ABSTRACT Studies about seed dispersal and germination are important to understand patterns of plant distribution and abundance, and help establish strategies for environmental conservation. We evaluated the role of two different dispersers, the ant Atta laevigata and the maned wolf Chrysocyon brachyurus, in the germination of Copaifera arenicola seeds, a characteristically myrmecochorous plant species. Germination was evaluated for seeds subjected to four treatments: (1) seeds manipulated by the ant, (2) seeds ingested by the maned wolf, (3) seeds that had the elaiosome removed manually, and (4) seeds with elaiosome (unmanipulated seeds). Seeds manipulated by the ant and seeds that had the elaiosome removed manually required less time to germinate and had higher germination percentages (98.6% and 95.8%, respectively) than the other treatments. However, seeds ingested by the maned wolf also had a high germination percentage (87.7%), above that of unmanipulated seeds (34.7%). Probably, elaiosomes of unmanipulated seeds and small remnants of this structure that resist digestion by maned wolf can decrease to some extent seed germination. We argue that dispersal of C. arenicola seeds by the ant and by the maned wolf result in different patterns of seed distribution in the environment and that they have complementary roles in structuring plant populations.

Uma das condições essenciais para a realização da análise textural é a individualização completa das partículas minerais da amostra de solo. Este estudo teve por objetivo avaliar a eficiência de métodos químicos e físicos combinados na dispersão de um Latossolo Vermelho irrigado com água de poço tubular no município de Janaúba - MG (16 º 01 ' 56 '' S e 43 º 25 ' 21 '' W). Foram coletadas amostras de solo na camada de 0-0,10 m em um bananal irrigado e em área adjacente sob mata nativa para determinação da análise textural. Os tratamentos constituíram-se de cinco dispersantes químicos (NaOH 0,1 mol L-1, NaOH 1 mol L-1, calgon 0,1 mol L-1, HCl 0,1 mol L-1 + NaOH 0,1 mol L-1e HCl 1 mol L-1 + NaOH 1 mol L-1) e dois dispersantes físicos (agitação com 50 oscilações horizontais por minuto durante 720 min e agitação com 12.000 rotações por minuto durante 10 min) dispostos em esquema fatorial 2 x 5 x 2 com cinco repetições. Com exceção de HCl 1 mol L-1 + NaOH 1 mol L-1, todos os dispersantes químicos apresentaram teores de argila inferiores no solo sob irrigação, o que pode ser atribuído ao elevado teor de carbonato de Ca no solo em decorrência da água utilizada na irrigação. A utilização de HCl 1 mol L-1 + NaOH 1 mol L-1 é eficiente em dispersar a argila presente em amostras de solo com elevado teor de carbonato de Ca.

One of the essential conditions for soil particle size analysis is the complete dispersion of mineral particles of the soil sample. This study aimed to evaluate the efficiency of chemical and physical methods in combination to disperse samples of an Ustox irrigated with water from a deep well in Janaúba - MG (16 º 01 ' 56 '' S, 43 º 25 ' 21 '' W) was evaluated. Soil samples were collected in the 0-0.10 m layer from an irrigated banana plantation adjacent to a native forest for particle size analysis. Five chemical dispersants were applied in the treatments (NaOH 0.1 mol L-1, NaOH 1 mol L-1, calgon 0.1 mol L-1, HCl 0.1 mol L-1 + NaOH 0.1 mol L-1and HCl 1 mol L-1 + NaOH 1 mol L-1) and two physical dispersants (50 horizontal oscillations per minute for 720 min and 12,000 revolutions per minute for 10 min.) arranged in a factorial design with five replications. All chemical dispersants except HCl 1 mol L-1 + NaOH 1 mol L-1resulted in low clay values in the soil under irrigation, which can be attributed to the high content of calcium carbonate in the soil. The use of HCl 1 mol L-1 + NaOH 1 mol L-1 is effective in dispersing soil samples with high calcium carbonate content.