Alpine Indicators & Ecotones
Alpine meadows on the Tibetan Plateau (credit: Biological Conservation)
Plant communities in ecological transition zones, like timberlines, are recognized as ecotones. In these locales you can observe the changes in plant density and composition directly. These zones represent the boundaries between two ecosystems and are ideal for viewing and conducting ecological competition in real time. Plants are now responding to changing climatic regimes by 'marching' upwards on mountains and across meadows. In some places, these movements have been quite rapid.
Research in alpine meadows on the Tibetan plateau has been conducted by researchers from Dartmouth University in collaboration with Chinese and Tibetan associates. Their botanical studies have shown shrubs have rapidly colonized alpine meadows due to dramatic changes in temperature and soil conditions on the high plateau, the Earth's 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 of woody shrubs. This ecological research has been conducted by the Silvis Lab for Spatial Analysis for Conservation and Sustainability at the University of Wisconsin.
Alpine meadow, Tibetan Plateau (credit: Wikipedia)
Jodi Brandt, one of the investigators 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, 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. However, these two species may be at the summit of their mountain top environments and won't be able to migrate higher. Decline or extinction of their populations may result.
Ecological boundaries are good locations to follow the effects of a warming world. We typically think of landscape changes as being a slow, almost a glacial process. What has been observed in Tibet, and in our own high mountains, has been compared to watching an ice cube melt in a glass of hot water. WHB