Fruit dispersal and seed banks in Atriplex sagittata: the role of heterocarpy

Mandak, B Pysek, P

B. Mandak et P. Pysek, Fruit dispersal and seed banks in Atriplex sagittata: the role of heterocarpy, J ECOLOGY, 89(2), 2001, pp. 159-165

36

INGLESE

Article

Environment/Ecology

JOURNAL OF ECOLOGY

0022-0477 → ACNP

89

2

2001

159 - 165

ISI

0022-0477(200104)89:2<159:FDASBI>2.0.ZU;2-V

1 Atriplex sagittata, an arly succesional, annual species of disturbed habi tats in Central Europe, produces three types of fruits. We studied the diff erences in dispersal between the fruit types in order to investigate their ecological roles. 2 The typical positive relationship between dispersal ability and germinabi lity is not found in this species. Type A (ebracteate) fruits produced deep ly dormant seeds and had the lowest dispersal potential, but of the two fru its with bracts, type B, with dormant seeds, was better dispersed by both w ater and wind than type C, which produces non-dormant seeds. 3 Wind, temperature and precipitation have significant effects on fruit rel ease but their effects differ between fruit types. The release of fruit typ es with bracts was positively correlated with wind whereas all fruit types tended to be negatively correlated with precipitation and temperature range . 4 Type C fruit, which contains non-dormant seed, are absent from the soil i n summer and have a Type II transient seed bank. Type A and B fruits, conta ining dormant seeds, form a persistent seed bank. 5 Heterocarpy, where fruit types show distinct ecological behaviour, enable s colonizing species such as A. sagittata to survive both major disturbance (by ensuring that some seeds persist) and unfavourable conditions (by spre ading germination over a long period). 6 In A. sagittata, seed dynamics can be explained by the germination behavi our of seeds produced by the three types of fruit. All fruit types mature i n autumn, but few of Type A fall from the mother plant until spring, when g ermination is probably inhibited because of insufficient stratification. Ty pe C fruit, however show peak dispersal in winter and the majority of these non-dormant seeds are able to germinate as soon as conditions become more suitable.