A major goal of forest ecosystem management is to conserve biological diversity and satisfy the continued demand for wood products. Silvicultural practices using variable regimes of fertilization and thinning may have the potential to create a diversity of forest habitats and wildlife to meet biodiversity goals and sustained wood production. This study was designed to test the hypotheses that large-scale pre-commercial thinning to various stand densities, at ages 12-14 years, combined with repeated fertilization, would, over a 7-year treatment period, enhance: (1) productivity of lodgepole pine (Pinus contorta) crop trees, and (2) species diversity and structural diversity of vegetation. Study areas were located near Summerland, Kelowna, and Williams Lake in south-central British Columbia, Canada. Each study area had nine treatments: four pairs of stands thinned to densities of ~250 (very low), ~500 (low), ~1000 (medium), and ~2000 (high) stems/ha with one stand of each pair fertilized three times at 2-year intervals, and an unthinned stand. Productivity of crop trees and coniferous stand structure were measured at 5-years post-treatment (1993-1998). Understory vegetation were sampled annually from 1993 to 2000. At 5 years since PCT, crop trees grew significantly faster in diameter in the low- than high-density and in the fertilized than unfertilized stands. Height growth of crop trees was significantly greater in the high- than low-density stands with no difference between unfertilized and fertilized stands. Mean crown volume index of herbs was significantly higher in fertilized than unfertilized stands, but volumes of shrubs and trees were unaffected. Volumes of mosses and lichens declined significantly in fertilized stands. Stand density had no effect on volume of vegetative layers. Mean species richness of herbs, shrubs, trees, and total vascular plants was similar among treatment stands. Mean species diversity of herbs and shrubs was significantly lower in fertilized than unfertilized stands, but trees showed no difference. Stand density had no effect on species diversity. Mean total structural diversity of vegetation (herbs, shrubs, and trees) was significantly different among stands with respect to density, with greater diversity in the low- than high-density stands. Fertilization tended to enhance this response.
T.P. Sullivan et al.
Sullivan, Thomas P., Sullivan, Drusilla S.; Lindgren, Pontus M.F.; Ransome, Douglas B.; Brockley, Robert P.; Winter, Ralph. 2004. Incremental silviculture of lodgepole pine: integration of stand productivity with non-timber values. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2004MR235