Abstract
Microorganisms govern soil carbon cycling with critical effects at local and global scales. The activity of microbial extracellular enzymes is generally the limiting step for soil organic matter mineralization. Nevertheless, the influence of soil characteristics and climate parameters on microbial extracellular enzyme activity (EEA) performance at different water availabilities and temperatures remains to be detailed. Different soils from the Iberian Peninsula presenting distinctive climatic scenarios were sampled for these analyses. Results showed that microbial EEA in the mesophilic temperature range presents optimal rates under wet conditions (high water availability) while activity at the thermophilic temperature range (60°C) could present maximum EEA rates under dry conditions if the soil is frequently exposed to high temperatures. Optimum water availability conditions for maximum soil microbial EEA were influenced mainly by soil texture. Soil properties and climatic parameters are major environmental components ruling soil water availability and temperature which were decisive factors regulating soil microbial EEA. This study contributes decisively to the understanding of environmental factors on the microbial EEA in soils, specifically on the decisive influence of water availability and temperature on EEA. Unlike previous belief, optimum EEA in high temperature exposed soil upper layers can occur at low water availability (i.e., dryness) and high temperatures. This study shows the potential for a significant response by soil microbial EEA under conditions of high temperature and dryness due to a progressive environmental warming which will influence organic carbon decomposition at local and global scenarios.
Highlights
Climate has been reported to directly influence soil biological activity (Conant et al, 2011; Davidson & Janssens, 2006; Xiao, Chen, Jing, & Zhu, 2018)
The aim of this study is to understand the influence of environmental factors, including soil characteristics and climate parameters, on microbial enzyme activity (EEA) in soils studied as a function of water availability and temperature
In spite of current limitations to fully understand the role of microorganisms in soils, this study provides strong evidence of the relevance of soil thermophilic microbial EEA and their potential increasing environmental relevance as a result of current and predicted global warming (Battisti & Naylor, 2009; Davidson & Janssens, 2006; IPCC, 2014) which will lead to increasing frequency and intensity of high temperature and desiccation periods in soils
Summary
Climate has been reported to directly influence soil biological activity (Conant et al, 2011; Davidson & Janssens, 2006; Xiao, Chen, Jing, & Zhu, 2018). Precipitation and temperature are two major factors with important consequences on the microbial activity at upper soil layers (Cheng et al, 2017; Delgado-Baquerizo et al, 2016). It is well known that temperature presents drastic influence on the activity and development of microorganisms (Bradford, Watts, & Davies, 2010; Conant et al, 2011). Different climate conditions can influence microbial functioning by altering soil habitats, microniches, and their environments so that activity is expected to change (Li et al, 2018)
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