Atividade biológica associada à leguminosa nativa sabiá (Mimosa caesalpiniifolia Benth.) e à palmeira ruderal babaçu (Attalea speciosa Mart.) no Maranhão central

Abstract

This study quantifies the consumption of five substrates through the bait-lamina test in four pairs of secondary vegetation dominated by two contrasting species, the babassu palm and the sabiá, and analyzes the different aspects in relation to microbial biomass in four pairs of monospecific areas of these vegetation in the central-north region of Maranhão. The first experiment involved 72 wooden plates, each of which contained three replicas of five different materials at three depths (1 cm, 5 cm and 10 cm). The five substrates used were: (1) a standard mixture of powdered cellulose (70%), wheat starch (27%) and charcoal (3%); (2) green babassu leaflet; (3) yellow babassu leaflet; (4) green sabiá leaflet; (5) yellow sabiá leaflet. After three periods of permanence in the field (1, 3 and 5 weeks) the plates were removed and the 36 holes per plate were analyzed, resulting in a total of 2,592 test holes. The analysis included the state of decomposition (without visible decomposition, partial decomposition, complete decomposition) and the degree of fungal infestation (no visible infestation, partial infestation, complete infestation). Out of the 2592 test holes, 1.2% could not be classify and 3.85% showed fungal infestation and were, excluded from the analyzes. The experiment revealed the presence of fungi Fusarium oxysporum, Penicillium spp., and Aspergillus flavus, as well as oribatid mites and the suborder Acaridida. All orifices were inspected and food consumption of the nutritional mass was quantified using three categories: (1) not consumed, (2) partially consumed and (3) completely consumed. In the first and third week, consumption in the orifices remained in category 1, however, in the fifth week consumption in category 3 was observed, and infestation in category 3 was also observed. The standard substrate was the most consumed, indicated by the median in category 3. Among the substrates composed of green babassu leaflets, green and yellow sabiá leaflets, there were no differences in consumption, the three substrates being in category 2. The yellow babassu leaflet was the least consumed and remained in category 1. In the second experiment, sampling was carried out in four pairs of areas of secondary vegetation and spontaneous capoeira, soil samples were collected at depths of 0-10 cm and removed from 24 sampling points and analyzed approximately 7 weeks after collection. The determination of nitrogen and carbon in microbial biomass was carried out through the processes of digestion, distillation and sample titration. Basal Respiration was determined by incubation and titration. The N contents of the Soil Microbial Biomass differed between the vegetation, being higher in the sabiá, in relation to the carbon values, there was no difference between babassu and sabiá. The CO2 released in breathing also presented higher values in the sabiá. The bait-lamina test did not provide sufficient evidence to prove the Home Field Advantage theory under conditions of intense rainfall and in a short period of time, it is still concluded that the sabiá areas present a more dynamic decomposition of organic residues intense, providing ideal conditions for the formation of substrate for the soil microbiota and release of CO2