Tag Archives: China

Lost world discovered in twilight of Chinese caves

Elatostema obscurinervium growing in stalagmite drip zones, one of 31 species known only from caves in China and Vietnam.

I never expected to be working in caves, that is, until I started to study nettles in Southwest China with Guangxi botanist Wei Yi-Gang. When Wei suggested that we collect in a local cave I was not hopeful. However, that first visit transported me to another world, an eerie moonscape in which plants thrived in powdery ‘soil’ and perpetual twilight. I was immediately gripped and determined to explore as many caves as possible. Over the next few years we visited over 60 caves, travelling on underground rivers, hiking across rice fields or sneaking into big tourist caves. Each time I got the same thrill from entering these strange and silent places. This has culminated in a paper just published in the scientific journal PLOS ONE.

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Yangtse cave, Fengshan County, Guangxi. Eight species new to science have been described from here.

There has been very little research on plants in caves. Having come across such a widespread and diverse flora we wanted to make sure that both botanists and cave biologists were aware of it. This is because plants growing in caves could tell us a lot about how plants adapt to extreme conditions. Also, as to how connected caves are to the surrounding landscape and each other. To do so we set out to answer a series of questions. Probably the most obvious was, are plants growing in light levels distinct to those outside? Did the species evolve in caves? Or are they survivors of a previous vegetation that at some time connected caves? And, are these plants important for conservation in the region? For example, in the restoration of the karst forests lost during the 20thC.

Cave converted to a tourist attraction.

There are thousands of caves in Southwest China and the landscape that they helped form has long been famous in Chinese culture and art. A landscape covered in dense forest until the 20thC at which time the ‘Great leap forward’ and later the ‘Cultural revolution’ resulted in massive deforestation. Once cut, the forest has not returned but instead been replaced dry scrub. The 21stC has brought new threats from cement and tourism. The rock that forms these caves is used to make cement, now in high demand, that combined with a rapid growth in tourism has meant once untouched ‘lost worlds’ are being mined or filled with walkways, bright lights and litter.

Collaborators from the Guangxi Institute of Botany, Fu Longfei and Chen Xiaoqin taking photosynthesis measurements.

We found that some of the plants growing in caves are surviving in very low levels of light. Levels much lower than previously known. From other cave studies we also know that daily changes in temperature and humidity are very small. There is also some suggestion from other studies that the cave atmosphere may be richer in CO2. It could be that low levels of light are being offset by more stable conditions and higher CO2 – an interesting question for future research.

We also found that whilst most of the plants we document are known from forest habitats elsewhere, 31 species are only known from caves. For reasons given in our paper we do not believe that this means that they evolved in caves but rather that they are species which were restricted to the forests lost in the 20thC.

So, it looks as if the plants that we are finding in caves are relics of forests that were lost to deforestation in the 1950s and 1970s. With a current focus on restoring these lost forests in China, these surviving populations could now become a valuable source of local plant material for restoration.

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Yin Jia cave close to Gu Lin village in Yunnan. At 1600 m above sea-level this is also one of highest elevations that we have collected in caves.

Other posts by me on this topic

2016: Studying cave-plants in SW China

2014: Caves explored last month



Caves explored last month

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Yin Jia cave close to Gu Lin village in Yunnan. This is the 37th cave we have explored. At 1600 m above sea-level this is also one of highest elevations that we have collected in caves. Click to see a clip of the cave entrance

Thanks to funding from the Bentham Moxon Trust and the Guilin Botanical Garden, myself and colleagues explored five caves for plants in October of this year (2014). There are likely thousands of caves in the limestone karsts of south-east asia which contain plants. Whilst of great interest botanically and for conservation they are also beautiful in their own right and each cave is unique. I thought I would provide a portrait of each one to show how varied they are in their form, where plants grow in them and their size.

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Cave #40. We spotted this cave from the road and getting to it involved climbing onto an aquaduct that ran along the base of a large cliff and then jumping off into the cave. The elevation of this cave is 660 m above sea-level and it is located in the province of Guizhou.

The cave above was one of the few that we spotted from the road and then were able to get to. It is also one of the few that had little evidence of human disturbance, very few footprints and areas of pure white travertine that had fallen from the roof had not been walked on or collected. The main plant-bearing cavern of the cave was about 25 m deep and the roof 15 m high and it had a well developed flora, you can see plants from the african-violet family (Gesneriaceae) in the foreground and we collected five species of nettle here.

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This is the enormous Xiangshuidong Tian Keng cave in Guizhou, known to us as cave#38. Click to see a panorama from within the cave

Xiangshuidong Tian Keng cave in Guizhou was one of the largest caves that we have collected in, but also one of the most impacted by tourism and use by local communities. The main cavern is about 250 m deep with a roof between 45 and 30 m high and it is set within a huge cliff forming the side of a mountain. It also has a waterfall and river running across the back of it. It is in this cave that we found a very rare and unusual form of Elatostema oblongifolium that has its male flowers borne on specialised shoots but overall the plant diversity of the cave was quite low, presumably because of the large numbers of local tourists and associated trampling of much of the ground available for plants

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This is Cave #36, Yuen Ja cave close to Mahi Po Niochan village in Yunnan. The cave has two main chambers, each with their own entrance and which come together at their back where a new and unexplored chamber continues on. Each of the main chambers is 30 to 40 deep and the entrances 3 to 6 m high.

This was the first cave that we encountered on this field trip. We found it after first being taken to a hole in the ground as what must have been a mistranslation from Mandarin into the local dialect. The cave was relatively big and had a trail running inside. The main cavern shelves very steeply meaning that very little light penetrates into the cave. Despite this and the relatively high altitude, 1500 m, we collected seven species of nettle from here.

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Unfortunately I didn’t record the local name of this cave so it is known only as Cave 39. It is in the province of Guizhou at an elevation of 600 m. The main cavern was about 40m deep and  the entrance about 10m high and 30m wide. Click to see a panorama of the interior of the cave.

This cave should have been perfect as it shelved gently meaning that light penetrated quite deep, it also had plenty of places for plants to grow, such as boulders and rocks. We only collected four species of nettle here, probably because the cave was heavily impacted by farmers using it as a barn to keep their water buffalo in at night. Evidenced by lots of hoof prints and dung. This is a very common use of caves and the trampling of buffalo and their herders can have a significant impact on the plants in the caves (see below).

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Two weeks collecting in caves and gorges in South China

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Very steeply sided hills characteristic of limestone karst. This limestone was first exposed ca 240 million years ago and the karst produced by the action of rain over tens of millions of years

I have just returned from collecting nettles in South West China with my great friend and colleague Professor Wei Yi-Gang and researcher Fu Long-Fei from the Guilin Botanic Gardens. For several years we have been working on documenting the nettle diversity of the limestone karst of this region, focusing on the poorly known cave-associated floras. Karst is a form of limestone which has been weathered by rain for millions of years resulting in finely divided and sharp surfaces and very steeply sided hills, small mountains and gorges. The karst where we have been working form part of a formation which runs from Myanmar, northern Thailand and Vietnam and across into southern China and includes the famous ‘stone forests’ of Yunnan and Guangxi. I am interested in karst because it is where nettles are most diverse, both in terms of genera (species groupings) and species. At a single location it may be possible to encounter eight genera and over a dozen species!

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Yuan Jiá cave in north-eastern Yunnan close to the border with Vietnam at an elevation of 1500 m, we collected five species of nettle from this cave. Click on picture to see me introducing our work outside of the cave

Because the limestone is porous it has resulted in the formation of thousands of caves whose entrances have been colonized by plants from a small group of families: nettles (Urticaceae), african violet family (Gesneriaceae), Begonias (Begoniaceae), ivy family (Araliaceae), the coffee family (Rubiaceae) together with ferns and mosses. The most diverse of these are the nettles, one group of which, Elatostema has about 1/5 of the species from this region known only from caves. As well as having very low light levels, sometimes 1/10 of 1% daylight, the caves have constant humidity and low temperatures which contrast strongly with the cave exterior. The cool air of a cave can be felt up to 20 m from the entrance, often before the cave itself can be seen. We believe that the species associated with caves have likely come from the deep shade of the forests that once dominated this area but which have since been lost to agriculture. It also possible that some of the species are relicts of a previous, cooler climate during the last ice-age. This is something that we have begun to study.

Elatostema binatum, one of over 15 species of Elatostema known only from caves in Guangxi, Yunnan and Ghuizou. This species is unusual in bearing male flowers on young shoots, female flowers have never been seen!

Caves represent a last refuge for several hundred species in SW China and now is a time of great change as caves come under threat from tourism, agriculture, urbanization and cement production. We want to help conserve these caves and the species that they include by first documenting their diversity and distribution across SW China. This information can be disseminated within China in the hope of raising awareness and protecting individual caves. It could also be used to identify a network of protected caves which include all of these species. Professor Wei would also like to develop protocols for cultivating the species outside of caves, something that is very difficult to achieve at the moment and which could represent a vital step for their conservation.



Cave-dwelling plants in SE Asia

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One of the many hundreds, if not thousands of caves located in the limestone karst of SW China. It is within such caves that we are discovering many new species of plants, very often from the nettle family.

Since 2007 I have been working with colleagues at the Chinese Academy of Sciences Guilin Institute of Botany on documenting the unusual cave flora of SW China and Guangxi. My interest stems from the fact that one of the most common groups of plants in these caves are two particular groups of nettles, members of the succulent herbaceous genera Elatostema and Pilea. It is also heavily influenced by the presence of a very knowledgeable and dedicated botanist at the Guilin Institute of Botany, Professor Wei Yi-Gang.

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Examples of some of the strange looking flower clusters in the nettle genus Elatostema, the most common group of nettles to be found growing in caves

More recently I have wanted to see whether it is possible to explain how, and when these plants occupied these ancient caves. Possible explanations are that they evolved in the caves, some of which are 15-25 million years old; alternatively that they represent plants which grew outside of the caves when the climate was different, during the last ice-age for example; lastly that they are relics of plants which grew in the forest understory outside of the caves prior to the arrival of agriculture in the area maybe 1,500 years ago. To try and answer these questions I have, together with a Masters student Alfred Gay, used DNA extracted from the leaves of the plants to look for patterns which may point to one of the three possible explanations above. Click here to see a slide show of the preliminary results.

A carpet of nettles growing in the back of one of the caves that we surveyed in SouthWest China, taken with a tripod!

Another interesting line of research would be how these nettles survive in such low light levels. In some cases 1/50th of 1% daylight! For the moment though I am focussing on documenting their diversity and describing the new species we find but in the long-term I am hoping to find collaborators to explore these other areas of research.