Go to the Xisha Islands to see the sea? No, go to see the soil!

“After returning from Xisha, I didn’t look at the sea. From then on, the Maldives was a passerby.”

Beautiful China Stamp Series - Sansha and Qilianyu

The Xisha Islands are located in the northwest of my country's South China Sea. They are composed of the Xuande Islands in the east and the Yongle Islands in the west. They belong to Sansha City, Hainan Province.

In May this year, at the invitation of the Hainan Provincial Soil Survey Office and Director Yang Anfu of the Hainan Academy of Environmental Sciences, three national soil survey experts, Professor Wang Qiubing (Shenyang Agricultural University), Professor Wu Kening (China University of Geosciences (Beijing)) and Professor Pan Jianjun (Nanjing Agricultural University), and I joined a joint scientific expedition team consisting of more than 20 people from 10 domestic units to conduct a 12-day soil survey in the Xisha Islands.

What is so special about the soil in the Xisha Islands?

Landing on nine islands in the Xisha Islands to inspect the soil

Let’s go! With 4 questions

When the nearly 1,000-ton Qiong Qiong Haiyu 11001 fishing boat sailed out of Tanmen Port in Hainan, I felt a sense of grandeur similar to Darwin's scientific expedition around the world on the Beagle. Although I dare not hope to make a discovery as famous as Darwin's, my heart has already flown to the Xisha Islands.

"A thousand-year-old fishing port, the gateway to the South China Sea" - Tanmen Port. Researcher Xie Liangshang of the Hainan Academy of Agricultural Sciences wrote a poem: "Sanshalang, a man from Tanmen, is famous for plowing the sea and patrolling the border. He rides the wind and waves for 3,000 miles, and makes contributions to the country and continues its glory."

The scarce and precious soil of the Xisha Islands has always attracted soil scholars of all generations in my country. In the 1940s, soil scientists Lu Faxi and Xi Lianzhi conducted investigations and studies on the Xisha Islands and the Nansha Islands respectively, accumulating valuable soil survey data. In 1974, Gong Zitong, Jiang Baifan, Zhang Shaode, Wu Zhidong and Wang Zhenrong from the Nanjing Institute of Soil Science of the Chinese Academy of Sciences went to the Xisha Islands to conduct a two-month soil survey, and obtained a series of systematic understandings on the occurrence and evolution of the soil of the South China Sea islands, the soil formation age, the guano phosphate resources, the geochemical characteristics and the distribution law.

Some literature data on the soil of the South China Sea Islands

Mr. Gong Zitong was very happy and excited when he heard that I was going to Sansha. He was impressed that the rise of the motherland has enabled his descendants to frequently go to Xisha for scientific research. He introduced me to all aspects of Xisha soil without reservation. I dare not hope that I can surpass the discoveries and understandings of my predecessors, but I am still looking forward to being able to personally investigate and understand Xisha soil.

I secretly wrote down the goals of this trip in my notebook: 1. What are the characteristics of the soil in the Xisha Islands? 2. What is the pattern of their distribution? 3. Compared with 50 years ago, how have they changed? 4. How can we better utilize and protect the Xisha soil in the future?

Departure

For us who have lived inland for a long time, going out to sea is really exciting. Team members went to the deck to watch. According to local customs, firecrackers are set off when going out to sea. Interestingly, the captain's eldest brother is Mr. Wang Shumao, who has won the "July 1st Medal" . This made us feel full of security and respect for this trip.

Less than 2 hours after leaving the port, the cell phone lost signal. The sea water changed from light blue to dark blue, and finally to a creepy black. The crew told us that we had reached the deep sea area. But soon, the fear was washed away by the full expectation, as evidenced by the poem:

Split the deep blue waves and cut through the myriad clouds in the sky.

The gentle breeze adds just the right amount of power, and the abyss of the ocean seems like nothing.

Flying fish sometimes leap on the shallow waves, accompanied by flying boobies competing for food.

Let my gaze follow the water and sky, and I will forget my worries.

The Yongle Islands in the east: some islands have no "soil", while others are covered with "dung"

At about 14:00 on May 31, after nearly 22 hours of turbulence, we arrived at the Yongle Islands. The Yongle Islands are composed of a series of islands and reefs that are exposed above the water, and there are narrow water gates between the islands. The ship sailed into the "harbor" surrounded by the "atoll" through the water gate between Quanfu Island and Coral Island, and the water surface suddenly became calm.

Our order of landing in Yongle Islands: Yagong Island → Yinyu Island → Ganquan Island → Lingyang Reef → Jinqing Island

First stop: Yagong Island - How do trees grow without soil?

Yagong Island was the first island we landed on. Before landing, we had to get off the big ship and onto the small boat, and then go to the island. As the small boat sailed towards Yagong Island, the water became shallower and more transparent, and we could even see small fish and corals underwater. Schools of fish swam among the corals on the reef flats, some blue, some red, and some gray, which was very cute.

Yagong Island is very small, less than 100 meters wide from east to west and about 300 meters long from north to south. The island is almost entirely covered with white corals and shell debris. The strong sunlight reflected by the coral sand makes it almost impossible to open your eyes, and the soles of your feet feel a little hot. When you step on it, it is loose and makes a creaking sound.

Marine fish drying on coral and shell debris (left) and a dog grave buried in a coral pile (right)

Obviously, the island has not yet experienced the basic soil-forming process such as mineral decomposition and organic matter accumulation. The coral and shell fragments that are overwhelmingly dominant can only be regarded as soil parent material. In other words, there is already a material basis for soil formation, but the soil with structure and layers has not yet developed. However, the few tall coconut trees and arbor trees on the island seem to be questioning us: How did we grow without soil?

We found the answer on the shore. It turned out that in order to develop and utilize Yagong Island, the hardworking fishermen brought brick red soil from Hainan Island as foreign soil to cover the coral sand . The highly acidic and highly viscous brick red soil met the highly alkaline and coarse coral sand, which improved the soil's ability to retain water and fertilizer, allowing coconut trees and other trees to grow into forests. This practice of using foreign soil to improve soil has long been practiced in the South China Sea islands and has achieved obvious results.

Photos of the soil covered with foreign soil and its landscape on Yagong Island.

Baby seabirds and eggs hatching from their shells on Yagong Island (Photo by Li Decheng, 2020)

Second stop: Yinyu Island - there is no natural soil here either

Unlike Yagong Island, the beach of Yinyu is whiter and more delicate. To land on Yinyu Island, you need to take a small boat to wade across a huge reef. The water on the reef is crystal clear, unlike the turbulent sea in the distance, and the water flow on the shore is calmer.

Walking on Silver Island, we found that there was no mature natural soil on the island , but the main part of the soil had turned into finer coral sand, indicating that the coral debris had undergone further physical breakage and transportation, while those coarse corals had been deposited on the reef flats farther away due to the weakening of the transportation power of the tide.

The reef flat of Yinyu is vast, and the water above it is shallow and transparent, so only relatively fine coral sand can be accumulated with the tide to form an island.

The soil in Yinyu is sandy and has relatively uniform particles.

The small vegetable garden on Silver Island, which uses soil from Shi Ke to improve the soil, has a good harvest. The huge white barrels at the foot of the wall are a rainwater collection system (the fresh water that falls from the sky is very precious)

The third stop: Ganquan Island - the soil here puzzles even experts

Both Yagong Island and Yinyu Island have very beautiful natural scenery. However, in terms of their soil, neither of them has developed a B layer indicating leaching and deposition of substances, and even only has a thick parent material layer. To further understand the island soil, we headed to the famous Ganquan Island.

Interesting Stories about Ganquan Island

According to historical records, in 1909, Li Zhun, the admiral of the Guangdong Navy of the Qing Dynasty, discovered two freshwater wells in the central lowland of the island while patrolling the sea. The spring water was sweet and drinkable. He said: "I have obtained fresh water and it tastes very sweet. I dug only a few feet deep into the ground. I tasted the fruit and it was very sweet. So I named it Ganquan Island, engraved a stone and built a strong mast, and hung a flag as a memorial." Ganquan Island got its name from this.

In addition to the Ganquan well, according to textual research, there are a large number of cultural relics from the Tang and Song dynasties buried on the island. In 1974, the Guangdong Provincial Museum and the Hainan Administrative Region Cultural Bureau conducted an investigation and trial excavation on Ganquan Island, discovering one Tang and Song residential site, three coral stone temples, and 37 unearthed relics. It can be said that it is precisely because of the stable preservation environment provided by the soil that these cultures can be preserved for a long time, becoming direct material evidence of the development, utilization, and operation of the Xisha Islands by Chinese ancestors.

The expert group is analyzing and studying the topography, vegetation and soil distribution patterns of Ganquan Island.

Ganquan Island is a typical saucer-shaped depression. Through satellite images, we can see that Ganquan Island has a distinct ring-shaped structure: the outermost circle is a white beach, the inner part is dense dark green trees, the innermost part is relatively sparse shrubs, and there are exposed light gray rocks in between.

In fact, this structure is highly consistent with the topography of Ganquan Island: starting from sea level and heading inward, the altitude gradually increases, and then slowly decreases over the top of the sand bank, and finally forms a relatively flat depression. Since the terrain within the sand bank is relatively stable, it is conducive to the growth of vegetation, and a large amount of organic matter is input into the soil, which promotes the formation of soil. It can be said that the soil distribution of Ganquan Island is a microcosm of the saucer-shaped depression islands in the Xisha Islands.

Typical soil profiles, landscape photos and sand table models on Ganquan Island. Satellite images are from the "GPS Toolbox" APP, provided by Zhang Yongfa; the sand table model was created by Professor Wang Qiubing and drawn by Yang Shunhua

Experts are discussing the soil formation of Ganquan Island. From left to right in the picture above are Professor Pan Jianjun and Professor Li Zhaofu (Nanjing Agricultural University), Professor Wang Qiubing and the author. (Photo by Zhu Fubin)

The soil in the shrubs of Ganquan Island’s depression aroused heated discussions among all team members. On June 2, under the guidance of Professors Wang Qiubing, Wu Kening, Pan Jianjun and Li Zhaofu, Meng Longwei (Hainan Institute of Environmental Sciences) and I selected a profile point in the shrubs. The next day, all team members gathered at this point to start digging and sampling.

We thought this was a typical "A+R" (humus layer + bedrock layer) soil, and we were only going to dig 30cm along the roots of the shrubs. Researcher Zhang Dongming (Hainan Academy of Agricultural Sciences) insisted on digging down, breaking the "R" layer of 18~40cm in the soil, and found that there was a soil layer rich in humus and plant roots buried between 40~55cm, a semi-weathered layer between 55~63cm, and another "R" layer below 63cm. This soil body actually has a cavity structure, and a humus layer has developed on the surface and in the cavity!

A soil profile of the Ganquan Island depression. The soil is 18 to 40 cm deep, with a "bedrock" layer, and below 63 cm there is another "bedrock" layer. Between the two is a chamber filled with soil and plant roots, which is very unique.

This makes it difficult for experts who identify soil types.

Some experts believe that the cementation of phosphorus and calcium in the 18-40cm soil layer is the product of the soil formation process. It is a secondary calcium carbonate formed by the carbonate contained in the runoff water from the exposed bedrock (coral limestone) area around the profile, which condenses into the soil and should be classified as a calcium-phosphorus layer. The five soil layers from top to bottom are Ah1 (humus layer 1)-Bkmφ (calcium-phosphorus layer)-Ah2 (humus layer 2)-Bkm (calcium-phosphorus layer)-C (parent material layer), and the soil is called phosphorus-calcium moist embryonic soil. Some experts also believe that this soil structure is very common in carbonate rock areas. It is the result of water and soil leaking into the cavity of the lower layer along the rock cracks and then continuing to develop. The B layer is still the bedrock layer. The layers can be divided into Ah1-R1-Ah2-Bkm-R2, and the soil should be called calcium-moist normal new soil. Is it the B layer or the R layer? Is it embryonic soil or new soil? It is difficult to reach a conclusion at the moment, and the final result still needs further analysis and discussion.

The calcium-phosphorus pan layer in the soil profile of the Ganquan Island depression (left); prying open the upper part of the 18-40 cm soil layer, the cemented shells can be seen (right)

Stop 4: Antelope Reef - Houses built by corals

After leaving Ganquan Island, we continued to head towards Lingyang Reef. The reef flat of Lingyang Reef is very vast, dotted with reefs. In order to land safely, we circled on the reef flat for about 40 minutes.

Similar to Yagong Island, there is no natural soil developed in situ on Lingyang Reef. The parent material on the island is coarse coral and shell debris. Red brick soil brought from other places is laid in front of and behind the fishermen's houses, and trees such as coconut trees and seaside wood have grown lushly.

The reef flats and rocks of Antelope Reef (above); houses and flower beds built with corals (below), showing the function of corals as building materials

Fifth stop: Jinqing Island - this place looks a bit like Nauru!

We boarded the small boat leaving Lingyang Reef and headed for the last stop of Yongle Islands, Jinqing Island. The name "Jinqing Island" was given to commemorate Shi Jinqing, the envoy of Srivijaya in the Ming Dynasty, who assisted Zheng He in defeating the pirate Chen Zuyi in the fifth year of Yongle (1407).

With the empirical model of soil distribution on Ganquan Island, we had a rough guess about the soil distribution on Jinqing Island before landing - a shape close to an ellipse, a dish-like terrain, ring-shaped vegetation and corresponding soil. The rest was to conduct field investigations and verifications, and look forward to some new discoveries. Sure enough, when investigating the hinterland of Jinqing Island, we made a new discovery - phosphate lime soil!

As usual, we set up three sampling points according to the distribution of terrain and vegetation, one of which is located in the middle of Jinqing Island. We didn't have any special expectations, but the white "stones" exposed on the surface caught the attention of Professor Wu Kening, who then called Professor Pan Jianjun and Professor Wang Qiubing for a "consultation". The three experts immediately decided to dig the soil profile on the spot for further observation.

The distribution location of Jinqing Island Point 2 and the white "stone" exposed on the surface - guano phosphate

Soil profile of Jinqing Island No. 2 (left) and landscape photo (right). In the left picture, the 0-30 cm soil layer is the phosphorus accumulation layer, where guano phosphate is concentrated, and the fine sandy soil layer is below.

As the name implies, phosphate lime soil is a type of soil rich in carbonates and phosphates. Earlier, China did not uniformly name and classify the soil in the Xisha Islands. In 1977, Mr. Gong Zitong and others published the book "Soil and Guano Phosphate Minerals in the Xisha Islands of China" based on field investigations, proposed a soil classification scheme for the Xisha Islands, and named this soil "phosphate lime soil" for the first time, which was applied in the second national soil survey . It is easy to understand why it is called lime soil, because the parent material here is basically corals and shells with simple chemical composition (more than 95% are carbonates). So, where does the phosphorus here come from? The answer is hidden in the guano (is there dye in the guano?).

Seabirds living on Dong Island (Photo by Yang Anfu)

A cross-section of the phosphate lime soil at Jinyin Island in the Xisha Islands (left; photographed by Gong Zitong in 1974) and a microscopic photograph of its phosphate accumulation layer (right; photographed by Cao Shenggeng)

In the middle of some islands, there is dense vegetation, which attracts a large number of seabirds to build nests and live. From a distance, the flocks of birds look like a field of white cotton ripe for harvesting. The birds, full of fish, directly rain "feces", causing the phosphorus-rich bird droppings to continuously enter the soil. Under the catalysis of time, these feces continue to decay, decompose and cement into minerals, and merge with the original soil, eventually forming the phosphorus lime soil that is characteristic of the Xisha Islands. The more fertile soil further nourishes the vegetation, and the lush vegetation attracts more and more seabirds. In this way, fish eat grass, birds eat fish, excrete feces to fertilize the soil, and the soil fertilizer promotes the growth of large trees, attracting more birds to live... What a vivid picture of the cycle of earth elements!

Although the name "phosphatic lime soil" is simple and clear, it lacks a quantitative soil type identification standard. The establishment of the Chinese soil system classification has overcome this problem, and "protosol" (such as phosphatic calcium moist protosol) is often used to represent phosphatic lime soil. For soils with a "guano layer" that is thick to a certain extent, it can also be classified as a homohumus soil. According to records, the guano layer of Treasure Island was 80 cm thick in 1974 , so it was classified as a phosphorus-rich lithological homohumus soil. Today, with the establishment of the Xisha Islands soil system, we have a deeper understanding of the soil of the Xisha Islands.

The soil of the Xisha Islands was originally very poor, and the formation of phosphorus lime soil provides important phosphorus fertilizer for plant growth. If used in a restrained manner, this is an inexhaustible fertilizer resource. Unfortunately, due to various reasons, the phosphorus accumulation layer in this section we see is now only about 30 centimeters, and most seabirds have moved to other islands such as Dongdao. From the perspective of soil diversity, the original fertile humus has become the current embryonic soil or even new soil, which is actually a kind of soil degradation. The tragedy of Nauru is a lesson not far away!

Close-up of guano phosphate rock; after breaking it open, bright yellow-brown phosphate cement can be seen

Xuande Islands in the west: There is an island with soil from all over the country

After checking the "dung" of Jinqing Island, we arrived at Xuande Islands after a night's sailing, which consists of Yongxing Island-Shidao, Qilian Island, Xuande Atoll, Yinli Beach and Dark Beach, etc. Qilian Island (where there are attempts to "plant" corals) is a general term for seven small islands, including Zhaoshu Island, Beidao, Zhongdao, Nandao, Beishazhou, Zhongshazhou and Nanshazhou, and in a broad sense also includes Xishazhou, Sanshizi and Xixinshazhou.

Satellite images of the Xuande Islands and our order of landing: Xishazhou → Zhaoshu Island → Beidao → Yongxing Island

Landscape of Xishazhou. The flat land in the distance is the core breeding area for seabirds and is not allowed to enter at will.

First stop: Xishazhou - the biggest danger of this trip

Xishazhou is the first island we landed in Xuande. When we landed on Xishazhou, we encountered the greatest danger of this trip.

Early in the morning, the sea was stormy and rainstorms were pouring down. The rolling tides and the shaking hull had already dissuaded a group of scientific expedition members from going. Taking advantage of the break in the rain, the improvised "suicide squad" got off the small boat and headed straight for Xishazhou. The most dangerous part was changing from the big ship to the small boat. The shaking small boat kept hitting the big ship. When going down the rope ladder, if you were not careful, your feet might be crushed and broken by the small boat. However, with the great help of the fishermen, all the members landed on Xishazhou, and soon the rainstorm stopped.

The monument to the tree planting campaign on the islands and reefs of Xishazhou

Since 2015, the Sansha Municipal Government has launched a large-scale tree planting campaign on islands and reefs. There are many species of plants in Xishazhou, including Pittosporum serrata, Tung oil tree, Malus tamanu, coconut trees, and sea lilies. Among them, Casuarina equisetifolia and Pittosporum serrata are the dominant species and grow very lushly.

After walking around the island, we found that it was almost entirely made up of coral sand, with no natural soil developed in situ. Finally, we selected a point in the Casuarina forest, where the vegetation was the most luxuriant, and dug and observed a soil profile. From the perspective of the profile, the surface was covered with a thick layer of dead branches and leaves, and the whole layer was sandy, which was obviously young soil deposited recently.

The internal landscape of the Xishazhou section and the Casuarina equisetifolia forest where it is located

The dead branches and leaves on the surface of the Casuarina forest have not yet undergone obvious decomposition

As the tide started to recede after 2pm, the water level on the reef flat would continue to drop, and even a small boat would have difficulty sailing out of the reef flat, which would have put us at risk of staying overnight on Xishazhou and being lonely on the cold sandbar. Therefore, we hurriedly collected a profile sample and two surface samples on Xishazhou and had to return home before 1pm.

Second stop: Zhaoshu Island - Chinese fertile soil forest

Zhaoshu Island is one of the larger islands in Qilianyu, with relatively complete infrastructure. It has not only a wharf and a road around the island, but also special desalination and sewage treatment facilities. The houses are also very distinctive, and even the vegetable garden has a clear and elegant name - Yixiang Garden. The topography, vegetation and soil distribution of Zhaoshu Island are roughly the same as those of Jinqing Island. The typical phosphate lime soil is mainly distributed in the middle of the island, which will not be elaborated here.

Zhaoshudao section and its guano phosphate deposits

Near the dock of Zhaoshu Island, there is a "Chinese Fertile Soil Forest" that has attracted everyone's attention. In 2017, the Sansha Municipal Government held a soil collection activity called "Chinese Fertile Soil in Sansha", using soil from 31 provinces, municipalities, autonomous regions, Hong Kong, Macao and Taiwan and water from the Mother River to plant a "Chinese Tongxin Tree" and 34 "Brother Trees". The soil-carrying ship set off from the site of the Nanjing Ming Dynasty Treasure Ship Factory, the starting point of Zheng He's voyage to the West, and sailed across the ocean to Zhaoshu Island. The soil has closely connected the mainland of the motherland with this place!

The Chinese fertile soil forest of Zhaoshu Island is paved with soil from all over the country

The depression landscape of Zhaoshu Island (left); the coastal landscape of Zhaoshu Island (right)

The third stop: North Island - saw the desperate turtle

Bidding farewell to the beautiful and warm Zhaoshu Island, we came to Beidao, which is famous for its abundant sea turtles. Unlike the aforementioned islands, the guano phosphorus pans on Beidao appear deeper, distributed below 60cm, and the cemented particles are coarser. It may be because this point is located on the slope, the material is not easy to accumulate, and the color of this section is lighter than the sections of Zhaoshu Island and Jinqing Island in the depression, but the exact reason needs further analysis.

Beidao section (left) and its phosphorus disk (right)

During the rainy period when we could not carry out our work, we visited the turtle protection center on the island. We learned from the staff that the turtles in the center mainly come from the marine fishing company. The turtles they rescued were either injured or had eaten plastic by mistake. Since turtles cannot digest and decompose plastic, it is difficult for them to dive to hunt, so they can only float on the sea in despair, waiting for the last moment to come.

Sea turtles have difficulty diving after ingesting plastic

Fourth stop: Yongxing Island

Leaving Beidao, we went to the last stop of this trip - Yongxing Island.

Yongxing Island is the seat of the Sansha Municipal Government. Sansha City was officially established on July 24, 2012. Starting from the pier and going straight along the main road of Yongxing Island, you can see various facilities such as post offices, hotels, schools, cinemas, restaurants, shops, etc. It can be said that although the sparrow is small, it has all the necessary facilities. Moreover, public places such as schools, cinemas, hospitals, etc. are open to the public free of charge. On June 9, 2023, we bid farewell to the Xisha Islands with the harvest along the way.

Conclusion

During this 12-day expedition, we visited 9 islands and sampled 11 soil profiles. The parent materials of the soils were all coral and shell residues. The soil system classification types identified were mainly phosphorus-calcium moist embryonic soil, phosphorus-humid normal neosoil, ordinary moist normal neosoil and calcium-humid normal neosoil. These precious soil samples will not only serve as important materials for scientific research, reveal the mystery of Xisha soil formation and guide islanders to improve soil scientifically, but will also be made into specimens for popular science display.

For disc-shaped depression islands, such as Ganquan Island, Jinqing Island and Zhaoshu Island, the terrain is relatively stable, the soil age is older, and the distribution of soil is adapted to the vegetation belt, forming a ring-shaped distribution, with embryonic soil and new soil on the inner and outer sides of the sand bank respectively. These embryonic soils are mostly phosphatic lime soils that are greatly affected by the input of bird droppings. The thickness of the soil depends on the balance between the formation rate and the erosion rate. With the departure of some seabirds, the amount of material input has decreased. How to sustainably protect and utilize these remaining "feces soil" resources will be a problem worth studying.

For sandbar islands, such as Yinyu and Xishazhou, the soil development time is short and the overall impact of seawater is still large, especially in Xishazhou. Soon after digging, seawater with a foul smell can be seen seeping out, and the soil is young and newly formed soil. Artificial afforestation is of great significance for stabilizing the terrain and developing the soil, but the vegetation is greatly affected by wind damage and salt damage, and the phenomenon of vegetation losing green is also relatively common. In addition to improving and fertilizing the soil by covering with brick red soil and mixing with the island's self-produced "manure soil", some islands with conditions have also built seedling greenhouses to prevent seedlings from being threatened by storms, rainstorms, exposure to the sun, nutrient deficiency, salt damage, insect pests and even soil erosion. How to prevent and control such problems still requires further analysis and research.

Coconut trees suffering from chlorosis on Xisha Island and Terminalia truncatula infested by pests on Jinqing Island

In the vast ocean, the Xisha Islands are just a drop in the ocean. However, these scattered islands play an extremely important role, and their strategic significance is self-evident. Although the soil on the islands is scarce and relatively poor, it is an important element for fishermen to settle down, develop production, green the islands and maintain the balance of the ecosystem, and is of great significance to the construction, utilization and protection of the islands.

Although our land is small, our soul is connected to China! Although our land is thin, we will make China rich!

Main references:

[1]. An Lei, Cao Feng, Zhang Zhiguo, Deng Qijiang. Ganquan Island[N]. People's Daily Overseas Edition, 2021-1-11, Page 11.

[2]. Gong Zitong, Zhang Ganlin, Zhang Chu, Yang Shunhua. Soil: The Skin of the Earth: Telling the Story of Soil Science from Postal Culture[M]. Beijing: Science Press, 2021.

[3]. Investigation team of Guangdong Botanical Institute. Natural environmental conditions and main soil types in Xisha Islands[J]. Soils, 1975, (1): 57-60.

[4]. Wang Yingchun. Tang and Song Dynasty Ruins on Ganquan Island in the Yongle Islands of the Xisha Islands: The sweet springs are not exhausted, and the legacy still exists [N]. Hainan Daily, December 21, 2020, p. 15.

[5]. Yang Anfu, Hu Yulin, Lin Tian, ​​Li Decheng, Wang Dengfeng, Zhang Mingkui, Lu Ying, Zhang Ganlin. Establishment of soil series in Xisha Islands, China[J]. Acta Pedologica Sinica, 2022, 59(3): 667–677.

[6]. Zhang Ganlin, Li Decheng. Field Soil Description and Sampling Manual[M]. Beijing: Science Press, 2022.

[7]. Zhang Ganlin, Wang Qiubing, Zhang Fengrong, Wu Kening, Cai Chongfa, Zhang Mingkui, Li Decheng, Zhao Yuguo, Yang Jinling. Classification of soil families and soil series in China’s soil classification system [J]. Acta Pedologica Sinica, 2013, 50(4): 826-834.

[8]. Zhang Ganlin. Chinese soil scientists’ attachment to the South China Sea[N]. China Science Daily, 2016-12-05, p.6.

[9]. Zhang Shaoruo, Liang Jixing, Lin Dian. Distribution, form and properties of soil phosphorus in Xisha Islands[J]. Journal of Tropical Crops, 1995, 16(1): 48-54.

[10]. Soil System Classification Research Group of Nanjing Institute of Soil Science, Chinese Academy of Sciences and China Soil System Classification Research Collaboration Group, 3rd edition [M]. Hefei: University of Science and Technology of China Press, 2001.

[11]. Xisha Islands Soil Survey Group, Nanjing Institute of Soil Science, Chinese Academy of Sciences. Soil and Guano Phosphate in Xisha Islands, my country[M]. Science Press, 1977.

Author: Yang Shunhua

Author unit: Nanjing Institute of Soil Science, Chinese Academy of Sciences

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