Taiga

Taiga is a type of environment that is commonly found in cold northern Cerilia. It mainly has coniferous plants growing in soils that aren't as nutrient rich as those in temperate zones. Depending on the climate, some broadleaf trees are scattered amongst the firs, e.g. birch, aspen, willow, rowan, oak, maple, and elm. Grass is uncommon where tree cover blocks sunlight or pine needles acidify the soil. Where meadows exist, grasses and herbs grow. Some of these herbs are favored by druids for their uses. Lichen and moss are common on rocks and trees even under difficult conditions.

The Northlands, where much of the taiga is found, is a largely a trackless wilderness, where travel is difficult or impossible without a skilled guide. In summer, travel is on foot or horse, while during winter, Rjurik who must travel are forced to do so by sleigh, dog-sled, skis, or snowshoes. Even then, traveling in winter is a tricky and potentially dangerous proposition.
General rules for forests can be found on pg 87 of the Dungeon Master's Guide (D&D 3.5). Overlooked among these hazards can be forest fires, which can be extremely dangerous in cold weather, because of the risk of sweating and then freezing.
Note that the sample forest encounter table (EL 6) is for temperate climates and includes creatures not suitable for taiga. Using the guide on page 95 of the DMG, this encounter table may be more suitable.
There is a 5% (or 1 in 20) change of an encounter each hour in desolate areas, such as most level 1 or 0 provinces. Near to settlements or in level 2 or 3 provinces those chances climb to 8% (or 1 in 12). Gundviir, Djaalfund, Mandal, and Kopindal in the Rjurik lands might see encounters as high as a 10% chance per hour.
Special rules for taiga can be found on pg 26 of Frostburn, the D&D 3.5 cold weather supplement. They include a table for terrain types, and special rules for bogs, and taiga undergrowth. Other terrain types described in this book are also useful for areas within or near to a taiga type forest. Some encounters in Frostburn are also particularly appropriate to normal encounters in taiga.

Details about these additional encounters are only found in the Frostburn supplement.