Tree Diversity Does Not Always Improve Resistance of Forest Ecosystems to Drought

Tree Diversity Does Not Always Improve Resistance of Forest Ecosystems to Drought. Grossiord, C., Granier, A., Ratcliffe, S., Bouriaud, O., Bruelheide, H., Chećko, E., Forrester, D. I., Dawud, S. M., Finér, L., Pollastrini, M., Scherer-Lorenzen, M., Valladares, F., Bonal, D., & Gessler, A. Proceedings of the National Academy of Sciences, 111(41):14812–14815, October, 2014.
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[Significance] In the context of climate change, expected drier and warmer environmental conditions will have drastic consequences on forest functions and services and may bring about important drought-induced die-off events. Biodiversity promotes forest ecosystem performance and resistance to insect pests and diseases, but whether or not diverse forests are also better adapted to deal with drought stress remains unknown. Within our study network of 160 forest stands across Europe, we found that mixed species forests are less exposed to drought stress in some regions only. Therefore, managing forest ecosystems for high tree species diversity does not necessarily assure improved resistance to the more severe and frequent drought events predicted for the future. [Abstract] Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year ($\Delta\delta$13CS). $\Delta\delta$13CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the drought exposure of the ecosystem. However, the other three forest types were unaffected by tree species diversity. We conclude that higher diversity enhances resistance to drought events only in drought-prone environments. Managing forest ecosystems for high tree species diversity does not necessarily assure improved adaptability to the more severe and frequent drought events predicted for the future.

@article{grossiordTreeDiversityDoes2014,
  title = {Tree Diversity Does Not Always Improve Resistance of Forest Ecosystems to Drought},
  author = {Grossiord, Charlotte and Granier, Andr{\'e} and Ratcliffe, Sophia and Bouriaud, Olivier and Bruelheide, Helge and Che{\'c}ko, Ewa and Forrester, David I. and Dawud, Seid M. and Fin{\'e}r, Leena and Pollastrini, Martina and {Scherer-Lorenzen}, Michael and Valladares, Fernando and Bonal, Damien and Gessler, Arthur},
  year = {2014},
  month = oct,
  volume = {111},
  pages = {14812--14815},
  issn = {1091-6490},
  doi = {10.1073/pnas.1411970111},
  abstract = {[Significance] 

In the context of climate change, expected drier and warmer environmental conditions will have drastic consequences on forest functions and services and may bring about important drought-induced die-off events. Biodiversity promotes forest ecosystem performance and resistance to insect pests and diseases, but whether or not diverse forests are also better adapted to deal with drought stress remains unknown. Within our study network of 160 forest stands across Europe, we found that mixed species forests are less exposed to drought stress in some regions only. Therefore, managing forest ecosystems for high tree species diversity does not necessarily assure improved resistance to the more severe and frequent drought events predicted for the future.

[Abstract] 

Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year ({$\Delta\delta$}13CS). {$\Delta\delta$}13CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the drought exposure of the ecosystem. However, the other three forest types were unaffected by tree species diversity. We conclude that higher diversity enhances resistance to drought events only in drought-prone environments. Managing forest ecosystems for high tree species diversity does not necessarily assure improved adaptability to the more severe and frequent drought events predicted for the future.},
  journal = {Proceedings of the National Academy of Sciences},
  keywords = {*imported-from-citeulike-INRMM,~INRMM-MiD:c-13391273,biodiversity,climate-change,drought-tolerance,droughts,ecosystem-resilience,europe,forest-resources,global-warming,unexpected-effect},
  lccn = {INRMM-MiD:c-13391273},
  number = {41}
}

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