Mosses function as keystone species and bioindicators of forest integrity. They are sensitive to changes in atmospheric conditions and may influence ecosystem functioning out of proportion to their biomass. Yet despite their importance, there have been no studies of their ecophysiology in the Southern Appalachian Mountains (SAM). We performed light response and drying curves to determine their influence on photosynthetic responses of four native mosses, using two species from open habitats and two from forest understories. We used a custom-built cuvette attached to a Li-6800 gas exchange system to allow for better control of relative humidity. We calculated the following parameters on an areal and dry weight basis: maximum photosynthetic rate (Amax) at light saturation (LSP), dark respiration rate (Rd), light compensation point (LCP), and apparent quantum efficiency (AQE), as well as chlorophyll contents for each species. We hypothesized the following:  Understory mosses would have higher chlorophyll contents and lower a:b ratios than open-habitat mosses.  Open-habitat mosses would maintain physiologically suitable water contents for a longer period of time than understory mosses, extending their time for photosynthesis.  Open-habitat mosses would exhibit higher LCP, LSP, Amax and Rd, but lower AQE compared to understory mosses. Polytrichum juniperinum and Ceratodon purpureus, open-habitat mosses, had higher LSPs (631 and 1098 μmol m-2 s-1, respectively), than understory species (Hypnum imponens and Thuidium delicatulum at 454 and 340 μmol m-2 s-1, respectively). Understory mosses had lower Amax values between 1.1 and 1.90 μmol m-2 s-1, while open-habitat mosses were higher at 4.6 and 17.0 μmol m-2 s-1, respectively. Open-habitat species had higher Rd rates than understory species. Ceratodon purpureus had the lowest chlorophyll content and a:b ratio. Photosynthetic rates peaked at intermediate water contents (70-80 %) before declining as the mosses dried with Ceratodon purpureus maintaining carbon uptake for the longest amount of time.  Our first hypothesis was partially rejected: Open-habitat species did not have statistically higher chlorophyll content and P. juniperinum did not have a lower a:b ratio than understory species. Our second hypothesis was partially accepted: C. purpureus dried the slowest and therefore remained photosynthetically active longer than the other mosses. Our third hypothesis was mostly accepted except that open-habitat species did not exhibit lower AQE as we predicted. C. purpureus had a similar AQE to understory species, and P. juniperinum had the highest AQE. P. juniperinum also had a LCP similar to understory mosses. Open-habitat moss species may be more tolerant of warming and precipitation alterations due to climate change because they are subject to greater light and moisture stress than understory species, especially in summer months. The results of this research should provide a basis for understanding how SAM mosses are adapted to their habitats, and with additional modeling, it should be possible to calculate daily and annual carbon uptake by SAM mosses and predict impacts of future climate change on their productivity.