Growing up or growing out? How soil pH and light affect seedling growth of a relictual rainforest tree

Seedling growth rates can have important long-term effects on forest dynamics. Environmental variables such as light availability and edaphic factors can exert a strong influence on seedling growth. The aim of a new article by Offord et al., published in AoB PLANTS, was to uncover the drivers of seedling growth in a rare rainforest conifer. Wollemia nobilis is limited to canyons, characterized by deeply shaded understories and acid soils. In a glasshouse experiment, the authors grew seedlings at a range of pH and light levels. Growth increased with increasing light, and was higher at low pH, regardless of light. The number of stems, however, was greatest in lower light. Thus Wollemia nobilis seedlings may vary their architecture – growing up when light is high, and growing out when light is lower. Nevertheless, low light is likely the key limitation of W. nobilis growth in the wild.