Abstract
Soil greenhouse gas (GHG) emissions are a significant environmental problem resulting from microbially-mediated nitrogen (N) and carbon (C) cycling. This study aimed to investigate the impact of Eucalyptus plantations on the structure and function of a soil microbial community, and how resulting alterations may be linked to GHG fluxes. We sampled and monitored two adjacent Eucalyptus plantations—a recently logged site that harbored new seedlings and an adult plantation—and compared them to a site hosting native vegetation. We used 16S rRNA gene sequencing and qPCR amplifications of key nitrogen and methane cycle genes to characterize microbial structure and functional gene abundance and compared our data with soil parameters and GHG fluxes. Both microbial community attributes were significantly affected by land use and logging of Eucalyptus plantations. The genes nosZ and archaeal amoA were significantly more abundant in native forest than in either young or old Eucalyptus plantations. Statistical analyses suggest that land use type has a greater impact on microbial community structure and functional gene abundance than Eucalyptus rotation. There was no correlation between GHG fluxes and shifts in microbial community, suggesting that microbial community structure and functional gene abundance are not the main drivers of GHG fluxes in this system.
Highlights
Emissions of greenhouse gases (GHG) through human activities represent a pressing issue today, contributing to global climate change and ecosystem destabilization[1]
We studied GHG fluxes and the microbial community associated with Eucalyptus plantations at two growth stages, and with a native Brazilian tropical forest (Atlantic Forest)
We did identify some differences in soil characteristics among treatments, especially lower soil pH in area Young Eucalyptus (YE) than native forest treatment (NF), and higher NO3− content in areas YE than Old Eucalyptus (OE) compared to NF
Summary
Emissions of greenhouse gases (GHG) through human activities represent a pressing issue today, contributing to global climate change and ecosystem destabilization[1]. Planted forests cover 7.8 million ha in Brazil[6], and they are thought to play many positive roles in the context of climate change and deforestation through restoration of degraded land, soil conservation, CO2 sequestration, and protection of biodiversity. Their appropriate use in many industrial applications reduce pressures on native forests[7]. GHG fluxes in Eucalyptus plantations have not yet been well described in the tropics, so a greater understanding of the impacts of Eucalyptus plantation management on these fluxes is still needed Soil behaves as both source and sink for GHGs12, as it represents the living space for the microbial communities responsible for nutrient cycling[13]. Microbial activities in the N and C cycles are central to GHG fluxes in soil
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