Response of carbon and water fluxes to environmental variability in two Eastern North American forests of similar-age but contrasting leaf-retention and shape strategies [post]

Eric R. Beamesderfer, M. Altaf Arain, Myroslava Khomik, Jason J. Brodeur, Brandon M. Burns
2020 unpublished
<p><strong>Abstract.</strong> The annual carbon and water dynamics of two Eastern North American forests were compared over a six year period from 2012 to 2017. The geographic location, forest age, soil, and climate were similar between the sites, however, the species composition varied: one was a deciduous broadleaf forest, while the other an evergreen needleleaf forest. During the 6-year study period, the mean annual net ecosystem productivity (NEP) of the coniferous forest
more » ... coniferous forest was slightly higher and more variable (218 ± 109 g C m<sup>−2</sup> yr<sup>−1</sup>) compared to that of the deciduous broadleaf forest NEP of 200 ± 83 g C m<sup>−2</sup> yr<sup>−1</sup>. Similarly, the mean annual evapotranspiration (ET) of the conifer forest over the 6-year study period was higher (442 ± 33 mm yr<sup>−1</sup>) compared to that of the broadleaf forest (388 ± 34 mm yr<sup>−1</sup>), but with similar interannual variability. Significant abnormalities in fluxes were measured between sites during drought years. Summer meteorology greatly impacted fluxes at both sites, but to varying degrees and with varying responses. In general, warm temperatures caused higher ecosystem respiration (RE), resulting in reduced mean annual NEP values – an impact that was more pronounced at the deciduous broadleaf forest compared to the evergreen needle-leaf forest. However, during drought years, the evergreen forest saw greater annual reduction in carbon sequestration compared to the deciduous forest. In the evergreen conifer forest, variability of summer meteorology greatly controlled the forest's annual carbon sink-source strength. Annual ET at both forests was driven by changes in air temperature (Ta), with the largest annual ET measured in the warmest years in the deciduous forest. Additionally, prolonged dry periods with increased Ta, greatly reduced ET. During drought years, the carbon and water fluxes of the deciduous forest were less sensitive to changes in temperature or water availability compared to the evergreen forest. If longer periods of increased temperatures and larger precipitation variability during summer months are to be expected under future climates, our findings suggest the carbon sink capacity of the deciduous forest will continue, while that of the conifer forest remains uncertain in the study region.</p>
doi:10.5194/bg-2019-457 fatcat:keb3ei657raitdueieil5tk3gu