Pinus resinosa Ait. seedlings planted under dense Corylus in northern Minnesota were studied to evaluate the effect of two light levels and three moisture levels on their growth. Precipitation was much above average during the first field season, but slightly below average during the second; no severe drought period was encountered. The elimination of either form of competition improved all aspects of seedling growth, but the removal of competition for light invariably produced a larger growth response than did the removal of competition for moisture. No unshaded seedlings died during the 2-year study, whereas 38 percent of the shaded seedlings died regardless of whether they were trenched or untrenched. Best growth resulted when both forms of competition were eliminated. Dry-matter increase, in particular, was only mediocre if either factor was limiting. A decided interdependence or interaction between the two factors was evident in all facets of growth observed (height growth, size of buds, length and number of needles, stem diameter growth, root growth, and dry-matter production).
Document Type: Journal Article
Research Forester, Pacific Southwest Forest and Range Expt. Sta., Forest Service, U.S. Dept. Agric.