Adaptive responses of soil microbial communities under experimental acid stress in controlled laboratory studies |
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| Institution: | 1. School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, China;2. Institute of Life Sciences, Jiangsu University, Zhenjiang 212013, China;3. School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK;4. Department of Plant Pathology, Shandong Agricultural University, Tai''an 271018, China;5. Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia;1. Institut für Biowissenschaften, Technische Universität Bergakademie Freiberg, Leipziger Straße 29, 09599, Freiberg, Germany;2. Göttingen Genomics Laboratory, Georg-August-Universität Göttingen, Grisebachstraße 8, 37073, Göttingen, Germany;3. Departamento de Biología, Universidad de Santiago, Avenida Libertador Bernardo O''Higgins nº 3363, Santiago, Chile;1. Manaaki Whenua - Landcare Research, P.O. Box 69040, Lincoln 7640 (New Zealand);2. Embrapa Arroz e Feijão, Highway GO-462, Km 12, P.O. Box 179, Santo Antônio de Goiás 75375-000 (Brazil);3. Wageningen University & Research, Department of Environmental Sciences, P.O. Box 47, Wageningen 6700AA (The Netherlands);1. The Institute of Biofilm Technology, Key Laboratory of Yangtze River Water Environment, Ministry of Education, 1239 Siping Road, Shanghai, China;2. College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China;3. Shanghai Urban Constitution Designed & Research Institute, Shanghai 200011, China |
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| Abstract: | Soil samples from nine different beech forest sites (Ah horizon) with a mean initial soil pH close to neutral (6.4, SD 0.6) were treated with different amounts of H+-ions using acid water of pH 0.5 (H2SO4). The H+-input needed to lower the pH by one or more than three units was in the range between 0.006 and 0.6 mg H+ kg−1, designated as mild, strong or extreme acid stress. The soil samples were incubated for a maximum of 200 days at 20°C and their microbial biomass-C (Cmic), qCO2 and pH was measured at intervals. In addition, the ratio of fungal:bacterial contributions to total respiration was determined at the beginning and end of the experimental period. The extent of microbial biomass-C loss (32–87%) and the increase in the qCO2 (1.8–>7 times) in comparison to acid-untreated samples followed the amount of initial H+-ion input. Differences between treatments based on one-way ANOVA were significant for Cmic depression at day 8 (p<0.01) and day 80 (p<0.05), and for qCO2 at the beginning (p<0.001) and at day 80 only between mild and extreme acid stress (p<0.027). Over time some recovery of the microbial biomass was observed with a concomitant decrease in the qCO2, an indication of adaptation to acidic conditions by the surviving and newly formed biomass. After 80 days of incubation microbial biomass values expressed as percent microbial-C in total soil carbon (Cmic:Corg) resembled those recorded for natural sites at comparable soil pH. There was a strong reduction in bacterial respiration following mild, strong or extreme acid treatment. A recovery here over time was only noted for mild or strong acid treatments. The results confirm that soil pH is a significant controlling parameter for microbial biomass build-up and the fungal:bacterial ratio as found previously with natural site studies. |
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