DISTINGUISHING FEATURES OF LOBLOLLY AND SHORTLEAF PINE SEEDS - IMPLICATIONS FOR MONITORING SEED PRODUCTION IN MIXED STANDS

Monitoring seed production in mixed loblolly pine - shortleaf pine (Pi nus taeda L,. and Pinus echinata Mill., respectively) stands may requi re identifying individual seeds by species. Although;;loblolly pine se eds are on average heavier and larger than those of shortleaf pine, th ere is considerable overlap ii? these properties for individual seeds. In this study the properties of six: seed lots of each species from A rkansas and Louisiana were examined. Seed weight for loblolly pine ave raged twice that of shortleaf pine, but seed length and width differed by only 13 and 27%, respectively. Seed-coat thickness was the most co nsistent difference observed between the two species: large shortleaf pine seeds had thinner seed coats than small loblolly seeds, but this property was slow and tedious to measure. By contrast. differences in seed-coat thickness were readily detected when conducting a cut test f or seed soundness by subjectively assessing the force required to cut the seed, In a blind test. 12 evaluators estimated within +/-10% of th r known composition of 10-seed subsamples 86% of the time for the cut test compared with only 57% when using seed appearance alone; inexperi enced evaluators Were only slightly lower in accuracy than experienced ones. Use of the cut test as a subjective estimate of the force requi red to cut the seed appears to be reasonably accurate in distinguishin g these two species for most purposes.