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Michael S. Williams - One of the best experts on this subject based on the ideXlab platform.

  • A comprehensive comparison of Perpendicular Distance sampling methods for sampling downed coarse woody debris
    Forestry, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    Many new methods for sampling down coarse woody debris have been proposed in the last dozen or so years. One of the most promising in terms of field application, Perpendicular Distance sampling (PDS), has several variants that have been progressively introduced in the literature. In this study, we provide an overview of the different PDS variants and comprehensive comparison of their associated estimator performance. Additionally, two new variants and their estimators are introduced to the existing pool. Simulations are used to determine the efficiency of competing protocols and associated estimators. The simulation results corroborate the theoreticalunbiasednessoftheestimatorsforPDSinallforms.Inaddition,whilethereissomedifferenceinvariance among the protocols, the overall difference is small, and depends on the attribute to be estimated. Therefore, the choice of which PDS variant to use in field applications will depend on the field conditions and attributes to be estimated.

  • Distance-limited Perpendicular Distance sampling for coarse woody debris: theory and field results
    Forestry, 2012
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Steven S. Roberge, Robert S Kenning
    Abstract:

    Coarse woody debris (CWD) has been identified as an important component in many forest ecosystem processes. Perpendicular Distance sampling (PDS) is one of the several efficient new methods that have been proposed for CWD inventory. One drawback of PDS is that the maximum search Distance can be very large, especially if CWD diameters are large or the volume factor chosen is small. Here, we propose a modified method, which we call Distance-limited PDS, that addresses this limitation. We describe the field procedures, develop new a new estimator, and provide a proof of unbiasedness of that estimator. The new method is compared with line intersect sampling (LIS) and PDS in a field trial in the northeastern United States. The results of the field trial show that this new method requires as little as 1/10 the sampling effort of LIS in order to achieve comparable variance of the estimates.

  • A Distance limited method for sampling downed coarse woody debris
    Forest Ecology and Management, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    A new sampling method for down coarse woody debris is proposed based on limiting the Perpendicular Distance from individual pieces to a randomly chosen sample point. Two approaches are presented that allow different protocols to be used to determine field measurements; estimators for each protocol are also developed. Both protocols are compared via simulation against existing sampling methods that are closely related in terms of theory and field implementation. The new method performed well in comparison to both fixed-area plot and Perpendicular Distance sampling, and may provide some simplifications in operational field use.

  • Simultaneous unbiased estimates of multiple downed wood attributes in Perpendicular Distance sampling
    Canadian Journal of Forest Research, 2008
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Harry T. Valentine
    Abstract:

    Perpendicular Distance sampling (PDS) is a fast probability-proportional-to-size method for inventory of downed wood. However, previous development of PDS had limited the method to estimating only one variable (such as volume per hectare, or surface area per hectare) at a time. Here, we develop a general design-unbiased estimator for PDS. We then show how that estimator can be used to develop simple measurement protocols that allow simultaneous, unbiased estimation of multiple downed wood variables, including logs per hectare, length of logs per hectare, surface area or area coverage per hectare, and volume per hectare.

  • Estimating the carbon in coarse woody debris with Perpendicular Distance sampling. Chapter 6
    2008
    Co-Authors: Harry T. Valentine, Mark J. Ducey, Timothy G. Gregoire, Jeffrey H. Gove, Michael S. Williams
    Abstract:

    Perpendicular Distance sampling (PDS) is a design for sampling the population of pieces of coarse woody debris (logs) in a forested tract. In application, logs are selected at sample points with probability proportional to volume. Consequently, aggregate log volume per unit land area can be estimated from tallies of logs at sample points. In this chapter we provide protocols and formulae for estimating the carbon in coarse woody debris with PDS. We also provide formulae for estimating components of change in the log population between two points in time.

Jeffrey H. Gove - One of the best experts on this subject based on the ideXlab platform.

  • A comprehensive comparison of Perpendicular Distance sampling methods for sampling downed coarse woody debris
    Forestry, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    Many new methods for sampling down coarse woody debris have been proposed in the last dozen or so years. One of the most promising in terms of field application, Perpendicular Distance sampling (PDS), has several variants that have been progressively introduced in the literature. In this study, we provide an overview of the different PDS variants and comprehensive comparison of their associated estimator performance. Additionally, two new variants and their estimators are introduced to the existing pool. Simulations are used to determine the efficiency of competing protocols and associated estimators. The simulation results corroborate the theoreticalunbiasednessoftheestimatorsforPDSinallforms.Inaddition,whilethereissomedifferenceinvariance among the protocols, the overall difference is small, and depends on the attribute to be estimated. Therefore, the choice of which PDS variant to use in field applications will depend on the field conditions and attributes to be estimated.

  • Distance-limited Perpendicular Distance sampling for coarse woody debris: theory and field results
    Forestry, 2012
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Steven S. Roberge, Robert S Kenning
    Abstract:

    Coarse woody debris (CWD) has been identified as an important component in many forest ecosystem processes. Perpendicular Distance sampling (PDS) is one of the several efficient new methods that have been proposed for CWD inventory. One drawback of PDS is that the maximum search Distance can be very large, especially if CWD diameters are large or the volume factor chosen is small. Here, we propose a modified method, which we call Distance-limited PDS, that addresses this limitation. We describe the field procedures, develop new a new estimator, and provide a proof of unbiasedness of that estimator. The new method is compared with line intersect sampling (LIS) and PDS in a field trial in the northeastern United States. The results of the field trial show that this new method requires as little as 1/10 the sampling effort of LIS in order to achieve comparable variance of the estimates.

  • A Distance limited method for sampling downed coarse woody debris
    Forest Ecology and Management, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    A new sampling method for down coarse woody debris is proposed based on limiting the Perpendicular Distance from individual pieces to a randomly chosen sample point. Two approaches are presented that allow different protocols to be used to determine field measurements; estimators for each protocol are also developed. Both protocols are compared via simulation against existing sampling methods that are closely related in terms of theory and field implementation. The new method performed well in comparison to both fixed-area plot and Perpendicular Distance sampling, and may provide some simplifications in operational field use.

  • Simultaneous unbiased estimates of multiple downed wood attributes in Perpendicular Distance sampling
    Canadian Journal of Forest Research, 2008
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Harry T. Valentine
    Abstract:

    Perpendicular Distance sampling (PDS) is a fast probability-proportional-to-size method for inventory of downed wood. However, previous development of PDS had limited the method to estimating only one variable (such as volume per hectare, or surface area per hectare) at a time. Here, we develop a general design-unbiased estimator for PDS. We then show how that estimator can be used to develop simple measurement protocols that allow simultaneous, unbiased estimation of multiple downed wood variables, including logs per hectare, length of logs per hectare, surface area or area coverage per hectare, and volume per hectare.

  • Estimating the carbon in coarse woody debris with Perpendicular Distance sampling. Chapter 6
    2008
    Co-Authors: Harry T. Valentine, Mark J. Ducey, Timothy G. Gregoire, Jeffrey H. Gove, Michael S. Williams
    Abstract:

    Perpendicular Distance sampling (PDS) is a design for sampling the population of pieces of coarse woody debris (logs) in a forested tract. In application, logs are selected at sample points with probability proportional to volume. Consequently, aggregate log volume per unit land area can be estimated from tallies of logs at sample points. In this chapter we provide protocols and formulae for estimating the carbon in coarse woody debris with PDS. We also provide formulae for estimating components of change in the log population between two points in time.

Mark J. Ducey - One of the best experts on this subject based on the ideXlab platform.

  • A comprehensive comparison of Perpendicular Distance sampling methods for sampling downed coarse woody debris
    Forestry, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    Many new methods for sampling down coarse woody debris have been proposed in the last dozen or so years. One of the most promising in terms of field application, Perpendicular Distance sampling (PDS), has several variants that have been progressively introduced in the literature. In this study, we provide an overview of the different PDS variants and comprehensive comparison of their associated estimator performance. Additionally, two new variants and their estimators are introduced to the existing pool. Simulations are used to determine the efficiency of competing protocols and associated estimators. The simulation results corroborate the theoreticalunbiasednessoftheestimatorsforPDSinallforms.Inaddition,whilethereissomedifferenceinvariance among the protocols, the overall difference is small, and depends on the attribute to be estimated. Therefore, the choice of which PDS variant to use in field applications will depend on the field conditions and attributes to be estimated.

  • Distance-limited Perpendicular Distance sampling for coarse woody debris: theory and field results
    Forestry, 2012
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Steven S. Roberge, Robert S Kenning
    Abstract:

    Coarse woody debris (CWD) has been identified as an important component in many forest ecosystem processes. Perpendicular Distance sampling (PDS) is one of the several efficient new methods that have been proposed for CWD inventory. One drawback of PDS is that the maximum search Distance can be very large, especially if CWD diameters are large or the volume factor chosen is small. Here, we propose a modified method, which we call Distance-limited PDS, that addresses this limitation. We describe the field procedures, develop new a new estimator, and provide a proof of unbiasedness of that estimator. The new method is compared with line intersect sampling (LIS) and PDS in a field trial in the northeastern United States. The results of the field trial show that this new method requires as little as 1/10 the sampling effort of LIS in order to achieve comparable variance of the estimates.

  • A Distance limited method for sampling downed coarse woody debris
    Forest Ecology and Management, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    A new sampling method for down coarse woody debris is proposed based on limiting the Perpendicular Distance from individual pieces to a randomly chosen sample point. Two approaches are presented that allow different protocols to be used to determine field measurements; estimators for each protocol are also developed. Both protocols are compared via simulation against existing sampling methods that are closely related in terms of theory and field implementation. The new method performed well in comparison to both fixed-area plot and Perpendicular Distance sampling, and may provide some simplifications in operational field use.

  • Simultaneous unbiased estimates of multiple downed wood attributes in Perpendicular Distance sampling
    Canadian Journal of Forest Research, 2008
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Harry T. Valentine
    Abstract:

    Perpendicular Distance sampling (PDS) is a fast probability-proportional-to-size method for inventory of downed wood. However, previous development of PDS had limited the method to estimating only one variable (such as volume per hectare, or surface area per hectare) at a time. Here, we develop a general design-unbiased estimator for PDS. We then show how that estimator can be used to develop simple measurement protocols that allow simultaneous, unbiased estimation of multiple downed wood variables, including logs per hectare, length of logs per hectare, surface area or area coverage per hectare, and volume per hectare.

  • Estimating the carbon in coarse woody debris with Perpendicular Distance sampling. Chapter 6
    2008
    Co-Authors: Harry T. Valentine, Mark J. Ducey, Timothy G. Gregoire, Jeffrey H. Gove, Michael S. Williams
    Abstract:

    Perpendicular Distance sampling (PDS) is a design for sampling the population of pieces of coarse woody debris (logs) in a forested tract. In application, logs are selected at sample points with probability proportional to volume. Consequently, aggregate log volume per unit land area can be estimated from tallies of logs at sample points. In this chapter we provide protocols and formulae for estimating the carbon in coarse woody debris with PDS. We also provide formulae for estimating components of change in the log population between two points in time.

Harry T. Valentine - One of the best experts on this subject based on the ideXlab platform.

  • A comprehensive comparison of Perpendicular Distance sampling methods for sampling downed coarse woody debris
    Forestry, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    Many new methods for sampling down coarse woody debris have been proposed in the last dozen or so years. One of the most promising in terms of field application, Perpendicular Distance sampling (PDS), has several variants that have been progressively introduced in the literature. In this study, we provide an overview of the different PDS variants and comprehensive comparison of their associated estimator performance. Additionally, two new variants and their estimators are introduced to the existing pool. Simulations are used to determine the efficiency of competing protocols and associated estimators. The simulation results corroborate the theoreticalunbiasednessoftheestimatorsforPDSinallforms.Inaddition,whilethereissomedifferenceinvariance among the protocols, the overall difference is small, and depends on the attribute to be estimated. Therefore, the choice of which PDS variant to use in field applications will depend on the field conditions and attributes to be estimated.

  • A Distance limited method for sampling downed coarse woody debris
    Forest Ecology and Management, 2012
    Co-Authors: Jeffrey H. Gove, Mark J. Ducey, Harry T. Valentine, Michael S. Williams
    Abstract:

    A new sampling method for down coarse woody debris is proposed based on limiting the Perpendicular Distance from individual pieces to a randomly chosen sample point. Two approaches are presented that allow different protocols to be used to determine field measurements; estimators for each protocol are also developed. Both protocols are compared via simulation against existing sampling methods that are closely related in terms of theory and field implementation. The new method performed well in comparison to both fixed-area plot and Perpendicular Distance sampling, and may provide some simplifications in operational field use.

  • Simultaneous unbiased estimates of multiple downed wood attributes in Perpendicular Distance sampling
    Canadian Journal of Forest Research, 2008
    Co-Authors: Mark J. Ducey, Michael S. Williams, Jeffrey H. Gove, Harry T. Valentine
    Abstract:

    Perpendicular Distance sampling (PDS) is a fast probability-proportional-to-size method for inventory of downed wood. However, previous development of PDS had limited the method to estimating only one variable (such as volume per hectare, or surface area per hectare) at a time. Here, we develop a general design-unbiased estimator for PDS. We then show how that estimator can be used to develop simple measurement protocols that allow simultaneous, unbiased estimation of multiple downed wood variables, including logs per hectare, length of logs per hectare, surface area or area coverage per hectare, and volume per hectare.

  • Estimating the carbon in coarse woody debris with Perpendicular Distance sampling. Chapter 6
    2008
    Co-Authors: Harry T. Valentine, Mark J. Ducey, Timothy G. Gregoire, Jeffrey H. Gove, Michael S. Williams
    Abstract:

    Perpendicular Distance sampling (PDS) is a design for sampling the population of pieces of coarse woody debris (logs) in a forested tract. In application, logs are selected at sample points with probability proportional to volume. Consequently, aggregate log volume per unit land area can be estimated from tallies of logs at sample points. In this chapter we provide protocols and formulae for estimating the carbon in coarse woody debris with PDS. We also provide formulae for estimating components of change in the log population between two points in time.

  • Additional results for Perpendicular Distance sampling
    Canadian Journal of Forest Research, 2005
    Co-Authors: Michael S. Williams, Harry T. Valentine, Jeffery H. Gove, Mark J. Ducey
    Abstract:

    Over the last decade a number of new methods have been proposed to sample coarse woody debris. Of the new methods, both field trials and computer simulations suggest that Perpendicular Distance sampling is often the most efficient method for estimating the volume and surface area of coarse woody debris. As with any new sampling technique, further research and field testing are required to address some of the practical problems associated with the implementation of Perpendicular Distance sampling. This paper provides further results associated with the sampling of curved and multistemmed logs and field techniques for both slope correction and the measurement of elevated logs.

Petropoulos P. - One of the best experts on this subject based on the ideXlab platform.