On the efficiency of line intersect distance sampling

2010 ◽  
Vol 40 (6) ◽  
pp. 1086-1094 ◽  
Author(s):  
David L.R. Affleck
Keyword(s):  
Cross Section ◽  
Woody Debris ◽  
Distance Sampling ◽  
Field Trials ◽  
Sampling Strategies ◽  
Volume Factor ◽  
Time Differential ◽  
Central Interest ◽  
Factor Design ◽  
Volume Estimates

Sampling strategies commonly used for coarse woody debris (CWD) inventories, including line intersect sampling (LIS), typically require large sample sizes to estimate aggregate volume with reasonable precision. Line intersect distance sampling (LIDS) is a recently developed strategy based on a probability proportional-to-volume design and a linear sampling unit. In principle, the design augments the precision of volume estimators by increasing the intensity with which bulkier particles are sampled, while the transect-based protocol facilitates the search for qualifying particles. This study reports on the relative performances of LIDS and LIS in seven stands in Montana, USA. Particles selected by LIDS were consistently less numerous but larger in cross section than those selected at the same locations by LIS. In timed field trials, LIDS required more time than LIS, but CWD volume estimates from LIDS were generally more precise, more than offsetting the time differential. Conversely, aggregate length and abundance of CWD were generally estimated more efficiently with LIS. Results suggest that LIDS permits more efficient use of survey resources than LIS where CWD inventories focus on parameters relating to volume, biomass, or carbon. However, the constant volume factor design of LIDS is not advantageous where CWD frequency is of central interest.

Additional results for perpendicular distance sampling

2005 ◽  
Vol 35 (4) ◽  
pp. 961-966 ◽  
Author(s):  
M S Williams ◽  
H T Valentine ◽  
J H Gove ◽  
M J Ducey
Keyword(s):  
Coarse Woody Debris ◽  
Woody Debris ◽  
Distance Sampling ◽  
Sampling Technique ◽  
Field Testing ◽  
Field Trials ◽  
Field Techniques ◽  
New Methods ◽  
Perpendicular Distance ◽  
Slope Correction

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.

scholarly journals How to Evaluate Downed Fine Woody Debris Including Logging Residues?

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 881
Author(s):  
Nathalie Korboulewsky ◽  
Isabelle Bilger ◽  
Abdelwahab Bessaad
Keyword(s):  
Wood Density ◽  
Stock Assessment ◽  
Woody Debris ◽  
Diameter Class ◽  
Density Measurements ◽  
Fine Woody Debris ◽  
Forest Inventories ◽  
Test Zone ◽  
Fixed Area ◽  
Volume Estimates

Volume or biomass estimates of downed woody debris are crucial for numerous applications such as forest carbon stock assessment, biodiversity assessments, and more recently for environmental evaluations of biofuel harvesting practices. Both fixed-area sampling (FAS) and line-intersect sampling (LIS) are used in forest inventories and ecological studies because they are unbiased and accurate methods. Nevertheless, most studies and inventories take into account only coarse woody debris (CWD, >10 cm in diameter), although fine woody debris (FWD) can account for a large part of the total downed biomass. We compared the LIS and FAS methods for FWD volume or biomass estimates and evaluated the influence of diameter and wood density measurements, plot number and size. We used a Test Zone (a defined surface area where a complete inventory was carried out, in addition to FAS and LIS), a Pilot Stand (a forest stand where both LIS and FAS methods were applied) and results from 10 field inventories in deciduous temperate forest stands with various conditions and amounts of FWD. Both methods, FAS and LIS, provided accurate (in trueness and precision) volume estimates, but LIS proved to be the more efficient. Diameter measurement was the main source of error: using the mean diameter, even by diameter class, led to an error for volume estimates of around 35%. On the contrary, wood density measurements can be simplified without much influence on the accuracy of biomass estimates (use of mean density by diameter class). We show that the length and number of transects greatly influences the estimates, and that it is better to apply more, shorter transects than fewer, longer ones. Finally, we determined the optimal methodology and propose a simplification of some measurements to obtain the best time-precision trade-off for FWD inventories at the stand level.

scholarly journals Distance-limited perpendicular distance sampling for coarse woody debris: theory and field results

2012 ◽  
Vol 86 (1) ◽  
pp. 119-128 ◽  
Author(s):  
M. J. Ducey ◽  
M. S. Williams ◽  
J. H. Gove ◽  
S. Roberge ◽  
R. S. Kenning
Keyword(s):  
Coarse Woody Debris ◽  
Woody Debris ◽  
Distance Sampling ◽  
Perpendicular Distance

Estimating the Carbon in Coarse Woody Debris with Perpendicular Distance Sampling

2008 ◽  
pp. 73-87 ◽  
Author(s):  
Harry T. Valentine ◽  
Jeffrey H. Gove ◽  
Mark J. Ducey ◽  
Timothy G. Gregoire ◽  
Michael S. Williams
Keyword(s):  
Coarse Woody Debris ◽  
Woody Debris ◽  
Distance Sampling ◽  
Perpendicular Distance

Assessing surface area of coarse woody debris with line intersect and perpendicular distance sampling

2005 ◽  
Vol 35 (4) ◽  
pp. 949-960 ◽  
Author(s):  
M S Williams ◽  
M J Ducey ◽  
J H Gove
Keyword(s):  
Surface Area ◽  
Coarse Woody Debris ◽  
Mean Squared Error ◽  
Woody Debris ◽  
Distance Sampling ◽  
Field Work ◽  
Single Measurement ◽  
Stem Form ◽  
Important Conclusion ◽  
Perpendicular Distance

Coarse woody debris (CWD) plays an important role in many terrestrial and aquatic ecosystem processes. In recent years, a number of new methods have been proposed to sample CWD. Of these methods, perpendicular distance sampling (PDS) is one of the most efficient methods for estimating CWD volume in terms of both estimator variance and field effort. This study extends the results for PDS to the estimation of the surface area of CWD. The PDS estimator is also compared to two line intersect sampling (LIS) estimators, where one of the LIS estimators requires the measurement of surface area on each log and the other estimates surface area using a single measurement of log circumference at the point of intersection between the log and the line. The first estimator approximates the true surface area by assuming either a conic or parabolic stem form and requires measurements of the end diameters of each log, which is more time consuming than a single measurement. The performance of the three estimators was compared using a computer simulation. The results of the simulation indicate that, given the same number of pieces of CWD sampled at each point, equal variances can be achieved with PDS using sample sizes that range from about 10% to in excess of 100% the size of a comparable LIS estimator. When the LIS estimators were compared, the estimator that required the measurement of surface area was only about 3%–6% more efficient than the alternative estimator, but the bias associated with assuming a conic or parabolic stem form ranged from roughly 5% to 15%. We conclude that PDS will generally outperform either of the LIS estimators. Another important conclusion is that the LIS estimator based on a measured surface area is likely to have a higher mean squared error than an LIS estimator that employs a single measurement of circumference. Thus, LIS sampling strategies that require the least amount of field work will often have the smallest mean square error.

Perpendicular distance sampling: an alternative method for sampling downed coarse woody debris

2003 ◽  
Vol 33 (8) ◽  
pp. 1564-1579 ◽  
Author(s):  
M S Williams ◽  
J H Gove
Keyword(s):  
Coarse Woody Debris ◽  
Woody Debris ◽  
Distance Sampling ◽  
Sampling Technique ◽  
Sampling Techniques ◽  
New Methods ◽  
Unequal Probability ◽  
Perpendicular Distance ◽  
The Difference ◽  
Primary Advantage

Coarse woody debris (CWD) plays an important role in many forest ecosystem processes. In recent years, a number of new methods have been proposed to sample CWD. These methods select individual logs into the sample using some form of unequal probability sampling. One concern with most of these methods is the difficulty in estimating the volume of each log. A new method of sampling CWD that addresses this issue is proposed. This method samples each log with probability proportional to the volume of each piece of CWD. While this method generally has a smaller variance than the existing methods, the primary advantage is that a design-unbiased estimator of CWD volume is achieved without ever actually measuring the volume of any logs. This method, referred to as perpendicular distance sampling (PDS), is compared with three existing sampling techniques for CWD using a simulation study on a series of artificial populations. In every case, the variance of the PDS estimator of CWD volume was smaller than the variance of the competing methods, but the difference in the variance was not large between PDS and two of the competing methods. When estimating the number of pieces of CWD, the variance of the PDS estimator was one of the largest amongst the tested methods. An equally important result is that the variant of line intersect sampling used in this study, where the orientation of the line is the same at all sample points, performed poorly in every situation. This and other problems suggest that the suitability of this sampling technique for estimating CWD is questionable.

scholarly journals Cross-section mass: an improved basis for woody debris necromass inventory

Silva Fennica ◽  
2011 ◽  
Vol 45 (2) ◽  
Author(s):  
Markku Larjavaara ◽  
Helene Muller-Landau
Keyword(s):  
Cross Section ◽  
Woody Debris

Exploiting the pasture capacitance probe in agricultural research: a comparison with other methods of measuring herbage mass

1987 ◽  
Vol 108 (1) ◽  
pp. 155-163 ◽  
Author(s):  
S. F. Crosbie ◽  
B. M. Smallfield ◽  
H. Hawker ◽  
M. J. S. Floate ◽  
J. M. Keoghan ◽  
...  
Keyword(s):  
New Zealand ◽  
Cross Section ◽  
Agricultural Research ◽  
Field Trials ◽  
Relative Ranking ◽  
Capacitance Probe ◽  
Time Savings

SummaryThe precision of the capacitance probe in detecting herbage mass differences between treatments has been assessed on a cross section of field trials in Otago-Southland, New Zealand. Used thoughtfully, the probe appears at least as good as any other alternative. Corrected meter readings from the probe may be used directly for relative ranking of treatments although calibration is desirable for interpretation purposes, and becomes essential when swards of widely differing composition are to be related. Considerable overall time savings, especially in the laboratory, are possible in comparison with other methods.

Early results from field trials using Hypholoma fasciculare to reduce Armillaria ostoyae root disease

2004 ◽  
Vol 82 (7) ◽  
pp. 962-969 ◽  
Author(s):  
Bill Chapman ◽  
Guoping Xiao ◽  
Sheldan Myers
Keyword(s):  
Tree Species ◽  
Woody Debris ◽  
Forest Tree ◽  
Field Trials ◽  
Fruiting Bodies ◽  
Armillaria Ostoyae ◽  
South Central ◽  
Early Results ◽  
Different Types ◽  
Hypholoma Fasciculare

Armillaria ostoyae (Romagn.) Herink. causes serious damage to forest tree species worldwide. In this study, Hypholoma fasciculare (Huds. ex Fr.) Kummer was inoculated, after logging, into areas in south-central British Columbia that had been identified as having high levels of A. ostoyae. Hypholoma fasciculare was successfully established in a variety of different types of trials, as indicated by growth of H. fasciculare mycelium into roots of inoculated stumps and the presence of fruiting bodies on and around stumps. Three to five years after treatment, inoculated plots had biologically and statistically significantly lower levels of mortality attributable to A. ostoyae.Key words: Hypholoma fasciculare, Armillaria, biocontrol, woody debris.

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