Sphagnum mosses in a changing UV-B environment: A review

Sphagnum mosses are the key regulating component in peatland ecosystems. Although their importance in sustainability of peatlands and overall impact on the Earth's carbon, nutrient and hydrological balance are well recognised, our knowledge of the effects of enhanced ultraviolet B (UV-B) radiation on peat mosses is insufficient. Analogous studies of the subject often bear contrasting results, and the following review represents our effort to untangle this apparent confusion. The review summarises current knowledge of the influence of changing UV-B radiation on morphology, chemistry and physiology of Sphagnum mosses, and discusses the methodological challenges faced by the researchers studying UV-B effects. Solar UV-B radiation regulates growth patterns in peat mosses, thus influencing the environment within the Sphagnum blanket for microorganisms and small invertebrates. Physiological changes, such as the increase in membrane permeability, as well as magnesium,calcium and potassium leakage, and decrease in water-holding capacity are important UV-B responses of Sphagna. UV-B-induced changes in photosynthetic pigments and UV-absorbing compounds of peat mosses are species-specific, and depend on UV radiation dose. The responses seen as a change in the phenolic content are mostly transient and not easily detected. The inconsistencies in findings show that the Sphagnum genus should not be considered as a homogeneous group in terms of UV-B responses; instead, comparative research on individual species is required. Therefore, we highlight the necessity for further, more detailed research into Sphagnum responses to UV-B; both as a single driver and in combination with other globally-changing environmental factors.