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Harvard Forest Symposium Abstract 2018

  • Title: Climate constraints on tree growth across a wide climatic gradient in the temperate forests of the Western Caucasus
  • Primary Author: Dario Martin Benito (Columbia University in the City of New York)
  • Additional Authors: Christof Bigler (ETH Zurich); Harald Bugmann (ETH Zurich); Mehmet DOĞAN (Not specified); Nesibe Köse (Not specified); Marine Moshulishvili (Ilia State University); Neil Pederson (Harvard Forest)
  • Abstract:

    The Caucasus is considered a global biodiversity hotspot and includes a wide diversity of temperate forest types, from xeric to mesic and rainforests, but little is known about their vulnerability to climate change. Here, we identify the major climate constraints and quantify their relative effects on tree growth. We used a new network of 35 tree-ring width chronologies from eight tree species across an elevational gradient of more than 2000m. Using correlation functions, we identified the major climate factors affecting tree growth at monthly and seasonal scales and their changes over time. To explore common patterns of growth responses in these species, we used Self Organizing Maps, a type of artificial neural network. Despite large differences in elevation, trees of most species responded with reduced growth to May-June drought. As expected, drought was particularly detrimental at warm low-elevation sites. At high elevations, growth of conifers was also limited by cold winters and summers. Important species-specific growth responses to climate were also evident. High elevation Fagus orientalis, for example, had little drought stress but responded positively to summer warmth. Climate growth relationships were stable over time at most sites, except for where temperature limited growth. At those sites, the positive responses to summer and winter temperatures were reduced over the last few decades. Growth response to precipitation among species were more similar than they were to temperature even in temperate rainforests, adding more evidence that mesic forests are vulnerable to drought. Productivity of high-elevation coniferous forests, limited by summer drought and cold temperatures, will depend on the balance between temperature and precipitation. If, as expected, climate change results in extended climatic gradients, conservation of these forests will become more essential for the region.

  • Research Category: Regional Studies; International Research Projects; Historical and Retrospective Studies