Interactions between planted black spruce seedlings and grass under alternative vegetation management treatments

摘要

A greenhouse experiment of mono and bi-cultured black spruce seedlings and grass was conducted to evaluate alternatives to herbicide use for forest regeneration and demonstrate a proposed vector competition analysis system for screening integrated forest vegetation management practices. The alternative treatments, pre-planting nutrient loading and post-planting fertilization, were tested in an additive design to identify response interactions. Loading increased nutrient uptake but not growth performance of the seedlings probably because of high soil fertility and low loading levels. Fertilization stimulated more growth in grass and seedlings in mono-culture (543 and 95%) than in bi-culture (162 and 63%) signifying that seedlings were more competitive than the grass for limiting resources. Nitrogen was most limiting as determined by vector diagnosis and a bivariate regression approach that compared competitive growth and nutrient uptake directly. The combined approach consistently depicted nutrient responses to be relatively greater than biomass responses to all treatments involving fertilizers, exemplifying the sensitivity or the model. The model was developed further as a vector competition analysis system to screen treatments and prioritize sites in terms of integrative vegetation control. Additional greenhouse treatments, such as shading plus fertilization and droughting, and other response data from the literature were used to demonstrate the application of vector competition models as a decision support tool for various forest management scenarios. For operational use, the technique needs extensive field calibration and validation in pilot projects.