THE SPATIOTEMPORAL EFFECTS OF NITROGEN AND LITTER ON THE POPULATION-DYNAMICS OF ARABIDOPSIS-THALIANA

1. The presence of litter and the availability of nitrogen supply were manipulated in experimental field-grown populations of the annual Arabidopsis thaliana (Cruciferae). 2 Arabidopsis typically has two generations a year. Spring-germinating plants (G1) set seed and die. Litter from this generation had an immediate effect on plants of the second generation (G2) germinating during late summer. Litter from G2 broke down over winter, and had a less direct impact on the next spring generation (G3). 3 A two phase model is proposed, whereby litter from G1 plants acted directly to spread reproductive output of G2 plants over many small individuals, with no effect on overall capsule production. 4 Nitrogen depletion by G1 plants did not affect the productivity of the second generation (G2) which germinated in the same summer. 5 After an intervening winter litter from G2 plants (although no longer present) had a stimulatory effect on both the number of plants and the overall capsule production of G3 plants, and this effect was greatly accentuated if nitrogen had also been applied.