Photosynthesis and Water Relations of Lichen Soil Crusts: Field Measurements in the Coastal Fog Zone of the Namib Desert

Lange, O. L.; Meyer, A.; Zellner, H.; Heber, U.

doi:10.2307/2389909

Cited by 167 publications

(116 citation statements)

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“…Acclimation occurs due to ambient light also (Green et al, 1997). Even their water balance can acclimate to different conditions and, for soil crust lichens from the Namib Desert, it was not only shown that minimum thallus water content (WC) allowing positive NP can be extremely low (Lange et al,1994), but also that photosynthesis is reactivated by water vapour uptake alone (Lange et al, 2006). Finally, Poorter et al (2012) showed that carbon partitioning acclimates to different habitat conditions and patterns of assimilate allocation are known to serve as excellent indicators for growth performance in vascular plants.…”

Section: Introductionmentioning

confidence: 99%

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

et al. 2014

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Biological soil crusts (BSC) are the dominant functional vegetation unit in some of the harshest habitats in the world. We assessed BSC response to stress through changes in biotic composition, CO 2 gas exchange and carbon allocation in three lichen-dominated BSC from habitats with different stress levels, two more extreme sites in Antarctica and one moderate site in Germany. Maximal net photosynthesis (NP) was identical, whereas the water content to achieve maximal NP was substantially lower in the Antarctic sites, this apparently being achieved by changes in biomass allocation. Optimal NP temperatures reflected local climate. The Antarctic BSC allocated fixed carbon (tracked using 14 CO 2 ) mostly to the alcohol soluble pool (low-molecular weight sugars, sugar alcohols), which has an important role in desiccation and freezing resistance and antioxidant protection. In contrast, BSC at the moderate site showed greater carbon allocation into the polysaccharide pool, indicating a tendency towards growth. The results indicate that the BSC of the more stressed Antarctic sites emphasise survival rather than growth. Changes in BSC are adaptive and at multiple levels and we identify benefits and risks attached to changing life traits, as well as describing the ecophysiological mechanisms that underlie them.

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Section: Introductionmentioning

confidence: 99%

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

et al. 2014

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“…Photosynthetic activity in BSCs can be triggered by very small amounts of moisture, including dew and fog [13,14], and can be sustained over a wide range of moisture conditions [15]. Elbert et al [9] estimate the median net uptake of C by BSCs in drylands to be 16 g m 22 yr 21 with a total annual net C uptake of 1.0 Pg yr 21 .…”

Section: Introductionmentioning

confidence: 99%

Impact of grazing intensity on seasonal variations in soil organic carbon and soil CO ₂ efflux in two semiarid grasslands in southern Botswana

Thomas

2012

Phil. Trans. R. Soc. B

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Biological soil crusts (BSCs) are an important source of organic carbon, and affect a range of ecosystem functions in arid and semiarid environments. Yet the impact of grazing disturbance on crust properties and soil CO 2 efflux remain poorly studied, particularly in African ecosystems. The effects of burial under wind-blown sand, disaggregation and removal of BSCs on seasonal variations in soil CO 2 efflux, soil organic carbon, chlorophyll a and scytonemin were investigated at two sites in the Kalahari of southern Botswana. Field experiments were employed to isolate CO 2 efflux originating from BSCs in order to estimate the C exchange within the crust. Organic carbon was not evenly distributed through the soil profile but concentrated in the BSC. Soil CO 2 efflux was higher in Kalahari Sand than in calcrete soils, but rates varied significantly with seasonal changes in moisture and temperature. BSCs at both sites were a small net sink of C to the soil. Soil CO 2 efflux was significantly higher in sand soils where the BSC was removed, and on calcrete where the BSC was buried under sand. The BSC removal and burial under sand also significantly reduced chlorophyll a, organic carbon and scytonemin. Disaggregation of the soil crust, however, led to increases in chlorophyll a and organic carbon. The data confirm the importance of BSCs for C cycling in drylands and indicate intensive grazing, which destroys BSCs through trampling and burial, will adversely affect C sequestration and storage. Managed grazing, where soil surfaces are only lightly disturbed, would help maintain a positive carbon balance in African drylands.

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“…The compilation of area-based net photosynthesis in different BSC types showed a wide range of maximum CO 2 uptake rates equivalent with deposition fluxes between -0.11 and -11.5 µmol m −2 s −1 (Lange, 2001). However, previous field studies investigating the gas exchange of BSC used mostly samples either on naturally loose and inert substrate, such as gravel, or separate samples in Petri-dishes (e.g., Lange et al, 1994;Levi et al, 1981;Kappen et al, 1980;Zaady et al, 2000). Separation of soildwelling BSC from the underlying soil compartment may eliminate a major factor influencing their CO 2 exchange.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, a rainfall gradient of 200-250 mm exists from the coastal region to the arid core of the Negev Desert, Israel. Dew precipitation accounts on average for 33 mm or 25-30% of the annual precipitation in the gravel desert of the Negev highlands (Evenari, 1981), and it was concluded that dew and fog play a particular role for BSC activity (e.g., Lange et al, 1994;Veste et al, 2001). However, significant differences exist in the amount of dew on a medium spatial scale (Kidron, 2000), so that dew and fog increase by 0.03 mm per 100 m increase in elevation from the coastal lowlands to the highlands of the Negev (Kidron, 1999).…”

Section: Introductionmentioning

confidence: 99%

The CO<sub>2</sub> exchange of biological soil crusts in a semiarid grass-shrubland at the northern transition zone of the Negev desert, Israel

et al. 2008

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Abstract. Biological soil crusts (BSC) contribute significantly to the soil surface cover in many dryland ecosystems. A mixed type of BSC, which consists of cyanobacteria, mosses and cyanolichens, constitutes more than 60% of ground cover in the semiarid grass-shrub steppe at Sayeret Shaked in the northern Negev Desert, Israel. This study aimed at parameterizing the carbon sink capacity of welldeveloped BSC in undisturbed steppe systems. Mobile enclosures on permanent soil borne collars were used to investigate BSC-related CO 2 fluxes in situ and with natural moisture supply during 10 two-day field campaigns within seven months from fall 2001 to summer 2002. Highest BSC-related CO 2 deposition between -11.31 and -17.56 mmol m −2 per 15 h was found with BSC activated from rain and dew during the peak of the winter rain season. Net CO 2 deposition by BSC was calculated to compensate 120%, -26%, and less than 3% of the concurrent soil CO

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Photosynthesis and Water Relations of Lichen Soil Crusts: Field Measurements in the Coastal Fog Zone of the Namib Desert

Cited by 167 publications

References 21 publications

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

Impact of grazing intensity on seasonal variations in soil organic carbon and soil CO ₂ efflux in two semiarid grasslands in southern Botswana

The CO<sub>2</sub> exchange of biological soil crusts in a semiarid grass-shrubland at the northern transition zone of the Negev desert, Israel

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Photosynthesis and Water Relations of Lichen Soil Crusts: Field Measurements in the Coastal Fog Zone of the Namib Desert

Cited by 167 publications

References 21 publications

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

Impact of grazing intensity on seasonal variations in soil organic carbon and soil CO 2 efflux in two semiarid grasslands in southern Botswana

The CO&lt;sub&gt;2&lt;/sub&gt; exchange of biological soil crusts in a semiarid grass-shrubland at the northern transition zone of the Negev desert, Israel

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Impact of grazing intensity on seasonal variations in soil organic carbon and soil CO ₂ efflux in two semiarid grasslands in southern Botswana

The CO<sub>2</sub> exchange of biological soil crusts in a semiarid grass-shrubland at the northern transition zone of the Negev desert, Israel