The microbiome plays a fundamental role in forest ecosystems. In addition, it is responsible for ensuring nutrient cycling and maintaining soil and trees health. However, microbiomes studies in Eucalyptus forests has not received much attention of the researchers. Moreover, the idea of removing forest residues for energy generation is being gradually accepted in Brazil, but it is straightly opposite to the reasoning behind the minimum-till principle, a well-established forest practice in several regions of the Brazil. There are no reports in the literature regarding the changes caused by the removal of forest residues on the taxonomic and functional diversity of microbiome in tropical soils. The reduction on C soil levels, as well as in the tree productivity are the principal effects reported in recent studies that adopted this practice. This reality allows for the following questioning: Are we trying to deconstruct the knowledge acquired over decades, in which the maintenance of forest residues has brought uncountable benefits to soil and plant health? To respond this question, we are going to follow-up a long-term experiment, installed with different levels of forest residue removals for the Eucalyptus grandis plantation, evaluating the metagenome in order to identify important drivers associated with soil nutrient cycling. Our main hypothesis is that forest residues removal reduces the taxonomic and functional diversity of the microbiome and promote consistently decreases in the soil C and N cycling. This experiment was installed in 2004 and reinstalled in 2012 (first and second rotation, respectively), at the Itatinga Experimental Station of Forest Sciences (ESALQ-USP) in a Yellow Latosol, typically dystrophic, with medium sandy texture. In this experiment, soil samples from the organic (H-org., ~0-5 cm) and mineral (H-min., ~5-20 cm) horizon are going to be sampled in two seasons of the year (dry and rainy). Soil chemical and physical characterization will be performed, as well as metabolic profile (C degradation) and microbial-enzymatic activity of the soil microbiome will be analyzed. The taxonomic and functional profile of the microbiome shall be evaluated through large-scale sequencing (16S rRNA and Shotgun), where the effect of the consecutive removal of forest residues will be evaluated to confirm or not our initial hypotheses. We hope to obtain a solid basis to transform the microbiome study into a toll for decision taking on the silvicultural practice, whether or not to remove the forest residues, in the light of a robust evaluation of the C and N cycling in this environment.
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