Abstract:Introduction: Lichen dominated biological soil crusts (BSCs) occur over large areas in the Sonoran Desert of the southwestern USA and northwest Mexico. In Baja California BSCs show a distinct patchiness and several types can be distinguished. Two chlorolichen-and two cyanolichen-dominated BSCs were selected. We hypothesize that patchiness and the resulting domination of certain functional lichen groups will result in patchiness of photosynthetic CO 2 -uptake related to environmental factors as well. Methods: F… Show more
“…A number of reports of typical soil crust lichen response curves of CO 2 -gas-exchange to water content, light, and temperature as well as diurnal courses have been published and our results are well in accordance with those results (e.g. Hahn et al 1989; Hahn 1992; Lange et al 1996, 1997, 1998; Lange 2000; Büdel et al 2013). Maximal rates of area based net photosynthesis of BSCs from different regions of the world range from 0.11 to 11.5 μmol CO 2 /m 2 s (Lange 2003) and with about 2.5 μmol CO2/m 2 s the crusts investigated here are in the lower range of those crusts listed by Lange (2003) that originated from all over the world.Fig.…”
Here we report details of the European research initiative “Soil Crust International” (SCIN) focusing on the biodiversity of biological soil crusts (BSC, composed of bacteria, algae, lichens, and bryophytes) and on functional aspects in their specific environment. Known as the so-called “colored soil lichen community” (Bunte Erdflechtengesellschaft), these BSCs occur all over Europe, extending into subtropical and arid regions. Our goal is to study the uniqueness of these BSCs on the regional scale and investigate how this community can cope with large macroclimatic differences. One of the major aims of this project is to develop biodiversity conservation and sustainable management strategies for European BSCs. To achieve this, we established a latitudinal transect from the Great Alvar of Öland, Sweden in the north over Gössenheim, Central Germany and Hochtor in the Hohe Tauern National Park, Austria down to the badlands of Tabernas, Spain in the south. The transect stretches over 20° latitude and 2,300 m in altitude, including natural (Hochtor, Tabernas) and semi-natural sites that require maintenance such as by grazing activities (Öland, Gössenheim). At all four sites BSC coverage exceeded 30 % of the referring landscape, with the alpine site (Hochtor) reaching the highest cyanobacterial cover and the two semi-natural sites (Öland, Gössenheim) the highest bryophyte cover. Although BSCs of the four European sites share a common set of bacteria, algae (including cyanobacteria) lichens and bryophytes, first results indicate not only climate specific additions of species, but also genetic/phenotypic uniqueness of species between the four sites. While macroclimatic conditions are rather different, microclimatic conditions and partly soil properties seem fairly homogeneous between the four sites, with the exception of water availability. Continuous activity monitoring of photosystem II revealed the BSCs of the Spanish site as the least active in terms of photosynthetic active periods.Electronic supplementary materialThe online version of this article (doi:10.1007/s10531-014-0645-2) contains supplementary material, which is available to authorized users.
“…A number of reports of typical soil crust lichen response curves of CO 2 -gas-exchange to water content, light, and temperature as well as diurnal courses have been published and our results are well in accordance with those results (e.g. Hahn et al 1989; Hahn 1992; Lange et al 1996, 1997, 1998; Lange 2000; Büdel et al 2013). Maximal rates of area based net photosynthesis of BSCs from different regions of the world range from 0.11 to 11.5 μmol CO 2 /m 2 s (Lange 2003) and with about 2.5 μmol CO2/m 2 s the crusts investigated here are in the lower range of those crusts listed by Lange (2003) that originated from all over the world.Fig.…”
Here we report details of the European research initiative “Soil Crust International” (SCIN) focusing on the biodiversity of biological soil crusts (BSC, composed of bacteria, algae, lichens, and bryophytes) and on functional aspects in their specific environment. Known as the so-called “colored soil lichen community” (Bunte Erdflechtengesellschaft), these BSCs occur all over Europe, extending into subtropical and arid regions. Our goal is to study the uniqueness of these BSCs on the regional scale and investigate how this community can cope with large macroclimatic differences. One of the major aims of this project is to develop biodiversity conservation and sustainable management strategies for European BSCs. To achieve this, we established a latitudinal transect from the Great Alvar of Öland, Sweden in the north over Gössenheim, Central Germany and Hochtor in the Hohe Tauern National Park, Austria down to the badlands of Tabernas, Spain in the south. The transect stretches over 20° latitude and 2,300 m in altitude, including natural (Hochtor, Tabernas) and semi-natural sites that require maintenance such as by grazing activities (Öland, Gössenheim). At all four sites BSC coverage exceeded 30 % of the referring landscape, with the alpine site (Hochtor) reaching the highest cyanobacterial cover and the two semi-natural sites (Öland, Gössenheim) the highest bryophyte cover. Although BSCs of the four European sites share a common set of bacteria, algae (including cyanobacteria) lichens and bryophytes, first results indicate not only climate specific additions of species, but also genetic/phenotypic uniqueness of species between the four sites. While macroclimatic conditions are rather different, microclimatic conditions and partly soil properties seem fairly homogeneous between the four sites, with the exception of water availability. Continuous activity monitoring of photosystem II revealed the BSCs of the Spanish site as the least active in terms of photosynthetic active periods.Electronic supplementary materialThe online version of this article (doi:10.1007/s10531-014-0645-2) contains supplementary material, which is available to authorized users.
“…At Site Homburg, the dominant lichen was Psora decipiens, with 3-4 mm wide squamules and a usually white, slightly upturned margin. This lichen has a cosmopolitan distribution and is known to be a key species in BSC from many different localities (Brodo et al, 2001;Bü del et al, 2009;Bü del et al, 2013). The occurrence of this species, together with the presence of all additional functional groups of cryptogams in BSC, underlines the moderate character of this site.…”
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.
“…Their investigation sites included one region with noteworthy biocrust cover not accompanied by dense vascular plant vegetation, the La Paz region of Baja California, with an annual C uptake (NEP) of roughly 90 g m −2 . Approximating annual C gain based on the maximal CO 2 uptake rates of four biocrust types composed of cyanobacteria, cyanolichens and chlorolichens from Baja California (Büdel et al, 2013), we approach an annual C gain for those biocrusts of 11 ± 4 g m −2 . The calculation was based on the following estimations: 90 active days per year with 34 of them having a sub-optimal CO 2 uptake rate of only 25 % of maximum due to supersaturation.…”
Abstract. Biological soil crusts (biocrusts) are a common element of the Queensland (Australia) dry savannah ecosystem and are composed of cyanobacteria, algae, lichens, bryophytes, fungi and heterotrophic bacteria. Here we report how the CO 2 gas exchange of the cyanobacteria-dominated biocrust type from Boodjamulla National Park in the north Queensland Gulf Savannah responds to the pronounced climatic seasonality and on their quality as a carbon sink using a semi-automatic cuvette system. The dominant cyanobacteria are the filamentous species Symplocastrum purpurascens together with Scytonema sp. Metabolic activity was recorded between 1 July 2010 and 30 June 2011, during which CO 2 exchange was only evident from November 2010 until mid-April 2011, representative of 23.6 % of the 1-year recording period. In November at the onset of the wet season, the first month (November) and the last month (April) of activity had pronounced respiratory loss of CO 2 . The metabolic active period accounted for 25 % of the wet season and of that period 48.6 % was net photosynthesis (NP) and 51.4 % dark respiration (DR). During the time of NP, net photosynthetic uptake of CO 2 during daylight hours was reduced by 32.6 % due to water supersaturation. In total, the biocrust fixed 229.09 mmol CO 2 m −2 yr −1 , corresponding to an annual carbon gain of 2.75 g m −2 yr −1 . Due to malfunction of the automatic cuvette system, data from September and October 2010 together with some days in November and December 2010 could not be analysed for NP and DR. Based on climatic and gas exchange data from November 2010, an estimated loss of 88 mmol CO 2 m −2 was found for the 2 months, resulting in corrected annual rates of 143.1 mmol CO 2 m −2 yr −1 , equivalent to a carbon gain of 1.7 g m −2 yr −1 . The bulk of the net photosynthetic activity occurred above a relative humidity of 42 %, indicating a suitable climatic combination of temperature, water availability and light intensity well above 200 µmol photons m −2 s −1 photosynthetic active radiation. The Boodjamulla biocrust exhibited high seasonal variability in CO 2 gas exchange pattern, clearly divided into metabolically inactive winter months and active summer months. The metabolic active period commences with a period (of up to 3 months) of carbon loss, likely due to reestablishment of the crust structure and restoration of NP prior to about a 4-month period of net carbon gain. In the Gulf Savannah biocrust system, seasonality over the year investigated showed that only a minority of the year is actually suitable for biocrust growth and thus has a small window for potential contribution to soil organic matter.
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