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Michael H. Young

Bio: Michael H. Young is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Soil water & Water content. The author has an hindex of 30, co-authored 143 publications receiving 3073 citations. Previous affiliations of Michael H. Young include Desert Research Institute & University of Arizona.


Papers
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Journal ArticleDOI
TL;DR: Key challenges in modeling soil processes are identified, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes.
Abstract: The remarkable complexity of soil and its importance to a wide range of ecosystem services presents major challenges to the modeling of soil processes. Although major progress in soil models has occurred in the last decades, models of soil processes remain disjointed between disciplines or ecosystem services, with considerable uncertainty remaining in the quality of predictions and several challenges that remain yet to be addressed. First, there is a need to improve exchange of knowledge and experience among the different disciplines in soil science and to reach out to other Earth science communities. Second, the community needs to develop a new generation of soil models based on a systemic approach comprising relevant physical, chemical, and biological processes to address critical knowledge gaps in our understanding of soil processes and their interactions. Overcoming these challenges will facilitate exchanges between soil modeling and climate, plant, and social science modeling communities. It will allow us to contribute to preserve and improve our assessment of ecosystem services and advance our understanding of climate-change feedback mechanisms, among others, thereby facilitating and strengthening communication among scientific disciplines and society. We review the role of modeling soil processes in quantifying key soil processes that shape ecosystem services, with a focus on provisioning and regulating services. We then identify key challenges in modeling soil processes, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes. We discuss how the soil modeling community could best interface with modern modeling activities in other disciplines, such as climate, ecology, and plant research, and how to weave novel observation and measurement techniques into soil models. We propose the establishment of an international soil modeling consortium to coherently advance soil modeling activities and foster communication with other Earth science disciplines. Such a consortium should promote soil modeling platforms and data repository for model development, calibration and intercomparison essential for addressing contemporary challenges.

542 citations

Journal ArticleDOI
TL;DR: In this article, the authors quantified and explained the direct physical effects of slope angle on infiltration and runoff generation by extending the Green-Ampt equation onto sloping surfaces and found that infiltration increases with increasing slope angle.
Abstract: [1] This work quantifies and explains the direct physical effects of slope angle on infiltration and runoff generation by extending the Green-Ampt equation onto sloping surfaces. A new extended solution using identical precipitation hydrographs was compared to the original formulation and then used to calculate the infiltration and runoff generation for different slope angles but for identical horizontal projection lengths. Homogeneous and isotropic soil is assumed, and two different boundary conditions for vertical rainfall are studied: ponded infiltration and infiltration under steady rainfall. Infiltration under unsteady rainfall was found to be similar to cases with steady rainfall. Both theoretical and numerical results show that infiltration increases with increasing slope angle. For cases with ponded infiltration the slope effect was generally not significant for mild to moderate slopes, but the slope effect became more important for low-intensity and short-duration rainfall events, especially as it delayed the time for ponding. It was also found that the cumulative vertical infiltration depth (Ihp) at ponding (or the initial loss) increases with increasing slope angle. The model was compared to Richards' equation on horizontal and sloping surfaces and found to perform well. The model's applicability for nonuniform slopes was discussed, and it was found that the model is generally applicable for isotropic and mildly anisotropic soils except for some small-scale topographic elements. Finally, the occurrence of nonvertical rainfall could increase runoff with increasing slope angle when rainfall deflects a large angle to upslope.

193 citations

Journal ArticleDOI
TL;DR: The authors here introduce and evaluate the consequences at local and global scale of modifying hydraulic properties of soils in response to biological activity—a process significantly changing soil structure.
Abstract: Most soil hydraulic information used in Earth System Models (ESMs) is derived from pedo-transfer functions that use easy-to-measure soil attributes to estimate hydraulic parameters. This parameterization relies heavily on soil texture, but overlooks the critical role of soil structure originated by soil biophysical activity. Soil structure omission is pervasive also in sampling and measurement methods used to train pedotransfer functions. Here we show how systematic inclusion of salient soil structural features of biophysical origin affect local and global hydrologic and climatic responses. Locally, including soil structure in models significantly alters infiltration-runoff partitioning and recharge in wet and vegetated regions. Globally, the coarse spatial resolution of ESMs and their inability to simulate intense and short rainfall events mask effects of soil structure on surface fluxes and climate. Results suggest that although soil structure affects local hydrologic response, its implications on global-scale climate remains elusive in current ESMs.

118 citations

Journal ArticleDOI
TL;DR: In this article, the authors evaluate how pedological development in near-surface soil horizons in an arid alluvial fan complex affects the soil hydraulic characteristics, and compare the use of Wooding9s equation and inverse modeling for evaluating hydraulic conductivity in highly layered, near surface soils.
Abstract: Desert pavements are prominent features in arid environments and consist of a surface layer of closely packed gravel that overlies a thin, gravel-poor, vesicular A (Av) soil horizon. Well-developed Av horizons form distinct and highly structured columnar peds. These structures, along with their silt- and clay-rich texture, are hypothesized as controlling infiltration and hence the overall hydrologic conditions in the soil profile. The objectives of this study were to (i) evaluate how pedological development in near-surface soil horizons in an arid alluvial fan complex affects the soil hydraulic characteristics, and (ii) to compare the use of Wooding9s equation and inverse modeling for evaluating hydraulic conductivity in highly layered, near-surface soils. These objectives were approached through field tension infiltrometer studies, soil sampling, and laboratory analyses of soil texture, water content, and soluble salt concentrations. Soils at five sites were studied at the Mojave National Preserve, California, representing a soil chronosequence (50–100000 yr) with varying degrees of desert pavement development. Results indicated 100-fold and threefold declines, respectively, in saturated hydraulic conductivity ( K s ) with both analytical methods, and α w using Wooding9s method, as the soils aged. No clear trends in K s or α w were detected in the underlying horizon, indicating that the controlling feature at these sites, in terms of water entry, was the K s of the surface (Av) horizon. Soluble salt concentrations within the profile indicated reduced infiltration with increased pavement development. Results showed that surface age can be used as an excellent predictor of saturated hydraulic conductivity ( r 2 = 0.9254). Further, results suggest that Av horizon development represents a key process controlling water cycling, potentially influencing ecosystem function in arid lands.

108 citations


Cited by
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Journal Article
TL;DR: This book by a teacher of statistics (as well as a consultant for "experimenters") is a comprehensive study of the philosophical background for the statistical design of experiment.
Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

13,333 citations

Reference EntryDOI
31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

3,792 citations

Journal ArticleDOI
TL;DR: The reliability of recharge estimates using different tech- niques is variable as mentioned in this paper, and uncertainties in each approach to estimating recharge underscore the need for application of multiple techniques to increase the expected recharge rates at a site.
Abstract: DOI 10.1007/s10040-0010176-2 Abstract Various techniques are available to quantify recharge; however, choosing appropriate techniques is often difficult. Important considerations in choosing a technique include space/time scales, range, and reliabili- ty of recharge estimates based on different techniques; other factors may limit the application of particular tech- niques. The goal of the recharge study is important be- cause it may dictate the required space/time scales of the recharge estimates. Typical study goals include water-re- source evaluation, which requires information on re- charge over large spatial scales and on decadal time scales; and evaluation of aquifer vulnerability to contam- ination, which requires detailed information on spatial variability and preferential flow. The range of recharge rates that can be estimated using different approaches should be matched to expected recharge rates at a site. The reliability of recharge estimates using different tech- niques is variable. Techniques based on surface-water and unsaturated-zone data provide estimates of potential recharge, whereas those based on groundwater data gen- erally provide estimates of actual recharge. Uncertainties in each approach to estimating recharge underscore the need for application of multiple techniques to increase

1,562 citations

Journal ArticleDOI
01 Mar 1994-Nature
TL;DR: It is clear that the above can lead to confusion when scientists of different countries are trying to communicate with each other, so an internationally recognized system of naming organisms is created.
Abstract: It is clear that the above can lead to confusion when scientists of different countries are trying to communicate with each other. Another example is the burrowing rodent called a gopher found throughout the western United States. In the southeastern United States the term gopher refers to a burrowing turtle very similar to the desert tortoise found in the American southwest. One final example; two North American mammals known as the elk and the caribou are known in Europe as the reindeer and the elk. We never sing “Rudolph the Red-nosed elk”! Confused? This was the reason for creating an internationally recognized system of naming organisms. To avoid confusion, living organisms are assigned a scientific name based on Latin or Latinized words. The English sparrow is Passer domesticus or Passer domesticus (italics or underlining these two names is the official written representation of a scientific name). Using a uniform naming system allows scientists from all over the world to recognize exactly which life form a scientist is referring to. The naming process is called the binomial system of nomenclature. Passer is comparable to a surname and is called the genus, while domesticus is the specific or species name (like your given name) of the English sparrow. Now scientists can give all sparrow-like birds the genus Passer but the species name will vary. All similar genera (plural for genus) can be grouped into another, “higher” category (see below). Study the following for a more through understanding of taxonomy. Taxonomy Analogy Kingdom: Animalia Country

1,305 citations