Effects of four important gradients on the distribution and abundance of Sphagnum and other bryophyte genera were studied on 29 peatlands located along a gradient from the Queen Charlotte Islands, British Columbia to central Alberta. Data obtained from permanent weather stations were used to divide the climate in the study area into four zones: hyper-oceanic, oceanic, sub-oceanic, and sub-continental. Based on surface water chemistry, the peatlands studied varied from bogs to rich fens.

Sphagnum species can be divided into 4 groups based on their distribution and abundance along climatic and surface water chemistry gradients: oceanic bog and poor fen species, widespread poor fen species with sub-continental tendencies,widespread species, and moderate-rich fen species. The height of the moss above the water table and overstory shade did not affect the geographical distribution of most species. Height relative to the water table only affected the distribution of species found at either end of the microtopographic gradient.

Ecotope dimensions of 11 Sphagnum species were measured on climatic, water chemistry, height of the capitulum above the water table and overstory shade gradients. Dispersal of species optima indicate that climate and height relative to the water table are extensively partitioned by Sphagnum species. Only bog and poor fen habitats are partitioned on a complex waster chemistry gradient that includes Ca, Mg, Na, K, Fe, Mn, and H concentrations in the surface waters. The overstory shade gradient was not partitioned by mire Sphagnum species.

Among 6 elements analysed (Ca, Mg, Na, K, Fe, Mn,), only Ca and Mg concentrations in mire surface waters are significantly related to concentrations in hummock-forming Sphagnum species. Climatic conditions that produce moisture deficits increase effects of Ca and Mg in surface waters on concentrations of these elements in the moss plants.

Increases in length and weight of pool, lawn, and carpet Sphagnum species that were grown in waters collected from different climatic zones vary along corrected conductivity and amonium gradients. Lack of suitable habitats does not appear to limit the geographical distribution of such poor fen species as Sphagnum lindbergii, S. papillosum, and S. jensenii, since they grew significantly (p $<$ 0.05) in waters obtained from each of the climatic zones. However, growth of the moderate-rich fen species Sphagnum teres may be restricted on many hyper-oceanic mires by low k$\sb{\rm corr}$ values ($<$10 $\mu$S) and low NH$\sb4\sp+$ concentrations ($<$2 mg/L) in the surface waters.