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Growing up or growing out? How soil pH and light affect seedling growth of a relictual rainforest tree
Published (Version of record)CC BY V4.0, Open
Journal article
Growing up or growing out? How soil pH and light affect seedling growth of a relictual rainforest tree
AoB plants, Vol.6
2014
PMCID: PMC4004931
PMID: 24790132
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Abstract
Our aim 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, we grew seedlings at a range of pH and light levels. Growth increased with increasing light, and was higher at low pH, regardless of light. Number of stems, however, was greatest in lower light. 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. 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. In the wild, seedlings of Wollemi pine (Wollemia nobilis) grow on very acid soils (pH ∼4.3) in deeply shaded sites (∼3 % full sunlight). To examine the relative influences of these two factors on the growth of young W. nobilis seedlings, we conducted a glasshouse experiment growing seedlings at two soil pH levels (4.5 and 6.5) under three light levels: low (5 % full sun), medium (15 %) and high (50 %). Stem length and stem diameter were measured, stem number and branch number were counted, and chlorophyll and carotenoid content were analysed. In general, increased plant growth was associated with increased light, and with low pH irrespective of light treatment, and pigment content was higher at low pH. Maximum stem growth occurred in plants grown in the low pH/high light treatment combination. However, stem number was highest in low pH/medium light. We hypothesize that these differences in stem development of W. nobilis among light treatments were due to this species' different recruitment strategies in response to light: greater stem growth at high light and greater investment in multiple stem production at low light. The low light levels in the W. nobilis habitat may be a key limitation on stem growth and hence W. nobilis recruitment from seedling to adult. Light and soil pH are two key factors in the growth of this threatened relictual rainforest species.
Details
- Title
- Growing up or growing out? How soil pH and light affect seedling growth of a relictual rainforest tree
- Creators
- Catherine A Offord - Royal Botanic Gardens and Domain Trust, Mount AnnanPatricia F Meagher - Royal Botanic Gardens and Domain Trust, Mount AnnanHeidi C Zimmer - University of Melbourne
- Publication Details
- AoB plants, Vol.6
- Publisher
- Oxford University Press
- Identifiers
- 991012893700102368
- Academic Unit
- Forest Research Centre; School of Environment, Science and Engineering; Faculty of Science and Engineering; Science
- Language
- English
- Resource Type
- Journal article