Biological soil crusts—communities of mosses, lichens, and microbes—stabilize soils, retain water, and regulate carbon in drylands. While these communities are well studied as a whole, less is known about how individual members respond to changing conditions. This project focuses on Syntrichia, a dominant desert moss genus, examining how drought, seasonality, and rainfall patterns influence its photosynthetic performance across time (seasons) and space (two California deserts).