Piper Frida I, Fajardo Alex
Centro de Investigación en Ecosistemas de la Patagonia (CIEP) Almirante Simpson 471, 5951822 Coyhaique, Chile
Instituto Milenio de Ecología y Biodiversidad (IEB), 7800003 Santiago, Chile.
Tree Physiol. 2016 Nov;36(11):1400-1408. doi: 10.1093/treephys/tpw063. Epub 2016 Aug 18.
Carbon (C) storage is considered a key component to plant survival under drought and shade, although the combined effects of these factors on survival remain poorly understood. We investigated how drought and shade alter the C dynamics and survival of tree seedlings, and whether drought limits the access to or usage of stored C. We experimentally applied two levels of soil humidity (well-watered versus drought, the latter induced by dry-down) and light availability (light versus complete darkness) on 1-year-old seedlings of Acer pseudoplatanus L. for 3 months. We quantified the survival, biomass, growth rate and non-structural carbohydrates (NSC) of seedlings at their time of death or at the end of the experiment for those that survived. We found that the soil dried out faster when drought was combined with light than when it was combined with complete darkness. Seedlings subjected to both drought and light showed reduced growth and reached 100% mortality earlier than any other treatment, with the highest NSC concentrations at the time of death. Seedlings exposed to both drought and complete darkness died significantly earlier than seedlings exposed to complete darkness only, but had similar NSC concentrations at time of their death, suggesting that drought accelerated the use of stored C under complete darkness. Complete darkness significantly reduced seedling growth and whole-plant NSC concentrations regardless of soil humidity, while root NSC concentrations were significantly more reduced when complete darkness was combined with drought conditions. Thus, the C dynamics in A. pseudoplatanus seedlings under complete darkness was not hindered by drought, i.e., the access and use of stored C was not limited by drought. The contrasting growth and C storage responses driven by drought under light versus complete darkness are consistent with a key role of the drought progression in the C dynamics of trees.
碳（C）储存被认为是植物在干旱和遮荫条件下生存的关键组成部分，尽管这些因素对生存的综合影响仍知之甚少。我们研究了干旱和遮荫如何改变树苗的碳动态和生存情况，以及干旱是否会限制对储存碳的获取或利用。我们对1年生的悬铃木幼苗进行了为期3个月的实验，设置了两种土壤湿度水平（充分浇水与干旱，后者通过逐渐干燥诱导）和光照条件（光照与完全黑暗）。我们对死亡时或实验结束时（对于存活的幼苗）的幼苗存活情况、生物量、生长速率和非结构性碳水化合物（NSC）进行了量化。我们发现，与完全黑暗相比，干旱与光照结合时土壤干燥得更快。同时遭受干旱和光照的幼苗生长减缓，比其他任何处理更早达到100%死亡率，死亡时NSC浓度最高。同时遭受干旱和完全黑暗的幼苗比仅暴露于完全黑暗的幼苗死亡时间显著提前，但死亡时NSC浓度相似，这表明干旱加速了在完全黑暗条件下储存碳的利用。无论土壤湿度如何，完全黑暗显著降低了幼苗生长和全株NSC浓度，而当完全黑暗与干旱条件结合时，根系NSC浓度降低得更为显著。因此，在完全黑暗条件下悬铃木幼苗的碳动态不受干旱阻碍，即储存碳的获取和利用不受干旱限制。干旱在光照与完全黑暗条件下对生长和碳储存的不同响应，与干旱进程在树木碳动态中的关键作用相一致。
