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Browse subject: forest mensuration
Number of records: 15

Field efficiency and bias of snag inventory methods.
About this Resource: Snags and cavity trees are important components of forests, but can be difficult to inventory precisely and are not always included in inventories because of limited resources. We tested the application of N-tree distance sampling as a time-saving snag sampling method and compared N-tree distance sampling to fixed-area sampling and modified horizontal line sampling in mixed pine-hardwood forests of southern Maine and New Hampshire. We also present a novel modification of N-tree distance sampling that limits the distance from plot center that an observer must search to find tally trees. A field test shows N-tree to be quick, but generally biased and characterized by high variability. Distance-limited N-tree sampling mitigates these problems, but not completely. We give recommendations for operational snag inventory in similar forest types.

yaImpute: An R Package for kNN Imputation
About this Resource: This article introduces yaImpute, an R package for nearest neighbor search and imputation. Although nearest neighbor imputation is used in a host of disciplines, the methods implemented in the yaImpute package are tailored to imputation-based forest attribute estimation and mapping. The impetus to writing the yaImpute is a growing interest in nearest neighbor imputation methods for spatially explicit forest inventory, and a need within this research community for software that facilitates comparison among different nearest neighbor search algorithms and subsequent imputation techniques. yaImpute provides directives for defining the search space, subsequent distance calculation, and imputation rules for a given number of nearest neighbors. Further, the package offers a suite of diagnostics for comparison among results generated from different imputation analyses and a set of functions for mapping imputation results.

Testing probabilistic techniques of timber volume estimation for forest management planning
About this Resource: The cost of management plan elaboration is one of the main factors hampering the operational implementation of forest management in Italy. Besides compartment descriptions, such a cost is mainly due to the quantitative assessment of stand dendrometrical attributes. The aim of this work is to test the integration of conventional forest mensuration techniques with probabilistic estimation procedures that in the last years have found ever wider implementation for inventorying small forest areas. Distinctively, the objective of this note is the comparative experimental testing of the following methods of timber volume assessment: two-phase relascope sampling; two-phase visual estimation. Under the examined conditions referred to Turkey oak and beech high stands in Central Italy, the latter method has provided hopeful results. The most accurate and precise options of two-phase visual estimation have allowed an average time saving around 40% with respect to the total tally, with an absolute bias around 4-5% with respect to the true value of compartment timber volume, and efficiency higher than the conventional one-phase systematic plot sampling.

DIAMETRIC AND HYPSOMETRIC STRUCTURE OF THE ARBOREOUS COMPONENT IN FRAGMENTS OF RAIN FOREST IN RECIFE-PE
About this Resource: The objective of this paper was to analyze the diametric and hypsometric structure of the arboreous component in fragments of Atlantic rain forest in Recife-PE, in order better understand the succession period of this patch. Twenty plots of 10 X 25 m (250 m2), totaling a sample area of 5.000 m2 (0,5 ha) were established. The plots were installed in the systematic way, in parallels lines in the south edge of fragment. The first line was installed at 10 m of the edge and the others at a distance of 50 m between lines. In all lines, the plots were installed 25 m of each other. The individuals inclusion level was DBH (Diameter at breast height = 1,30 m) greater than or equal to 4,77 cm. The trees had been mensured and labelled. The Detrended Correspondence Analysis was carried through (DCA). In the sampled area, 531 individuals were registered, pertaining to 25 botanical families, 41 genera and 54 species. The diametric individual structure presented the standard reverse-J-shape. The most of individuals, in relation to height class, was located in the central classes. However, some species were deficient in the initial classes. The correspondence (DCA), for quantitative or structural data had shown two well defined groups. The studied area is a secondary uneven aged forest formation, presenting an initial period of stage of succession.

Using Airborne Lidar to Discern Age Classes of Cottonwood Trees in a Riparian Area
About this Resource: Airborne lidar (light detecting and ranging) is a useful tool for probing the structure of forest canopies. Such information is not readily available from other remote sensing methods and is essential for modern forest inventories. In this study, small-footprint lidar data were used to estimate biophysical properties of young, mature, and old cottonwood trees in the San Pedro River basin near Benson, Arizona. The lidar data were acquired in June 2004, using Optech's 1233 ALTM during flyovers conducted at an altitude of 600 m. Canopy height, crown diameter, stem dbh, canopy cover, and mean intensity of return laser pulses from the canopy surface were estimated for the cottonwood trees from the data. Linear regression models were used to develop equations relating lidar-derived tree characteristics with corresponding field acquired data for each age class of cottonwoods. The lidar estimates show a good degree of correlation with ground-based measurements. This study also shows that other parameters of young, mature, and old cottonwood trees such as height and canopy cover, when derived from lidar, are significantly different (P < 0.05). Additionally, mean crown diameters of mature and young trees are not statistically different at the study site (P = 0.31). The results illustrate the potential of airborne lidar data to differentiate different age classes of cottonwood trees for riparian areas quickly and quantitatively.

A Comparison of Statistical Methods for Estimating Forest Biomass from Light Detection and Ranging Data.
About this Resource: Strong regression relationships between light detection and ranging (LIDAR) metrics and indices of forest structure have been reported in the literature. However, most papers focus on empirical results and do not consider LIDAR metric selection and biological interpretation explicitly. In this study, three different variable selection methods (stepwise regression, principle component analysis [PCA], and Bayesian modeling averaging [BMA]) were compared using LIDAR data from three study sites: Capitol Forest in western Washington State, Mission Creek in central Washington State, and Kenai Peninsula in south central Alaska. Separate aboveground biomass regression models were developed for each site as well as common models using three study sites simultaneously. Final biomass models have R 2 values ranging from 0.67 to 0.88 for three study sites. PCA indicates that three LIDAR metrics (mean height, coefficient variation of height, and canopy LIDAR point density) explain the majority of variation contained within a larger set of metrics. Within each study area, forest biomass models using these three predictor variables had similar R 2 values as the stepwise and BMA regression models. Individual site models using these three variables are recommended because these models are straightforward in terms of model form and biological interpretation and are easily adopted for application.

Regression modeling and mapping of coniferous forest basal area and tree density from discrete-return lidar and multispectral satellite data
About this Resource: We compared the utility of discrete-return light detection and ranging (lidar) data and multispectral satellite imagery, and their integration, for modeling and mapping basal area and tree density across two diverse coniferous forest landscapes in north-central Idaho. We applied multiple linear regression models subset from a suite of 26 predictor variables derived from discrete-return lidar data (2 m post spacing), advanced land imager (ALI) multispectral (30 m) and panchromatic (10 m) data, or geographic X, Y, and Z location. In general, the lidar-derived variables had greater utility than the ALI variables for predicting the response variables, especially basal area. The variables most useful for predicting basal area were lidar height variables, followed by lidar intensity; those most useful for predicting tree density were lidar canopy cover variables, again followed by lidar intensity. The best integrated models selected via a best-subsets procedure explained ~90% of variance in both response variables. Natural-logarithm-transformed response variables were modeled. Predictions were then transformed from the natural logarithm scale back to the natural scale, corrected for transformation bias, and mapped across the two study areas. This study demonstrates that fundamental forest structure attributes can be modeled to acceptable accuracy and mapped with currently available remote sensing technologies.

Field measurements of hygroscopic properties and state of mixing of nucleation mode particles
About this Resource: An Ultrafine Tandem Differential Mobility Analyser (UF-TDMA) has been used in several field campaigns over the last few years. The investigations were focused on the origin and properties of nucleation event aerosols, which are observed frequently in various environments. This paper gives a summary of the results of 10 nm and 20 nm particle hygroscopic properties from different measurement sites: an urban site, an urban background site and a forest site in Finland and a coastal site in western Ireland. The data can be classified in four hygroscopic growth classes: hydrofobic, less-hygroscopic, more-hygroscopic and sea-salt. Similar classification has been earlier presented for Aitken and accumulation mode particles. In urban air, the summertime 10 nm particles showed varying less-hygroscopic growth behaviour, while winter time 10 nm and 20 nm particles were externally mixed with two different hygroscopic growth modes. The forest measurements revealed diurnal behaviour of hygroscopic growth, with high growth factors at day time and lower during night. The urban background particles had growth behaviour similar to the urban and forest measurement sites depending on the origin of the observed particles. The coastal measurements were strongly affected by air mass history. Both 10 nm and 20 nm particles were hygroscopic in marine background air. The 10 nm particles produced during clean nucleation burst periods were hydrofobic. Diurnal variation and higher growth factors of 10 nm particles were observed in air affected by other source regions. External mixing was occasionally observed at all the sites, but incidents with more than two growth modes were extremely rare.

Field measurements of hygroscopic properties and state of mixing of nucleation mode particles
About this Resource: An Ultrafine Tandem Differential Mobility Analyser (UF-TDMA) has been used in several field campaigns over the last few years. The investigations were focused on the origin and properties of nucleation event aerosols, which are observed frequently in various environments. This paper gives a summary of the results of 10 nm and 20 nm particle hygroscopic properties from different measurement sites: an urban site, an urban background site and a forest site in Finland and a coastal site in western Ireland. The data can be classified in four hygroscopic growth classes: hydrofobic, less-hygroscopic, more-hygroscopic and sea-salt. Similar classification has been earlier presented for Aitken and accumulation mode particles. In urban air, the summertime 10 nm particles showed varying less-hygroscopic growth behaviour, while winter time 10 nm and 20 nm particles were externally mixed with two different hygroscopic growth modes. The forest measurements revealed diurnal behaviour of hygroscopic growth, with high growth factors at day time and lower during night. The urban background particles had growth behaviour similar to the urban and forest measurement sites depending on the origin of the observed particles. The coastal measurements were strongly affected by air mass history. Both 10 nm and 20 nm particles were hygroscopic in marine background air. The 10 nm particles produced during clean nucleation burst periods were hydrofobic. Diurnal variation and higher growth factors of 10 nm particles were observed in air affected by other source regions. External mixing was occasionally observed at all the sites, but incidents with more than two growth modes were extremely rare.

DIAMETER DISTRIBUTION OF ONE SEMIDECIDUOUS SEASONAL FOREST STAND OF CERRADO ECOMUSEUM AREA
About this Resource: A stand of a semideciduous forest of the Raio de Sol s farm (15º 45 54 S and 49º 04 03 W) with 10 ha was studied.It is inserted into the bioregion of the Cerrado Ecomuseum, Goiás state. For the phytosociological inventory, ten sample plots of 20 x20 m each were systematically laid out. In these plots all living trees with DBH above 5 cm were measured. 742 individuals belongingto 83 species, 67 genera and 36 families were registered. The diameter distribuition shows a tendency of a J inverse model. Ninetysix percent of the individuals are situated in the three first diameter classes. Studied vegetal community was balanced observedthrough the Liocourt quotient.

Mode resolved density of atmospheric aerosol particles
About this Resource: In this study, we investigate the mode resolved density of ultrafine atmospheric particles measured in boreal forest environment. The method used here enables us to find the distinct density information for each mode in atmospheric fine particle population: the density values for nucleation, Aitken, and accumulation mode particles are presented. The experimental data was gained during 2 May 2005–19 May 2005 at the boreal forest measurement station &quot;SMEAR II&quot; in Hyytiälä, Southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm&lt;sup&gt;3&lt;/sup&gt; (average 1.5 g/cm&lt;sup&gt;3&lt;/sup&gt;) and for Aitken mode from 0.4 to 2 g/cm&lt;sup&gt;3&lt;/sup&gt; (average 0.97 g/cm&lt;sup&gt;3&lt;/sup&gt;). As an overall trend during the two weeks campaign, the density value of Aitken mode was seen to gradually increase. With the present method, the time dependent behaviour of the particle density can be investigated in the time scale of 10 min. This allows us to follow the density evolution of the nucleation mode particles during the particle growth process following the nucleation burst. The density of nucleation mode particles decreased during the growth process. The density values for 15 nm particles were 1.2–1.5 g/cm&lt;sup&gt;3&lt;/sup&gt; and for grown 30 nm particles 0.5–1 g/cm&lt;sup&gt;3&lt;/sup&gt;. These values are consistent with the present knowledge that the condensing species are semi-volatile organics, emitted from the boreal forest.

Mode resolved density of atmospheric aerosol particles
About this Resource: In this study, we investigate the mode resolved density of ultrafine atmospheric particles measured in boreal forest environment. The method used here enables us to find the distinct density information for each mode in atmospheric fine particle population: the density values for nucleation, Aitken, and accumulation mode particles are presented. The experimental data was gained during 2 May 2005&ndash;19 May 2005 at the boreal forest measurement station &quot;SMEAR II&quot; in Hyytiälä, southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm&lt;sup&gt;3&lt;/sup&gt; (average 1.5 g/cm&lt;sup&gt;3&lt;/sup&gt;) and for Aitken mode from 0.4 to 2 g/cm&lt;sup&gt;3&lt;/sup&gt; (average 0.97 g/cm&lt;sup&gt;3&lt;/sup&gt;. As an overall trend during the two weeks campaign, the density value of Aitken mode was seen to gradually increase. With the present method, the time dependent behaviour of the particle density can be investigated in time scale of 10 min. This allows us the follow the density evolution of the nucleation mode particles during the particle growth process following the nucleation burst. The density of nucleation mode particles decreased during the growth process. The density values for 15 nm particles were 1.2&ndash;1.5 g/cm&lt;sup&gt;3&lt;/sup&gt; and for grown 30 nm particles 0.5&ndash;1 g/cm&lt;sup&gt;3&lt;/sup&gt;. These values are consistent with the present knowledge that the condensing species are semi volatile organics, emitted from the Boreal forest.

Growth and yield of all-aged Douglas-fir-western hemlock forest stands: a matrix model with stand diversity effects.
About this Resource: A density-dependent matrix model was developed for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) - western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest stands in the Pacific Northwest of the United States. The model predicted the number and volume of trees for 4 species groups and 19 diameter classes. The parameters were based on species-dependent equations linking individual tree growth, mortality, and stand recruitment to tree and stand characteristics, including stand diversity in terms of tree species and size. The equations were estimated with individual tree and stand data from 2706 permanent plots in western Washington and Oregon, largely from private and state lands, measured twice at an average interval of 10 years. Other things being equal, diameter growth increased slightly with species diversity and decreased with size diversity. Recruitment increased with species diversity and decreased with size diversity. Mortality was independent of species diversity and tended to increase with size diversity. There was practically no relationship between individual tree volume and species or size diversity. The number of trees predicted by the model over the interval between successive inventories was generally unbiased. Long-term predictions with different initial conditions were consistent with standard yield tables and compared favorably with those of the Forest Vegetation Simulator. The model also implied that, independently of its initial condition, an undisturbed stand would eventually reach a steady state dominated by western hemlock more than 1 m in diameter, with few trees of other species and size.

Etude dendrométrique d'Acacia auriculiformis A. Cunn. ex Benth. en mélange sur vertisol au Benin
About this Resource: Dendrometrical study of Acacia auriculiformis A. Cunn. in mixed stands on claysoils in Benin. Acacia auriculiformis is a fast growing species planted on vertisols in Benin. An inventory of 11 mixed stands of Acacia, which are 7 to 9 years old, has been realized to estimate growth parameters of the stands. The present study shows that, for the dendrometrical parameters, there is no difference between species associations at a 0.05 significance level. Nevertheless, the largest values of quadratic mean diameter of the stems foot are observed in the species associations including Leucaena leucocephala. Moreover, the branch volume decreases with the increasing of the number of stems per tree. The most appropriate volume function for Acacia auriculiformis is the one that takes into account the diameter of the stems foot and the total height. Otherwise, the species associations do not influence the profile of Acacia trees, which is constant within the associations. The predicted conversion and cutting coefficients show that the stacked wood volume represents about 144% of the real stand volume.