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Digitale Medien

Distribution and Variability of Surface Soil Properties at a Regional Scale (2000)

Brejda, John J. ; Moorman, Thomas B. ; Smith, Jeffrey L. ; [weitere]

Springer

Soil Science Society of America journal 64 (2000), S. 974-982

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ISSN: 1435-0661

Schlagwort(e): MBC, microbial biomass carbon MEP, Mehlich extractable phosphorus MLRA, Major Land Resource Areas MWD, mean-weight diameter NRCS, Natural Resources Conservation Service NRI, National Resource Inventory PMN, potentially mineralizable nitrogen PSU, primary sampling units TOC, total organic carbon WSA, water stable aggregates

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: e transformation resulted in normal distributions for most soil properties and reduced variability two- to threefold. However, a few soil properties remained non-normally distributed. Soil pH may be monitored at the regional scale with a high degree of precision. Small changes in soil C content (3–8% of the regional mean) may be detected using loge transformed total organic C as the indicator. Sampling soil properties as part of the NRI should improve NRCS' ability to monitor soil condition on a regional scale.

Materialart: Digitale Medien

URL: http://dx.doi.org/

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A mirage boundary correction method for distance sampling (2012)

Lynch, Thomas B.

Canadian Science Publishing

In: Canadian Journal of Forest Research. 2012; 42(2): 272-278. Published 2012 Feb 01. doi: 10.1139/x11-185.

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Publikationsdatum: 2012-02-01

Print ISSN: 0045-5067

Digitale ISSN: 1208-6037

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Publiziert von Canadian Science Publishing

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An antithetic variate to facilitate upper-stem height measurements for critical height sampling with importance sampling (2013)

Lynch, Thomas B. ; Gove, Jeffrey H.

Canadian Science Publishing

In: Canadian Journal of Forest Research. 2013; 43(12): 1151-1161. Published 2013 Dec 01. doi: 10.1139/cjfr-2013-0279.

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Publikationsdatum: 2013-12-01

Beschreibung: Critical height sampling (CHS) estimates cubic volume per unit area by multiplying the sum of critical heights measured on trees tallied in a horizontal point sample (HPS) by the HPS basal area factor. One of the barriers to practical application of CHS is the fact that trees near the field location of the point-sampling sample point have critical heights that occur quite high on the stem, making them difficult to view from the sample point. To surmount this difficulty, use of the “antithetic variate” associated with the critical height together with importance sampling from the cylindrical shells integral is proposed. This antithetic variate will be u = (1 − b/B), where b is the cross-sectional area at “borderline” condition and B is the tree’s basal area. The cross-sectional area at borderline condition b can be determined with knowledge of the HPS gauge angle by measuring the distance to the sample tree. When the antithetic variate u is used in importance sampling, the upper-stem measurement will be low on tree stems close to the sample point and high on tree stems distant from the sample point, enhancing visibility and ease of measurement from the sample point. Computer simulations compared HPS, CHS, CHS with importance sampling (ICHS), ICHS and an antithetic variate (AICHS), and CHS with paired antithetic varariates (PAICHS) and found that HPS, ICHS, AICHS, and PAICHS were very nearly equally precise and were more precise than CHS. These results are favorable to AICHS, since it should require less time than either PAICHS or ICHS and is not subject to individual-tree volume equation bias.

Print ISSN: 0045-5067

Digitale ISSN: 1208-6037

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Publiziert von Canadian Science Publishing

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n-Tree distance sampling for per-tree estimates with application to unequal-sized cluster sampling of increment core data (2003)

Lynch, Thomas B ; Wittwer, Robert F

Canadian Science Publishing

In: Canadian Journal of Forest Research. 2003; 33(7): 1189-1195. Published 2003 Jul 01. doi: 10.1139/x03-036.

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Publikationsdatum: 2003-07-01

Beschreibung: Samples from the n trees nearest to a point or plot center are sometimes used to estimate per-tree values such as age or growth from increment cores. Clutter et al. (J.L. Clutter, J.C. Fortson, L.V. Pienaar, G.H. Brister, and R.L. Bailey. 1983. Timber management: a quantitative approach. John Wiley & Sons, New York) indicated that this procedure can be biased because it is more likely to sample large trees occupying large amounts of space. This sampling procedure falls into the category of n-tree distance sampling in which the nth closest tree to a point defines a plot radius that can be used to estimate number of trees or amount of volume per hectare. When a ratio of n-tree per-hectare estimates is used to estimate per-tree attributes, the resulting estimator is a weighted average in which weights are the inverse of the n-tree sampling plot size. Since this ratio estimator essentially weights observations inversely with plot size, it is not subject to the objections of Clutter et al. (1983). This estimator is used to estimate age by diameter at breast height class for eastern cottonwood (Populus deltoides Bartr. ex Marsh.) on the Cimarron National Grassland.

Print ISSN: 0045-5067

Digitale ISSN: 1208-6037

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Publiziert von Canadian Science Publishing

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The unbiasedness of a generalized mirage boundary correction method for Monte Carlo integration estimators of volume (2014)

Lynch, Thomas B. ; Gove, Jeffrey H.

Canadian Science Publishing

In: Canadian Journal of Forest Research. 2014; 44(7): 810-819. Published 2014 Jul 01. doi: 10.1139/cjfr-2014-0031.

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Publikationsdatum: 2014-07-01

Beschreibung: The typical “double counting” application of the mirage method of boundary correction cannot be applied to sampling systems such as critical height sampling (CHS) that are based on a Monte Carlo sample of a tree (or debris) attribute because the critical height (or other random attribute) sampled from a mirage point is generally not equal to the critical height measured from the original sample point. A generalization of the mirage method is proposed for CHS and related techniques in which new samples of critical heights or other dimensions are obtained from mirage points outside the tract boundary. This is necessary because, in the case of CHS, the critical height actually depends on the distance between the tree and a randomly located sample point. Other spatially referenced individual tree attribute or coarse woody debris (CWD) estimators that use Monte Carlo integration with importance sampling have been developed in which the tree or CWD attribute estimate also depends on the distance between the tree and the sample point. The proposed modified mirage method is shown to be design unbiased. The proof includes general application to Monte Carlo integration estimators for objects such as CWD sampled from points.

Print ISSN: 0045-5067

Digitale ISSN: 1208-6037

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Publiziert von Canadian Science Publishing

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