Disponibilidade de fitomassa, banco de sementes do solo e fluxo de co2 em áreas de caatinga no cariri paraibano

• Ano de defesa: 2016
• Autor(a) principal: Oliveira, Karla Priscila de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal da Paraíba; Brasil; Zootecnia; Programa de Pós-Graduação em Zootecnia; UFPB
• Palavras-chave em Português: Espécies nativas; Emergência de plântulas; Disponibilidade de forragem; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA
• Link de acesso: https://repositorio.ufpb.br/jspui/handle/123456789/26146

The Caatinga presents a high variability of species, many of them considered as forage value, however, this resource is often explored only in an extractive way that allied the lack of knowledge about its dynamics has been causing its degradation. The objective of this study was to evaluate the phytomass availability, floristic composition and phytosociological structure of the soil seed bank and the microbial activity through the soil CO2 flow in areas the Caatinga in the Cariri Paraibano. The experiment was carried out at the Experimental Station of the Agricultural Sciences Center of the UFPB, located in São João do Cariri-PB. Phytomass availability and CO2 flux were evaluated in three Caatinga areas with 3.2ha each, being distributed: area I (T1 = 62,5 Kg PC/ha/year), area II (T2 = 31,3 Kg PC/ha/year) and area III (T3 = no animals), in a completely randomized design. In each area, were established three transects, each one being 100 m, 20 m apart, where 10 points were marked on each transect every 10 m, so that 30 plots were sampled in each plot. For the soil seed bank, an area of 100 m2 was used, which was closed to the access of the animals where 30 plots of 1 m2 were installed. For the seed bank in a greenhouse 30 soil samples were collected in the same area and taken to the CCA / UFPB where the identification of the species germinated. Were assessed the phytomass availability, Chemical-bromatological composition, as well as the floristic composition and phytosociological parameters of the herbaceous, sub-shrub, shrub and arboreal. The CO2 flow and soil temperature were evaluated in the diurnal (5 to 17) and nocturnal (17 to 5) shifts, for which 30 sampling points were distributed in each area, totaling 90 points. In each area 30 containers containing 10 mL of 0.5 N KOH were collected to capture CO2 liberated by soil fauna activity. The CO2 quantification was done by titration with 0.1 N HCl, using the phenophthalein and orange methyl indicators. In order to carry out CO2 kinetics, 6 points were selected, and the evaluations were performed every two hours in the daytime period (5 to 17) and soil water, carbon and organic matter contents were determined. Among the families identified, the ones with the highest species richness were Asteraceae, Euphorbiaceae, Fabaceae, Malvaceae and Poaceae. Of the three evaluated areas, the area without animals was the one that xxi presented the greatest number of species (28), showing a greater conservation of the same in relation to the others grazed by goats. The species Aristida adscensionis presented higher frequency in the area with 31,3 Kg PC/ha/ year and in the area without animals. The highest availability of phytomass was observed in the non-animal area. In July, there was a greater participation of the species of the herbaceous stratum due to the greater rainfall occurred in the month. The highest values of crude protein (PB) were verified for the subbranch stratum and for the herbaceous stratum. The herbaceous stratum contributes with greater participation in the phytomass availability of the Caatinga vegetation. The Caatinga has a diverse vegetation in its different strata, being represented by several families. In field conditions the families Fabaceae, Malvaceae and Poaceae presented higher species richness. The species Aristida adscensionis presented the highest importance value (45.7%). The diversity for the Shannon-Weaver (H ') and Pielou (J') indices was 2,63 nats.ind-1 and 0,86, respectively. In a greenhouse the families Fabaceae, Malvaceae, Asteraceae and Poaceae presented greater species richness. The highest value of importance was observed for Aristida adscensionis, with 122.80 ind.m2 . The diversity for the Shannon-Weaver (H ') and Pielou (J') indices was 2.92 nats. ind.-1 and 0.90, respectively. The herbaceous stratum contributes with greater participation in the phytomass availability of the Caatinga vegetation. The use of 62,5 kg PC/ha/year causes a reduction in the availability of phytomass of the Caatinga species. Seed bank species under field conditions and under greenhouse conditions are predominantly represented by the herbaceous stratum. The families Fabaceae, Malvaceae and Poaceae presented more species both in greenhouse and in field conditions. The release of CO2 from the soil presents temporal variation with higher release peaks in the period of higher rainfall. The CO2 rate tends to be higher at the end of the afternoon.