Henning Knudsen (b. 1948), associate professor, emeritus mycologist, Natural History Museum of Denmark
Within the last 15 years, research at the tree line of the Scandinavian mountain range in Swedish Dalarne has been carried out with the purpose of registering changes in the area caused by climate change. Research led by PhD Lisa Öberg, from Mid Sweden University, and professor Hans Kullman, University of Umeå, showed that the tree line has moved a few hundred meters further up the mountain, followed by herbs and scrubs. However, it was another and more surprising aspect of their research that soon caught the interest of the world. Analysis of macrofossils found under solitary growing spruces at the margins of the tree line revealed that some of the trees were surprisingly old. When applying carbon-14 dating methods, several trees, or the origins of these trees to be more precise, turned out to be thousands of years old. The oldest of these, a solitary spruce growing on Fulufjället, was personalized as Old Tjikko, and it is he who has become the main figure of this book.
Old Tjikko is the type of conifer, which famous Swedish botanist Carl von Linné named Norway spruce (Picea abies) in 1753. Linné found it particularly well developed in the Norwegian mountains even though it does not thrive along the SW Norwegian coast. Also in the southernmost parts of Sweden and in Denmark it is naturally absent, growing only where it has been planted. Norway spruce simply avoids coastline areas where shifts between frost and thaw in spring may occur too often, which is devastating for the sprouting buds. However, such fluctuations are minimized further inland and Norway spruce thrives well here. In fact so well that it is possible to be in the familiar company of Norway spruce (Picea abies var. abies and Picea abies var. obovata) for the next 7.000 km, from Norway to the Okhotsk Sea in the east, covering an area equivalent to more than half of the Northern Hemisphere, a distribution equaled by only a few other organisms. Measured not only by its distribution, but also by biomass and biological importance, we are facing one of the most important organisms of the northern Hemisphere.
It is a popular saying that the Amazon rainforest acts as the green lungs of the Earth. Thus, when they are destroyed, these huge green areas will no longer be able to support the planet by absorbing and hereby limiting CO₂ from entering the atmosphere. It is less often considered that the vast green belt of conifers stretching through western Russia and all of Siberia, which Russians call ‘the Green Ocean’, serves the same purpose. From this perspective, Old Tjikko is a modest representative of one of the very few species of conifers that make up this huge green belt. Their specific ability to adapt to different climates and soil types make their large distribution possible, also for Scots pine (Pinus silvestris), the five needled Siberian pine (Pinus sibirica) and a few species of Larch (Larix sibirica and Larix gmelinii). The spruce can survive both high and low temperatures, from areas covered in snow to areas with dry or moist ground, and from poor soil conditions with very few minerals to areas of limestone with a high level of minerals. Norway spruce is even able to tolerate its roots being constantly covered in water for a period. It is also tolerant to scarceness of light when young, waiting for the surrounding trees to fall or open up their shadowing branches.
Under favorable conditions, Norway spruce will become both old and grand. Trees up to 40 m tall with trunks measuring 4 m in circumference closest to the ground grow in old virgin forests in inaccessible valleys or on steep slopes where it is impossible to remove their trunks if felled. Considering its size, Old Tjikko may not look old. However, in such harsh conditions as those where it was found, close to the tree line in these mountains, with its proximity to subarctic regions and other extreme conditions, it makes sense. Trees here grow very slowly and may therefore be much older than their size suggests, in comparison to similar trees growing under much more lush conditions. Even only moderately thick trunks, which you could easily grasp with just two hands, can easily be more than 100 years old!
Old Tjikko, as you see him in the photographs in this book, with his trunk and branches, is about 5-600 years old. However, the team, which investigated Old Tjikko and similar trees nearby, found that parts of Old Tjikko’s root system can be dated back even further. When carbon-14 dating was applied, some parts were proven to be 9.500 years old. That is a very old age for a living organism and it is in fact the oldest living organism known! Thus, parts of the root system date back this far, while other parts of the system are considerably younger. We need to imagine a shoot coming up from the roots, developing and then dying back, and then growing again from another place from the same root system, throughout the many years of Old Tjikko’s existence. Therefore, the actual tree part of Old Tjikko may be ‘only’ 5-600 years old, but below Old Tjikko, in the layer of debris accumulated here for thousands of years, it is possible to find and date macrofossils of seeds, cones, needles, twigs and other remnants from previous ages.
Around 10.000 years ago, a huge shield of ice covered most of Scandinavia during the last ice age. Old Tjikko’s age is not only an impressive fact in itself, but is also interesting seen from this point of view. As the ice started to melt the simultaneous immigration of plants and animals began, and there is little doubt that Norway spruce was among the first species to conquer the open land after the ice melted, following pioneers like Birch and Scots Pine. Spruce seeds are heavy and not easily moved by wind and weather, but birds and animals can have spread the seeds even over long distances. In this way, Norway spruce fills an enormous role in the forest ecosystem of the northeastern Hemisphere. Norway spruce is so dominant in both biomass and distribution that it inevitably interact with many other organisms. A relevant place to start could be with humans using its timber for building purposes and a variety of utensils and for firewood. Today, modern avant-garde restaurants even serve very young cones of spruce, appreciated for their delicious resinous flavor! The use of Norway spruce in celebrations of religious customs at winter solstice has also made it a favorite among many people, although now superseded by the more fashionable and less prickly Fir (Abies).
The number of organisms connected with Norway spruce is impressive and not known in detail. Fungi and insects are by far dominant in numbers, counting hundreds of species exclusively connected with spruce. The mosses are more conspicuous, but far less diverse. They grow in most spruce forests, especially in areas where there is little light. Over the years, the mosses will develop into thick, soft, green carpet structures, resembling the feeling of walking on a spring mattress. Due to the sparse light, there will only be a few other plants growing here, but in old well-established forests a number of orchids may appear. Not large and flashy, but still wonders of life if you kneel down and study their intricate floral structure. Such wonders Old Tjikko will never see. He is a pioneer living at the extreme edge of what is possible for his kind, exposed to long periods of drought, powerful storms and hard frost. Yet he did not choose these circumstances. He was brought here as a seed, and has clung to life here ever since. His company consists instead of barren stones and the less spectacular growth of grasses, sedges, heathers and other dwarf scrubs and some mosses. Not the precious orchids from the deep and moist spruce forests.
Old Tjikko participates, as all plants do, in the process of photosynthesis. He takes up water through his roots and CO₂ from the air through his stomata. The sun provides the energy to build these simple substances into complex molecules of carbohydrates or sugars. From this first step, the carbohydrates are built into numerous physiological circuits for use in different growth processes. Photosynthesis is a fundamental process of life on Earth, providing us with all the well-known benefits from plants, such as buildings, wood, fruits and seeds. The importance of this process cannot be overestimated. There is however also an opposite process, which generally is grossly underestimated, namely the breaking down or decomposition of dead organic material from plants and animals. When we cherish the large forests of Amazonia, Siberia and Canada, which provide us with oxygen as a result of their photosynthesis, it should not be forgotten that oxygen is also consumed in the decomposition process that is necessary to uphold this eternal cycle.
The process of decomposition is mainly performed by fungi and bacteria, which makes it difficult for us to observe. We might see the fruit bodies of fungi growing on trunks and on the ground, but these only represent a fragment of the actual fungus. Most of it is inside the tree or below ground, where its body, the mycelium, lives in the form of extremely large cobwebby structures with an enormous surface. The mycelium exudes enzymes, which decay the surrounding substrate, which is then inhaled back into the mycelium and used for the life processes in the fungus. In recent years, new molecular techniques have helped us to understand that there can be numerous different fungi living in a single tree, each of them decomposing a certain part of the available organic material, including remnants from the decomposition processes of other fungi. More than a hundred different polypores or bracket fungi are known to attack Norway spruce, depending on age, size, environment and soil type, which may vary between basic, acid, sandy, turfy or mull. Bracket fungi are the most efficient decomposers of tree trunks, whether dead or alive, and therefore an obvious menace for the forest industry. Old Tjikko lives in a very exposed and wind-swept location, which makes it difficult for him to develop nice regular branches and grow to a normal height. However, for the very same reasons, he is indirectly protected against the attacks from many fungi that find it impossible to establish themselves in these wind-swept conditions. We cannot see it in the photos, but it does look as if his entire layer of bark is well preserved. Bark is as important to him as our skin is to us. Any broken branches or other damages, where bark is removed, will immediately expose that part of the tree to attacks from fungi, which will easily germinate on the naked wood, but not on the bark. When an opening in the bark is established, it is only a matter of time before spores land and begin to grow their mycelium into the tree.
Old Tjikko faces many hostile fungi but will welcome other groups of fungi. If you look at the outermost 2-3 mm of his root-tips, you will see that they are in many different colors, such as white, silver, yellow, red, blue or black, and slightly swollen. These are so-called mycorrhizal tips, involving two different organisms growing intimately together in a symbiosis. It does not look like much, but it is extremely important for both involved parts, the tree and the fungus, none of which would be able to exist without the other. Most important forest trees on the northern Hemisphere make mycorrhiza with many different fungi and the process is extremely important for the forest. A layer of hyphae, each cell being 0.01 mm in diameter, from a mycorrhizal fungus (root fungus) cover the root tips of the Norway spruce and the two organisms now work together, mutually helping each other without one of them damaging the other. Through these swollen root tips, the fungal partner will send water and micronutrients into the tree and the tree will send sugar made in its needles back into the fungus.
The role of the roots of a tree is to extract water, but the surface area of the fungus mycelium is so much larger than that of the roots of the tree, and therefore far more efficient at extracting water. A cube measuring one cm³ contains 1-2 km of hyphae! Imagine the surface area of all these hyphae put together and you will understand why fungi are far more efficient in extracting water from the soil than roots. The number of specific mycorrhizal fungi connected with spruce amount to hundreds of species, but in the mountain tundra where Old Tjikko lives only a few mycorrhizal fungi thrive, all crucial to the well-being of Old Tjikko (and vice versa). Another important fungal group are ordinary decomposers living in the acid (low pH) debris of needles, cones, twigs, branches and old bark in the soil below Old Tjikko, where numerous species of fungi have adapted to thrive in this particular environment. At times, this layer will thicken, but as the fungi are continually decomposing the debris, a more or less stable thickness will eventually occur.
In some, but not all years, Norway spruce will ‘flower’, producing small, red cones that will become bluish brown and then completely brown as they mature. During the following spring, the sun will warm the cones and the scales will split open, allowing the seeds to fall out and disperse. Spruce seeds have a long wing-like part causing them to whirl around as they fall, leading them away from the shade of the tree. The seeds are also taken directly from the cones by many different birds that feed on them, helping them to spread even further. The most specialized of these are the crossbills whose beaks allow the bird to grab the seed from one side of the cone wall while keeping a steady hold of the cone wall with the other side of its beak, preventing the seed from slipping away. A highly specialized solution, which make the crossbills totally dependent on the seeds of spruce trees to feed! Without the availability of spruce seeds, crossbills have to migrate for long stretches in search of other climatic areas where these are available. Old Tjikko is now of high age and has stopped producing cones. We might anticipate that a warmer climate could benefit Old Tjikko, maybe causing his roots to produce new shoots, but it is more likely that Old Tjikko has reached his limit in terms of growth and is now simply withdrawing, slowly but inevitably. Living, as he does, so close to the limit for his species, that just one unfavorable dry summer or other extreme weather conditions might severely strain his last chances of survival.
When you see these pictures of Old Tjikko, here in this book, he may look lonely, but he is not. It may be that many of his nearby kin have died away, but he has millions of other family members growing along a 7.000 km belt spanning eastward from Norway to the Okhotsk Sea. His relatives are still one of the strongest and most massively present species in the northern Hemisphere. And although he may have lost many of his nearest neighbors, he has so many other intimate relations, positive and negative, to relate to, including fungi, insects, mosses, lichens and small invertebrates, that a total list of all their names would fill pages. So he will stay on, standing for a while longer and then he will eventually die, maybe sooner or maybe not until after a new long period of being favored by the ever-changing climate conditions of planet Earth. We do not know, but we thank him for his contribution to the continually recycling ecosystem of the forest, so important to all of us, to which he so truly belongs.