Authors: Kamaluddin, Mohammed¹; Chang, Scott X.²; Curran, Michael P.³; Zwiazek, Janusz J.¹

Source: Forest Science, Volume 51, Number 6, December 2005 , pp. 513-521(9)

Abstract:

We investigated the effects of soil compaction and forest floor removal on growth and physiology of lodgepole pine (Pinus contorta ex Loud. var. latifolia Engelm.) and Douglas-fir (Pseudotsuga menziesii var. glauca [Baissn.] Franco) seedlings on a calcareous long-term soil productivity (LTSP) study site near Invermere, British Columbia. Treatments consisted of factorial combinations of soil compaction (noncompacted versus compacted) and forest floor removal (forest floor intact versus forest floor removed) as well as a remedial (rehabilitation) treatment of deep ripping following soil compaction. The experiment was not replicated at the treatment plot level, therefore no statistically based mean comparisons were made. After two growing seasons, we found that the two tree species responded differently to those treatments. Lodgepole pine height and diameter growth and unit needle-weight (dry mass per unit needle) averaged 25, 51, and 30% greater, respectively, in the rehabilitation than in the other treatments, whereas Douglas-fir responded to the rehabilitation treatment by increasing stem diameter growth by 27%, but not height growth (a change of 9%). Forest floor removal decreased height growth in lodgepole pine by 11%, but increased diameter growth in Douglas-fir by 15%. The decreases in growth for lodgepole pine in the forest floor removal treatments were accompanied by lower foliar N concentrations. Foliar N concentrations were positively correlated with rates of net photosynthesis (r = 0.69, P = 0.004) and height growth (r = 0.76, P = 0.004) in lodgepole pine, but not in Douglas-fir. Low N supply (as observed for lodgepole pine) and depletion of soil moisture as a result of forest floor removal likely played a role in shaping the growth and physiological responses of the trees in this study. FOR. SCI. 51(6):513–521.

Keywords: Soil disturbance; long-term soil productivity (LTSP) network; foliar N; photosynthesis; shoot water potential; drought tolerance; environmental management; forest; forest management; forest resources; forestry; forestry research; forestry science; natural resources; natural resource management

Document Type: Regular article

Affiliations: 1: Centre for Enhanced Forest Management, Department of Renewable Resources University of Alberta 442 Earth Sciences Building Edmonton Alberta Canada T6G 2E3 2: Department of Renewable Resources University of Alberta Edmonton Alberta Canada T6G 2E3 Phone: (780) 492-6375;, Fax: (780) 492-1767, Email: scott.chang@ualberta.ca 3: Ministry of Forests, Forest Sciences Program 1907 Ridgewood Road Nelson British Columbia V1L 6K1; University of British Columbia Vancouver British Columbia Canada V6T 1Z4