Light and shade

Acer Leaf Damage

3.2.1 Influence of shade on tree development Owing to their height and complex structure, there can be less light near the ground in forests than in any other terrestrial vegetation type. Shade can thus be a very important factor in determining the forest dynamics. Very great variations occur in the light levels reaching the floors of, for example, Scandinavian forests in which periodic storms produce mosaic patterns of light and shade. Tree fall greatly increases the amount of light reaching...

What controls the rate of decomposition

Forest Litter Decomposition

Three major factors control decomposition climate, quality of the litter, and the soil microbial and faunal communities, as shown in Fig. 7.3. Other factors Figure 7.3 Factors that affect how quickly litter decomposes. (Reprinted from Prescott et al. 2000. Forest Ecology and Management 133 with permission from Elsevier.) Figure 7.3 Factors that affect how quickly litter decomposes. (Reprinted from Prescott et al. 2000. Forest Ecology and Management 133 with permission from Elsevier.) can be...

Fiby urskog soils topography and zonation of a Swedish primitive boreal forest

Boreal Forests First Level Consumers

The majority of northern hemisphere forests have now been heavily influenced by humans, so those such as Fiby urskog (Hytteborn and Packham, 1985 Fig. 2.7) which have been relatively little affected in this way, are especially interesting in showing local natural zonation and variation of forest vegetation. Though the highest parts of the reserve are now 60-65 m above mean sea level, they were exposed to wave action when the land first emerged from the sea, so drift and other sediments were...

Roots foraging and competition

Norway Spruce Root Pattern

The radicle (embryonic root) of a seedling often continues to grow downwards as a primary or tap root, but in most trees the main root system consists of secondary lateral roots which grow sideways away from the stem, usually no more than 1-2m below the soil surface but with some deeper roots. Different species have different rooting patterns and in this respect three common European conifers differ greatly in their ability to adapt to varied soil conditions. Young silver fir Abies alba has the...

Vascular plants soilpH mineral nutrients and microorganisms

Figure 2.3 emphasizes the important influence of soil pH chemical weathering, for example, proceeding very much faster in the most acid soils. Humification (the breakdown of dead plant material to humus) and biotic activity in general increase towards the mid-range of pH and then drop away as soils become alkaline. Soil bacteria and fungi react differently to variation in soil pH, though it strongly influences both. The optimum pH for soil bacteria is slightly on the alkaline side of neutrality...

Temperaturemoisture gradients below the timberline

Sierra Conifer Species Elevation Diagram

Altitude, and the changes in environmental conditions that go with it, plays just as important a role below the timberline as at the top. For example, there is a well-marked temperature-moisture gradient from the warm, dry lowlands to the cold, wet mountain peaks in the north-western region of the USA shown in Fig. 3.18. The lower limit for these trees usually shows a gradual transition, apparently set by soil moisture levels. Ponderosa pine Pinus ponderosa, Douglas fir Pseudotsuga menziesii,...

Ecological problems of understorey plants

Understorey plants are by definition those living below the tree canopy. Unless the canopy is very open, as in birch woodlands, light will be in short supply for most of the growing season (see Section 1.3.2 above), hence it is referred to as the dark phase of the year. Deciduous canopies will go through the light phase in the non-growing season when the leaves have fallen but, of course, most understorey plants will not then be growing. Evergreen trees have a year-round dark phase. In the...

Genetic variation in populations and its implications

Genetic variations exist in virtually all forest organisms they are particularly important in tree species and in the pests and pathogens that attack them. The genetic basis of forest pathology and its influence right up to the landscape level was the basis of the 1999 Montreal symposium of the American Phytopathological Society. Much of what was discussed then has been updated (Lundquist and Hamelin, 2005) in a volume that emphasizes how rapidly long-lived trees and forests can be devastated...

Hemlock woolly adelgid

The hemlock woolly adelgid Adelges tsugae is a small aphid-like insect, less than 1 mm long, wrapped up in a white, woolly mass when laying eggs (Fig. 5.8a), that as the name suggests, infests hemlock (Tsuga) trees. Native to Asia, it was first found in western North America in 1924 and then spread through the continent, probably carried on infected hemlock trees. The hemlock woolly adelgid became a problem when it reached the east coast in the early 1990s because the two hemlock species here -...

Wind cold and wave regeneration

Wind Speed And Rain Angle

Wave regeneration is a particularly regular form of cyclic change in which mature trees continually die off at the front edge of the wave, which lies behind an opening in the forest canopy and is thus exposed to the prevailing wind. In balsam fir (Abies balsamea) forests at over 1000 m in north-eastern USA, young trees spring up after the wave has passed on at a speed of 1-3 m y_1 (Fig. 9.8). Though the dead trees often remain standing for some time, they no longer exert sufficient shade to...

Pollution acid rain and forest decline

Acid Rain Pollution Facts

Acid rain became a problem when combustion of fossil fuels increased after the industrial revolution, releasing increasing quantities of sulphur dioxide (SO2), nitrogen oxides (NOx - see next section for a definition) and other acidifying particles into the atmosphere to join what is naturally produced. The sulphur dioxide and nitrous oxides dissolve in atmospheric moisture to form sulphuric (H2SO4) and nitric (HNO3) acids which are brought to ground as acid precipitation. Unpolluted rain has a...

Woody material

Populus Tremula Boom

Dead wood in a forest is much more variable in time and space than leaf litter and consequently has been the Cinderella of the forest, largely ignored for a long time but now seen to be crucially important. Dead wood appears in many forms, sizes and positions (and so is difficult to measure) including standing dead trees (snags), dead branches in the canopy, and trunks and branches on the ground. It should also include the dead heartwood of living trees but, as George Peterken (1996) points...

Pollination strategies

Sycamore Seed Dispersal Mechanism

Forest plants face a number of problems in respect of pollination, from the sheer size of the larger trees to the still, dark conditions inside a forest hampering pollinators. Trees in northern and temperate forests, especially the conifers, tend to be wind pollinated (anemophilous) but towards the tropics the trend is towards animal pollination, particularly by insects (entomophilous). Wind pollination is often seen as primitive and wasteful of pollen (a single birch catkin can produce 5.5....

Masting

Infection Holes Hand Caused Insect

Masting is the irregular periodic synchronous production of large seed crops in perennial plants such that the majority of trees produce heavy seed crops in certain years (the mast years) while in other years the crop is small or nonexistent. The pattern of reproduction involving the production of a superabundance of seeds became known as mast seeding from the German word for fattening livestock on abundant seed crops, so that years of high abundance became known as mast years. In many species,...

What allows species to coexist in a woodland

This question has taxed ecologists and foresters for centuries and has been the theme of thousands of publications. Despite this, we are still struggling to explain why one or just a few species do not come to dominate a forest by killing off the weaker species. Requirements for certain species are remarkably precise, as in the case of Abbot squirrels which have become so dependent on Ponderosa pine, whose seeds and shoot-tip bark they consume, that they are now found only in association with...

Box 91 Influence of humans on the forests of Crete and Cyprus

Cyprus Mediterranean Forests

The deposits of Knossos, Crete, provide an almost continuous record of the activities of humans since 6000 BC, including Minoan times when wild boar were numerous. Human influence has greatly changed the forests of this Mediterranean island, which is some 160 miles from west to east. Beneath the bare peaks of the limestone mountains, remnants of the once extensive cypress Cupressus sempervirens and pine forests clothe the upper ranges. The Calabrian pine Pinus brutia, sometimes treated as a...

Altitudinal zonation and timberlines

What Altitudinal Zonation

The polar margin of arctic forests and the upper margin of subalpine forests i.e. forests on mountainsides just below the treeless, alpine zone have cold timberlines. In reality these are facets of the same environmental conditions shown in Fig. 3.15a the alpine timberline becomes lower in altitude away from the equator until it reaches sea level near the poles. The ultimate factor determining timberlines is decreasing temperature with altitude and latitude in the northern hemisphere forest...

Silviculture and the replacement of trees

Coppicing Alder Trees

Silviculture treats forest trees as crops which are established, tended, harvested and then replaced by others. Essentially it is that part of forestry which involves an understanding of how trees modify, and are influenced by, the ecosystems in which they live. A silvicultural system encompasses a the regeneration of trees, b the form of the crop produced and c the orderly arrangement of the crops over the forest as a whole. The main groups of forest system described below have many variants...

Persistence variation and adaptation within the genus Pinus

Lodgepole Pine Serotinous Cones

Pinus has been accurately described as the 'most ecologically and economically significant tree genus in the world' Richardson and Rundel, 1998, p. 3 . It has 111 species, mostly restricted to the northern hemisphere, and this ancient genus, of which the earliest representatives date from the Lower Cretaceous around 120 Ma, is still remarkably successful. Indeed several species, often through the intervention of humans, are currently increasing their range. By the end of the Mesozoic 65 Ma...

Specialized heterotrophs epiphytes parasites and saprotrophs

5.5.1 Epiphytic plants and lichens and surface-living microorganisms A large number of autotrophic algae, lichens and higher plants such as bromeliads and orchids hitch rides on the external surfaces of living plants, especially in moist subtropical and tropical climates. They take nothing from the host except a safe anchorage and so are classed as externally attached autotrophs epiphytes . These obvious large epiphytes are accompanied by a much more widespread and varied microflora of...

The nature of biodiversity

Importance Forest With Diagram

Biodiversity can be defined as the variety and abundance of species, their genetic composition, and the communities, ecosystems and landscapes in which they occur Maclaren, 1996 . The term is sometimes used very narrowly to refer to species-richness, but should be employed to describe the full complexity of life on Earth. Such descriptions still have far to go as Box 7.1 points out, some 200 000 fungi have so far been described but these represent only a fraction of those believed to exist....

Soils and trees

Soils are often given superficial treatment, and yet without them forests would quickly cease to function. As well as physically supporting plants, soils act as refuse collectors, processing organic waste and thereby recycling nutrients, a major influence on the productivity of forests. Without functioning soils, forests would rapidly be choked with dead wood and other material, and the bulk of nutrients needed by plants and animals would be locked up and unavailable. Moreover, soil is not...

Climate change

Forstkiste

The climate of the Earth has changed naturally many times since the origin of life at the beginning of the Cambrian. The present global warming the temperature of the Earth has increased during the twentieth century by 0.76 C differs from those of the past in that it has almost certainly been initiated by the activities of humans. During the twentieth century the atmospheric concentration of carbon dioxide CO2 rose by 35 from 280 parts per million ppm to 379 ppm in 2005. The concentrations of...

Box 41 Seedcaching birds

Mangrove Zonation

The Corvidae, a widespread group of rather aggressive birds including the ravens, crows, rooks, jackdaws, magpies, jays, choughs and nutcrackers, show considerable intelligence and the rooks in particular seem to communicate by their calls. The group as a whole has a rather mixed diet, some feeding on carrion, but a number of corvids also form caches of seeds as a winter food supply. In doing so, they are crucial to the establishment of a number of tree species from seed. Most prominent are the...

Ecology of past forests

Pityostrobus

9.1.1 The Palaeozoic era and tectonic plate theory Woodlands and forests of the past were often very different from those we know today. In this matter, as in so many others, the Greek philosopher Heraclitus was correct in stating that only change is constant. Moreover, the changes known to have occurred in the world's flora and fauna have sometimes been very abrupt Toghill, 2000 , as in the biggest mass extinction of all time which occurred at the end of the Permian period 245 Ma i.e. millions...

Spatial structure

Rainforest Stratification

1.4.1 Vertical structure above and below ground Though some may be missing, in most forests it is possible to recognize four distinct layers of vegetation starting with the tree canopy at normally 5 m Fig. 1.4 . Under this are the underlying shrubs, including climbers lt 5 m , the field or herb layer of herbaceous plants lt 1m made up of herbs - plants without woody stems - and short woody plants such as brambles , and a ground or moss layer of mosses and liverworts bryophytes , lichens and...

Seasonal changes and aspect societies

Rain Forests

Phenology is the study of the onset and duration of the activity phases of animals and plants throughout the year Sections 4.6.1, 11.3.2 . These are largely synchronized to the weather so the dates on which they occur differ from year to year. Though the order in which the various plant species unfold their buds, flower, fruit and senesce is much the same different individuals of the same tree species frequently commence leafing out flushing earlier or later than their fellows. This influences,...

Influence of herbivores

Insect Groups

The size and vigour of particular herbivore populations at a given time is a major influence on forest trees and other plants. Many examples could be chosen to illustrate this point here we consider deer and elephants. Deer have increased in number and expanded their range in many parts of the world over the last few decades, becoming a particular problem Section 5.7.1 . This is partly due to our previous management. Historically game managers strove to augment and protect deer populations, and...

Changes in species diversity over time

Animals Change Over Time

6.4.1 Plants, lichens and fungi indicative of old woodland Biodiversity may be related to the age and previous history of the ecosystem concerned. For example, the richness of epiphytic lichen communities is frequently related to the length of time the dominant trees have been established in the forest. Fagus sylvatica has a south-western distribution in Sweden where aged beech trees in old forest stands often have an extremely rich lichen flora including the rare Lobaria pulmonaria, a leafy...

Saprotrophic parasitic and hemiparasitic plants

David Morse Florida Forest Service

A number of plants have lost their autotrophic status by losing their ability to photosynthesize, and live instead as heterotrophs, either as saprotrophs or parasites. The saprotrophs essentially live by extracting food from decomposing leaf litter using fungi as an intermediary and so should be called myco-heterotrophs living off fungi , as outlined in Box 3.1. It is often difficult to tell what the fungus receives in return from the plant perhaps the plant is primarily parasitic on the fungus...

The nature offorest soils and their influence on the ground flora

Soil Catena Podzol Brown Earth

Traditionally, soils of high quality have been used for agriculture, so those beneath long-established woodlands were usually not only of lower original quality, but have not been limed, fertilized and drained. Such human manipulations have sometimes influenced the soils of modern plantations to such a degree that this causes difficulties when attempts are made to introduce characteristic woodland floras Section 11.6.2 . Conversely, in many parts of the world abandoned agricultural land has...

The woodland ecosystem food chains food webs and the plant animal and decomposition subsystems

Woodland Ecosystem

Trees dominate the woodland and forest communities in which they grow but hosts of other organisms - including fungi and bacteria - which evolved in parallel with them, live beside, beneath and in them in an interacting whole. The types of animals involved in such communities are illustrated in Fig. 1.8 in many other parts of the world the major differences from western European forests involve the presence of much larger herbivores and carnivores and of primates such as monkeys and gorillas....

Rainforest distribution and vulnerability

European Rain Microorganism

There is widespread concern about the decline of forests around the world, especially at lower latitudes. Tropical forests are causing particular concern given that they contain more than 50 of all the species on Earth, and have a large economic value. Even more critically, more than 50 million indigenous people live in tropical forests Amazonian forests alone hold 400 indigenous groups composed of 1 million people Bryant et al., 1997 . Costanza et al. 2003 calculate that the current economic...

Plant strategies

Witchcraft Triangle Hebrew

4.1.1 Strategic response to competition, disturbance and stress The concept that living organisms display ecological 'strategies' has advanced rapidly in recent years. The r-K continuum of MacArthur and Wilson 1967 made an important early contribution in contrasting the opportunistic r-species with rapid rates of population growth , which exploit temporary habitats, with the equilibrium K-species of stable habitats in which competitive ability and survival of the individual is more important...

Box 83 Nutrient dynamics at Hubbard Brook

Molde Ramos Arvore

The long-term studies revealed that over the last half of the previous century the undisturbed northern hardwood forest showed a long-term net retention i.e. more came in with precipitation than left in stream water of hydrogen H , chlorine Cl , N and P, and net losses of Ca, Mg, Na, K, sulphur S , silicon Si and Al. Likens 2004 suggests that the net loss of calcium is attributable to acid rain, reducing the input of Ca in precipitation and increasing its leaching from soil. Certainly the...

Box 101 Connectivity in a fragmented landscape

A good example of woodland fragmentation and connectivity is provided by communities of the maritime juniper Juniperus oxycedrus ssp. macrocarpa, a Mediterranean species tolerant of saline spray along the south-west coast of Spain, which are both vulnerable and ecologically important. Though now greatly reduced in area, it seems that these formerly extended from the El Rompido cliff in Huelva to the west all the way to Gibraltar in the east. Studies by Munoz-Reinoso 2004 are designed to form...

Plant life forms and biological spectra

Bluebells Perennating Buds Location

3.1.1 Variation in vascular plant and bryophyte life form In addition to taxonomic classifications which endeavour to place closely related species in the same family, botanists have for centuries attempted to distinguish particular life forms, any one of which may be adopted by quite unrelated species. The simplest of these is the distinction between woody and herbaceous plants. Raunkiaer 1934 developed the most widely known scientific description of life forms, and then used it to initiate...

Forest types and classification

Terrestrial Biomes

1.6.1 Distribution in relation to climate biomes Living organisms have very distinct distributions there are at least 400 000 species of flowering plants but not one occurs everywhere in the world. There are, however, communities of plants and animals found over often extensive regions of the world that have a similar and characteristic appearance or physiognomy as defined by their life form see Section 3.1.1 and principal plant species. These major ecological communities are known as biomes...

Rain forests climate soils and variation

Hopea Parviflora

2.5.1 Tropical rain forests the changing archetype Corner 1964 considered tropical rain forest to be the cradle of flowering plant angiosperm evolution and that all other forest types were derived from it - it is the archetype, the earliest common ancestor. Early trees such as those of the Coal Measure forests see Section 9.1 and Fig. 1.1 , as well as the first seed plants and the first flowering plants, do indeed appear to have evolved under conditions of high temperature and constant...

Assessment of production use of the yield class system and the importance of spacing in commercial forestry

Sitka Spruce Growth Rates

Detailed assessment of timber and of tree growth is accomplished using forest management tables such as those employed by the British Forestry Commission Hamilton and Christie, 1971 Edwards, 1983 . As trees grow they increase in fresh weight, dry weight, height and volume, of which foresters usually measure the last two. Measurable volume is normally taken as that of stemwood exceeding 7 cm diameter overbark, and the pattern of growth in an even-aged stand is described in terms of annual volume...

Habitat creation and conservation

In recent years the creation of attractive herb communities, for both meadows and woodland floors, has become increasingly common in areas used by the public Buckley, 1989 . Helliwell 1996 , who has worked on habitat transfers involving grassland, marshland and woodland, provides a valuable summary of the general principles involved, paying particular attention to soils and the need to appreciate the considerable differences between the various layers of strongly stratified soils when this...

Biomass and productivity

Hubbard Brook Nutrient Cycling

The sheer size of forest and woodlands is what people often comment upon. The weight or mass of organic material present is referred to as the biomass or sometimes the standing crop . It should be borne in mind that this can be a somewhat loose term since it may or may not include dead wood or litter. Table 8.1 shows that the biomass above ground increases from the boreal forest towards the tropics, starting from very low levels at the Arctic treeline and reaching in excess of 9401 ha-1 in the...

Rates of decomposition

Rate Decomposition Ammonia

7.6.1 k values and mean residence time With so many factors potentially affecting decomposition it is no surprise that decomposition rates vary tremendously around the world. These rates can be expressed in absolute terms as the weight of litter that disappears in an area Figure 7.6 Estimates of the decomposition rate constant k for different forests, defined as the ratio of amount of annual litterfall to the amount of organic matter in the forest floor. Higher values of k indicate more rapid...

Herbivorous mammals and birds

Rainforest Herbivores

Mammals have played a major role in the world's forests over a very long period. Their numbers are small compared with insects and other invertebrates, but their individual biomasses are large so collectively they have made a major impact on forest ecosystems. In Pleistocene times, for example, when even Australia had a marsupial elephant, elephants even larger than those of today were widespread. These enormous animals, which could break down large trees Rackham, 2002 , appear to have been...

Soil profiles and properties

Soil Profile Rendzina

Soil profiles of the kind shown in Fig. 2.2 occur in many of the world's temperate zones see also Box 2.1 . Soil reaction or pH is an important property influencing the availability of important mineral elements in different Figure 2.2 Profiles of common British soil types. The organic O horizon can be divided into three distinct horizons as shown depending upon the degree of decomposition of the litter and its integration into the soil below. The A and Ai horizons shown in Fig. 2.1 are here...

Fungal hotspots of insect diversity in boreal forests

Boreal Forest Biodi Versity Hufson

The fact that many species of insect are found in association with wood-decaying macrofungi has long been known, but these have often been clumped together with other invertebrates associated with dead and decaying wood. Up to a thousand species of fly and the same number of beetles are believed to be associated with these two habitats in Fennoscandia alone. A review of recent major advances in our knowledge of species-richness, host specificity and the Figure 6.8 Ant hill beneath Norway spruce...

Light and shade plants growth analysis

Morphology Figure Ground

Figure 3.8 Transverse sections through leaves of yellow archangel Lamiastrum galeobdolon ssp. montanum left and of wood-sorrel Oxalis acetosella right . Both species are hypostomatous, i.e. have their stomata restricted to the undersides of the leaves. a , a0 sun leaves b , b0 shade leaves, whose palisade mesophyll consists of funnel cells see text for an explanation . From right Packham and Willis, 1977. Journal of Ecology 65 left Packham and Willis, 1982. Journal of Ecology 70, Blackwell...

Dutch elm disease

Life Cycle Dutch Elm Disease

Dutch elm disease DED , one of the more serious tree diseases in the world, acquired its name because so much early research on it was done in the Netherlands Gibbs et al, 1994 , rather than this being its source. Dutch elm disease, which may have originated in the Himalayas, is widespread throughout the natural distribution of the elm apart from China and Japan it has even attacked exotic elms in New Zealand. Discovered in a number of European countries shortly after World War I, the first...

Box 13 An example of the UK National Vegetation Classification NVC Wistmans Wood Dartmoor Devon

Types Classification Ecology

Wistman's Wood, owned by the Duchy of Cornwall, has been managed since 1961 under a nature reserve agreement with what is now Natural England, the Government conservation body. This long narrow 3.5 ha wood is divided into the North, Middle and South Woods, all situated in the valley of the West Dart river. Its vegetation in general conforms to W17, an upland Oak-Birch-Dicranum moss woodland majus woodland, subcommunity Isothecium myosuroides-Diplophyllum albicans , a grouping in which...