During previous years of living in Yunnan Province, I was struck by the potential that its mountains offered for ecological research. As the mountains soar upwards, the habitats rise above the treeline to grassy swards, then bare rock terrain hosting crustose lichens. At the treeline, short conifers struggle for survival in extreme conditions. Moving downwards, the vegetation transitions to deciduous, then pine-dominated forests. In southern Yunnan, the descent continues right down to the sub-tropics. What drives these changes in vegetation? Surely an important factor must be warming temperatures as one descends the mountains. While travelling in the region, I always felt like I was using a time machine, travelling from spring back to winter in the space of just a day’s journey. I often thought that the region would be ideal for an ecological experiment that involved comparisons of temperature and its impact on vegetation.

When I was offered the chance to conduct a postdoctoral research project at the Kunming Institute of Botany (KIB) of the Chinese Academy of Sciences (CAS), in Yunnan, I immediately wanted to seize the opportunity to use its elevation gradients for an ecological field experiment. Climate change has taken center stage as the major risk to global ecosystems. Thus, harnessing elevation gradients to study climate change seemed an ideal use of my resources. With research funding from the Yunnan Provincial Human Resources and Social Security Bureau and later salary funding from PIFI, I had the resources that I needed to implement an experimental plan that I had imagined for years previously. I decided that I would like to conduct a translocation experiment, in which organisms would be moved from higher to lower elevations, thus simulating potential warmer future climates.

But what should my study organisms be? Epiphytic lichens jumped out as being the ideal model organism for my study. Epiphytes are organisms that grow on trees. This makes them a good candidate for translocation, because they can be lifted from one tree and attached to another, without risking damage to root systems. By using ladders to place my translocated epiphytes high into the tree, I could keep them safely away from potential damage from browsing animals or passing people.

Lichens are especially suitable for climate change research. Because they absorb water, carbon dioxide and nutrients directly from the atmosphere, they are very sensitive to atmospheric change. There is great conservation concern that warming climates could kill sensitive lichens. Past air pollution has wiped out many lichen populations worldwide. But Yunnan has proved a haven for many lichens. Some of these are endemic to the region. Others have a wider historic distribution, but are scarce or extinct in much of their previous range. In Yunnan, lichens are recognized as being of especial importance for conservation. The endemic, rare, Yunnan snub-nosed monkey Rhinopithecus bieti eats large “beard lichens” Dolichousnea longissima as a major component of its diet. Loss of beard lichens would remove the food source of the Yunnan snub-nosed monkey. Local people utilize a range of lichens for food and medicinal use.

I selected nine species of lichens for inclusion in my experiment. I used three regions of Yunnan, in order to span an elevation gradient which descended from 4,000 m to 2,000 m above sea level. With 60 specimens of each species to be translocated, I felt confident that I would have a large enough data set to really be able to test the impact of warming. At each site I compared specimens that had been translocated at their original location, to those which had been translocated down the mountain.

After setting up the experiment in 2018, I spent three growing seasons walking through these mountains, downloading microclimate data from loggers attached to the trees, and monitoring changes in my lichen specimens. I am so grateful to the different field assistants who accompanied me on each of these trips. It was tough work for some of them to travel for the first time to such high elevations in such rugged mountains. We experienced every kind of weather on the mountains, from scorching sun to summer fogs, all-day drizzle to torrential rain and chill days. Sometimes snow prevented all access to the sites. In 2020, travel restrictions added further challenges to accessing field sites.

Through it all, the lichens continued to grow. Slowly, but surely, the differing sites had differing impacts on the specimens. By the end of 2020 it was time to make the final harvest of the experimental specimens. With a last visit to each site, I said goodbye to some beautiful mountain ridges, some stunning views and biodiverse forests.

Back at the Kunming Institute of Botany, it was time for months of laboratory work in 2021. For each of these hundreds of specimens, I would take many measures of their growth and health. Testing chlorophyll content revealed more about their health than growth data would have alone. Using LICOR equipment, I could put sections of lichen thalli (the lichen equivalent to a leaf) inside sealed chambers and see their rates of carbon dioxide exchange. This enabled for dynamic records of their photosynthetic and respiratory rates. Manipulating temperature, moisture and carbon dioxide experimental conditions allowed me to test the degree to which thalli had acclimated to the changed environmental conditions to which they had been exposed over the preceding months.

The different species differed in how changing climate had impacted their growth, health, reproduction, chlorophyll content, respiration and photosynthetic rates. There was a high level of complexity in how different environmental conditions affected the outcome. Much of the final year of my PIFI in 2022 was spent analyzing and writing up this vast data set. In the end, it became a full monograph.

Source: Fiona Worthy,

Kunming Institute of Botany,

Chinese Academy of Sciences