bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion-Linked Microbial Metabolism in the Vadose Zone
Authors: Watson J. E. , Harris R. F.
Published: November 2020

Figure 7.1 is a schematic of nutrient and contaminant transformations and cycling in the vadose zone. As detailed in Harris and Arnold (1995), higher plants take up C, N, P, and S in their most oxidized forms and use, via photosynthesis, the Sun’s energy and low-energy electrons from the oxygen in water to convert the oxidized forms of these essential elements into the relatively high energy reduced forms comprising plant biomass. Following plant death, the biomass residues enter the soil and are attacked by soil organisms as a source of food. The plant residues are depolymerized and the reduced, high-energy monomers are assimilated in part into soil organism biomass, and in part are used as electron donors to combine with the most thermodynamically efficient electron acceptors for dissimilatory energy generation to drive growth and maintenance reactions. In aerobic zones, oxygen is the preferred electron acceptor as long as it is nonlimiting. Death of soil organisms produces dead biomass which re-enters the biological reactor. Ultimately, via respiration in aerobic soils, all the reduced C, N, P, and S materials are released as their oxidized forms, and oxygen is reduced to water to complete the cycle. Ideally, the cycle is conservative, particularly from the standpoint of nonleakage of nutrients, such as nitrate, into the groundwater. Similarly, contaminants entering the vadose zone, either as a function of agronomic use or by accident, should ideally be integrated into the natural nutrient cycles and converted to harmless by-products for assimilation and dissimilation by soil organisms and higher plants (Liu, 1994). Management of nutrient and contaminant transformations by the soil organisms requires a thorough understanding of the ecophysiological and solute transport ground rules that control the nature and rates of transformation options available to the soil organisms. In models of chemical transport and transformation through the vadose zone, colonies of microorganisms are frequently treated as a homogeneous biofilm reactor (Grant and Rochette, 1994). Often, modeling efforts are focused on environmental conditions external to the microbial colony. This consideration of the colony as a biofilm with relatively constant nutrient uptake rates ignores the growth differentiation that occurs as the colony develops
Wheat Breeding and the Consolidation of Indian Autonomy, 1940-1970
Authors: Perkins John H.
Published: November 2020

Between 1940 and 1970, India vastly increased its wheat-breeding efforts, which in turn became part of the country’s capacity for high-yielding agriculture. These changes in agricultural science and production practices were by no means incidental to Indian politics. On the contrary, the embrace of science and high-yielding practices was the result of intense debate and experimentation with a number of policies. On the surface, the arguments were about how best to increase food production, but the debates had a far deeper meaning. They touched the very heart and soul of what independent India was to be, and on their outcome rested India’s ability to be an autonomous nation. The debate sharpened its focus at independence in 1947, when a single question became paramount: Should India aspire to be an industrialized, urban society? Or should India create a more prosperous but agrarian society based on hundreds of thousands of largely self-sufficient rural villages? Finding an acceptable answer to this question posed far more difficult problems for Indian politics than the central question that had existed for nearly a century: how to get the British to leave. During the three decades from 1940 to 1970, India at various times (1) expanded the amount of land devoted to food production; (2) managed food shortages through a system of price control and state procurement of grain; (3) launched community development programs in an attempt to raise the well-being of villages in an egalitarian way; (4) obtained grants and low-cost sales of surplus wheat from the United States and elsewhere in order to cover its food production deficit; and (5) embraced the promise of science to increase yields, reluctantly at first, then enthusiastically. In the end, it was the science, particularly the key contributions of plant breeding, that tipped the balance toward higher levels of wheat production. Repercussions of the ideological clashes involved in making this choice continue within India even today. This chapter covers the events in three phases. First, at independence India was already in a food crisis caused by the collapse of food production in the last years of the British raj and the effects of partition.
Introductio
Authors: Holman J. Alan
Published: November 2020

There is disagreement about the time of the beginning of the Pleistocene. For instance, Repenning (1987), a North American, puts the beginning date at 1.9 million ybp. On the other hand, some modern Europeans studying the subject (e.g., Gibbard et al., 1991; Kolfschoten and Meulen, 1986; Roebroeks and Kolfschoten, 1995; Zagwijn, 1985, 1992) consider the epoch to have begun about 2.3 million ybp. The system used here, however, follows Sanchiz (in press), who accepts the official usage of Harland et al. (1990), who put the beginning of the Pleistocene at 1.64 million ybp. Evidence that the Pleistocene ended about 10,000 ybp (Meltzer and Mead, 1983) is widely accepted. This ending date correlates very closely with the terminal extinction of many large land mammal species. The Pleistocene is characterized by climatic oscillations and a series of glacial and interglacial events where great continental ice sheets advanced and retreated many times. The ice sheets were massive forces, sculpting the topography of the land and carrying much sedimentary material, including huge boulders and even megablocks of land up to 4 km in diameter, as far as 250 km in the Canadian prairies (MacStalker, 1977). In Britain and Europe, as well as in North America, the advance and retreat of ice sheets had a marked effect on the distribution of plant and animal life. Huge tracts of habitat were alternately obliterated and reopened several times, but other effects perhaps arc not so well known. For instance, during glacial times, so much atmospheric water was tied up in the formation of the ice that sea levels worldwide lowered markedly. On the other hand, sea levels rose during interglacial times when water was melting off the ice sheets. The most interesting and controversial biological event that took place in the Pleistocene was the sudden, almost worldwide, extinction of large land mammals, and to a lesser extent birds, that took place by the end of the epoch 10,000 years ago. At least 200 mammalian genera became extinct, among them large herbivores, the carnivores that preyed on them, and the scavengers that fed on the remains of both groups.
“Who Has the Youth, Has the Future”
Authors: Rodden John G.
Published: November 2020

Experiencing everyday life in another culture places your own in stark relief. Assumptions stand revealed, often by utterly minor objects and events. Consider, for instance, bananas. Bananas? We Americans take them for granted, we even trivialize them—playing second banana, being driven bananas, going bananas, and on and on. But not so in Germany. To Germans, bananas are not such a light-hearted matter. As one well-known Cologne artist who has stenciled his Andy Warhol–style, Day- Glo bananas on the outer walls of hundreds of art galleries has proclaimed: “Bananas are almost a holy object in Germany.” Banana-crazed Germans, joked Der Stern in 1992, are “the apes of the EC.” These exaggerations warrant our attention. For bananas are an impossibly overdetermined symbol in Germany, signifying justice, national self-determination, cultural pride, deprivation, prosperity, communist tyranny, capitalist luxury, unity, and economic and even sexual freedom. The banana occupies a special place in Germany’s national psyche and in the history of German re-education, given its role in both early postwar reconstruction and recent reunification. Let us therefore examine that role at some length here, for it turns out that “banana politics” bears revealingly, if unexpectedly and often amusingly, on the issues of German identity and German re-education—and reflects Teutonic tensions both within and outside reunited Germany. Ever since hunger overtook war-torn, occupied Germany in the mid-1940s, when even basic foodstuffs were unobtainable, bananas have symbolized Plenty to both western and eastern Germans—the plenty western Germans eventually obtained, the plenty eastern Germans always lacked. In West Germany, the early postwar generation endured rationing and shortages until mid-century. As children, many of them knew of bananas only through the reminiscences of their elders. For them the fruit still evokes childhood memories of humiliation, dispossession, and hunger. All this began to change in West Germany with the Wirtschaftswunder (economic miracle) of the 1950s. West German parents delightedly weaned their infants on “Banana Salad” baby food, the leading seller of Hipp, the Gerber’s of West Germany.
After the Wall II: The Fall and Rise of an Educational System
Authors: Rodden John G.
Published: November 2020

In the fall of 1990, a hit movie comedy opened to packed houses in eastern German theaters. Go, Trabi, Go!—the producers gave the film an English title—celebrated with rollicking Weltschmerz the misadventures of Georg, a hapless baby-blue Trabant 601—whose jinxed capers make him the undeniable screen successor to Herbie, the Disney VW Beetle of the 1960s. Georg stalls pitifully on the Autobahn, is shorn of his bumper in Munich traffic, is robbed of all four tires by pranksters during a camping stop, and even gets mistaken for scrap near an auto junkyard, an obvious metaphor for the DDR running out of gas—as it lurches toward unity. Go, Trabi, Go! begins with DDR German teacher Udo Struutz deciding to fulfill a long-deferred dream: his first journey to the West will be to travel from his hellhole hometown of industrial Bitterfield, the dirtiest city in all of Eastern Europe, to balmy Naples, thereby tracing the footsteps of his beloved Goethe, whose Italian Journey recorded his own (less quixotic) southern pilgrimage from Weimar in the 1780s. Herr Struutz packs his wife and daughter into little Georg, a family member for 20 years whom Herr Struutz lovingly wipes down with his own washcloth. “See Naples and Die!” scrawls Herr Struutz on Georg’s trunk, recalling Goethe’s clarion call to self-actualization: “Sterbe und werde!” (“die and become!”). The adventure turns out to be a story of Innocent Ossis Abroad and their psychological collision with the West. Numerous scenes in Go, Trabi, Go! allude to the region’s plight: putt-putting along on the Autobahn, little Georg strains to do his maximum speed of 60 mph as contemptuous Mercedes-Benzes, Porsches, and BMWs fly by; broken-down in Bavaria, Georg costs the Struutz family a steep (an outrageously inflated) price for repair, which the intrepid socialist entrepreneurs earn by charging curious Bavarians DM 5 for a “Trabi Peep Show” and a five-minute joy ride in Georg. Reassuringly, the Struutz family eventually does reach its destination, albeit with the accident-prone but indomitable Georg—now minus his top—as a breezy convertible.
Leipzig, 1993 Of Sport, State, and Stasi: Socialism with an Un-Beautiful Face
Authors: Rodden John G.
Published: November 2020

Back again in the so-called Heldenstadt (city of heroes), as the faded bumper stickers on a few cars remind me. Is the word now tinged with irony? Though the city is in the middle of a construction boom, Leipzigers are the first to tell you that the city’s heroic image has been badly tarnished in the last few years. A warm mid-September afternoon in the smoggy city center. I take a seat in one of the cafes that dot the streets near the University. Students sit inside with books in their laps, talking animatedly to one another. Across the street is the Leipzig railway station—before the war, it was the biggest in Europe—and the Gewandhaus, where the Leipzig orchestra plays. Kurt Masur, who helped negotiate with police to hold their fire against Leipzig protesters before the city’s first mass demonstration— four years ago come October 9—is still conducting at the Gewandhaus. Otherwise, everything seems to have changed—the Leipzig smog excepted. Ute, a 23-year-old, first-year Germanistik student at the University, enters and greets me. Once an accomplished teenage ice skater in a top Sportschule—indeed, at 16, a young Privilegierte (privileged one) on her way to joining the elite traveling Sportkader—Ute is still slim and athletic. She has come to tell me about her expulsion almost a decade ago from the elect Red circle, the causes of which, she told me on the phone, “I have lately been brooding about incessantly.” She did not elaborate. I know only that the saga of her youthful rebellion against the State and her struggle to leave the DDR in 1988/89 had begun soon thereafter. Reared in Weissenfels, a town near Leipzig, Ute was born into a family of athletes. In the 1950s, her father competed on the DDR national ice hockey team and her mother was a top handball player and member of the DDR national championship squad; Ute’s older brother, Dieter, reached the Thuringia championship soccer team.
Energy for Agriculture in the Twenty-first Century
Authors: Stout B. A.
Published: November 2020

Adequate food supplies and a reasonable quality of life require energy —both noncommercial and commercial forms. Energy is a prime mover of economic growth and development. Although the linkages between energy and development are complex and still imperfectly understood, energy undoubtedly fuels economic development. And the developing countries where most of the population growth is occurring face an energy crisis of staggering proportions. An ample energy supply is not an automatic guarantee of smooth economic advancement, social progress, or stability, but it is, indisputably, their essential precondition. The future of our increasingly interdependent world will thus be very much influenced by the success or failure of the developing countries to ensure a sufficient and sustainable flow of energy (Smil and Knowland, 1980). The global inequity in the use of commercial fuels is familiar. About 1.5 billion people live in countries where the per capita consumption is less than 7 gigajoules (GJ) y-1, and another 1.1 billion consume only 7-20 GJ y -. Let’s translate this into more meaningful terms: 7 GJ is the equivalent of about 180 1 of diesel fuel —or about 0.5 1 per day to cover all human needs, such as food production and cooking, shelter, heating, and clothing. Millions and millions of rural inhabitants use virtually no commercial fuel. Clearly, no one can achieve a desirable quality of life (QOL) with so little energy available (Leach, 1979). Many studies have related GNP and energy use, but scholars debate the correlation with QOL. When one considers that energy is required to produce all the basic needs of humans, it seems apparent that a relationship as shown in Figure 5.1 may exist. Morrison (1978) carried this concept a step further by expressing QOL as a function of energy use. At low levels of energy use (quadrant III), he hypothesized that basic need satisfaction is linearly related to energy use. As the amount of energy increases (quadrant II), two paths were hypothesized. Option A projects a linear relationship between QOL and energy use, whereas option B suggests an optimum QOL at a moderately high level of energy use, followed by a deterioration of QOL due to environmental degradation at excessively high energy use rates.
Cause and Effect Factors Influencing the Composition and Distribution of North American Plant Formations through Late Cretaceous and Cenozoic Time
Authors: Graham Alan
Published: November 2020

The arrangement of vegetation over the landscape is a product of interactions between the environment, the ecological characteristics of individual organisms, barriers, dispersal potential, epidemic disease, anthropogenic influences, and the partially serendipitous factor of propagule availability. Within the complex of environmental factors, several are of special importance in tracing the history of North American plant communities. They include climate; plate tectonics as a mechanism for orogeny, volcanism, land bridges, and terranes; and catastrophes. Each have numerous interacting subcomponents, feedbacks, and amplifiers, and although constraints of format make it necessary to discuss these separately and sequentially, they are interconnected and pertubation of one affects the entire system. Diagrams summarizing these factors are presented at the end of the following sections. The diagrams are not intended as models for, indeed, the single factor of climate could be expanded into a component so vastly complex that it would be counterproductive to a general summary. Similarly, the hydrological cycle, which involves the largest movement of any substance on Earth, cannot be fully treated because a “systems” view of its role in influencing climate is not available (Chahine, 1992) and the roles of water vapor (a greenhouse gas) and cloud cover are just now being quantified (Cess et al., 1995; Ramanathan et al., 1995). Rather, the diagrams illustrate some of the factors and relationships discussed in the text and serve as a reminder of the complex interactive nature of physical and biotic events. Plants are limited in their ecological amplitude. Several important corollaries follow from this observation; one of the most fundamental is that changes in climate cause extinctions promote evolution, and alter the range and habitats of organisms. Because climate plays a central role in the arrangement of modern communities (Gates, 1993; Kareiva et al., 1993; Woodward, 1987) and in the development and distribution of past assemblages (Brenchley, 1984; Crowley and North, 1991; Hecht, 1985a), reference to some elements of general climatology is necessary for understanding the diversification, radiation, and reshuffling of North American paleocommunities during the Late Cretaceous and Cenozoic.
Quaternary North American Vegetational History: 1.6 Ma to the Present
Authors: Graham Alan
Published: November 2020

The Quaternary Period encompasses the Pleistocene and the Holocene or Recent Epochs. The date used for the beginning of the Pleistocene depends upon which globally recognizable event is selected as representing a significant break with the preceding Pliocene Epoch. Candidates include the Gauss-Matuyama magnetopolarity boundary (~2.8 Ma; see Quaternary International, 1997); the initiation of widespread permafrost, a frigid Arctic Ocean, and rapid glaciation in the high northern latitudes (~2.4 Ma; Shackleton and Opdyke, 1977; Shackleton et al., 1984); or the African Olduvai paleomagnetic event between 1.87 and 1.67 Ma. The transition from hothouse to icehouse conditions was gradual, but the Pleistocene is typified at Vrica, Italy, as beginning at ~1.67 Ma (Aguirre and Pasini, 1985; Richmond and Fullerton, 1986; oxygen isotope stage 62), and that is the date used here. In the conterminous United States the Elk Creek till of Nebraska is 2.14 m.y. in age (Hallberg, 1986), and the onset of the full ice age is represented by the onset of repeated glaciations at ~850 Kya when glaciers extended down the Mississippi River Valley. Subsequently, glacial-interglacial conditions fluctuated until the latest retreat at ~11 Kya that began the Holocene or Recent Epoch. The chronology of ice age events began with the publication of Louis Agassiz’s (1840) Etudes surles Glaciers. In the absence of evidence to the contrary, a single glacial advance was envisioned as blanketing the high latitudes. In the 1940s Willard E Libby at the University of Chicago perfected the technique of radiocarbon dating, and Flint and Rubin (1955) applied this methodology of “isotopic clocks” to establishing the absolute chronology of drift deposits from the eastern and midwestern United States. Their radiocarbon dates showed evidence of two or more times of continental-scale glaciations; older organic material was “radiocarbon inert” and beyond the ~40-Ky range of the technique. A standard chronology eventually became established for North America that included four major glacial stages (Nebraskan, oldest; Kansan; Illinoian; and Wisconsin) separated by four interglacials (Aftonian, oldest; Yarmouth, Sangamon, and the present Holocene).
Off-line Parallel Exact String Searching
Authors: Galil Z. , Yudkiewicz I.
Published: November 2020

The string matching problem is defined as follows: given a string P0 ... Pm-1 called the pattern and a string T0 .. .Tn-1 called the text find all occurrences of the pattern in the text. The output of a string matching algorithm is a boolean array MATCH[0..n — 1] which contains a true value at each position where an occurrence of the pattern starts. Many sequential algorithms are known that solve this problem optimally, i.e., in a linear O(n) number of operations, most notable of which are the algorithms by Knuth, Morris and Pratt and by Boyer and Moore. In this chapter we limit ourselves to parallel algorithms. All algorithms considered in this chapter are for the parallel random access machine (PRAM) computation model. In the design of parallel algorithms for the various PRAM models, one tries to optimize two factors simultaneously: the number of processors used and the time required by the algorithm. The total number of operations performed, which is the time-processors product, is the measure of optimality. A parallel algorithm is called optimal if it needs the same number of operations as the fastest sequential algorithm. Hence, in the string matching problem, an algorithm is optimal if its time-processor product is linear in the length of the input strings. Apart from having an optimal algorithm the designer wishes the algorithm to be the fastest possible, where the only limit on the number of processors is the one caused by the time-processor product. The following fundamental lemma given by Brent is essential for understanding the tradeoff between time and processors : Any PRAM algoriihm of time t that consists of x elementary operations can be implemented on p processors in O(x/p + t) time. Using Brent’s lemma, any algorithm that uses a large number x of processors to run very fast can be implemented on p < x processors, with the same total work, however with an increase in time as described. A basic problem in the study of parallel algorithms for strings and arrays is finding the maximal/minimal position in an array that holds a certain value.
Carbon Storage in Biomass and Soils
Authors: Bernoux Martial , Piccolo Marisa C.
Published: November 2020

Carbon dioxide and methane integrate biogeochemical cycles of C and constitute, together with nitrous oxide, the main trace gases responsible for the greenhouse effect. Increasing interest in the global consequences of climate change has prompted the global scientific community to deepen their studies about the global C stocks and the interrelations among its different compartments. As main compartments, soils and phytomass (living and nonliving) have received special attention. Many authors proposed a quantification of C stored in soils and proposed to study their role as both a source and sink of carbon (Post et al. 1982, Eswaran et al. 1993, Sombroek et al. 1993, Batjes 1996). The world’s mineral soils are estimated to contain about 1500 Pg C (Post et al. 1982, Eswaran et al. 1993, Batjes 1996), while the biomass of plants is estimated to be comprised between 560 and 835 Pg C (Whittaker and Likens 1975, Bouwman 1990). Tropical forests account for between 20 and 25% of the world terrestrial C (Brown and Lugo 1982, Dixon et al. 1994). The Amazon contains the largest expanse of native tropical ecosystems and has a direct influence on global biogeochemical cycles, especially the C cycle. The C stored in phytomass is of importance because of its quantity and its potential to be released easily. Carbon in soil is proved to be important because soil organic carbon (SOC) is intimately involved in virtually all biological processes, and organic matter (OM), even when present in small amounts, is an extremely important soil constituent. Two Brazilian soil classes, Latossolos and Podzólicos, make up 73% of the total area of the Legal Amazon Basin of Brazil (Prado 1996, Jacomine and Camargo 1996). More precisely, only three dystrofic soil types, Podzólico Vermelho Amarelo (Acrisol), Latossolo Amarelo (xanthic Ferralsol), and Latossolo Vermelho Amarelo (orthic Ferralsol) cover approximately 60% of the total, and are therefore of prime interest. The remainder is distributed between 13 additional classes. Only 6, however, represent more than one percent, and only 2 of which are more than 5%: Plintossolos (Inceptisols, Oxisols, and Alfisols) and Gleissolos (Entisols and Inceptisols).
The Tropical Environment
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

The term “tropics” refers to the continuously warm and frost-free zone of the world that lies approximately between the Tropic of Cancer (or latitude 23.5° north of the equator) and the Tropic of Capricorn (or latitude 23.5° south of the equator). The tropical region comprises approximately 36% of the world’s land surface. Geographically, the tropics encompasses the entire region of Southeast Asia, Central America, the islands in the South Pacific and the Caribbean Basin, a major part of Africa, South America, a large portion of the Indian subcontinent, and a small part of northern Australia. Within a tropical region, natural vegetation and agriculture vary with elevation and rainfall regime. Within the tropical belt, mean annual temperature at sea level is about 26 °C, and it decreases approximately 0.6 °C with every 100 m increase in elevation. On the basis of elevation, the tropics may be further divided into • lowland tropics (areas below 600 m), • midaltitude tropics (areas between 600 and 900 m), and • high-altitude tropics or tropical highlands (areas above 900 m). Tropical highlands account for 23% of the tropics whereas the low- and midaltitude regions together comprise about 87% of the total area. Tropical highlands usually have cool air temperatures with a mean annual temperature of 20 °C or lower. Rainfall on tropical highlands can be extremely variable within a short distance. Because of the year-round comfortable temperature, areas of tropical highlands with favorable rainfall and fertile soils are usually densely populated and hence intensively cultivated. Climates in the lowland and midaltitude tropics generally share three common features, namely, a year-round warm temperature, rainfall of high intensity and short duration, and a high rate of evaporation. Climates are characterized principally by mean monthly air temperature, and the amount and distribution of rainfall.
Soil Fertility
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

In the natural world, plant species evolve and adapt to specific soil and climatic conditions. The productivity and stability of a natural soil-plant continuum or ecosystem are maintained through diversity, succession, and internal nutrient cycling. Hence, there are no rich soils or poor soils but different soils supporting different ecosystems. From an agricultural viewpoint, however, the term soil fertility may be defined as the capacity of a soil, under a given rainfall or water management regime, to support the growth of common food and fiber crops with minimum or no external inputs for a long period of time without adversely degrading the chemical, physical, and biological properties of the soil. Thus, a naturally fertile or productive soil usually possesses the following features: • good soil tilth or workability • adequate organic matter content in the surface layer • adequate permeability • adequate available water-holding capacity • slightly acidic to neutral pH • loamy-textured topsoil • moderate amounts of smectite and weatherable minerals Worldwide, the most fertile soils are prairie soils derived from glacial till, young alluvial soils in river valleys and deltas and high-base-status volcanic ash soils. These soils are also known as Mollisols, high-base-status Entisols and high-base- status Andisols, respectively, according to the Soil Taxonomy classification. At the other end of the scale are the so-called infertile soils. These are the highly weathered and strongly leached soils or “lateritic soils” of the tropics. Ultisols and Oxisols rich in kaolinite and Fe and Al oxides fall into this category. The soil fertility status of other types of soils falls in between these two groups. In general, parent material and stage of weathering are good indicators of soil fertility. Moderately weathered soils derived from basic parent rocks such as basalts and limestone and recent alluvial deposits are invariably more fertile than those derived from acidic parent rocks such as sandstone, quartzite, and coarse-grained granite. Strongly weathered soils generally have a low fertility because primary minerals containing plant nutrients such as Ca, Mg, and K have long disappeared through dissolution, acidification, and leaching. The dominant clay-size minerals in strongly weathered soils, kaolinite and Fe and Al oxides, possess little capacity to retain these cations.
Soil Management: An Overview
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

The term “soil management” refers to the human manipulation of chemical, physical, and biological conditions of the soil for the production of agricultural plants. Good soil management helps maintain and improve soil fertility while sustaining optimum crop yield over time, whereas inappropriate soil management practices can lead to the degradation of soil fertility and a declining crop yield within a relatively short period of time. In a cropped field, where pests and disease are not limiting factors, the decline in crop yield over time may be attributed to several soil-related factors, namely, deterioration of soil physical conditions, such as surface crusting and subsurface compaction, depletion of available nutrients in the soil and soil acidification, soil moisture stress (drought or waterlogging), and the decline in soil organic matter and soil biological activity. Thus, major tasks of soil management for crop production include the following: • tillage and seedbed preparation • replenishment of soil nutrients • soil moisture management • maintenance of soil organic matter The main purposes of tillage are to loosen a compacted surface soil to facilitate seed emergence and root growth through improved soil aeration and water storage, and to eradicate weeds before planting and control subsequent weed growth during the cropping season. Common tillage practices used in tropical agriculture are as follows: • Slash-and-burn, followed by sowing seeds into holes made by punching a wooden stick into the porous surface soil. • Slash-and-burn, followed by heaping or ridging the compacted surface soil using a hand hoe. • Plowing, harrowing, and puddling in irrigated rice paddies using water buffalo or a two-wheel power-tiller. • Ridge tillage using a hand hoe, animal traction or an engine-powered tractor on crusted or compacted soils and poorly drained clayey soils. • Minimum or strip tillage with a crop-residue mulch on coarse-textured soils and on sloping land. • Conventional tillage involving plowing and harrowing on fine-textured soils and compacted soils on flatland. • Minimum tillage with a plant-residue mulch or cover crop in annual and tree crop mixed systems (agroforestry).
The Limits to Growth
Authors: Rostow W. W.
Published: November 2020

Economists have never believed that trees would grow to the sky. They have always assumed, explicitly or implicitly, that some forces from the side of supply or demand would produce limits to growth. In the course of these recurrent speculations, they faced and wrote about many of the issues that the world economy will face, if I am more or less correct, in the century ahead. The first five chapters of this book dealt with characteristics of growth from the 18th century to the last decade of the 20th. In that interval, by and large, most men and women in the industrial world became accustomed to think that endless growth was more or less normal and automatic. This chapter will be somewhat different. After taking the oscillations of the Chinese dynasties as an example of the limits of traditional societies, it will deal with the reflections on the limits to growth that run sporadically as a minor theme from Adam Smith to John Maynard Keynes and beyond to our own day. I will then turn to what we can say about the next half century in terms of the limits to growth. Until Europe, after some four centuries of preconditioning, invented via Britain the Industrial Revolution, the long cycle was the normal economic and political pattern of the traditional society. The Chinese theory of the long dynastic cycle, for example, is paraphrased memorably by Mary Wright:… In brief, the theory was this: A new dynasty at first experiences a period of great energy, and vigorous and able new officials put in order the civil and military affairs of the Empire. In the course of generations the new period of vigor is followed by a golden age. Territories acquired earlier arc held, but no new territories arc conquered. Learning and the arts flourish in an atmosphere of elegance. Agricultural production and the people's welfare are supported by the maintenance of peace, attention to public works, and limitations of taxes. This golden age, however, carries within it the seeds of its own decay. The governing class loses first the will and then the ability to meet the high standards of Confucian government. Its increasing luxury places a strain on the exchequer. Funds intended for irrigation, flood control, maintenance of public grain reserves, communications, and payment of the army are diverted by graft to private pockets.
Plant Nutrient Relations
Authors: Monson Russell K. , Mullen Renée
Published: November 2020

Alpine soils do not generally exhibit high levels of inorganic fertility, which is the result of inadequate mineralization of organic litter, a consequence of the cool, short alpine growing season (Rehder and Schäfer 1978; Gokceoglu and Rehder 1977; Rehder 1976a, 1976b; Fisk and Schmidt 1995; chapters 11, 12). Slow mineralization rates, in turn, result in a soil that is high in organic humus, and more likely than the soil of other ecosystems, to sequester and bind inorganic nutrients, especially N and P. Accordingly, alpine plants are exposed to a difficult situation in their efforts to obtain the inorganic ions required to support growth and reproduction. In accommodating the relative infertility of alpine soils, plants rely on a number of different traits, some of which are ubiquitous and some of which are more restricted in their distribution. Biomass allocation patterns favor high root:shoot ratios, increasing the potential for nutrient absorption by the roots relative to nutrient utilization by the shoot. Nutrient-use efficiencies (biomass produced per mass of senescent nutrient) tend to be high in alpine plants due to efficient resorption prior to leaf senescence. In several alpine growth forms, strict internal controls over seasonal phenology and growth (e.g., preformed buds and strongly enforced dormancy patterns) bring growth demands for nutrients more into balance with the limited supply provided by the soil. Luxury uptake and long-term storage during pulses of high nutrient availability provide plants with a means of bridging the gap between incongruent periods of high nutrient supply and high nutrient demand. Association of fungi with the roots of some alpine plants has the potential to enhance N and P acquisition. Finally, some alpine species can overcome the limitations imposed by scarce inorganic nutrient supplies through high rates of organic nutrient assimilation. It is the aim of this chapter to further consider each of these traits, with particular emphasis on their relationship to N and P acquisition. Topics concerning soil processes and their role in controlling nutrient availability have been covered elsewhere (chapter 8) and will not be repeated. Rather, this review focuses on nutrient relations from the plant’s perspective.
Direct and Indirect Evidence
Authors: Oreskes Naomi
Published: November 2020

At the California Institute of Technology in the mid-1940s, a young Henry William Menard—later an expert on submarine physiography and director of the U.S. Geological Survey—learned about continental drift from Beno Gutenberg. For although most American earth scientists considered the question of drift settled, many Europeans did not. Among them was “Dr. G,” famous for his pioneering work on microseisms (the continual seismic disturbances that form the background “noise” of seismographs) and deep-focus earthquakes, who had come to Caltech from Germany in 1930. In 1939, he edited Internal Constitution of the Earth, part of a series entitled Physics of the Earth sponsored by the National Research Council. Gutenberg’s chapter, “Hypotheses on the Development of the Earth’s Crust and their Implications,” focused on the evidence for a plastic crustal substrate and “currents” within it. More than just an idea, he argued, subcrustal currents were necessary—in the past and at present — to account for both isostasy and horizontal crustal dislocations: “Many writers have expressed the belief that the strength of the interior of the earth prevents any currents today. The results of geophysical research, however, leave no doubt that such currents still exist. . . . [either] as a consequence of changes produced by disturbances at the surface [or as ] the primary cause of movement at the surface.” Gutenberg’s course at Caltech reflected these views. The strength of the crust was “enough to support [the] highest mountains,” he explained in class, but isostasy demonstrated that this strength “decreases downwards, and below 40 km or so plastic flow may occur.” This flow was implicated in both geological and seismological processes. Among the forces causing earthquakes, for example, Gutenberg suggested “elastic rebound as a release of shear due to sub-crustal flow and contraction of the crust & possibly differential movements in the crust from continental drift.” He noted that the energy release associated with earthquakes was “of the same order of magnitude as that due to temperature gradient,” which suggested that the most likely cause of plas tic flow was internal temperature differentials. One preexamination review sheet asked students for the meaning of isostasy and of “Wegener’s hypothesis.”
Soil Development in the Jornada Basin
Authors: Curtis Monger H.
Published: November 2020

Soils of the Jornada Basin are the substrate on which Jornada ecosystems reside and interact. Understanding soils and plant–soil feedback processes have been integral to understanding vegetation change and desertification (Buffington and Herbel 1965; Schlesinger et al. 1990). Formal studies of Jornada soils extend back to 1918. The most detailed study of Jornada soils is the USDA-SCS Desert Soil-Geomorphology Project (Gile et al. 1981), a 400-mi2 study area that includes the southernmost areas of the Jornada Experimental Range (JER) and Chihuahuan Desert Rangeland Research Center (CDRRC). This chapter highlights findings of soil and geomorphology studies, discusses factors and processes of soil development, and lists several ways soils of the Jornada Basin carry a memory of past climates. In addition to the Veatch (1918) study and the Desert Soil-Geomorphology Project, other investigations of soil types in the Jornada Basin include three soil surveys by the Soil Conservation Service: the first was of Jornada Experimental Range (SCS 1963), the second was of the White Sands Missile Range that includes the eastern Jornada Basin and San Andres Mountains (Neher and Bailey 1976), and the third was of Doña Ana County (Bulloch and Neher 1980). The 1918 investigation by J.O. Veatch of soils of the Jornada Basin was a reconnaissance study of the Jornada physical landscape. The purpose of the investigation was to make observations on the relation between soils and native vegetation and of the effect of overgrazing on different soil types. Veatch divided the study area into the higher mountain slopes, the foothills, and the Jornada Plain (as he described it, the plain included the currently recognized basin floor and piedmont slope). He recognized that the Jornada Plain was of Pleistocene age and contained extinct lakes with gypsum precipitated from desiccating water. He wrote that little change existed between the soil and subsoil, that “in reality a description of ‘soils’ here is but little more than a description of the various lithologic phases, appearing at the surface of a recent geologic formation.”
Water and Energy Balances within the Jornada Basin
Authors: Gutschick Vincent P. , Snyder Keirith A.
Published: November 2020

This chapter describes general characteristics and components of the energy and water balances in arid regions, with specific examples from the Jornada Basin. Various research efforts to characterize the energy and water balances and resultant carbon dioxide fluxes in the Jornada Basin are detailed. We provide a brief overview of how plant physiology interacts with energy and water balances in this region, and characterize general abiotic conditions and some physiological traits of plants in this arid region. The surface of a landscape may be considered as a layer with some amount of vegetation. More general descriptions divide the vegetation, like the soil, into layers, but the concern here is energy balance at the interface with the atmosphere. The net energy balance of the land surface is determined by inputs (radiant energy), outputs (reflection [i.e., albedo], emission of longwave radiation, convective heat transfer to the atmosphere [i.e., sensible heat flux], evapotranspiration of water [i.e., latent heat flux], and conduction of heat into soil), and changes in heat storage. The balance of these terms is adjusted as the surface temperature comes into steady state or nearly so. Increased solar input will drive surface temperatures higher until longwave emission and other losses come into a new balance. The net energy input, as inputs minus outputs, may be stated formally as an energy-balance equation . . . Rate of heat storage = S = Q+sw + Q+TIR − Q+TIR _ Q_E Q_H − Q_S, (8-1) . . . where the superscript + indicates an input, and − indicates an output or loss, and all terms are expressed as flux density in units of W/m2. Q+SW is the energy added to the surface layer by solar radiation from above. Q+TIR is the thermal infrared radiation emitted by gases in the atmosphere, principally water vapor and CO2, whereas Q_TIR is the thermal infrared radiation emitted from components of the Earth’s surface and lost back to the atmosphere. Q_E is the latent heat flux from the heat of vaporization of water vapors resulting from soil evaporation (E) and plant transpiration, generally measured as the composite evapotranspiration flux (ET).
Plant Communities in the Jornada Basin: The Dynamic Landscape
Authors: Peters Debra P. C. , Gibbens Robert P.
Published: November 2020

Plant communities of the Jornada Basin are characteristic of the northern Chihuahuan Desert both in structure and dynamics. Although a number of plant communities can be differentiated, five major vegetation types are often distinguished that differ in plant species cover and composition, as well as other factors, such as animal populations, soil properties, and elevation. These five types are black grama (Bouteloua eriopoda) grasslands, playa grasslands, tarbush (Flourensia cernua) shrublands, creosotebush (Larrea tridentata) shrublands, and mesquite (Prosopis grandulosa) shrublands. Similar to many other parts of the Chihuahuan Desert, these plant communities have experienced major shifts in vegetation composition over the past 50–150 years (York and Dick-Peddie 1969). The most dramatic changes in vegetation and associated ecosystem processes have occurred as a result of a shift in life form due to woody plant encroachment into perennial grasslands (Grover and Musick 1990; Bahre and Shelton 1993). This encroachment of shrubs has occurred in many arid and semiarid regions of the world, including the Western United States, northern Mexico, southern Africa, South America, New Zealand, and Australia (McPherson 1997; Scholes and Archer 1997). A number of drivers have been implicated in these grass–shrub dynamics, including various combinations of livestock grazing, small animal activity, drought, changes in fire regime, and changes in climate (Humphrey 1958; Archer 1989; Allred 1996; Reynolds et al. 1997; Van Auken 2000). The causes of shrub invasion are quite variable and often poorly understood, although the consequences consistently lead to the process of desertification (Schlesinger et al. 1990). This chapter describes the characteristics of each vegetation type and the documented changes in each type at the Jornada Basin. We then discuss the key drivers influencing these dynamics. Vegetation in the Chihuahuan Desert region has been classified as desert-grassland transition (Shreve 1917), desert savanna (Shantz and Zon 1924), desert plains grasslands (Clements 1920), desert shrub grassland (Darrow 1944), and shrubsteppe (Kuchler 1964). Desert grassland is often used as a general descriptive name for the area (McClaran 1995), although landscapes at the Jornada and throughout the northern Chihuahuan Desert often consist of a mosaic of desert grasslands, Chihuahuan Desert shrublands, and plains-mesa sand scrub (Dick-Peddie 1993).