Molecular Soil Biology 2024, Vol.15, No.4, 193-204 http://bioscipublisher.com/index.php/msb 195 3.3 Importance of algae and lichens Algae and lichens are also vital primary producers in desert ecosystems. They are often found in biological soil crusts, which are communities of microorganisms that live on the soil surface. These crusts play a significant role in stabilizing soil, reducing erosion, and enhancing soil fertility by fixing atmospheric nitrogen and carbon (Bay et al., 2021). Algae and lichens can photosynthesize and contribute to primary production even in extreme arid conditions, making them crucial for the resilience and sustainability of desert ecosystems (Leung et al., 2020) (Figure 1). Their ability to survive and function in such environments highlights the diverse strategies employed by primary producers to thrive in deserts. Figure 1 Conceptual diagram representing the model lifestyle of a microbial community in a desert in response to hydration-desiccation cycles (Adopted from Leung et al., 2020) Image caption: It is proposed that organic carbon reserves (energy reserve hypothesis), light (light-dependent continual-energy-harvesting hypothesis), and trace gases (air-dependent continual-energy-harvesting hypothesis) are the major energy sources that allow dormant microorganisms to persist during prolonged desiccation. Abbreviations: CODH, carbon monoxide dehydrogenase; Hyd, group 1h [NiFe] hydrogenase; pMMO, particulate methane monooxygenase; PS, photosystem of aerobic anoxygenic phototroph; Rho, microbial rhodopsin; and Cox, terminal oxidase (Adopted from Leung et al., 2020) 4 Herbivores in Desert Food Chains 4.1 Types of desert herbivores Desert ecosystems host a variety of herbivores that have adapted to the harsh conditions. These herbivores can be broadly categorized into insects, rodents, and ungulates. Insects, such as various species of beetles, play a crucial role in the desert food chain by consuming plant material and aiding in decomposition (Holter et al., 2009). Rodents, including species like the spinifex hopping-mouse (Notomys alexis) and the sandy inland mouse (Pseudomys hermannsburgensis), exhibit diverse dietary preferences, often consuming seeds, invertebrates, and plant material (Murray and Dickman, 1994). Ungulates, such as the gemsbok (Oryx g. gazella) and the springbok (Antidorcas marsupialis), are larger herbivores that graze or browse on a variety of plant species (Lehmann et al., 2013). 4.2 Adaptations for water and nutrient acquisition Herbivores in desert environments have evolved several adaptations to cope with the scarcity of water and nutrients. For instance, desert ungulates like the gemsbok and springbok exhibit dietary plasticity, allowing them to switch between different types of plants depending on availability and environmental conditions (Lehmann et
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