Comparison ofT-Square, Point Centered Quarter, andN-Tree Sampling Methods inPittosporum undulatumInvaded Woodlands (original) (raw)
Related papers
Revista Árvore, 2010
In order to verify Point-Centered Quarter Method (PCQM) accuracy and efficiency, using different numbers of individuals by per sampled area, in 28 quarter points in an Araucaria forest, southern Paraná, Brazil. Three variations of the PCQM were used for comparison associated to the number of sampled individual trees: standard PCQM (SD-PCQM), with four sampled individuals by point (one in each quarter), second measured (VAR1-PCQM), with eight sampled individuals by point (two in each quarter), and third measuring (VAR2-PCQM), with 16 sampled individuals by points (four in each quarter). Thirty-one species of trees were recorded by the SD-PCQM method, 48 by VAR1-PCQM and 60 by VAR2-PCQM. The level of exhaustiveness of the vegetation census and diversity index showed an increasing number of individuals considered by quadrant, indicating that VAR2-PCQM was the most accurate and efficient method when compared with VAR1-PCQM and SD-PCQM. RESUMO -O objetivo deste estudo foi verificar a precisão e a eficiência do método Quadrante Centrado em um Ponto (PCQM), usando diferentes números de indivíduos por amostra, em 28 unidades amostrais em uma área de Floresta Ombrófila Mista no sul do Paraná, Brasil. Foram comparadas três variações do método com relação ao número de indivíduos amostrados: primeira variação (SD-PCQM), amostragem com quatro indivíduos por ponto (um por quadrante), segunda variação (VAR1-PCQM), amostragem com oito indivíduos por ponto (dois em cada quadrante), e terceira variação (VAR2-PCQM), amostragem com 16 indivíduos por ponto (quatro indivíduos em cada quadrante). Foram registradas 31 espécies pelo SD-PCQM, 48 pelo VAR1-PCQM e 60 espécies pelo VAR2-PCQM. O nível de eficiência da amostragem da vegetação e o índice de diversidade apresentaram um acréscimo de acordo com o número de indivíduos por quadrante, incluídos na amostra, indicando que o VAR2-PCQM foi o mais preciso e eficiente método quando comparado com VAR1-PCQM e SD-PCQM. Palavras-chave: Método de amostragem, Fitossociologia e Floresta Ombrófila Mista.
Field methods for sampling tree height for tropical forest biomass estimation
Methods in ecology and evolution, 2018
Quantifying the relationship between tree diameter and height is a key component of efforts to estimate biomass and carbon stocks in tropical forests. Although substantial site-to-site variation in height-diameter allometries has been documented, the time consuming nature of measuring all tree heights in an inventory plot means that most studies do not include height, or else use generic pan-tropical or regional allometric equations to estimate height.Using a pan-tropical dataset of 73 plots where at least 150 trees had in-field ground-based height measurements, we examined how the number of trees sampled affects the performance of locally derived height-diameter allometries, and evaluated the performance of different methods for sampling trees for height measurement.Using cross-validation, we found that allometries constructed with just 20 locally measured values could often predict tree height with lower error than regional or climate-based allometries (mean reduction in predictio...
Biotropica, 2012
A standardized rapid inventory method providing information on both tree species diversity and aboveground carbon stocks in tropical forests will be an important tool for evaluating efforts to conserve biodiversity and to estimate the carbon emissions that result from deforestation and degradation (REDD). Herein, we contrast five common plot methods differing in shape, size, and effort requirements to estimate tree diversity and aboveground tree biomass (AGB). We simulated the methods across six Neotropical forest sites that represent a broad gradient in forest structure, tree species richness, and floristic composition, and we assessed the relative performance of methods by evaluating the bias and precision of their estimates of AGB and tree diversity. For a given sample of forest area, a 'several small' (< 1 ha) sampling strategy led to a smaller coefficient of variation (CV) in the estimate of AGB than a 'few large' one. The effort (person-days) required to achieve an accurate AGB estimate (< 10% CV), however, was greater for the smallest plots (0.1 ha) than for a compromise approach using 0.5 ha modified Gentry plots, which proved to be the most efficient method to estimate AGB across all forest types. Gentry plots were also the most efficient at providing accurate estimates of tree diversity (< 10% CV of Hill number). We recommend the use of the 0.5 ha modified Gentry plot method in future rapid inventories, and we discuss a set of criteria that should inform any choice of inventory method.
– In order to verify Point-Centered Quarter Method (PCQM) accuracy and efficiency, using different numbers of individuals by per sampled area, in 28 quarter points in an Araucaria forest, southern Paraná, Brazil. Three variations of the PCQM were used for comparison associated to the number of sampled individual trees: standard PCQM (SD-PCQM), with four sampled individuals by point (one in each quarter), second measured (VAR1-PCQM), with eight sampled individuals by point (two in each quarter), and third measuring (VAR2-PCQM), with 16 sampled individuals by points (four in each quarter). Thirty-one species of trees were recorded by the SD-PCQM method, 48 by VAR1-PCQM and 60 by VAR2-PCQM. The level of exhaustiveness of the vegetation census and diversity index showed an increasing number of individuals considered by quadrant, indicating that VAR2-PCQM was the most accurate and efficient method when compared with VAR1-PCQM and SD-PCQM. RESUMO – O objetivo deste estudo foi verificar a precisão e a eficiência do método Quadrante Centrado em um Ponto (PCQM), usando diferentes números de indivíduos por amostra, em 28 unidades amostrais em uma área de Floresta Ombrófila Mista no sul do Paraná, Brasil. Foram comparadas três variações do método com relação ao número de indivíduos amostrados: primeira variação (SD-PCQM), amostragem com quatro indivíduos por ponto (um por quadrante), segunda variação (VAR1-PCQM), amostragem com oito indivíduos por ponto (dois em cada quadrante), e terceira variação (VAR2-PCQM), amostragem com 16 indivíduos por ponto (quatro indivíduos em cada quadrante). Foram registradas 31 espécies pelo SD-PCQM, 48 pelo VAR1-PCQM e 60 espécies pelo VAR2-PCQM. O nível de eficiência da amostragem da vegetação e o índice de diversidade apresentaram um acréscimo de acordo com o número de indivíduos por quadrante, incluídos na amostra, indicando que o VAR2-PCQM foi o mais preciso e eficiente método quando comparado com VAR1-PCQM e SD-PCQM.
Phytocoenologia, 2009
Stand inventories are indispensable in community and population studies, diversity and conservation assessments, and pattern search, representing the fi rst step towards understanding distribution and abundance variation of species in space. As species abundance descriptors are estimated through sampling, the precision of the estimates is important to assess data scope. In a 6.5-ha area of a semideciduous Atlantic forest, SE Brazil, we randomly located 100 plots of 10 10 m to sample trees with DBH 5 cm. We calculated the sampling error of estimates of density, frequency, dominance, and importance value index (IVI) for species with fi ve or more adult individuals, and determined the number of plots necessary not to exceed sampling errors of 20 %. Esenbeckia leiocarpa (Rutaceae), the most abundant species, was the only species for which sampling errors did not exceed 20 %. The most appropriate criterion for evaluation of the sampling suffi ciency for the inventory of the stand as a whole was the one based on the general sampling error of a set of the most abundant species. The estimates of density, frequency and IVI were infl uenced by the aggregation of individuals. The estimate of dominance had a greater infl uence of the basal area variation among individuals. Frequency had the greatest precision, dominance had the smallest, and density and IVI had intermediate precision.
Comparative evaluation of accuracy and efficiency of six forest sampling methods
PROCEEDINGS- …, 2002
We compared estimates of woody stem density with known stem densities in three forest stands in southeast Oklahoma by using fixed-radius plots 3.64 m radius (0.01 acre; FRPs-AC), fixed-radius plots 5.64 m radius (0.01 ha; FRPs-HA); 10 m X 10 m quadrat (0.01 ha; QUAD), variable-radius plot (VRP), point-centered quarter (PCQ), and belt transect (BT) sampling techniques. These stands varied in stem density and were categorized as high, moderate, and low density stands. We found that FRPs were the most time-efficient and produced the most accurate estimates regardless of stem size. The VRP and PCQ methods were also timeefficient, but tended to underestimate actual stem density. Although FRPs of suitable size are accurate for large diameter stems in dense forest, time constraints limit applicability. We recommend using FRPs for small stems [(2.54-11.42 cm diameter breast height (DBH)] and VRPs for large stems (>11.43 cm DBH). These methods with appropriate sample sizes should be applied after pre-sampling has been completed to determine sampling variance. This combination of methodologies provides a quick and relatively accurate manner to characterize or monitor change in the wide range of forest conditions found in Oklahoma.
Tree height and tropical forest biomass estimation
Biogeosciences, 2013
Tropical forests account for approximately half of above-ground carbon stored in global vegetation. However, uncertainties in tropical forest carbon stocks remain high because it is costly and laborious to quantify standing carbon stocks. Carbon stocks of tropical forests are determined using allometric relations between tree stem diameter and height and biomass. Previous work has shown that the inclusion of height in biomass allometries, compared to the sole use of diameter, significantly improves biomass estimation accuracy. Here, we evaluate the effect of height measurement error on biomass estimation and we evaluate the accuracy of recently published diameter-height allometries at four areas within the Brazilian Amazon. As no destructive sample of biomass was available at these sites, reference biomass values were based on allometries. We found that the precision of individual tree height measurements ranged from 3 to 20 % of total height. This imprecision resulted in a 5-6 % uncertainty in biomass when scaled to 1 ha transects. Individual height measurement may be replaced with existing regional and global height allometries. However, we recommend caution when applying these relations. At Tapajos National Forest in the Brazilian state of Pará, using the pantropical and regional allometric relations for height resulted in site biomass 21 % and 25 % less than reference values. At the other three study sites, the pantropical equation resulted in errors of less that 2 %, and the regional allometry produced errors of less than 12 %. As an alternative to measuring all tree heights or to using regional and pantropical relations, we recommend measuring height for a well-distributed sample of about 100 trees per site. Following this methodology, 95 % confidence intervals of transect biomass were constrained to within 4.5 % on average when compared to reference values.
ECOTROPICA 12: 151–160, 2006, 2006
It is widely accepted that tree species from tropical old-growth late-successional forests (natural forests) differ markedly in their leaf morphological and physiological attributes from tropical pioneer (early-successional) trees, which often form secondary forests in clear-cut areas. For example, higher foliar nitrogen contents, higher photosynthetic activities, and a larger leaf size have frequently been reported for pioneer tree species. Since most tropical forests are rich in tree species, we hypothesize that the results of a morphological and functional comparison between natural forest (NF) and secondary forest (SF) species may largely depend on the sampling design, i.e. the number of tree species sampled and how these are selected in the stands. To test this hypothesis we compared three different leaf-sampling strategies (SA: species average based on a large random sample; NSA: species average based on a small random sample; WSA: species average SA weighted by tree species frequency) with the results of a nearly complete stand inventory. The study was conducted in NF and SF stands in the lower montane rainforest of Central Sulawesi, Indonesia. As expected, the SA, NSA and WSA sampling strategies gave different results with respect to the assumed functional dichotomy between NF and SF trees. Our data indicate that, for many leaf attributes, more than 20 or 25 species per forest type are required for detecting significant differences between NF and SF trees. Leaf size was the only parameter that was significantly affected by a sampling effect, resulting from the absence of very large-leaved species in small samples. If the focus of interest is on the leaf traits of the ‘average tree’ of a forest type, as in biogeochemical studies, the weighted species average (WSA) approach, which also considers species abundances, should be given preference over simple species averages (SA and NSA).
Angle-count sampling method for estimating forest stand volume – a practical approach
2020
The forest stand is defined as a group of trees occupying a specific area, which is sufficiently uniform in species composition, age arrangement and condition as to be distinguishable from the forest on adjoining areas. It represents the unit for which one and the same silvicultural treatment is prescribed. Quantitative information about stand or forest compartments, therefore, relates directly to silvicultural and management decisions. Stand measurements provide information about age, mean diameter, mean and top height, stand density, stand mixture and stand composition, volume and biomass, site index, site class or yield class, present and future growth, stand quality and vitality as well as yield (Bell and Dilworth, 1990; Laar and Akca, 2007; Veperdi, 2011). Point (angle count) sampling is a method of selecting trees to be tallied on the basis of their sizes rather than by their frequency of occurrence. Sample points, somewhat analogous to plot centers, are located within a fores...
Open Journal of Forestry
Big Basal Area Factor (Big BAF) and Point-3P are two-stage sampling methods. In the first stage the sampling units, in both methods, are Bitterlich points where the selection of the trees is proportional to their basal area. In the second stage, sampling units are trees which are a subset of the first stage trees. In the Big BAF method, the probability of selecting trees in the second stage is made proportional to the two BAFs' ratio, with a basal area factor larger than that of the first stage. In the Point-3P method the probability of selecting trees, in the second stage, is based on the height prediction and use of a specific random number table. Estimates of the forest stands' volume and their sampling errors are based on the theory of the product of two random variables. The increasing error in the second stage is small, but the total cost of measuring the trees is much smaller than simply using the first stage, with all the trees measured. In general, the two sampling methods are modern and cost-effective approaches that can be applied in forest stand inventories for forest management purposes and are receiving the growing interest of researchers in the current decade.