Vector competition analysis: a new approach for evaluating vegetation control methods in young black spruce plantations

Abstract

This paper reports on a new graphical analysis technique that facilitates screening alternative strategies for crop management in programs of integrated vegetation management in young forest plantations. The responsiveness of black spruce seedlings to three vegetation management measures (herbicide application, fertilization and seedling nutrient loading) on two contrasting site types (Hardwood [ST 10] and Feathermoss [ST 4]) located in northern Ontario, were compared and evaluated using vector competition analysis. The approach is based on vector diagnosis and regression analysis that compare growth and nutritional interactions between crop and non-crop plants competing for the same growth resources. Response parameters are examined in a bivariate model depicting vectors of changing biomass production or nutrient uptake relative to competition-free treatments. Although herbicide application reduced non-crop vegetation on both sites, it accelerated tree growth and nutrient uptake only in the herb-rich Hardwood site, but had no effect on seedlings in the Feathermoss site. Fertilization stimulated vegetation growth in the competitive Hardwood site causing seedling suppression, but stimulated both tree and non-crop vegetation growth in the Feathermoss site because of weaker competition. Preplant nutrient loading improved seedling growth and nutrition reducing competition of neighboring weeds. Vector competition analysis facilitated interpretation of plant interactive relationships and identification of limiting factors. Advantages over traditional competition indices are that both growth and nutrition parameters, as well as crop and non-crop responses are quantitatively and systematically evaluated, and that simultaneous comparisons simplified screening of the most effective treatments and sites for possible vegetation control. Key words: Competition indices, treatment screening, nutrient loading, fertilization, herbicide