Juntao Zhu, Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences, discusses his article: Loss of resource-conservative species affects plant phylogenetic and functional structure under long-term snow addition
The alpine meadows on the Tibetan Plateau are unique ecosystems shaped by a harsh climate and traditional yak grazing. But as the climate changes, these areas are seeing more extreme snow events. We wanted to know how plant communities respond when faced with more snow and continuous grazing over a long period of time.
What We Did: A 16-Year Experiment
To find the answer, we began a field experiment in 2009. We set up plots in an alpine meadow in Namtso village, central Tibet, China, and applied four different treatments: some plots were left as a control, some had yak grazing, some had extra snow added each spring to mimic a heavy snowstorm, and some had both snow addition and grazing. For 16 years, we tracked the plant species in each plot to see what changed.
Key Finding 1: More Snow Was the Biggest Driver of Change
After analysing our long-term data, we found that the added snow had a much stronger effect on the plant community than grazing. The extra snow melts in the spring, providing more water to the soil. This extra moisture gave a big advantage to the dominant plant in the meadow, a sedge called Kobresia pygmaea. It grew better and started to crowd out its neighbours, leading to an overall decline in the number of plant species.
The species that were lost were mostly “resource-conservative” plants. These are species adapted to stress, with traits like tough, dense leaves (high leaf dry matter content) that help them conserve resources. In the wetter, more resource-abundant conditions created by the snow, their slower survival strategy was no longer the most effective. Instead, faster-growing “resource-acquisitive” species, which could better capitalize on the improved conditions, held the advantage.
Key Finding 2: A Surprising Twist in the Community’s “Family Tree”
To understand the changes more deeply, we didn’t just count the species that disappeared; we also investigated their evolutionary relationships. We constructed a family tree to see if the losses were random or if specific branches of the tree were more vulnerable than others. We found that the species being lost under the snow addition treatment were often close relatives of the species that survived.
Imagine a large, dense bush representing the community’s family tree. Before our experiment, the branches (species) were mixed, with some clustered together and some far apart, creating a random structure. The added snow specifically targeted and removed clusters of species that were closely related to the resident community, and these were precisely those same conservative species. With these clusters gone, the remaining branches naturally seemed more spread out. As a result, the plant community’s phylogenetic structure became “overdispersed,” meaning the remaining species were, on average, more distantly related to each other than before.
Why This Research Matters
This result is important because it shows that environmental changes do not just remove species randomly. Interestingly, the community’s functional trait structure remained clustered and relatively stable. This suggests that to survive in the harsh alpine environment, plants must have a very similar set of functional traits, even if they come from very different evolutionary branches.
The loss of conservative species is a concern because these plants play a key role in ecosystem functions, like how nutrients are cycled. Our 16-year study provides crucial evidence that changes in snow patterns can reshape these important ecosystems. To protect them, we need to understand exactly how and why species dynamics are changing.
