Tree Ring Data from North Round Pond in Pisgah State Forest NH 1754-2015

Is it possible to reconstruct aboveground carbon/biomass from tree rings? If so, how far back in time can researchers go when using tree-ring data in the reconstruction of past biomass? Answers to these questions will have a significant impact on our understanding of dynamics in the terrestrial carbon sink. Long tree-ring records of biomass can reveal intra-annual to annual to multidecadal variations that cannot be resolved by forest census data that is not conducted at annual time steps. Additionally, while these dynamics might be resolved using remote sensing, most remotely-sensed products are only two decades or less in length. By having long records of carbon biomass, we can then identify not only the dominant drivers of biomass, but how the importance of these drivers might change during different eras as environmental factors change (e.g., climate, air pollution, disturbance). To test these and other questions, we collected tree-ring records from four 30m radius plots set in the vicinity of North Round Pond in Pisgah State Forest, New Hampshire. Two plots are set in broadleaf-dominated forests while two are set in oak-mixed conifer dominated forests. We can convert these data to biomass using allometric equations and compare tree-ring inferred aboveground biomass to the census data going back in time. While a strong hurricane in September 1938 knocked down 80% of a stand ca 3.5 km SSE of these stands and the stands in the vicinity of the North Round Pond are set on N- and NW-facing slopes, and thus potentially shielded by the strong tropical winds, they, too, were disturbed by the hurricane of 1938. However, there are some very old trees and patches of trees in this landscape, while, at the same time, we suspect some logging impacted parts of some of these plots in the 1960s, like in North Round Pond Plot 1. The forest stands have since regrown and the plots we installed can be used to understand forest recovery and carbon dynamics in a heavily disturbance forest. Recruitment dates for some of the trees from these plots have been published in Pederson et al. (2017). Pederson, N., Young, A. B., Stan, A. B., Ariya, U., Martin-Benito, D. 2017. Low-Hanging DendroDynamic Fruits Regarding Disturbance in Temperate, Mesic Forests. In: Amoroso, M. M., Daniels, L. D., Baker, P. J., Camarero, J. J., Dendroecology: Tree-Ring Analyses Applied to Ecological Studies, Springer, Cham., Switzerland.

能否通过树木年轮（tree rings）重建地上碳储量/生物量？若可行，研究人员利用树木年轮数据重建历史生物量时，可回溯至多久以前？上述问题的答案将对我们理解陆地碳汇（terrestrial carbon sink）的动态变化产生重要影响。长时序树木年轮生物量记录能够揭示年际内、年际至数十年际的变化特征，这类变化无法通过非年度步长的森林普查数据捕捉。此外，尽管遥感技术或可解析此类动态，但绝大多数遥感产品（remotely-sensed products）的时序长度仅为二十年甚至更短。通过获取长时序的碳生物量记录，我们不仅能够明确驱动生物量变化的核心因子，还能揭示随着环境因素（如气候、空气污染、干扰事件）改变，这些驱动因子的重要性在不同时期会发生何种变化。为验证上述及其他相关问题，我们在美国新罕布什尔州皮斯加州立森林北圆塘周边设置了4个半径30米的样地，采集了树木年轮数据。其中2个样地位于阔叶树占优的森林，另外2个则位于栎类混交针叶林占优的森林。我们可通过异速生长方程（allometric equations）将这些数据转换为生物量，并将树木年轮反演得到的地上生物量与回溯历史的普查数据进行对比。1938年9月的强飓风曾在距离这些样地约3.5公里的南东南方向击倒了80%的林分，而北圆塘周边的样地地处北坡和西北坡，理论上或可受到强热带风暴的庇护，但这些样地同样受到了1938年飓风的干扰。不过该区域内仍存在一些古树和树群；同时我们怀疑部分样地（如北圆塘样地1）在1960年代曾受到伐木活动的影响。此后这些林分已完成自然恢复，我们设置的样地可用于探究受严重干扰森林的恢复过程与碳动态。部分样地树木的定植年代（recruitment dates）已在Pederson等人（2017）的研究中发表：Pederson, N., Young, A. B., Stan, A. B., Ariya, U., Martin-Benito, D. 2017. 《温带中生林干扰相关的简易树木年轮动力学研究成果》，收录于：Amoroso, M. M., Daniels, L. D., Baker, P. J., Camarero, J. J. 编著，《树木年代生态学：应用于生态研究的树木年轮分析》，瑞士沙姆市，施普林格（Springer）出版社。