bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Crops with Tolerance to Salinity and Drought Stress
Authors: Verma D. P. S.
Published: November 2020

Availability of water is the most important factor for crop productivity. A vast area (more than 50 million hectares) of agricultural land throughout the world suffers from recurring droughts, resulting in poor crop productivity (Carter, 1975). An equally large area of land is affected by high salinity. Even though irrigated agriculture has increased significantly during the past twenty years, the high capital cost of this process and the resulting increase in salinity is making this approach difficult to adopt. Furthermore, excessive irrigation is lowering the water tables, reducing water availability even more. Drought and salinity are formidable obstacles to the development of new varieties that can give sufficient yield under water stress conditions (Boyer, 1982). Some plants have evolved adaptations to water deficit and high salinity. These adaptations encompass a wide variety of plant characteristics (McCue and Hanson, 1990), including developmental and structural traits, time of flowering, rooting patterns, leaf waxiness, and physiological mechanisms such as the ability to exclude salt or the compartmentalization of ions within the cell (Binzel et al., 1988). Obviously, these are Multigenic traits, and most of them are determined by gene products that have not yet been characterized. The Multigenic nature of the phenotypes has thwarted attempts to characterize these mechanisms at the genetic level and has hindered efforts to produce osmotolerant plants by traditional breeding and somaclonal variations (Vasil, 1990). Among the biochemical traits in the adaptation of plants to water stresses, synthesis and accumulation of compatible osmolytes and changes in patterns of carbon and nitrogen metabolism are most important. Plants accumulate energy-rich metabolites under water stress; the most prevalent of these are proline and betaines (Yancey et al., 1982). Concentration of K+ and organic solutes (primarily polyols) has been shown to increase in direct proportion to changes in osmotic stress in many bacteria, algae, and higher plants. With the recent advances in genetic transformation of crop plants, genes encoding entire biosynthetic pathways or that augment the rate-limiting step in an adaptive process can now be transferred to any crop plant.
Prospects for Engineering Enhanced Durable Disease Resistance in Crops
Authors: Lamb Chris
Published: November 2020

Plants have evolved a battery of defense mechanisms that in aggregate provide protection against a wide range of potential viral, bacterial, fungal, and other pathogens encountered throughout the plant life cycle. However, in the artificial setting of agriculture, disease, although the exception, can be costly and even devastating. Crop diseases have played significant roles in human history, exemplified by the widespread starvation and mass emigration triggered by the failure of European potato crops in the mid-nineteenth century as a result of late blight. Today, the use of pesticides, breeding for resistance, and integrated pest management provide important tools for reducing crop losses to pre-and postharvest diseases. However, agrichemicals are expensive, prohibitively so for many fanners in developing countries, and there are increasing concerns about environmental load from their intensive application. Likewise, major disease resistance (R) genes are in many cases not durable, resistance breaking down within one or two seasons as a result of selection pressure on the pathogen population, and most breeding efforts now rely on combinations of minor resistance genes, each giving partial protection. For a number of important diseases, such as take-all of wheat, there is no effective genetic resistance. Population growth, migration to cities, desertification, and climate change all now contribute to an urgent need to secure diversified food production against disease losses. In this chapter I discuss the prospects that genetic engineering of disease-resistance mechanisms can contribute to durable, broad protection and hence underpin enhanced crop productivity. Plants have a number of performed physical and chemical defensive mechanisms that help protect against the myriad potential pathogens to which plants arc exposed (Osbourn, 1996). However, superimposed upon this preexisting protective armory, plants respond to the perception of pathogen attack by activation of inducible defense mechanisms (Lamb et al., 1989; Staskawicz et al., 1995). Many of the most important crop diseases involve specialized interactions between pathogen and host. Interactions between specific plant cultivars and defined physiological races or strains of potential pathogens are described as compatible (host susceptible, pathogen virulent) or incompatible (host resistant, pathogen avirulent).
Significance of Dietary Protein Source in Human Nutrition: Animal and/or Plant Proteins?
Authors: Young Vernon R. , Scrimshaw Nevin S.
Published: November 2020

Within the framework of the interdisciplinary symposium on “Feeding a World Population of More Than Eight Billion People: A Challenge to Science,” the organizers asked us to discuss the role of animal protein foods as a necessary source of the nutritionally indispensable (essential) amino acids for meeting the needs of humans, including children. Specifically, we were directed to consider the recommendations made by a joint FAO/WHO Expert Consultation (FAO/WHO, 1991) concerning estimates of indispensable amino acid requirements in humans and the extent to which these estimates “were realistic in light of the observed adequacy of vegetarian diets; and how these requirements can be fulfilled.” Our focus, therefore, is on the requirements for amino acids, and so we attempt to meet our remit as follows: the most basic demand for the production of food proteins, assuming an adequately nourished, healthy population, is determined by the physiological requirements for a utilizable source of nitrogen and for the nine indispensable amino acids (with two conditionally indispensable amino acids, tyrosine and cystine) needed for support of maintenance, growth, and tissue repair. Adequate knowledge about the quantitative characteristics of these requirements is fundamental. Therefore, we begin by reviewing the status of current international estimates of amino acid requirements and argue that for the indispensable amino acids they are seriously inadequate for planning purposes, especially for adults, who will represent a sizable proportion of the world's future 8 billion people, and their food needs. The requirement for dietary protein consists of two components: (1) total nitrogen to serve the needs for synthesis of the nutritionally dispensable (nonessential) and conditionally indispensable amino acids, as well as for other physiologically important nitrogen-containing compounds, and (2) the nutritionally indispensable (essential) amino acids (IAA) that cannot be made by human tissues at rates commensurate with metabolic needs and so must be supplied from an exogenous source (diet, parenteral amino acid mixture). With respect to the human requirements for total nitrogen (protein), the current international recommendations are now broadly accepted (FAO/WHO/UNU, 1985).
Productivity, Poverty Alleviation, and Food Security
Authors: Winkelmann Donald L.
Published: November 2020

Most observers agree that, barring catastrophe, the global population will number more than 8 billion by 2025. There is, however, less agreement about the consequences for food security. Some, for example, Brown and Kane of the World Watch Institute (Brown and Kane, 1994), argue that there will be widespread shortages of foodstuffs, accompanied by higher global prices. Others, like Alexandratos of the Food and Agriculture Organization of the United Nations (FAO) (Alexandratos, 1995), claim that production will match rising demands and that prices will continue to decline in real terms. All agree, however, that the world’s poor, especially those in the poorest countries, will be without adequate food. This chapter links food security with poverty and argues that increased productivity in agriculture is the most effective way for the poor to achieve food security. What is food security? The International Food Policy Research Institute, IFPRI (IFPRI, 1995) defines food security as “economic and physical access at all times to the food required for a healthy and productive life.” Food security has two dimensions: the availability of food and access to food. Availability depends on production, and, while the debate about global availability continues, the view in this chapter, like that of the FAO, is that adequate food will be available globally at real prices roughly comparable to those prevailing in the 1990s. (See Dyson, 1996, p. 167, for perhaps the latest systematic study holding this view.) To achieve food adequacy, the major assumptions here are that research will continue to turn out the elements of improved technologies and that Eastern Europe, especially Russia and Ukraine, will move closer to its potential as a food supplier. Lack of access to food because of poverty, however, is a major challenge. Some people in the developed world and in higher-income developing countries do not have access to food, but policy changes could resolve that problem; certainly, such societies have the resources. This is not the case for the poor in the world’s poorest countries; for them, the combination of individual and societal poverty severely limits access to adequate foodstuffs.
Late Cretaceous through Early Eocene North American Vegetational History: 70-50 Ma
Authors: Graham Alan
Published: November 2020

At the end of the Cretaceous the Appalachian Mountains had undergone 180 m.y. of erosion since their principal uplift in the Middle Pennsylvanian through the Late Permian (300-250 Ma), but they were higher and more rugged than at present and provided a somewhat more diverse vertically zoned array of habitats. In contrast, the Rocky Mountains were only ~1 km above sea level at 65 Ma; the Coast Ranges, Sierra Nevada, and Cascade Mountains would not attain substantial heights until late in the Tertiary. Computer models in the NM mode, which simulate conditions in western North America in the Late Cretaceous, show a nearly continuous westerly jet stream with relatively small amplitude between the troughs (lowpressure systems) and ridges (high-pressure systems). The present north-south seasonal meandering of the jet stream was also less. Thus, in the models precipitation and temperatures were more uniform throughout the year and there was less regional differentiation in climate. CO2 concentrations during the Cretaceous are estimated to have been 4-8 times to 10-12 times higher than at present. With a 2-5°C warming for each doubling of CO2, this provides part of the explanation for the higher MAT documented for the Late Cretaceous and Early Tertiary. High CO2 concentrations near the end of the Cretaceous may have been a holdover from earlier intense volcanism in the South Pacific that began to subside at ~ 100 Ma. The term epeirogeny refers to vertical motions of the Earth’s crust, and these movements affect the ocean floor, as well as the continents. There was a 50% increase in the production of ocean crust in the Middle Cretaceous compared to earlier times, as represented by the early Aptian Ontong Java Plateau, the Earth’s largest oceanic plateau, now submerged over 2 km off the Solomon Islands. A sense of the magnitude of this structure can be gained by comparing its volume with that of the surface-exposed Deccan Traps of India (66 Ma). The latter are ~1 km thick and have a volume of 1.5 x 106 km3. The Ontong Java Plateau is ~36 km thick and has a volume of 50 x 106 km3.
Off-line Serial Exact String Searching
Authors: Crochemore M.
Published: November 2020

String searching or string-matching is the problem of locating all occurrences of a string x of length m, called the pattern, in another string t of length n, called the text. The algorithmic complexity of the problem is analyzed by means of standard measures: running time and amount of memory space required by the computations. This chapter deals with solutions in which the pattern only is preprocessed. There are mainly three kinds of methods to solve the problem: sequential methods simulating a finite automaton, practically fast methods, and time-space optimal methods. Alternative solutions based on a preprocessing of the text are described in Chapter 3. Parallel algorithms for the problem, presented in Chapter 2, sometimes also generate new serial algorithms. Finally, methods that search for approximate occurrences of a pattern are the subject of Chapters 4, 5, and 6. The problem is of main importance for several reasons. From a theoretical point of view, it is a paradigm for the design of efficient algorithms, in the same way as are, for instance, sorting methods. From a practical point of view, the algorithms developed in this chapter often serve as basic components in text facility software. In the whole chapter, x denotes the pattern of length m (m = |x|), and t is the text of length n (n = |t|). To avoid trivial situations, the pattern is assumed to be a non-empty string (x ≠ λ, m ≠ 0). Since the problem becomes a simple counting exercise when the alphabet reduces to only one symbol, the reader may consider in the following that the common alphabet Σ of the text and the pattern contains at least two symbols (|Σ| > 1). We assume that the pattern is given first. The text is given at search time only. This allows us to preprocess the pattern in order to accelerate the future search in the text. An instance of the problem arises when we try to recognize a specific pattern in various texts or streams of symbols arriving through a communication channel.
Parallel Computations of Levenshtein Distances
Authors: Apostolico A. , Atallah M.J.
Published: November 2020

This chapter discusses parallel solutions for the string editing problem introduced in Chapter 5. The model of computation used is the synchronous, shared - memory machine referred to as PRAM and discussed also earlier in this book. The algorithms of this chapter are based on the CREW and CRCW variants of the PRAM. In the CREW - PRAM model of parallel computation concurrent reads are allowed but no two processors can simultaneously attempt to write in the same memory location (even if they are trying to write the same thing). The CRCW - PRAM differs from the CREW - PRAM in that it allows many processors to attempt simultaneous writes in the same memory location: in any such common-write contest, only one processor succeeds, but it is not known in advance which one. The primary objective of PRAM algorithmic design is to devise algorithms that are both fast and efficient for problems in a particular class called NC. Problems in NC are solvable in O(logo(1) n) parallel time by a PRAM using a polynomial number of processors. In order for an algorithm to be both fast and efficient, the product of its time and processor complexities must fall within a polylog factor of the time complexity of the best sequential algorithm for the problem it solves. This goal has been elusive for many simple problems, such as topological sorting of a directed acyclic graph and finding a breadth-first search tree of a graph, which are trivially in NC. For some other problems in NC, it seems counter-intuitive at first that any fast and efficient algorithm may exist, due to the overwhelming number of simultaneous subproblems that arise at some point of the computation. Such is the case of the string-editing problem. This chapter will show that string editing can be solved in O((log n)2) time and O(n2/ log n) processors on the CREW-PRAM, and in O(log n loglog n) time and O(n2/ loglogn) processors on the CRCW-PRAM. Throughout, it will be convenient to analyze our algorithms using the time and work (i.e., number of operations) complexities.
Shortest Common Superstrings
Authors: Li M. , Jiang T.
Published: November 2020

Given a finite set of strings S = {s1,...,sm}, the shortest common superstring of S, is the shortest string s such that each si appears as a substring (a consecutive block) of s. . . . Example. . . . . . . Assume we want to find the shortest common superstring of all words in the sentence “alf ate half lethal alpha alfalfa.” Our set of strings is S = { alf, ate, half, lethal, alpha, alfalfa }. A trivial superstring of S is “alfatehalflethalalphaalfalfa”, of length 28. A shortest common superstring is “lethalphalfalfate”, of length 17, saving 11 characters. The above example shows an application of the shortest common superstring problem in data compression. In many programming languages, a character string may be represented by a pointer to that string. The problem for the compiler is to arrange strings so that they may be “overlapped” as much as possible in order to save space. For more data compression related issues, see next chapter. Other than compressing a sentence about Alf, the shortest common superstring problem has more important applications in DNA sequencing. A DNA sequence may be considered as a long character string over the alphabet of nucleotides {A, C, G, T}. Such a character string ranges from a few thousand symbols long for a simple virus, to 2 x 108 symbols for a fly and 3 x 109 symbols for a human being. Determining this string for different molecules, or sequencing the molecules, is a crucial step towards understanding the biological functions of the molecules. In fact, today, no problem in biochemistry can be studied in isolation from its genetic background. However, with current laboratory methods, such as Sanger’s procedure, it is quite impossible to sequence a long molecule directly as a whole. Each time, a randomly chosen fragment of less than 500 base pairs can be sequenced. In general, biochemists “cut”, using different restriction enzymes, millions of such (identical) molecules into pieces each typically containing about 200-500 nucleotides (characters). A biochemist “samples” the fragments and Sanger’s procedure is applied to sequence the sampled fragment. . . .
Tree Pattern Matching
Authors: Zhang K. , Shasha D.
Published: November 2020

Most of this book is about stringology, the study of strings. So why this chapter on trees? Why not graphs or geometry or something else? First, trees generalize strings in a very direct sense: a string is simply a tree with a single leaf. This has the unsurprising consequence that many of our algorithms specialize to strings and the happy consequence that some of those algorithms are as efficient as the best string algorithms. From the point of view of “treeology”, there is the additional pragmatic advantage of this relationship between trees and strings: some techniques from strings carry over to trees, e.g., suffix trees, and others show promise though we don’t know of work that exploits it. So, treeology provides a good example area for applications of stringologic techniques. Second, some of our friends in stringology may wonder whether there is some easy reduction that can take any tree edit problem, map it to strings, solve it in the string domain and then map it back. We don’t believe there is, because, as you will see, tree editing seems inherently to have more data dependence than string editing. (Specifically, the dynamic programming approach to string editing is always a local operation depending on the left, upper, and upper left neighbor of a cell. In tree editing, the upper left neighbor is usually irrelevant — instead the relevant cell depends on the tree topology.) That is a belief not a theorem, so we would like to state right at the outset the key open problem of treeology: can all tree edit problems on ordered trees (trees where the order among the siblings matters) be reduced efficiently to string edit problems and back again?. The rest of this chapter proceeds on the assumption that this question has a negative response. In particular, we discuss the best known algorithms for tree editing and several variations having to do with subtree removal, variable length don’t cares, and alignment. We discuss both sequential and parallel algorithms.
Soil Physics
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

Soil physics deals with physical properties of soils such as soil texture, porosity, soil water, soil aeration, soil temperature, soil structure, and the influence of these properties on plant growth. Soil texture refers to the particle-size distribution of soils. The primary soil particles are arbitrarily divided into different size classes. The International Society of Soil Science defines soil particles larger than 0.02 mm and smaller than 2 mm as sand, those larger than 0.002 mm but smaller than 0.02 mm as silt, and those smaller than 0.002 mm as clay. Soil particles larger than 2 mm, such as gravel and stones, are called coarse fragments and are not part of the soil itself, to which the term soil texture applies, but can have considerable influence on soil properties and plant growth. Sand particles (0.02-2 mm) can be further divided into fine sand (0.02-0.2 mm) and coarse sand (0.2-2 mm). Sand particles can be rounded or angular, and are noncohesive. They usually consist of a single mineral, usually quartz (SiO2) or other primary silicate, and may appear brown, yellow, or red as a result of Fe-oxide coatings. Due to its mineral composition, sand has a smaller plant-nutrient content than finer soil particles. Sand particles have large voids between them which promote drainage of water and entry of air into the soil. Due to their low specific surface area, sand particles can hold little water, therefore rain needs to be received at short intervals to enable plant growth on sandy soils. Silt particles (0.002-0.02 mm) do not feel gritty when rubbed between fingers and are not visible to the unaided eye as sand particles are. Quartz is generally the dominant mineral. However, when silt is composed of weatherable minerals, the release of plant nutrients can be significant. The pores between silt particles are smaller and more numerous than those in sand, and silt therefore retains more water than sand, which helps to sustain plant growth. Silt itself does not exhibit much stickiness or plasticity and is therefore easily washed away by water. If silt fractions have some cohesion and adsorptive capacity, it is due to a film of adhering clay particles.
Soil Formation and Classification
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

Soil is the superficial layer of the land area of the Earth and contains weathered inorganic materials, organic matter, air, and water. The branch of soil science that studies the formation and classification of soils is termed pedology. For both scientific and technical purposes, soils around the world are organized into various categories on the basis of their differences and similarities. There are two types of soil classification schemes: (i) the scientific or pedological classification schemes which group soils on the basis of morphological, physical, chemical, and mineralogical properties as well as stage of weathering; and (ii) the technical or practical classification schemes which group soils based on selected properties for specific applications in agriculture and urban development, such as making a quick appraisal of soil fertility capability of farmlands or determining the suitability of septic tank installations of a housing development site. Soils are formed from the weathering of rocks and rock debris that have been eroded and transported by water, wind, ice, or gravity to other sites within the landscape. The soil, together with any underlying weathered debris and/or weathered bedrock, is termed regolith. The formation of soils from rock and minerals may take a long period of time, that is, thousands or millions of years. The pathways of soil formation are shown in fig. 7-1. The development of distinct characteristics of a soil profile or pedon involves physical, chemical, and biological weathering processes. The weathering process that involves the breakdown of rock and minerals by the action of water, pressure, heat, and freeze, into increasingly smaller fragments or particles is called physical weathering. The processes that involve hydrolysis, dissolution, and the formation of secondary minerals, such as clay-sized layer silicates and Fe and Al oxides, are called chemical weathering. The two important and interrelated chemical processes of tropical weathering are desilication and laterization. Desilication involves the dissolution of silicate minerals, and the subsequent leaching of dissolved silica from the soil profile by rain. The loss of silica from the soil eventually leads to the formation and accumulation of Fe and Al oxides in the soil, a weathering process known as laterization.
Major Arable Soils of the Tropics :A Descriptive Grouping Based on Clay Mineralogy
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

Several pedological soil classification schemes have been developed to classify soils worldwide based on morphological features, stage of weathering, and to some extent their chemical and physical properties. Three soil classification systems are commonly used as research and teaching tools in the tropics, namely, the USDA Soil Taxonomy classification, the FAO/UNESCO World Soil Legends, and the French soil classification system. Brazil, the country with the largest land area in the tropics, has its own national soil classification system. However, soil survey, classification, and interpretation are costly and time-consuming, and few countries in the tropics have completed soil maps that are at a scale detailed enough to be useful to farmers and land users. In the absence of soil information at state, county or farm level, the authors propose a simple descriptive grouping of major soils in the tropics based on clay mineralogy to facilitate discussion on soil management and plant production in the subsequent chapters of this book. Reference to the Soil Taxonomy classification will be made when such information is available. It should be pointed out that the main purpose of this technical grouping is to provide field workers, especially those who are less familiar with the various soil classification systems, with a simple framework for planning soil management strategies. It by no means replaces the national and international soil taxonomy and classification systems that are designed for communication among soil scientists and for more detailed interpretation of soil survey data and land-use planning. This technical scheme classifies major arable soils in the tropics into four groupings according to their dominant clay mineralogy. They are • kaolinitic soils • oxidic soils • allophanic soils • smectitic soils Kaolinitic soils are deeply weathered soils with a sand, loamy sand, or sandy loam texture in the surface horizon and a clayey B horizon (20-60%). Silt content is low (< 20%) throughout the profile. Kaolinite (> 90%) is the dominant mineral in the clay fraction. These soils have an effective CEC of less than 12 cmol/kg of clay in the lower B horizon. Kaolinitic soils have a relatively high bulk density, especially in the clayey subsoil horizons (> 1.40 Mg/m3). The structure of the subsoil horizons is usually massive or blocky.
Soils and Sustainable Agriculture : Ecological Considerations
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

Sustainable agriculture can be defined in many different ways. In industrial nations, sustainable agriculture means improving energy use efficiency, reducing environmental pollution, and increasing and sustaining profitability. For millions of small-holder farmers throughout the tropics, sustainable agriculture means providing basic food needs for the farming family, improving the farmer’s ability to replenish soil nutrients and control soil degradation, and optimizing crop yield per unit area of land. Soil utilization for agricultural production in the tropics during the past two centuries, to a large extent, has been influenced by the technological and economic changes in temperate regions. Research and development for agriculture during the colonial era were mainly focused on the needs of industrial nations, while the production of food crops for the indigenous inhabitants was largely left in the hands of the traditional slash-and-burn cultivators. Large and small cash crop plantations were developed on fertile, high-base-status allophanic and oxidic soils for coffee, cocoa, banana, and sugarcane production throughout the humid and subhumid tropics. Cotton was cultivated on smectitic soils and high-base-status kaolinitic soils in the subhumid and semiarid regions of Africa for the textile industries in temperate regions. In tropical America, cattle ranching, a production system introduced by European immigrants, still occupies most of the fertile flat land today, while food grains are usually cultivated on less fertile land or in shallow soils on steep slopes. In tropical Africa and Latin America, a wide range of food crops, such as maize and beans, potato, cowpea, sorghum, millet, cassava, and yam are mostly produced under the traditional slash-and-burn system of cultivation on less fertile kaolinitic soils. In tropical Asia, the indigenous intensive rice-based agriculture on wet smectitic soil has been practiced over many centuries and has been able to meet the basic food needs for the increasing population in the region. Generally, upland food crop production in the tropics has not kept pace with human population growth in the tropics during the past century. It was not until the 1950s and 1960s, following the independence of many nations in tropical Asia and Africa, that more attention was given to the research and development of food crop production.
Technology and Investment
Authors: Rostow W. W.
Published: November 2020

Technology has been at the heart of economic growth, from the swift Dutch commercial boats of the 17th century—called "fly boats" in English—to the latest computer or product of genetic engineering at the end of the 20th century. Since the middle of the 18th century, economists have recognized two categories of technologies. Adam Smith, for example, drew a line between the inventions of those whom he called "philosophers" (and we call scientists) that involved "new powers not formerly applied" and incremental improvement in ways of doing things that more or less automatically accompanied the widening of the market and consequent specialization. Since there were limits to the widening of the market and Smith assumed his scientific inventions were sporadic, it followed that, in the end, decreasing returns would set in. The process ended as stagnation or decline when nations had acquired their "full complement of riches." However, that is not the way it happened in the last two centuries, when innovation became a flow rather than an occasional event. A preliminary word about technology and investment. Private, domestic investment is conventionally divided into nonresidential, residential, and inventories. Nonresidential investment is the sum of business structures plus producers' equipment. Residential is primarily nonfarm structures, although relatively small items for farm structures and producers' durable equipment go with these structures. Inventories fluctuate rather stably in a 3.2 to 3.5 relation to final sales. The most volatile items in this statistical array are the linked figures for business structures and equipment and residential nonfarm structures. The hypothesis at which I have arrived is that the macroeconomic convention of viewing investment as dependent on the rate of growth of consumption (or in a fixed proportion to consumption) is too aggregated a view of the investment process. Net business investment (excluding obsolescence requirements) is primarily a function of the size of the technological backlog a country has available. The bulk of business investment that takes place is a consequence of the plowback of profits.
Atmospheric Chemistry and Deposition
Authors: Sievering Herman
Published: November 2020

The two most significant elements with atmospheric components that influence ecological processes at Niwot Ridge are carbon (C) and nitrogen (N). The enrichment of the atmosphere by carbon dioxide (CO2) is ubiquitous across the globe. Global and regional patterns of the annual increases in atmospheric CO2 as well as the current and anticipated vegetation responses are the subject of ongoing analyses (e.g., Schimel 1995, 1998). Hence, except to emphasize the unique Niwot Ridge contribution to the CO2 database, the material presented in this chapter focuses primarily on N, which has a tremendous potential to influence the structure and function of ecosystems (Vitousek et al. 1997). Anthropogenic increases in atmospheric deposition can have profound effects on terrestrial and aquatic ecosystems (Ollinger et al. 1993). Of particular concern are increases in the deposition of nitrogen-containing species, including nonprecipitative, dry-deposited gaseous and particulate N, which can be an important component of the N cycle. These species may act as fertilizer N and can be utilized by vegetation and microbes with little or no energy expenditure. Estimation of the magnitude of N dry plus wet deposition to alpine tundra and subalpine forest ecosystems of Niwot Ridge is integral to understanding N cycling within these systems. This chapter focuses on the estimation of N deposition to the alpine tundra and, to a lesser extent, to the adjacent subalpine forest. The first section presents a brief review of the chemistry of the air environment over Niwot Ridge. The next section discusses the processes of N deposition and exchange with the alpine landscape, source regions for the N in the air over Niwot Ridge, and a procedure for determining atmospheric deposition from ambient air concentrations. Evidence is presented that anthropogenic sources contribute the majority of N in regional air masses and thus to total N deposition. The role that ammonia gas may play in reducing or enhancing N deposition is also described. The contribution that N deposition may make to N accumulation in the subalpine forest ecosystem below Niwot Ridge is briefly discussed in the final section.
Geomorphic Systems of Green Lakes Valley
Authors: Caine Nel
Published: November 2020

There are at least three justifications for the examination of the geomorphology of the area in which ecosystem studies are conducted. First, the present landscape and the materials that make it up provide the substrate on which ecosystem development occurs and may impose constraints, such as where soil resources are limited, on that development. Second, the nature of the landscape and the geomorphic processes acting on it often define a large part of the disturbance regime within which ecosystem processes occur (Swanson et al. 1988). Third, the processes of weathering, erosion, sediment transport, and deposition that define geomorphic dynamics within the landscape are themselves ecosystem processes, for example, involving the supply of resources to organisms. In this last context, it is noteworthy that drainage basins (also called watersheds or catchments) were recognized as units of scientific study during a similar time period in both geomorphology and ecology (Slaymaker and Chorley 1964; Bormann and Likens 1967; Chorley 1969). The drainage basin concept, the contention that lakes and streams act to integrate ecological and geomorphic processes, remains important in both sciences and underlies the studies in Green Lakes Valley reviewed here. Over the past 30 years, Niwot Ridge and the adjacent catchment of Green Lakes Valley have been the subject of much research in geomorphology. Building on the studies of Outcalt and MacPhail (1965), White (1968), and Benedict (1970), work has emphasized the study of present-day processes and dynamics, especially of mass wasting in alpine areas. These topics have been reviewed by Caine (1974, 1986), Ives (1980), and Thorn and Loewenherz (1987). Studies of geomorphic processes have been conducted in parallel with work on Pleistocene (3 million to 10,000 yr BP) and Holocene (10,000 yr BP to present) environments in the Colorado Front Range (Madole 1972; Benedict 1973) that have been reviewed by White (1982). This chapter is intended to update those reviews in terms that complement the presentation of ecological phenomena such as nitrogen saturation in the alpine (chapter 5) as well as to refine observations and conclusions of earlier geomorphic studies.
Plant-Herbivore Interactions
Authors: Dealing Denise
Published: November 2020

The alpine provides a tremendous opportunity for studying plant-herbivore interactions at the population, community, and ecosystem levels. For herbivores, variations in topography and microclimate result in a relatively large amount of spatial variation in plant communities within short distances (chapter 6). A large community of herbivores, from nematodes to grasshoppers to elk, occurs on Niwot Ridge. Furthermore, given the low rates of nutrient availability in alpine soils (Fisk and Schmidt 1995; chapter 12) combined with the slow-growing perennial habit of the vegetation, alpine plants should, in theory, invest heavily in defense against herbivores (Coley et al. 1985). The goal of this chapter is to provide: (1) a summary of the feeding behaviors of the herbivores on Niwot Ridge, (2) information on the nutritional and secondary chemistry of plants on Niwot Ridge as it relates to herbivory, and (3) a review of hypotheses on community dynamics of herbivores and plants relevant to the alpine. The ultimate objective is to provide a synthesis of information that will stimulate interest in alpine tundra as a system for studying the dynamics of plant-herbivore interactions at all levels of ecological organization. The flora of Niwot Ridge has been divided into six communities (May and Webber 1982; chapter 6). Regardless of community association, nearly all of the plant species occurring on the ridge are perennials and several are very long lived (May and Webber 1982). Communities can change across small spatial scales (meters), and community origin and maintenance are believed to be largely determined by abiotic factors (Walker et al. 1994; chapter 6). However, several studies suggest that biotic factors such as herbivory may have a significant impact on plant community dynamics (Huntly et al. 1986; Davies 1994). There is significant variation in the nutritional composition of plants on Niwot Ridge. Generally, and in the absence of plant secondary compounds, species that are high in nitrogen and low in fiber are presumed to be the most desirable as forage. Based solely on these nutritional variables, the clover Trifolium parryi is hypothesized to be one of the more-preferred forages, whereas alpine sandwort, Minuartia obtusiloba, should be one of the less-preferred food items.
Paleoecology and Late Quaternary Environments of the Colorado Rockies
Authors: Elias Scott A.
Published: November 2020

Present-day environments cannot be completely understood without knowledge of their history since the last ice age. Paleoecological studies show that the modern ecosystems did not spring full-blown onto the Rocky Mountain region within the last few centuries. Rather, they are the product of a massive reshuffling of species that was brought about by the last ice age and indeed continues to this day. Chronologically, this chapter covers the late Quaternary Period: the last 25,000 years. During this interval, ice sheets advanced southward, covering Canada and much of the northern tier of states in the United States. Glaciers crept down from mountaintops to fill high valleys in the Rockies and Sierras. The late Quaternary interval is important because it bridges the gap between the ice-age world and modern environments and biota. It was a time of great change, in both physical environments and biological communities. The Wisconsin Glaciation is called the Pinedale Glaciation in the Rocky Mountain region (after terminal moraines near the town of Pinedale, Wyoming; see chapter 4). The Pinedale Glaciation began after the last (Sangamon) Interglaciation, perhaps 110,000 radiocarbon years before present (yr BP), and included at least two major ice advances and retreats. These glacial events took different forms in different regions. The Laurentide Ice Sheet covered much of northeastern and north-central North America, and the Cordilleran Ice Sheet covered much of northwestern North America. The two ice sheets covered more than 16 million km2 and contained one third of all the ice in the world’s glaciers during this period. The history of glaciation is not as well resolved for the Colorado Front Range region as it is for regions farther north. For instance, although a chronology of three separate ice advances has been established for the Teton Range during Pinedale times, in northern Colorado we know only that there were earlier and later Pinedale ice advances. We do not know when the earlier advance (or multiple advances) took place. However, based on geologic evidence (Madole and Shroba 1979), the early Pinedale glaciation was more extensive than the late Pinedale was.
Introduction: The Instability of Scientific Truth
Authors: Oreskes Naomi
Published: November 2020

Scientists are interested in truth. They want to know how the world really is, and they want to use that knowledge to do things in the world. In the earth sciences, this has meant developing methods of observation to determine the shape, structure, and history of the earth and designing instruments to measure, record, predict, and interpret the earth’s physical and chemical processes and properties. The resulting knowledge may be used to find mineral deposits, energy resources, or underground water; to delineate areas of earthquake and volcanic hazard; to isolate radioactive and toxic wastes; or to make inferences and predictions about the earth’s past and future climate. The past century has produced a prodigious amount of factual knowledge about the earth, and prodigious demands are now being placed on that knowledge. The history of science demonstrates, however, that the scientific truths of yesterday are often viewed as misconceptions, and, conversely, that ideas rejected in the past may now be considered true. History is littered with the discarded beliefs of yesteryear, and the present is populated by epistemic resurrections. This realization leads to the central problem of the history and philosophy of science: How are we to evaluate contemporary science’s claims to truth given the perishability of past scientific knowledge? This question is of considerable philosophic interest and of practical import as well. If the truths of today are the falsehoods of tomorrow, what does this say about the nature of scientific truth? And if our knowledge is perishable and incomplete, how can we warrant its use in sensitive social and political decision-making? For many, the success of science is its own best defense. From jet flight to the smallpox vaccine, from CD players to desktop scanners, contemporary life is permeated by technology enabled by scientific insight. We benefit daily from the liberating effects of petroleum found with the aid of geological knowledge, microchips manufactured with the aid of physical knowledge, materials synthesized with the aid of chemical knowledge. Our view of life — and death — is conditioned by the results of scientific research and the capabilities of technological control.
The Depersonalization of Geology
Authors: Oreskes Naomi
Published: November 2020

Some historians have concluded that plate tectonics caused a change in the standards of the geological community, but the shift in standards of the American scientific community was not so much the result of the development of plate tectonics as it was a larger trend that helped to cause it. Geologists consciously chose to move their discipline away from observational field studies and an inductive epistemic stance toward instrumental and laboratory measurements and a more deductive stance. This shift helps to explain why geologists felt compelled to attend to the demands of geodesists even at the expense of their own data: it was the geodesists’ data, rather than their own, that seemed to be in the vanguard of their science. Geologists at the start of the twentieth century had high hopes for their discipline, and they were not disappointed. The Carnegie Institution’s Geophysical Laboratory became one of the world’s leading locales for laboratory investigations of geological processes, and work done there inspired scientists at other American institutions. At Harvard, for example, Reginald Daly joined forces with Percy Bridgman to raise funds for a high pressure laboratory to determine the physical properties of rocks under conditions prevailing deep within the earth. The application of physics and chemistry to the earth was also advanced at the Carnegie’s Department of Terrestrial Magnetism, where scientists pursued geomagnetism, isotopic dating, and explosion seismology.’ By mid-century, the origins of igneous and metamorphic rocks had been explained, the age of the earth accurately determined, the behavior of rocks under pressure elucidated, and the nature of isostatic compensation resolved, largely through the application of instrumental and laboratory methods. Similar advances occurred in geophysics and oceanography. The work that Bowie and Field instigated in cooperation with the U.S. Navy, and that scientists at places like Wood’s Hole and the Scripps Institution of Oceanography greatly furthered, had grown by the 1950s into a fully fledged science of marine geophysics and oceanography with abundant financial and logistical backing. This work —in gravity, magnetics, bathymetry, acoustics, seismology— relied on instrumentation, much of it borrowed from physics.
Regional Setting of the Jornada Basin
Authors: Mack Greg H. , Nolen Barbara A.
Published: November 2020

Within the area around Las Cruces, New Mexico, is a network of studies both at the Jornada Experimental Range (JER) and the Chihuahuan Desert Rangeland Research Center (CDRRC), which includes the Desert Soil-Geomorphology Project. All of these research entities are in the Chihuahuan Desert; this chapter describes the geologic history and development of landscapes that are important elements to our understanding of this ecosystem and its dynamic nature. Southern New Mexico consists of C3 shrubs and C4 grasses in the lower elevations surrounded by C3 woodlands and juniper savannas in the higher elevations (Dick-Peddie 1993; see also chapter 10). Although the boundary of the Chihuahuan Desert has differed slightly depending on whether it was based on vegetative or climatic criteria, the boundary most widely used is based on a de Martonne aridity index of 10 (Schmidt 1979). Like many deserts of the world, the Chihuahuan Desert is in a zone of dry, high-pressure cells near 30° latitude; is relatively far from marine moisture sources; and occupies a position in which mountains scavenge moisture from weather fronts (Strahler and Strahler 1987). The orographic influence is especially important in Mexico, which contains about threefourths of the Chihuahuan Desert, because the desert is bounded to the west by the Sierra Madre Occidental and to the east by the Sierra Madre Oriental Mountains. The basin and range province consists of north–south trending mountain ranges and broad intervening desert basins that at the Jornada Basin site is the product of the Rio Grande rift tectonic system, which has been active since middle tertiary time (Seager 1975; Seager et al. 1984). Erosion of the steeply tilted mountain ranges has been the main source of sediment for the filling of the intermontane basins. Vertically, sedimentary deposits are separated by paleosols that indicate quiescent times following periods of erosion and sedimentation. As the basins filled with sediment, pore spaces between sediment particles filled with water from rain, making these structural basins large reservoirs of ground water (Hawley and Lozinsky 1992; Hawley and Kennedy 2004).