Background. Moss cover plays a decisive role in increasing soil moisture in forest ecosystems. Bryophytes with high water content can significantly reduce water evaporation from the soil surface and retain it for an extended time. Under the influence of environmental conditions, mosses change the shape and organization of moss turfs thus regulating the efficiency of moisture absorption and retaining. Therefore, it is essential to establish the differences in the water exchange strategy of epigeic dominant moss species depending on the environmental conditions in reserved and anthropogenically disturbed forest ecosystems. Materials and Methods. The research was carried out using the dominant epigeic, typical forest moss species Plagiomnium cuspidatum (Hedw.) T. J. Kop. and P. ellipticum (Brid.) T. J. Kop. from experimental plots of forest ecosystems, which differed in water and temperature regimes and light intensity. We determined the peculiarities of the influence of adaptations of moss turf morphological structure, individual plant’s physiological functional traits, and their metabolic osmoprotective changes based on the leading indicators of their water exchange (coefficients of water retention, water recovery, and drought resistance). Results. It was established that humidity and light intensity in forest ecosystems changed the shape and organization of moss turfs, i.e., the height of individual shoots in the turf and the density and size of leaves. The predominance of the generative or vegetative type of moss reproduction led to significant changes in the morphology of shoots, physiological functional traits of plants, and the density of the turf structure, which was regulated due to the increase in airstream turbulence and wind penetration, absorption and evaporation of water. The hydration of moss tissues was maintained due to the rise in the total carbohydrate content as well as the soluble fraction content primarily in the vegetative shoots. Conclusions. Mosses adapted to variable microclimatic conditions of forest ecosystems due to endohydricity and water retention mechanisms in external capillary spaces, i.e., changes in height, shape, and density of turfs, shoot morphology, various ratios of fertile to sterile plants, and their physiological functional traits. The internal regulation of water potential of cells was ensured by an increased concentration of osmoprotectors (carbohydrates, primarily their soluble fraction).