Compensatory growth in shoot populations of young white pine trees

Summary

White pine (Pinus strobus L.) trees have shoot populations composed of subpopulations of terminal and lateral shoots. I tested whether the subpopulations would show compensatory (increased) growth when separated from each other. Ten-year-old white pine (Pinus strobus L.) trees growing under an oak (Quercus) overstory were untreated or treated in winter by removing either all terminal, or all lateral buds (10 trees per treatment). Growth was compared between control and treated shoot subpopulations. In the 1st year, shoot-length frequency distributions were similar between control and treated subpopulations. There was significant compensatory shoot elongation (mean of 1.5 cm per shoot) in both treated subpopulations. In the 2nd year each subpopulation produced both terminal and lateral shoots. Shoot-length frequency distributions were similar, but shifted toward longer shoots in treated populations. Shoot number, mean length and total shoot length were greater in treated populations. The increased growth in treated subpopulations was due both to differences in parent shoot length and to compensatory shoot production and elongation.