were obtained. Nevertheless, this difference had no impact on repeatability and reproducibility. In the present work, we provided reliable, convenient and sensitive method for fentanyl detection in the normal and lipemic rabbit plasma. However, construction of two separate validation curves was necessary to provide adequate results since the liquid-liquid extraction was utilized. Therefore, special attention should be paid during fentanyl quantification that involves lipemic plasma samples purified by this technique.

scholarly journals Forest Road Status Assessment Using Airborne Laser Scanning

2019 ◽  
Vol 66 (4) ◽  
pp. 501-508 ◽  
Author(s):  
Katalin Waga ◽  
Piotr Tompalski ◽  
Nicholas C Coops ◽  
Joanne C White ◽  
Michael A Wulder ◽  
...  
Keyword(s):  
British Columbia ◽  
Laser Scanning ◽  
Airborne Laser Scanning ◽  
Height Distribution ◽  
Forest Roads ◽  
The Road ◽  
Airborne Laser ◽  
Independent Field ◽  
The Status ◽  
The Impact

Abstract Forest roads allow access for silvicultural operations, harvesting, recreational activities, wildlife management, and fire suppression. In British Columbia, Canada, roads that are no longer required must be deactivated (temporarily, semipermanently, or permanently) in order to minimize the impact on the overall forested ecosystem. However, the remoteness and size of the road network present challenges for monitoring. Our aim was to examine the utility of airborne laser scanning data to assess the status and quality of forest roads across 52,000 hectares of coastal forest in British Columbia. Within the forest estate, roads can be active or deactivated, or have an unknown status. We classified road segments based on the vegetation growth on the road surface, and edges, by classifying the height distribution of airborne laser scanning returns within each road segment into four groups: no vegetation, minor vegetation, dense understory vegetation, and dense overstory vegetation. Validation indicated that 73 percent of roads were classified correctly when compared to independent field observations. The majority were classified as active roads with no vegetation or deactivated with dense vegetation. The approach presented herein can aid forest managers in verifying the status of the roads in their management area, especially in remote areas where field assessments are costly and time-consuming.

Sign in / Sign up

Export Citation Format

Share Document