Ecology of the Colchic temperate rainforest

In the project ClimaDyst-RainFor, we are investigating the relationships between climate and forest structure and composition in the Colchic temperate rainforests of the Lesser Caucasus in NE Turkey and the Republic of Georgia. We are conducting an integrated study combining multi-century climate reconstructions, forest disturbance histories, and forest succession models along environmental gradients in these temperate forests.

The Colchic region, located in the southeastern coast of the Black sea, comprises some of the last remnants of old-growth forests in Western Eurasia and constitute one of the few temperate rainforests in the world. Being on the on shore of the Black Sea and surrounded by high mountains (up to 5000m asl), causes this region to receive high amounts of precipitation with some locations receiving up to 4000mm such as the Mtirala National Park in SW Georgia. Temperatures are warmer than in many other temperate forests, which made the Colchic a tertiary forest refugium. And still today, it allows some subtropical taxa to develop here.

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A distinct characteristic of these forests is the dominance of well-developed broadleaf evergreen understory bushes that can reach over 5 m in height. Several species of Rhododendron dominate this stratum, but other species such as Prunus laurocerasus, Ilex or Ruscus are also present. In contrast, the only evergreen dominant canopy trees are conifers (Abies and Picea). These forests have a high degree of endemism and are seriously endangered by global change and anthropogenic disturbances (see the WWF page).

In this project, we address issues of historical forest dynamics at landscape and plot level, by reconstructing canopy disturbance events and tree recruitment and mortality through dendrochronological methods across a network of forest plots on altitudinal and precipitation gradients. We also used a forest succession model (ForClim) for simulating past and future forest dynamics and understanding the involved processes driving forest development including climate variability. Because simulations of past forest dynamics require information of past climatic conditions, we are also working on reconstructing precipitation and temperature variability for the last several centuries.

The combination of paleoecological and modelling approaches allow for investigating multiple climate effects on the ecology of these forests under changing environmental conditions. A deeper understanding of ecological processes under a combination of complex disturbances provides critical and long-term perspectives on the role of climate variability in causing vegetation changes in these ecosystems where global change is expected to lead to more frequent and intense droughts.

Preliminary analysis of the data collected across our tree-ring plot network show a diversity of species sensitivity to climate for broadleaf and conifer species. Drought sensitivity for certain species and locations have allowed us to reconstruct spring-summer precipitation over the last 250 years and show that climate observations during the recent period might underestimate the real occurrence of drought in this otherwise wet region (Martin-Benito et al. 2016).

Our investigations also have lead to the discovery and inventory of several large patches of well preserved old-growth forest dominated by trees >300 years old. These forests, however, may be endangered by logging and road development.

Publications from this project:
  1. Martin-Benito, D., Ummenhofer C.C., Köse, N., Güner, H.T., Pederson, N. 2016. Tree-ring reconstructed May-June precipitation in the Caucasus since 1752 CE. Climate Dynamics 1:17. PDF [Supplementary material]
  2. Seidl, R., Thom, D., Kautz, M., Martin-Benito, D., Peltoniemi, M., Vacchiano, G., Wild, J., Ascoli, D., Petr, M., Honkaniemi, J., Lexer, M.J., Trotsiuk, V., Mairota, P., Svoboda, M.,  Fabrika, M., Nagel, T.A., Reyer, C.P.O. Forest disturbances under climate change.  Nature Climate Change 7:395–402 [PDF]
  3.  Pederson, N., Young,A.B., . Stan, A.B.,  Ariya U., D. Martin-Benito. Accepted. Low-hanging DendroDynamic Fruits Regarding Disturbance in Temperate, Mesic Forests. In Dendroecology: Tree-ring Analyses Applied to Ecological Studies, M. Amoroso, L. Daniels, P. Baker, J. J. Camarero, Eds. (Springer).
  4. Martin Benito, D. and N. Pederson. 2016. Recent climate may have masked the vulnerability of mesic temperate forests. Science eLetter. doi: 10.13140/RG.2.1.3799.2566.
  5. Trotsiuk, V., Svoboda, M., Weber, P., Pederson, N., Klesse, S., Janda, P., Martin-BenitoD.,  Mikolas, M.,  Seedre, M., Bace, R., Frank, D. 2016. The legacy of disturbance on individual tree and stand-level above ground biomass accumulation and stocks in primary mountain Picea abies forests. Forest Ecology and Management 373 (2016) 108–115PDF
  6. Mina, M., Martin-Benito, D., Bugmann, H., Cailleret, M. 2016. Forward modeling of tree-ring width improves simulation of forest growth responses to drought. Agricultural and Forest Meteorology 221: 13-33PDF
  7. Martin-Benito, D., Anchukaitis, K., Evans, M., del Río, M., Beeckman, H., Cañellas, I. Effects of drought on xylem anatomy and water-use efficiency of two cooccurring pine species. Forests 2017, 8, 332 [PDF] [Supplementary material]

 

Funding
The research is now funded through a the CLIMADYST-RAINFOR project from the EU program FP7-PEOPLE (here). It started in 2012-2013 through a grant from LDEO Climate Center.

Team members:
Dario Martin-Benito (ETH Zurich, Switzerland)
Christof Bigler (ETH Zurich, Switzerland)
Harald Bugmann (ETH Zurich, Switzerland)
Neil Pederson (Harvard Forest, US)
Nesibe Köse (University of Istanbul, Turkey)
Marina Mosulishvili (Ilia State University, Georgia)
Interesting links:
Neil Pederson’s blog The Broadleaf Papers

[Updated August 17, 2016]

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