Do light and litter influence the recruitment of Cistus spp. stands?

After a major disturbance (such as fire or soil upsetting), large numbers o f Cistus spp. seedlings may appear and ensure population recruitment, but i n the absence of such disturbances seedlings are rare or nonexistent in mat ure Cistus stands. What are the causes? Two factors, little studied until n ow, have been examined: the influence of litter and of light reaching the s oil surface. In two types of stands, one dominated by C. monspeliensis and the other by C. albidus, an experiment was undertaken by removing the veget ation cover and by the presence or absence of litter to examine the establi shment of seedlings. The seed bank in the soil was also studied to determin e its size. Seeds were also subjected to a temperature of 52 degrees C to s imulate exposure to full sunlight in summer and determine whether this had any affect on their germination rate. Light and litter had no effect on the germination, irrespective of the qual ity or intensity of light reaching the soil or the presence or absence of l itter; there were always few seedlings and there was no significant differe nce in numbers between treatments. There was a large seed bank in the soil and these seeds were capable of germinating following experimental conditio ns: the heat stress applied proved to be too slight to break seed dormancy, although they were viable because they germinated after scarification. In existing Cistus spp. stands, Cistus spp. seeds germinate with difficulty, a nd lack of recruitment could lead to disappearance of local communities unl ess they are subjected to disturbances.