Phenology and Carbon Allocation of Roots at Harvard Forest 2011-2013

The objective of this study is to estimate the phenology and partitioning of C allocated belowground across the growing season at Harvard Forest in two hardwood stands dominated by Quercus rubra and Fraxinus americana, respectively, and one conifer stand dominated by Tsuga canadensis. The phenology of fine root production was characterized by multiple flushes of growth and mortality, especially in the red oak (Q. rubra) stand. Root exudation rate did not have a clear seasonal signal. The deciduous hardwood stands allocated C belowground earlier in the season compared to the conifer-dominated stand. Deciduous stands also allocated a greater proportion of total belowground C flux (TBCF) to root growth compared to the conifer-dominated hemlock (T. canadensis) stand. Of the three stands, red oak partitioned the greatest proportion of TBCF (~50%) to root growth, while hemlock partitioned the least.

本研究旨在估算哈佛森林内三个林分在整个生长季的物候特征与碳向地下分配的格局：两个分别以红栎（Quercus rubra）和美国白蜡（Fraxinus americana）为优势种的硬木林分，以及一个以加拿大铁杉（Tsuga canadensis）为优势种的针叶林分。细根生产的物候表现为多次生长与死亡脉冲，在红栎（Q. rubra）林分中尤为显著。根系分泌物速率未呈现明确的季节信号。相较于针叶林分，落叶硬木林分在生长季更早地将碳分配至地下部分。与以加拿大铁杉（T. canadensis）为优势种的林分相比，落叶林分配至细根生长的总地下碳通量（TBCF）占比更高。在三个林分中，红栎林分将约50%的总地下碳通量分配至细根生长，其占比为三者之最，而加拿大铁杉林分的该占比最低。