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...

Predicting Where Vegetation Types Will Occur

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...

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...

What Will Happen As The Warming Continues

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...

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...

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...

Why Does Climate Vary From One Place To Another

Ekman Spiral

Essentially, there arc two main reasons that climate varies from place to place first, the amount of energy arriving from the sun, and second the circulation of the atmosphere and oceans which carry heat and moisture from one placc to another. One of the major factors determining the relative warmth of a climate is the angle of the sun in the sky. The sun shines almost straight at the earth's equator, because the equator sits in the direct plane of the sun within the solar system. So, if you...

The Future

With greenhouse gases increasing in the atmosphere, it is likely that the world's climatc will changc significantly over the next century or two. Vegetation feedbacks will surely have a role to play in this change too perhaps amplifying changc, perhaps damping it. There has not been much discussion in the scientific literature so far on how-vegetation feedbacks in arid zones will alter the course of changing climate, but it is a reasonable guess that they will have some significant effects....

Bibliography

J.M., Constable, J., Gucnther, P. and Zimmerman, P. (2001). Estimate of total VOC emission from global vegetation at the Last Glacial Maximum, compared to the Holocene. Chemosphere - Global Change Science, 3, 73-91. Adams, J.M., Green, W. and Zhang, Y-J. Recalibrating the paleoclimatic thermometer broad scale analysis of leaf margin trends against temperature in North America. Global and Planetary Change (submitted). Barnola, J.-M., Raynaud, D., Lorius, C. and Barkov, N.I. (2003)....

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...

The Worlds Major Vegetation Types

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...

But Deserts Make Themselves

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...

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...

Biomes The Broad Vegetation Types Of 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...

An Example Of A Biome Or Broadscale Vegetation Type Tropical Rainforest

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...

Forests

Forests temper a stern climate, and in countries where the climate is milder, less strength is wasted in the battle with nature Since the beginning of agriculture, 12,000 years ago, humans have had an uneasy relationship with forests. On one hand, the forests provided timber, and good hunting for game. But they also took up space where crops might be grown, and provided a refuge for malevolent creatures both real and imaginary. As farming spread out from its first heartlands in the Middle East,...

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...

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...

Dust

So far, we have considered albedo, roughness and evaporation of water in the feedbacks between vegetation cover and climate. Another potentially important vegetation climate feedback comes from dust. The dust in the atmosphere mostly consists of particles of soil, fragments of the sorts of minerals that make up rocks and clays. These tiny particlcs tend to scattcr sunlight. Dust is really a product of vegetation covcr, or rather a lack of vegetation cover areas with lots of bare soil between...

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 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...

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...

Wiiat Deforestation Does To Climate Within A Region

Tropical Region Solar Energy

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...

Microclimates and vegetation

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...

Box 81 Q C3 and CAM 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...

From Microclimates To Macroclimates

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...

Plants on the move

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...

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,...

The Green Sahara Of The Past

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...