{"id":28122,"date":"2024-06-07T07:55:01","date_gmt":"2024-06-07T07:55:01","guid":{"rendered":"https:\/\/www.walkhighlands.co.uk\/news\/?p=28122"},"modified":"2024-06-07T07:55:08","modified_gmt":"2024-06-07T07:55:08","slug":"scots-pine-the-sight-the-sound-and-the-smell","status":"publish","type":"post","link":"https:\/\/www.walkhighlands.co.uk\/news\/scots-pine-the-sight-the-sound-and-the-smell\/","title":{"rendered":"Scots pine: the sight, the sound and the smell"},"content":{"rendered":"
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\"Ben<\/figure>\n<\/div>\n\n\n

After a winter of relative dormancy while much of the natural world slumbers, our senses kick into high gear as the warmer months progress. The explosion of life and activity means there are many amazing sights, sounds and smells for us to take in. But while most species grab our attention via one or perhaps two of those senses, the scots pine manages to tantalise all three.<\/p>\n\n\n\n

The sight<\/strong><\/h3>\n\n\n\n

We all know what a splendid sight old scots pines are, with their scaly red bark and sprawling asymmetrical crowns, and we love them for it. Their gnarly, deep green beauty is justification alone for being chosen as Scotland\u2019s national tree in 2014. But that\u2019s not the sight I\u2019m talking about. No, I\u2019m talking about the sight of pale yellow dust. Pollen.<\/p>\n\n\n

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Pollen painting<\/em><\/figcaption><\/figure>\n<\/div>\n\n
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\u2018Chalking\u2019 the landscape<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

Its arrival is hard to miss, and typically manifests itself in three conspicuous ways.<\/p>\n\n\n\n

Firstly, after it\u2019s rained, many puddles have a gooey yellow film on the water\u2019s surface. On first glance it looks like oil, especially after the wind has pushed and spun the water around, painting the pollen into lines and swirls. Puddles become abstract works of art, and wouldn\u2019t look out of place in a Jackson Pollock exhibition.<\/p>\n\n\n\n

More usually though, long after those puddles have drained away, you\u2019re left with conspicuous yellow \u2018high tide\u2019 marks across the landscape. It\u2019s as though someone has taken a thick piece of chalk and drawn horizontal contour lines all over the place.<\/p>\n\n\n\n

Secondly, during a prolonged dry spell with no rain to wash particulates away, you\u2019ll find everything coated in a fine (and sometimes not-so-fine) dusting of pale yellow. It gets everywhere.<\/p>\n\n\n\n

And thirdly, when a dry spell coincides with gusty winds, you will see great big clouds of pollen wafting skyward above trees and forests. This can be rather stressful for anyone managing woodlands, and especially for anyone managing both visitors AND woodlands because it does, on first glance, look very much like smoke.<\/p>\n\n\n\n

In most Mays\/Junes at Mar Lodge Estate, as I\u2019ve been walking out of Glen Derry or Glen Dee on fire patrol, I\u2019ve caught sight of this \u2018smoke\u2019. My heart misses a beat and I can feel the adrenaline surging, a mixture of dread and action. It is with considerable relief, therefore, that I realise that it\u2019s pollen, not smoke, and the panic subsides.<\/p>\n\n\n

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False alarm! Pine pollen doing its best snoke impression in Glen Derry<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

Scots pine pollen comes from the male flowers. Yep, flowers! I\u2019m not sure how many of us have ever considered that pines have flowers in the conventional sense, but they do.<\/p>\n\n\n\n

Scots pine is a \u2018monoecious\u2019 species of tree. Meaning \u2018single house\u2019, moneocious refers to the fact that each individual specimen of the species has both male and female reproductive parts. It\u2019s commonplace in the tree world, and includes familiar trees like birch, alder, larch and oak.<\/p>\n\n\n\n

Some other plant species are \u2018dioecious\u2019 (\u2018two houses\u2019) where a given individual of the species has either male or female reproductive parts, but not both. Examples of dioecious trees are aspen, juniper and holly.<\/p>\n\n\n\n

Pollen is the medium through which plants fertilise other plants of the same species. The pollination process is the same for both monoecious and dioecious plants \u2013 pollen from the male reproductive parts needs to reach the female reproductive parts – it\u2019s just that a monoecious plant can pollinate itself and others, whereas a dioecious plant can only pollinate plants other than itself.<\/p>\n\n\n\n

There are advantages and disadvantages to both methods. Being able to reproduce without needing another individual of your species is advantageous if there are none nearby, however this isn\u2019t a great long-term strategy for species survival.<\/p>\n\n\n\n

Studies into the viability of scots pine seeds finds that while infertile seeds are present in all types of fertilisation (including dioecious cross-fertilisation with other individuals), they are much more likely when a pine has self-fertilised. So, while self-fertilisation is a handy back-up strategy in an emergency, it can also lead to long term decline without the input of fresh genetic material from other populations.<\/p>\n\n\n\n

Plants do have strategies to avoid self-fertilisation, however. And in the scots pine\u2019s case, the male and female flowers are generally kept some distance apart on different branches or on different areas of the tree.<\/p>\n\n\n\n

The male flower of the scots pine is called the microstrobilus, and it grows at the base of the new season\u2019s shoots. It is pale yellow and cone-like in shape, a few centimetres in height, and is essentially a catkin made of a number of flowers. Each flower has anthers, on which the pollen grains can be found.<\/p>\n\n\n

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Left: female flowers. Right: male flowers<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

These flower \u2018cones\u2019 are strikingly obvious this time of year, more so than the mature seed-bearing cones, as they dot the scots pines with pale yellow blobs (reddish brown later in the season) from top to bottom. There is, however, considerable variation from one tree to another. Some trees will be absolutely covered, while others won\u2019t have any at all.<\/p>\n\n\n\n

The female flower is called the megastrobilus, and it grows at the tips of the new season\u2019s shoots. It is smaller and less obvious than the male flower, and you need to look much closer to find it. It\u2019s a small, reddish-pink flower, and looks much like the more obvious purple flowers you might have seen on larch trees. This flower contains the ovules, which sit waiting for pollen from male flowers to reach them.<\/p>\n\n\n\n

Pollen is released by the tree all the time during flowering, but it\u2019s on those warm, dry and breezy days that it gets dispersed en-masse. You get a sense of how readily it leaves the male flowers if you simply tap one of them with your finger. You can see the pollen rising up, like a thin smoke.<\/p>\n\n\n\n

Scots pine pollen is large enough to see individual grains with the naked eye, but not so large that you can make out the finer details. When they land on a surface they look like tiny dots, but under magnification they are shaped more like fortune cookies. They have two air bags to help the grain get airborne. Actually, they look a bit like one of those Mickey Mouse hats.<\/p>\n\n\n\n

It\u2019s an incredible sight, therefore, when a gust of wind surges through a dense pine woodland and wafts the pollen aloft. Given how small the grains are, there\u2019s a mind-boggling amount of pollen in those clouds. One study from the early 20th<\/sup> Century reckoned that just one scots pine flower produces in the region of 150,000 pollen grains!<\/p>\n\n\n\n

Surprisingly, despite it seeming to be fall or waft everywhere, it appears that most scots pine pollen has a local, rather than a far-reaching impact.<\/p>\n\n\n\n

Scandinavian studies have found that scots pines there are mostly fertilised by pollen from close by. Nevertheless, when there\u2019s so much pollen, it\u2019s to be expected that some will be caught in winds and be transported a long distance. Hundreds of kilometres, in fact.<\/p>\n\n\n\n

This raises interesting questions about the ability of scots pines in one location to fertilise others many hundreds of kilometres away.<\/p>\n\n\n\n

Estimating the fertilisation rates in a patch of scots pines by non-local pollen is difficult, but 5-10% of pollen in a Swedish study of a scots pine plantation was thought to be non-local (several hundred kilometres distance) in origin. In a similar Spanish study, it was 5%.<\/p>\n\n\n\n

But is the pollen even viable after that distance? Well, a study in 1963 found that 75% of pollen that had travelled 70km across the sea from Germany to Sweden was still viable.<\/p>\n\n\n

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Pollen dispersal<\/em><\/figcaption><\/figure>\n<\/div>\n\n
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Pollen grains filling the lines on my finger<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

One wonders, therefore, whether scots pines better adapted to hotter, drier climes in southerly latitudes, might be sending their pollen north to fertilise more northerly pines? In an age where northern regions are warming up quickly with climate change, might fertilisation by pollen from drier, warmer-adapted locations, help northern populations prepare for the warmer, drier climate that is undoubtedly coming their way?<\/p>\n\n\n\n

Genuinely, I\u2019ve no idea. But after reading all these studies, it did get me pondering these imponderables.<\/p>\n\n\n\n

Anyway, regardless of where the pollen comes from, after pollination and fertilisation the female flower slowly hardens into a small, green cone. It then takes two years for it to mature into the larger, brown, seed-bearing cone familiar to us all.<\/p>\n\n\n\n

The seeds are obviously very important to the tree, so they\u2019re well protected. The cone is composed of overlapping woody scales, each of which can house two seeds. This means that there could be as many as 100 seeds in a single cone, but a couple of dozen seeds in total is more typical.<\/p>\n\n\n\n

The scales protect the seeds from the elements, but also from being eaten. They\u2019re difficult to get into unless you\u2019ve got a) sharp teeth and dexterity of a red squirrel or b) an especially useful crossed-bill to prise the scales apart.<\/p>\n\n\n\n

However, under the right conditions, cones readily open-up with little persuasion, which brings us to our next scots pine sense.<\/p>\n\n\n\n

The sound<\/strong><\/h3>\n\n\n\n

On those blue-sky summer days, with low humidity and a hot sun blazing down, any walk through a pine woodland is likely to accompanied by a continuous popping sound from up above. This is the sound of pine cones opening up, and for readers of a certain age it sounds like the snap, crackle and pop of milk being poured onto Rice Krispies.<\/p>\n\n\n\n

I already knew that temperature played a part in the process, but wasn\u2019t sure to what extent, so I went online to try and find out more. In so doing, I stumbled upon fascinating research by German scientists, published just a couple of years ago, where they set out to explain the mechanics behind the opening of scots pine cones.<\/p>\n\n\n\n

If you\u2019ve ever picked a pine cone or branch up, or even simply leaned on a scots pine trunk, you\u2019re probably familiar with the sticky resin the tree contains. It\u2019s found all over the tree, but is also inside the cones, and the study suggests that resin acts as a latch on the scales.<\/p>\n\n\n\n

They found that on hot, sunny days with low humidity, the cone scales quickly lose moisture. As a result, they want to curl outwards, but they\u2019re prevented from doing so by the resin, which acts as a glue.<\/p>\n\n\n\n

However, when the cone heats up in the sun, its surface can be as much as 20C warmer than the surrounding air. At 45-50C the resin in the scales starts to melt, relaxing from a solid state into a viscous liquid. This releases the latch and then, with explosive elastic energy, the scales open suddenly with an audible crack.<\/p>\n\n\n\n

In controlled experiments, all of the scales on a pine cone were observed opening all at once in at least one case, but typically the cones\u2019 scales opened over a number of separate movements.<\/p>\n\n\n\n

The experiment subsequently observed how newly-opened pine cones would later close and open again, depending on the environmental conditions, but they would always do so smoothly and quietly. The explosive \u2018crack\u2019 only occurred the first time a pine cone had opened<\/p>\n\n\n\n

The researchers had originally assumed that the initial crack would be key to seed dispersal, somehow catapulting the seeds out of the cones with explosive force, but this was never observed under the controlled conditions. Seeds always remained in situ regardless of how fast the cone opened.<\/p>\n\n\n

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Top: Pine cones brought indoors and left to open over 2 days.<\/em>
Bottom left: a pair of seed \u2018wings\u2019 housed between the scales<\/em>.
Bottom right: pine seeds with and without wings<\/em>.
<\/figcaption><\/figure>\n<\/div>\n\n\n

The study makes for an easy and fascinating read, but I\u2019m left not knowing why scots pine cones have that violent initial opening if it doesn\u2019t actually play a role in ejecting the seeds? The research paper mentions that the cones were securely mounted so they could be filmed, but it\u2019s not clear how they were positioned. On an actual tree, cones face downwards so that seeds can fall out when the cone is open, and so now I\u2019m wondering if perhaps the experiment didn\u2019t replicate that aspect, because SURELY the violent cracking of the cones has served some evolutionary purpose for seed dispersal?<\/p>\n\n\n\n

Ugh, maybe I\u2019m overthinking it. But regardless of the reason for it, the force and speed of the pine cone opening does, apparently, make the scots pine one of the fastest moving plants on the planet!<\/p>\n\n\n\n

Cones will close when the humidity increases, for that is indicative of wet weather. Rain is bad for scots pine seed dispersal because the seeds risk being washed out of the sky too close to the tree. Cones therefore close up to avoid wasting their seeds.<\/p>\n\n\n\n

The seed itself is attached to a single wing. When it falls from the cone it spins through autorotation, keeping the seed in the air as long as possible. This is important, as scots pine likes the sunlight and tends not to grow below an existing canopy. It needs to get far away from its parent, into the sunlight.<\/p>\n\n\n\n

Seeds can fly almost 200m from the tree, but it\u2019s more typical to fly just 10 to 50m. This is why, in places where natural regeneration of woodland is being encouraged, you\u2019re likely to see a single old granny pine surrounded by a close skirt of youngsters.<\/p>\n\n\n\n

Intriguingly, it has been suggested that this method of seed dispersal is a throwback to the Carboniferous period, some 300 million years ago, when there weren\u2019t as many animal-related methods of seed dispersal available.<\/p>\n\n\n\n

The smell<\/strong><\/h3>\n\n\n\n

The third and final sense is smell, because on warm days, as you walk through a pine woodland, there\u2019s a beautifully sweet piney aroma hanging in the air.<\/p>\n\n\n\n

The smell comes from the pine resin within the tree. It is exposed to the outside world via the cones, but also via open cores and holes where the tree has been damaged, often by wood-boring insects.<\/p>\n\n\n\n

Resin contains volatile organic compounds called terpenes, which readily evaporate in warm weather. The non-volatile components of resin, which cannot easily evaporate, crystalise and harden when they reach the exterior, which seals the wound and protects the tree. But the terpenes easily lost through evaporation rise, disperse, and fill the forest with that sweet aroma. The hotter it is, the more evaporation takes place, and the stronger the smell.<\/p>\n\n\n\n

And oh man, it smells amazing!<\/p>\n\n\n

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The familiar \u2018skirt\u2019 of youngsters around a scots pine<\/em><\/figcaption><\/figure>\n<\/div>\n\n
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Everything represented! 2yr old cone at the bottom, 1yr old green cones further up, and this year\u2019s pink flower at the very tip of the new shoot. Male flowers in the background.<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

When I get that first whiff of pine on a warm day, I have to physically stop and take it in. Quite literally, in fact, because it\u2019s always a looooooong inhalation through the nose.<\/p>\n\n\n\n

I always find it weirdly calming.<\/p>\n\n\n\n

Now, that\u2019s partly because when I pause and stand still, and take a deep breath, it creates a moment of mindfulness for sure, which always feels good. But the long, deep inhalation will also, by its nature, bring more oxygen into the blood, boosting levels of that happy chemical, serotonin. That\u2019s simply the outdoors working its natural magic.<\/p>\n\n\n\n

But even beyond that, the pine aroma does feel as though it adds something more to the mix when you\u2019re exposed to it. Something fresh. Something soothing. Something relaxing.<\/p>\n\n\n\n

Most notably among the terpenes are \u2018pinene\u2019 and \u2018limonene\u2019, volatile organic compounds that have been found to have positive impacts upon human health.<\/p>\n\n\n\n

Through inhalation they have an anti-inflammatory effect, helping to relax and open up our airways, but once absorbed within our bodies they also have wider-reaching effects.<\/p>\n\n\n\n

They\u2019re known antioxidants, are antimicrobial, and have even been linked to decreases in tumour growth in mice. They\u2019ve also been shown to positively impact the brain, improving memory and cognitive performance.<\/p>\n\n\n\n

Of course, while all those medical benefits undoubtedly have merit and are all very interesting, they\u2019re also rather distant and nebulous when you\u2019re simply out & about to have a nice walk. So, let\u2019s instead focus on the simple fact that scots pine on a hot sunny day is just a really nice smell. One that makes you feel good, which isn\u2019t surprising given it\u2019s been proven to lower blood pressure, reduce heart rate, and reduce levels of the stress hormone, cortisol.<\/p>\n\n\n\n

My only caveat here, as with the pollen clouds, is that the smell does raise my anxiety levels a tad when I\u2019m at work, because a strong smell of pine on the air is often a tell-tale sign that the landscape is ready to combust.<\/p>\n\n\n\n

But in that situation I need only pause to look around, take a long deep inhalation, and remind myself\u2026\u2026 where better to help manage anxiety and lower your stress levels, than a beautiful, popping, aromatic pine woodland?<\/p>\n","protected":false},"excerpt":{"rendered":"

After a winter of relative dormancy while much of the natural world slumbers, our senses kick into high gear as the warmer months progress. The explosion of life and activity means there are many amazing sights, sounds and smells for us to take in. But while most species grab our attention via one or perhaps two of those senses, the scots pine manages to tantalise all three. The sight We all know what a splendid sight old scots pines are, with their scaly red bark and sprawling asymmetrical crowns, and we love them for it. Their gnarly, deep green beauty…<\/span> <\/p>\n

Read more ›<\/div>\n

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