Spatiotemporal variation in seed dispersal and recruitment near and far from Pinus halepensis trees

Spatiotemporal variation in the wind-generated dispersion pattern of Aleppo pine (Pinus halepensis) seeds was examined by placing seed traps up to 110 m away from a small. isolated stand in Israel during six successive disper sal seasons. Subsequent recruitment was surveyed two years later. Of the 54 87 seeds, 97% were trapped 120 m from the nearest adult tree. Seasonal disp ersal curves were consistently right-skewed and leptokurtic. The inverse po wer law and the negative exponential model accounted for a similar fraction of the variation in the number of dispersed seeds at different distances ( 79-86% and 76-88%, respectively). Seed dispersal rates varied significantly among seasons. Eighty saplings (3-5 yr old) became established during the three years of the study, most within 15 m of the nearest canopy, some fart her away, and none directly under the tree canopies. The estimated probabil ity of seed survival to sapling stage increased significantly with increasi ng distance from adults, as predicted by the escape hypothesis. Winds varied significantly between seasons. generating significant intersea sonal variation in seed deposition patterns far from, but not near to, adul t trees. Coefficients of variation of seed dispersal rates were lower near adult trees than farther away. Both Moran's I correlograms and partial Mant el tests revealed interseasonal consistency in seed deposition patterns for the total study area and for the area near adult trees but showed consider able variation farther away. We suggest that the low spatiotemporal variati on near adults and the high variation far away act to intensify the effects of predation (by increasing the efficiency of predators near adults and re ducing it far away) and competition (by increasing the intensity of seedlin g competition near adults and reducing it far away) in structuring the obse rved survivorship curve predicted by the escape hypothesis.