Airborne imaging spectroscopy covering wavelength range of 0.35-2.5 μm can be used to quantify soil textural properties and chemical constituents. In this paper, we evaluate the effects of spatial resolution on the quantification of soil constituents using a lasso algorithm-based ensemble bootstrapping framework. Airborne visible infrared imaging spectrometer data collected at 7.6 m resolution over Bird's Point New Madrid (BPNM) floodway in Missouri, USA, is upscaled using a spatial filter to simulate a satellite-based sensor and generate multiple coarser resolution datasets, including the originally proposed 60.8 m hyperspectral infrared imager like data. The simulated data at multiple spatial resolutions are used in an ensemble lasso algorithm-based modeling framework for developing quantitative prediction models and spatial mapping of the soil constituents. We outline an evaluation framework with a set of metrics that considers the point-scale model performance as well as the consistency of cross-scale spatial predictions. The model results demonstrate that the ensemble quantification method is scalable, and further the model structure indicates the persistence of important spectral features across spatial resolutions. The probability density functions of the constituents over the BPNM landscape show that it is similar for multiple spatial resolutions. Finally, a comparison of the model predictions with statistical central values together with the within pixel variance across fine to coarse resolutions indicate that the model accurately captures the median values of the fine subgrid that the coarse-resolution data is composed of. This study establishes the feasibility for quantifying soil constituents from space-borne hyperspectral sensors.
We present an approach to mapping surface waters at local to global scales. In prior research we demonstrated that wide angle remotely sensed imagery having high radiance values measured near the direction of the sun glint in the principal plane signaled the presence of either open water or inundated plant communities, in contrast to dry upland plant communities. We demonstrated that regional to global scale wetlands issues that do not involve one meter resolution per se may be addressed with acceptable accuracy by applying spectral mixture analysis (SMA) and atmospheric correction techniques to the 6-10 km pixel imagery from POLDER. Here we investigate the influence of wind speed upon the discrimination process, showing that at very low wind speeds and very high wind speeds we are not able to discriminate the three cover types and that when wind speeds are moderate there is potentially an error associated with estimation of the areal extent of open water areas.
Environmental limiting factors (ELFs) are the thresholds that determine the maximum or minimum biological response for a given suite of environmental conditions. We asked the following questions: 1) Can we detect ELFs on percent tree cover across the eastern slopes of the Lake Tahoe Basin, NV? 2) How are the ELFs distributed spatially? 3) To what extent are unmeasured environmental factors limiting tree cover? ELFs are difficult to quantify as they require significant sample sizes. We addressed this by using geospatial data over a relatively large spatial extent, where the wall-to-wall sampling ensures the inclusion of rare data points which define the minimum or maximum response to environmental factors. We tested mean temperature, minimum temperature, potential evapotranspiration (PET) and PET minus precipitation (PET-P) as potential limiting factors on percent tree cover. We found that the study area showed system-wide limitations on tree cover, and each of the factors showed evidence of being limiting on tree cover. However, only 1.2% of the total area appeared to be limited by the four (4) environmental factors, suggesting other unmeasured factors are limiting much of the tree cover in the study area. Where sites were near their theoretical maximum, non-forest sites (tree cover < 25%) were primarily limited by cold mean temperatures, open-canopy forest sites (tree cover between 25% and 60%) were primarily limited by evaporative demand, and closed-canopy forests were not limited by any particular environmental factor. The detection of ELFs is necessary in order to fully understand the width of limitations that species experience within their geographic range.
Wolf and Anderegg, Hijmans, and Stephenson and Das suggest that our findings of changes in climatic water balance driving downhill shifts in plant species distributions are flawed. We demonstrate that the conclusions these authors make are subject to the selection of methods they apply and do not provide sufficient evidence to reject our original findings.
Sprague-Dawley rats have been used to study the pathogenesis and toxicokinetics of snakeweed (Gutierrezia microcephala and G sarothrae) toxicosis. Diets containing as little as 10% snakeweed (SW) will induce early embryonic toxicosis and abortion in Sprague-Dawley rats. The sc administration of safflower oil to inseminated female rats will provide protection/tolerance against SW embryotoxins. Two studies evaluated this embryotoxin protection. In the first study, an increase in daily consumption of SW resulted in increased embryo-fetal survival in the SW-containing diet+saline group from 0% in previous studies to 35%. In the second study, once again an increase in diet consumption was associated with 40% of the females in the SW-containing diet+saline group carrying litters to term.
