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/生物量（aboveground carbon/biomass）？若可以，利用树木年轮数据重建过去生物量时，研究人员能追溯到多久远的时间？这些问题的答案将显著影响我们对陆地碳汇（terrestrial carbon sink）动态的理解。长期的生物量树木年轮记录可揭示从年内（intra-annual）到年度再到数十年尺度（multidecadal）的变化，而这些变化无法通过非年度时间步长的森林普查数据（forest census data）解析。此外，尽管这些动态可通过遥感（remote sensing）解析，但大多数遥感产品（remotely-sensed products）的时长仅为20年或更短。通过获取长期的碳生物量记录，我们不仅能识别生物量的主导驱动因素（dominant drivers），还能了解这些驱动因素的重要性如何随不同时期环境因素（如气候、空气污染、干扰）的变化而改变。

为验证这些及其他问题，我们从新罕布什尔州皮斯加州立森林中北圆池塘附近设置的4个半径30米样地收集了树木年轮记录。其中2个样地位于阔叶林为主的森林，另外2个位于以栎类混交针叶林为主的森林。我们可通过异速生长方程（allometric equations）将这些数据转换为生物量，并将树木年轮推断的地上生物量与历史普查数据进行比较。尽管1938年9月的一场强飓风摧毁了这些林分东南偏南约3.5公里处某林分的80%，且北圆池塘附近的林分位于北向和西北向山坡，可能免受强热带风的影响，但它们也受到了1938年飓风的干扰。然而，该区域存在一些非常古老的树木和树木斑块，同时我们推测20世纪60年代的伐木活动影响了部分样地（如北圆池塘样地1）。此后林分已恢复生长，我们设置的样地可用于了解受严重干扰森林的恢复过程及碳动态。这些样地中部分树木的更新日期（recruitment dates）已发表于Pederson等人（2017）的研究中。

Pederson, N., Young, A. B., Stan, A. B., Ariya, U., Martin-Benito, D. 2017. 温带湿润森林干扰相关的易获取树木动态研究成果。载于：Amoroso, M. M., Daniels, L. D., Baker, P. J., Camarero, J. J. 主编，《树木年代生态学（dendroecology）：树木年轮分析在生态学研究中的应用》，Springer出版社，瑞士尚姆。