An important natural resource

On the first manned mission to the moon in 1969, one of astronaut Neil Armstrong’s main tasks was to collect samples of lunar soil. So why would soil collection be given top priority in a journey into the unknown? Hseu Zeng-yei, director of the National Taiwan University Soil Museum and professor of agricultural chemistry at NTU, says: “It’s because soil is the source of life.”

The most familiar function of soil is as a medium for the growth of plants. “The 18 currently known essential human nutrients were all identified through soil research.” Secondly, soil serves as habitat for many organ­isms, including billions of microbes that are invisible to the naked eye. Penicillin, the first antibiotic ever discovered by medical science, was derived from a common soil microbe.

Soil’s third function is holding and purifying water, while its uses in construction comprise its fourth function. Finally, soil participates in the planet’s elemental cycles. For instance, it is nitrogen-fixing bacteria in the soil that absorb nitrogen from the atmosphere, making it available for plants to use. Soil plays a huge role in supporting the ecosystem’s cycles.
 

No soil, no life

Chiu Chih-yu, a research fellow at the Academia Sinica’s Research Center for Biodiversity, explains the importance of soils through the rise and fall of an ancient civilization. The Tigris and Euphrates river systems gave birth to the world’s first complex civilization on the Meso­potamian Plain, where the stable water resources and fertile soils at first supported rich agricultural production. Population growth, however, led to overdevelopment. When upstream forests were cut down, soils downstream lost organic material. Eventually they could no longer support enough food production, leading to social disruption and decline. Soil degradation was thus one of several factors that caused the collapse of that civilization.

The history of the ethnic Chinese diaspora is also connected to soils. China’s southeast coast is known for its poor soils. The hardscrabble environment prompted many to leave for Southeast Asia, Taiwan or further afield. Chiu notes that the first Taiwanese-based ancestor in his patrilineal line crossed the strait to Taoyuan as part of those migrations. So it is that every clump of soil beneath our feet has a story to tell.

“No soil, no life,” says Hseu.

The five factors of soil development

The five main factors governing the development of soil are parent material, climate, topography, living organ­isms, and time. “The weightier factors will have the bigger impact. Hence, in the classroom I always explain that soil is a linear equation with five variables.”

The parent material is the rock from which the soil is derived. Young soil naturally reflects the qualities of the parent material. A hot, wet environment will speed the weathering of the parent material. With a lot of rain, elements such as potassium, calcium, and magnesium leach from the soil, and the soil becomes more acidic. Consequently, red clays are more common in tropical regions, because other elements have leached away, giving iron oxides prominence. The older a soil, the more red and acidic it will be. We thus see how time factors in.

Organic activity also weathers soil. Chiu explains how different bamboo species interact with different soil ecologies. Tortoiseshell bamboo (Phyllostachys edulis) is planted in the mountains at middle elevations. It is cultivated for its edible shoots and woody culms, but the associated digging and chopping frequently disturbs the soil, damaging its organic materials. Not continually accumulating humus like tree forests, stands of tortoise­shell bamboo become prone to soil degradation. The area around Zuozhen and Longqi in Tainan and Tianliao in Kaohsiung, on the other hand, is known for its “moonscapes”—badlands with soils so saline that they are ill-suited for growing most plants. Locals started to plant thorny bamboo (Bambusa stenostachya) there in the Japanese era. Thorny bamboo contributes organic matter, improving the physicochemical properties of the soil. Thus, planting stands of thorny bamboo is a good long-term strategy for improving the soil in such areas.

When you understand the factors behind the development of soils, it is not hard to see why Taiwan’s soils are so varied. The island of Taiwan, uplifted as the Philippine Sea Plate collides with the Eurasian Plate, features rich sources of parent material. “Furthermore, land on the Tropic of Cancer is largely continental, with Taiwan being the only island, and the changes in elevation here have led to different climatic zones.” This combination of factors has resulted in Taiwan’s great soil diversity. “Soil provides habitats for organisms,” Hseu Zeng-yei notes. “So soil diversity leads to organic diversity.”
 

Understanding soil and terroir

Taiwan has ethnic diversity to match its soil diversity, with at least four major ethnic groups. Each has brought different methods of soil use and related cultural practices. The Han Chinese, for instance, brought wet-field farming, which led to rural Taoyuan being dotted with irrigation ponds.

“The word fengtu [literally ‘wind and earth’] refers to the terroir and culture fostered by a place’s land and climate.” The oldest soils on Taiwan are estimated to be those of the Linkou Plateau. Over millennia, the nutrients in the soil have been washed away, leaving behind high quantities of iron oxide, which makes the soil red and highly acidic. “This soil was one thing that brought Taiwan into the global spotlight,” says Hseu, who explains that Taiwan grew renowned for its teas in large part because of its soil. Taiwan’s laterite (red clay) plateau from Linkou to Taoyuan and Hsinchu used to be famous for the teas it produced. The Bagua Plateau, straddling Changhua and Nantou, produces songbo evergreen oolong. In Eastern Taiwan, farmers at Wuhe in Hualien’s Ruisui Township are growing the newly developed Taiwan honey-scented tea, while the Luye Highland in Taitung has been producing tea since the Japanese era. “Tea bushes like acidic soil, and the clouds and fog that come with the high elevation of the plateau promote tea leaf growth. That connection between tea leaves and soil is quite representative of Taiwan’s culture.”

“By understanding a place’s soil, you can understand its terroir and culture.” Hseu cites the famous rush weaving industry of Dajia in Taichung, which arose only because some of the land there was dry and saline, and no good for growing anything else. Today the Jianan Plain is described as the granary of Taiwan, but the farmland there used to be described as “fields at the mercy of the weather.” Despite having richly mineralized soil, they lacked sufficient water resources. Local food supplies were thus dependent on frequent rainfall.

It wasn’t until ample water was provided by the Jianan Irrigation system, designed by Japanese civil engineer Yoichi Hatta and completed in 1930, that the character of the local soil changed and rice production on the Jianan Plain burgeoned. “Yoichi Hatta in fact was always thinking about how to improve the local soil,” says Hseu.

Soil scientists find their interest being piqued constantly in daily life. When Hseu watches the French Open, he considers how little red clay is found in temperate zones. Building clay tennis courts there must be quite expensive. The Japanese archipelago features dark volcanic soils, and the infield in the film Kano reflected that. Fans of American baseball may notice that if a broadcasted game is in Florida, which is in the subtropics, the field’s dirt is reddish. But if the game is in Seattle, which is in a volcanic zone, the dirt is appropriately dark. Hseu is thus able to connect soil to culture and daily life for us.

Treat with care

“Researching soil,” Hseu says, “has led me to under­stand why the Portuguese called Taiwan ‘Ilha Formosa’—the beautiful island.” The discipline has also taught him not to judge a book by its cover, because one has got to dig to deeper levels to truly understand the nuances of a locale’s soil.

Taking a global view, it is clear that the world’s exploding population since World War II, along with the shortage of food to support it, has caused a major crisis. The emphasis that the UN sustainable development goals place on ending hunger and poverty only further demonstrates the importance of soil. And soil will even play an important role in achieving the emissions-­cutting goal of “net zero,” a hot topic in recent years. “Like trees, soil has the capacity to store carbon. In fact, about 60% of the carbon in forest carbon sinks is in the soil.”

Soil is likewise connected to many international pollution problems, such as the dust storms that hit Taiwan, Japan, Korea and other countries in the winter. Scientists have determined that the dust in these storms comes from the Mongolian Plateau. Overlogging of the forests there has caused desertification. When the north wind blows, neighboring countries are all affected.

“A place’s water and earth make its people what they are.” That Chinese expression speaks to how the soil shapes each locality’s people and their culture. Those forces also have a global impact. Soil is properly classified as an irrecoverable resource and is bound up with important sustainability issues around the world. It is our responsibility as global citizens to get to know it better and to treat it with care.

For more pictures, please click《Taiwan: A Global Museum of Soil》