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Life Science


Review Essays of Academic, Professional & Technical Books in the Humanities & Sciences



Fundamentals of Tree-Ring Research by James H. Speer (The University of Arizona Press)

Dendrochronology (tree-ring dating) is a method of scientific dating based on the analysis of tree-ring growth patterns. As James Speer notes in Fundamentals of Tree-Ring Research, trees are remarkable bioindicators. Although there are other scientific means of dating climatic and environmental events, dendrochronology provides the most reliable of all paleorecords. Trees record any environmental factor that directly or indirectly limits a process that affects the growth of ring structures from one season to the next, making them a useful monitor for a variety of events.
Fundamentals of Tree-Ring Research introduces the fundamental principles, concepts, and methods of dendrochronology and provides the basic instruction, theoretical framework, and biological and ecological background for the practitioner of tree-ring research. Speer compiles this knowledge into a user manual and reference book that covers the breadth of the field.

The book includes a history of the discipline, principles of the field, basic scientific information on the structure and growth of trees, the complete range of dendrochronology methods, and a description of each of the relevant subdisciplines. Individual chapters address the composition of wood, methods of field and laboratory study, dendroarchaeology, dendroclimatology, dendroecology, dendrogeomorphology, and dendrochemistry. Fundamentals of Tree-Ring Research also provides thorough introductions to common computer programs and methods of statistical analysis. In the final chapter, the author describes frontiers in dendrochronology, with an eye toward future directions in the field. Speer, associate professor of geography and geology at Indiana State University, the organizer of the Annual North American Dendroecological Fieldweek, and the current president of the Tree-Ring Society, concludes with several useful appendixes, including a listing of tree and shrub species that have been used successfully by dendrochronologists. Throughout, photographs and illustrations visually represent the state of knowledge in the field.

Dendrochronology is one of the most important environmental recording techniques for a variety of natural environmental processes and a monitor for human-caused changes to the environment such as pollution and contamination. Dendrochronology examines events through time that are recorded in the tree-ring structure or can be dated by tree rings. Because the tree becomes the instrument for environmental monitoring, it serves as a long-term bioindicator that extends for the lifetime of the tree. Dendrochronology can be applied to very old trees to provide long-term records of past temperature, rainfall, fire, insect outbreaks, landslides, hurricanes, and ice storms, to name only a few applications. Wood from dead trees can also be used to extend the chronology of tree rings further back in time.

According to Speer in the introduction to Fundamentals of Tree-Ring Research, the discipline of dendrochronology is used to mark time or record environmental variability in the structure of the wood from trees growing in seasonal climates, such as in the mid and high latitudes, and some tropical trees growing in environments with a pronounced wet or dry season. Because many environmental variables can affect tree growth, different records can be gained from a variety of tree species on a site and on a variety of sites in a region. Dendrochronologists have been able to develop interesting records that contribute to many areas of modern culture, from boundary disputes to forensic science. For example, Sellards et al. in 1923 used tree rings to settle a boundary dispute between the states of Oklahoma and Texas along the Red River. Tree rings have been used to help elucidate strange atmospheric events such as the Tunguska Event in Siberia, the largest impact event in the written history of the Earth, that occurred on June 30, 1908.

One of the most remarkable stories involves the Stradivari violin called the Messiah with a label date of 1716. This instrument would be valued between 10 and 20 million dollars if it could be authenticated as the true Messiah violin, but if it was made by a copyist in the 1800s, it would be worth far less. Dr. Henri Grissino-Mayer of the University of Tennessee pulled together a team of experts to examine the rings and demonstrated that the last rings in the instrument date to 1687, which is consistent with two other instruments made by Stradivari: the Archinto (dating to 1686) and the Kux/Castelbarco violas (dating to 1684).

Fundamentals of Tree-Ring Research presents a comprehensive history of dendrochronology that incorporates old world and new world pioneers. Chapter 3 contains a more complete history of dendrochronology that draws from European, American, Russian, and Asian dendrochronologists up to the 1950s. Speer provides a primer on the aspects of wood growth and structure that underlie the study of tree rings in chapter 4. The core of the book is the field and laboratory methods that are incorporated in chapters 5 and 6. He presents a basic gounding in field practices and provides some greater depth in working with the programs and statistics that are important to dendrochronology. Broad overviews and useful starting points for all of the major subfields in dendrochronology are given in chapters 7-11. Each chapter describes some specialized methods in each subfield, and the bibliography includes entries for the subfields as a starting point for research. Finally, chapter 12 describes what Speer sees as some frontiers in dendrochronology where researchers are gaining the most ground.

The breadth of this book surpasses any existing texts in the field. It is a very valuable resource because many researchers use tree rings to address a variety of answers rather than remaining exclusively within one subdiscipline. Carolyn A. Copenheaver, Virginia Polytechnic Institute and State University

Fundamentals of Tree-Ring Research is an easy to use primer and reference manual addressing all of the subjects that readers new to the field need to know. It is a welcome reference for practitioners and laypeople at all levels. No previous volume presents a comprehensive history of dendrochronology that incorporates old world and new world pioneers in dendrochronology. Speer cites most of the pertinent literature throughout the text and leads readers to useful internet resources in dendrochronology.

Litchi and Longan: Botany, Production and Uses edited by C. M. Menzel , G. K. Waite (CABI Publishing) Litchi (lychee) and the related fruit longan are grown extensively in China and South-East Asia, as well as in Australia, Florida (USA), Southern Europe and Southern Africa. This book represents the only comprehensive, balanced and internationally focused publication on these fruit. It covers all aspects of production, from taxonomy and breeding, to propagation, flowering and fruit set, to diseases, pests and postharvest storage and processing. Written by leading scientists from Australia, China, India, Israel, Thailand and the USA, the book represents the standard work on its subject. As the fruit are imported to many developed countries, the book will be of interest to a wide audience.

Litchi and longan are indigenous to South-east Asia and make significant contributions to the lives and economic health of millions of people in the region. These fruit originated in southern China and northern Viet Nam, but their culture has now spread to most countries that experience a subtropical climate for part of the year. Litchi is most important in China, India, Viet Nam and Thailand, while longan is produced mainly in China, Viet Nam and Thailand. There is also interest in these two fruit in southern Africa, Madagascar, Reunion, Israel, Spain, the USA, Mexico, Brazil, Australia, Bangladesh, Nepal, the Philippines and Indonesia. Production in the Asia-Pacific region accounts for more than 95% of world cultivation, at about 3 million tons, more than world avocado production but less than citrus, banana, pineapple, mango and papaya.

Most of the fruit is produced by small landholders, with fewer than 100 trees each. Orchards with more than 1000 trees are rare, except in southern China, where there are single plantings of more than 10,000 trees, and in southern Africa and Australia. The fruit have a high value, and can significantly add to the income of small landholders, with a few trees doubling the income of some families in Asia.

Despite the long history of litchi and longan cultivation, many areas experience low productivity, with average yields being less than 5 t/ha due to a number of factors such as warm weather at flower­ing, reliance on inappropriate cultivars or lack of tree care. In Israel and some other countries, yields of up to 15 t/ha have been achieved, indicating that there is a large gap between actual and potential yields. Prospects for increasing production and marketing of these crops are high if some of the grow­ing, postharvest handling and marketing issues are resolved. Inter- and intraregional cooperation in this area would assist the development and status of these crops in many local economies.

Litchi requires temperatures of around 15°C or lower to flower, with a period of dry weather sometimes being beneficial. Once trees have set fruit, warm weather and good soil moisture are asso­ciated with heavy yields. Cropping is thus limited to areas that experience some cool weather before flowering. Production in litchi is very erratic in the true tropics where nights seldom fall below 25°C, with the majority of the industries based in environments where nights fall below 15°C. However, there are examples of industries such as that in central Thailand, which is based on cultivars that can flower at temperatures slightly higher than those normally considered ideal. These areas often supply early season fruit and return higher incomes than fruit from `traditional' subtropical orchards, but can fail in some years. The quality of some of these cultivars is often inferior compared with the traditional types, indicating that new varieties that have better fruit quality need to be developed for these environments.

Longan has both subtropical and tropical ecotypes. The bulk of the crop in China and Thailand is still produced in cooler areas, whereas the main industry in Viet Nam is based in the Mekong Delta. More research is required to define the optimum temperatures for flowering in both species. There are also some growing techniques that can assist cropping in the warmer areas, but they have not been evaluated across many diverse environments. The other constraint related to climate is poor fruit set during cool, damp weather, and damage to trees and fruit after typhoons or hurricanes in China, Viet Nam, Madagascar, Mauritius, Australia, Hawaii and Florida.

Despite the long history of litchi and longan cultivation in Asia, there is a paucity of information concerning the yield of the major cultivars in different environments. The performance of some cultivars is disappointing, and production is unprofitable, with many industries based on only one or two cultivars. A lack of suitable cultivars limits production in many countries, because the existing varieties are low-yielding or are not well regarded in the market place.

Limited plant breeding and selection, facilitated by the exchange of germplasm, would increase the production of the crops. Some countries, such as India, China, Nepal and Viet Nam, have many seedling trees, which could form the basis of industry expansion. Breeding programmes are required in the long term to develop better cultivars, and this is best implemented with a regional focus. In the interim, the current gene pool should be more systematically evaluated. Standardization of cultivar names and descriptions would assist in this endeavour and encourage cooperation amongst producing countries. Based on the above, it can be concluded that there is a need for a much stronger varietal improvement programme.

Propagation is well described, most commercial orchards being planted with air-layers, with grafting and budding being popular in China and Viet Nam. It is reported that grafted trees are more drought- and wind-resistant, but little experimental evidence for this is available. Grafting also uses less planting material than air-layering. However, there are some disadvantages with grafting; it is not as easy to accomplish as air-layering, and requires the growing of seedling rootstocks. Grafted trees also take longer to develop to the stage where they can be planted out. There is little information on the graft compatibility between different cultivars, and the impact on production and fruit quality. Newly established young plants require regular watering, and many orchards in Asia experience serious losses at this stage due to a lack of irrigation facilities. The provision of irrigation, along with education of nursery workers and growers in tree care, would overcome this problem. It is apparent that further work is required in order to standardize nursery techniques.

Litchis and longans can be grown on a range of different soil types, including soils with a pH from 5 to 8. In very acid or alkaline soils, there can be problems with iron, zinc, boron and other nutrients. The soil must be freely draining, although the trees can tolerate a wet profile for part of the day. Tree health and production are best on sandy, sandy loam and clay loam soils, while heavy clay soils should be avoided.

Optimal production is achieved with irrigation, especially during the fruiting cycle, with rainfall varying from month to month across the different growing areas. Most of the orchards in Asia are not irrigated and are dependent on regular rainfall. Experiments in Australia and South Africa have shown that drought can reduce growth and fruit production, but the significance of this research for local producers in South-east Asia is not known. Most growers cannot afford the cost of irrigation and, in any case, irrigation is generally not available. Mulching and cover crops can assist water conservation in the absence of irrigation, although new orchards should be irrigated if possible.

Most growers apply fertilizers to their orchards. Tentative leaf and soil standards are available for both crops, but the tests are too expensive for small landholders. Local government extension staff could provide this service on a regional or district basis. Growers generally use a mixture of organic and chemical fertilizers, although the source of the fertilizer does not affect production. In contrast the effect on cropping of the timing of fertilizer application is yet to be resolved. Crop nutrient removal data should be used for estimating fertilizer requirements.

High-density orchards are becoming popular, and should increase returns to growers, especially in the early years of a planting. There is evidence that these orchards have double the returns of traditional low-density plantings. Considerable experience has been acquired in China, with closer plantings expected to increase returns for both small and large landholders.

High-density plantings require canopy management to control the size of trees, and close attention to water and nutrient management is also essential. Experiments in China and Australia have shown that the optimal time to prune trees is during the first few weeks following harvest, and this research needs to be repeated in the other growing areas. Extension staff also need training in the various aspects and benefits of canopy management. Drought, girdling, pruning and chemical defoliation can improve flowering, and need to be evaluated across different environments.

Many insects and other pests affect the trees, leaves, flowers and fruit, and their impact on grower returns varies from orchard to orchard. Each country's local industry needs to develop its own system of integrated pest management. Pest management approaches, along with other methods of tree care, must be suited to the needs and abilities of small landholders. Diseases do not generally affect litchi production, apart from downy blight and anthracnose in China, and pepper spot in Australia. The main disorder affecting longan is witches' broom, endemic to much of South-east Asia.

Litchi and longan fruit are highly perishable and have short shelf-lives, which seriously limits marketing and expansion of the crops. Attempts have been made to reduce postharvest fruit browning and rotting, by heating and cooling the fruit, the use of various packages and packing materials, and application of fungicides and other chemicals. However, the protocols established for the use of these cannot guarantee fruit quality for more than a week or two. Some export industries are based on the treatment of the fruit with sulphur, but this chemical may soon be withdrawn. The development of new postharvest treatments is thus more urgent.

Most of the litchis and longans produced in Asia are marketed locally, with some exports to Hong Kong, Malaysia and Singapore, and to a lesser degree Europe and the Arab States. There are also exports of litchis from southern Africa, Madagascar, and Australia to Europe. Most of the fruit is sold fresh, with one-third of the Chinese crop being dried, and some being processed and canned.

Quarantine issues relating to fruit flies cause problems for exports from Australia and South Africa to Japan and the USA. Disinfestation protocols need to be established for the various markets. The market potential within Asia is strong because of the rising affluence in many of those countries. Good-quality fruit from the region is also highly regarded in Europe, although very little market intelligence has been collected. The preferred cultivars, packaging, etc. for the different markets are not known. The potential size and value of each market is also unknown. Restricted freight space is a limiting factor for countries such as Australia, which are some distance from overseas markets. Quality standards are not used in all countries, despite their demonstrated benefits in several markets.

This publication presents the current state of knowledge concerning the history, physiology, culture, and marketing of litchi and longan throughout the world. Although it contains a wealth of documented information from the literature, and the extensive personal experience of the authors within their respective disciplines in association with the crops, it can be concluded that further research into all aspects of these two tropical fruit is required.

Cacti of the Trans-Pecos & Adjacent Areas by A. Michael Powell, James F. Weedin (Texas Tech University Press) A landmark guide, complete and definitive, Of the 132 species and varieties of cacti in Texas, about 104 of them occur in the fifteen counties of the Trans-Pecos region. This volume includes full descriptions of those many genera, species, and varieties of cacti, with sixty-four maps showing the distribution of each species in the region.

The descriptions follow the latest findings of cactus researchers worldwide and include scientific names; common names; identifying characters based on vegetative habit, flowers, fruit, and seeds; identification of flowerless specimens; and phenology and biosystematics.

The introduction—full of details about the biology and morphology of the family Cactaceae, the uses of cacti, and the horticulture and conservation of cacti—is an important reference for general readers. More than three hundred beautiful full-color photographs of the cacti in flower and in fruit, all cross-referenced to their description in the text, highlight the book.

A glossary of cactus terms, an exhaustive list of literature, and a thorough index complete the book.

Excerpt: The Chihuahuan Desert Region holds more species of cacti than any other comparable area in North America. This center of cactus diversity lies mostly in northern Mexico; it extends into the United States only in the Trans-Pecos region of Texas and some adjacent parcels in New Mex­ico and Arizona. This area west of the Pecos River involves about 3,000 square miles, or 20.5 million acres, equivalent in size to the state of Maine. The Trans-Pecos shares some species and vegetation types with the Edwards Plateau ("Hill Country") of Central Texas, the Tamaulipan thorn-scrub of the Rio Grande valley, the Great Plains of the Texas Panhandle and eastern New Mexico, and the Apachean floristic region of southeastern Arizona. However, by far the greatest part of the Trans-Pecos vegetation and flora pertains to the Chihuahuan Desert. Consequently, the Trans-Pecos is one of the major centers of cactus distribution in the United States.

In Trans-Pecos Texas, the southern Big Bend area is best known as cactus country. The lowest elevation in the entire Chihuahuan Desert Region lies in the Boquillas Basin near the Rio Grande, just downslope from the southeastern foothills of the Chisos Mountains. Endemic taxa and subfossil remains of desert plants indicate that the Boquillas Basin served as a major biological refugium during the last Ice Age and thus must have been one of the major dispersal cen­ters for Chihuahuan Desert species.

The present work is the first that emphasizes the cacti of Trans-Pecos Texas. Several publications with wider geographic coverage that have included the Trans-Pecos cactus flora are cited in the Introduction. Most of the sources are out of print. The cactus books most widely used to identify Texas cacti were those by Del Weniger and Lyman Benson. The extensive nomenclatural differences between the Weniger and Benson publications were disconcerting to many who wanted to use the scientific names of southwestern cacti. One objective of our cactus treatment was to reconcile the differences between Weniger and Benson, where possible, and to provide alternative nomenclature that reflects contempo­rary taxonomic research.

Two advantages of regional treatments such as Cacti of the Trans-Pecos and Adjacent Areas are that more detailed information can be included about the biology of cacti in general and about each species and identification is simpler without the need to "wade through" extraneous species. One of our objectives in preparing the current Cacti was to allow preliminary identification by matching unidentified cacti with color photographs of plants in flower and in fruit. Distrib­ution maps, keys, and descriptions provide a second level of information for sys­tematic identification that supersedes the first impression gained from the pic­tures. In addition to the means for field, greenhouse, herbarium, and laboratory identifications, Cacti includes explanatory sections on morphology and anatomy, physiology, secondary compound chemistry, ecology and biogeography, chromosome numbers, evolution, pollination biology, uses and other ethnobotany, horti­culture, conservation, diagnostic vegetative and floral characters, floral and fruit phenology, technical features of sterile specimens that allow identification of dried specimens and fragments, and anything else of potential relevance for con­fidence in identification of populations or individual species. For each species we include basionym citation, nomenclatural synonyms, common names that have come to our attention, and a translation of the Latinized international name.

Cacti of the Trans-Pecos and Adjacent Areas should allow confident identifi­cation of cacti throughout Texas, excepting varieties of Echinocereus reichen­bachii and several eastern species of prickly pears. We have prepared full treat­ments for all cactus taxa known to occur in the Trans-Pecos except for certain chromosome races of Opuntia leptocaulis and certain prickly pears recognized by David Ferguson. There is at least brief mention of essentially all Texas taxa of Cactaceae. The Cis-Pecos Texas cactus species are not keyed but are diagnosed either in the context of discussing Trans-Pecos cactus species or in abridged treat­ments inserted as appendixes at the ends of genera sections. Photographs repre­senting most of these taxa are included, except for the opuntias. In treating the relatively large and taxonomically complex genus Opuntia, we at least mention all of the Cis-Pecos species recognized in standard reference works such as Benson (1969b, 1982) and Britton and Rose ([1937] 1963).

The book was designed for use by dedicated nonprofessionals, self-taught hobbyists and naturalists, and serious students of cacti. Visitors to the national parks, state parks, and other natural areas in regions adjacent to the Trans-Pecos will use the book. The manual will be important to professionals in national and state park resource interpretation, wildlife biology, ecology, range management, and environmental consulting.

Many aspects of format follow the companion books Trees and Shrubs of the Trans-Pecos and Adjacent Areas (Powell, 1998a) and Grasses of the Trans-Pecos and Adjacent Areas (Powell, 2000). Metric system measurements are used in keys, descriptions, and discussions about the species. The English system is used for elevations and distances. Abbreviations for states are two letters in caps, following the U.S. Postal Service and current trends in scientific writing. Directions are in caps (e.g., N, E, S, W, or NW). Only one direction, NE, has the same abbreviation as a state, Nebraska. Author citations for plant names mostly follow those in the Missouri Botanical Garden, TROPICOS, and in Brummitt and Powell (1992).

Most of the morphological data were taken from specimens housed in the Sul Ross State University (SRSC) herbarium and from living specimens at Sul Ross. Some measurements also were taken from pertinent literature.

The generalized distribution maps reflect our current information about the ranges of relevant taxa in North America. Although we prefer to use geographi­cally explicit dot maps for indicating taxon distribution, in this case we elected to use a more generalized mapping approach for several reasons. Dot maps are most effective when localities documented by herbarium specimens are numer­ous, showing patterns that reflect actual distributions. Relatively few herbarium specimens are available for many of the cacti. To fashion the range maps, we have used a combination of documented localities, remembered localities from our collective field experiences, and our understanding (sometimes insufficient) of the habitat requirements of each species. Distributional information recorded in various published sources has been incorporated or not, on a species-by­species basis, because mistakes are rampant in the literature. The generalized dis­tributions portrayed in the present work are most accurate when dealing with taxa of restricted ranges. The mapped distributions are less precise when portray­ing wider-ranging taxa. The astute observer will notice where certain localized landforms (marginally conspicuous at this map scale, in most cases) have been ignored because they are predictably islands of unsuitable habitat (e.g., moun­tains within the ranges of the deep-soil low plains cacti). The high Chisos Moun­tains are among the smallest such habitat islands mapped as holes in species ranges at this scale.

The small inset maps show approximate ranges of widely distributed taxa. Spots on the inset map denote regional occurrence of species outside the Trans-Pecos and not necessarily specifically documented localities. Taxa with limited ranges outside the Trans-Pecos (only one spot, at this scale) are the minority, because most of the species included in the present work extend into two or more other states of the United States and/or Mexico. Distributional information for each taxon is summarized verbally in the text.

The term "cultivated" in figure legends denotes photography of specimens grown in containers, in the experimental Opuntia garden, or in the formal Cac­tus Garden at Sul Ross State University. The photographs were taken by the first author, except for those otherwise specifically acknowledged.

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