Five years of vegetation succession following vegetation management treatments in a jack pine ecosystem

Abstract

All correspondence should be directed to Doublas G. Pitt-Phone: (705) 949-9461, Fax: (705) 759-5700 dpitt@NRCan.cc.ca Five years of data on vegetation dynamics and succession are provided for six operational release treatments applied to three 2- to 4-yr-old jack pine (Pinus banksiana Lamb.) plantations in central Ontario. Treatments included 3 yr of annual noncrop vegetation removal, conventional aerial spray with glyphosate (1.42 kg ae/lia), ground application of glyplwsate with a mist blower, basal-bark application of triclopyr, motor-manual cutting (brush saw), and no treatment. Conventional aerial spraying and annual removal resulted in the greatest jack pine crop growth, with trees exceeding 90% crown closure, 7 cm in groundline diameter, and 3 in in height (stem volume index = 5.1 dm3) after 5 growing seasons. The cover of herbaceous plants was highest (30-50%) in the aerial spray plots during the obsen-ation period. Deciduous tree, shrub, and fern species remained well represented on these plots, although total cover and height were low (<35% and I m, respectively). Mist-blower find brush-saw plots contained mid-sized pine (3.5 dm3) with 69% crown closure. In contrast, untreated and basal-bark plots contained the smallest pine (2.3 dm3 and31% crown closure), likely caused by heavy competition and herbicide damage, respectively. On mist-blower and basal-bark plots, good height growth was obsen'ed on untreated deciduous trees; low-shrub and fern cover remained high (46 and 30%, respectively); and herbaceous cover increased gradually to 22 %. On brush-saw plots, recovery of woody coverwas rapid, but height growth was relatively slow. Deciduous trees and tall shrubs dominated untreated sites (> 70% cover) by the end of the fifth growing season. Successional trends suggest that aerial spray and annual removal treatments will produce pure jack pine stands at maturity; mist blower, basal bark, and brush-saw treatments may produce mixedwood stands; and untreated plots will likely be dominated by hardwoods.