A constant hazard in the Tibetan Plateau – yakjam
I’ve been out of the social-media loop for a few weeks, hence the abnormally long interval since my last post. As you might recall, I’ve been travelling overseas and most recently blogged from Monterey, California where I was attending a symposium on invasion genetics.
The next phase of my travels couldn’t have been more different.
The reason I couldn’t access the blog was because I was well behind the Great Firewall of China. I was, in fact, in the Tibetan region of Gansu and Sichuan Provinces in western China for most of the last 10 days. While I’ve travelled to China many times before, this was by far the most evocative, interesting and unique experience I’ve ever had in this country. Reflecting on the past 10 days while waiting in Hong Kong for my flight back to Australia, I am still reeling a little from what I saw.
Top bloke: Jiajia Liu of Fudan University
What the hell was I doing at 3500-4000 m elevation on the Tibetan Plateau? Good question. I have been most fortunate to be included in a crack team of Chinese ecologists who have designed and implemented a most impressive set of experiments in plant community ecology. The team, led by Professor Shurong Zhou and Dr. Jiajia Lui of Fudan University, has been working relentlessly to put together some of the sexiest plant ecology experiments going in China.
Having now so far published two papers from the some of the experiments (see here and here), my Chinese colleagues thought it was high time I visited the famous site. Situated at 3500 m in the Tibetan region of Gansu Province in western China, the Lanzhou University research station Azi Shi Yan Zhan is about a 20-hectare area of meadow fenced off from the grazing of the ubiquitous domestic yaks herded by the local Tibetans. If that sounds pretty exotic, let me assure you that it is.
Traditional Tibetan yak herder tent dwellings
The first thing that strikes an ecologist about the region is just the vastness of it all. Hundreds of kilometres in every direction of valleys and mountains overgrazed by yaks and sheep, which was likely mostly forested many hundreds or even thousands of years ago (based on the odd valley or mountain that has been spared the grazing pressure). While it was certainly cool to see that most inhabitants of the region were still living a traditional lifestyle in tents while tending to their rather beautiful and lucrative livestock (apparently a full-grown yak sells for 10,000 ¥, or about AU$1800), it was disconcerting all the same to witness the scale of the ecological devastation.
You can therefore appreciate that a 20-hectare plot that hasn’t been grazed for 20 years is a thing of exquisite beauty in comparison. Not only is the meadow vegetation, which has come back mainly from the in situ seed bank, beautiful – it is also wonderfully diverse. There are well over 60 species in the small site, and another 200 or so in the general region. A single 1.5-m quadrat can contain over 40 species. I was also lucky enough to see Chinese red pikas (Ochotona erythrotis), Himalayan marmots (Marmota himalayana) and Himalayan vultures (Gyps himalayensis).
The beautiful Saussurea stella (Asteraceae)
The impressive plant diversity isn’t all. The experiments themselves are impressive to say the least. Not only have Zhou & Liu’s team measured quadrat diversity, they have constructed a full molecular phylogeny of all species, have measured about 20 different functional traits, have clipped all individuals to measure productivity, and have systematically removed specific functional groups in a fully replicated design to test the various determinants of community productivity, structure and resilience. It is, in a brief, a staggering achievement, and we have only begun to scrape the surface of the this dataset’s richness.
So far, we’ve determined that biomass and stem density explain the most variation in species aggregation patterns, and that phylogenetic diversity and single functional traits explain the most variation in productivity. The cool thing about these results is that they confirm what up until now had only been measured in artificial plantation experiments. With natural communities only modified by functional composition, these experiments provide powerful information about how species diversity maintains ecosystem function.
Temperature-raising pyrex panes mimic climate change effects
Even cooler, Zhou & Liu have another experiment at the same site where they have manipulated temperature to mimic short-term climate change, and nutrient concentrations to mimic fertiliser additions. The results are so far preliminary, but it appears that these natural communities confirm the observation that species asynchrony is one of the best predictors of biomass stability, and that both warming and fertilisers break this down. We’re working on that particular manuscript at the moment.
In essence, this is a group to watch, with some punchy papers on ecosystem processes guaranteed. It was a pleasure to be treated to such a wonderful region by my most gracious and generous hosts. I hope to return the favour some day soon. 谢谢我的朋友
