The Royal Botanic Gardens and Domain Trust, The Australian Botanic Garden, Mount Annan, NSW 2567, Australia.
AoB Plants. 2014 Apr 29;6(0). doi: 10.1093/aobpla/plu011. Print 2014.
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.
幼苗生长速度对森林动态有重要的长期影响。环境变量，如光照条件和土壤因素，对幼苗生长有强烈的影响。在野外，Wollemia nobilis 幼苗生长在非常酸性的土壤（pH 值约为 4.3）中，这些土壤处于非常阴暗的地点（约 3%的全日照）。为了研究这两个因素对年轻的 Wollemia nobilis 幼苗生长的相对影响，我们进行了一项温室实验，在两种土壤 pH 值（4.5 和 6.5）下，在三种光照水平下（低光 5%、中光 15%和高光 50%）种植幼苗。测量了茎长和茎直径，计数了茎数和枝数，并分析了叶绿素和类胡萝卜素含量。一般来说，植物生长的增加与光照的增加以及无论光照处理如何，pH 值的降低有关，并且在低 pH 值下色素含量更高。在低 pH 值/高光处理组合中，植物的最大茎生长发生。然而，在低 pH 值/中光下，茎数最高。我们假设，在光照处理中，Wollemia nobilis 的茎发育存在这些差异是由于该物种对光照的不同繁殖策略：在高光下有更多的茎生长，在低光下有更多的多茎投资。Wollemia nobilis 栖息地的低光照水平可能是限制茎生长的关键因素，从而限制了从幼苗到成年的 Wollemia nobilis 的繁殖。光照和土壤 pH 值是这个受威胁的残余雨林物种生长的两个关键因素。
