(Belnap et al., 2003). These communities provide critical ecosystem services such as reducing erosion, increasing soil fertility and water infiltration, and even facilitating germination of native seeds while reducing germination of large-appendaged exotic seeds (Harper and Belnap, 2001; Belnap, 2002, 2006; Belnap et al., 2003; Hawkes, 2004; Li et al., 2005; Su et al., 2007). Mosses play important roles in biocrusts, such as contributing to both soil stability via rhizoids and soil formation via capture of nutrient- rich fine particles (Seppelt et al., 2016). Moreover, in some dryland ecosystems, biocrust mosses control the overall carbon balance by reaching peak photosynthetic activity during winter months when surrounding shrubs are dormant (Zaady et al., 2000; Jasoni et al., 2005). However, Mojave Desert mosses are faced with being quiescent during hot, dry summers and are thus unable to use any of the intense solar radiation for photosynthesis (Stark, 2005). Furthermore, while many plants have morphological mechanisms to reduce absorption of excess light, such as altering leaf angle or the production of a waxy cuticle, mosses both lack thick cuticles (Jeffree, 2007) and are unable to alter leaf angle once desiccated. Although their dry state is often a curled state thought to be a protective adaptation for minimizing light absorption (Zotz and Kahler, 2007), it may not alone be enough to protect desert mosses from the long-term excess light and intense UV radiation they face while quiescent.
Studies on UV protection in mosses have been limited with most focus on Antarctic mosses and UV-B supplementation in greenhouses or growth chambers (Searles et al., 2001; Gwynn-Jones et al., 1999; Searles et al., 1999; Lud et al., 2002; Martínez-Abaigar et al., 2003; Newsham, 2003; Green et al., 2005; Núñez-Olivera et al., 2005; Robinson et al., 2005; Dunn and Robinson, 2006; Björn, 2007; Turnbull et al., 2009). Thus, there is a need for a better understanding of the effects of natural levels of UV radiation in a field setting. While nearly all mosses tested in nature appear to be
Accepted Manuscript
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