Notes from ISA study session Within the ISA Tree Risk Assessment Qualification (TRAQ 3.0) methodology, overall tree risk is evaluated as a function of four interacting components: Target, Likelihood of Failure, Likelihood of Impact, and Consequences . Collectively, these elements determine the probability and severity of harm associated with a tree or tree part failure. The session summarized here focused primarily on the Target  component and the factors that influence targe

Woody tree trunks exhibit a complex internal structure that reflects their functions in transport, support, storage, and long-term growth. Unlike herbaceous stems, tree trunks undergo secondary growth, resulting in an increase in diameter over time. This growth is produced by lateral meristems and gives rise to the characteristic tissues of wood and bark.

Accurate tree identification relies heavily on vegetative characteristics, particularly when reproductive structures such as flowers or fruits are absent. Bud arrangement, twig anatomy, leaf morphology, and growth form provide reliable diagnostic features that remain visible for much of the year. Understanding how these traits vary among angiosperms allows for systematic identification across seasons and habitats.

Successful tree transplanting depends on an understanding of plant adaptability, root biology, and soil–root interactions. While trees possess an inherent capacity to tolerate environmental variation, transplanting represents a significant physiological disturbance. Proper site preparation, planting technique, and early management are therefore critical to long-term establishment and structural stability.

Notes from ISA exam study session Soils function as chemically active systems largely because soil particles carry electrical charges. Clay minerals and organic matter possess a net negative charge, which allows them to attract and temporarily retain positively charged nutrient ions. This property underlies cation exchange capacity, the soil’s ability to hold and exchange nutrient cations such as calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), ammonium (NH₄⁺), iron (Fe

Plant growth depends on mineral nutrients that occur in soil as dissolved ions or weakly bound to soil particles. While carbon is obtained from atmospheric carbon dioxide and hydrogen and oxygen from water, all remaining essential nutrients are absorbed through roots in specific chemical forms. Nitrogen is taken up primarily as nitrate (NO₃⁻), a highly mobile anion, and as ammonium (NH₄⁺), a cation that can be retained on soil exchange sites.