Why so Few Tree Species in Quebec?

The total forested area on Earth is 4.06 billion hectares. 90 million of those hectares, of which 92% are publicly owned, are in a province of Canada called Quebec. It’s a vast area of trees, twice the total area that’s within Sweden’s borders. 1 out of every 45 hectares of the world’s forests are in Quebec, and yet of the ~100 000 species of trees on our planet, only about 50, or 1 in 2000 are native to Quebec. Why is there so little diversity of trees in this province?

According to a recent analysis, climate is the most important factor in determining tree diversity, and the highest number of tree species can be found in the hot, humid tropics. Why? Possibilities include a 365-day growing season which allows ample time to reproduce and recombine genes; higher mutation rates from UV and more isolated niches are my guesses. At latitudes between 45 N and and 63N, there is nothing remotely tropical about Quebec. Its lower latitudes accommodate temperate forests, but north of that is a large area featuring even longer and colder winters. These northern latitudes have the bulk of Quebec’s woodlands: the boreal forest. It is a flat area where genes don’t get isolated easily; the growing seasons are short and speciation of trees suffers. Dominating a vast forest are only five main species. Which one gets the edge partly depends on whether or not the soil retains water: white spruce is found mainly on well-drained upland; black spruce is in the damp lowlands. There is also balsam fir, jack pine and the American larch.

The bulk of Quebec’s forests are of the boreal variety, as is the case throughout the horseshoe-shaped, 2.5-to-4.2- billion-year-old Canadian Shield. (From https://www.the-forest-time.com/en/guides-des-pays-et-regions)

But why do its temperate forests only feature about 40 native deciduous species? The area that is currently temperate was completely covered by ice sheets during ice ages. During periods of glaciation, trees can survive but only in valleys. These are isolated from one another, reducing genetic drift between trees of different valleys, facilitating the formation of different species. But in Quebec, the few mountains existing in the south are too eroded and too low in elevation to block off advancing ice and to shelter the valleys.

Given that we tend to be attached mostly to the trees we grew up with, and since in Quebec’s case, the lack of tree-biodiversity is perfectly natural, I am comforted by the fact that all of its native species are familiar to me.

The genera that have the most Quebec-native species are Acer(maple) with 6; Populus (poplar) with 5; Betula (birch) with 4 and Quercus(oak) with 4. But among the eight genera that have only one lonely representative in Quebec, Rhus typhina, the staghorn sumac is one of my favorites. Elsewhere in the world, there are 200 different species of Rhus ! The staghorn reproduces both sexually and asexually by spreading seeds and rhizomes , respectively. The latter create clones, with older shoots in the middle and younger ones around the mother plant. It’s why sumacs proliferate so easily among the cleared area under hydro towers where they often coexist with wild grapes. It’s only in recent years that I realized that both wild grapes and sumac fruits are edible, although it’s best to use them to make a sweetened drink (red sumac berries) and jam (wild grapes). Sumac belongs to the Anacardiaceae family, which includes interesting warm-climate trees such as the mango (a south Asian native), cashew (of Brazilian origin) and pistachios, originally from Iran.

Staghorn sumac in the autumn.

Advertisement

Covid-19 and the Loss of Smell

In a little more than half of people infected with COVID-19 on the 1st stage of the epidemic, the sense of smell is compromised. Compared to people with other respiratory issues, those who test positive for COVID-19 are 27 times more likely to have smell-loss while being only 2.2 to 2.6 times more likely to have fever, cough or respiratory difficulty. According to a report from the Harvard Medical School, SARS-CoV-2 does not directly infect olfactory neurons but may instead interfere with brain function by affecting vascular cells in the nervous system. The hypothesis hasn’t been verified, but given that most COVID-19 positive patients regain their sense of smell within 8 weeks, it suggests that nerve cells themselves aren’t damaged.

Two weeks ago my wife and I started experiencing mild symptoms: congestion, slight cough, and a fever that was gone within 36 hours. Our autistic son who often takes off his mask had been asking for his salbutamol inhaler a few days earlier. A couple of days after our symptoms surfaced ( Wednesday and Thursday) we all tested positive for COVID-19. But my wife and I only lost our sense of smell 5 days after the appearance of other symptoms.

I had tested my sense of smell using a jar of oregano. Each morning, for each of us, the smell seemed to get a little fainter until Monday March 15 (see graphic), when it totally disappeared. When oregano’s volatiles failed to excite our olfactory receptors that morning, it was then that we noticed that we were not smelling coffee, apples, tomato sauce, almond oil, nasal rub, eau de toilette, compost or any of the usual bathroom stenches. The next morning we also tested our ability to smell vanilla, peppermint, and lemon extract. Anosmia had undoubtedly kicked in.

This persisted until Friday. On that day there was faint smell for each of the three extracts and for oregano, and even coffee grounds led to a very faint stimulus. This condition is called hyposmia. There was little change until one of us observed some improvements on the morning of Tuesday, 8 days after the onset of anosmia. Encouragingly, for me, oregano’s smell was more intense and so was that of the other three. Coffee’s smell was still weak, and those of apples and other fruits were still totally absent.

On Thursday, 10 days after the onset of anosmia, although there was no response from rubbing my fingers on oleander and bringing them to my nose, but that did not apply when I did the same thing with a plant of lemon thyme. There was a faint aroma. Similarly whereas in the previous week I had not been able to smell broth, after leaving the house for half an hour, upon reentering there was an olfactory response, but it smelled like a less complex mixture than it really was. Meanwhile on the same day, the lemon, vanilla and peppermints extracts all seemed stronger, and the same was true when I stuck my nose into the 250 ml oregano jar.

Rather than tediously continue with prose, I recorded the rest of the observations in the following table. Initially I was apprehensive, given that there’s no guarantee that the sense would come back unblemished. The sense of smell alerts us to dangers, strongly evokes distant memories, makes eating far more pleasurable, puts us in tune with nature and plays an underappreciated role in romance. Unlike hearing and vision which depend on waves, smell involves a direct interaction with matter. I was relieved when the sense started to function again and fascinated by the way different smells were restored at different rates. Oddly, except for the smell of tomato sauce, the last smells to come back were mostly unpleasant ones.

A daily log of how my sense of smell gradually became more functional. Most smells returned within a month, but oddly hyposmia persisted mostly for unpleasant smells for at least 4 more weeks.

A Greek study published in January 2021 in the Journal of Clinical Medicine, most of the 182 patients (88%) recovered their sense of smell by two months, confirming the findings of last year’s studies. MRIs have been conducted in other patients for those who have recovered and for those less fortunate. In the latter case, the olfactory bulb has been not only inflamed but damaged.

Does this imply that anosmia for such patients is permanent? Olfaction without apparent bulbs is seen in 0.6% of women, but not in men. Somehow part of the cortex compensates for the bulb’s absence. Whether this corrective measure can only happen soon after birth and not necessarily after COVID remains to be seen.

Postscript

As shown above, in keeping track of my sense of smell’s recovery, I exposed my nose to a variety of smells almost on a daily basis. Inadvertently I imposed upon myself a form of “smell training therapy” , an approach that is effective in helping patients recover from COVID19 smell loss. We’ve often encountered how self-reporting can introduce a bias in medical studies. Here there was an experimental component to the tracking itself, which could have artificially accelerated my recovery.

If you are familiar with BBC’s Crowd Science, this week’s episode covered COVID19 smell loss.

Almost a year after my infection and I report that the smells that were faint on Day 48 of the anosmia (tomato, coffee in cup(not the beans) and bleach are still faint. In addition I was throughout my life revolted by the smell of goat cheese and parmesan, but now the fainter smell is tolerable.

18 months later, last week, I finally smelled tomato sauce for the 1st time. I continued to gain sensitivity to parmesan to the point that it’s revolting again. It’s possible that pre-CoVID, I was hypersensitive to parmesan’s smell. Then until recently, I was smelling it like most people who enjoy eating the cheese. For a long time I had been associating my aversion to the smell to a bad experience with a parmesan meal from my childhood. But recent observations suggest otherwise. The reaction was more physiologically based, reinforcing what scientists know: there is a minority of smells which are not perceived the same way by different people due to the variability of nasal receptors.