Identifying your current microclimates – but first: The macroclimate
To be able to identify the microclimates present on your small part of the world, you will need to have some understanding of the macroclimate which exists in your area because that is the context within which your microclimate(s) will exist. That is to say –
- What are your temperatures throughout summer and winter?
- When is the first and last frost? (If indeed you get frosts at all!)
- How much rainfall do you get what is its distribution throughout the year?
- How hard do the winds blow and from which direction?
- How many sunny/cloudy days do get over the course of a year?
- How does humidity vary throughout the year?
If you have lived in your area for any length of time you will have some idea of the answers to a few of these questions. We have been here a long time and I know that generally the cold winds come from the south, and hot winds come from the north and west.
There are a number of ways of finding this data out, but there are a couple of caveats –
1. The closer the measurements were taken to your part of the macroclimate the more likely they will be to reflect your experience of it and the more useful the data will be.
2. The term ‘climate change’ says it all. Things are changing so be circumspect when using old data or data that has been averaged over a long time period, it may not be as accurate for current conditions.
A good source of data in Australia is the Bureau of Meteorology (BoM). It is worth checking out how close a BoM monitoring station might be to your house. This link will take you to the BoM site where you can check out your place, and the closest meteorological site which can provide you data.
http://www.bom.gov.au/climate/data/index.shtml#mapoption
http://www.bom.gov.au/climate/data/stations/
There is also a website where people can share data from their own private weather station and that is accessible through the BoM here - http://www.bom.gov.au/wow-support/. Also, check with your neighbours to see if they are weather enthusiasts, or if they have friends that are. They might have an operational home weather station and record of weather data.
Of course, if you intend to get into this yourself, there are any number of companies who will be willing to sell you a home weather station of your own.
Identifying your microclimates
When we moved in, the microclimates available in our yards were few. Some areas close to the house affected by thermal mass, the southern side of the northern fence and the eastern side of the western fence and, of course, the house were providing some shade and that was about it. Where our house was built, and indeed the whole estate, was effectively clear felled so there was no existing vegetation to be worried about or of which we could take advantage. This would have been good, being able to start from scratch, but at that time I had no knowledge of gardening, let alone microclimates. So here, over forty years later, I have had lots of mistakes to learn from so you don’t have to make them!
No microclimates around here!
When you are carrying out your microclimate investigation, It is worth having a notebook to record your observations of any you discover and a digital camera is good to capture any interesting bits. A line drawing of the layout of your property, filled as you go or later based on the observations in the notebook is good to have so that you can put things all together and have a comprehensive map of what microclimates you have where, and how they might interact.
There are a few other bits of equipment which will help, too – one or two maximum/minimum thermometers, a sun sight (more about that here), a soil moisture meter, and if you are up for it, a small hand held anemometer.
sun sight
Temperature
The sun is the driver for both light and temperature, so will impact both these aspects of the microclimates present on the site.
A good way to start investigating for microclimates on your site is to just have a wander on hot days to detect cooler areas under trees or other foliage or otherwise shaded areas and take notes on what you find. Following up by placing a maximum/minimum thermometer in areas of interest, checking them daily and comparing the results with readings from the weather stations.
It is amazing the effects of trees on the air temperature. I was in a country town years ago and we were in the middle of a stand of trees in a park, I didn’t have any temperature measurement devices on me but I would bet that it was 5⁰C or cooler under the trees than out in the open. Also, while trees will have a cooling impact on microclimate by providing shade, the ground under the northern side of a tree will provide a sunny, sheltered microclimate and could be warmer than the surrounding area. So making notes about existing trees, their size, leaf cover and evergreen/deciduous status is worthwhile.
In colder weather, areas that are close to a thermal mass like a building or water tank and that are in a position where it is in the sun and/or sheltered from cold wind can result in warmer microclimates than the surrounding area. As well as providing slightly warmer temperatures due to the presence of a brick building, the northern eaves of a building can trap warm air and provide shelter from frost as well. Placing the max/min thermometers in these areas can provide confirmation and some idea of temperature differences.
The cardamom plant (Elettaria cardamomom) on the right (above) growing in the middles of the yard suffered leaf damage from a late winter cold snap, while the one on the left, close to the house and protected by banana plants growing nearby, suffered no damage at all. Photos taken at the same time.
Aspect or the direction the property faces has an impact on temperatures and light. It is probably the most critical non-alterable characteristic of the property as a whole. Here in the southern hemisphere a south facing yard may mean reduced direct sunlight and temperatures as a result which can limit options for growing food crops. Almost any aspect will allow some form of food production but the more favourable the aspect (ie closest to a north easterly aspect) the more productive the area can be.
To know how great the effect of aspect will have, it needs to be coupled with the slope of the land. A property with a southerly aspect but very little slope will generally be warmer than land sloping steeply to the south. Slope will also give an indication of drainage of water and cold air from high to low, and the steeper the slope the faster the drainage of both fluids. Thus microclimates at the bottom of the slope will tend to be damper in wet weather because that is where the rainfall will end up, and cooler in winter due to the accumulation of cold air/frost.
Light
To understand the effect of sunlight on your property (and this will also have an impact on temperature) it will require looking over your property with an eye to the type and amount of shade as well as the aspect and slope of your site (see ‘temperature’ above). Ponds can also have an impact, not only on temperature due to their thermal mass, but they can also reflect light, affecting light levels in a particular microclimate.
Of course, shade will vary throughout the year, being at its greatest area on the shortest day of the year and least on the longest day of the year, due to the variation of the angle of the sun. One way to go is to make a sketch of your property of the extent of the shade on the shortest and longest days, if you can wait long enough. There are aids which can help to work out how a given tree or object’s shade will impact your property, one is by building the above mentioned ‘Sun Sight’ which measures the angle the shade of a particular object makes with the sun for a given day of the year, showing in real time where the shade from that object will land on your yard. It can be used to do this for the shortest day, longest day and everything in between. There are also phone aps like the ‘Sunseeker’ which will assist in a similar way, although I have no direct experience with them.
Even a single large deciduous tree can have considerable influence on the local microclimate
It is also worth recording the quality of the shaded areas in your yard, is it complete shade with only indirect or oblique sun available like from a northern fence, or a dappled or incomplete shade as provided by trees or bushes, or even summer shade and winter sun as provided by removable shades or deciduous trees.
Air Circulation
It is important to understand which direction the main winds come from in your area, however the direction and force of these winds and the turbulence associated with them will be modified by your local environment, especially the urban and suburban environment. Again, a wander about on a windy day will give an insight onto where the windiest and calmest parts of your site are. For comparison, it can be handy to have quantitative data as well as qualitative data so a hand held anemometer can be useful, but vary in cost from a few tens to several hundreds of dollars. I suppose it comes back to how much of an issue wind is for your site.
Air circulation can also be thought of in terms of air drainage, with hot air rising up and cool air moving down the slope of the land as discussed above. Air drainage through a site can be very important, particularly in damp times where a moist or humid microclimate is also a still microclimate, this can favour fungi and cause losses in food crops that are sensitive to fungal problems. It is worth taking note if there are any areas of the site where this may become a problem. Frost drainage in winter is also an important consideration, particularly if you want to grow plants that are marginal in your area in terms of frost.
Water
Again, for me, there is no better way of understanding how water acts on your site than taking a stroll around during a rainy day. That way it is possible to see where the water pools and where it drains well, where water flows enter your site from the neighbours and where water drains from structures. Even without a home weather station, cheap rain gauges are available and easy to install so that you will know exactly how much rain is falling on your property as a whole.
Follow the water!
Once the rain has stopped, a soil moisture gauge can be invaluable in identifying where water accumulates and hangs around, even if there is no surface water. Another indicator is the types of plants growing, and plants such as moss and sedges are a good sign that the soil is continually damp.
Sedge
Moss
Part 1: What are Microclimates and why are they important?
