What causes microclimates to form


Microclimate, any climatic condition in a relatively small area, within a few metres or less above and below the Earth’s surface and within canopies of vegetation. The term usually applies to the surfaces of terrestrial and glaciated environments, but it could also pertain to the surfaces of oceans and other bodies of water.

The strongest gradients of temperature and humidity occur just above and below the terrestrial surface. Complexities of microclimate are necessary for the existence of a variety of life forms because, although any single species may tolerate only a limited range of climate, strongly contrasting microclimates in close proximity provide a total environment in which many species of flora and fauna can coexist and interact.

Microclimatic conditions depend on such factors as temperature, humidity, wind and turbulence, dew, frost, heat balance, and evaporation. The effect of soil type on microclimates is considerable. Sandy soils and other coarse, loose, and dry soils, for example, are subject to high maximum and low minimum surface temperatures. The surface reflection characteristics of soils are also important; soils of lighter colour reflect more and respond less to daily heating. Another feature of the microclimate is the ability of the soil to absorb and retain moisture, which depends on the composition of the soil and its use. Vegetation is also integral as it controls the flux of water vapour into the air through transpiration. In addition, vegetation can insulate the soil below and reduce temperature variability. Sites of exposed soil then exhibit the greatest temperature variability.

Topography can affect the vertical path of air in a locale and, therefore, the relative humidity and air circulation. For example, air ascending a mountain undergoes a decrease in pressure and often releases moisture in the form of rain or snow. As the air proceeds down the leeward side of the mountain, it is compressed and heated, thus promoting drier, hotter conditions there. An undulating landscape can also produce microclimatic variety through the air motions produced by differences in density.

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The microclimates of a region are defined by the moisture, temperature, and winds of the atmosphere near the ground, the vegetation, soil, and the latitude, elevation, and season. Weather is also influenced by microclimatic conditions. Wet ground, for example, promotes evaporation and increases atmospheric humidity. The drying of bare soil, on the other hand, creates a surface crust that inhibits ground moisture from diffusing upward, which promotes the persistence of the dry atmosphere. Microclimates control evaporation and transpiration from surfaces and influence precipitation, and so are important to the hydrologic cycle—i.e., the processes involved in the circulation of the Earth’s waters.

The initial fragmentation of rocks in the process of rock weathering and the subsequent soil formation are also part of the prevailing microclimate. The fracturing of rocks is accomplished by the frequent freezing of water trapped in their porous parts. The final weathering of rocks into the clay and mineral constituents of soils is a chemical process, where such microclimatic conditions as relative warmth and moisture influence the rate and degree of weathering.

But just as the outdoors has microclimates, indoor spaces can also produce The reason for this is a combination of factors that include an advancing knowledge in . All three examples demonstrate the lengths designers have gone to create. Measuring an organism’s microclimatic conditions thus mandates that we first have an Wind speed, air temperature, humidity, and solar radiation can influence . shoot activation – features likely to create a favorable canopy microclimate. . () performed GWAS using three methods of single-marker regression. be a great idea). Now try to list other factors that will affect local weather conditions ​Form groups of three people and do the following: Give each person.

First, let’s define microclimate. As the name suggests, it is the climate of a small area that usually differs from the surrounding region. (1) One thing that can. Topography, large bodies of water and urban areas are three things that can create microclimates on a large scale. Small-scale microclimates are created by. A microclimate is a local atmospheric zone where the climate is different from the surrounding area. They exist, for example, near bodies of water which cool the local atmosphere, or in heavily urban areas where brick, concrete, and asphalt absorb the sun’s energy, heat up, and.

The good news is that once you understand how different factors affect microclimates, you can modify those factors through your design to create, change and. A microclimate is a local set of atmospheric conditions that differ from those in the surrounding Microclimates can be used to the advantage of gardeners who carefully choose and position their plants. In an urban area, tall buildings create their own microclimate, both by overshadowing large areas and by channeling. (15 points) A. What are three things that can create microclimates? (3 points) brick, concrete, and asphalt B. What characteristics of these things help create a.

Microclimatic conditions depend on such factors as temperature, humidity, An undulating landscape can also produce microclimatic variety through the air. Its humidity may differ; water may have accumulated there making things Within a few centimeters of the surface, the temperatures during the day can be. The term may refer to areas as small as a few square meters or square feet (for example a garden bed) or as large Microclimates can be found in most places. . What are the three microclimates and their characteristics? Views · How do humans create microclimates, and what benefits does it bring?.

A microclimate is a smaller area within a general climate zone that has its own are north-facing, and this can create entirely different landscapes as a result. Are there areas of your yard that may be creating microclimates? these two factors can show you how to make a microclimate work in your. Water, mass and windblocks are three things that can create microclimates. A pond or a rock pile can store heat and release it when the air.

Making Microclimates

Sophie Thomson

SOPHIE THOMSON: Have you ever walked around your garden and wondered why some plants are thriving and yet others are struggling to survive. It’s because your garden isn’t a uniform space. It’s made up of a series of garden rooms, each with their own growing conditions. Some areas are hot and dry while others are cool and shady. And these different growing conditions are called microclimates.

If you want to create a successful and sustainable garden it’s really important you understand the different microclimates within your garden. To do this, you simply do a site analysis, whether you’re upgrading an existing garden or establishing a new garden.

The three factors to consider are temperature, sunlight and air circulation and all you need to do is just think about what the hot spots in your garden are. Think about where the shadows fall. They may be cast by a tree or the house and they may change from winter to summer. And also think about the air circulation and where the prevailing winds come from. All these factors affect how plants grow and understanding them will help you to create a stunning garden.

In this garden, the owner has identified the different microclimates and either worked with them, or changed them to suit her needs. The result is a garden that’s fantastic to live in. It’s one where there are entertaining areas, areas to sit and relax and it’s also a garden where the plants are happy and healthy.

This area of the garden is on the north-western side and in Adelaide, typically, this would bake in summer. However the large trees on the western side, actually cast some late afternoon shade and that helps to cool the garden off. This small area of lawn has a similar effect. If this was a hard surface such as paving or concrete, it would act as a heat bank and radiate heat onto the house. So a small area of lawn is a much cooler alternative.

Around this entertaining area, we’ve got some deciduous trees. These are ornamental pears. As they grow, they’ll form a canopy above us and being deciduous, they let the winter sun through and create cooling shade in summer.

In this corner of the garden, the perimeter is planted with trees and shrubs creating shelter from hot north winds and the little bit of wind that manages to get through gets cooled off over this water feature and blows cool air into the garden. So, with the use of shade, lawn, shelter and a water feature, the growing conditions in this part of the garden have actually been changed. And that’s something that you can do in your own garden.

One of the areas of this garden that’s really struggling is this northern side next to the pool. It’s open to hot north winds in summer, we get reflected heat off the building and the plants just bake. There was an area of lawn here, but it really struggled, so what I’m going to do is turn it into a garden bed and include a small to medium sized tree to create shade and it’s going to end up looking great.

This soil is ok but I’m going to add some compost. Adding this extra organic matter to the soil, turns it into a sponge which increases its water holding capacity.

I’ve chosen a Natchez Crepe Myrtle because they flower for 60 to a hundred days mid summer and produce a stunning display of white flowers. Crepe Myrtles love the heat and they come in a range of colours. They’re a perfect tree for a sunny, hot position.

The plants I’ve chosen are all really tough and waterwise and won’t need any supplementary watering once established. This is a plant from Mexico called Beschorneria yuccoides. The interesting grey foliage is upright and gives a great vertical accent to the bed.

These are simply cuttings of a Aeonium haworthii. All you do is you grab several together, bunch them like a posy and stick them into the ground. They’re so tough that they’ll root and look great in no time at all.

And finally, to finish it off, a groundcover of this stunning Gazania. It’s got the beautiful silvery foliage and bright yellow daisy flowers.

Until these Gazanias spread to cover the ground, I’m actually going to use this fine gravel mulch. What it will do, it will insulate the soil and it will also stop the dirt splashing onto the pavers.

Once all these plants establish, they’ll actually grow down onto the paving and soften the edge of the path. That will cut down on all the reflected heat and together with our beautiful tree, will actually help to change the microclimate in this area of the garden from one which is really harsh, to one which is a lot more favourable.

Creating a microclimate where it’s easier for plants to grow does take time, so start now and in a couple of years, your garden will be reaping the rewards.

STEPHEN RYAN: Planting a young tree from a pot is comparatively straightforward. But when it comes to advanced trees, things can get quite complicated. So here’s John to show us how it’s done.


MICROCLIMATES ARE climates of small areas, such as gardens, cities, lakes, valleys, and forests. A microclimate is an expression of the temperature, humidity, and wind within a few feet or meters of the ground. Such expressions exist because surfaces vary in their ability to absorb, store, or reflect the sun’s energy, making some areas warmer or colder, wetter or drier, or more or less prone to frosts. Microclimates may be natural or human made. They are important for their effects on comfort, crops, and natural surroundings.

Microclimates can extend for several miles because of the presence of large bodies of water, urban areas, and topography. Large bodies of water, such as the Great Lakes, Chesapeake Bay, and the ATLANTIC OCEAN ,moderate temperatures of adjacent inland areas. Such water bodies store huge amounts of heat during the summer and release it slowly in winter. Consequently, land areas near the water tend to have low temperatures in winter that are not as cold or prone to fall and spring frosts. Small lakes and bays have the same but less extreme effects. Urban areas also have microclimates. In winter, buildings, parking lots, and streets of cities absorb heat during the day, and then radiate it back into the air at night. Temperatures may be moderate enough to lengthen the growing season slightly in urban areas. In summer, the heating affect of concrete walls, metal and tile roofs, and asphalt parking lots can create sweltering temperatures. The excessive heat dries soils, wilts plants, and endangers the health of infants and the elderly. Topography also affects microclimates. In the Northern Hemisphere, south-facing slopes receive direct rays from the sun and are therefore warmer and drier than north-facing slopes. Additionally, cold air, which is heavier than warm air, tends to spill down mountain slopes and pool in valleys at night. Some valleys are 10 degrees F (18 degrees C) cooler than adjoining slopes on winter nights. Such valleys are at risk to frosts in late spring and early fall from the downslope drainage of cold air.

Microclimates can also be much smaller. The backyard has an assortment of possible small-scale microclimates. Surfaces of homes, balconies, rooftops, paved surfaces (such as patios, driveways, and sidewalks), lawns, trees, and soil types have subtle effects on the temperature, humidity, and motion of air. Like urban areas, a home absorbs heat during the day and radiates it back at night. Like mountain slopes, the side of a home facing the sun receives more solar energy and is warmer than the opposite side. Less cold-tolerant trees and shrubs are better suited to the side exposed to direct sunlight; hardier plants that are less prone to spring frosts can survive the cooler, shady side of the house. The eve of a smartly built roof hangs out over the windows just enough to shade the windows from the “high” sun of summer, but the overhang is not too far to block the “low” sun of winter. Fences, walls, and large rocks protect plants from wind and radiate heat. In winter, paved surfaces around the home absorb the day’s heat and reradiate it at night, moderating nocturnal temperatures. The same solid surfaces also absorb and reradiate heat to moderate winter temperatures and to raise summer temperatures.

Gardeners, architects, and farmers change the ground surface (such as by changing the reflectivity or heat transmission of the surface or by modifying surface roughness) to create microclimates. Human-made microclimates can be deliberate or unintentional, large or small in scale. For instance, a skillful gardener creates several small-scale microclimates in a single garden to assure a variety of attractive flowers, shrubs, and trees. The gardener knows that certain plants benefit from the coolness of shade trees; other plants require windbreaks for protection from desiccating winds; and plants that are frost sensitive do better near walls or large rocks that absorb and reradiate heat. Architects design landscapes, homes and office buildings to take advantage of sunlight, solar energy, wind direction, and water drainage.

Farmers utilize microclimates in similar ways in large fields; they select crops according to field exposure to sunlight and wind, as well as moisture retention capacity of the soil. Some of the largest changes that people make to microclimates are unintentional results of widespread suburbanization, forest clearance, and agricultural expansion. Alterations of microclimates will not affect the general climate of a region, but the change can and does result in large local changes in climatic conditions.

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What Causes Microclimates

Last Updated on Fri, 31 Jan 2020 | Vegetation

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Microclimates are caused by local differences in the amount of heat or water received or trapped near the surface. A microclimate may differ from its surroundings by receiving more energy, so it is a little warmer than its surroundings. On the other hand, if it is shaded it may be cooler on average, because it does not get the direct heating of the sun. Its humidity may differ; water may have accumulated there making things damper, or there may be less water so that it is drier. Also the wind speed may be different, affecting the temperature and humidity because wind tends to remove heat and water vapor. All these influences go into “making” the microclimate.

4.1.1 At the soil surface and below

Soil exposed to the sun heats up during the day and cools during the night. Within a few centimeters of the surface, the temperatures during the day can be extreme: 50 °C or more in a dry desert climate when there is no water to evaporate and cool the soil. Even high on mountains, exposed dark soil surfaces heated directly by the sun can reach 80 °C—hot enough to kill almost any lifeform.

At night a bare soil surface cools off rapidly and by morning it may end up more than 20 °C cooler than during the day. Yet, only 15 cm down the fluctuation between night and day is only about 5°C, because the day’s heat is slow to travel through soil. Thus, the soil at depth has its own quite separate climate: a microclimate distinct from that at the surface. Down at 30 cm there is essentially no difference between temperature of night and day because the soil is so well insulated from the surface; it stays at about the average temperature of all the days and nights combined over the last few weeks. At about 1 meter depth, there is no difference between temperatures in winter and summer—the soil remains right at the yearly average without fluctuation.

These differences are all-important to plant roots and the small animals and microbes that live within the soil. At depth, the extremes of heat or cold are much less and survival is often easier. But in high latitudes where the average annual temperature is too low, below —3°C, the soil at depth always remains frozen, for it is never reached by the heat of the summer. Water that once trickled down into the soil forms a deep layer of ice, known as permafrost, that may stay in place for many thousands of years. Where there is permafrost, roots cannot penetrate and plants must make do with rooting into the surface layer above which at least thaws during the summer. In the far north, patches of trees in the tundra seem to promote the formation of permafrost in the soil underneath themselves. The freezing of the soil eventually kills the roots, causing the trees to die and give way to tundra again. Permafrost forms under these tree patches because, in the shade cast by the leaves and branches, there is no direct heating of the ground by sunshine in the peak of summer. The frozen sub-surface of the soil never thaws out, and that equals permafrost. This is despite the fact that the covering of trees absorbs sunlight and heats up the air above the ground in the warmer months, and warms the local and regional climate overall (see Chapter 5). This extra warming does not reach into the ground, however; at least not strongly enough to compensate for the lack of the intense direct heating of the sun that would be found on open tundra soil in summer.

4.1.2 Above the surface: the boundary layer and wind speed

If we now go upwards from the soil surface into the air above, there is another succession of microclimates. When wind blows across bare soil or vegetation, there is always some friction with the surface that slows the wind down. This slowing down causes the air just above the soil to form a relatively still layer known as the boundary layer. Within a few millimeters of the soil surface, the friction is severe enough that the air is almost static (Figure 4.1). Air molecules are jammed against the surface, and the molecules above them are jammed against the air molecules below, and so on. Moving up a few centimeters or tens of centimeters above the surface, the dragging influence of friction progressively lessens as the “traffic jam” of air molecules gets less severe, and there is a noticeable increase in average wind speed because of this. In fact, what with the decreasing friction from plants, trees, buildings, etc. the average wind speed keeps on increasing with higher altitudes, until it really tears past a mountain top. It is no coincidence that the strongest wind gust ever recorded was at the top of a mountain (372km/hr at the summit of Mount Washington, USA). Even so, mountains are not always windy. Some days in the mountains will have hardly any breeze, when the weather favors calm conditions.

In a sense there is a succession of boundary layers, each on top of one another and with the air higher up moving faster. “Boundary layer” is really a relative term: it is a layer of slower moving air caused by being closer to a rough surface, below a faster moving one above that is less affected by the surface. The term “boundary layer” is used at many different scales in the field of climatology, and can be very confusing because different sub-disciplines each use the term in their own way at the scale they are most interested in.

The boundary layer fundamentally affects the heat balance at the surface and in the air above, up to the height of a few centimeters or a few meters. If sunlight is hitting the surface, being absorbed and heating the surface up, heat is being

(Wind speed increases with height from surface)

Figure 4.1. The boundary layer over a surface. Source: Author.

conducted gradually to the air above it. The relatively static air in the boundary layer will be able to heat up as it is close to the surface, and because it stays still and accumulates heat it will be quite a bit warmer than the mixed air in the wind above. As this boundary layer air is not being continually whisked away, the surface will not lose heat as fast either. In effect, the warmed boundary layer air acts like a blanket over the surface. The thicker the blanket, the warmer the surface can become. If the surface below the boundary layer air consists not of soil but of living leaves (as it does above a forest canopy, for instance), this extra warmth can be very important for their growth and survival. In a cold climate, there may be selection on the plants to maximize the thickness and the stillness of the boundary layer. In a hot climate, on the other hand, the plants may be selected to disperse the boundary layer, to prevent the leaves from overheating.

So, in a layer of still air the temperature can be several degrees higher than the mixed-in air just above it. This can make a lot of difference to the suitability of the local environment for particular plants and animals. For instance, in a tundra or high mountain environment, at the very edge of existence for plants, this small amount of shelter can determine whether plants can survive or not. On the upper parts of mountains, with strong winds and short grassy vegetation, a local boundary layer can make a big difference to the temperature the plants experience. If a spot is sheltered—for instance, between rocks or in a little hollow—the wind speed is also lower; there is a small space of static air with almost no wind movement. On a mountain slope in the mid or low latitudes, the intense sunlight can deliver a lot of energy directly to the surface. If the shelter of a hollow prevents this heat from escaping to the cold air above, it can become much warmer and types of plants that require more warmth are able to survive.

By making their own boundary layer climate, plants can turn it to their advantage. The upper limit to where trees can grow on a mountain—the tree-line—occurs below a critical temperature where the advantage shifts from trees towards shrubs or grasses. Trees themselves standing packed together create a layer of relatively still air amongst them that can trap heat, but there comes a limit up on a high mountain slope at which this heat-trapping effect is no longer quite enough for trees to form a dense canopy. In a looser canopy, much of the heat-trapping effect collapses and suddenly beyond this point the trees are left out in the cold. This effect helps to produce the sudden transition in vegetation that is often seen at a certain altitude up on many mountains.

Often, right above the treeline on a mountain, dense woody shrubs take over. It is thought that shrubs can thrive at mountain temperatures too cold for trees because they can create a strong boundary layer against the wind among their tightly packed branches. Wind cannot blow between the branches, so the sun’s direct heat is not carried away as fast, and their leaves can thrive in the warmer temperatures of the trapped air (Figure 4.2). Trees, by contrast, have a much looser growth form; so, if they are standing out on their own the wind can blow straight through their branches and carry away the sun’s heat. Shrubs—with their heat-trapping growth form—can keep their leaves as much as 19°C warmer than the trees, making all the difference between success and failure in the high mountains.

Figure 4.2. Shrubs trap more heat amongst their branches than trees do, because the wind cannot blow between the tightly packed branches of a shrub. Source: Author.

Higher even than shrubs can grow on a mountain is the “alpine” zone of cushion plants (Figure 4.3*). These exquisite little plants, from many different plant families in mountains around the world, form a little dense tussock of short stems and tiny leaves. Many of them look at first sight like cushions of moss, but they are flowering plants—often producing a flush of pretty flowers on their surface in the summer. The cushion plant growth form seems to be adapted to a version of the same trick that mountain shrubs use. A cushion plant, which needs all the heat it can get, creates a miniature zone of static air in the small gaps down between its tightly packed leaves. Leaves within the tussock are heated directly by the sun, and because the wind cannot blow between them everything within the tussock stays warmer. The plant is able to photosynthesize, grow and reproduce in an extreme environment by creating its own miniature boundary layer and microclimate amongst the leaves. Measurements show that on sunny days in the mountains, the leaf temperature of these cushion plants is often 10 to 20°C higher than the air immediately above. One reason why such alpine cushion plants are difficult to grow in sunny, warm lowland climates is that they are so good at trapping heat. They essentially fry themselves when ambient temperatures are already warm, raising their own leaf temperatures to levels that would also kill any lowland plant.

* See also color section.

Figure 4.3. An alpine cushion plant, Silene exscapa. The growth form of cushion plants maximizes trapping of heat in the cold high mountain environment. Source: Christian Koerner.

Many cushion plants use an additional trick to trap heat: above the dense cushion of leaves is a layer of hairs—transparent, and matted. These act like a little greenhouse, letting in sunlight and trapping warmed air underneath because it is not carried away by convection or by the breeze. This miniature greenhouse significantly increases the temperature of the leaves underneath, presumably resulting in more photosynthesis and better growth.

4.1.3 Roughness and turbulence

Although an uneven surface creates a boundary layer by slowing the air down, it can actually help set the air just above the boundary layer in motion by breaking up the smooth flow of the wind. The surface of a forest canopy, with lumpy tree crowns and gaps between them (Figure 4.4*), can send rolling eddies high up into the air above. This turbulent zone created by the canopy often reaches up to several times the height of the trees themselves. A more miniature turbulent layer will also be created above scrub vegetation when the wind blows across open ground between the bushes and then jams against their leaves and branches. Generally, whatever the height of the biggest plants in the ecosystem, the rolling turbulence that they create will extend for at least twice their own height into the atmosphere above.

Figure 4.4. The lumpy, uneven tree crowns of tropical forest create turbulence in the air that flows over them, Perak, Malaysia. Source: Author.

The turbulent microclimate created by air blowing over uneven vegetation surfaces also helps to propel heat and moisture higher up into the atmosphere, altering the temperature on the ground and feeding broader scale climate processes. In Chapters 5 and 6 we will see various case studies where changes in vegetation roughness seem to affect climate quite noticeably.

4.1.4 Microclimates of a forest canopy

The canopy and understory of a forest are like two different worlds, one hot and illuminated by blinding sunlight, the other dark, moist and cool. Parts of a large forest tree can extend all the way between these two worlds, and trees will often spend their early years in the deep shade before pushing up into the light above. Both the canopy and the understory microclimates present their own distinct challenges, and the plants need adaptations to meet these.

It is remarkable how hot the surface of a temperate or tropical forest canopy can become on a sunny summer’s day, with leaf temperatures exceeding 45°C. In tropical rainforests, although it is cloudy and humid much of the time, a few sunny hours are enough to dry out the air at the top of the canopy and really bake the leaves.

It is critical that a leaf exposed to strong sunlight keeps itself cool enough to avoid being killed by heat. A leaf can lose heat very effectively by evaporating water brought up by the tree from its roots; the heat is taken up into the latent heat of evaporation, vanishing into water vapor in the surrounding air—it is the same principle by which sweating cools the human body. Evaporation from the leaves occurs mostly through tiny pores known as stomata, which are also used to let CO2 into the leaf for photosynthesis (see Chapter 8). When the evaporation occurs through these stomata, ecologists call it “transpiration”. As we shall see in the later chapters of this book, both the heat uptake and the supply of water to the atmosphere by transpiration are also important in shaping the regional and global climate.

Slowing down heat loss by transpiration presents a dilemma for the plant. On one hand, if its stomata are open and it is transpiring, a leaf can keep cool. However, keeping cool in this way gets through a lot of water. If the leaves “spend” too much water, there is a risk that eventually the whole tree will die of drought because its roots cannot keep up with the rate of loss. Even if there is plenty of water around the tree’s roots, the afternoon sun can evaporate it from leaves faster than the tree can supply it through its network of vessels. If water is indeed limiting, the leaves will shut their stomata to conserve it. Tropical forest leaves in sun-lit microclimates also have a thick waxy layer, to help cut down on evaporation when water is in short supply.

If leaves close their stomatal pores and swelter, they risk being damaged by heat. It is thought that certain chemicals which are naturally present in leaves, such as isoprene, may help to protect their cells against heat damage in situations where they cannot evaporate enough water to keep cool. A breeze over the forest canopy will always help the leaves to lose heat even without any transpiration going on, and the faster the wind blows the better the leaves will be able to cool. The size and shape of leaves can also be important in avoiding heat damage. A big leaf is at all the more risk of overheating than a small leaf, because it creates a wider, thicker boundary layer that resists the cooling effect of the breeze. These sorts of problems are thought to limit the size that leaves of canopy trees can reach without suffering too much water loss or heat damage. The only exceptions are big-leaved tropical “weed trees” such as Macaranga, that can have leaves 50 cm across. They seem to keep themselves cool by sucking up and transpiring water at a high rate. Perhaps because of the risks of overheating, in temperate trees the “sun leaves” (see below) exposed at the top of the canopy tend to be smaller than the “shade leaves” hidden down below, even on the same tree.

The most intense aridity in the forest is likely to be felt by smaller plants that grow perched on the branches of the big trees: the epiphytes. In tropical and temperate forests where there is high rainfall and high humidity year-round, these plants are able to establish themselves and grow even without any soil to provide a regular water supply. But, because they are isolated from the ground below, and only rooting into a small pocket of debris accumulated on the branches, epiphytes are at the mercy of minor interruptions in the supply of water from above. When it has not rained for a while, epiphytes up in the canopy can only sit tight, either tolerating dehydration of their leaves or holding in water by preventing evaporation from their

Figure 4.5. The eery gloom of tropical montane forest shrouded by cloud. Cloud water condensing on the leaves constantly drips down from the canopy, watering the trees. Photo: Genting Highlands, Malaysia. Source: Yang Ren Kit.

waxy leaves. Some epiphytes live rather like cacti within the rainforest, having thick fleshy leaves that store water for times of drought. One very important group of epiphytes in the American tropics, the bromeliads, tends to accumulate a pool of rainwater in the center of a rosette of leaves. They are thought to be able to draw upon this water reserve to keep themselves alive when it has not rained for a while. Other bromeliads are able to tolerate drying out and then revive and photosynthesize each time it rains. One well-known example is Spanish moss (Tillandsia) which festoons trees in the Deep South of the USA.

Sometimes trees can in effect water themselves. High up on many tropical mountains, around 2,000 m above sea level, are “cloud forests” which thrive in the layer where clouds tend to hit the mountain slopes (Figure 4.5*). The cloud droplets condense on leaves in the forest canopy and drip to the ground. Walking under the trees when clouds shroud the mountain, cold water condensed from the fog continuously drips onto the back of one’s neck. Often this contributes 30% or more of the water that reaches the trees’ roots. Similarly, in northern California where coastal fogs constantly roll in off the sea, the water captured from fog droplets plays an important part in the survival of the giant redwoods (Sequoia sempervirens).

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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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Exploring a missed opportunity: Microclimates

They go largely unobserved and unattended. In view of the climate change that is with us today, this is a huge missed opportunity: microclimates.

As long ago as 1949, Wolfe, Wareham and Scofield, in a meticulous description of the microclimate in the small Neotoma valley in Central Ohio, observed there is much attention for predictions and trends of macroclimate, but far less understanding of how this translates in weather at a local level.

Agricultural systems in the Amhara region of Ethiopia affect microclimates. Photo: Abby Waldorf

The same holds true today. Climate science has a large interest in ‘average weather’. There is an obsession with predicting larger climate trends: regional long-term patterns of rainfall, temperature peaks and averages. How this pans out locally in time and space in less understood.

What is a microclimate?

Microclimates are the wonderful local interplays between factors such as soil temperature, air temperature, wind directions, soil moisture and air humidity – affected by day-night effects and seasonal effects.

They are determined by the particular landscape, soil conditions, vegetation and land use and water retention. Basically they are where meteorology lands on earth and where a dynamic interaction of forces – local heat exchanges, capillary rise over seasons, moisture retention – determine, the moisture available to the different ecosystems, the presence of dew and frost, the actual temperatures for plant growth, the vigour of soil biotic life and capacity to fixate nitrogen and the occurrence of pests and diseases.

Microclimate interactions (click to enlarge). Source: MetaMeta

The effect of microclimates may either buffer against climate change or may amplify its effects, be it temperature peaks, droughts, irregular or late rainfall. See the mosaic of interactions on the right.

What is more is that microclimates can be influenced and managed. There are several interventions that can affect the microclimate and hence the ability of an area to cope with and even make beneficial use of the larger climate change.

How are microclimates managed?

The first important intervention is to improve water retention at a landscape level by water harvesting, by water spreading and by erosion and drainage control. This increases the soil moisture available in a landscape. When there is more moisture in a landscape it will even out temperature peaks and lows, both in the air and the soil at different depths. It will have an effect on dew formation and the risk of night frost. Moreover secure soil moisture is a big boost to the ability of soil bacteria to fixate nitrogen and add to the overall fertility of the landscape.

Another intervention is regreening. Vegetation affects how much heat is absorbed in an area and how much is radiated. It affects the circulation of air temperature at different layers and the speed and direction of winds and the movement of dust particles among others. Vegetation canopy can retain moisture. The presence of small forests in an open landscape can create local winds.

A good example is the Tigray and Amhara regions in Ethiopia, where intense development of the landscape caused much change: shallow groundwater tables have come up, moisture has been secured and vegetation boosted – all these having a tremendous impact on the local climate. Agricultural productivity rose not only as an effect of secured moisture but probably also as an effect of gentler microclimates and higher soil nitrogen availability.

Microclimates at a landscape level

Understanding the microclimate is an essential part of managing an ecosystem. It is also a call for intensive change – instead of isolated interventions, managing microclimates rests on a critical sum of measures that creates a systematic change of microclimates at landscape level.

Moreover, there are different conceivable strategies in intensive watershed management and regreening – the method of water harvesting practiced (run-off storage or water spreading) or the type of vegetation promoted – all having a different impact on the microclimate.

The management of microclimate is a powerful frontier, but not well understood, to smoothen out the impacts of climate change and at the same time create more resilience through more stable agricultural ecosystems.

We are reviewing microclimates in a project entitled ‘Harnessing Flood for Better Livelihoods and Ecosystem Services’. As part of the review, we are exploring questions such as: does the capture of run-off in different parts of the landscape – upstream, midstream or downstream – have an effect on the microclimate? If so, where is the largest impact? Also, can we optimize it and make better use of it?

For instance different ways of capturing and spreading run-off may effect the distribution of soil moisture differently with knock-on effects on soil temperature or on capillary rise. At this stage the challenge is to come to grips with the forgotten factor: the microclimate.

The next step is to position microclimate versus macroclimate change, as was done in Neotoma. The question is: can better management of the microclimate ward off the threats of larger climate change? Or even better – make smarter use of climate change as it comes?

Ecosystem services (including microclimates) in relation to the managed distribution of floodwater and run-off is investigated under the CGIAR Research Program on Water, Land and Ecosystems’ project, Harnessing Floods for Enhanced Livelihoods and Ecosystems Services.

Which of the following would be an example of a microclimate?

appearance of a fine haze in a painting, which creates greater warmth around the figures and gives the scene a more dream-like appearance. c. Done in ink on paper by Leonardo da Vinci, the drawing shows the human figure combined with geometry. d. Known as El Greco, he was one Mannerist artist who was known for dark, gloomy paintings that often featured figures so elongated and out of proportion that they almost seem to have been tortured into their shapes 2. Match the vocabulary word to the correct definition. 1. The Last Supper 2. Michelangelo 3. Master of Flemalle 4. Mannerism a. Often viewed by the public as having a touch of the divine, as evidenced by his nickname Il Divino; regarded as one of the greatest artists of all time. He created the famous David statue. b. Believed to have been the painter Robert Campin by most art scholars today. He gave us one of the first paintings to include a sense of perspective and space. c. Western period of art from around 1520 to 1600; it followed theHigh Renaissance period. d. One of the first pieces to give us the classic High Renaissance style.The painting shows Jesus with his twelve disciples at the dinner shortly before his crucifixion.

Microclimate Data Prolongs the Summer

A nice outdoor climate is as important as good indoor climate. Even though the weather has its own mind, architects are actually able to influence outdoor conditions significantly by design.

Designing with the local microclimatic conditions in mind, such as windflow, sun, and shadow, architects can minimize the uncomfortable and optimize the comfortable aspects of the local climate – and thus increase the amount of comfortable outdoor hours significantly.

“We all know that one secret spot in the park, the courtyard or in the playground, where the sun always shines and there is shelter and a comfortable temperature. Through our analysis, the variance of the microclimate is actively implemented in the shaping of the building, improving the experienced weather altogether,” says Lead Engineer at Henning Larsen, Jakob Strømann-Andersen.

Five extra weeks

For one, the construction of the building has been made to block out cold windflows and push them upwards along the building. The wind is guided according to the orientation of the towers and the way they gradually rise upwards. This ensures shelter from the wind in the open square as well as on the various rooftop terraces. Furthermore, the building is orientated in order to ensure that both the square and all the terraces are exposed to sunshine all day, while the towers also give shade to each other in the best suitable way.

“In Toronto, winters are viciously cold and the summers very warm. By analyzing weather data from all seasons, we have adapted the building to extend the comfortable outdoor season in the area by at least five weeks, for example by minimizing the chill factor during the spring and fall. The experienced temperature will simply increase,” says Jakob Strømann-Andersen.

“By optimizing these conditions, we ensure a public space that is livelier, more dynamic, and that invites more interaction between people and the place. One example of this is the annual local farmer’s market. When it takes place in the Fall in front of the civic centre, visitors will experience the weather conditions as more comfortable,” he states.

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