Tropical Rainforest

The Green Sahara Of The Past

Tropical Sahara

Evidence from a whole range of sources shows that only a few thousand years ago, the climate of the whole Sahara region was very different from now. Animal bones in the desert sands show that giraffes and elephants once walked where there is now no vegetation and no water. The people who lived in the central Sahara at that time even recorded the animals they saw in rock paintings and engravings, vividly illustrating just how completely this place has changed in a few thousand years. A more...

The Worlds Major Vegetation Types

Coniferous Forests Chile

In the broadest sense the world's vegetation can be divided into several basic structural types, each of which includes several bionics 1. There is a set of forest vegetation bionics, which have a dense, closed canopy of trees. If you stand and look upwards in a forest, you see few large gaps between the crowns of the trees, which tend to overlap and interlock with one another. Forest biomes include tropical rainforest, temperate evergreen forest, temperate deciduous forest, and cold climate...

Box 53 Interactive vegetation schemes in dimate modeling

To simulate vegetation climate feedbacks, it is necessary to pass back and forth between a climate model and the vegetation cover. Initially, a particular climate and a vegetation distribution are set up together. The vegetation distribution can be whatever the modeler is interested to try out, and does not need to be anything that corresponds to the actual present-day vegetation, or anything that is in balance with the climate. The purpose of the exercise is to see how the two of them...

The Present Increase In C02

Tropical Rainforest United States Map

Since the late 1700s, the carbon dioxide level in the atmosphere has been increasing (Figure 7.10). The record of air bubbles trapped in polar ice shows the 18th century beginning stages of this rise, which has gently accelerated over time into a steep increase of about 1 a year. The change in C02 levels is also recorded in the stomatal densities of the leaves of trees preserved in herbaria leaves collected around 1750 have a lower number of stomatal pores per unit number of epidermal cells in...

Scrub Biomes

In climates that are too dry for forest but wetter than desert, one can either have scrub or grassland. Whether scrub or grassland actually occurs in a particular place depends on a range of factors including soil type, the time of year when rain occurs, lire frequency and the abundance of grazing mammals. It also depends partly on what species of plants happen to have evolved locally whether they are mostly grasses or mostly bushes. Also, if the soils are thin, infertile and rocky, scrub is...

Methane The Other C Arbon

C02 is a sort of common currency for the carbon cycle. It is produced in abundance by all living organisms, and is the chemically stable end point for many different processes going on in the earth's atmosphere, ocean and soils. It also participates in a whole range of different processes, including photosynthesis and chemical breakdown of rocks (sec below). Methane gas by contrast is only produced under special circumstances, usually where there is almost no oxygen. It is a result of the...

Microclimates and vegetation

Lotus Flower With Hands Clipart

Climate on the broad scale, across hundreds of kilometers, brings about the broad-scalc distribution of vegetation types (Chapters 1 and 2). However, even looking at the world much more locally, wc see that there arc also very substantial differences in the average climatc. For example, a south-facing slope has a different climate from a north-facing one. The year-round temperature and rainfall conditions under a tree will be different from those just a few meters away in the open. The...

Plants on the move

Skeleton Resting Head Hand Cartoon

3.1 VEGETATION CAN MOVE AS THE CLIMATE SHIFTS Bionics arc fundamentally determined by climate, as arc the ranges of most individual plant species. Whenever the global climate changed in the past, so did the form and species composition of vegetation in each part of the world. In the past couple of decades, geologists have become increasingly aware just how much the earth's climate can change, and often on far shorter timescales than would have been thought possible. Each of these changes must...

Biomes The Broad Vegetation Types Of The World

Tropical Regions The World

On the broadest scale, certain forms of vegetation occur again and again, scattered between different places around the planet. Depending on how finely you might choose to subdivide them, there arc between five and twenty fundamental vegetation types in the world. They include, for example, tropical rainforest and savanna in the tropics, and in the high latitudes temperate forest and steppe. Such broad-scale vegetation types are known as biomes. and each one of them is distributed between...

What Will Happen As The Warming Continues

Map Africa Rainforest

Eventually, global warming may get to the point where the present distribution ranges of species of plants and animals are left far behind the areas that they could potentially live in. For example, the potential range of sugar maple (Acer saccharum) might shift hundreds of kilometers to the north, way up into Canada towards the edges of the Hudson Bay (Figure 3.9). When this situation of a much warmer climate arises, the new vegetation zones and communities won't just snap into place...

Deciduous Or Evergreen The Adaptive Choicks That Plants Make

In some areas forests keep their leaf cover all year round. In others they drop their leaves part of the year and grow a new set after a few weeks or months. So one finds temperate deciduous forests in the northern temperate zone, but temperate evergreen forests in eastern Australia, southern China. New Zealand and parts of Chile (Figure 2.1). In some parts of the tropics, mainly near the equator, the forests are evergreen. In other places mainly the outer tropics the forests are deciduous. The...

An Example Of A Biome Or Broadscale Vegetation Type Tropical Rainforest

Rainforest Leaf Waxy And Drip Tip

In each biome, vegetation looks the way that it does because of selection by the environment. Natural selection has killed plants which had the wrong characteristics, and allowed others that had the right features to survive. By this mechanism, plants from many different lineages have evolved to suit the climate, often in quite subtle Figure 2.1. (b) Areas of the most intense human alteration of vegetation. Agriculture (dry croplands that depend on rainfall, plus irrigated croplands watered by...

From Microclimates To Macroclimates

Models Microclimates

The same factors which affect microclimates, including the plants themselves, translate into larger effects on the heat balance and moisture balance of the earth's surface. In many respects, the macroclimate (over hundreds of kilometers) is the sum total of all the microclimates across broad areas. For example, the local effect of a boreal forest canopy heating up in the sun because it has shed the snow from its branches can make a great difference to regional climate if it occurs on a broad...

Direct C02 Effects And The Ecology Of The Past

There are some fairly good indications that the C02 concentration of the atmosphere has undergone natural variations in the past, before humans began to affect it. The best substantiated changes in C'02 were those that occurred between glacial and interglacial periods during the last 650.000 years, where bubbles trapped in ice caps preserve samples of the ancient atmosphere that can be analyzed (Chapter 7). The evidence of such fluctuations in CO has set ecologists wondering what these might...

The Role Of Forest Feedback In Broad Swings In Climate

Geologists have established that the earth's recent history has been dramatically unstable. On almost any timescale one looks at during the last couple of million years, there have been both regular oscillations and sudden jumps in climate. And it is turning out that forest feedbacks may have played a substantial role in these past fluctuations. 6.5.1 Deforestation and the Little Ice Age Between 1000 and 1900 ad. forests in many areas of the northern mid-latitudes retreated under the onslaught...

Nutrients And Evergreenness

Hvcrgrccnncss is not only determined by climate soils can have a lot to do with it too. Part of the reason why boreal forests tend to have evergreen conifers may be that the soils underneath them arc nutricnt-deficicnt. Each time a plant changcs its leaves, some nutrients fail to be re-absorbed before the leaves are dropped, and are lost. If nutrients are in short supply, other plants that keep their leaves will grow faster and overtop this plant, and their roots will also grow fast and grab...

But Deserts Make Themselves

The South America Map Black

In addition to all of the more traditional climatology, there is another factor whose importance is only now becoming understood. Deserts partly owe their existence to the fact that they themselves exist. The desert makes the desert, internally modifying its own climate so that less rain falls So the link from climate to vegetation, in Chapter 1, has been turned on its head. A fundamental fact of the earth system, that climate scientists arc only now becoming fully aware of, is that vegetation...

The Great Heattransporting Machine

The decrease in temperature towards the poles forms the basic pattern of the earth's climates. But this pattern is greatly altered by the global circulation of two fluids air and water. Factoring in the circulation of air and water enables us to understand the present-day patterns of climate in more detail. One useful way to think of the world's climate circulation is to view it essentially as a heat-transporting machine that takes heat from the tropics and moves it to higher latitudes. It...

Irv gives rainv climateoff sea

How the rain-making machine of the tropics works. The heating of the ITCZ causes water to condense out and fall as rain. When the air descends again, no water vapor can condense out and there is an arid climate. it cools, and water droplets condense out as clouds and then fall as rain. This gives the moist tropical rainforest climate down below. A typical morning in the equatorial tropics begins clear and sunny. As the sun climbs high in the sky. the day becomes hot, but by...

Biomes Are To Some Extent Subjective

It is important to emphasize once again that one biomc docs not suddenly give way to another over just a few meters, as we might expect from looking at a biomc map. Instead of any sudden boundary, bionics tend to fade into one another over hundreds of kilometers. For example, as one moves over a long distance the trees in the forest may become on average more deciduous, or boreal conifers become more common in the vegetation. Patches of grassland mixed in with forest may become more and more...

Predicting Where Vegetation Types Will Occur

Fossil Grid Sampling Map

Knowing that bionics arc in a general way related to climate, ccologists have wondered if it is possible to predict which biomc will occur in a particular placc, using some simple set of rules based on climatic conditions. As well as providing a satisfying explanation of the present-day world, these predictive schemes are useful in enabling ccologists to look both forwards and backwards in time. They can be used (I) to predict how biomes will shift in the future in response to human disruption...

Volatile Organic Compounds And Climate

It is known that tree leaves evaporate many dilferent organic compounds (VOCs) out into the air around them, especially when they are heated under a hot sun. There are several groups of compounds, including monotcrpenoids and isoprcne, which arc thought to play some sort of protective role within the leaves, though no-one is quite sure what (it might, for example, be against insects, fungi or heat). The rate at which these chemicals are emitted depends on the particular forest type, and also...

Temperature Ani C02 ResponsewS Interacting

Over the next century or so, C02 itself will not be the only environmental factor changing. Climate is likely to become substantially warmer in most parts of the world, partly because of the greenhouse effect of the C02 itself. So, to know how-vegetation will really change, it may be helpful to try altering both factors simultaneously and see how they interact. There have been a few short-term (one or two year) open-top chamber experiments in the temperate zone which artificially warmed plants...

There Are Other Effects Of Enhanced C02 On Plants Apart From Growth Rate

Plants grown at higher C02 levels generally have a higher carbon-to-nitrogen ratio. It seems that because they have more carbon to work with, they end up producing more of the carbon-containing structural molecules of cell walls, such as cellulose and lignin. They may also store up excess carbon as starch reserves inside their cells. It is uncertain what implications these changes might have for ecosystem functioning for example, they might decrease the suitability of the plant as food for...

Wiiat Deforestation Does To Climate Within A Region

Tropical Rainforest Layers Diagram

What will happen if a forest is removed and replaced with much more open vegetation, such as grassland or fields of crops In a general way, there will be two competing effects on local climate. First, albedo will be greater over the more open grassland or cropland with patches of lighter soil between the leaves. This will tend to cool down the surface because solar energy is reflected straight back to space. However, the smoother surface of a grassland or crop cover and the smaller total Figure...

Coldclimate Evergreenness

Polar Tropical

Deciduous forests are a feature of mid-latitude climates with cold winters. Yet at still higher latitudes with even colder winters (as in much of Canada or Russia), evergreen conifers are dominant instead. This seems to contradict the explanation for temperate trees losing their leaves surely here the need to drop leaves in winter is even greater, and yet these are evergreens. However, another factor has entered the equation, the briefness of the growing season in the high latitudes. The...

Wiiat Favors Forest Vegetation

Across nearly half of the world's land surface, the original vegetation is forest. In some places it is easy to tell that forest is the natural vegetation because the landscape is still covered by it. For example, the eastern USA and southeastern Canada are at present mostly forested. Even areas in eastern North America that arc kept as farmland will go back to forest if left for several decades. Within just a few years an abandoned field will become covered with tree seedlings that have...

Response Of Vegetation To Tiie Present Warming Of Climate

Www Climate And Vegetation Drawing

There are of course many aspects of plant ecology that seem tightly controlled by temperature the broad-scale distribution of biomes across the continents is one example (Chapter 2). Temperature also determines exactly how high up a mountain trees can grow, and the precise time of year that trees start to leaf out, or when spring flowers appear. It also determines how fast a tree can grow, with variations in climate showing up in the width of the annual rings. Because of the amplifying factors...

Watching Forests Take Up Carbon

Because of the present and future importance of forests affecting the time course of the rise in atmospheric C02, there is presently a lot of work going on to understand whether and how fast they are taking up carbon in particular parts of the world, and how they respond to climate fluctuation. When modern ecosystem ecology first began in the 1960s, studies of forest growth concentrated on estimating the amount of wood added to all the trees throughout the forest, from the width of tree rings...

Box 81 Q C3 and CAM plants

Sequences Pathway Water Plants

Many plants in arid environments decrease the problem of water loss through stomata by chemical tricks that help them take up CO with less water loss. These are known as C4 and CAM plants. Most plants are known as C3 plants. They take CO up into leaf cells which handle the whole photosynthetic reaction in the same cells. The C02 gets fixed into a three-carbon chain (hence the name C3), and then in the same cell the water-splitting part of photosynthesis gives the hydrogen needed to tack on to...

Other Face Experiments

When tundra ecosystems in northern Alaska were exposed to increased C02 at nearly 600 ppm in a FACE experiment, there was an initial increase in growth which disappeared after 2 3 years. This particularly short-lived response is thought to occur because tundra ecosystems are highly nutrient-limited they cannot respond well to the extra carbon supply by increasing plant tissues because the nutrients they also need to build their tissues are in such short supply. Other FACE studies have included...

The climate system

Though few people stop to think of it, much of the character of a place comes from its covering of plants. Southern France, with scented hard-leaved scrublands, has an entirely different feel about it from the tropical rainforest of Brazil, or the conifer forests of Canada. Vegetation is as important a part of the landscape as topography and the architecture of buildings, and yet it is an accepted and almost subconscious part of the order of things. Even fewer people ever ask themselves why...

Utilization of microclimates in agriculture

Many of the aspects of microclimates that affect plant ecology also apply to agriculture. Good farmers plan their planting to avoid unfavorable microclimates avoiding frost pockets for sensitive crops, and allowing for the effect of aspect on temperature or water balance. They can also try to make new microclimates which will favor the plants they are growing. Shelter belts of planted trees or bushes create a drag that slows down the drying or cooling wrinds that blow across farmland. The...

Geography Makes Deserts

The world's broad desert belts north and south of the equator result from the global circulation pattern (Chapter 1) equatorial air rises up into the atmosphere, heated by intense sunlight and loses its water vapor as sudden rainstorms. Eventually, this air comes back down hundreds of kilometers from the equator, and heats up as it is compressed, holding even more tightly onto what little water vapor remains within it. In such a situation, with dry air nearly always moving in from above, there...

Seasons As Well As Vegetation Distribution Are Changing

For a long time, naturalists and gardeners have recorded dates of flowering and leafing of the plants around them. These records happen to provide another interesting measure of responses to climate change. In Europe, it is quite evident that the seasonal patterns in vegetation have been shifting in response to warmer temperatures. In Britain, for example, a long tradition of amateur natural history has ensured an abundance of information on the detailed distribution and behavior of plants,...

Humans And The Carbon Store Of Plants

No single species alters the world's habitats as much as humans do. Even in distant prehistory, the arrival of people in a particular part of the world could be heralded by an increase in burning. For example, in Australia there was a sudden jump in fire frequency around 45.000 years ago, right around the time when humans first show up in the archaeological record. From what we know of the Australian Aborigines and other hunter-gatherers when they were first contacted by Europeans, humans...

Could The Sahara Be Made Green

Some models that involve both vegetation and climate have suggested the hidden potential for far more extreme changcs in the climate of the Sahara than we have witnessed over the past century. These models have conccntratcd so far on just the western half of the Sahara desert. They tend to find that if you were to blanket the whole of the western Sahara desert in a leafy cover of grass or bushes, the climate of the region would be transformed. The low albedo, the greater roughness, the capturc...

What factors tend to decrease plant responses to CO2 fertilization

Some vegetation types respond more strongly to C02 than others, but all seem to show at least some decline in C02 response over time. Various factors seem to be at work in producing both the variation in response and the decline in response. Probably the most important of these is nutrient supply. The more nutrient-deprived the system is. the less responsive it tends to be to CQ2 fertilization. Also, much of the decline in C02 response over time seen in raised C02 experiments is thought to be...

Other Direct C02 Effects In The Oceans

Ocean plankton do not tend to be limited by lack of C'02, because it is already present in dissolved form in such abundance in the ocean water. In addition, they tend to be severely limited by lack of nutrients, which cuts down how much they could potentially benefit from more CO . However, there may be another insidious effect of high C02 levels that could have far-reaching consequences for ocean ecosystems and perhaps the whole planetary system. Some of the most abundant ocean plankton, known...

The Future Direct C02 Effect A Good Or A Bad Thing For The Natural World

If dircct COi fertilization turns out to have significant cffccts on the natural world, will these cffccts be good or bad The effects are likely to be complex and multi-faceted, and whether they are. on balance, likely to be good or bad is a subjective issue that depends on one's priorities. Some scientists, and groups supported by the fossil fuel lobby, have argued that C02 fertilization might turn out to be a very good thing for nature in general. By allowing plants to thrive on less water,...

Other Trends In Forest With Climate

There are also trends in the appearance of trees along rainfall gradients. Generally, individual leaf sizes of trees get smaller as you move from a very moist tropical climate (e.g., the central Amazon Basin) to a rather drier hotter climate (e.g., the southern Amazon Basin), even if it is still covcrcd in forest. It has been suggested that this is because drier climates can get hotter (sec Chapters 5 and 6 for the reasons for this) and a big leaf cannot loose heat as well as a small one when...

The Two Direct Effects Of Co On Plants Photosynthesis And Water Balance

Carbon dioxide may affect plants by changing the climate, but it can have another more subtle and quite separate influence, through its direct effects on plant physiology. Since CO is fundamental to photosynthesis, it makes sense that increasing the amount of CO in the atmosphere will tend to allow plants to photosynthesize faster. This then is one-half of the direct C02 effect on plants. But there is also another less straightforward direct effect of C02 on the water balance of plants. Why...

Box 52 Simulating climate GCMs and mesoscale models

What changes can we expect for the Earth's climate over the coming decades, as greenhouse gases increase Because of the importance of knowing the answer to this question, a lot of effort is going in to understanding and forecasting climate change. The world's most powerful computers (known as supercomputers) are used to calculate the effects of a given rise in greenhouse gases on global climate, using a model a simplified world inside the computer, complete with oceans, continents, mountain...

The Increasing Greenhouse Effect And Future Vegetation Change

The greenhouse ellect keeps the earth warm enough for life, and lack of it makes mountains cold (Chapter I). But now the warming from the greenhouse ellect is intensifying, as humans push more and more of the so-called greenhouse gases into the atmosphere (see Box Section 1.1). Leading amongst these gases is C02. released by fuel-burning and deforestation. Its concentration is already 40 higher than it was 200 years ago, and it looks set to double by 2050 (Chapter 7). Methane is another...

Humans Altering The Natural Vegetation Shifting Biomes

In some areas the natural vegetation has been almost totally removed such as where there are now ploughed fields or cityscapes. But, in many other places, the effect of human actions has been more subtle. Often the result of anthropogenic influence seems to be a downgrading of the vegetation to something that might be found in a rather drier or colder climate. For example, a meadow in the English countryside can only exist under human influence the forest that once covered the land has been...

Interaction

How Vegetation Makes the Global Environment How Vegetation Makes the Global Environment Assistant Professor in Biological Sciences SPRINGER-PRAXIS BOOKS IN ENVIRONMENTAL SCIENCES SUBJECT ADVISORY EDITOR John Mason B.Sc., M.Sc., Ph.D. ISBN 978-3-540-32491-1 Springer Berlin Heidelberg New York Springer is part of Springer-Science + Business Media (springer.com) Library of Congress Control Number 2007923289 Apart from any fair dealing for the purposes of research or private study, or criticism or...