Potential of UltraCamX stereo images for estimating timber volume and basal area at the plot level in mixed European forests

2013 ◽  
Vol 43 (8) ◽  
pp. 731-741 ◽  
Author(s):  
Christoph Straub ◽  
Christoph Stepper ◽  
Rudolf Seitz ◽  
Lars T. Waser
Keyword(s):  
Point Cloud ◽  
Forest Canopy ◽  
Complex Structure ◽  
Mixed Forest ◽  
Basal Area ◽  
Deciduous Tree ◽  
Stereo Images ◽  
Timber Volume ◽  
European Forests ◽  
Forest Attributes

Current technical advances in the field of digital photogrammetry demonstrate the great potential of automatic image matching for deriving dense surface measurements of the forest canopy. In contrast to airborne laser scanning (ALS), aerial stereo images are updated more regularly by national or regional mapping agencies in several countries. Frequently, ALS-based terrain models (DTMs) are available, and thus photogrammetric canopy heights can be derived. However, currently, there is little knowledge as to how accurately forest attributes can be modeled using the aerial stereo images acquired by these official, regular aerial surveys, especially for mixed forests in central Europe. Thus, a photogrammetric point cloud derived from UltraCamX stereo images in combination with an ALS-DTM and a classification of coniferous and deciduous tree regions (based on orthoimages) was used to create a stratified estimation of timber volume and basal area in a mixed forest in Germany. Suitable models were derived at the plot level using explanatory variables from the photogrammetric point cloud (which was normalized using an ALS-DTM). The prior stratification of conifer- and deciduous-dominated field plots slightly improved the estimation accuracy. The results verify that stereo images can be an alternative to ALS data for modeling key forest attributes, even in mixed central European forests with complex structure.

Mixtures of airborne lidar-based approaches improve predictions of forest structure

2021 ◽  
Author(s):  
Ryan Christopher Blackburn ◽  
Robert Buscaglia ◽  
Andrew Sanchez Meador
Keyword(s):  
Feature Selection ◽  
New Mexico ◽  
Random Forests ◽  
Forest Structure ◽  
Point Cloud ◽  
Basal Area ◽  
Airborne Lidar ◽  
Forest Attributes ◽  
Field Plots ◽  
Paired T Test

The most common method for modeling forest attributes with airborne lidar, the area-based approach, involves summarizing the point cloud of individual plots and relating this to attributes of interest. Tree- and voxel-based approaches have been considered as alternatives to the area-based approach but are rarely considered in an area-based context. We estimated three forest attributes: basal area, overstory biomass, and volume, across 1,680 field plots in Arizona and New Mexico. Variables from the three lidar approaches (area, tree, voxel) were created for each plot. Random forests were estimated using subsets of variables based on each individual lidar approach and mixtures of each approach. Boruta feature selection was performed on variable subsets, including the mixture of all lidar-approach predictors (KS-Boruta). A corrected paired t-test was utilized to compare six validated models (area-Boruta, tree-Boruta, voxel-Boruta, KS-Boruta, KS-all, ridge-all) for each forest attribute. Based on significant reductions in error (SMdAPE), basal area and biomass were best modeled with KS-Boruta while volume was best modeled with KS-all. Analysis of variable importance shows voxel-based predictors are critical for the prediction of the three forest attributes. This study highlights the importance of multi-resolution voxel-based variables for modeling forest attributes in an area-based context.

Point accuracy of combined pseudorange and carrier phase differential GPS under forest canopy

1999 ◽  
Vol 29 (5) ◽  
pp. 547-553 ◽  
Author(s):  
Erik Næsset
Keyword(s):  
Carrier Phase ◽  
Forest Canopy ◽  
Basal Area ◽  
Single Frequency ◽  
Deciduous Tree ◽  
Differential Gps ◽  
Positional Accuracy ◽  
Combined Use ◽  
Tree Canopies ◽  
The Mean

One 6-channel and two 12-channel single frequency GPS receivers observing C/A (course/acquisition) code and carrier phase were tested to determine positional point accuracies under conifer and deciduous tree canopies. Positional accuracies were determined for 38 subcanopy sites by differential processing of C/A code observations only and combined use of C/A code and carrier phase. Observation periods of 2.5-30 min were evaluated. Mean positional accuracy ranged from 1.17 to 3.70 m for the 12-channel receivers based on 2.5-30 min of observation of C/A code. Mean accuracy ranged from 0.79 to 2.25 m for combined use of C/A code and carrier phase. The accuracy was 7.34 m with 30 min of C/A code observations with the 6-channel receiver. With combined use of C/A code and carrier phase the mean accuracy of the 6-channel receiver increased to 0.98-2.44 m. The accuracy increased with decreasing basal area and improving geometric satellite distribution. The mean accuracy was significantly higher for the 12-channel receivers than for the 6-channel receiver and significantly higher by combined use of C/A code and carrier phase than use of C/A code only.

scholarly journals Multisensorial Close-Range Sensing Generates Benefits for Characterization of Managed Scots Pine (Pinus sylvestris L.) Stands

2020 ◽  
Author(s):  
Tuomas Yrttimaa ◽  
Ninni Saarinen ◽  
Ville Kankare ◽  
Niko Viljanen ◽  
Jari Hynynen ◽  
...  
Keyword(s):  
Pinus Sylvestris ◽  
Scots Pine ◽  
Forest Structure ◽  
Point Cloud ◽  
Forest Canopy ◽  
Basal Area ◽  
Weighted Mean ◽  
Range Sensing ◽  
Close Range

Terrestrial laser scanning (TLS) provides detailed three-dimensional representation of the surrounding forest structure. However, due to close-range hemispherical scanning geometry, the ability of TLS technique to comprehensively characterize all trees and especially the upper parts of forest canopy is often limited. In this study, we investigated how much forest characterization capacity can be improved in managed Scots pine (Pinus sylvestris L.) stands if TLS point cloud is complemented with a photogrammetric point cloud acquired from above the canopy using unmanned aerial vehicle (UAV). In this multisensorial (TLS+UAV) close-range sensing approach, the used UAV point cloud data was considered feasible especially in characterizing the vertical forest structure and improvements were obtained in estimation accuracy of tree height as well as plot-level basal-area weighted mean height (Hg) and mean stem volume (Vmean). Most notably the root mean square error (RMSE) in Hg improved from 0.88 m to 0.58 m and the bias improved from -0.75 m to -0.45 m with the multisensorial close-range sensing approach. However, in managed Scots pine stands the mere TLS captured also the upper parts of the forest canopy rather well. Both approaches were capable of deriving stem number, basal area, Vmean, Hg and basal area-weighted mean diameter with a relative RMSE less than 5.5% for all of the sample plots. Although the multisensorial close-range sensing approach mainly enhanced characterization of forest vertical structure in single-species, single-layer forest conditions, representation of more complex forest structures may benefit more from point clouds collected with sensors of different measurement geometries.

scholarly journals Depletion of atmospheric gaseous elemental mercury by plant uptake at Mt. Changbai, Northeast China

2016 ◽  
Vol 16 (20) ◽  
pp. 12861-12873 ◽  
Author(s):  
Xuewu Fu ◽  
Wei Zhu ◽  
Hui Zhang ◽  
Jonas Sommar ◽  
Ben Yu ◽  
...  
Keyword(s):  
Tree Species ◽  
Northeast China ◽  
Forest Canopy ◽  
Mixed Forest ◽  
Elemental Mercury ◽  
Chemical Oxidation ◽  
Deciduous Tree ◽  
Pinus Koraiensis ◽  
Polar Regions ◽  
Gaseous Elemental Mercury

Abstract. There exists observational evidence that gaseous elemental mercury (GEM) can be readily removed from the atmosphere via chemical oxidation followed by deposition in the polar and sub-polar regions, free troposphere, lower stratosphere, and marine boundary layer under specific environmental conditions. Here we report GEM depletions in a temperate mixed forest at Mt. Changbai, Northeast China. The strong depletions occurred predominantly at night during the leaf-growing season and in the absence of gaseous oxidized mercury (GOM) enrichment (GOM  <  3 pg m−3). Vertical gradients of decreasing GEM concentrations from layers above to under forest canopy suggest in situ loss of GEM to forest canopy at Mt. Changbai. Foliar GEM flux measurements showed that the foliage of two predominant tree species is a net sink of GEM at night, with a mean flux of −1.8 ± 0.3 ng m2 h−1 over Fraxinus mandshurica (deciduous tree species) and −0.1 ± 0.2 ng m2 h−1 over Pinus Koraiensis (evergreen tree species). Daily integrated GEM δ202Hg, Δ199Hg, and Δ200Hg at Mt. Changbai during 8–18 July 2013 ranged from −0.34 to 0.91 ‰, from −0.11 to −0.04 ‰ and from −0.06 to 0.01 ‰, respectively. A large positive shift in GEM δ202Hg occurred during the strong GEM depletion events, whereas Δ199Hg and Δ200Hg remained essentially unchanged. The observational findings and box model results show that uptake of GEM by forest canopy plays a predominant role in the GEM depletion at Mt. Changbai forest. Such depletion events of GEM are likely to be a widespread phenomenon, suggesting that the forest ecosystem represents one of the largest sinks ( ∼ 1930 Mg) of atmospheric Hg on a global scale.

scholarly journals Application of a Three-Dimensional Radiative Transfer Model to Retrieve the Species Composition of a Mixed Forest Stand from Canopy Reflected Radiation

2018 ◽  
Vol 10 (10) ◽  
pp. 1661 ◽  
Author(s):  
Natalia Levashova ◽  
Dmitry Lukyanenko ◽  
Yulia Mukhartova ◽  
Alexander Olchev
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Tree Species ◽  
Forest Canopy ◽  
Mixed Forest ◽  
Three Dimensional ◽  
Forest Stand ◽  
Deciduous Tree ◽  
Radiative Transfer Model ◽  
Transfer Model

The paper introduces a three-dimensional model to derive the spatial patterns of photosynthetically active radiation (PAR) reflected and absorbed by a non-uniform forest canopy with a multi-species structure, as well as a model algorithm application to retrieve forest canopy composition from reflected PAR measured along some trajectory above the forest stand. This radiative transfer model is based on steady-state transport equations, initially suggested by Ross, and considers the radiative transfer as a function of the structure of individual trees and forest canopy, optical properties of photosynthesizing and non-photosynthesizing parts of the different tree species, soil reflection, and the ratio of incoming direct and diffuse solar radiation. Numerical experiments showed that reflected solar radiation of a typical mixed forest stand consisting of coniferous and deciduous tree species was strongly governed by canopy structure, soil properties and sun elevation. The suggested algorithm based on the developed model allows for retrieving the proportion of different tree species in a mixed forest stand from measured canopy reflection coefficients. The method accuracy strictly depends on the number of points for canopy reflection measurements.

scholarly journals UAV Based Estimation of Forest Leaf Area Index (LAI) through Oblique Photogrammetry

2021 ◽  
Vol 13 (4) ◽  
pp. 803
Author(s):  
Lingchen Lin ◽  
Kunyong Yu ◽  
Xiong Yao ◽  
Yangbo Deng ◽  
Zhenbang Hao ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Point Cloud ◽  
Forest Canopy ◽  
Estimation Method ◽  
Vertical Direction ◽  
Estimation Accuracy ◽  
3D Point Cloud ◽  
Area Index ◽  
Better Than

As a key canopy structure parameter, the estimation method of the Leaf Area Index (LAI) has always attracted attention. To explore a potential method to estimate forest LAI from 3D point cloud at low cost, we took photos from different angles of the drone and set five schemes (O (0°), T15 (15°), T30 (30°), OT15 (0° and 15°) and OT30 (0° and 30°)), which were used to reconstruct 3D point cloud of forest canopy based on photogrammetry. Subsequently, the LAI values and the leaf area distribution in the vertical direction derived from five schemes were calculated based on the voxelized model. Our results show that the serious lack of leaf area in the middle and lower layers determines that the LAI estimate of O is inaccurate. For oblique photogrammetry, schemes with 30° photos always provided better LAI estimates than schemes with 15° photos (T30 better than T15, OT30 better than OT15), mainly reflected in the lower part of the canopy, which is particularly obvious in low-LAI areas. The overall structure of the single-tilt angle scheme (T15, T30) was relatively complete, but the rough point cloud details could not reflect the actual situation of LAI well. Multi-angle schemes (OT15, OT30) provided excellent leaf area estimation (OT15: R2 = 0.8225, RMSE = 0.3334 m2/m2; OT30: R2 = 0.9119, RMSE = 0.1790 m2/m2). OT30 provided the best LAI estimation accuracy at a sub-voxel size of 0.09 m and the best checkpoint accuracy (OT30: RMSE [H] = 0.2917 m, RMSE [V] = 0.1797 m). The results highlight that coupling oblique photography and nadiral photography can be an effective solution to estimate forest LAI.

Factors affecting interannual variation in growth of western Canadian aspen forests during 1951-2000

2005 ◽  
Vol 35 (3) ◽  
pp. 610-622 ◽  
Author(s):  
EH (Ted) Hogg ◽  
James P Brandt ◽  
B Kochtubajda
Keyword(s):  
Populus Tremuloides ◽  
Interannual Variation ◽  
Regional Scale ◽  
Forest Health ◽  
Basal Area ◽  
Deciduous Tree ◽  
Severe Drought ◽  
Moisture Index ◽  
Canadian Prairies ◽  
The North

Trembling aspen (Populus tremuloides Michx.) is the most important deciduous tree in the North American boreal forest and is also the dominant tree in the aspen parkland zone along the northern edge of the Canadian prairies. Since the 1990s, observations of dieback and reduced growth of aspen forests have led to concerns about the potential impacts of climate change. To address these concerns, a regional-scale study (CIPHA) was established in 2000 that includes annual monitoring of forest health and productivity of 72 aspen stands across the western Canadian interior. Tree-ring analysis was conducted to determine the magnitude and cause of temporal variation in stand growth of aspen at the scale (1800 km × 500 km area) encompassed by this study. The results showed that during 1951–2000 the region's aspen forests underwent several cycles of reduced growth, notably between 1976 and 1981, when mean stand basal area increment decreased by about 50%. Most of the growth variation was explained by interannual variation in a climate moisture index in combination with insect defoliation. The results of the analysis indicate that a major collapse in aspen productivity likely occurred during the severe drought that affected much of the region during 2001–2003.

scholarly journals INVESTIGATION OF FOREST CANOPY DENSITY CHANGES IN HYRCANIAN FOREST RESOURCES DURING 1987 TO 2002 USING REMOTE SENSING TECHNOLOGY

2019 ◽  
Vol XLII-4/W18 ◽  
pp. 1031-1034
Author(s):  
M. Taefi Feijani ◽  
S. Azadnejad ◽  
S. Homayouni ◽  
M. Moradi
Keyword(s):  
Time Series ◽  
Forest Canopy ◽  
Spectral Band ◽  
Mixed Forest ◽  
Canopy Density ◽  
Rate Of Growth ◽  
Sensing Technology ◽  
Forest Canopy Density ◽  
Annual Time Series ◽  
Forest Lands

Abstract. Forest canopy density (FCD) of seventeen protected areas of the Caspian Hyrcanian mixed forest are studied here. A modified version of FCD mapper based on spectral band fusion and customized threshold calibration that is optimized for Hyrcanian forests is used for this purpose. In this project, the results of applying the FCD model on three time series of satellite images have been analysed. This classification is based on the FAO standard and consist of four categories such as no-forest, thin, semi-dense and dense. These images, taken with TM and ETM sensors, belong to three-time series between 1987 and 2002. The results of this study indicate that the rate of growth or destruction of forests has been investigated in the regions. Then, using tables and diagrams of variations, the rate of growth or destruction of forest lands in the corresponding period in each class is determined. The FCD model has the ability to study the canopy loading classes in the annual time series.

Status, diversity and trends of the bird communities in Volcanoes National Park and surrounds, Rwanda

2019 ◽  
Vol 30 (1) ◽  
pp. 1-20 ◽  
Author(s):  
MIA A. DERHÉ ◽  
DEO TUYISINGIZE ◽  
WINNIE ECKARDT ◽  
FAIDA EMMANUEL ◽  
TARA STOINSKI
Keyword(s):  
National Parks ◽  
National Park ◽  
Mixed Forest ◽  
Basal Area ◽  
Bird Community ◽  
Bird Communities ◽  
Population Pressure ◽  
Bird Diversity ◽  
Albertine Rift ◽  
1960S And 1970S

SummaryThe Volcanoes National Park (VNP) in Rwanda, part of the Virunga massif in the Albertine Rift region, boasts some of Rwanda’s best remaining natural vegetation and is home to many endangered and endemic species. The park has suffered from high levels of degradation and destruction, reducing in size by 50% during the 1960s and 1970s, and remains under threat from illegal activities, human population pressure and climate change. This study is the first to investigate the status and trends of bird communities in the VNP, using a multi-year dataset. We use a five-year dataset, totalling over 3,200 point-counts, both within and around the VNP, to assess the conservation value of the VNP for birds in comparison with other national parks and non-protected areas. We assess bird communities and population trends within and around the parks and identify important habitat factors for birds within the VNP. We found that the VNP hosts a unique bird community compared to other localities, with several Albertine Rift endemics and threatened species occurring in the VNP. Hagenia/ Hypericum woodland, herbaceous vegetation, brush ridge and mixed forest host the highest levels of bird diversity in the VNP, whilst the park’s waterbodies provide key habitat for the endangered Albertine Rift endemic Grauer’s Swamp-warbler (Bradypterus graueri). Elevation had a negative effect on bird diversity in the VNP, whilst the basal area of dead trees, Hagenia and vines had a positive effect. Both inside and outside the VNP, there was a significant decline in abundance and species richness over the sampling years; however, we advocate for further monitoring to confirm these trends. Based on our findings, we recommend effective, targeted management of key habitats for birds within the park, including those identified in this study, in order to mitigate bird declines and conserve the unique bird communities in the VNP.

Sign in / Sign up

Export Citation Format

Share Document