Phenological changes offset the warming effects on biomass production in an alpine meadow on the Qinghai-Tibetan Plateau

Phenology is an important indicator of plant responses to environmental changes and is closely correlated with biomass production. However, how changes in phenological events affect plant biomass production when exposed to changing temperature and precipitation remain unclear. We conducted a 4-year manipulative experiment of warming and precipitation addition to explore phenology-biomass interactions under climate change in a dry alpine meadow on the central Qinghai-Tibetan Plateau from 2015 to 2018. In dry and warm years, warming delayed phenology and precipitation addition advanced them. Warming decreased the biomass of Kobresia pygmaea in 2018 and the biomass of Poa pratensis in 2015, 2017 and 2018. However, precipitation addition significantly increased the biomass of Poa pratensis and Potentilla multifida in most of the experimental years. Phenological changes regulated the responses of biomass to treatments. Specifically, delay of green up of P. pratensis and delay of withering of K. pygmaea induced by warming can increase biomass production, but it can be offset by the direct negative effects of warming on biomass. Synthesis. Here we show how warming-induced drought tend to decrease the biomass production of graminoids and the negative effects of warming on the biomass of P. pratensis and K. pygmaea were partially offset by green up postponement and withering postponement respectively. Our results highlights phenology is a crucial regulator for biomass production under climate change. Hence, both direct and indirect effects of warming and precipitation addition on phenology and biomass cannot be ignored when predicting biomass responses to climate change.

Automated summary

The study showed that warming delayed phenology while precipitation addition advanced it in dry and warm years; the biomass of certain plants decreased with warming but increased with precipitation addition; phenological changes regulated the responses of biomass to treatments.