Looking for age-related growth decline in natural forests: unexpected biomass patterns from tree rings and simulated mortality
Looking for age-related growth decline in natural forests: unexpected biomass patterns from tree rings and simulated mortality
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DOI：
10.1007/s00442-014-2881-2
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发表时间：
2014-05-01
期刊：
影响因子：
2.7
通讯作者：
Bradford, John B.
中科院分区：
文献类型：
--
作者：
Foster, Jane R.;D'Amato, Anthony W.;Bradford, John B.
森林生物量增长几乎普遍被认为在林分发展的早期，接近郁闭，达到峰值，之后将趋于平稳或下降。用于建立递减模式的时间序列和小区重新测量方法受到局限性和粗糙的时间细节。我们结合每年的树木年轮测量和死亡率模型，以解决两个问题：第一，如何假设树木的生长和死亡率的影响重建的生物量增长？第二，在什么情况下生物量生产遵循早期达到峰值然后下降的模式？我们集成了三个随机死亡率模型与人口普查树木年轮数据集从八个温带森林类型，重建林分水平的生物量增量（在明尼苏达州，美国）。我们比较了死亡率模型，森林类型和立场之间的增长模式。死亡率模型之间的峰值生物量增长的时间变化显着，峰值20 - 30年前，死亡率是随机的树木生长和大小，比死亡率有利于缓慢增长的个人。随机或U形死亡率（最高的小树或大树）产生的峰值增长比单独存活的树样本高25 - 30%。平均年龄，单种班克松或糖槭林的生长趋势相似的早期高峰和下降的预期。然而，我们观察到不断增加的生物量增长，在较老的，低生产力的森林栎红，白蜡，和崖柏。树轮重建估计活生物量增长的年度变化，并确定了比以前的方法更多样化的发展模式。这些详细的，长期的生物量发展模式是至关重要的检测最近的增长对全球变化的反应和模拟未来的森林动态。
Forest biomass growth is almost universally assumed to peak early in stand development, near canopy closure, after which it will plateau or decline. The chronosequence and plot remeasurement approaches used to establish the decline pattern suffer from limitations and coarse temporal detail. We combined annual tree ring measurements and mortality models to address two questions: first, how do assumptions about tree growth and mortality influence reconstructions of biomass growth? Second, under what circumstances does biomass production follow the model that peaks early, then declines? We integrated three stochastic mortality models with a census tree-ring data set from eight temperate forest types to reconstruct stand-level biomass increments (in Minnesota, USA). We compared growth patterns among mortality models, forest types and stands. Timing of peak biomass growth varied significantly among mortality models, peaking 20-30 years earlier when mortality was random with respect to tree growth and size, than when mortality favored slow-growing individuals. Random or u-shaped mortality (highest in small or large trees) produced peak growth 25-30 % higher than the surviving tree sample alone. Growth trends for even-aged, monospecific Pinus banksiana or Acer saccharum forests were similar to the early peak and decline expectation. However, we observed continually increasing biomass growth in older, low-productivity forests of Quercus rubra, Fraxinus nigra, and Thuja occidentalis. Tree-ring reconstructions estimated annual changes in live biomass growth and identified more diverse development patterns than previous methods. These detailed, long-term patterns of biomass development are crucial for detecting recent growth responses to global change and modeling future forest dynamics.