Kerri T. Vierling

Lidar: shedding new light on habitat characterization and modeling

Ecologists need data on animal–habitat associations in terrestrial and aquatic environments to design and implement effective conservation strategies. Habitat characteristics used in models typically incorporate (1) field data of limited spatial extent and/or (2) remote sensing data that do not characterize the vertical habitat structure. Remote sensing tools that directly characterize three-dimensional (3-D) habitat structure and that provide data relevant to organism–habitat interactions across a hierarchy of scales promise to improve our understanding of animal–habitat relationships. Laser altimetry, commonly called light detection and ranging (lidar), is a source of geospatial data that can provide fine-grained information about the 3-D structure of ecosystems across broad spatial extents. In this review, we present a brief overview of lidar technology, discuss recent applications of lidar data in investigations of animal–habitat relationships, and propose future applications of this technology to issues of broad species-management and conservation interest.

REPRODUCTIVE SUCCESS OF LEWIS'S WOODPECKER IN BURNED PINE AND COTTONWOOD RIPARIAN FORESTS

Abstract Lewiss Woodpecker (Melanerpes lewis) has been characterized as a “burn specialist” because of its preference for nesting within burned pine forests. No prior study, however, has demonstrated the relative importance of crown-burned forests to this woodpecker species by examining its reproductive success in different forest types. We studied breeding Lewiss Woodpeckers in cottonwood (Populus fremontii) riparian forest patches of Colorado and crown-burned ponderosa pine (Pinus ponderosa) forests of Idaho to compare their reproductive success, productivity, and potential source-sink status in the two forest types. Daily nest survival rates were significantly lower in cottonwood compared to burned pine forests. Nesting success was 46% (n = 65) in cottonwood forests and 78% (n = 283) in burned pine forests. Proportion of nests destroyed by predators was significantly higher in cottonwood forests (34%) compared to burned pine forests (16%). We consistently found crown-burned forests to be potential source habitat, whereas cottonwood riparian sites were more often concluded to be potential sink habitat. Cottonwood riparian forests were surrounded primarily by an agricultural landscape where the composition and abundance of nest predators was likely very different than the predator assemblage occupying a large-scale burn in a relatively natural landscape. Conversion of riparian and adjacent grassland landscapes to agriculture and prevention of wildfire in ponderosa pine forests have likely reduced nesting habitat for this species. Prescribed understory fire is the prevailing management tool for restoring ponderosa pine ecosystems. Conditions created by crown fire may be equally important in maintaining ponderosa pine systems and conserving nesting habitat for the Lewiss Woodpecker. Éxito Reproductivo de Melanerpes lewis en Bosques de Pinos Quemados y Bosques Ribereños de Populus fremontii Resumen. Melanerpes lewis ha sido caracterizado como un “especialista de quemas” porque prefiere anidar en áreas de pinos maduros quemados. Sin embargo, ningún estudio anterior ha demostrado la importancia relativa de los bosques de árboles con copas quemadas para este carpintero examinando su éxito reproductivo en diferentes tipos de bosques. Estudiamos M. lewis reproductivos en parches de bosques ribereños de Populus fremontii en Colorado y bosques de Pinus ponderosa con las copas quemadas en Idaho para comparar su éxito reproductivo, productividad y la condición potencial de fuente-sumidero de los dos tipos de bosques. Las tasas diarias de supervivencia de los nidos fueron significativamente más bajas en los bosques de Populus fremontii que en las áreas de pinos maduros quemados. El éxito de los nidos fue de 46% (n = 65) en los bosques de Populus fremontii y 78% (n = 283) en los bosques de pinos quemados. La proporción de nidos destruídos por depredadores fue signicativamente más alta en los bosques de Populus fremontii (34%) que los bosques de pinos quemados (16%). Encontramos consistentemente que las áreas de pinos con las copas quemadas son potencialmente hábitats fuente mientras que los bosques de Populus fremontii fueron considerados como sumideros potenciales con mayor frecuencia. Los bosques de Populus fremontii estaban rodeados principalmente por un paisaje agrícola donde la composición y la abundancia de los depredadores de nidos eran probablemente muy diferentes de las de un área quemada de gran escala en medio de un paisaje natural. La conversión de paisajes ribereños y de pastizales a áreas agrícolas y la prevención de fuegos naturales en los bosques de P. ponderosa probablemente ha reducido el habitat de anidación de esta especie. El manejo de fuegos planificados en el sotobosque es la técnica más utilizada para reestablecer los ecosistemas de P. ponderosa. Las condiciones creadas por el fuego en las copas de los árboles podrían ser igualmente importante para mantener los sistemas de P. ponderosa, incluyendo la conservación de los hábitats de anidación de M. lewis.

Spinning a laser web: predicting spider distributions using LiDAR

LiDAR remote sensing has been used to examine relationships between vertebrate diversity and environmental characteristics, but its application to invertebrates has been limited. Our objectives were to determine whether LiDAR-derived variables could be used to accurately describe single-species distributions and community characteristics of spiders in remote forested and mountainous terrain. We collected over 5300 spiders across multiple transects in the Bavarian National Park (Germany) using pitfall traps. We examined spider community characteristics (species richness, the Shannon index, the Simpson index, community composition, mean body size, and abundance) and single-species distribution and abundance with LiDAR variables and ground-based measurements. We used the R2 and partial R2 provided by variance partitioning to evaluate the predictive power of LiDAR-derived variables compared to ground measurements for each of the community characteristics. The total adjusted R2 for species richness, the Shannon index, community species composition, and body size had a range of 25-57%. LiDAR variables and ground measurements both contributed >80% to the total predictive power. For species composition, the explained variance was approximately 32%, which was significantly greater than expected by chance. The predictive power of LiDAR-derived variables was comparable or superior to that of the ground-based variables for examinations of single-species distributions, and it explained up to 55% of the variance. The predictability of species distributions was higher for species that had strong associations with shade in open-forest habitats, and this niche position has been well documented across the European continent for spider species. The similar statistical performance between LiDAR and ground-based measures at our field sites indicated that deriving spider community and species distribution information using LiDAR data can provide not only high predictive power at relatively low cost, but may also allow unprecedented mapping of community- and species-level spider information at scales ranging from stands to landscapes. Therefore, LiDAR is a viable tool to assist species-specific conservation as well as broader biodiversity planning efforts not only for a growing list of vertebrates, but for invertebrates as well.

Preburn Characteristics and Woodpecker Use of Burned Coniferous Forests

Abstract Large wildfires are common in many western coniferous forests, and these fires can affect woodpecker reproduction and habitat use. Our objectives were to examine nesting densities, reproductive parameters, and species-specific habitat selection of woodpeckers in a recently burned region of the Black Hills in South Dakota, USA, between 2001 and 2004. Postfire nesting densities were greatest in areas dominated by high prefire canopy cover, and reproductive success averaged >70%. For some species of woodpeckers, factors such as diameter at breast height, burn severity, and distance to unburned patches were important for nest-site selection. Our data indicated that nesting densities of many woodpeckers in the Black Hills were lower than what has been recorded elsewhere following recent, large wildfires in ponderosa pine (Pinus ponderosa) forests. Management activities that simulate mixed-severity fire effects and retain higher numbers of large snags are likely to benefit cavity nesters in this region.

Assessing Biodiversity by Airborne Laser Scanning

Estimating biodiversity in complex habitats, particularly in forests, is still a major challenge for ecologists and conservationists. In ground-breaking work, Robert MacArthur and his colleagues quantified relationships between bird and vertical vegetation diversity, and found that the diversity of vegetation structure strongly influenced bird species diversity. However, they were limited in spatial extent when describing vertical vegetation structure due to the labor-intensive nature of data collection. Current remote sensing techniques, such as LiDAR, can describe ecologically relevant measurements of forest structure across broad extents, and thus, there are increasing efforts to examine relationships between LiDAR-derived data and patterns of animal biodiversity. LiDAR-based data have been utilized for silvicultural assessments for over a decade, but LiDAR use in biodiversity studies is more recent. LiDAR data can assist in the assessment of local animal diversity across taxa, and might assist in larger scale biodiversity assessments in remote and rugged environments. In the following chapter, we first briefly discuss the role of vegetation structure in biodiversity studies, followed by a description of the variables that are most commonly used in biodiversity studies. We then give an overview of biodiversity studies that have utilized LiDAR in forests to date. Although there is a growing body of literature relating LiDAR-derived variables to single species distributions and habitat quality, we focus this chapter solely on studies that address animal species diversity in forested landscapes. We conclude with a discussion of future directions concerning biodiversity assessments in forested systems that might benefit from the use of LiDAR-based data.

Landscape-Scale Attributes of Elk Centers of Activity in the Central Black Hills of South Dakota

Abstract We researched the environmental attributes (n = 28) associated with elk (n = 50) summer range (1 May–30 Sep) in the central Black Hills of South Dakota, USA, during 1998–2001. We defined high-use areas or centers of activity as landscapes underlying large concentrations of elk locations resulting from the shared fidelity of independently moving animals to specific regions on summer range. We divided the study area into 3-km grid cells to represent the distance elk travel in a 24-hour period. We computed mean elevation and slope, proportion and configuration of overstory canopy cover, proportion and configuration of dominant vegetation type, estimated biomass, road density, traffic rate, and amount of habitat not dissected by improved surface roads for each cell. We used a combination of multiple stepwise regression and likelihood ratio tests to develop spatially adjusted models with total number of elk locations per cell as the dependent variable. Environmental attributes varied in their significance based on their availability to different elk subpopulations. Collectively, the number of elk locations was positively associated (model r2 = 0.50, P < 0.001) with elevation, proportion of non–road-dissected habitat, shape complexity of meadows, proportion of forest stands with ≤40% overstory canopy cover, and proportion of aspen (Populus tremuloides). Elk were responsive to a landscape structure emphasizing forage potential, and their selection was based on the composition and pattern of both biotic and abiotic variables. Defining the characteristics of high-use areas allows management to manipulate landscapes so as to contain more of the habitats preferred by elk.

A Practical Sampling Design for Acoustic Surveys of Bats

ABSTRACT Acoustic surveys are widely used for describing bat occurrence and activity patterns and are increasingly important for addressing concerns for habitat management, wind energy, and disease on bat populations. Designing these surveys presents unique challenges, particularly when a probabilistic sample is required for drawing inference to unsampled areas. Sampling frame errors and other logistical constraints often require survey sites to be dropped from the sample and new sites added. Maintaining spatial balance and representativeness of the sample when these changes are made can be problematic. Spatially balanced sampling designs recently developed to support aquatic surveys along rivers provide solutions to a number of practical challenges faced by bat researchers and allow for sample site additions and deletions, support unequal-probability selection of sites, and provide an approximately unbiased local neighborhood-weighted variance estimator that is efficient for spatially structured populations such as is typical for bats. We implemented a spatially balanced design to survey canyon bat (Parastrellus hesperus) activity along a stream network. The spatially balanced design accommodated typical logistical challenges and yielded a 25% smaller estimated standard error for the mean activity level than the usual simple random sampling estimator. Spatially balanced designs have broad application to bat research and monitoring programs and will improve studies relying on model-based inference (e.g., occupancy models) by providing flexibility and protection against violations of the independence assumption, even if design-based estimators are not used. Our approach is scalable and can be used for pre- and post-construction surveys along wind turbine arrays and for regional monitoring programs.

Using satellite and airborne LiDAR to model woodpecker habitat occupancy at the landscape scale.

Incorporating vertical vegetation structure into models of animal distributions can improve understanding of the patterns and processes governing habitat selection. LiDAR can provide such structural information, but these data are typically collected via aircraft and thus are limited in spatial extent. Our objective was to explore the utility of satellite-based LiDAR data from the Geoscience Laser Altimeter System (GLAS) relative to airborne-based LiDAR to model the north Idaho breeding distribution of a forest-dependent ecosystem engineer, the Red-naped sapsucker (Sphyrapicus nuchalis). GLAS data occurred within ca. 64 m diameter ellipses spaced a minimum of 172 m apart, and all occupancy analyses were confined to this grain scale. Using a hierarchical approach, we modeled Red-naped sapsucker occupancy as a function of LiDAR metrics derived from both platforms. Occupancy models based on satellite data were weak, possibly because the data within the GLAS ellipse did not fully represent habitat characteristics important for this species. The most important structural variables influencing Red-naped Sapsucker breeding site selection based on airborne LiDAR data included foliage height diversity, the distance between major strata in the canopy vertical profile, and the vegetation density near the ground. These characteristics are consistent with the diversity of foraging activities exhibited by this species. To our knowledge, this study represents the first to examine the utility of satellite-based LiDAR to model animal distributions. The large area of each GLAS ellipse and the non-contiguous nature of GLAS data may pose significant challenges for wildlife distribution modeling; nevertheless these data can provide useful information on ecosystem vertical structure, particularly in areas of gentle terrain. Additional work is thus warranted to utilize LiDAR datasets collected from both airborne and past and future satellite platforms (e.g. GLAS, and the planned IceSAT2 mission) with the goal of improving wildlife modeling for more locations across the globe.

Assessing the status and trend of bat populations across broad geographic regions with dynamic distribution models

Bats face unprecedented threats from habitat loss, climate change, disease, and wind power development, and populations of many species are in decline. A better ability to quantify bat population status and trend is urgently needed in order to develop effective conservation strategies. We used a Bayesian autoregressive approach to develop dynamic distribution models for Myotis lucifugus, the little brown bat, across a large portion of northwestern USA, using a four-year detection history matrix obtained from a regional monitoring program. This widespread and abundant species has experienced precipitous local population declines in northeastern USA resulting from the novel disease white-nose syndrome, and is facing likely range-wide declines. Our models were temporally dynamic and accounted for imperfect detection. Drawing on species-energy theory, we included measures of net primary productivity (NPP) and forest cover in models, predicting that M. lucifugus occurrence probabilities would covary positively along those gradients. Despite its common status, M. lucifugus was only detected during -50% of the surveys in occupied sample units. The overall naive estimate for the proportion of the study region occupied by the species was 0.69, but after accounting for imperfect detection, this increased to -0.90. Our models provide evidence of an association between NPP and forest cover and M. lucifugus distribution, with implications for the projected effects of accelerated climate change in the region, which include net aridification as snowpack and stream flows decline. Annual turnover, the probability that an occupied sample unit was a newly occupied one, was estimated to be low (-0.04-0.14), resulting in flat trend estimated with relatively high precision (SD = 0.04). We mapped the variation in predicted occurrence probabilities and corresponding prediction uncertainty along the productivity gradient. Our results provide a much needed baseline against which future anticipated declines in M. lucifugus occurrence can be measured. The dynamic distribution modeling approach has broad applicability to regional bat monitoring efforts now underway in several countries and we suggest ways to improve and expand our grid-based monitoring program to gain robust insights into bat population status and trend across large portions of North America.

OLD BURNS AS SOURCE HABITATS FOR LEWIS'S WOODPECKERS BREEDING IN THE BLACK HILLS OF SOUTH DAKOTA

Abstract ABSTRACT Crown-burned pine forests are an important breeding habitat for many cavity-nesting birds, and can serve as a source habitat for some woodpecker species. However, it is unclear if this function continues with postburn succession as predators recolonize burned habitats and snag density declines. Lewiss Woodpeckers (Melanerpes lewis) are considered “burn specialists” and are a species of conservation concern. We monitored Lewiss Woodpeckers nesting in ponderosa pine (Pinus ponderosa) forests to determine the source or sink function of old-burn habitats in the Black Hills of South Dakota (study units burned in 1988 and 1991); concurrently, we examined avian and mammalian predator communities within burned and unburned areas. Between 2002 and 2005 we found 55 Lewiss Woodpecker nests, 51 of which were successful. Using adult and juvenile mortality rates for other melanerpine species taken from the literature, we determined that the old-burn habitats we sampled were acting as sources for Lewiss Woodpeckers. Point counts and tracking tube surveys suggested that both avian and mammalian predators had successfully recolonized these old-burn habitats, as both groups were common in old burns and in unburned forests. The unusually high nesting success of Lewiss Woodpeckers in the Black Hills is likely due to the absence of some common nest predators. While the high success rates might continue, we suggest that the overall contribution of young to the region from these burned sites will decline as suitable habitat components (such as snags) decline with the continuation of postfire succession.