Shorter growing season linked to warmer winters on ‘the roof of the world’.
In many regions, climate change has advanced the timing of spring events, such as flowering or the unfolding of leaves. But the meadows and steppes of the Tibetan Plateau are bucking that trend — plants are starting to bloom later in spring, making the growing season shorter. This change could threaten the livelihood of the thousands of nomads who survive by raising cattle on the plateau.
“I’ve worked in the Tibetan Plateau region for 25 years,” says Jianchu Xu, an ethnoecologist at the World Agroforestry Centre in Kunming, China, and a professor at the Kunming Institute of Botany of the Chinese Academy of Sciences, who led the study, published this week in theProceedings of the National Academy of Sciences. Xu says he expected that plants on the plateau would follow the same pattern of early flowering seen elsewhere. In Europe, for instance, spring flowerings in 2000 occurred about 8 days earlier than they did in 1971 on average, and autumn events, such as changes in leaf colour, about 3 days earlier.
“But then my PhD student Haiying Yu looked at more recent data” and discovered that the opposite was the case. The finding “contradicted the linear link” that is often seen between warming temperatures and an earlier start to the growing season, Xu says.
The group used satellite data to identify the start, end and length of the growing season for the meadow and steppe vegetation of the Tibetan Plateau between 1982 and 2006, and linked it to temperature change. During this time, the mean temperature rose about 1.4 ºC on the steppes and 1.25 ºC on the lower-lying meadows.
The study showed an initial advance in the timing of the growing season or its ‘phenology’ for both the meadow and steppe for the first 15 years. But from 2000 until 2006 that trend was reversed. The net effect was a shortening of the growing season by about one month for steppe plants and three weeks for meadow vegetation.
Continue reading over at Nature News.