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Terrestrial and aquatic responses to climate change and human impact on the southeastern T ibetan P lateau during the past two centuries
Author(s) -
Wischnewski Juliane,
Kramer Annette,
Kong Zhaochen,
Mackay Anson W.,
Simpson Gavin L.,
Mischke Steffen,
Herzschuh Ulrike
Publication year - 2011
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2011.02474.x
Subject(s) - plateau (mathematics) , climate change , ecology , diatom , holocene , physical geography , ecosystem , global warming , detrended correspondence analysis , environmental science , environmental change , terrestrial ecosystem , population , geography , geology , oceanography , habitat , biology , mathematical analysis , mathematics , demography , sociology
Rapid population growth and economic development have led to increased anthropogenic pressures on the T ibetan P lateau, causing significant land cover changes with potentially severe ecological consequences. To assess whether or not these pressures are also affecting the remote montane‐boreal lakes on the SE T ibetan P lateau, fossil pollen and diatom data from two lakes were synthesized. The interplay of aquatic and terrestrial ecosystem response was explored in respect to climate variability and human activity over the past 200 years. Nonmetric multidimensional scaling and Procrustes rotation analysis were undertaken to determine whether pollen and diatom responses in each lake were similar and synchronous. Detrended canonical correspondence analysis was used to develop quantitative estimates of compositional species turnover. Despite instrumental evidence of significant climatic warming on the southeastern Plateau, the pollen and diatom records indicate very stable species composition throughout their profiles and show only very subtle responses to environmental changes over the past 200 years. The compositional species turnover (0.36–0.94 SD ) is relatively low in comparison to the species reorganizations known from the periods during the mid‐ and early‐ H olocene (0.64–1.61 SD ) on the SE P lateau, and also in comparison to turnover rates of sediment records from climate‐sensitive regions in the circum arctic. Our results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem in our study area. Synergistic processes of post‐Little Ice Age warming, 20th century climate warming and extensive reforestations since the 19th century have initiated a change from natural oak‐pine forests to seminatural, likely less resilient pine‐oak forests. Further warming and anthropogenic disturbances would possibly exceed the ecological threshold of these ecosystems and lead to severe ecological consequences.