Research
"Look deep into nature,
and then you will understand everything better."
– Albert Einstein
Selected Research
- Monarch Butterfly winter habitat
- Stream Habitat
- Drought and Climate Change
- Climate Change in Montane Ecosystems
- Regional Climate and Productivity in the Central Great Plains
- Canopy Architecture of Boreal Forests
- Seedling Establishment and Regeneration in Rain Forest of Costa Rica
- Mechanical Architecture of Arborescent Rain Forest Palms in Costa Rica
Research Approach
- Conservation Biology
- Sampling Design, Field Measurement, and Monitoring
- Experimental Design
- Habitat Characterization
- Microclimate Measurement and Modeling
- Population Analysis
- Quantitative Analysis
- Geographic Information System (GIS)
- Remote Sensing
- Hemispherical (Fisheye) Photography
- Solar Radiation Maps
- Distributed Sensor Networks (DSNs)
- Climate Change Impacts
Selected Research
Monarch Butterfly Winter Habitat: Each winter monarch butterflies (Danaus plexippus L.) from throughout North America migrate to winter habitat in Mexico and California, where they roost in sites protected from extreme weather. In California dozens of sites support overwintering butterflies from western North America. Responsible protection and management of these sites is critical for the long-term welfare of western monarch butterflies. In collaboration with Dr Stuart Weiss (Creekside Center for Earth Observation), we employ hemispherical photography, stand maps, and meteorological sensors, together with models of site changes over time, to understand Monarch habitat needs. This comprehensive approach enables us to identify, maintain, and restore forest canopy structure that provides suitable overwintering microsites, with respect to solar exposure, temperature, and wind protection.
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Each winter thousands of monarch butterflies aggregate and roost in forest stands protected from extreme weather. |
Upward-looking hemispherical (fisheye) photography under forest stands provides a methodology to characterize canopy geometry, and to calculate solar and wind exposure. |
Stream Habitat: Temperature is a fundamental determinate of habitat suitability for aquatic organisms. Water temperature is determined by a complex interplay of prevailing meteorology, local riparian canopy structure and solar exposure, streambed morphology, and surface and subsurface flow patterns. In collaboration with Dr Stuart Weiss (Creekside Center for Earth Observation), we have developed a methodology for spatial-temporal analysis of stream temperature regimes. Our approach synthesizes long-term records of stream flow and water temperature, meteorology, stream morphology, observed temperature regimes, riparian canopy structure and solar exposure, prediction of temperature regimes, and characterization of species requirements. This approach can be applied to a broad spectrum of streams for habitat assessment, stream conservation, restoration to accommodate diverse habitat needs, and examination of potential impacts of climate change.
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Aquatic organisms such as steelhead trout (Oncorhynchus mykiss) require habitat with specific temperature regimes. (photo by A. Launer) |
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riparian vegetation have markedly different temperature regimes .
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for closed versus open canopy stream reaches.
Drought and Climate Change: Extreme climatologic events, such as droughts, floods, and hurricanes, are projected to increase in frequency and intensity as global warming progresses, leading to unprecedented changes in ecosystem function and new challenges for conservation of biodiversity. Recent protracted drought in southwestern North America together with high temperatures caused subcontinental-scale tree mortality. Reduced soil moisture during the drought weakened natural defenses of piñon pine (Pinus edulis) and led to extensive outbreaks of the naturally occurring pathogen piñon bark beetle (Ips confusus), with more than 90% piñon mortality in many areas. This rapid, widespread mortality will alter ecosystem structure and function for decades. In collaboration with Dr David Breshears (University of Arizona) and other colleagues, we employ regional analysis to quantify relations between climate, seasonal patterns of productivity (phenology), and dieoff using satellite remote sensing and geographic information system (GIS).
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Widespread dieoff of piñon pine (Pinus edulis) at Bandelier National Monument in New Mexico. (photos by C. Allen) |
Map of NDVI deviation, a measure of green (photosynthetic) biomass during the drought, illustrates where mortality was greatest. |
A) Soil moisture, B)remotely sensed Normalized Difference Vegetation Index (NDVI), and C) piñon pine mortality at Mesita del Buey, NM. For each plot, the metric of interest is illustrated with a solid dark line, and the 11-year pre-drought baseline mean (solid gray line) and 95% confidence interval (dashed gray lines and associated gray area) are displayed for reference |
Dieoff of the piñon canopy released resources to the herbaceous understory. Herbaceous plants green up more rapidly in response to precipitation than evergreen trees, resulting in a fundamental shift in the seasonal pattern (phenology) of ecosystem productivity. (photo by P. Rich) |
Climate Change in Montane Ecosystems: Climate change, together with habitat loss/fragmentation and invasion of non-native species, poses profound challenges for conservation in montane ecosystems, with substantial risks to ecosystem integrity and the viability of native species. Global climate change translates locally into corresponding shifts of microclimate gradients, with potential habitat for some species increasing and for others decreasing. For example, distributions of plant species such as big sagebrush (Artemisia tridentata), currently most common in warmer, drier habitat of lower elevations, are expanding in higher elevation microsites as temperature rises. At the same time, populations of higher-elevation species are becoming more fragmented and shifting from south-facing slopes to cooler north-facing slopes. Microclimate shifts also cause additional non-linear, cross-scale changes in processes such as fire cycles and pathogen outbreaks. In collaboration with Dr Pinde Fu (ESRI) and other colleagues, we evaluate shifts in microclimate (temperature, precipitation, solar exposure, soil moisture, etc.) and predict associated shifts in distribution of native species based on field measurements and map-based models of likely climate change scenarios.
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Vegetation at timberline near Rocky Mountain Biological Laboratory (RMBL) in Colorado. |
Average diurnal microclimate records for RMBL. |
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Insolation models for the vicinity of RMBL. |
Upward-looking hemispherical photographs of topographic influences on insolation. |
Energy Balance Components: shortwave radiation (SW), longwave radiation (LW), sensible heat (H), latent energy (LE), and storage (G). |
Regional Climate and Productivity in the Central Great Plains: Normalized Difference Vegetation Index (NDVI ) has proven to be a robust indicator of terrestrial vegetation productivity. Among climatic factors, precipitation and temperature strongly influence both temporal and spatial patterns of NDVI. The relationship between precipitation and NDVI is strong and predictable when viewed at the appropriate temporal and spatial scale, and with appropriate lags. Most tree productivity measurements (tree ring size, tree diameter growth, and seed production) are strongly correlated with NDVI integrated for a period during the early growing season; foliage production is most strongly correlated with NDVI integrated over the entire growing season; and tree height growth corresponds with NDVI integrate during the previous growing season. Similarly, productivity measurements for herbaceous plants (grassland biomass and crop yield) are strongly correlated with NDVI. The strong relationships between NDVI and productivity, and between precipitation and NDVI, along with detailed analysis of the temporal and spatial patterns for our study region, provides the basis for prediction of productivity at landscape scales under different climate regimes. (with Jue Wang, KU PhD Dissertation Research)
Canopy Architecture of Boreal Forests: Hemispherical photography and mapped forest plots were used to characterize forest canopy architecture as part of the Boreal Ecosystem Atmosphere Studies (BOREAS) Experiment in northern Canada. (with Richard Fournier).
Seedling Establishment and Regeneration in Rain Forest of Costa Rica: Light is a key resource controlling tree regeneration in the understory of closed-canopy old-growth forests. Comparing the landscape-scale distribution of key resources with species' actual distributions at similar scales offers a quantitative method for assessing plant life histories within and among forests. (with Deborah A. Clark, David B. Clark, and Stephen Oberbauer).
Mechanical Architecture of Arborescent Rain Forest Palms in Costa Rica: Mechanical architecture refers to the morphological basis of mechanical support in plants. Ecological and developmental studies of arborescent palms in the lowland rain forest of Costa Rica were focused on the mechanical architecture that enables palms to grow to tree stature and changes in stem structure that accompany height growth. Palms have evolved a means for attaining tree stature that is distinct from that of arborescent dicotyledons and conifers. Arborescent palms maintain a margin of safety against elastic buckling during height growth by various combinations of 1) initiation of height growth with a stem diameter that is sufficient for future support requirements, 2) increase in stem diameter by means of sustained cell expansion, and 3) increase in stiffness and strength of stem tissue by means of sustained lignification. (Paul Rich Harvard PhD Dissertation Research).
Research Approach
Conservation biology is the scientific study of protection of Earth’s biodiversity and natural resources. The goals of conservation biology are twofold: 1) to understand effects of human activities on organisms, communities, and ecosystems; and 2) to develop practical science-based approaches to protect and restore ecosystem health.
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| Populations of the threatened Bay Checkerspot butterfly (Euphydryas editha bayensis) have declined severely since the 1980s, with local extinctions and restriction to small habitat islands (photo by S. Weiss). |
Sampling Design, Field Measurement, and Monitoring: Understanding the structure and function of the natural world requires sampling designs that rigorously characterize key environmental factors while minimizing time, effort, and cost. Field measurement based on such sampling designs employs standard and custom techniques (e.g. quadrats and transects), specialized field instruments (e.g. hemispherical photography and temperature sensors), along with systematic qualitative and quantitative observations. Monitoring with repeated field sampling enables assessment of ecological changes with time.
Experimental Design: Modern science is founded in keen observation of natural phenomena coupled with testing of hypotheses using sound experimental design. An experiment tests the effect of one or more treatments, in which a single factor is varied and compared with a control. Ecological experiments are challenging because of the complexity and the large spatial and temporal domains of natural systems. We combine observational studies with experiments to test effects of environmental variables. We also make use of "natural experiments", wherein we identify locations in nature where key differences in conditions can serve as experimental treatments.
Habitat Characterization: Habitat is the natural environment where a particular plant or animal is able to thrive. Habitat characterization requires comprehensive understanding of the physical conditions and biological needs of the organism of interest. For plants this can include microclimate conditions (temperature, precipitation, solar radiation, etc.), soil, nutrient levels, water availability, and interactions with other organisms (competition, herbivory, pollination, etc.). Similarly, for animals this can include microclimate conditions, food, water, shelter, and interactions with other organisms (competitors, predators, pathogens, etc.).
Microclimate Measurement and Modeling: Microclimate, local atmospheric conditions, such as temperature, precipitation, and incoming solar radiation (insolation), is a fundamental determinant of habitat suitability. Gradients of microclimate, with marked variation over short distances, can be characterized by a combination of sensor measurements and GIS-based models, and in turn related to ecological processes. Among the challenges are understanding how prevailing climate and microclimate regimes are influenced by topography, water bodies, local energy balance, vegetation cover, and local air/water flow patterns. We have pioneered the use of solar radiation mapping tools, topoclimate models, distributed sensor networks (DSNs), prediction of microclimate shifts resulting from climate change, and conservation management practices based on the ecological ramifications of microclimate.
Population Analysis: Population analysis applies the principles of population biology to examine the status of native and nonnative populations and how they change through time. Comprehensive analysis requires understanding the environmental factors and feedbacks that affect population size, as well as rigorous application of demography, which focuses on age- or size-class dependent recruitment, mortality, and migration.
Quantitative Analysis: Quantitative analysis, as applied for ecological research, enables rigorous interpretation of data concerning natural ecosystem structure and processes. This includes quantitative summaries concerning data (descriptive statistics), hypothesis testing about patterns and processes based on samples and probability distributions (inferential statistics), and interpolation/extrapolation of spatial and temporal patterns based on limited samples (geostatistics).
Geographic Information System (GIS): GIS provides tools to organize, analyze, and display geospatial information. The technology integrates database operations such as query and statistical analysis with geographic analysis, modeling, and mapping capabilities. The flexibility and capabilities of a GIS come from its ability to store geographic information as interactive map layers that can be overlaid and related for advanced visualization and analysis.
The overlay of map layers in a GIS
enable powerful geospatial analysis
and display (courtesy of ESRI).
Remote Sensing: Remote sensing, using visible and multispectral images obtained from satellite- or aircraft-mounted sensor arrays, is increasingly used to analyze land cover and ecological processes. Measurement and monitoring with remote sensing has the advantage of allowing noninvasive data collection over large spatial areas, with repeated sampling over time and ready comparison with other geographic areas.
Hemispherical (Fisheye) Photography: Hemispherical photography, also known as canopy or fisheye photography, is a powerful technique for calculating light regimes under plant canopies and for assessing canopy structure. Hemiphotos are acquired using a camera fitted with a special wide-angle lens pointed upwards, providing a 180 degree (hemispherical) view. The resulting circular images depict the zenith at the center and the horizons at the edges. Using computer image analysis tools we are able to calculate the direct and diffuse light that penetrates through canopy openings. We can also estimate properties of the canopy itself, such as leaf area index (the area of foliage per unit ground area).
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Hemispherical photographs being acquired to assess conditions for grape ripening in vineyards (photo by S. Weiss). |
Hemispherical photograph used to study microclimate of winter roosting habitat at the Monarch Butterfly Biosphere Reserve, Mexico (photo by S. Weiss). |
Solar Radiation Models: Solar radiation maps depict the geographic distribution of incoming solar radiation (insolation), fundamental for a multitude of physical and biological processes on Earth. Typically, a digital elevation model (DEM) is used as input to calculate solar radiation maps. Solar radiation models account for latitude as it influences solar angles, atmospheric conditions, and three main local geometric effects: 1) elevation, which determines the amount of atmosphere through which solar radiation must pass; 2) surface orientation, which determines angle of incidence; and 3) topographic obstruction, which blocks insolation from certain sky directions.
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GIS-based tools such as Solar Analyst and ArcGIS Solar Radiation Tools, enable calculation and analysis of solar radiation maps using DEMs for input. |
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Analysis of topographic influence on vegetation patterns at Big Creek Reserve, CA, use A) the DEM as input to calculate solar radiation maps for the B) summer solstice, C) equinox, and D) winter solstice, and relations with E) vegetation distribution (from Rich 2000). |
Distributed Sensor Networks (DSNs): DSNs are revolutionizing the way we sense the natural and human environment by expanding our ability to collect information over a wide range of spatial and temporal scales and with high local accuracy. DSNs consist of a large number of small, independent sensors, each of which is capable of reading and storing one or more environmental variables such as temperature. To be effective, sensors must be inexpensive, low-maintenance, low in power consumption, and noninvasive. Deployment of DSNs allows us to address long-standing problems in ecology and conservation biology.
Climate Change Simulation: As the result of anthropogenic increases of atmospheric carbon dioxide from burning fossil fuels, along with release of other greenhouse gases, the climate of the Earth is becoming markedly warmer. Widespread climate change is causing associated far-reaching ecological changes that affect all aspects of conservation, including shifts in habitat distribution, population dynamics, and biogeochemical cycling. Map-based climate models enable examination of shifts in microclimate as they relate to changes in habitat distribution, associated species composition, and ecosystem dynamics.
PMR /na /kab /arc