Potential sampling bias in long-term forest growth trends reconstructed from tree rings: A case study from the Italian Alps
Potential sampling bias in long-term forest growth trends reconstructed from tree rings: A case study from the Italian Alps
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DOI：
10.1016/s0378-1127(98)00242-4
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发表时间：
1998-09-16
影响因子：
3.7
通讯作者：
Innes, JL
中科院分区：
文献类型：
--
作者：
Cherubini, P;Dobbertin, M;Innes, JL
对树木长期生长趋势的年轮研究经常产生有争议的结果。在这类研究中，通常选取林分中直径最大的树木作为样本。通过研究两种年龄不均匀的亚高山挪威云杉（Picea abies (L.)）中所有树木的过去直径，我们评估了林分动态对长期生长趋势的影响。喀斯特)位于意大利东阿尔卑斯山，由环宽重建而成。这些树按照直径排序，每组12棵树（最大的12棵，最小的12棵等）。不同直径组有不同的增量曲线。在这两个林分中，1992年最大的12棵树的生长速度并没有一直快于较小的树。这表明过去已经发生了直径排序的变化，未来可能会发生变化。在林分发育过程中，单株树木的相对位置发生变化，按直径排序。在任何时候，直径最大的树可能并不总是最大的树，也可能不会继续如此。在给定的年份里，最大的树平均比其他树长得慢，这将在未来成为最大的树。采伐前最大的树木的平均年表，以及目前（1992年）已不在前12名之列的树木的平均年表，以及进入前12名的树木的平均年表显示出非常不同的生长趋势。如果脱离背景进行分析，人们对这些数据的解读就会不同，从而得出有关长期增长趋势的不同结论。当只对12棵直径最大的树进行采样时，可能会出现偏差，因为这些树可能不是开放生长的，过去也没有竞争。因此，林分动态和采样策略的偏差可能严重影响长期生长的研究。在今后的研究中，应评价林分内所有径级的生长模式，而不是局限于最大径级的取样。(C) 1998爱思唯尔科学有限公司
Tree-ring studies of long-term growth trends have often produced controversial results. In such studies, the largest-diameter trees in a stand are usually sampled. We assessed the influence of stand dynamics on long-term growth trends by examining the past diameters of all the trees living in two uneven-aged subalpine Norway spruce (Picea abies (L.) Karst.) stands in the Italian eastern Alps, as reconstructed from ring widths. The trees were ordered according to diameter, and groups of 12 trees (the 12 largest, the 12 smallest, etc.) were formed. Different diameter groups have different increment curves. In both stands, the 12 largest trees in 1992 have not had consistently faster growth rates than smaller trees. This indicates that changes in diameter ranking order have occurred in the past and may be expected in the future. During stand development, changes occur in the relative position of individual trees, as ordered by diameter. The largest-diameter trees, at any time, may not always have been the largest trees and may not continue to be so. In a given year, the largest trees on average grow slower than other trees, which will become the largest in the future. The mean chronologies of the trees that were among the largest, prior to the harvest, and which presently (in 1992) are no longer in the top 12, and the mean chronologies of the trees that have moved up into the top 12 show very different growth trends. If analysed out of context, they would be interpreted differently, leading to different conclusions on long-term growth trends. when only the 12 largest-diameter trees are sampled, a bias may be present, as the trees may not have been open grown and free of competition in the past. Consequently, studies of long-term growth may be seriously affected by bias attributable to stand dynamics and sampling strategies. In future studies, the growth patterns of all diameter classes in a stand should be assessed, rather than restricting the sampling to the largest diameters. (C) 1998 Elsevier Science B.V.