Steen Magnussen. (2013). An assessment of three variance estimators for the k-nearest neighbour technique. Silva Fennica vol. 47 no. 1 article id 925. https://doi.org/10.14214/sf.925

Keywords: forest inventory; simple random sampling; resampling estimators; bootstrap; jackknife; difference estimator; cluster sampling

Abstract | Full text in HTML | Full text in PDF | Author Info

A jackknife (JK), a bootstrap (BOOT), and an empirical difference estimator (EDE) of totals and variance were assessed in simulated sampling from three artificial but realistic complex multivariate populations (N = 8000 elements) organized in clusters of four elements. Intra-cluster correlations of the target variables (Y) varied from 0.03 to 0.26. Time-saving implementations of JK and BOOT are detailed. In simple random sampling (SRS), bias in totals was ≤ 0.4% for the two largest sample sizes (n = 200, 300), but slightly larger for n = 50, and 100. In cluster sampling (CLU) bias was typically 0.1% higher and more variable. The lowest overall bias was in EDE. In both SRS and CLU, JK estimates of standard error were slightly (3%) too high, while the bootstrap estimates in both SRS and CLU were too low (8%). Estimates of error suggested a trend in EDE toward an overestimation with increasing sample size. Calculated 95% confidence intervals achieved a coverage that in most cases was fairly close (± 2%) to the nominal level. For estimation of a population total the EDE estimator appears to be slightly better than the JK estimator.

Magnussen, Canadian Forest Service, Natural Resources Canada, 505 West Burnside Road, Victoria BC V8Z 1M5 Canada E-mail: steen.magnussen@nrcan.gc.ca

article id 382, category Research article

Steen Magnussen, René I. Alfaro, Paul Boudewyn. (2005). Survival-time analysis of white spruce during spruce budworm defoliation. Silva Fennica vol. 39 no. 2 article id 382. https://doi.org/10.14214/sf.382

Keywords: mortality; hazard rates; defoliation stress index; Cox proportional hazard regression; Choristoneura fumiferana

Abstract | View details | Full text in PDF | Author Info

Mortality and defoliation (DF%) in 987 white spruce (Picea glauca (Moench) Voss) trees were followed from 1992 to 2003 during an outbreak of the spruce budworm Choristoneura fumiferana (Clem.) in 15 white-spruce-dominated uneven-aged stands in the Fort Nelson Forest District near Prince George, British Columbia. Four stands were aerially sprayed with Bacillus thuringiensis (Bt). Defoliation and mortality levels were elevated in non-sprayed stands. The relationship between defoliation and survival-times was captured in a Cox proportional hazard model with a defoliation stress index (DSI), diameter (DBH), crown class (CCL), a random stand effect, Bt-treatment, and number of years of exposure to stand-level defoliation (DYEAR) as predictors. The DSI, optimized for discrimination between survivors and non-survivors, is the discounted sum of five lagged DF% values. Survival probabilities were predicted with a maximum error of 0.02. Hazard rates increased by 0.06 for every one point increase in DSI. CCL and random stand effects were highly significant. Bt-treatment effects were fully captured by DSI, CCL, and DYEAR.

Magnussen, Canadian Forest Service, Victoria, BC, Canada. V8Z 1M5 E-mail: smagnussen@pfc.forestry.ca
Alfaro, Canadian Forest Service, Victoria, BC, Canada. V8Z 1M5 E-mail: ria@nn.ca
Boudewyn, Canadian Forest Service, Victoria, BC, Canada. V8Z 1M5 E-mail: pb@nn.ca

article id 618, category Research article

Steen Magnussen, Paul Boudewyn, Mike Wulder, David Seemann. (2000). Predictions of forest inventory cover type proportions using Landsat TM. Silva Fennica vol. 34 no. 4 article id 618. https://doi.org/10.14214/sf.618

Keywords: neural net; maximum likelihood classification; agreement of predictions

Abstract | View details | Full text in PDF | Author Info

The feasibility of generating via Landsat TM data current estimates of cover type proportions for areas lacking this information in the national forest inventory was explored by a case study in New Brunswick. A recent forest management inventory covering 4196 km2 in south-eastern New Brunswick (the test area) and a coregistered Landsat TM scene was used to develop predictive models of 12 cover type proportions in an adjacent 4525 km2 region (the validation area). Four prediction models were considered, one using a maximum likelihood classifier (MLC), and three using the proportions of 30 TM clusters as predictors. The MLC was superior for non-vegetated cover types while a neural net or a prorating of cluster proportions was chosen for predicting vegetated cover types. Most predictions generated for national inventory photo-plots of 2 x 2 km were closer to the most recent inventory results than estimates extrapolated from the test area. Agreement between predictions and current inventory results varied considerably among cover types with model-based predictions outperforming, on average, the simple spatial extensions by about 14%. In this region, an 11-year-old forest inventory for the validation area provided estimates that in half the cases were closer to current inventory estimates than predictions using the optimal Landsat TM model. A strong temporal correlation of photo-plot-level cover type proportions made old-values more consistent than predictions using the optimal Landsat TM model in all but three cases. Prorating of cluster proportions holds promise for large-scale multi-sensor predictions of forest inventory cover types.

Magnussen, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: smagnussen@pfc.forestry.ca
Boudewyn, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: pb@nn.ca
Wulder, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: mw@nn.ca
Seemann, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: ds@nn.ca

Click this link to register to Silva Fennica.

If you are a registered user, log in to save your selected articles for later access.

Contents alert

Your selected articles
Send to email

Bettinger P., Graetz D. et al. (2002) Eight heuristic planning techniques applied to t.. Silva Fennica vol. 36 no. 2 article id 545 (remove) | Edit comment

Tomppo E., Korhonen K. T. et al. (2001) Multi-source inventory of the forests of the Heb.. Silva Fennica vol. 35 no. 3 article id 587 (remove) | Edit comment

Windisch J., Sikanen L. et al. (2010) Supply chain management applications for forest .. Silva Fennica vol. 44 no. 5 article id 124 (remove) | Edit comment

Peltola H., Kilpeläinen A. et al. (2007) Effects of early thinning regime and tree status.. Silva Fennica vol. 41 no. 3 article id 285 (remove) | Edit comment

Bogino S., Fernández Nieto M. J. et al. (2009) Climate effect on radial growth of Pinus sylvest.. Silva Fennica vol. 43 no. 4 article id 183 (remove) | Edit comment

Peltoniemi M., Thürig E. et al. (2007) Models in country scale carbon accounting of for.. Silva Fennica vol. 41 no. 3 article id 290 (remove) | Edit comment

Martín C., Parra T. et al. (2008) Genetic diversity and structure of the endangere.. Silva Fennica vol. 42 no. 4 article id 229 (remove) | Edit comment

Bieker D., Rust S. (2010) Non-destructive estimation of sapwood and heartw.. Silva Fennica vol. 44 no. 2 article id 153 (remove) | Edit comment

Kalliokoski T., Nygren P. et al. (2008) Coarse root architecture of three boreal tree sp.. Silva Fennica vol. 42 no. 2 article id 252 (remove) | Edit comment

Veijalainen A.-M., Juntunen M.-L. et al. (2007) Forest nursery waste composting in windrows with.. Silva Fennica vol. 41 no. 1 article id 305 (remove) | Edit comment

Heske F., (1929) Paper on knowledge on forest zones in West-Himal.. Acta Forestalia Fennica vol. 34 no. 30 article id 7243 (remove) | Edit comment

Salemaa M., Jukola-Sulonen E.-L. et al. (1991) Forest condition in Finland, 1986-1990. Silva Fennica vol. 25 no. 3 article id 5451 (remove) | Edit comment

Nyyssönen A., Kilkki P. (1965) Sampling a stand in forest survey Acta Forestalia Fennica vol. 79 no. 4 article id 7162 (remove) | Edit comment

Luukkanen O., (1972) Genetic variation of photosynthesis in forest tr.. Silva Fennica vol. 6 no. 2 article id 4863 (remove) | Edit comment

Leikola M., (1987) Academic dissertations and doctors in forestry s.. Acta Forestalia Fennica vol. 0 no. 199 article id 7646 (remove) | Edit comment

Päivinen R., Anttila P. (2001) How reliable is a satellite forest inventory? Silva Fennica vol. 35 no. 1 article id 610 (remove) | Edit comment

Mälkönen E., (1976) Effect of whole-tree harvesting on soil fertility. Silva Fennica vol. 10 no. 3 article id 4944 (remove) | Edit comment

Pukkala T., Kolström T. (1991) Effect of spatial pattern of trees on the growth.. Silva Fennica vol. 25 no. 3 article id 5449 (remove) | Edit comment

Vuoristo I., (1935) Investigations of the regression between the cub.. Acta Forestalia Fennica vol. 42 no. 6 article id 7323 (remove) | Edit comment

Cockayne L., (1929) Hybridism in the forests of New Zealand Acta Forestalia Fennica vol. 34 no. 3 article id 7216 (remove) | Edit comment

Marjokorpi A., Salo J. (2007) Operational standards and guidelines for biodive.. Silva Fennica vol. 41 no. 2 article id 297 (remove) | Edit comment

Roitto Y., (1963) Suomen sisävesien aluskanta. Puutavaraliikenteen.. Silva Fennica vol. 0 no. 113 article id 4711 (remove) | Edit comment

Follow @SilvaFennica