Thursday, December 27, 2018

Free Mini-class: Microclimates

with Klaudia von Gool

Excerpted from our double certificate design course.

Climate will vary more locally through human structures, topography, altitude, vegetation and water masses. This is called microclimate. By observing and analysing our microclimate we can design strategies to modify it.

Let's look at some of these factors in more detail.

Topography is the shape of the landscape and includes aspect and slope. Hills, mountains and valleys affect how wind moves through a landscape, as the wind moves around hills, speeds up near the top of hills, and funnels through valleys.

Aspect, the direction land faces, affects the amount of sunlight on a site. For example, a south facing site in the Northern Hemisphere will be a sunny site and can produce more biomass/vegetation.

Slope, the gradient or steepness in the land, will affect wind speed; this increases towards the top of a slope. Turbulence will be experienced just past the top of a slope. This is important information when situating wind turbines, as they work more efficiently without turbulence.

Cold air will sink and move down the slope. Accordingly, the slope will impact thermal zones, and a cold sink may occur just above structures or vegetation lower down the slope or in slightly depressed areas. In colder areas this can create a frost pocket.

Altitude. Temperature decreases with higher altitudes. We also find higher wind speeds and more moisture, because of rain or other precipitation at higher altitudes.

Studying existing vegetation can give us clues to rainfall, wind strength and direction and soil fertility. A way to discover the prevailing wind in our local landscape is by observing trees.

​This picture shows how the wind has shaped the trees, restricting growth on the side that the wind blows from, so that there's more growth on the other side.
Picture of a tree affected by the wind
As well as trees being affected by wind, trees themselves can also affect the wind in the landscape and other microclimate factors. For example, in temperate climates it is cooler and less windy in a forest while it's hot outside of it, as trees provide shade and a more moist microclimate and act as a windbreak. At night it stays warmer in a forest compared to out in the open, as the trees create shade from the wind and trap warmth. This does depend on the season and vegetation/leaf cover.

On a larger scale trees contribute to the creation of rain through evapotranspiration.

Structures.

Urban environments create warmer microclimates through the "heat island effect," as concrete absorbs more heat than the surrounding countryside. In general it is warmer in the centre of a city.
The hard surface of buildings, roads and straight lines of streets also create a wind tunnel effect, where wind speeds up. Tall buildings can create wind turbulence. Buildings can create a rain shadow, so there is a drier and a wetter side.

Microclimate and niche.

​Microclimates are directly connected to ecological niches, where organisms occupy a space where they can thrive optimally. Creating, or being aware of having, a variety of microclimates, means you can have a wide variety of niches for more diverse planting, keeping animals, and thus increasing yields.
An illustrated picture of microclimates in a yard.
We can make modifications to a microclimate to reduce and direct wind flow, as wind has a growth limiting effect on vegetation. On a windy site, planting windbreaks and shelterbelts is one of the earliest modifications needed. These create more sheltered areas and can direct the flow of air, including cold air coming downhill. Using plants to reduce wind is more effective than solid structures, which create more turbulence. In addition, we can choose species for multiple functions, which again creates more yields.

We can modify our local climate or microclimate by adding water storage, which can modify temperature fluctuations. On a larger scale, we can introduce lakes or ponds to modify heat and to add light reflection. On a smaller scale, adding water storage inside a greenhouse or polytunnel will help buffer extremes of temperature.

In hot climates, planting trees and adding vegetation gives a cooling effect. This is as a result of shade and evaporation, which creates cooling.

​We can modify climate and microclimate through buildings, like adding a greenhouse. When we place a dwelling to the North of a greenhouse (in the Northern Hemisphere) we can make use of surplus heat and protect plants. We can paint walls white in darker, shadier areas to direct in more light and improve growth and ripening by reflecting light. Dark walls reduce frost risk by keeping warmer.  
Picture of an enclosed yard making a microclimate.
We can use thermal mass like rocks or stone walls to absorb heat and plant more tender plants close up to it. We can also use the cooler temperature of the Earth, whilst it’s warmer at the surface, to create a root cellar for food storage into the Earth, without energy based refrigeration.

In cooler climates, you can create sun traps. These designs are sun-facing and wind-still, creating shelter from cold and destructive winds by capturing maximum sunlight all day. In the Victorian era in the UK, walled gardens were built on large estates to create microclimates for tender crops. Fruit trees were trained up against the walls in fan or espalier shapes.

​Hot beds are created by placing small glass frames on top of piles of manure, which generated heat as they rotted down. This is a form of season extension.
Start making some notations on a basic sketch map of your design area. Notice how microclimates work with both intentional and unintentional design. Note other microclimate factors: buildings/structures, landform, altitude, aspect, slope, larger vegetation; sketch these onto your map.
Make a very basic notation of the microclimates with colours or symbols.

Note areas that are driest, wetter, windiest, most wind-sheltered, where it might be warmest in the morning and evening, and anywhere that would be cool all day.

What different needs and opportunities are associated with these microclimates?
Picture of a greenhouse microclimate.
**

This miniclass is excerpted from the Climates, Biogeography and Microclimates module of our double-certificate design course, taught by Klaudia von Gool.

Klaudia draws on over 20 years experience and study to express her lifelong passion for the environment through facilitating people care and social design programs across the UK, Europe and the Middle East.  She’s an Environmental Scientist, Consultant, Parent, Mentor, Coach, Permaculture Teacher and Designer and student of healthy intact cultures and indigenous wisdom. Using her many practical and ceremonial skills, her work focuses across land-based, community and inner sustainability in order to fully activate the human potential in service of life, culture repair and rebuilding the village.

​Further information on this topic:


Cloud catchers. In an arid climate in Peru the people are harvesting fog for water as a low tech method of irrigating crops.

Regenerative Agriculture, Beyond Sustainability.
An inspiring film about regenerative agriculture. For the microclimate relevant part, watch from 12:35 to see the story of one farm, known as 'Dry Lands', that was destroyed by its previous owner. When the new owner replanted, he found that slowly the temperature on the land dropped, the climate changed, soil 'grew' as he added organic matter from vigorous pruning, water was retained, drought conditions were reversed and water started to run in the streams year-round.

#microclimates #ecologicalniches #freepermaculture #permaculturedesign #permaculturewomen
Via Permaculture Women's Guild - free permaculture http://bit.ly/2EQvR2k