Growth and Nutritional Interactions of Nutrient-Loaded Black Spruce Seedlings with Neighboring Natural Vegetation Under Greenhouse Conditions

Abstract

Abstract Nutrient loading during nursery culture to improve early outplanting performance of black spruce (Picea mariana [Mill.] BSP) seedlings on weed prone sites is increasingly practiced in northern Ontario, but more insight is needed on the competitive mechanisms involved. Vector competition analysis was used to examine nutrient loading on interspecific growth and nutritional interactions between planted seedlings and neighboring natural vegetation under controlled greenhouse conditions. Nutrient loaded and conventional (nonloaded) seedlings were raised in a commercial green-house and then transplanted in bioassay soil substrates retrieved from two forest sites [Hardwood (OG 10) and Feathermoss (OG 4)], with weeds removed or left to grow naturally. Weed control increased seedling growth on the Hardwood substrates (103–194% height increase), but had no effect on the Feathermoss substrates suggesting that no seedling–natural vegetation interactions occurred on the latter site. Nutrient loading, however, countered weed competition on the competition-prone Hardwood site, reflecting the high competitiveness of these seedlings. Vector competition analysis revealed that tree-vegetation interactions on the Hardwood site caused antagonistic nutrient dilution primarily due to competition for N. Nutrient interactions were more symmetric with nutrient-loaded trees, indicating that these seedlings were less sensitive to competition than were nonloaded seedlings. For. Sci. 48(1):77–84.