Kress Anne, Saurer Matthias, Büntgen Ulf, Treydte Kerstin S, Bugmann Harald, Siegwolf Rolf T W
Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
Oecologia. 2009 May;160(2):353-65. doi: 10.1007/s00442-009-1290-4. Epub 2009 Feb 14.
Larch budmoth (LBM, Zeiraphera diniana Gn.) outbreaks cause discernable physical alteration of cell growth in tree rings of host subalpine larch (Larix decidua Mill.) in the European Alps. However, it is not clear if these outbreaks also impact isotopic signatures in tree-ring cellulose, thereby masking climatic signals. We compared LBM outbreak events in stable carbon and oxygen isotope chronologies of larch and their corresponding tree-ring widths from two high-elevation sites (1800-2200 m a.s.l.) in the Swiss Alps for the period AD 1900-2004 against isotope data obtained from non-host spruce (Picea abies). At each site, two age classes of tree individuals (150-250 and 450-550 years old) were sampled. Inclusion of the latter age class enabled one chronology to be extended back to AD 1650, and a comparison with long-term monthly resolved temperature data. Within the constraints of this local study, we found that: (1) isotopic ratios in tree rings of larch provide a strong and consistent climatic signal of temperature; (2) at all sites the isotope signatures were not disturbed by LBM outbreaks, as shown, for example, by exceptionally high significant correlations between non-host spruce and host larch chronologies; (3) below-average July to August temperatures and LBM defoliation events have been coupled for more than three centuries. Dampening of Alps-wide LBM cyclicity since the 1980s and the coincidence of recently absent cool summers in the European Alps reinforce the assumption of a strong coherence between summer temperatures and LBM defoliation events. Our results demonstrate that stable isotopes in tree-ring cellulose of larch are an excellent climate proxy enabling the analysis of climate-driven changes of LBM cycles in the long term.
落叶松芽蛾（LBM，Zeiraphera diniana Gn.）的爆发会导致欧洲阿尔卑斯山寄主亚高山落叶松（Larix decidua Mill.）年轮中细胞生长出现明显的物理变化。然而，目前尚不清楚这些爆发是否也会影响年轮纤维素中的同位素特征，从而掩盖气候信号。我们将1900年至2004年期间瑞士阿尔卑斯山两个高海拔地点（海拔1800 - 2200米）落叶松的稳定碳氧同位素年表及其相应的年轮宽度中的LBM爆发事件，与从非寄主云杉（Picea abies）获得的同位素数据进行了比较。在每个地点，对两个年龄组的树木个体（150 - 250岁和450 - 550岁）进行了采样。纳入后一个年龄组使得一个年表能够追溯到公元1650年，并与长期的月分辨率温度数据进行比较。在这项局部研究的限制范围内，我们发现：（1）落叶松年轮中的同位素比率提供了一个强烈且一致的温度气候信号；（2）在所有地点，同位素特征并未受到LBM爆发的干扰，例如，非寄主云杉和寄主落叶松年表之间异常高的显著相关性就表明了这一点；（3）三个多世纪以来，7月至8月低于平均水平的温度与LBM落叶事件一直相关。自20世纪80年代以来阿尔卑斯山范围内LBM周期性的减弱以及欧洲阿尔卑斯山近期凉爽夏季的缺失，强化了夏季温度与LBM落叶事件之间存在强烈一致性的假设。我们的结果表明，落叶松年轮纤维素中的稳定同位素是一种出色的气候代用指标，能够长期分析气候驱动的LBM周期变化。
