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Biological soil crusts are a diverse soil surface community, prevalent in semiarid regions, which function as ecosystem engineers and perform numerous important ecosystem services. Loss of crusts has been implicated as a factor leading to accelerated soil erosion and other forms of land degradation. To support assessment and monitoring efforts aimed at ensuring the sustainability of rangeland ecosystems, managers require spatially explicit information concerning potential cover and composition of biological soil crusts. We sampled low disturbance sites in Grand Staircase?Escalante National Monument (Utah, USA) to determine the feasibility of modeling the potential cover and composition of biological soil crusts...
Seasonal differences have been observed in the ability of desiccated mosses to dissipate absorbed light energy harmlessly into heat. During the dry summer season desiccation-tolerant mosses were more protected against photo-oxidative damage in the dry state than during the more humid winter season. Investigation of the differences revealed that phototolerance could be acquired or lost even under laboratory conditions. When a desiccated poikilohydric moss such as Rhytidiadelphus squarrosus is in the photosensitive state, the primary quinone, Q(A), in the reaction centre of photosystem II is readily reduced even by low intensity illumination as indicated by reversibly increased chlorophyll fluorescence. No such reduction...
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Desertification is a global problem, costly to national economies and human societies. Restoration of biological soil crusts (BSCs) may have an important role to play in the reversal of desertification due to their ability to decrease erosion and enhance soil fertility. To determine if there is evidence that lower fertility may hinder BSC recolonization, we investigated the hypothesis that BSC abundance is driven by soil nutrient concentrations. At a regional scale (north and central Colorado Plateau, USA), moss and lichen cover and richness are correlated with a complex water?nutrient availability gradient and have approximately six-fold higher cover and approximately two-fold higher species richness on sandy soils...
The relationship between photosynthetic energy conservation and thermal dissipation of light energy is considered, with emphasis on organisms which tolerate full desiccation without suffering photo-oxidative damage in strong light. As soon as water becomes available to dry poikilohydric organisms, they resume photosynthetic water oxidation. Only excess light is then thermally dissipated in mosses and chlorolichens by a mechanism depending on the protonation of a thylakoid protein and availability of zeaxanthin. Upon desiccation, another mechanism is activated which requires neither protonation nor zeaxanthin although the zeaxanthin-dependent mechanism of energy dissipation remains active, provided desiccation occurs...
BACKGROUND AND AIMS: The basic parameters of water relations were measured in Sphagnum mosses. The relationships of these parameters to the photosynthetic response to desiccation and the ecology of these mosses were then tested. METHODS: The water relations parameters of six Sphagnum species (mosses typical of wet habitats) and Atrichum androgynum (a moss more typical of mesophytic conditions) were calculated from pressure-volume isotherms. Photosynthetic properties during and after moderate desiccation were monitored by chlorophyll fluorescence. KEY RESULTS: When desiccated, the hummock-forming species S. fuscum and S. magellanicum lost more water before turgor started dropping than other sphagna inhabiting less...
    map background search result map search result map Spatial Modeling of Biological Soil Crusts to Support Rangeland Assessment and Monitoring Evidence for micronutrient limitation of biological soil crusts- Importance to arid-lands restoration Spatial Modeling of Biological Soil Crusts to Support Rangeland Assessment and Monitoring Evidence for micronutrient limitation of biological soil crusts- Importance to arid-lands restoration