Alpine Indicators & Ecotones
Alpine meadows on the Tibetan Plateau (credit: Biological Conservation)
Plant communities growing in ecological transition zones, like timberlines, are recognized as ecotones. These locations are where you can directly see the changes in plant density and composition. Ecotones represent the tension zones and the boundaries between different ecosystems and are ideal locations to view the process in real time. Plants are now responding to changing climate regimes by 'marching' upwards on mountains and across meadows. In some places, these movements have been rapid.
research in alpine meadows on the Tibetan plateau has been conducted by ecologists from Dartmouth University in collaboration with Chinese and Tibetan associates. Their studies have shown shrubs have moved rapidly colonized the meadows due to dramatic changes in temperature and soil conditions on the high plateau, the so-called Third Pole. In less than 30 years, lush meadows, once blanketed in herbs and grasses, have filled in and become dominated by species woody shrubs. The results of this alpine research appeared in the journal Biological Conservation.
Alpine meadow, Tibetan Plateau (credit: Wikipedia)
The lead author Jodi Brandt commented:"nearly 40% of the alpine meadows we studied had converted from meadows into shrub-lands at the study sites between 1990 and 2009" representing a biological timeline of less than 20 years.
Closer to the home, recent investigations have shown similar responses to plant populations on mountains in the western USA. The iconic Bristlecone pines, Methuselah trees alive 1000 years before the birth of Jesus, as well as the small alpine rodent the pika, have responded to warming temperatures as well. Both species may be at their environmental tolerance limits and won't be able to migrate any higher leading to decline in their populations.
Ecological boundaries are good indicators of the effects of a changing environment. We typically think of landscape changes as being a slow, almost glacial process. What has been observed in Tibet, and in our own high mountain ranges, has been compared to watching an ice cube melt in a glass of hot water. WHB