The tropical rain forest

Tropical rain forest is one of the major vegetation types of the globe (Richards 1996; Whitmore 1998). It is an essentially equatorial and strongly hygrophilous biome as its name suggests and is found on all the continents that the tropics touch. Tropical rain forest is defined physiognomically with typical features being a closed, evergreen canopy of 25m or more in height dominated by mesophyll-sized leaves, with an abundance of thick-stemmed woody climbers and both herbaceous and woody epiphytes. Altitude has a marked effect on forest physiognomy above about 1500m, and montane facies have to be distinguished. The so-called tropical diurnal climate has a temperature regime in which the major periodicity is the daily march from night-time lows to afternoon highs. The fluctuation through the year in mean monthly temperatures is usually of smaller magnitude than the typical daily temperature range. Temperatures usually average at around 27°C at lowland weather stations in tropical rain-forest regions, and minima rarely, if ever, enter the chilling range below 10°C. Rainfall is generally at least 2000mm per annum, and a month with less than 100mm is considered dry. Rain forests can withstand dry periods though prolonged, or particularly severe, droughts on a regular basis usually lead to drought-deciduous forest replacing the true rain forest. Many rain forests do persist despite annual dry seasons, though only if the trees have access to ground water in areas experiencing long periods without rain.

Reproduction

The high species diversity of the tropical rain forest is inevitably associated with low population densities for a majority of species. Most tree species will exist at densities below ten mature individuals per hectare of forest, and many will live in much sparser populations. Tropical ecologists have long been intrigued by the possible ability of tropical tree populations of widely separated individuals to outbreed successfully. In recent years, new techniques for genetically fingerprinting individuals have provided strong evidence that many tropical tree species are strongly outbreeding despite large average distances between trees within a population.

Vegetative reproduction

There have been relatively few studies of vegetative reproduction in tropical trees. However, a number of reports refer to the marked ability of some understorey species to root from plant fragments including stems and leaves (Gartner 1989; Kinsman 1990; Sagers 1993). Shrubs, such as species of Psychotria and Piper, may need to be resilient to damage as they stand a relatively high chance of being broken by falling tree parts or large animals. An ability to re-sprout and produce adventitious roots will allow broken fragments to establish as new plants. Even the large-tree species, Tetramerista glabra, from the peat swamp forests of Borneo has been reported to employ this method of propagation (Gavin & Peart 1997, 1999). Many Tetramerista ‘seedlings’ are actually sprouts from fallen branches or collapsed saplings.

A wide range of tropical trees are typically multi-stemmed.

Age, size and growth in tropical rain-forest trees

The growth rates of tropical trees are usually estimated by repeat measurements of dimensions, most often that of stem girth or diameter. If tropical trees could be aged easily and accurately then estimates of average growth rates would be possible from one-off measurements. The age of trees in the temperate zone can generally be estimated precisely from counting annual rings on cores taken from the trunk base. Tree rings are caused by periodic variation in the nature of the wood laid down at the cambium. Wood growth is often so uniform in tropical trees that rings are undetectable. Where they are present they may represent checks on normal growth that occurred at irregular intervals. However, there are certain tropical regions where dry seasons, or very wet ones with flooding, are strong enough annual signals to produce yearly rings (Martínez-Ramos & Alvarez-Buylla 1998).

Most tropical lowland forest trees do not have annual rings. Old trees can be aged by using 14C-dating techniques on wood samples from the heart of the trunk base. This method has recently been applied with some startling results on large trees from the Amazon basin (Chambers et al. 1998). Twenty large trees from near Manaus, Brazil, were found to have ages (± 80 years) of 200–1400 years. The oldest was an individual of Cariniana micrantha. There was a poor correlation between size and age, even within a species.

Introduction

The Madonie Park, covering 40 000 hectares, is one of the most interesting and floristically differentiated areas in the Mediterranean basin. Its territory shows a very high degree of diversity as instanced by about 1600 taxa of the vascular flora with a high percentage of endemic species. The forest vegetation, in the Mediterranean to subatlantic belt, is varied and mainly characterised by evergreen oak (both Quercus ilex and Q. suber) and deciduous woods with Quercus pubescens, Q. virgiliana, Castanea sativa, Q. petraea and Fagus sylvatica. Exotic trees are widespread in all the Madonie mountains, including Pinus halepensis, P. pinea, P. nigra, Cedrus atlantica, C. deodara, Cupressus sempervirens, C. arizonica, C. macrocarpa, Abies alba, A. cephalonica, Robinia pseudoacacia and Eucalyptus camaldulensis. The landscape is also composed of rocky environments, grasslands and wetland sites. All these environments are also very rich in cryptogams (lower plants) but knowledge about them is still inadequate.

As regards fungi, it is noteworthy that since the second half of the seventeenth century the local population has exploited the understorey products as a source of food or for income. In the last decade mushroom picking, previously limited to relatively few people, has become a widespread pastime with potentially adverse consequences to mycelium growth and fruit body appearance. This threat, together with the lack of knowledge of Sicilian fungi, causes serious problems for any attempt to safeguard the integrity of the ecosystem. In addition, the concern for fungi by local authorities and the scientific community is still very slight.

The reception of this book since its original publication some 15 years ago, and the frequent questions put to the author over the past decade about a revised edition, suggest that it has found a place amongst the tools of working botanists as well as of reference librarians. I hope this revision will find a similar reception, in spite of – inevitably – an increase in bulk.

In the nearly 20 years since coverage was closed for the original edition, floras and related works have continued by and large to gush forth. The need for them remains, although it may be driven more by practical than by academic considerations. The renewal and increasing prominence of the environmental and conservation movements, the associated promulgation of international treaties such as the Convention on International Trade in Endangered Species (CITES) and the Convention on Biological Diversity (CBD), and the consequent requirement to have a better understanding of national biotas have moreover created new ‘markets’ for floristic information. This is all in addition to natural cycles of renewal as scientific knowledge expands and deepens, best expressed in more developed countries. Altogether, many more new floras and enumerations have been published than superseded, improving coverage for many parts of the world – sometimes well beyond what was the case in 1979 (Map I). They retain an important place within the botanical literary warrant, and continue to be one of the most important points of contact between user and producer.

Introduction

Many regions of the dunes along the coast of The Netherlands are now in use as part of the drinking water supply chain and are therefore well protected. The Amsterdam Waterworks Dunes, situated south and west of Haarlem, deliver drinking water to the city of Amsterdam. The site is owned and managed by the municipality of Amsterdam. In this dune field of 34 km2 the mycota of two, locally decalcified, natural grasslands has been studied since 1986 (Becker & Baeyens, 1992; Nauta & Jalink, 1996). The management consists of summer grazing by cattle in one site (Eiland van Rolvers), and yearly mowing and removal of the hay in the other (Groot Zwarteveld).

History

The area of the Amsterdam Waterworks Dunes consists mainly of young dunes, formed during several periods of blowing sand from the eleventh century onwards. The soils differ in calcium content, depending on the period in which they were formed, and this can often be seen from the vegetation. For instance, the Hippophae rhamnoides scrub, developed in the central part of the Amsterdam Waterworks Dunes from around 1500–1600 onwards, has usually developed on more or less calcareous soil. From early days humans have used the dunes. There is evidence that from 1500 onwards, wet dune slacks have been grazed in summer by cattle and sheep.

In the early nineteenth century the dune area also became popular for growing potatoes.

Introduction

In countries that made up the former Soviet Union, however much one wants to concentrate on fungal conservation, general infrastructure problems demand attention. Until they have been addressed, little conservation of anything can take place. Ukraine is no exception. A number of agencies are committed to eliminating poverty and sustaining development in the transition countries in Central and Eastern Europe; the Department for International Development (DFID) is the British government department responsible for this. DFID has published a concise assessment of Ukraine's political, economic and environmental background which can be found in the UK Government's 1998 country strategy paper for Ukraine at the web site <http://www.dfid.gov.uk/public/what/pdf/ukraine_csp.pdf>, with the UK Government's environmental strategy for Ukraine being on <http://bc.kiev.ua/english/work/envstr.pdf>. The realities described in these two straight-talking documents make one admire all the more the dedication of those Ukrainian mycologists who have stayed in Ukraine and who somehow manage to continue their work in surroundings that are often difficult. Problems in Ukrainian science and education are a microcosm of those at national level. The issues that must be faced in solving those problems are extremely difficult, and many are contentious. It is inappropriate to discuss them here.

Ukraine does, however, have a national policy on nature conservation. The present work describes efforts by a team of Ukrainian and British scientists to provide infrastructure for fungal conservation within that national policy, through improved computing and informational resources.

Introduction

Microfungi are rarely considered within conservation policies for a number of reasons: they are small, poorly known (especially in the tropics), extremely diverse, and their fruit bodies are often ephemeral. They are frequently perceived at best as not charismatic, and at worst as threats to other species. However, it is probably true to say that the majority of fungi would be describable as ‘microfungi’ and many are likely to berare and threatened. Nevertheless, they may play important roles in the ecosystem through positive interactions with other organisms, and they represent an enormous range of genetic and metabolic resources. Thus, consideration of microfungi in relation to the issues that are addressed in conservation programmes for African animals and plants is appropriate, and represents a valuable model for many other organism groups.

One of the principal barriers to the inclusion of microfungi as targets for conservation is knowing whether species are genuinely rare, or simply rarely recorded. With the assistance of the UK Government's Darwin Initiative, we have addressed this problem in Kenya by collecting and studying fungal species which are associated with rare and endangered plants, and which are likely to be host limited. We can then be confident that the fungi are at least narrowly distributed, and are threatened to at least the same degree as their plant hosts.

Introduction

China is the world's major mushroom producing country. Agaricus production is mainly for export but Lentinula edodes (shiitake or shiang-gu) is the traditional local product, and now the major crop. Lentinula edodes is indigenous to China. It was first cultivated there more than 800 years ago, and today, China accounts for about 70% of world production. In 1997, Chinese production was recorded as 91 500 metric tonnes of the dried crop (drying produces the characteristic taste of the mushroom), ten times that in fresh weight. Shiang-gu (the Chinese name) is presently about the second or third most popular cultivated mushroom in the world, being consumed throughout China, Taiwan, Japan and Korea, and with increasing world-wide popularity. One-third of the Chinese crop is exported. As this amounts to the equivalent of about 300 000 tonnes of fresh mushrooms, the industry is an important earner of foreign exchange as well as making a very significant contribution to the income of peasant-farmers especially of the mountainous regions in China (Chang & Chiu, 1992). In these regions the land is poor in fertility and too distant from reliable transport to make conventional farming of green crops profitable.

Traditional technology

The traditional log-pile cultivation method is still the one that is most frequently used. For this, locally felled logs (oak, chestnut, hornbeam, maple and other trees) over 10 cm diameter (probably about 20 to 30 years old) and 1.5 m to 2 m long are normally cut in spring or autumn of each year.