Florística e fitossociologia, deposição de serapilheira e atividade microbiana em áreas de caatinga sob pastejo caprino

• Autor(a) principal: Luna, Rômulo Gil de
• Data de Publicação: 2015
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/14535
• topic: Semiárido; Pastejo; Desertificação; Indicadores ecológicos; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA

The Caatinga is the main biome of the Brazilian semi-arid region and the number of degraded areas in its ecosystems has been growing every day. The objective of this work is to know the floristic and phytosociological composition of litter deposition, and microbiological attributes of soil in areas under different densities of goats, aiming to use these parameters as indicators of desertification. The study was carried out on the Experimental Farm Basin School (7° 24‟ S; 36° 32‟ W), in São João do Cariri-PB. The density of goats was of 3 animals/ha and 1.5 animals/ha in the treatments T1 and T2, respectively; and no animals in T3 and T4. Thirty plots of 10 m x 10 m were plotted in each experimental area, distributed over three lines of semi-parallel tracks. Floristic and phytosociological analyses included only individuals of arboreal and shrubby ports with CNS ≥ 9.5 cm and At ≥ 1.0 m. Collectors were distributed in the areas, with monthly inspection to collect the material that felt from plants. The referred material was kiln-dried and weighed. Soil samples were collected to analyze microbiological and chemical attributes and fertility. To determine the decomposition activity (AD), nylon bags were used containing pure cellulose in its interior, and buried at 20.0 cm depth. These were collected and renewed every 45 days, which rate of decomposition was determined. The microbial biomass (BM) was estimated using the method of fumigation-incubation and respiratory activity (AR) from non-fumigated soil samples. From these parameters, the qCO2 and Cmic : Corg of soils were calculated. Related to floristic and phytosociology, 413 individuals were registered, six families and nine species; 332 individuals, seven families and nine species; 315 individuals, six families and nine species and 215 individuals, four families and seven species in T1, T2, T3 and T4, respectively. The families Fabaceae, Euphorbiaceae, Apocynaceae and Cactacea were those that exhibited the greatest numbers of individuals, and the species P. pyramidalis, A. pyrifolium, P. gounellei, and C. blanchetianus exhibited the highest values for all phytosociological parameters analyzed. Considering the data of litter, it was not found sufficient evidence to conclude about the effects of treatments, and evaluation times of seasonality on the deposition of this material. In almost all treatments, the deposition was very low if compared to other areas of caatinga preserved, being, in some treatments, less than the annual consumption of goats. The soils of the four treatments presented high sum of bases (high contents of Ca, Mg, K and Na) and low levels of soil organic matter. The low values of litter here obtained when compared to those observed in areas of better preserved caatingas seem to serve as good indicators of degradation. The AD (decomposition activity) was not useful as biological indicator of degraded areas, because in some evaluation times it was higher in T1 and T2 and in others, in the testimony area. As general analysis, one can infer that the treatment T3 presented the best pH, the highest levels of P, K, Ca and Mg and values of CTC, V% and SB than the soil of the areas I, II and IV, as well as the highest floristic diversity. BM parameters, RB, qCO2 and Cmic : Corg relation (in 2012) and BM and Cmic : Corg (2013) were more susceptible to degradation by grazing, and can be used as ecological indicators of degraded areas.