THE ROLE OF THE SHRUB CORDIA-MULTISPICATA CHAM AS A SUCCESSION FACILITATOR IN AN ABANDONED PASTURE, PARAGOMINAS, AMAZONIA

We studied the conditions that permit the shrub, Cordia multispicata, to establish in Amazon pastures and the potential role of this shrub a s a 'succession facilitator' near the town of Paragominas, Para State, Brazil. Local disturbances that reduce cover such as grazing and burn ing helped C. multispicata establish in pastures in active use. Germin ation of C. multispicata was significantly improved on sites subjected to simulated grazing and seedling growth was hastened following pastu re burning. We found that below-ground competition, evaluated using ro ot ingrowth cores, was reduced by burning and grazing. Recently abando ned pastures are frequently composed of a mix of forbs and grasses but as succession proceeds a mosaic of more discrete vegetation patches a ppears. At our site, a five-year-old abandoned pasture, grass patches (primarily Panicum maximum) and shrub patches (mainly C. multispicata) were common. We compared physical and biotic characteristics of zones dominated by C. multispicata and P. maximum and found: (1) the rain o f bat and bird dispersed seeds of woody species was much greater in th e zones of C. multispicata (92 seeds/m2/year) than in the patches of g rass (6 seeds/m2/year); (2) the density of woody seedlings was eight t imes greater in the C. multispicata patches (0.65/m2) than in the zone s of P. maximum (0.08 woody individuals/m2); (3) soil nutrient availab ility and litter nutrient concentrations were greater in the shrub zon es than in the grass zones; and (4) photosynthetic photon flux density at the soil surface was generally more favorable for rainforest tree seedling growth in C. multispicata patches (16% of full sunlight) as c ompared to the grass zones (7.7% of full sun). We conclude that the sh rub, C. multispicata, acts as a magnet, attracting volant seed vectors , and as a nurse plant, facilitating the establishment of woody specie s in abandoned Amazon pastures.