Comparison of relascope and fixed-radius plots for the estimation of forest stand variables in northeast Spain: an inventory simulation approach

Abstract

The Bitterlich relascope is a multiple use dendrometer widely used in forest inventory. Although it is most commonly used to estimate basal area, the relascope can also estimate other stand variables, including density and diameter distribution. However, forest stand inventories in Spain rarely use relascope plots to estimate these variables due to the belief that they lead to higher errors than fixed-radius plots due to the heterogeneity of many Mediterranean forests. This study compared the accuracy of the estimated averages of three main stand variables (basal area, stand density, and diameter class distribution) in forest stand inventories performed with relascope plots and with conventional fixed-radius circular plots, both measuring a similar number of trees (15)(16)(17)(18)(19)(20). A forest stand inventory simulator (DOMO) was used (1) to generate simulated forest stands corresponding to the nine most common types in the Mediterranean region of Catalonia (NE Spain), including even-aged and uneven-aged stands, and (2) to estimate and compare the average values of these variables at the forest stand level resulting from both plot types. In general, we did not find significant accuracy differences between the inventory systems for most of the stand variables and forest types studied, as expected by established angle-count sampling theory. However, the results show that for stands with multiple strata and open structures, the Bitterlich relascope provides a more accurate estimate for basal area than for density, while the reverse occurs for fixed-radius plots.

Easy and Quick Survey Method to Estimate Quantitative Characteristics in the Thin Forests

“…Ultimately, the transect method was selected as the optimal sampling method in the Arasbaran forests. Pique et al (2011) compared the accuracy of the estimated means of three main stand variables (basal area, stand density, and diameter class distribution) in forest stand inventories performed with relascope plots and with conventional fixed radius circular plots, both measuring a similar number of trees (15)(16)(17)(18)(19)(20). The results showed that for stands with multiple strata and open structures, the Bitterlich relascope provided a more accurate estimate for basal area than for density, while the reverse occurred for fixed radius plots.…”

Delineation of Individual Tree Crowns from ALS and Hyperspectral data: a comparison among four methods

“…Forest inventories are usually based on the measurement of some field plots (e.g. one plot per hectare of forest) either of fixed size or using the angle count sampling technique [Gasparini and Di Cosmo, 2015;Piqué et al, 2011], and to average the values measured over stands having uniform structural characteristics [Gregoire and Valentine, 2008]. As usual for the surveys based on statistical sampling, which are preferred for large scale inventories to reduce the fieldwork, the spatial detail is not preserved, which can be problematic especially in forests managed with selective lodging, and characterized by the presence of mixed tree species.…”

Yes in my backyard : market based mechanisms for forest conservation and climate change mitigation in La Primavera, Mexico

“…These are based on geometric principles and give values consistent to those obtained by the measurement of trees in standard inventory plots (e.g. Grosenbaugh, 1952;Piqué et al, 2011). …”

“…Palley and Horwitz 1961;Grenier et al, 1991;Piqué et al, 2011). Generating information for basal area and tree density through these alternative methods will be faster, cheaper and easier than using full forest inventories in which the dimensions of all the trees in sampling plots are measured individually.…”

“…Basal area is one of the variables most used in the forestry trade for a variety of objectives (particularly in timber management). It has the advantage that it can be quickly and consistently assessed in the field (Piqué et al, 2011). The data from the forest inventory is used in combination with a theoretical analysis of the allometric equations most to explore the use of plot level basal area data to simplify the process of estimating carbon stocks; this under the assumption that any reduction in the cost of generating the information will reduce transaction costs in market-based mechanisms.…”