The enzymatic and physiological response of the microbial community in semiarid soil to carbon compounds from plants

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Cellulose and lignin are major carbon polymers derived from plants and constitute a main source of energy and nutrients for soil microorganisms. In semiarid soil, however, the transformation of organic matter is limited by climatic conditions (mean annual rainfall of less than 300 mm and hot summers) and the small microbial biomass. In the present study, 75 μg C g−1 soil of both cellulose and lignin were added to two semiarid soil types: Calcaric Regosol and Haplic Calcisol, called Abanilla and Santomera, respectively, from their locations. These soils contained different amounts of total organic C (5 g kg−1for the Abanilla soil and 12 g kg−1 for the Santomera soil), which are related to differences in soil quality. Soil enzyme activities, such as cellulase, β-glucosidase, polyphenol oxidase, lipase, catalase, phosphomonoesterase and urease, respiration and community-level physiological profiles (CLPPs) were analysed in both soil types after the addition of cellulose and lignin. Abanilla, the more degraded soil, showed a notable response to the addition of cellulose and lignin from the first day of incubation, with an increase in almost all enzyme activities cited above. For example, cellulose activity reached almost 45 μg glucose g−1 hour−1 in cellulose-amended soil and approximately 30 μg glucose g−1 hour−1 in the control soil. Moreover, more catabolic diversity was observed in the community-level physiological profile (CLPP) after addition of cellulose and lignin than in the control soil. The biochemical response of the microbial community of Santomera soil was slower than that in the Abanilla soil. Furthermore, the larger catabolic diversity (H) of Abanilla than Santomera soil (H = 3.24, H = 2.66, respectively) on the first day of incubation, measured by the community-level physiological profile (CLPP), suggests that the microbial community of semiarid soil without vegetation has the potential to degrade cellulose and lignin.

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