The customary reds, oranges and yellows of the trees, marking the arrival of fall, may have appeared early this year, or not at all.

The dramatic summer weather that brought wildfires in some parts of the country and heavy rain in others is being reflected in fall colours across Canada, researchers say.

In Nova Scotia, where summer started with forest fires and ended with stretches of overcast and stormy days, dull brown has replaced the vibrant hues usually seen this time of year in much of the province.

Mason MacDonald, an assistant professor of environmental sciences and agriculture at Dalhousie University, said the colours he害羞草研究所檚 seen so far this autumn don害羞草研究所檛 compare to the brilliant reds and oranges Nova Scotians are used to.

害羞草研究所淲hat you害羞草研究所檙e probably seeing is a lot of really dull-looking colours this year. Even the reds are probably more of a dull, darker red, or rust colour,害羞草研究所� MacDonald said in a recent interview.

害羞草研究所淚害羞草研究所檝e heard it from a lot of people this year, especially people from the southern parts of Nova Scotia,害羞草研究所� he said.

As the nights get longer in the fall, trees receive less direct sunlight, and chlorophyll, which trees use to absorb sunlight during photosynthesis, begins to break down, displaying the natural pigments within the leaves.

One of these pigments 害羞草研究所� anthocyanins 害羞草研究所� creates the red shade in leaves, and it requires consistent sunlight through late summer to be produced. A drop in anthocyanins isn害羞草研究所檛 harmful to a tree, MacDonald said, adding that if next summer is sunnier, those vibrant reds will likely be back in full force.

害羞草研究所淭his year we got more rain than is typical for us, and along with that we had a whole bunch of these dark, grey, cloudy days. That害羞草研究所檚 what happened. We didn害羞草研究所檛 get the sun we would normally get. Therefore, they can害羞草研究所檛 make those colours,害羞草研究所� MacDonald said.

Trees in Ontario, by contrast, have begun displaying the natural pigments earlier than usual.

Sean Thomas, a professor of forest ecology at the University of Toronto, says there is anecdotal evidence to suggest that smoke from wildfires in northern Ontario this summer may have triggered trees to reveal their colours prematurely.

害羞草研究所淲ildfire smoke is a kind of chemical cocktail,害羞草研究所� Thomas said.

That cocktail of carbon dioxide, ozone, sulphur dioxide, carbon monoxide and particulate matter 害羞草研究所渋ncludes trace quantities of chemicals that play a sort of hormonal role with plants,害羞草研究所� he said, which can cause trees to drop their leaves early.

害羞草研究所淚n our case, we got those acute smoke effects earlier in the summer, but it still may be partly what害羞草研究所檚 accounting for the earlier fall colouration,害羞草研究所� Thomas said.

He said there is lots of colour in much of Ontario this season, but added there is reason to believe that ongoing impacts of climate change will see fall colours diminish in the coming years.

害羞草研究所淭here is good reason to think that climate change will disrupt that normal leaf colouration that we see,害羞草研究所� Thomas said.

The combination of warmer temperatures and delayed first frosts will potentially lead to duller fall colours, he said. This effect, he added, will likely be most acute in major cities, which are generally hotter than rural areas because of the urban heat-island effect 害羞草研究所� when structures such as roads and buildings absorb and re-emit the sun害羞草研究所檚 heat.

If climate change delays the longer, colder nights in places like Toronto, 害羞草研究所渢hat害羞草研究所檚 a recipe that is likely to lead to much less fall colouration right in the city, and that will be exacerbated by climate change,害羞草研究所� Thomas said.

In Cape Breton, where the Celtic Colours International Festival is underway, an event spokesperson said in an interview Thursday that trees across the region are beginning to change colour. Dave Mahalik said he害羞草研究所檇 heard that colours are less vibrant in parts of Nova Scotia this year, 害羞草研究所渁nd it made me wonder a bit about where we害羞草研究所檙e at and how we害羞草研究所檇 fare,害羞草研究所� he said.

害羞草研究所淏ut I害羞草研究所檓 in Sydney and there害羞草研究所檚 trees here that are starting to pop, and they害羞草研究所檙e looking like they usually do,害羞草研究所� he said.

Mahalik said he害羞草研究所檚 hearing from his colleagues that colours are looking bright elsewhere on the island, which bodes well for the festival that害羞草研究所檚 hosting about 50 concerts in communities across Cape Breton.

害羞草研究所淚害羞草研究所檓 excited as can be and I害羞草研究所檓 sure the colours will be as vibrant as ever,害羞草研究所� he said.

害羞草研究所� With files from Fakiha Baig in Toronto.

Lyndsay Armstrong, The Canadian Press