Jacques Carvalho Ribeiro Filho

Carbon stocks in a tropical dry forest in Brazil

The dry forests are the type most widely distributed vegetation in the tropics, and studies aimed at quantifying the carbon stock in these forests are important for it to be quantified their participation as mitigating the effects of climate change. With that in mind, the aim of this research was to quantify the carbon stocks in the woody, herbaceous, litter and root components of a patch of dry tropical forest, with 30 years of regeneration in Iguatu-CE, Brazil. Initially the vegetation was inventoried by means of a floristic and phytosociological survey of the woody component in a 1 ha area which had been under conservation. The biomass was then estimated employing allometric equations, and the stored carbon was quantified. Stocks of carbon in the litter and the herbaceous plants were determined by monitoring their biomass over 24 months, with subsequent conversion into carbon. Carbon stocks in the roots were estimated as the product of their biomass and carbon concentrations, for this were collected 20 samples at a depth of up to 30 cm deep in the dry and rainy season. It was found that the carbon content varies with the chamber and evaluated by adding carbon stored in woody compartments (19,27 t ha-1) litter (2.62 t ha-1) plants herbaceous (0.57 t ha-1) and roots (4.73 t ha-1), the total carbon stored in the dry tropical forest with 30 years of regeneration is around 27.19 t C ha-1. The dry tropical forest acts effectively in reducing CO2 atmospheric.

CARACTERISTICAS DAS CHUVAS E RESPOSTAS SEDIMENTOLOGICAS EM DIFERENTES USOS DO SOLO NO SEMIÁRIDO

The objective of this work was to evaluated the precipitation characteristics (depth, I30 and erosivity) and their effects on sediment production in three watersheds under different managements of land use 35-year regenerating Caatinga (RC), thinned Caatinga (TC), which underwent thinning of trees with diameter smaller than 10 cm; and deforested Caatinga (followed by burning and pasture) (DC). The experimente was conducted in the central, tropical semiarid region of the State of Ceará, Brazil. The precipitation events, surface runoff and sediment production were monitored from 2010 to 2015. The precipitation characteristics were subjected to Pearsons correlation at 1 and 5% of significance and the events that produced sediments in each watershed were hierarchically grouped by hierarchical cluster analysis technique. Two hundred precipitation events were recorded, with 23 (RC), 18 (TC) and 43 (DC) events producing sediments. The use of thinning (TC) decreased the sediment production by 53.5%, while the deforestation, burn and pasture cultivation (DC) increased soil losses by 14%, compared with the RC. The sediment production was greatly correlated with the I30 in the three watersheds, denoting the erosion process great dependence on the precipitation intensity.

PRECIPITAÇÃO EFETIVA E PERDAS DE SOLO EM DIFERENTES SISTEMAS DE COBERTURA VEGETAL NO BIOMA CAATINGA

The objective of this work was to evaluate the influence of anthropic activities on the effective precipitation (eP) and soil loss in watersheds under different land uses in a tropical dry forest region. The experimental area was located in the central part of the State of Ceará, Brazil. The land uses evaluated were: fallow Caatinga (FC), thinned Caatinga (TC) and deforested Caatinga followed by a burning procedure and pasture cultivation (DBP). The areas were monitored in the rainy season (January to May, 2010), when 57 natural rainfalls occurred, totaling 941 mm of precipitation. The eP and sediment productions were quantified by the sum of all occurrences during the study period, and the soil loss was represented by suspended and dragged sediments. The eP was 15.13 mm and sediment produced was 167.81 kg ha in FC conditions. The eP values was smaller (11.28 mm) in the watershed with TC, which had soil loss sum of 42.04 kg ha . The largest annual eP was found in the DBP area, with 112.88 mm yr of accumulated water depth, which also showed the greater annual soil loss (3114.97 kg ha). The greatest interference of plant cover in the two variables evaluated occurred in the first precipitation events, when the plants were not yet fully developed.

ESTRATO HERBÁCEO E FATORES HIDROSEDIMENTOLÓGICOS EM MICROBACIAS EXPERIMENTAIS COM DIFERENTES MANEJOS NO SEMIÁRIDO CEARENSE

Objetivou-se com o presente trabalho avaliar o efeito do bosque herbaceo sobre as respostas hidrosedimentologicas de microbacias localizadas no semiarido cearense. Foram avaliadas duas microbacias, uma apresentando cobertura vegetal caatinga nativa e a outra foi submetida ao raleamento das plantas cujo diâmetro do caule era inferior a 10 cm. As variaveis hidrosedimentologicas estudadas foram: precipitacao pluviometrica, umidade do solo, escoamento superficial e perda de solo. As variaveis foram monitoradas em escala temporal de 24 horas por um periodo de dois anos (Jan/2010 a Dez/2011). As coletas do estrato herbaceo foram coletadas mensalmente para o mesmo periodo. A producao de biomassa no manejo raleado chegou a ser superior em 90%, quando comparada com o manejo de caatinga nativa para o ano de 2010. Esse maior desenvolvimento da vegetacao herbacea na microbacia raleada promoveu um aumento na taxa de infiltracao da agua no solo, com consequente reducao da lâmina escoada e das perdas de solo, tal fato promoveu uma maior umidade do solo na microbacia raleada em mais de 89% dos eventos, quando comparada com a microbacia nativa. Do ponto de vista de conservacao de agua e solo, o manejo do raleamento se mostra bastante adequado para o bioma caatinga.