Browsing by Author "Machado, R.C.R."

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    Photosynthetic photon flux density, carbon dioxide concentration, and vapor pressure deficit effects on photosynthesis in cacao seedlings
    (2008) Machado, R.C.R.; Elson, M.K.; Bunce, J.A.; Baligar, V.C.
    Independent short-term effects of photosynthetic photon flux density (PPFD) of 50–400 μmol m–2 s–1, external CO2 concentration (Ca) of 85–850 cm3 m–3, and vapor pressure deficit (VPD) of 0.9–2.2 kPa on net photosynthetic rate (PN), stomatal conductance (gs), leaf internal CO2 concentration (Ci), and transpiration rates (E) were investigated in three cacao genotypes. In all these genotypes, increasing PPFD from 50 to 400 μmol m–2 s–1 increased PN by about 50 %, but further increases in PPFD up to 1 500 μmol m–2 s–1 had no effect on PN. Increasing Ca significantly increased PN and Ci while gs and E decreased more strongly than in most trees that have been studied. In all genotypes, increasing VPD reduced PN, but the slight decrease in gs and the slight increase in Ci with increasing VPD were non-significant. Increasing VPD significantly increased E and this may have caused the reduction in PN. The unusually small response of gs to VPD could limit the ability of cacao to grow where VPD is high. There were no significant differences in gas exchange characteristics (gs, Ci, E) among the three cacao genotypes under any measurement conditions.
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    Soil and litter fauna of cacao agroforestry systems in Bahia, Brazil
    (2009) M.K. da Silva Moco; E.F. da Gama-Rodrigues; Machado, R.C.R.; A.C. da Gama-Rodrigues; Baligar, V.C.
    Agroforestry systems deposit great amounts of plant residues on soil and this leads to high levels of soil organic matter content and has increased soil biodiversity and improved its conservation. This study compares the distribution of meso and macrofaunal communities in soil and litter under cacao agroforestry systems and in a natural forest in the southern Bahia state of Brazil. Soil and litter samples were obtained in September 2003, February 2004, and August 2004 in five cacao agroforestry systems. The systems evaluated included: cacao renewed under Erythrina sp. (Erythrina poeppigiana) (CRE); cacao renewed under natural forest (Cabruca, CRF); an old cacao system under Erythrina sp. (OCE); an old cacao system under a natural forest system (Cabruca, OCF) and a cacao germplasm collection area (CGC). As a reference soil and litter under a natural forest (NF) was included. Organisms were collected over a 15-day period with a Berlese– Tullgren apparatus. The density and richness of total fauna varied distinctly according to sites, sampling time and material sampled (soil and litter). 16,409 of fauna were recovered from soil and litter samples and the density of total fauna was 2,094 individuals m-2 in the litter and 641 individuals m-2 in the soil. The richness was 11.8 in the litter and 7.5 in the soil. The cacao agroforestry systems adopted for growing cacao in the southern Bahia region of Brazil have beneficial effects on the soil and litter faunal communities, and such systems of cacao cultivation could be considered as a conservation system for soil fauna. The development of a litter layer resulted in higher abundance and diversity of soil fauna.