Analysis of the spatial patterning of trees in the dwarf forest of the Plains and a tall forest in the Wharton Tract of the New Jersey Pine Barrens lead to the following conclusions. (1) In the Plains pitch pine and black-jack oak are exclusively dominant whereas in the Wharton Tract short-leaf pine and chestnut oak also predominate. (2) The trees on the Plains are over three times as dense as in the Wharton Tract which is probably due to the younger age, high rate of survival following forest fires, and rapid regeneration by stump sprouting on the Plains. (3) Fire is responsible for maintaining the random spacing of the relatively sensitive black-jack oak. (4) Black-jack oak in the Plains cannot be recognized as individuals by inspection, while sprouts from pitch pine stoods are distinctive. (5) Uniform spacing among pitch pines in the Plains and among chestnut oaks in the Wharton Tract may be due to concentrated seed predation; there was no evidence of either exploitative competition or allelopathy among trees. (6) Positive association between short-leaf pine clumps and pitch pine clumps could reflect Pinus specific preferences for soil patches. (7) The index of spatial patterning derived by Smith-Gill (1975) is introduced to the ecological literature.© Blackwell Science Ltd. Abstract reproduced by permission.