Oxygen isotope ratios of pedogenic carbonates were analyzed along a climatic gradient in the Palo... more Oxygen isotope ratios of pedogenic carbonates were analyzed along a climatic gradient in the Palouse region of eastern Washington State to evaluate changes in their isotopic composition with changing climate. A modern analog approach was used to assess the relationship between the istotope ratios in the pedogenic carbonates with those in soil water (measured in June when we anticipated carbonate formation might occur because of low soil water content), and meteoric water from two National Atmospheric Deposition Program (NADP) sites adjacent to our sequence. Mean annual meteoric water d 18 O values (wrt VSMOW) from the two NADP sites varied slightly with elevation, -13.9‰ at the Starkey site (elevation 1253 m) and -13.0‰ at the Palouse site, (elevation 766 m) but showed distinct seasonal trends with weighted means ranging from -11.9‰ during autumn to -15.0‰ during the winter. Carbonate d 18 O (wrt VPDB) varied significantly with MAP, ranging from -14.1‰ at the most arid site to -11.4‰ at the wettest site but displayed a trend opposite to that of soil water d 18 O (-4 to -12‰ VSMOW for the 70 cm depth). Neither measured soil water d 18 O values nor mean meteoric water d 18 O values generated realistic temperatures of formation for the observed trend in carbonate d 18 O values. When mean annual temperatures across the gradient were used for temperature of formation, calculated soil water d 18 O in equilibrium with carbonate d 18 O was similar to winter precipitation d 18 O at the most arid sites but became increasingly similar to mean annual meteoric d 18 O as MAP increased. We suggest that the unexpected trend in carbonate d 18 O is largely due to the diminishing influence of winter precipitation/snowmelt on soil moisture as MAP increases across the climatic gradient and that seasonal effects of meteoric water may need to be considered in pedogenic mineral isotopic equilibrium in temperate regions.
Plantations of radiata pine (Pinus radiata) cover more than 4,000,000 ha worldwide [P.B. Lavery, ... more Plantations of radiata pine (Pinus radiata) cover more than 4,000,000 ha worldwide [P.B. Lavery, D.J. Mead, Pinus radiata: a narrow endemic from North America takes on the world, in: D.M. Richardson (Ed.), Ecology and Biogeography of Pinus, Cambridge University Press, Cambridge, 1998, pp. 432-449]. In many areas, including the Ecuadorian Andes, these plantations have been established on former grasslands. Although this land use has grown over the past four decades in Ecuador, little is known about the effect of the change in vegetation cover on nutrient cycling in the high-altitude grassland systems where the plantations are frequently established. We examined changes in soil nitrogen, phosphorus, and acidity with stand age, using a chronosequence of stands ranging from 0 to 25 years of age. The effects of planting the grasslands with pine were most notable near the soil surface (0-10 cm), although in some cases changes deeper in the A horizon were also large. Total nitrogen concentrations became increasingly depleted along the chronosequence at intermediate depth (P ¼ 0:04), while N was gained in the litter (P ¼ 0:02) and upper-A horizon (P ¼ 0:001) until the plantations reached 20 years, at which point it again declined. In the top 10 cm, concentrations of NO 3 À increased dramatically under pine (P < 0:001), while NH 4 þ was lower than in grasslands (P ¼ 0:04). Unlike nitrogen, neither total nor available phosphorus was significantly altered by the change in vegetation. Soil pH was higher in the grassland soils (5.5) than under pine stands of any age (P < 0:01), all of which had a mean pH of 5.2. Acidification under pine occurred only in the top 10 cm, with no differences in pH at other depths, indicating that it is being driven by soil processes that predominate in the near-surface environment. These results demonstrate that the change of vegetation can affect soil properties on a decadal time scale, with implications for long-term site productivity.
Topographic orientation influences patterns of snow accumulation and generates distinct edaphic p... more Topographic orientation influences patterns of snow accumulation and generates distinct edaphic properties and biogeochemical processes on the leeward and windward slopes of alpine ridges. Removal of snow from windward slopes exposes these landscapes to colder wintertime soil temperatures and higher frequency of freeze-thaw events. In contrast, increased snow accumulation on leeward slopes dampens subnivean temperature fluctuations and maintains adequate conditions to sustain wintertime soil microbial activity. Our work on alpine ridges at the Fraser Experimental Forest in central Colorado Rockies indicates that nitrogen dynamics and the soil chemical environment differ between windswept and leeward alpine slopes and across the alpine-subalpine ecotone. Soil nitrate occurs at near-detection levels in subalpine forest and on leeward alpine slopes. In contrast, windward alpine soils contain significant nitrate in both the 0-5 cm (3.4 mg g-1) and 5-15 cm (4.5 mg g-1) depths. Alpine soils incubated under constant moisture and temperature showed a similar, but less dramatic topographic effect on nitrification. This suggests that sufficient substrate exists to support nitrifying bacteria on both aspects and that environmental conditions may be more critical in regulating microbial processes in the alpine. Similar to the pattern observed for nitrate, soil pH is significantly higher on windward alpine sites. We believe this demonstrates a shift in the relative importance of physical to chemical weathering across the alpine ridge. The distinct biogeochemical conditions within alpine landscapes and across the treeline ecotone may help explain patterns of N export and improve predictions regarding the impact of climate change on watershed processes and water quality.
Ultraviolet VDR Vitamin D Receptor Wits University of the Witwatersrand 25(OH)D Serum 25-hydroxyv... more Ultraviolet VDR Vitamin D Receptor Wits University of the Witwatersrand 25(OH)D Serum 25-hydroxyvitamin D xi
Artificial Intelligence (AI) must be directed at humane ends. The development of AI has produced ... more Artificial Intelligence (AI) must be directed at humane ends. The development of AI has produced great uncertainties of ensuring AI alignment with human values (AI value alignment) through AI operations from design to use. For the purposes of addressing this problem, we adopt the phenomenological theories of material values and technological mediation to be that beginning step. In this paper, we first discuss the AI value alignment from the relevant AI studies. Second, we briefly present what are material values and technological mediation and reflect on the AI value alignment through the lenses of these theories. We conclude that a set of finite human values can be defined and adapted to the stable life tasks that AI systems will be called upon to accomplish. The AI value alignment can also be fostered between designers and users through technological mediation. Upon that foundation, we propose a set of common principles to understand the AI value alignment through phenomenological...
The need for a systematic approach to work with artificial intelligence (AI) is current and rapid... more The need for a systematic approach to work with artificial intelligence (AI) is current and rapidly growing. It is important that Information Systems researchers get ahead of public sentiment and be able to provide proactive commentary about the current state-of-the-art, as well as solutions for future systems. One critical question is how can we ensure value alignment between AI and human values through AI operations from design to use? For the purposes of this discussion, we adopt the phenomenological theories of material values and technological mediation to be that beginning step. In this paper, we firstly analyze the AI phenomenon from selected resources from the top IS research outlets (basket of 8 journals and 5 AI journals in IS). Secondly, we briefly present what are material values and technological mediation and reflect on the AI value alignment principle through the lenses of these theories. Supported by these new understandings and reflections, we propose to build a common principle of human values to understand the AI value alignment principle through phenomenological theories. The paper contributes unique aspect of material values that are not addressed in the current AI research.
The Shortgrass Steppe Long Term Ecological Research (SGS-LTER) project is entering its final year... more The Shortgrass Steppe Long Term Ecological Research (SGS-LTER) project is entering its final year of a more than 30-year history (1982-2014) of research and engagement within the LTER network. During this transition we are simultaneously bringing closure to several of our experiments and expanding our infrastructure in the field to position our community of scientists for future work. New initiatives and infrastructure include the following: 1) a common garden experiment to assess the genetic plasticity and response of the dominant grass species, Bouteloua gracilis, to climate change. Field collections were made for our common garden experiment in 2011 and representative plants will be installed at the new SGS Research and Interpretation Center garden this fall; 2) A new grazing experiment designed to investigate the response of shortgrass steppe plant communities (e.g., species composition and abundance) to changing climate and grazer populations; and 3) New rainout shelters to und...
Published by Copernicus Publications on behalf of the European Geosciences Union. 4816 D. D. Rich... more Published by Copernicus Publications on behalf of the European Geosciences Union. 4816 D. D. Richter et al.: Strengthening the biogeosciences in environmental research networks
By signing and submitting this proposal, the Authorized Organizational Representative or Individu... more By signing and submitting this proposal, the Authorized Organizational Representative or Individual Applicant is: (1) certifying that statements made herein are true and complete to the best of his/her knowledge; and (2) agreeing to accept the obligation to comply with NSF award terms and conditions if an award is made as a result of this application. Further, the applicant is hereby providing certifications regarding debarment and suspension, drug-free workplace, and lobbying activities (see below), nondiscrimination, and flood hazard insurance (when applicable) as set forth in the NSF Proposal & Award Policies & Procedures Guide, Part I: the Grant Proposal Guide (GPG) (NSF 08-1). Willful provision of false information in this application and its supporting documents or in reports required under an ensuing award is a criminal offense (U. S. Code, Title 18, Section 1001).
2003 9 served for agrarian settlement. Lewis and Clark objectively observed both gardens and dese... more 2003 9 served for agrarian settlement. Lewis and Clark objectively observed both gardens and deserts during the expedition and reported those observations in their journals. Lewis's reaction to the prairies of the Great Plains shows the extent to which he was a scientific observer of the landscape. He had heard that the prairies were like deserts ("barren, steril and sandy"), but objective observation showed them to be "fertile in the extreem.
The State of Florida (USA) is especially threatened by sea level rise due to extensive low elevat... more The State of Florida (USA) is especially threatened by sea level rise due to extensive low elevation coastal habitats (approximately 8,000 km 2 < 1 m above sea level) where the majority of the human population resides. We used the Sea Level Affecting Marshes Model (SLAMM) simulation to improve understanding of the magnitude and location of these changes for 58,000 ha of the Waccasassa Bay region of Florida's central Gulf of Mexico coast. To assess how well SLAMM portrays changes in coastal wetland systems resulting from sea level rise, we conducted a hindcast in which we compared model results to 30 years of field plot data. Overall, the model showed the same pattern of coastal forest loss as observed. Prospective runs of SLAMM using 0.64 m, 1 m and 2 m sea level rise scenarios predict substantial changes over this century in the area covered by coastal wetland systems including net losses of coastal forests (69%, 83%, and 99%, respectively) and inland forests (33%, 50%, and 88%), but net gains of tidal flats (17%, 142%, and 3,837%). One implication of these findings at the site level is that undeveloped, unprotected lands inland from the coastal forest should be protected to accommodate upslope migration of this natural community in response to rising seas. At a broader scale, our results suggest that coastal wetland systems will be unevenly affected across the Gulf of Mexico as sea level rises. Species vulnerable to these anticipated changes will experience a net loss or even elimination.
Isotopic signatures of soil components are commonly used to infer past ecologic and climatic shif... more Isotopic signatures of soil components are commonly used to infer past ecologic and climatic shifts in the soil record. The theory behind the fractionation of isotopes that occurs during ecosystem processes is well understood; however, few isotopic studies have explored ecosystem relationships in modern soils. We discuss relationships of stable carbon isotopic signatures in plant tissue, soil organic carbon (SOC), laboratory-respired CO 2 , and modern carbonates at 10 sites (seven containing pedogenic carbonates) along a C 3 -dominated climatic gradient (mean annual precipitation (MAP) ranging from 200 to 1000 mm) in the Palouse region of eastern Washington state. A horizon soil organic carbon (SOC) d 13 C values varied from À 24.3x to À 25.9x PDB. Values in the arid portion of the gradient (200 to approximately 500 mm MAP) generally decreased and linear regression of SOM 13 C vs. MAP was significant (r 2 = 0.71, p = 0.02). Trends in plant-13 C of two grass species (Agropyron spicatum and Festuca idahoensis) found throughout this portion of the gradient were similar to that of SOC. Mean pedogenic carbonate d 13 C values varied from À 4.1xto À 10.8x PDB. Linear regression was significant for carbonate 13 C vs. MAP (r 2 = 0.79, p = 0.007), estimated above-ground productivity (r 2 = 0.88, p = 0.002) and soil carbon content (r 2 = 0.83, p = 0.004). Carbonate d 13 C values at the most arid site exhibited higher variability than other sites (presumably due to greater spatial variation in plant respiration vs. atmospheric diffusion). Our data suggest that carbon isotopic relationships among ecosystem components may prove useful in determining ecosystem level properties in modern systems, and potentially in ancient systems as well.
Besides well‐known effects of climate and parent material on silicate weathering the role of land... more Besides well‐known effects of climate and parent material on silicate weathering the role of land use change as a driver in the global silicon cycle is not well known. Changes in vegetation cover have altered reservoirs of silicon and carbon in plants and soils. This has potential consequences for plant‐Si availability, agricultural yields, and coastal eutrophication, as Si is a beneficial element for many crop plants and an essential nutrient for diatom growth. We here examined the role of sustained and intensive land use and human disturbance on silicon (Si) pool distribution in soils with similar climatological and bulk mineralogical characteristics. We show that land use impacts both biogenic and nonbiogenic Si pools. While biogenic Si strongly decreases along the land use change gradient (from forest to croplands), pedogenic silica fractions (e.g. pedogenic clays) increase in topsoils with a long duration of cultivation and soil disturbance. Our results suggest that nonbiogenic...
Wildfire is a natural disturbance, though elemental losses and changes that occur during combusti... more Wildfire is a natural disturbance, though elemental losses and changes that occur during combustion and post-fire erosion can have long-term impacts on soil properties, ecosystem productivity, and watershed condition. Here we evaluate the potential of forest residue-based materials to rehabilitate burned soils. We compare soil nutrient and water availability, and plant recovery after application of 37 t ha−1of wood mulch, 20 t ha−1of biochar, and the combination of the two amendments with untreated, burned soils. We also conducted a greenhouse trial to examine how biochar influenced soil nutrient and water content under two wetting regimes. The effects of wood mulch on plant-available soil N and water content were significant and seasonally consistent during the three-year field study. Biochar applied alone had few effects under field conditions, but significantly increased soil pH, Ca, P, and water in the greenhouse. The mulched biochar treatment had the greatest effects on soil N ...
Uploads
Papers by Eugene Kelly