scholarly journals Annual net primary productivity of a cyanobacteria-dominated biological soil crust in the Gulf Savannah, Queensland, Australia

2018 ◽  
Vol 15 (2) ◽  
pp. 491-505 ◽  
Author(s):  
Burkhard Büdel ◽  
Wendy J. Williams ◽  
Hans Reichenberger

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 CO2 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 CO2 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 CO2. 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 CO2 during daylight hours was reduced by 32.6 % due to water supersaturation. In total, the biocrust fixed 229.09 mmol CO2 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 CO2 m−2 was found for the 2 months, resulting in corrected annual rates of 143.1 mmol CO2 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 CO2 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.

2017 ◽  
Author(s):  
Burkhard Büdel ◽  
Wendy J. Williams ◽  
Hans Reichenberger

Abstract. Biological soil crusts 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 on the annual net primary productivity of a cyanobacteria dominated biological soil crust form the Boodjamulla National Park in north western Queensland using a semi-automatic cuvette system. The dominating cyanobacteria are the filamentous species Sypmplocastrum purpurascens together with Scytonema sp. The recording period lasted from July 1st 2010 to June 30th 2011. Metabolic activity was found from November 2010 until mid-April 2011 only, referring to 23.6 % of the total time of the year. With the onset of the raining season in November, the first month of activity had a pronounced respiratory loss of CO2. Also the last month of the raining season had a negative CO2 balance. Of the metabolic active period, 48.6 % were net photosynthesis and 51.4 % dark respiration. Net photosynthetic uptake of CO2 during daylight was reduced at 32.6 % of the time by water suprasaturation during. In total, the biological soil crust fixed 229.09 mmol CO2 m−2 yr−1, referring 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 days in November and December 2010 could not be analysed for net photosynthesis and respiration. Based on climatic and gas exchange data from November 2010, an estimated loss of 88 mmol CO2 m−2 was found for the two month, resulting in annual rates of 143.08 mmol CO2 m−2 yr−1, equivalent to a carbon gain of 1.72 g m−2 yr−1. The bulk net photosynthetic activity occurred above a relative humidity above 42 %, indicating a suitable climatic combination of temperature and water availability, and a light intensity well above 200 µmol photons m−2 s−1 photosynthetic active radiation. The Boodjamulla biocrust showed a highly seasonally varying CO2 gas exchange pattern divided into metabolically inactive winter month and active summer month. The metabolic active period starts with a period (up to 3 month) of carbon loss, probably due to regrowth before a four month period of carbon gain. This must be taken into consideration for future analyses and modelling of carbon balances in comparable biocrust ecosystems.


2020 ◽  
Author(s):  
shuo li ◽  
Alexander V. Babanin ◽  
Fangli Qiao ◽  
Dejun Dai ◽  
Shumin Jiang ◽  
...  

2018 ◽  
Vol 2 (3) ◽  
Author(s):  
Toshio Ohhashi ◽  
Yoshiko Kawai

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