Cover of Trees and Forests of Tropical Asia
Trees and Forests of Tropical Asia Exploring Tapovan
by Peter Ashton and David Lee
University of Chicago Press, 2022
Cloth: 978-0-226-53555-5 | Paper: 978-0-226-53569-2 | Electronic: 978-0-226-53572-2
DOI: 10.7208/chicago/9780226535722.001.0001

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ABOUT THIS BOOKAUTHOR BIOGRAPHYREVIEWSTABLE OF CONTENTS

ABOUT THIS BOOK

Informed by decades of researching tropical Asian forests, a comprehensive, up-to-date, and beautifully illustrated synthesis of the natural history of this unique place.
 
Trees and Forests of Tropical Asia invites readers on an expedition into the leafy, humid, forested landscapes of tropical Asia—the so-called tapovan, a Sanskrit word for the forest where knowledge is attained through tapasya, or inner struggle. Peter Ashton and David Lee, two of the world’s leading scholars on Asian tropical rain forests, reveal the geology and climate that have produced these unique forests, the diversity of species that inhabit them, the means by which rain forest tree species evolve to achieve unique ecological space, and the role of humans in modifying the landscapes over centuries. Following Peter Ashton’s extensive On the Forests of Tropical Asia, the first book to describe the forests of the entire tropical Asian region from India east to New Guinea, this new book provides a more condensed and updated overview of tropical Asian forests written accessibly for students as well as tropical forest biologists, ecologists, and conservation biologists.

AUTHOR BIOGRAPHY

Peter Ashton is professor emeritus in the Department of Organismic and Evolutionary Biology at Harvard University, where he served as director of the Arnold Arboretum. He is also an honorary research associate at the Royal Botanic Gardens, Kew. He is the author, most recently, of On the Forests of Tropical Asia: Lest the Memory Fade. For over fifty years, David Lee has researched leaves, first in the Asian tropics and later at Florida International University, where he taught for thirty years and is professor emeritus in the Department of Biological Sciences. He is the author of many articles and several books, including Nature’s Palette and Nature’s Fabric, both also published by the University of Chicago Press.

REVIEWS

“This profoundly inspirational book, a personal—almost autobiographical—deep-dive into the ecology, evolution, biogeography, and conservation of the forests of tropical Asia, is a lyrically written, instant classic, a page-turner natural history saga in the mold of a modern-day Alfred Russel Wallace.”
— Stephen P. Hubbell

“A fascinating, unique contribution to a scarce literature, and a book that perhaps could only have been written by these two authors. Ashton and Lee’s stories will inspire others to build a knowledgebase that the rich biodiversity of tropical Asian forests warrants, and that society seeks.”
— Kamal Bawa, University of Massachusetts, Boston, and ATREE, Bengaluru

“A major scientific treatise that will be an essential reference for those who study tropical forests.”
— Plant Science Bulletin, on "On the Forests of Tropical Asia"

“A monumental work. . . . For any tropical biologist on any continent, the book will provide an invaluable reference, a fascinating history, and a wellspring for novel ideas.”
— Biotropica, on "On the Forests of Tropical Asia"

“A masterpiece of scientific scholarship in an area that is of tremendous importance for the biosphere.”
— Biologist, on "On the Forests of Tropical Asia"

TABLE OF CONTENTS


DOI: 10.7208/chicago/9780226535722.003.0001
[Hadley Cell;El Niño Southern Oscillation;limits of tropics;killing frosts;species diversity;irradiance]
Tropical regions establish at low latitudes with greater solar irradiance and an absence of rare killing frosts, and they are directly influenced by Hadley circulation cells. The Asian tropics are distinctive for their long longitudinal spread and higher latitude excursions. The former results from a complex geological history resulting in physical isolation, and the latter results from the formation of high mountain ranges (principally the Himalayas) protecting areas to the south from winter weather.Equatorial daily weather, seasonality, andEl Nino Southern Oscillation events are also particularly important in Asia.Total species diversity in the Asian tropics may be higher on an area basis than other regions, and the chapter discusses how this diversity can be assessed.


DOI: 10.7208/chicago/9780226535722.003.0002
[forest types;climate;everwet;seasonal;mixed dipterocarp forests;kerangas]
This chapter is a summary of the major forest types in the Asian tropics.It describes each type and the major climate and geological factors that have helped to produce them.It also offersa concise and photographically enriched documentofeach forest, summarizes them collectively with a table, and describes their distribution throughout the region with a map.It stresses the primary importance of climate, as the seasonality and amount of precipitation are the primary determinants of the major forest types, starting with unseasonal and wet forests, known as mixed dipterocarp forests (MDF) in Asia. It continues, with increasing seasonality through various seasonal evergreen, seasonal deciduous forests to thorn woodlands.Soils and nutrients influence the formation of other forests, particularly ultramafic and kerangas.


DOI: 10.7208/chicago/9780226535722.003.0003
[plate tectonics;terranes;Gondwana;Laurasia;volcanism;Pangaea;landscape natural history]
The complex patterns of distributions of forest types in tropical Asia are very much due to the tumultuous geological history in the region, particularly during the past 200 million years.Plate tectonics moved large masses of landforms from the unitary continent of Pangaea as terranes becamepart of landforms of the original Asian continent. The most influential event was the movement of the Indian subcontinent north into Asia, arriving some 55 million years ago. These plate movements had secondary effects, producing zones of volcanic activity, regions of limestone in shallow seas, and regions with abrupt shifts in geology and soil formation.


DOI: 10.7208/chicago/9780226535722.003.0004
[seasonal tropics;monsoon;Pleistocene;sea levels;sundaland;climate]
Regional climates in Asia have profoundly influenced the distributions of forest types in the region, historically influenced by geological processes.Landforms, in relation to adjacent seas and latitude, have been influenced by different patterns of rainfall, with dry months (less than 100 mm of precipitation).There are four distinct climatic patterns: the aseasonal tropics with no dry months and stretching from Sumatra to the Pacific, and seasonal climates: one with summer rains (the southwest monsoon), one with winter rains (the northeast winter “monsoon”) and a few areas where both are present.Regions with seasonal climates are often affected by cyclonic storms and fire.Geology has influenced the changes in climates over time, thus influencing the presence of forest types.Global changes in temperature have affected sea levels, particularly in the emergence and submergence of land in the South China Sea, or Sundaland, during the Pleistocene.


DOI: 10.7208/chicago/9780226535722.003.0005
[weathering;udult;humult;litter decomposition;nutrients;leaching]
Climate and geology both influence the processes of soil formation or weathering.Soils are critical to understanding the distribution of forests in the Asian tropics, on local to regional scales.Biological activity is important in soil formation, particularly ants and termites, also microbes. Increasingly we are learning the importance of mycorrhizae in soils.Organic material and its distribution are thus of critical importance in the classification and function of soils.Soils that distribute organic materials throughout the horizon are udult, and soils that accumulate an organic layer at the surface are humult. The latter soils are on mountains where cooler temperatures reduce the rate of litter decomposition. Soil quality and accumulation often vary on very local scales, often depending on geology, and influence types of forests or tree distributions.


DOI: 10.7208/chicago/9780226535722.003.0006
[plant functional types;Christian Raunkiaer;trees;dipterocarps;photosynthesis;architecture;longevity;phenology;growth]
The different plants characterizing a tropical forest are today classified as groups, or functional types.One classification, based on leaf size is that of Raunkiaer, used frequently in the book.Functional types help distinguish a forest anywhere, including the tropics, but there are differences (taxonomic groups and importance) among forests in Asia, Africa and the neotropics.Trees are stressed in this chapter, and functional types can be distinguished by their physiology (particularly photosynthesis and respiration), growth, architecture, shade tolerance, size, longevity, phenology, reproduction, and other characters.In addition, understory plants, palms, epiphytes, lianas, also vary among forests types and regions.The roles of these plants will be stressed in later chapters.


DOI: 10.7208/chicago/9780226535722.003.0007
[mixed dipterocarp forests;stratification;architecture;disturbance;gap phase dynamics;emergent;pioneer;equilibrium]
Lowland everwet forests, or mixed dipterocarp forests, are the most majestic, establishing on sites where moisture is always available.Such forests have a highly stratified structure, normally including emergents above the canopy and lower layers.Maximum height, branching and crown architecture, and reproduction (mast flowering and fruiting prevails) may factor in determining the layers in the forest.If the forest structure is damaged (by death, disease or storm damage), gaps are formed and an ecological process of recovery, succession or gap phase dynamics, follows.Successional species (pioneers) are different in physiology and function than mature (climax) species. These forests vary in structural and physiognomic detail when established in different rock substrates, soils and slopes. These forests are in dynamic equilibrium, rarely reaching a climax.


DOI: 10.7208/chicago/9780226535722.003.0008
[deciduous forests;bamboo;reproduction;fire;grazing]
Seasonal forests establish under conditions of at least 1 dry month.In the latter condition, the forests are evergreen but lack emergent crowns, with a lower stature than everwet forests. The reproduction in all of these forests is annual.Fire is an important ecological factor in seasonal forests.Increasing aridity (more dry months) promotes a series of forest types, from semievergreen, to tall and short deciduous forests, to notophyll forests and thorn woodland.Bamboos and fire are important in their ecology.Fire, then grass, then grazing by ungulates (especially cattle) are widespread in these forests.Fires vary from confinement to the ground layer and lower temperatures, to those that reach the canopy, produce higher temperatures and more extensive ecological effects (hot fires).Human-caused fires have increased in the past century, making the management of such forests more challenging.


DOI: 10.7208/chicago/9780226535722.003.0009
[MDF;peat swamp;kerangas;soil;topography;diversity;nutrients;precipitation]
Tree species diversity and composition in lowland forests is influenced by several factors.Generally total diversity and importance of certain species is affected by reductions in rainfall, from MDF to deciduous forests (with few dipterocarps in the latter).Species composition, and therefore floristic communities, among these forest types is influenced by geology, soils, topography, and water stress.Water stress reduces canopy height in all forests, and low nutrient status may promote the establishment of peat swamp forests and kerangas, and other forests on limestone and ultrabasic minerals.Collectively, these variables influence the structure and diversity of MDF throughout the everwet regions, producing different forest associations.The transition from evergreen to deciduous forests reduces the importance of dipterocarps (except for Sal in India) and their replacement by other families, including Lamiaceae (teak), Lythraceae (Lagerstroemia) and Combretaceae (Terminalia).


DOI: 10.7208/chicago/9780226535722.003.0010
[lower montane forest;upper montane forest;Mount Kinabalu;conifers;moss forest;frost;tree line]
Increasing elevation (and lower mean temperature) changes forest structure and composition.Dipterocarps become less important with elevation, true lower montane forests establish (at around 1,000 m), then upper montane forests, then subalpine thickets.Stature decreases, species composition changes, and species diversity generally decreases.With cloud penetration in upper montane forests, a distinct mossy forest establishes.Mount Kinabalu in northern Borneo is the best documented location for these altitudinal changes.In Bhutan and northeast India, the increase in elevation establishes lower montane forest above deciduous forest, and at higher elevations a change to warm temperate mostly evergreen forests.Frost is an important factor in the vegetation distribution in the montane tropics, low temperature ponding affecting lower elevations and ground frost at very high elevations. Conifers are more important on mountains than in the lowlands.Low temperatures (and the balance between respiration and photosynthesis) may limit the growth of trees at only the highest elevations.


DOI: 10.7208/chicago/9780226535722.003.0011
[pollination;outcrossing;mass flowering;phenology;genetic diversity]
Pollination is important in the tropics, as elsewhere, by promoting outcrossing, maintaining genetic diversity, and promoting evolution.Few species use wind or water for pollination, almost all use animals, mostly insects but occasionally animals (particularly bats). Flower structures promote a variety of breeding mechanisms, as unisexual flowers promoting dioecy and outcrossing.Mass flowering and fruiting is prevalent in MDF, especially among the dipterocarps, flowering every few years, many of whom share the same pollinator and shift their flowering phenology. Bamboos flower en masse at very long intervals.In deciduous forests the flowering is annual, with fruits generally ripening before the monsoon rains.


DOI: 10.7208/chicago/9780226535722.003.0012
[seeds;dispersal;outcrossing;seed shadows;density dependence;neutral theory;pathogens;mycorrhizae]
Seed dispersal as another mechanism, complementary to pollination, in promoting outcrossing and genetic diversity, and ultimately fitness. In closed forests, wind or water are relatively unimportant in dispersal. Animals are important dispersal agents in tropical Asian forests. Seed shadows, promoting species diversity in small areas, may occur near trees because of density-dependent mortality, as by pathogens.Species distributions in these forests may be due to random factors in dispersal and survival, Hubbell’s neutral theory.Most animals in these forests are seed dispersers, particularly good examples being the primates.On the other hand, other mobile links may harm forest trees, as pathogens, affecting diversity patterns.Mycorrhizae may affect seedling survival and growth (and distribution) in a complex manner. Dispersal influences genetic and species diversity.


DOI: 10.7208/chicago/9780226535722.003.0013
[phylogeography;Gondwana;India;Laurasia;barriers;speciation;Sundaland;endemism]
The present diversity of species within tropical forests is the result of a long history, of geological episodes and shifts in climates. The method for tracing histories of plant evolution combines systematics (particularly molecular), fossil history and geography: phylogeography.Movement of precursor species into tropical Asia occurred by four pathways: pan-tropical connections, Gondwanan elements via India, eastern Laurasia, and Australasia. These arrivals further evolved via speciation in the Asian tropics, but their movements were affected by barriers.The most important were Wallace’s line, separating eastern and western tropical Asia; Chatterjee’s partition, separating India and Indochina, the Kangar-Pattani line, dividing Thailand and Malaya; and high sea levels across the Sunda shelf, affecting Borneo and Malaya.High diversity areas established, the most notable which is the Riau Pocket. These often corresponded with high levels of endemicity, particularly on mountains.


DOI: 10.7208/chicago/9780226535722.003.0014
[Stephen Hubbell;neutral theory;intermediate disturbance;diversity;latitude;precipitation;speciation;ForestGEO]
This chapter addresses the challenge of understanding the high species diversity within individual forests.Forests in seasonal climates are reduced in diversity, and most discussion concerns the highest diversity forests in the wet tropics.Various hypotheses have been proposed as explanations. Stephen Hubbell’s neutral theory postulated random factors of dispersal to explain these levels of diversity. Diversity is increased by higher precipitation, and it may also be greater on older sites.Heterogeneity at individual sites, in topography (and moisture availability) and soils (and nutrient supplies) also clearly influence diversity within the greater forest.Differences in canopy structure, forest dynamics (intermediate disturbance), latitude, nutrients (David Tillman) all affect diversity. Forests also vary in rank orders of species abundance, and some are dominated by a single species. Such differences are inconsistent with the neutral theory. The establishment of the ForestGEO plots and the tools for their comparison is advancing the study of forest diversity, still one of the great challenges in ecological research.


DOI: 10.7208/chicago/9780226535722.003.0015
[hominids;culture;swidden;non-timber forest products;irrigation;rice;civilization;trade]
Hominids have lived in the Asian tropics for 2 million years, and modern humans for 50,000 years.They have had almost no effect on the everwet forests during that time, and some influence on forest in the seasonal tropics.A diversity of languages and culture arose among separate people in the region, attuned to the environments where they lived.In addition to hunting and gathering, many groups established systems of cultivation involving cutting and burning forests in small areas, cultivating, and then allowing the forest to recover: Swidden or shifting cultivation. Their spiritual beliefs resulted in the preservation of certain forests.Where resources permitted, regional civilizations were established, trading with India and China.These civilizations developed technologies of irrigation and rice cultivation; India had the most cultural influence on the region.A common tradition of land use occurred, with towns, local rulers, and trade established along the coasts, and less populated and forest-based people on the interior uplands. They collected valuable non-timber forest products (spices and perfume oils, mainly) and sold them to the lowland people, who traded with foreigners.Those products found their way into China, India, the Middle East and Europe for at least 3,000 years.


DOI: 10.7208/chicago/9780226535722.003.0016
[colonialism;commodities;tea;coffee;rubber;community forestry;Dietrich Brandis;selective management;independence]
Motivated by the desire to control trade in valuable spices, perfume oils and other goods from the Asian tropics, European nations explored, gained trading footholds, and then colonized tropical Asia: England in India, Malaysia and Java; Spain in the Philippines, Portugal for a while in India and further east, Holland in Malaya and Indonesia, and France in India and Indochina.They turned their attention to forests, converting some for establishing commodity plantations, especially coffee and tea, and much later in rubber and oil palm. Generally, the colonial powers struggled with ownership issues, affecting their exploitation of forests.Only the English made serious attempts to exploit and then manage forests, especially after the depletion of many forest resources. Dietrich Brandis was appointed as the first Inspector-General of the Indian Forest Department.That ultimately led to the first management systems in the tropics, for teak in India and Burma, and later selective management systems for mixed dipterocarp forest in Malaya and Borneo. There were even early efforts in community forestry. In the 20thcentury, English foresters developed the Malayan Uniform System, the first management system for those forests. However, changing markets, the Second World War, and then independence, prevented its widespread application.


DOI: 10.7208/chicago/9780226535722.003.0017
[independence;deforestation;economics;population;mercantilism;oil palm;transmigration;watersheds;non-timber forest products]
The multiple benefits of forests, biodiversity conservation, watershed protection, non-timber forest products, homes and livelihoods of forest people, are lost with deforestation. After the end of World War II, the present countries of tropical Asia gained their independence from their European overlords, sometimes by acquiescence and sometimes by protracted and violent struggle. Only Thailand and Bhutan had kept their independence as royal kingdoms.Independence released the country-level changes that led to widespread forest exploitation (sources of jobs and revenues for newly established economies and governments) and, ultimately, deforestation. From independence to present day, population has quadrupled, and the region is largely deforested, except New Guinea.Existing forests are limited to preserves (national parks) and on the steepest slopes and mountains.Early advances in sylvicultural management systems were largely abandoned.Several developments fostered the rapid deforestation:availability of technology, partly military in origin; the rise of mercantilism in recently established countries, with foreign involvement; the expansion of commodity plantations, particularly the dramatic rise of oil palm; transmigration schemes, movement of people from densely to sparsely settled regions (i.e. forests); and in the seasonal tropics, the direct pressure of rapidly growing human populations.


DOI: 10.7208/chicago/9780226535722.003.0018
[water;climate;weather;biodiversity;economics;sylviculture;ecotourism]
The forest resources of tropical Asia have almost vanished.What might be done to preserve the remaining forests and re-establish additional productive forests?The first task is to convince policy makers of the value of forests, not just as an economic resource (i. e. timber and other products), but also the ancillary benefits of forests.Sylvicultural management should maintain this value, part of healthy and productive economies, into the future.Climate change will make the conservation of existing forests more difficult, and the loss of forest biomass and carbon (particularly in peat swamps) adds to the problem.Temperature increase will affect the water balances of forests.Sea level rise will remove low-lying lands, often densely populated. Those people will move to uplands, already densely inhabited. Weather will become more erratic, causing catastrophic events:drought, hurricanes, floods, and fires.Reversing these trends will require changing attitudes in local populations and gaining financial resources from the more developed world outside of the tropics.Ecotourism may help; it provides income for local people, valuing remaining forests. Public interest worldwide has been attracted to the wonder of tropical forests and wildlife, promoting international support for forest preservation.

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