Beijing Forestry University, Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Engineering Research Center of Soil and Water Conservation, Beijing, 100083, China.
Sci Rep. 2018 Jan 10;8(1):308. doi: 10.1038/s41598-017-18694-z.
Tree-level intrinsic water-use efficiency (iWUE) is derived from the tree-ring C isotope composition (δC) and is an important indicator of the adaptability for trees to climate change. However, there is still uncertainty regarding the relationship between long-term forest ecosystem carbon sequestration capacity and iWUE. To determine whether elevated atmospheric CO concentration (Ca) increase iWUE and tree growth (basal area increment, BAI), dendrochronological methods and stable isotope analyses were used to examine annual changes in the tree-ring width and carbon isotope composition (δC) of Platycladus orientalis in northern China. The iWUE derived from δC has increased significantly (p < 0.01). Long-term iWUE trend was largely and positively driven by the elevated atmospheric CO concentration and temperature. We observed a general increase in averaged BAI, which had significant positive correlation with iWUE (R = 0.3186, p < 0.01). Increases in iWUE indeed translated into enhanced P. orientalis growth in semi-arid areas of northern China. Elevated atmospheric CO concentration significantly (p < 0.01) stimulated P. orientalis biomass accumulation when Ca was less than approximately 320 ppm in the early phase; however, this effect was not pronounced when Ca exceeded 320 ppm.
树木的整树尺度内在水分利用效率（iWUE）由树木年轮的碳同位素组成（δC）得出，是树木适应气候变化的重要指标。然而，长期森林生态系统碳固存能力与 iWUE 之间的关系仍存在不确定性。为了确定大气 CO 浓度（Ca）升高是否会增加 iWUE 和树木生长（胸径年生长量，BAI），本研究利用树木年代学方法和稳定同位素分析，研究了中国北方侧柏的树木年轮宽度和碳同位素组成（δC）的年际变化。δC 得出的 iWUE 显著增加（p < 0.01）。长期 iWUE 趋势主要受大气 CO 浓度和温度升高驱动。我们观察到平均 BAI 普遍增加，iWUE 与 BAI 呈显著正相关（R = 0.3186，p < 0.01）。iWUE 的增加确实导致了中国北方半干旱地区侧柏生长的增强。在大气 CO 浓度早期阶段（Ca 约小于 320 ppm），Ca 显著（p < 0.01）刺激了侧柏生物量的积累；然而，当 Ca 超过 320 ppm 时，这种效应并不明显。
