Taiwan fir grows from a sesame-sized seed into a giant tree, and the cones must be left for the forest

As Christmas arrives, among the dazzling array of decorations and wreaths, cute pinecones (cones) are indispensable. What trees do these cones actually come from? What secrets lie hidden in their unique shapes? Cones, full of symbolic blessings, often must endure hardship before they can reproduce and take root. To hear about such a contrasting and twisting growth process, let Chen Jianfan, assistant researcher in the Botanical Garden Division of the Taiwan Forestry Research Institute, explain it clearly.

Cone sizes vary greatly, and the small cones of big trees create a contrasting charm

Chen Jianfan is usually a researcher who buries himself in research and is not good with words, but cones are the key that opens his conversational floodgates. In the cabinets of his research room are many cones on display, with more than 20 kinds lined up in a row, all collected through his years of investigation. Some are as large as an arm, while others are as small as sesame seeds.

When Chen Jianfan first created a themed guided tour to train volunteers, he specially classified and organized common cones in Taiwan. The largest cone is that of the Taiwan Huashan pine, while the smallest cones actually belong to the huge Taiwan fir, red cypress, Taiwan hinoki, and Taiwan incense cedar. The Taiwan fir, the tallest tree in East Asia, has seeds only as big as sesame seeds!

They are all cones, so why do their sizes differ so much? "This is just like how different animals can be tall, short, fat, or thin; cones of different groups will naturally grow differently too." Chen Jianfan said this is the result of natural evolution. Cones are one of the most numerous fruit forms of gymnosperms, and Taiwan has about 30 species of gymnosperms, making it one of the regions with the richest variety in the world.

It is true that squirrels love to eat pinecones, and the pine nuts people eat are also cone seeds

Cones or seeds that fall to the ground are also one of the food sources for squirrels and flying squirrels. Chen Jianfan said that although cones do not look as plump and delicious as Fagaceae seeds, it is also common in forests to see cones gnawed down to "just a single cone axis."

Not only squirrels or other wild animals bite off the cone scales and pick out the seeds to eat; Clark's nutcrackers at mid- to high altitudes also feed on Huashan pine seeds. Chen Jianfan said that the seed wings of the Huashan pine are not obvious and cannot be carried by wind to rock faces, and animal feeding is very likely the reason the Huashan pine appears on steep rocks.

"The pine nuts people eat are actually also cone seeds." Chen Jianfan explained that the pine nuts commonly eaten by people mostly come from the Korean pine (Pinus koraiensis), which is widely planted in temperate regions. Its seeds are relatively large and contain many seeds per cone, so it is specially selected for producing "pine nuts."

The number of seeds contained in a small cone is astonishing. Taking Taiwan's red cypress and hinoki alone as an example, in 1942 the Japanese researcher Matsuura Sakujiro sampled and calculated at Taipingshan that Taiwan hinoki produces 790,354 seeds in one year, and red cypress produces 2,135,362 seeds, showing the astonishing vitality of gymnosperms.

Low, mid, and high altitudes each have their own strengths, and large pure forests are related to cones

Gymnosperms are divided into four major groups: Coniferophyta, Gnetophyta, Cycadophyta, and Ginkgophyta. Among them, conifers are the most common group and are further divided into seven families, the best known being Pinaceae and Cupressaceae (including Taxodiaceae). Taiwan's five precious coniferous woods, red cypress, hinoki, Taiwan fir, Taiwan incense cedar (Luanta fir), and Taiwan incense cedar, as well as Taiwan yew, all belong to gymnosperms.

Gymnosperms prefer cool growing environments, but different tree species still have their own preferences. For example: Taiwan fir, Taiwan hemlock, and Taiwan spruce like to grow at mid- to high altitudes (above 2,000 m); red cypress and Taiwan hinoki are mostly found at mid altitudes (1,500 to 2,000 m); Taitung cycad, Taiwan amentotaxus, and podocarpus species are distributed at low altitudes (500 to 1,500 m).

Chen Jianfan added that some gymnosperms are widespread species. For example, Taiwan red pine is widely distributed from low to mid altitudes. The distribution of low-altitude gymnosperms appears within broadleaf forests, while gymnosperms in mid- to high-altitude areas easily form large pure forests, giving people a sense at a glance that "beauty lies in abundance." This kind of forest landscape distribution occurs because of cones.

Cones have unique shapes, and reproduction often requires surviving fire

Cones have unique appearances. Chen Jianfan explained that a typical cone is formed by layers of overlapping cone scales, and there are often bract scales on the outside of the cone scales, with small seeds on the cone scales. There is a size gap between the cone scales and the seeds. For example, the cone scales of the Taiwan five-needle pine are as large as fingers, but the seeds with the seed wings removed are as small as grains of rice. The seeds have thin scaly wings and can be blown scattered by the wind.

Chen Jianfan explained that after cones mature, the cone scales open and close depending on the dryness of the environment. When there is a lot of moisture, the cones close, and when the environment is dry, they open, so when the environment is dry, it is the time for cones to reproduce. He added that Taiwan is located in the subtropics, where temperatures are relatively high, and when cones mature and the environment is dry, they will slowly split open. After splitting open, the wind disperses them. But if it is in a lower-temperature temperate country at mid- to high latitudes, cone reproduction sometimes depends on "fire."

Fire causes cones to split open and helps release seeds. But why does fire not burn all the cones away? Chen Jianfan said this is because forest fires are usually ground fires and burn through quickly, so they do not turn the cones into ashes.

Landslides are both disaster and opportunity, and seeds grow into pure forests

Cones need dryness or even fire to open, while seed germination and growth need open space. For example, once the seeds of Taiwan red pine land in a flat and broad area, they will germinate quickly. Chen Jianfan explained that in recent years, surveys of vegetation regeneration on landslide sites in central Taiwan found that the continued growth and regeneration of coniferous trees in Taiwan's mountains and forests may require landslides or forest disturbance.

Chen Jianfan further explained that he observed that at the mid- to high altitudes where spruce, hemlock, fir, and Taiwan red pine grow, small seedlings often appear on bare land exposed by landslides. He speculated that this is because landslides or forest disturbance clear out large areas, making them suitable for seeds to germinate and grow smoothly. "If they drift onto forest floor, even if the seeds germinate, it is hard for them to compete with other trees for light and they do not grow well, so they spread quickly only in open areas."

Chen Jianfan said that from observations, compared with Fagaceae seeds, which are rich in starch and can survive under the forest waiting for a suitable time to grow quickly, cone seeds have scaly wings and are functionally closer to pioneer species dispersed by wind. The seeds themselves are relatively small, and after drifting with the wind and landing on gravel or soil, they must quickly absorb nutrients from the soil after germination.

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Cypress needs open environments, while hinoki can grow with just a little space

"But if the leaf litter layer on the soil surface is too thick, the seeds cannot touch the soil when they take root, and it is also hard for them to grow!" Chen Jianfan said that large-scale landslides and mountain collapses can also clear the leaf litter layer, making it smoother for gymnosperms to grow. Zeng Yanxue, a professor in the Department of Forestry at National Chung Hsing University, also found in research on spruce forests that fallen trees or small-area landslides can promote the regeneration of forest composition.

In addition to spruce, red cypress also depends on landslides and debris flows. Cypress-type plants survive only in North America, Japan, and Taiwan. Red cypress was described by tree scholar Kanehira Ryozo