Measurements of CO2 exchange over a woodland savanna (Cerrado Sensu stricto) in southeast Brasil

The technique of eddy correlation was used to measure the net ecosystem exchange over a woodland savanna (Cerrado Sensu stricto) site (Gleba Pé de Gigante) in southeast Brazil. The data set included measurements of climatological variables and soil respiration using static soil chambers. Data were collected during the period from 10 October 2000 to 30 March 2002. Measured soil respiration showed average values of 4.8 molCO2 m-2s-1 year round. Its seasonal differences varied from 2 to 8 molCO2 m-2s-1 (Q10 = 4.9) during the dry (April to August) and wet season, respectively, and was concurrent with soil temperature and moisture variability. The net ecosystem CO2 flux (NEE) variability is controlled by solar radiation, temperature and air humidity on diel course. Seasonally, soil moisture plays a strong role by inducing litterfall, reducing canopy photosynthetic activity and soil respiration. The net sign of NEE is negative (sink) in the wet season and early dry season, with rates around -25 kgC ha-1day-1, and values as low as 40 kgC ha-1day-1. NEE was positive (source) during most of the dry season, and changed into negative at the onset of rainy season. At critical times of soil moisture stress during the late dry season, the ecosystem experienced photosynthesis during daytime, although the net sign is positive (emission). Concurrent with dry season, the values appeared progressively positive from 5 to as much as 50 kgC ha-1day-1. The annual NEE sum appeared to be nearly in balance, or more exactly a small sink, equal to 0.1 0.3 tC ha-1yr-1, which we regard possibly as a realistic one, giving the constraining conditions imposed to the turbulent flux calculation, and favourable hypothesis of succession stages, climatic variability and CO2 fertilization

Alguns efeitos do fluometuron sobre o crescimento inicial de Bidens pilosa L. Some effects of fluometuron on early growth of Bidens pilosa L.

Sementes de picão-preto (Bidens pilosa L.) foram germinadas em placas de petri sobre papel de filtro molhado com diferentes concentrações de fluometuron (0, 5, 25, 125 e 625 ppm). O ensaio foi conduzido em condições de laboratório, com variação de temperatura entre 24°C e 28°C e intensidade luminosa máxima de 600 lux e foi encerrado após sete dias (168 horas). O fluometuron diminuiu a germinabilidade e o comprimento da radídula e do hipocótilo, afetou o formato dos cotilédones e, nas concentrações mais elevadas, impediu a rejeição do pericarpo. Os efeitos observados não são atribuíveis a lesões bioquímicas do processo fotossintético.Seeds of Bidens pilosa L. (Compositae) were germinated in Petri dishes on filter paper wetted with aqueous suspensions of fluometuron at different concentrations (0, 5, 25, 125 and 625 ppm). The experiment was conducted during 7 days, under room conditions; the temperature range was 24°C - 28°C and the maximum light intensity was 600 lux. Fluometuron reduced germination percentage, radicle and hypocotyl lenght, affected cotyledon shape and, at the higher concentrations, prevented the pericarp rejection. The observed effects can not be attributed to biochemical lesions of the photosynthetic process

Alguns efeitos do fluometuron sobre o crescimento inicial de Bidens pilosa L.

Sementes de picão-preto (Bidens pilosa L.) foram germinadas em placas de petri sobre papel de filtro molhado com diferentes concentrações de fluometuron (0, 5, 25, 125 e 625 ppm). O ensaio foi conduzido em condições de laboratório, com variação de temperatura entre 24°C e 28°C e intensidade luminosa máxima de 600 lux e foi encerrado após sete dias (168 horas). O fluometuron diminuiu a germinabilidade e o comprimento da radídula e do hipocótilo, afetou o formato dos cotilédones e, nas concentrações mais elevadas, impediu a rejeição do pericarpo. Os efeitos observados não são atribuíveis a lesões bioquímicas do processo fotossintético.Seeds of Bidens pilosa L. (Compositae) were germinated in Petri dishes on filter paper wetted with aqueous suspensions of fluometuron at different concentrations (0, 5, 25, 125 and 625 ppm). The experiment was conducted during 7 days, under room conditions; the temperature range was 24°C - 28°C and the maximum light intensity was 600 lux. Fluometuron reduced germination percentage, radicle and hypocotyl lenght, affected cotyledon shape and, at the higher concentrations, prevented the pericarp rejection. The observed effects can not be attributed to biochemical lesions of the photosynthetic process

Diameter and height distributions of trees sampled outside Brasília Botanical Garden in Brazil used to develop allometric biomass equations.

<p>Diameter and height distributions of trees sampled outside Brasília Botanical Garden in Brazil used to develop allometric biomass equations.</p