**2.2 Climate sensitivity analysis**

The authors evaluated biomass for the total forest, *Larix* spp., and evergreen conifers at 372 sites across Siberia in response to changes in temperature and precipitation, and to the inclusion of European Larch (*Larix decidua)* (Table 1).


Table 1. A total of 12 treatments including the base condition, combinations of temperature and precipitation change and *Larix decidua* addition to the available species pool were used.

temperature and update soil water content. In particular, at each site, the model's climate inputs are drawn from a statistical distribution of monthly values for minimum and maximum mean temperature and precipitation that is derived from 60 years of data recorded at local weather stations (NCDC 2005a, 2005b). The model also uses values for soil field capacity, and soil carbon and nitrogen from Stolbovoi and McCallum (2002) for each

The birth, growth, and eventual death of individual trees are determined in response to competition for light and local site parameters such as soil moisture and nutrient availability, which are updated annually with bio-environmental conditions and available nutrients. Complete model processing details are available in Yan and Shugart (2005). Fifty-eight different tree species are included in FAREAST simulations, and can be grouped into ten genera (*Abies* spp., *Betula* spp, *Larix* spp., *Picea* spp., *Pinus* spp. *Populus* spp., *Tilia* spp., *Quercus* spp., *Fraxinus* spp., and *Ulmus* spp.) and two collections of less common species (other deciduous and other coniferous). These species represent the genera that dominate Northern Eurasian forests, and include species that were added when the original geographic area of interest for the model in Yan and Shugart (2005) was expanded to cover all of Russia (Shuman and Shugart 2009). Twenty-five parameters describe each species and determine which species has an advantage in terms of competition for light or nutrients, or tolerance to lack of water. Tree growth and regeneration is limited by functions describing local light, temperature, nutrients and drought dynamics determined through interaction and annual update of soil water and available carbon and nitrogen. Tree mortality each year is a consequence of a Monte Carlo realization of individual species probability of mortality plus added probability of mortality on that individual from stress or disturbances. Successional dynamics are therefore a result of competition between tree species for light and nutrients, as well as limitations to growth imposed by local environmental conditions. Each site uses a unique species list drawn from species range information created in ESRI ArcGIS (2008) using range information adapted from Nikolov and Helmisaari (1992) and Hytteborn et al., (2005). At each site, 200 independent twelfth-hectare plots were simulated for 500 years and the modeled biomass values were averaged for each species in each year of the model run. This average produces a landscape-level approximation of succession, which

includes the natural disturbance associated with the death of individual trees.

The authors evaluated biomass for the total forest, *Larix* spp., and evergreen conifers at 372 sites across Siberia in response to changes in temperature and precipitation, and to the

Treatments used in climate sensitivity analysis Change in temperature Base + 4 degrees Change in precipitation Base 10% Introduction of *Larix decidua* Base + *Larix decidua* Table 1. A total of 12 treatments including the base condition, combinations of temperature and precipitation change and *Larix decidua* addition to the available species pool were used.

**2.2 Climate sensitivity analysis** 

inclusion of European Larch (*Larix decidua)* (Table 1).

site.

*L. decidua* has a higher tolerance for an increased number of warm days than do species of larch native to Siberia and the RFE. This gives *L. decidua* an advantage over other species of larch for establishing in areas with warmer temperatures. The climate scenarios used in this analysis are based on the moderate predictions of temperature and precipitation increase that are made by global climate models for portions of Eurasia (IPCC 2007). For the base scenario, no changes are made to the distributions of monthly temperature and precipitation values derived from historical records. The remaining climate scenarios employ a linear increase in temperature or precipitation or both from the start of simulation, year zero, to year 200 of the simulation. This is followed by an additional 300 years of simulation during which the climate stabilizes around the conditions attained in year 200. For each of the 12 treatments, biomass (tC ha-1) values were summed across species to obtain values for the total forest, *Larix* spp., and evergreen conifers at each site.

Fig. 1. Multi-scale analysis included data for 372 sites at the continental scale (a) and sub-sets from six regions **(b)** within northwest Siberia, the central border of Siberia, two sets from southern Siberia, and two eastern sets from high diversity areas in the Amur region of the Russian Far East

A non-parametric factorial ANOVA was performed at 10 year intervals and used to assess differences in total forest, *Larix* spp., and evergreen conifer biomass (tC ha-1) between model runs that employed one of the 11 different climate and *L. decidua* treatments and the base climate scenario (SAS v. 9.1, SAS Institute Inc. 2002). This analysis was completed at the continental scale for a total of 372 sites (Figure 1a), and for six regional subsets (Figure 1b) including northwest Siberia (NW Siberia), the central border of Siberia (Central Siberia), two sets from southern Siberia (E Irkutsk, and W Irkutsk), and two sets from the Amur region of the Russian Far East (N RFE, and SW RFE). These regions represent areas with a broad range of climatic conditions and offer a representative sample of different forest types. Within the six regional subsets, local scale results were evaluated for changes in successional dynamics resulting from the climate or *L. decidua* treatments.
