Changes in Cytisus balansae populations after fire

Abstract

Abstract. Demographic changes in Cytisus balansae populations were studied during the first 10 yr after a fire, by comparing populations of different ages in which different cohorts were considered. In the study area this species constitutes a monospecific formation which undergoes periodic burning. We distinguished both new genets (seedlings or plants originating from seedlings, after the last fire) and three types of ramets (resprout clumps): rootstock ramets, basal‐branch ramets and lateral‐root ramets. We found that C. balansae regenerated rapidly after fire. Most seedlings, rootstock ramets and basal‐branch ramets emerged in the first year after fire. Lateral‐root ramets appeared mainly after 2 ‐ 4 yr and continued to emerge in the following years. The numbers of ramets and new genets decreased with time, mainly during the first six years. Density variations between quadrats within each population also decreased. Survivorship varied between seedlings and type of ramet, and according to time of emergence. Survival curves for seedlings which emerged in the first year were concave, for rootstock ramets convex, and for the remainder of the ramets intermediate. The 10‐yr‐old population was dominated by rootstock ramets. Some were entirely dead but most of them had only some dead basal branches. At this age new lateral‐root ramets were still emerging. The future of C. balansae populations is discussed on the basis of results obtained for old (25 ‐ 30 yr) plants, growing in the prolonged absence of fire.