Showing papers by "University of Oklahoma published in 2003"

The International HapMap Project

Abstract: The goal of the International HapMap Project is to determine the common patterns of DNA sequence variation in the human genome and to make this information freely available in the public domain. An international consortium is developing a map of these patterns across the genome by determining the genotypes of one million or more sequence variants, their frequencies and the degree of association between them, in DNA samples from populations with ancestry from parts of Africa, Asia and Europe. The HapMap will allow the discovery of sequence variants that affect common disease, will facilitate development of diagnostic tools, and will enhance our ability to choose targets for therapeutic intervention.

The identity crisis within the is discipline: defining and communicating the discipline's core properties

Abstract: We are concerned that the IS research community is making the discipline's central identity ambiguous by, all too frequently, under-investigating phenomena intimately associated with IT-based systems and over-investigating phenomena distantly associated with IT-based systems. In this commentary, we begin by discussing why establishing an identity for the IS field is important. We then describe what such an identity may look like by proposing a core set of properties, i.e., concepts and phenomena, that define the IS field. Next, we discuss research by IS scholars that either fails to address this core set of properties (labeled as error of exclusion) or that addresses concepts/phenomena falling outside this core set (labeled as error of inclusion). We conclude by offering suggestions for redirecting IS scholarship toward the concepts and phenomena that we argue define the core of the IS discipline.

Narrow (n,m)-distribution of single-walled carbon nanotubes grown using a solid supported catalyst.

Abstract: Unusually structure-selective growth of single-walled carbon nanotubes (SWNTs) has been attained using a CVD method with a solid supported catalyst. In this method, CO feedstock disproportionates on silica-supported catalytic nanoclusters of Co that are formed in situ from mixed salts of Co and Mo. The nanotube products are analyzed by spectrofluorimetry to reveal distributions resolved at the level of individual (n,m) structures. Two structures, (6,5) and (7,5), together dominate the semiconducting nanotube distribution and comprise more than one-half of that population. The average diameter of produced SWNTs is only 0.81 nm, and a strong propensity is found favoring chiral angles near the armchair limit.

Nitrogen and Climate Change

Abstract: Models project that land ecosystems may be able take up a considerable proportion of the carbon dioxide released by human activities, thereby counteracting the anthropogenic emissions. In their Perspective, Hungate et al . argue that these carbon uptake estimates are too high because the models do not take other nutrients such as nitrogen into account appropriately. The authors estimate that there will not be enough nitrogen available to sustain the high carbon uptake scenarios. Nutrients other than nitrogen may also affect carbon uptake in ways not captured by most models.

Home country environments, corporate diversification strategies, and firm performance

Abstract: This study reexamines the relationships between corporate diversification strategies and firm performance and suggests that these relationships are related to home country environments. We examined...

Where Have We Been, Where Are We Going? Taking Stock in Creativity Research

Abstract: The dedicated work of numerous scholars has, over the last 10 years, led to some radical advances in our understanding of the nature and implications of creativity. This work has been summarized in 2 recent handbooks-Mark Runco's Creativity Research Handbook and Robert Sternberg's Handbook of Creativity. In this article I use these handbooks as a starting point to take stock in both what has been accomplished and what still needs to be done in our attempts to understand creativity. I begin by noting that both handbooks clearly describe the major approaches being used in studies of creativity and the findings resulting from each approach. A careful review of the chapters presented in these handbooks, however, brings to the fore a number of issues. For example, we need critical comparative tests contrasting the merits of different methods and theories, elaboration and extension of our traditional samples and our traditional measures, and more attempts to develop integrative models. However, some topics, suc...

Dispersion of Single-Walled Carbon Nanotubes in Aqueous Solutions of the Anionic Surfactant NaDDBS

Abstract: The insolubility of single-walled carbon nanotubes (SWNT) in either water or organic solvents has been a limitation for the practical application of this unique material. Recent studies have demonstrated that the suspendability of SWNT can be greatly enhanced by employing appropriate surfactants. Although the efficiency of anionic, cationic, and nonionic surfactants has been demonstrated to different extents, the exact mechanism by which carbon nanotubes and the different surfactants interact is still uncertain. To deepen the understanding of this interfacial phenomenon, we have investigated the effects of chemical modifications of the surface on the extent of nanotube-surfactant interaction. Such changes in the surface chemistry of the SWNT can be achieved by simply varying the pretreatment method, which can be acidic or basic. We have found that intrinsic surface properties such as the PZC (point of zero charge) are greatly affected by the purification method. That is, the electrical charge of the SWNT surface varies with the pH of the surrounding media. However, it has been found that during the adsorption of the anionic surfactant sodium dodecylbenzenesulfonate (NaDDBS) on SWNT Coulombic forces do not play a central role, but are overcome by the hydrophobic interactions between the surfactant tail and the nanotube walls. Only at pH values far from the PZC do the Coulombic forces become important. The hydrophobic forces between the surfactant tail and the nanotube determine the structure of the surfactant-stabilized nanotubes. In such a structure, each nanotube is covered by a monolayer of surfactant molecules in which the heads form a compact outer surface while the tails remain in contact with the nanotube walls. It is important to note that although the final configuration can be described as a cylindrical micelle with a nanotube in the center, the mechanism of formation of this structure does not proceed by incorporation of a nanotube into a micelle, but rather by a two-step adsorption that ends up in the formation of a surfactant monolayer.

The Extremely Metal-poor, Neutron Capture-rich Star CS 22892-052: A Comprehensive Abundance Analysis

Abstract: High-resolution spectra obtained with three ground-based facilities and the Hubble Space Telescope (HST) have been combined to produce a new abundance analysis of CS 22892-052, an extremely metal-poor giant with large relative enhancements of neutron capture elements. A revised model stellar atmosphere has been derived with the aid of a large number of Fe peak transitions, including both neutral and ionized species of six elements. Several elements, including Mo, Lu, Au, Pt, and Pb, have been detected for the first time in CS 22892-052, and significant upper limits have been placed on the abundances of Ga, Ge, Cd, Sn, and U in this star. In total, abundance measurements or upper limits have been determined for 57 elements, far more than previously possible. New Be and Li detections in CS 22892-052 indicate that the abundances of both these elements are significantly depleted compared to unevolved main-sequence turnoff stars of similar metallicity. Abundance comparisons show an excellent agreement between the heaviest n-capture elements (Z ≥ 56) and scaled solar system r-process abundances, confirming earlier results for CS 22892-052 and other metal-poor stars. New theoretical r-process calculations also show good agreement with CS 22892-052 abundances and the solar r-process abundance components. The abundances of lighter elements (40 ≤ Z ≤ 50), however, deviate from the same scaled abundance curves that match the heavier elements, suggesting different synthesis conditions or sites for the low-mass and high-mass ends of the abundance distribution. The detection of Th and the upper limit on the U abundance together imply a lower limit of 10.4 Gyr on the age of CS 22892-052, quite consistent with the Th/Eu age estimate of 12.8± 3 Gyr. An average of several chronometric ratios yields an age 14.2± 3 Gyr.

Regional Angiogenesis With Vascular Endothelial Growth Factor in Peripheral Arterial Disease A Phase II Randomized, Double-Blind, Controlled Study of Adenoviral Delivery of Vascular Endothelial Growth Factor 121 in Patients With Disabling Intermittent Claudication

Abstract: Background— “Therapeutic angiogenesis” seeks to improve perfusion by the growth of new blood vessels. The Regional Angiogenesis with Vascular Endothelial growth factor (RAVE) trial is the first major randomized study of adenoviral vascular endothelial growth factor (VEGF) gene transfer for the treatment of peripheral artery disease (PAD). Methods and Results— This phase 2, double-blind, placebo-controlled study was designed to test the efficacy and safety of intramuscular delivery of AdVEGF121, a replication-deficient adenovirus encoding the 121-amino-acid isoform of vascular endothelial growth factor, to the lower extremities of subjects with unilateral PAD. In all, 105 subjects with unilateral exercise-limiting intermittent claudication during 2 qualifying treadmill tests, with peak walking time (PWT) between 1 to 10 minutes, were stratified on the basis of diabetic status and randomized to low-dose (4×109 PU) AdVEGF121, high-dose (4×1010 PU) AdVEGF121, or placebo, administered as 20 intramuscular injec...

In pursuit of moderation: nine common errors and teir solutions

Abstract: One result of the increasing sophistication and complexity of MIS theory and research is the number of studies hypothesizing and testing for moderation effects. A review of the MIS and broader management literatures suggests researchers investigating moderated relationships often commit one or more errors falling into three broad categories: inappropriate use or interpretation of statistics, misalignment of research design with phenomena of interest, and measurement or scaling issues. Examples of nine common errors are presented. Commission of these errors is expected to yield literatures characterized by mixed results at best, and thoroughly erroneous results at worse. Procedures representing examples of best practice and reporting guidelines are provided to help MIS investigators avoid or minimize these errors.

The contingent effects of management support and task interdependence on successful information systems implementation

Abstract: Management support is considered to be a critical factor in the successful implementation of information systems innovations. The literature suggests a complex relationship between management support and implementation success. However, the empirical literature typically hypothesizes and tests a simple main-effects model. Drawing upon the role of the institutional context and metastructuration actions, we propose a contingent model in which task interdependence moderates the effect of management support on implementation success. A meta-analysis of the empirical literature provides strong support for the model and begins to explain the wide variance in empirical findings. Implications for theory and practice are discussed.

Scaffolding Students' Problem-Solving Processes in an Ill-Structured Task Using Question Prompts and Peer Interactions

Abstract: This study examined the effects of question prompts and peer interactions in scaffolding undergraduate students’ problem-solving processes in an ill-structured task in problem representation, developing solutions, making justifications, and monitoring and evaluating. A quasi-experimental study, supplemented by multiple-case studies, was conducted to investigate both the outcomes and the processes of student problem-solving performance. The quantitative outcomes revealed that question prompts had significantly positive effects on student problem-solving performance but peer interactions did not show significant effects. The qualitative findings, however, did indicate some positive effects of peer interactions in facilitating cognitive thinking and metacognitive skills. The study suggests that the peer interaction process itself must be guided and monitored with various strategies, including question prompts, in order to maximize its benefits.

Institutional Ownership Differences and International Diversification: The Effects of Boards of Directors and Technological Opportunity

Abstract: We examined the roles of institutional investors, boards of directors, and technological opportunity in relation to international diversification. Our research contributes to both agency and foreign direct investment theories. In data on 197 large U.S. firms, we found significant relationships between institutional ownership and international diversification. International diversification was favored by (1) professional investment funds along with outside board members and (2) pension funds along with inside board members. Also, pension funds' long-term orientation facilitated internationalization in industries with high technological opportunities. The results suggest that different institutional owners have different stakes in firms' international strategies, and the effects of boards of directors and technological opportunity accentuate these differences.

Measuring Individual Differences in the Tendency to Forgive: Construct Validity and Links with Depression

Abstract: Four studies examine the construct validity of the Tendency to Forgive Scale (TTF), a brief measure of dispositional forgiveness. Study 1 showed that romantic partners' ratings of targets converged with targets' self-ratings, and Study 2 demonstrated that higher scores on the TTF were associated with lower offense accessibility. Study 3 examined the TTF's relation to self-reported depression symptoms, both independent of and interacting with attitudes toward forgiveness and dispositional vengeance. Lower TTF scores were associated with higher degrees of depression, especially for individuals with positive attitudes toward forgiveness or those low in dispositional vengeance, although neither of these latter variables displayed significant zero-order relations with depression. Finally, Study 4 examined relations between the TTF, dispositional empathy, another recent measure of dispositional forgiveness, and the dimensions of the Big Five, providing both convergent and discriminant validity evidence for the TTF.

The value relevance of announcements of transformational information technology investments

Abstract: In this paper, we examine the influence of IT strategic role to extend the findings of Im et al. (2001), Chatterjee et al. (2002) and Dos Santos et al. (1993). Specifically, we demonstrate that IT strategic role can explain how IT investments in each of the IT strategic roles might affect the firm's competitive position and ultimately firm value. We find positive, abnormal returns to announcements of IT investments by firms making transformative IT investments, and with membership in industries with transform IT strategic roles. The results of previous research are not found to be significant when IT strategic role is included as an explanatory variable. These results provide support for the value of capturing the IT strategic role of a firm's IT-related competitive maneuvering in studies striving to understand the conditions under which IT investments are likely to produce out-of-the-ordinary, positive returns.

The Social Construction of Meaning: An Alternative Perspective on Information Sharing

Abstract: Research on information sharing has viewed this activity as essential for informing groups on content relevant to a decision. We propose and examine an alternate function of information sharing, i.e., the social construction of meaning. To accomplish this goal, we turn to social construction, social presence, and task closure theories. Drawing from these theories, we hypothesize relationships among the meeting environment, breadth and depth of information shared during a meeting, and decision quality. We explore these relationships in terms of the effects of both the media environment in which the group is situated and the medium that group memberschoose to utilize for their communication.Our study of 32, 5- and 6-person groups supports our belief that interpretation underlies information sharing and is necessary for favorable decision outcomes. It also supports the proposed negative effect of low social presence media on interpretation in terms of depth of information sharing; a low social presence medium, however, promotes information sharing breadth. Finally, the findings indicate that when in multimedia environments and faced with a relatively complex task,choosing to utilize an electronic medium facilitates closure and, therefore, favorable outcomes.

Emotional intelligence, leadership effectiveness, and team outcomes

Abstract: Emotional intelligence reflects the ability to read and understand others in social contexts, to detect the nuances of emotional reactions, and to utilize such knowledge to influence others through emotional regulation and control. As such, it represents a critically important competency for effective leadership and team performance in organizations today. In this paper, we develop a conceptual model that brings together theory and research on emotional intelligence, leadership, and team process and outcomes. Additionally, we formulate testable propositions, propose directions for future research, and discuss implications for practice.

Are All Dads Equal? Biology versus Marriage as a Basis for Paternal Investment

Abstract: The stepfather relationship provides a source of potential conflict in remarriage families, because the mother and partner may have different interests in the well-being of children from a prior union. Using three different theoretical perspectives—biology, sociology, and selection—this paper examines the engagement, availability, participation, and warmth of residential fathers in married biological parent, unmarried biological parent, married stepparent, and cohabiting father families. The data come from 2,531 children and their parents who were interviewed during the 1997 wave of the Child Development Supplement to the Panel Study of Income Dynamics. Biology explains less of father involvement than anticipated once differences between fathers are controlled. Marriage continues to differentiate paternal investment levels, as do age of child and financial responsibility to nonresidential children.

Hermansky-Pudlak syndrome type 7 (HPS-7) results from mutant dysbindin, a member of the biogenesis of lysosome-related organelles complex 1 (BLOC-1).

Abstract: Hermansky-Pudlak syndrome (HPS; MIM 203300) is a genetically heterogeneous disorder characterized by oculocutaneous albinism, prolonged bleeding and pulmonary fibrosis due to abnormal vesicle trafficking to lysosomes and related organelles, such as melanosomes and platelet dense granules. In mice, at least 16 loci are associated with HPS, including sandy (sdy; ref. 7). Here we show that the sdy mutant mouse expresses no dysbindin protein owing to a deletion in the gene Dtnbp1 (encoding dysbindin) and that mutation of the human ortholog DTNBP1 causes a novel form of HPS called HPS-7. Dysbindin is a ubiquitously expressed protein that binds to alpha- and beta-dystrobrevins, components of the dystrophin-associated protein complex (DPC) in both muscle and nonmuscle cells. We also show that dysbindin is a component of the biogenesis of lysosome-related organelles complex 1 (BLOC-1; refs. 9-11), which regulates trafficking to lysosome-related organelles and includes the proteins pallidin, muted and cappuccino, which are associated with HPS in mice. These findings show that BLOC-1 is important in producing the HPS phenotype in humans, indicate that dysbindin has a role in the biogenesis of lysosome-related organelles and identify unexpected interactions between components of DPC and BLOC-1.

Effects of drought on fish across axes of space, time and ecological complexity

Abstract: 1. We evaluate the position of 50 previously published studies of fish and drought with respect to spatial scale of study (individual stream pools to subcontinents), length of the dry period (weeks to centuries), and level of system complexity (individual fish to ecosystems). Most papers address short (months to a year) droughts or dry periods, in local reaches of streams, and impacts on populations or local assemblages. In these 50 papers, the most frequently demonstrated effects of drought were population declines, loss of habitat, changes in the community, negative effects from changes in water quality, movement within catchments, and crowding of fish in reduced microhabitats. Thirteen other less frequent effects also were identified. 2. Gaps in knowledge exist on effects of long-term droughts (decades to centuries), influence of drought on fish effects in ecosystems, and at the spatial scale of river basins to subcontinents. However, some of these gaps have recently been addressed, particularly additive effects of repeated drying episodes and whole-lake or basin-wide effects of drought, and in using molecular techniques to seek signals of drought at wide geographic scales because of events in the deep past. Gaps in knowledge remain for effects of very short dry periods, on drought effects on higher levels of complexity, and on the manner in which droughts at the scale of decades affect fish. 3. Data from streams in Oklahoma and elsewhere in the south-western U.S.A. suggest that most droughts may leave little persistent signal in the existing fish fauna, i.e. that recovery from drought by fish populations or assemblages in the region can be rapid. However, species that are vulnerable to drought or water loss in streams may have disappeared from some basins in the region before the mid-1900s, and recent evidence also suggests that extreme droughts do sometimes alter fish assemblages. 4. Little is known about mechanisms by which droughts have direct or indirect effects on fish, the roles of droughts in the evolution of fish species, and the ways droughts alter effects of fish in ecosystems. Global climate changes may have serious consequences for future local or regional fish faunas, but ongoing studies of fish experiencing drought may aid in future conservation of what will become species at risk under climate-change scenarios.

Effect of flow perfusion on the osteogenic differentiation of bone marrow stromal cells cultured on starch-based three-dimensional scaffolds.

Abstract: This study aims to investigate the effect of culturing conditions (static and flow perfusion) on the proliferation and osteogenic differentiation of rat bone marrow stromal cells seeded on two novel scaffolds exhibiting distinct porous structures. Specifically, scaffolds based on SEVA-C (a blend of starch with ethylene vinyl alcohol) and SPCL (a blend of starch with polycaprolactone) were examined in static and flow perfusion culture. SEVA-C scaffolds were formed using an extrusion process, whereas SPCL scaffolds were obtained by a fiber bonding process. For this purpose, these scaffolds were seeded with marrow stromal cells harvested from femoras and tibias of Wistar rats and cultured in a flow perfusion bioreactor and in 6-well plates for 3, 7, and 15 days. The proliferation and alkaline phosphatase activity patterns were similar for both types of scaffolds and for both culture conditions. However, calcium content analysis revealed a significant enhancement of calcium deposition on both scaffold types cultured under flow perfusion. This observation was confirmed by Von Kossa-stained sections and tetracycline fluorescence. Histological analysis and confocal images of the cultured scaffolds showed a much better distribution of cells within the SPCL scaffolds than the SEVA-C scaffolds, which had limited pore interconnectivity, under flow perfusion conditions. In the scaffolds cultured under static conditions, only a surface layer of cells was observed. These results suggest that flow perfusion culture enhances the osteogenic differentiation of marrow stromal cells and improves their distribution in three-dimensional, starch-based scaffolds. They also indicate that scaffold architecture and especially pore interconnectivity affect the homogeneity of the formed tissue.

Manufacturer governance of foreign distributor relationships: do relational norms enhance competitiveness in the export market?

Abstract: Research on international marketing channels accentuates the importance of relational norms and trust-building activities between buyers and sellers. Indeed, cultural and country differences may limit the use and effectiveness of traditional tools (such as market incentives and authoritative control) that govern the relationship between an exporting manufacturer and its foreign distributor. Consequently, exporting manufacturers need to emphasize relationships with their foreign distributors. This research finds evidence that supports both direct and indirect effects between the manufacturer's use of governance via relational norms and its competitiveness in the export market. The indirect effect results from the mediating role of trust, a finding that makes a key contribution to the understanding of the role of relational governance in cross-border relationships.

Observation of a narrow resonance of mass 2.46 GeV/c2 decaying to D*s+π0 and confirmation of the D*sJ(2317) state

Abstract: Using 13.5 ${\mathrm{fb}}^{\ensuremath{-}1}$ of ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data collected with the CLEO II detector, we have observed a narrow resonance decaying to ${D}_{s}^{*+}{\ensuremath{\pi}}^{0}$ with a mass near $2.46\mathrm{GeV}{/c}^{2}.$ The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at $2.32\mathrm{GeV}{/c}^{2},$ the ${D}_{\mathrm{sJ}}^{*}{(2317)}^{+},$ that decays to ${D}_{s}^{+}{\ensuremath{\pi}}^{0}.$ Reconstructing the ${D}_{s}^{+}{\ensuremath{\pi}}^{0}$ and ${D}_{s}^{*+}{\ensuremath{\pi}}^{0}$ final states in CLEO data, we observe peaks in both of the corresponding reconstructed mass difference distributions, $\ensuremath{\Delta}{M(D}_{s}{\ensuremath{\pi}}^{0}{)=M(D}_{s}{\ensuremath{\pi}}^{0})\ensuremath{-}{M(D}_{s})$ and $\ensuremath{\Delta}{M(D}_{s}^{*}{\ensuremath{\pi}}^{0}{)=M(D}_{s}^{*}{\ensuremath{\pi}}^{0})\ensuremath{-}{M(D}_{s}^{*}),$ both of them at values near $350\mathrm{MeV}{/c}^{2}.$ We interpret these peaks as signatures of two distinct states, the ${D}_{\mathrm{sJ}}^{*}{(2317)}^{+}$ plus a new state, designated as the ${D}_{\mathrm{sJ}}{(2463)}^{+}.$ Because of the similar $\ensuremath{\Delta}M$ values, each of these states represents a source of background for the other if photons are lost, ignored or added. A quantitative accounting of these reflections confirms that both states exist. We have measured the mean mass differences $〈\ensuremath{\Delta}{M(D}_{s}{\ensuremath{\pi}}^{0})〉=350.0\ifmmode\pm\else\textpm\fi{}1.2(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.0(\mathrm{syst})\mathrm{MeV}{/c}^{2}$ for the ${D}_{\mathrm{sJ}}^{*}{(2317)}^{+}$ state, and $〈\ensuremath{\Delta}{M(D}_{s}^{*}{\ensuremath{\pi}}^{0})〉=351.2\ifmmode\pm\else\textpm\fi{}1.7(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.0(\mathrm{syst})\mathrm{MeV}{/c}^{2}$ for the new ${D}_{\mathrm{sJ}}{(2463)}^{+}$ state. We have also searched, but find no evidence, for decays of the two states via the channels ${D}_{s}^{*+}\ensuremath{\gamma},{D}_{s}^{+}\ensuremath{\gamma},$ and ${D}_{s}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}.$ The observations of the two states at 2.32 and $2.46\mathrm{GeV}{/c}^{2},$ in the ${D}_{s}^{+}{\ensuremath{\pi}}^{0}$ and ${D}_{s}^{*+}{\ensuremath{\pi}}^{0}$ decay channels, respectively, are consistent with their interpretations as $c\overline{s}$ mesons with an orbital angular momentum $L=1$ and spin and parity ${J}^{P}{=0}^{+}$ and ${1}^{+}.$

A meta‐analysis of the criterion‐related validity of assessment center dimensions

Abstract: We used meta-analytic procedures to investigate the criterion-related validity of assessment center dimension ratings. By focusing on dimension-level information, we were able to assess the extent to which specific constructs account for the criterion-related validity of assessment centers. From a total of 34 articles that reported dimension-level validities, we collapsed 168 assessment center dimension labels into an overriding set of 6 dimensions: (a) consideration/awareness of others, (b) communication, (c) drive, (d) influencing others, (e) organizing and planning, and (f) problem solving. Based on this set of 6 dimensions, we extracted 258 independent data points. Results showed a range of estimated true criterion-related validities from .25 to .39. A regression-based composite consisting of 4 out of the 6 dimensions accounted for the criterion-related validity of assessment center ratings and explained more variance in performance (20%) than Gaugler, Rosenthal, Thornton, and Bentson (1987) were able to explain using the overall assessment center rating (14%).

The Boundaries and Limitations of Agency Theory and Stewardship Theory in the Venture Capitalist/Entrepreneur Relationship*

Abstract: The dynamic ownership arrangements surrounding the venture capitalist–entrepreneur (VC–E) relationship inherent in new ventures make the examination of principals’ or venture capitalists’ (VCs) and...

Substrate regulation of soil respiration in a tallgrass prairie: Results of a clipping and shading experiment

Abstract: [1] Changes in soil respiration, one of the major fluxes of global carbon cycling, could significantly slow down or accelerate the increase in atmospheric CO2, with consequent feedbacks to climate change. It is critical to understand how substrate availability regulates soil respiration in projecting the response of carbon cycling to changed climate. We conducted a clipping and shading experiment for 1 year in a tallgrass prairie of the Great Plains, United States, to manipulate substrate supply to soil respiration. Our results showed that reduced substrate supply under clipping and/or shading significantly decreased soil respiration at all the timescales (diurnal, transient, and annual) irrespective of the minor concurrent changes in soil temperature and moisture. Annual mean soil respiration decreased significantly by 33, 23, and 43% for the clipping, shading, and clipping plus shading treatments, respectively. Temperature sensitivity of soil respiration decreased from 1.93 in the control plots to 1.88, 1.75, and 1.83 in the clipped, shaded, and clipped plus shaded plots, respectively. Rhizosphere respiration, respiration from decomposition of aboveground litter, and respiration from oxidation of soil organic matter and dead roots accounted for 30, 14, and 56% of annual mean soil respiration, respectively. Rhizosphere respiration was more sensitive to temperature than the other two components. Our results suggest a critical role of substrate supply in regulating soil respiration and its temperature sensitivity.