In the paper results of a study conducted on the base of system approach, planning multifactorial experiment and modeling of ecology-physiological feature of some sprout on the Karelia territory plant species are presented. It was installed that CO₂ gas exchange of studied samples of woody plants and sphagnum mosses have a broad optimum limits, and forecasting changes in global climate not leave for these frame. Suggestion was made that certain increasing in temperature, precipitation and an air contents CO₂ will be favourable for growing of main woody plants and will leading to intensify of a carbon assimilation of sphagnum mosses that set off a loss of carbon by peat of wetlands.