Comparative Resistance and Resilience of Soil Microbial Communities and Enzyme Activities in Adjacent Native Forest and Agricultural Soils |
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Authors: | Guilherme Chaer Marcelo Fernandes David Myrold Peter Bottomley |
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Institution: | (1) Embrapa Agrobiologia, Seropédica, RJ, Brazil;(2) Embrapa Tabuleiros Costeiros, Aracaju, SE, Brazil;(3) Crop and Soil Science, Oregon State University, Corvallis, OR, USA;(4) Microbiology, Oregon State University, Corvallis, OR, USA |
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Abstract: | Degradation of soil properties following deforestation and long-term soil cultivation may lead to decreases in soil microbial
diversity and functional stability. In this study, we investigated the differences in the stability (resistance and resilience)
of microbial community composition and enzyme activities in adjacent soils under either native tropical forest (FST) or in
agricultural cropping use for 14 years (AGR). Mineral soil samples (0 to 5 cm) from both areas were incubated at 40°C, 50°C,
60°C, or 70°C for 15 min in order to successively reduce the microbial biomass. Three and 30 days after the heat shocks, fluorescein
diacetate (FDA) hydrolysis, cellulase and laccase activities, and phospholipid-derived fatty acids-based microbial community
composition were measured. Microbial biomass was reduced up to 25% in both soils 3 days after the heat shocks. The higher
initial values of microbial biomass, enzyme activity, total and particulate soil organic carbon, and aggregate stability in
the FST soil coincided with higher enzymatic stability after heat shocks. FDA hydrolysis activity was less affected (more
resistance) and cellulase and laccase activities recovered more rapidly (more resilience) in the FST soil relative to the
AGR counterpart. In the AGR soil, laccase activity did not show resilience to any heat shock level up to 30 days after the
disturbance. Within each soil type, the microbial community composition did not differ between heat shock and control samples
at day 3. However, at day 30, FST soil samples treated at 60°C and 70°C contained a microbial community significantly different
from the control and with lower biomass regardless of high enzyme resilience. Results of this study show that deforestation
followed by long-term cultivation changed microbial community composition and had differential effects on microbial functional
stability. Both soils displayed similar resilience to FDA hydrolysis, a composite measure of a broad range of hydrolases,
supporting the concept of high functional redundancy in soil microbial communities. In contrast, the resilience of the substrate-specific
activities of laccase and cellulase were lower in AGR soils, indicating a less diverse community of microorganisms capable
of producing these enzymes and confirming that specific microbial functions are more sensitive measurements for evaluating
change in the ecological stability of soils. |
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