Journal
BIODIVERSITY AND CONSERVATION
Volume 23, Issue 7, Pages 1787-1807Publisher
SPRINGER
DOI: 10.1007/s10531-014-0681-y
Keywords
Warming; Rain exclusion; Lichens; Gas exchange; Chlorophyll fluorescence; Semi-arid land
Funding
- European Research Council under European Community [242658]
- Spanish Ministry of Economy and Competitiveness (PREVEA project) [CGL2007-63258/BOS, PRI-PIMBDV-2011-0874]
- Junta de Andalucia (COSTRAS project) [RNM-3614]
- Spanish National Research Council (CSIC) [2007-029, 2009-031]
- Spanish Ministry of Education, Culture and Sports (FPU) [AP2010-0759]
- British Ecological Society [231/1975]
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The importance of biological soil crusts (biocrusts) for the biogeochemistry of drylands is widely recognized. However, there are significant gaps in our knowledge about how climate change will affect these organisms and the processes depending on them. We conducted a manipulative full factorial experiment in two representative dryland ecosystems from central (Aranjuez) and southeastern (Sorbas) Spain to evaluate how precipitation, temperature and biocrust cover affected the assimilation and net C balance of biocrusts. Chlorophyll fluorescence, net photosynthesis and dark respiration were measured in situ bimonthly during a year. We also conducted daily cycle measurements of net photosynthesis in winter and at the end of spring. In Sorbas, warming reduced the fixation of atmospheric C in biocrust-dominated microsites throughout the year. In Aranjuez, there was an interaction between the three factors evaluated; during winter, net photosynthesis was significantly greater in high biocrust cover plots under natural conditions and in the rainfall exclusion treatment. During the daily surveys, rainfall exclusion and warming reduced C fixation in Sorbas and in Aranjuez respectively. The effects of the treatments evaluated varied with the rainfall and non-rainfall water inputs (NRWIs) registered before the measurements. Our results suggest that changes in NRWI regimes as consequence of warming could have a greater impact on the C balance of biocrusts than changes in rainfall amounts. They also indicate that climate change may reduce the photosynthetic ability of lichens, with a consequent reduction of their dominance in biocrust communities at the mid to long term. This could reduce the ability of dryland ecosystems to fix atmospheric C.
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