Distinguishing Saplings of Pines of Piedmont Upland Grassland Systems

Abstract

The development and assessment of Piedmont upland grassland restoration efforts is hampered in part by continued challenges in identifying immature individuals of three associated pines, Pinus echinata, P. taeda, and P. virginiana, the penultimate of which is thought alien to the system. To help fill this gap, we studied three quantitative and 25 qualitative characters in 174, 2- to 5-year-old saplings in managed stands in Durham County (North Carolina) and 169 herbarium specimens of mature individuals from 94 Piedmont counties from Georgia to Virginia. Although mean short-shoot needle and fascicle sheath lengths differed significantly between lifestage classes of the three species (F8,335=185, p<0.0001 and F8,335=173.5, p<0.0001, respectively), there was substantial range overlap, likely contributing to diagnostic confusion in the field when existing keys are applied. For example, needle length ranges of all lifestage classes of all species overlapped with those of mature P. echinata and 2-year-old P. virginiana. In addition, at the apex of the previous season's growth, 2-year-old saplings of P. echinata and P. virginiana exhibited needles either predominantly or in higher percentages of threes, than the contrasting described preponderance of pairs for mature individuals. Of the 25 qualitative characters evaluated, we found (1) absence of decurrency glaucescence distinguishes 2- to 5-year-old saplings of P. taeda from P. echinata and P. virginiana, and (2) absence of stomatal plugs distinguishes P. virginiana from the others. A diagnostic key to saplings is provided.