ALBERT

Beschreibung: Forests, Vol. 9, Pages 362: Design-Unbiased Estimation and Alternatives for Sampling Trees on Plantation Rows Forests doi: 10.3390/f9060362 Authors: Thomas B. Lynch David Hamlin Mark J. Ducey Bruce E. Borders Recently, methods for inventories of forest plantations have been proposed based on the use of remote sensing to estimate total row length, followed by the estimation of plantation row attributes, such as number and volume or weight of trees, at randomly selected field locations on the ground within a forest plantation of interest. While we are aware of instances in which such inventories have been performed, to our knowledge, no scientific studies of this approach have previously appeared. Many plantation inventories have been performed by traditional methods, such as Bitterlich (point) sampling and fixed-size plot sampling. Random plot sizes including a fixed number of rows are possible but the resulting estimators are typically not unbiased. Plot sampling and Bitterlich sampling can be problematic in plantations because inventory crews may gravitate towards the establishment of sample points in similar locations relative to row spacing, e.g., midway between rows, compromising the assumption of random point location in the tract area. We propose and test five novel estimators which are based on sampling a fixed number of trees at random sample locations on rows. The methods we propose can be used to estimate tract-level quantities of any tree attribute, including the number of trees, total volume, basal area, and others. Fixed row lengths may be sampled at randomly determined field locations on rows. Alternatively, distance sampling methods can be used to sample a fixed number of trees subsequent to, or nearest to, a randomly located point on a plantation row. Ducey’s recently-developed estimator for point-to-particle sampling on lines can be applied to sampling on rows. A “mean of ratios” (MR) estimator can be based on the average ratio of the sum of the sample trees’ attributes divided by the length of line occupied by the sample trees. A “ratio of means” (RM) estimator can be based on the ratio of the mean of the sample trees’ attributes for all random points divided by the mean sample line length for all random points. For either of these ratio estimators, the line length may be chosen to include the gap between trees into which the random sample point falls (G-MR, mean of ratios including the sample gap and G-RM, ratio of means estimator including the sample gap), or it may be chosen to begin subsequent to that gap (NG-MR, mean of ratios not including the sample gap and NG-RM, ratio of means not including the sample gap). A simulation was used to test each of these techniques on typical plantation row populations. Two row populations were used in the simulation. One had relatively uniform spacing between trees on a row, which resembles the characteristics of young plantations. The second population contained numerous gaps, typical of more mature plantations that have been thinned and may be experiencing mortality. In the simulations, the estimators were used to estimate the number of trees in each population. Trends in other variables, such as volume or basal area, were similar to those for te estimated number of trees in the populations. The simulation results showed that the G-MR method had the smallest root mean square error followed by the NG-RM. Ducey’s method and the fixed-length row plot were both design-unbiased. Both the latter methods had low root mean square errors but these were slightly higher than some of the other methods. In contrast to the other methods tested, the NG-MR and G-RM methods were both substantially biased on a simulated row population containing large gaps which might occur due to mortality or thinning. The estimators which had good performance in simulations—Ducey’s method, G-MR, NG-RM, and fixed-length row sampling—are viable alternatives to traditional methods of sampling plantations, such as Bitterlich sampling and fixed-size plot sampling, if accurate plantation row lengths can be measured.

Beschreibung: Forests, Vol. 9, Pages 251: Use of Stereology in Forest Inventories—A Brief History and Prospects for the Future Forests doi: 10.3390/f9050251 Authors: Thomas B. Lynch Göran Ståhl Jeffrey H. Gove Several forest inventory techniques utilize approaches that are similar to stereological approaches often applied in microscopy and other fields. Stereology is characterized by the description and estimation of properties of objects based on samples of lower dimension than the object, e.g., 2-dimensional slices from 3-dimensional objects, 1-dimensional probes from 3-dimensional or 2-dimensional objects and dimensionless points from higher dimensional objects. The stereological character of many forest inventory methods was historically developed independently of recognition of a relationship with stereology. Strip sampling of forests, common in the late 19th and early 20th century, can be considered as a sterelogical approach if the strip centerline is viewed as a 1-dimensional probe of tree inclusion zones on a land area. The stereological character of plot sampling and Bitterlich sampling becomes evident if one views these methods as samples of 1-dimensional probes for volume within tree inclusion zones, or dimensionless points sampling for basal area in inclusion zones. Traditional methods of estimation of tree stem volume include samples of 2-dimensional cross-sectional area at fixed points along the tree stem to estimate 3-dimensional volume. Though these traditional methods usually use a shape assumption (e.g., parabolic frustum) for short stem segments, we show how a random-systematic start estimator of stem cross-sections can provide a design-unbiased estimate of stem volume without using any stem shape assumptions. Monte Carlo integration estimators of tree volume such as importance sampling that are designed to depend on only a few (usually one or two) tree upper-stem height or cross-sectional samples can also be viewed as stereological methods. Several forest inventory methods such as Matern’s individual tree basal area estimator and sector sampling can be viewed as local stereology, in which sample lines or slices pass through a central point. Finally, we suggest potential applications of stereological principles in the emerging “big data” era characterized by lidar and other remote sensing data and the assemblage of large tree and stand datasets. We suggest a new stem volume estimator which may have potential for future use with terrestrial lidar.

Beschreibung: The Chapman-Richards distribution is developed as a special case of the equilibrium solution to the McKendrick-Von Foerster equation. The Chapman-Richards distribution incorporates the vital rate assumptions o...

Beschreibung: The newer knowledge of nutrition shows that cereals and seed products are deficient in calcium, sodium, chlorine, and unknown substances, called fat-soluble A and water-soluble B sometimes referred to as “vitamines” or “accessory food factors.”McCollum(1) in America, has gone the length of proving bj actual experiment that cows and their calves can be raised to perfection on nothing but the complete maize plant, although maize grain is well known as a very incomplete food. In spite of his demonstration, and in spite of the obvious fact that nothing could be more like grass than an entire cereal plant and therefore suited to herbivora, very few practical or theoretical agriculturists recognise that straw is the most likely thing in the world to correct for the deficiencies of grain feeding. The difficulty is to get straw that is eatable. The practical farmer, when he happens to get a good sample, accepts it as a gift of fate and is content to turn it into profit for himself as soon as he can. The object of the enquiry, or rather the series of enquiries of which this forms a part, is to adopt the more scientific mode of procedure and endeavour to find out what differences of feeding value naturally occur in oat straw, and which of the conditions needed for high feeding value could be repeated at will, and what light such investigation threw on the old question of why farmers in some districts can fatten cattle on swedes and straw whilst in other districts it is found impossible. Oat straw is plentiful in this country and is probably well supplied with the so-called food accessories, that is the things that the grains lack; the problem at issue is how to get more of the eatable kind and less of the uneatable kind. Provided that the straw is eaten in fair quantity, the possible diminution of growth power, by partial destruction of vitamines due to keeping straw in the stack, is of no practical importance because of the large amount of the straw.