Tibetan grasslands haves shorter growing seasons following decades of climate change, yet biomass remains unchanged.

Satellite images show that alpine plants have been emerging earlier each year over the past few decades, but cannot show whether earlier sprouting species have migrated in or existing species are sprouting earlier.

Now, a team led by researchers from Lanzhou University has analysed 35 years of seasonal biomass data, hand-harvested from a grassland in the Tibetan Plateau, situated about 3,200 metres above sea level.

Between 1980 and 2014, the fast-growing phase of established alpine plants started earlier as springs became warmer, and finished earlier as autumns became drier, ultimately shortening the fast-growing period by one week every decade. However, annual biomass production did not change since plants grew faster, possibly due to more sunlight.

Understanding how shifts in the growing phases affect plant productivity could inform predictions of how alpine grasslands will respond to global warming.