Are Phosphatase Activities Related to Microbial Abundance and Activity in Soil?.

Activities of enzymes in soil could be contributed from intracellular and extracellular enzymes. Microorganisms are considered major contributors of soil enzymes. However, activities of soil enzymes are often not strongly correlated with microbial abundance and activities because a significant fraction of the enzymatic activities could be originated from non-viable microbial cells, soil fauna, plants, or cell-free enzymes from all sources.  The main goal of this study was to reveal whether and to what degree phosphatase activities and indices of microbial abundance and activity in soil are related with the intent to understand conditions that foster this relationship and exploit their functional capacity in an ecosystem context.  Evaluations were conducted through data mining based on relevant studies published between 2004 to 2013 in Soil Biology and Biochemistry and Applied Soil Ecology. Data were extracted from a total of 50 studies employing 472 diverse soil types with a range of soil properties. Key parameters evaluated included activities of acid and alkaline phosphomonoesterases, the content of microbial biomass carbon and nitrogen, and basic soil properties. Activities of acid or alkaline monophosmonoesterase were highly correlated (P < 0.001) with the content of organic carbon and microbial biomass carbon as well as soil pH, with r values ranging from 0.17*** to 0.66*** (n=112–186).  Activities of alkaline phosphomonoesterase were more closely (r = 0.47 vs 0.17) associated with microbial biomass carbon than acid phosphomonoesterase, suggesting differential origin and status of these two classes of enzymes in soil. However, data consistently suggested that soil enzyme activities are more closely associated with the content of organic carbon than microbial biomass carbon, signifying the predominant contribution of cell-free enzymes to the detected activities in soil.