Density Anomalies in White Pine at Harvard Forest 2019

The density of wood is a primary determinant of the amount of carbon sequestered in forests. For boreal and Mediterranean ecosystems, anomalies from the typical intra-annual density increase in radial growth of conifers are predominantly related to drought. We took 41 wood samples at breast height, ten additional samples near branches, and seven samples from the top of 41 white pines to determine the spatial distribution of density anomalies throughout the stem. We measured the ring width, density anomaly presence, position within a ring, and arc of density anomalies at multiple heights. Even in a mesic forest density anomalies in white pine are predominantly occurring during drier growing seasons. Moreover, we examined the spatial extent of density anomalies within the stems of white pines and discovered density anomalies are more likely to occur near branches, at the top of the tree, and in wider rings. Furthermore, the position of the density anomalies within the rings was remarkably consistent with the anomalies occurring roughly 80% into the fully formed ring at all heights for high-frequency years only as well as all years Density anomalies seem to be triggered by exogenous factors but their distribution within the stem varies along endogenous gradients, thus better understanding these systematic anomalies can help us to understand how wood formation has reacted and will respond to the environment and changes therein.