Phenotypic plasticity versus ecotypic differentiation under recurrent summer drought in two drought-tolerant pine species

1. Despite worldwide reports of high tree mortality, growing evidence indicates that many tree species are well adapted to survive repeated dry spells. The drought resilience of trees is related to their phenotypic plasticity and ecotypic differentiation. Whether these two mechanisms act at the same organisational level of a tree and involve similar plant traits is still unknown.

2. We assessed phenotypic plasticity and ecotypic differentiation across four populations of Pinus sylvestris and Pinus nigra seedlings grown for three years under a recurrent summer drought treatment or well-watered control conditions in a common garden. We measured the response to the summer drought treatment of a total of 26 traits including shoot and needle morphology, needle anatomy, and foliar macronutrients, and related the traits to the growing season water deficit (GSWD) at the location of the seed origin.

3. Foliar phenotypic plasticity in response to recurrent summer drought was surprisingly lo...

1. 尽管全球范围内均有树木高死亡率的报道，越来越多的证据表明，诸多树木物种已能够良好适应反复出现的干旱期。树木的耐旱性与其表型可塑性（phenotypic plasticity）和生态型分化（ecotypic differentiation）密切相关，但这两种机制是否作用于树木的同一组织水平、是否涉及相似的植物性状，目前仍不明朗。
2. 本研究在同质园（common garden）环境中，对欧洲赤松（Pinus sylvestris）和黑松（Pinus nigra）的4个种群的实生苗开展了为期3年的实验，设置反复夏季干旱处理与充分浇水的对照条件，以此评估其表型可塑性与生态型分化。我们共测定了26个涵盖枝条与针叶形态、针叶解剖结构以及叶片大量营养元素在内的性状对夏季干旱处理的响应，并将这些性状与种子来源地的生长季水分亏缺（GSWD）进行关联分析。
3. 树木在应对反复夏季干旱时的叶片表型可塑性出人意料地低……