The Use of the Land Survey Record to Assess Changes in Vegetation Structure. A Case Study From the Darling Downs, Queensland, Australia.

1998 ◽  
Vol 20 (1) ◽  
pp. 132 ◽  
Author(s):  
RJ Fensham ◽  
JE Holman
Keyword(s):  
Vegetation Structure ◽  
Canopy Cover ◽  
Vegetation Density ◽  
Crown Cover ◽  
Standard Application ◽  
Land Survey ◽  
Minor Vegetation ◽  
Structural Category ◽  
Historical Photographs

Fifteen references to vegetation structure from the historical land survey record for the eastern Darling Downs were calibrated with historical photographs to determine the use of the surveyors' structural terminology (Open: 'open', 'light': Dense: 'heavy', 'thick', 'dense'). Sites with less than 40% canopy cover were only described by terms included within the Open category, and sites with greater than 50% canopy cover were only described by terms included within the Dense category. These results provide calibrations of the surveyors' structural terminology indicating terms were unambiguously applied outside the 40-50% canopy cover range. The use of corner tree distances as an absolute measure of vegetation density is warned against because corner trees had to meet certain criteria and were not necessarily the nearest tree to any corner. However, the distance from allotment corners to "corner trees" provided a measure of the relative use of the surveyor's structural epithets and is consistent with standard application among their fraternity. Survey records dating from 1864-1910 were compared with the structure of existing remnants (projective crown cover measured from recent 1:25,000 aerial photography) to assess changes in vegetation structure. The analysis suggests that 88% of the 34 sites included in the analysis have not changed from the broad structural category that was assigned by the surveyors. Using the assumptions developed by this study, two sites were assessed as having thickened substantially. These results suggest that only minor vegetation thickening has occurred in the Darling Downs since the early land surveys. This conclusion is supported by direct comparison of the historical photographs with existing remnants. indicating that only one site out of 17 has thickened substantially.

scholarly journals Leveraging TLS as a Calibration and Validation Tool for MLS and ULS Mapping of Savanna Structure and Biomass at Landscape-Scales

2021 ◽  
Vol 13 (2) ◽  
pp. 257 ◽  
Author(s):  
Shaun R. Levick ◽  
Tim Whiteside ◽  
David A. Loewensteiner ◽  
Mitchel Rudge ◽  
Renee Bartolo
Keyword(s):  
Remote Sensing ◽  
Vegetation Structure ◽  
Laser Scanning ◽  
Canopy Cover ◽  
Structural Diversity ◽  
Point Clouds ◽  
Large Area ◽  
Calibration And Validation ◽  
Savanna Vegetation ◽  
Landscape Scales

Savanna ecosystems are challenging to map and monitor as their vegetation is highly dynamic in space and time. Understanding the structural diversity and biomass distribution of savanna vegetation requires high-resolution measurements over large areas and at regular time intervals. These requirements cannot currently be met through field-based inventories nor spaceborne satellite remote sensing alone. UAV-based remote sensing offers potential as an intermediate scaling tool, providing acquisition flexibility and cost-effectiveness. Yet despite the increased availability of lightweight LiDAR payloads, the suitability of UAV-based LiDAR for mapping and monitoring savanna 3D vegetation structure is not well established. We mapped a 1 ha savanna plot with terrestrial-, mobile- and UAV-based laser scanning (TLS, MLS, and ULS), in conjunction with a traditional field-based inventory (n = 572 stems > 0.03 m). We treated the TLS dataset as the gold standard against which we evaluated the degree of complementarity and divergence of structural metrics from MLS and ULS. Sensitivity analysis showed that MLS and ULS canopy height models (CHMs) did not differ significantly from TLS-derived models at spatial resolutions greater than 2 m and 4 m respectively. Statistical comparison of the resulting point clouds showed minor over- and under-estimation of woody canopy cover by MLS and ULS, respectively. Individual stem locations and DBH measurements from the field inventory were well replicated by the TLS survey (R2 = 0.89, RMSE = 0.024 m), which estimated above-ground woody biomass to be 7% greater than field-inventory estimates (44.21 Mg ha−1 vs 41.08 Mg ha−1). Stem DBH could not be reliably estimated directly from the MLS or ULS, nor indirectly through allometric scaling with crown attributes (R2 = 0.36, RMSE = 0.075 m). MLS and ULS show strong potential for providing rapid and larger area capture of savanna vegetation structure at resolutions suitable for many ecological investigations; however, our results underscore the necessity of nesting TLS sampling within these surveys to quantify uncertainty. Complementing large area MLS and ULS surveys with TLS sampling will expand our options for the calibration and validation of multiple spaceborne LiDAR, SAR, and optical missions.

scholarly journals A virtual diorama. Mapping archives in situ at places of cultural significance

1970 ◽  
pp. 22-36
Author(s):  
Jonathan Westin ◽  
Gunnar Almevik
Keyword(s):  
Spatial Information ◽  
Three Dimensional ◽  
Physical Space ◽  
Cultural Significance ◽  
Dimensional Reconstruction ◽  
Historical Photographs ◽  
New Applications ◽  
Archive Material

Using the wooden church of Södra Råda as a case study, this article concerns new applications of technology to contextualise and activate archive material in situ at places of cultural significance. Using a combination of augmented reality and virtual reality, we describe a process of turning historical photographs and two-dimensional reconstruction drawings into three-dimensional virtual models that can be lined up to a physical space. The leading questions for our investigation concern how archive material can be contextualised, and how the result may be made accessible in situ and contribute to place development. The result of this research suggests possibilities for using historical photographs to faithfully reconstruct lost historical spaces as three-dimensional surfaces that contextualise documentation and offer spatial information.

An improved hazard assessment chart for rock falls in near vertical blocky rock environments

2021 ◽  
Author(s):  
Fhatuwani Sengani ◽  
Mulenga Francois
Keyword(s):  
Slope Angle ◽  
Vegetation Density ◽  
Rock Falls ◽  
Structural Mapping ◽  
Initial Height ◽  
Rockfall Hazard ◽  
Final Destination ◽  
Bedding Planes ◽  
Hazard Rating

Abstract The purpose of the study was to perform rockfall stability analysis and develop an improved rockfall hazard matrix chart using the R518 road in Limpopo as the case study. The study entailed structural mapping, wedge simulation using stereonet plots. The RocFall software was then used to identify the parameters that influence the occurrence of rockfall. The software was also used to monitor the variations in the kinetic energy of rolling, bouncing or falling rocks. The effects of the initial height and velocity of falling rocks on the final destination of fragments were also explored. Results showed that the selected area along the R518 road consists of joints and bedding planes. These features weaken the rock mass and create wedges that can potentially fall. Simulations with RocFall, on the other hand, indicated that slope height, vegetation density, slope angle, the velocity of the falling rock largely contribute to the extent that the broken rock could reach. From the empirical and numerical findings, an improved rockfall hazard rating chart was proposed. The chart was found to be suitable for the rating of level of rockfall hazard along highways and roads.

scholarly journals Estimation of crown and canopy cover from airborne lidar data

2010 ◽  
Vol 52 (1) ◽  
pp. 5-17 ◽  
Author(s):  
Mait Lang
Keyword(s):  
Norway Spruce ◽  
Scots Pine ◽  
Stand Structure ◽  
Canopy Cover ◽  
Airborne Lidar ◽  
Silver Birch ◽  
Lidar Data ◽  
Crown Cover ◽  
Pine Trees ◽  
Airborne Lidar Data

Metsa katvuse ja liituse hindamine lennukilt laserskanneriga Tests were carried out in mature Scots pine, Norway spruce and Silver birch stands at Järvselja, Estonia, to estimate canopy cover (K) and crown cover (L) from airborne lidar data. Independent estimates Kc and Lc for K and L were calculated from the Cajanus tube readings made on the ground at 1.3 m height. Lidar data based cover estimates depended on the inclusion of different order returns significantly. In all the stands first order return based estimate K1 was biased positively (3-10%) at the reference height of 1.3 m compared to ground measurements. All lidar based estimates decreased with increasing the reference height. Single return (Ky) and all return (Kk) based canopy cover estimates depended more on the sand structure compared to K1. The ratio of all return count to the first return count D behaved like crown cover estimate in all stands. However, in spruce stand D understimated Lc significantly. In the Scots pine stand K1(1.3) = 0.7431 was most similar canopy cover estimate relative to the ground estimate Kc = 0,7362 whereas Ky(1.3) and Kk(1.3) gave significant underestimates (>15%) of K. Caused by the simple structure of Scots pine stand - only one layer pine trees, the Cajanus tube based canopy cover (Kc), crown cover (Lc) and lidar data based canopy density D(1.3) values were rather similar. In the Norway spruce stand and in the Silver birch stand second layer and regeneration trees were present. In the Silver birch stand Kk(1.3) and Ky(1.3) estimated Kc rather well. In the Norway spruce stand Ky(1.3) and K1(1.3) were the best estimators of Kc whereas Kk(1.3) underestimated canopy cover. Lidar data were found to be usable for canopy cover and crown cover assessment but the selection of the estimator is not trivial and depends on the stand structure.

scholarly journals How Surface Radiation on Forested Snowpack Changes across a Latitudinal Gradient

Hydrology ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 62 ◽  
Author(s):  
Bijan Seyednasrollah ◽  
Mukesh Kumar
Keyword(s):  
Picea Glauca ◽  
Forest Floor ◽  
Latitudinal Gradient ◽  
Geographical Location ◽  
Canopy Cover ◽  
Surface Radiation ◽  
Net Radiation ◽  
Vegetation Density ◽  
Clear Sky ◽  
Sky Conditions

Radiation is the major driver of snowmelt, and, hence, its estimation is critically important. Net radiation reaching the forest floor is influenced by vegetation density. Previous studies in mid-latitude conifer forests have confirmed that net radiation decreases and then subsequently increases with increasing vegetation density, for clear sky conditions. This leads to the existence of a net radiation minimum at an intermediate vegetation density. With increasing cloud cover, the minimum radiation shifts toward lower densities, sometimes resulting in a monotonically increasing radiation with vegetation density. The net radiation trend, however, is expected to change across sites, affecting the magnitude and timing of individual radiation components. This research explores the variability of net radiation on a snow-covered forest floor for different vegetation densities along a latitudinal gradient. We especially investigate how the magnitude of minimum/maximum radiation and the corresponding vegetation density change with the site geographical location. To evaluate these, the net radiation is evaluated using the Forest Radiation Model at six different locations in predominantly white spruce (Picea glauca) canopy cover across North America, ranging from 45 to 66° N latitudes. Results show that the variation of net radiation with vegetation density considerably varies with latitude. In higher latitude forests, the magnitude of net radiation is generally smaller, and the minimum radiation is exhibited at relatively sparser vegetation densities, under clear sky conditions. For interspersed cloudy sky conditions, net radiation non-monotonically varies with latitude across the sites, depending on the seasonal sky cloudiness and air temperature. The latitudinal sensitivity of net radiation is lower on north-facing hillslopes than on south-facing sites.

scholarly journals Rapid response of habitat structure and above-ground carbon storage to altered fire regimes in tropical savanna

2019 ◽  
Vol 16 (7) ◽  
pp. 1493-1503 ◽  
Author(s):  
Shaun R. Levick ◽  
Anna E. Richards ◽  
Garry D. Cook ◽  
Jon Schatz ◽  
Marcus Guderle ◽  
...  
Keyword(s):  
Carbon Storage ◽  
Vegetation Structure ◽  
Habitat Structure ◽  
Canopy Structure ◽  
Three Dimensional ◽  
Canopy Cover ◽  
Fire Regimes ◽  
Dry Season ◽  
Airborne Lidar ◽  
Climate Conditions

Abstract. Fire regimes across the globe have been altered through changes in land use, land management, and climate conditions. Understanding how these modified fire regimes impact vegetation structure and dynamics is essential for informed biodiversity conservation and carbon management in savanna ecosystems. We used a fire experiment at the Territory Wildlife Park (TWP), northern Australia, to investigate the consequences of altered fire regimes for vertical habitat structure and above-ground carbon storage. We mapped vegetation three-dimensional (3-D) structure in high spatial resolution with airborne lidar across 18 replicated 1 ha plots of varying fire frequency and season treatments. We used lidar-derived canopy height and cover metrics to extrapolate field-based measures of woody biomass to the full extent of the experimental site (R2=0.82, RMSE = 7.35 t C ha−1) and analysed differences in above-ground carbon storage and canopy structure among treatments. Woody canopy cover and biomass were highest in the absence of fire (76 % and 39.8 t C ha−1) and lowest in plots burnt late in the dry season on a biennial basis (42 % and 18.2 t C ha−1). Woody canopy vertical profiles differed among all six fire treatments, with the greatest divergence in height classes <5 m. The magnitude of fire effects on vegetation structure varied along the environmental gradient underpinning the experiment, with less reduction in biomass in plots with deeper soils. Our results highlight the large extent to which fire management can shape woody structural patterns in savanna landscapes, even over time frames as short as a decade. The structural profile changes shown here, and the quantification of carbon reduction under late dry season burning, have important implications for habitat conservation, carbon sequestration, and emission reduction initiatives in the region.

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