Forest Botany and Tree Physiology, University of Goettingen, 37077 Göttingen, Germany.
Laboratory for Radio-Isotopes, University of Goettingen, 37077 Göttingen, Germany.
Tree Physiol. 2018 Jan 1;38(1):37-51. doi: 10.1093/treephys/tpx146.
To investigate how long-lived forest trees cope with low soil phosphorus (P) availabilities, we characterized P nutrition of beech (Fagus sylvatica, L.) in soils from P-rich and P-poor beech forests throughout an annual growth cycle. Young trees were excavated with intact soil cores in mono-specific beech forests, kept under common garden conditions, and used for 33P labeling, analyses of P uptake, P content and biomass during five phenological stages (dormancy in winter, bud swelling in early spring, mature leaves in early and late summer, and senescent leaves in fall). Seasonal allocation patterns showed that young, emerging leaves were preferred sinks for P under P-poor conditions, thereby keeping foliar P concentrations at levels similar to those of trees grown in P-rich soil. Phosphorus concentrations in stems and roots of trees from the P-poor conditions were lower than those from P-rich conditions. Coarse roots were the main P storage tissue, supplying inorganic P to newly formed leaves, originating from the inorganic and organic P pools under low and high P conditions, respectively. Beech trees in P-poor soil exhibited net biomass increment early in the annual growth along with a strong P deficit, which was replenished by enhanced uptake in late summer and fall. Trees in P-rich soil grew until late summer, and showed a moderate P decline in organic pools and recovery late in fall, which coincided with elevated P uptake from soil. Beech in P-poor soil produced more biomass per unit of P but at a slower growth rate than those in P-rich soil, thereby exhibiting similar P-use efficiencies. Temporal decoupling of growth and P acquisition in combination with internal P trade-off between storage tissues and leaves facilitated flexible acclimation of beech to a wide range of soil P availabilities.
为了研究长寿树种如何应对土壤磷（P）供应不足的问题，我们对来自富磷和贫磷山毛榉林中的山毛榉的 P 营养状况进行了特征描述。在单一种群的山毛榉林中，我们使用完整的土壤芯挖掘出幼树，在普通花园条件下进行保存，并用于 33P 标记、磷吸收、磷含量和生物量分析，共进行了五个物候阶段（冬季休眠、早春萌芽、夏初和夏末成熟叶、秋季衰老叶）。季节性分配模式表明，在 P 缺乏的情况下，新出现的幼叶是 P 的首选吸收器，从而使叶片 P 浓度保持在与富 P 土壤中生长的树木相似的水平。来自贫 P 条件的树木的茎和根中的 P 浓度低于来自富 P 条件的树木。粗根是主要的 P 储存组织，为新形成的叶片提供无机 P，这些 P 分别来自低 P 和高 P 条件下的无机 P 和有机 P 库。在 P 贫土壤中的山毛榉在年度生长的早期表现出净生物量增量，同时伴随着强烈的 P 亏缺，这在夏末和秋季通过增强吸收得到补充。在富 P 土壤中的树木一直生长到夏末，在有机库中 P 含量适度下降，并在秋季后期恢复，这与土壤中 P 吸收的增加相对应。在 P 贫土壤中的山毛榉每单位 P 产生的生物量更多，但生长速度比富 P 土壤中的树木慢，因此表现出相似的 P 利用效率。生长和 P 吸收的时间解耦，以及储存组织和叶片之间的内部 P 权衡，使山毛榉能够灵活地适应广泛的土壤 P 供应。
