Supressão de Corymbia citriodora (Hook.) K. D. Hill e L. A. S. Johnson: uma discussão sobre as alterações no solo

Abstract

Recent studies have shown the importance of the biological community of the soil in determining its quality and in the process of transformation and stabilization of soil organic matter (SOM). This study is based on the hypothesis that the adequate suppression of old plantations (> 25 years old) of Corymbia citriodora (Hook.) K. D. Hill and L. A. S. Johnson, in tropical regions with high rainfall rates and clayey soil, increases the stock and quality of waste under the soil and intensifies biological activity, considered precursors to the increase in SOM and soil quality, generating a better balance between stable and labile SOM fractions. In this study, indicators of soil quality and SOM dynamics were evaluated in areas of C. citriodora plantations submitted to three managements that aim at prioritizing the restoration of native vegetation in the Biological Reserve (REBIO) União - RJ, namely: suppression of C. citriodora planting subjected to girdling (GR); suppression of C. citriodora planting submitted to the practice of shallow cutting and subsequent planting of native seedlings (PL) and planting of abandoned C. citriodora without management practice (EU). These managements were compared with native forest area (FF). Soil, litter and fauna were sampled to determine the General Indicator of Soil Quality (GISQ) through quantification of chemical and biological attributes and correlation with litter attributes. The total contents of C, nitrogen (N) and phosphorus (P) in air-dried fine earth (ADFE) were also determined; in light organic matter (LFOM) and in the granulometric fractions of SOM, in addition to the C extracted by potassium permaganate. In the soil under FF and GR, percentages of tOC around 50% higher than the PL area were observed. The microbiological properties were the most efficient in differentiating the study areas. In the EU area, the highest values of C: N (33.93) and N: P (38.18) were observed, in addition to the lowest levels of C, N and P in the particulate fraction of SOM. In GR, POXC values 187.37% higher than EU were quantified, favoring the production of less recalcitrant and more labile material when compared to EU. The short time (4 years) of implementation of the system in PL directly affected the low production of LFOM, with percentages of 64, 58 and 57% lower when compared to the GR, EU and FF areas respectively. GISQ showed high quality for the soil under FF, medium for GR and PL and low for EU. The results allow inferring that the practice of girdling (GR) is a potential strategy, aiming at the suppression of C. citriodora, favoring soil quality, boosting soil/plant interactions and mainly favoring the availability of labile N and P in the soil.