John F. Weishampel

Estimation of tropical forest structural characteristics using large-footprint lidar

Quantification of forest structure is important for developing a better understanding of how forest ecosystems function. Additionally, estimation of forest structural attributes, such as aboveground biomass (AGBM), is an important step in identifying the amount of carbon in terrestrial vegetation pools and is central to global carbon cycle studies. Although current remote sensing techniques recover such tropical forest structure poorly, new large-footprint lidar instruments show great promise. As part of a prelaunch validation plan for the Vegetation Canopy Lidar (VCL) mission, the Laser Vegetation Imaging Sensor (LVIS), a large-footprint airborne scanning lidar, was flown over the La Selva Biological Station, a tropical wet forest site in Costa Rica. The primary objective of this study was to test the ability of large-footprint lidar instruments to recover forest structural characteristics across a spectrum of land cover types from pasture to secondary and primary tropical forests. LVIS metrics were able to predict field-derived quadratic mean stem diameter (QMSD), basal area, and AGBM with R 2 values of up to .93, .72, and .93, respectively. These relationships were significant and nonasymptotic through the entire range of conditions sampled at the La Selva. Our results confirm the ability of large-footprint lidar instruments to estimate important structural attributes, including biomass in dense tropical forests, and when taken along with similar results from studies in temperate forests, strongly validate the VCL mission framework. D 2002 Elsevier Science Inc. All rights reserved.

Imaging radar for ecosystem studies

Recently a number of satellites have been launched with radar sensors, thus expanding opportunities for global assessment. In this article we focus on the applications of imaging radar, which is a type of sensor that actively generates pulses of microwaves and, in the interval between sending pulses, records the returning signals reflected back to an antenna.

Geospatial revolution and remote sensing LiDAR in Mesoamerican archaeology

The application of light detection and ranging (LiDAR), a laser-based remote-sensing technology that is capable of penetrating overlying vegetation and forest canopies, is generating a fundamental shift in Mesoamerican archaeology and has the potential to transform research in forested areas world-wide. Much as radiocarbon dating that half a century ago moved archaeology forward by grounding archaeological remains in time, LiDAR is proving to be a catalyst for an improved spatial understanding of the past. With LiDAR, ancient societies can be contextualized within a fully defined landscape. Interpretations about the scale and organization of densely forested sites no longer are constrained by sample size, as they were when mapping required laborious on-ground survey. The ability to articulate ancient landscapes fully permits a better understanding of the complexity of ancient Mesoamerican urbanism and also aids in modern conservation efforts. The importance of this geospatial innovation is demonstrated with newly acquired LiDAR data from the archaeological sites of Caracol, Cayo, Belize and Angamuco, Michoacán, Mexico. These data illustrate the potential of technology to act as a catalytic enabler of rapid transformational change in archaeological research and interpretation and also underscore the value of on-the-ground archaeological investigation in validating and contextualizing results.

Volumetric lidar return patterns from an old-growth tropical rainforest canopy

Rainforests represent the epitome of structural complexity in terrestrial ecosystems. However, measures of three-dimensional canopy structure are limited to a few areas typically < 1 ha with construction crane or walkway/platform access. An innovative laser profiling system, the Laser Vegetation Imaging Sensor (LVIS), was used to map canopy structure (i.e. based on height and vertical distribution of laser returns) of a tropical rainforest in Costa Rica. Within a 1km2 area of mature rainforest, canopy top height ranged from 8.4 to 51.6m based on the altimeter measures. The laser return density was most concentrated in the horizontal layer located 20-30m above the ground. Spatial patterns of the return were found to be isotropic based on north-south versus east-west vertical return profiles and exhibited properties of self-similarity.

Forest biomass from combined ecosystem and radar backscatter modeling

Abstract Above-ground woody biomass is an important parameter for describing the function and productivity of forested ecosystems. Recent studies have demonstrated that synthetic aperture radar (SAR) can be used to estimate above-ground standing biomass. To date, these studies have relied on extensive ground-truth measurements to construct relationships between biomass and SAR backscatter. In this article we discuss the use of models to help develop a relationship between biomass and radar backscatter and compare the predictions with measurements. A gap-type forest succession model was used to simulate growth and development of a northern hardwood-boreal transitional forest typical of central Maine, USA. Model results of species, and bole diameter at breast height (dbh) of individual trees in a 900 m 2 stand were used to run discontinuous canopy backscatter models to determine radar backscatter coefficients for a wide range of simulated forest stands. Using model results, relationships of copolarized backscatter to forest biomass were developed and applied to airborne SAR (AIRSAR) image over a forested area in Maine. A relationship derived totally from model results was found to underestimate biomass. Calibrating the modeled backscatter with limited AIRSAR backscatter measurements improved the biomass estimation when compared to field measurements. The approach of using a combination of forest succession and remote sensing models to develop algorithms for inferring forest attributes produced comparable results with techniques using only measurements. Applying the model derived algorithm to SAR imagery produced reasonable results when mapped biomass was limited to 15 kg/m 2 or less.

Spatiotemporal patterns of annual sea turtle nesting behaviors along an East Central Florida beach

Abstract The Florida coastline from Melbourne Beach to Wabasso Beach is one the most important nesting areas for loggerhead turtles ( Caretta caretta ) in the Western Hemisphere and for green turtles ( Chelonia mydas ) in the United States. In this study, we quantified the spatial patterns of numerous loggerhead ( N ≈400,000) and green turtle ( N ≈14,000) and less numerous ( N ≈100) leatherback ( Dermochelys coriacea ) beach ascents from 1989–1999 in terms of their autocorrelative properties along 40.5 km within this critical reproductive zone. Nesting and non-nesting emergence patterns of loggerhead and green turtles were non-random, favoring the southern half of the study area. Perhaps due to low numbers or differences in nesting behavior, leatherback nest distributions were not significantly different from random. Loggerhead and green turtle nest locations exhibited similar clinal patterns. They were positively autocorrelated at distances less than 10 km and negatively at distances greater than 30 km. These patterns were significantly correlated interannually.

Multifractal analysis of canopy height measures in a longleaf pine savanna

Spatial patterns of forest canopies are fractal as they exhibit variation over a continuum of scales. A measure of fractal dimension of a forested landscape represents the spatial summation of physiologic (leaf-level), demographic (populationlevel), and abiotic (e.g., edaphic) processes, as well as exogenous disturbances (e.g., fire and hurricane) and thus provides a basis to classify or monitor such systems. However, forests typically exhibit a spectrum of fractal parameters which yields further insight to the geometric structure of the system and potentially the underlying processes. We calculated multifractal properties of longleaf pine flatwoods, the predominant ecosystem of central Florida, from canopy profile data derived from an airborne laser altimeter and ground-based measurements in The Nature Conservancy’s Disney Wilderness Preserve located near Kissimmee, Florida. These metrics were compared for six 500 m transects to determine the level of consistency between remotely sensed and field measures and within a forest community. Multifractal techniques uncovered subtle differences between transects that could correspond to unique, underlying abiotic and biotic processes. These techniques should be considered a valuable tool for ecological analysis. # 2000 Elsevier Science B.V. All rights reserved.

Inferring foraging areas of nesting loggerhead turtles using satellite telemetry and stable isotopes.

In recent years, the use of intrinsic markers such as stable isotopes to link breeding and foraging grounds of migratory species has increased. Nevertheless, several assumptions still must be tested to interpret isotopic patterns found in the marine realm. We used a combination of satellite telemetry and stable isotope analysis to (i) identify key foraging grounds used by female loggerheads nesting in Florida and (ii) examine the relationship between stable isotope ratios and post-nesting migration destinations. We collected tissue samples for stable isotope analysis from 14 females equipped with satellite tags and an additional 57 untracked nesting females. Telemetry identified three post-nesting migratory pathways and associated non-breeding foraging grounds: (1) a seasonal continental shelf–constrained migratory pattern along the northeast U.S. coastline, (2) a non-breeding residency in southern foraging areas and (3) a residency in the waters adjacent to the breeding area. Isotopic variability in both δ13C and δ15N among individuals allowed identification of three distinct foraging aggregations. We used discriminant function analysis to examine how well δ13C and δ15N predict female post-nesting migration destination. The discriminant analysis classified correctly the foraging ground used for all but one individual and was used to predict putative feeding areas of untracked turtles. We provide the first documentation that the continental shelf of the Mid- and South Atlantic Bights are prime foraging areas for a large number (61%) of adult female loggerheads from the largest loggerhead nesting population in the western hemisphere and the second largest in the world. Our findings offer insights for future management efforts and suggest that this technique can be used to infer foraging strategies and residence areas in lieu of more expensive satellite telemetry, enabling sample sizes that are more representative at the population level.

Ancient Maya Regional Settlement and Inter-Site Analysis: The 2013 West-Central Belize LiDAR Survey

During April and May 2013, a total of 1057 km2 of LiDAR was flown by NCALM for a consortium of archaeologists working in West-central Belize, making this the largest surveyed area within the Mayan lowlands. Encompassing the Belize Valley and the Vaca Plateau, West-central Belize is one of the most actively researched parts of the Maya lowlands; however, until this effort, no comprehensive survey connecting all settlement had been conducted. Archaeological projects have investigated at least 18 different sites within this region. Thus, a large body of archaeological research provides both the temporal and spatial parameters for the varied ancient Maya centers that once occupied this area; importantly, these data can be used to help interpret the collected LiDAR data. The goal of the 2013 LiDAR campaign was to gain information on the distribution of ancient Maya settlement and sites on the landscape and, particularly, to determine how the landscape was used between known centers. The data that were acquired through the 2013 LiDAR campaign have significance for interpreting both the composition and limits of ancient Maya political units. This paper presents the initial results of these new data and suggests a developmental model for ancient Maya polities.

DUNE VEGETATION FERTILIZATION BY NESTING SEA TURTLES

Sea turtle nesting presents a potential pathway to subsidize nutrient-poor dune ecosystems, which provide the nesting habitat for sea turtles. To assess whether this positive feedback between dune plants and turtle nests exists, we measured N concentration and delta15N values in dune soils, leaves from a common dune plant (sea oats [Uniola paniculata]), and addled eggs of loggerhead (Caretta caretta) and green turtles (Chelonia mydas) across a nesting gradient (200-1050 nests/km) along a 40.5-km stretch of beach in east central Florida, USA. The delta15N levels were higher in loggerhead than green turtle eggs, denoting the higher trophic level of loggerhead turtles. Soil N concentration and delta15N values were both positively correlated to turtle nest density. Sea oat leaf tissue delta15N was also positively correlated to nest density, indicating an increased use of augmented marine-based nutrient sources. Foliar N concentration was correlated with delta15N, suggesting that increased nutrient availability from this biogenic vector may enhance the vigor of dune vegetation, promoting dune stabilization and preserving sea turtle nesting habitat.