COS 171-3 - Novel methods for measuring nonstructural tree carbon flux to assess effects of lengthening growing seasons

Friday, August 11, 2017: 8:40 AM
B117, Oregon Convention Center
George R. Robinson, Department of Biological Sciences, State University of New York at Albany, Albany, NY, Andrei Lapenas, Geography and Planning, State University of New York at Albany, Albany, NY, James Castrcane, College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY and Marie Orton, Biology, State University of New York at Albany, Albany, NY

Lengthening growing seasons, a feature of temperate zone climate change, should in principle increase forest carbon sequestration, when soil moisture is not reduced. However, recent evidence indicates that longer seasons without drying are not leading to commensurate volumes of wood. We hypothesize that seasonal shifts in nonstructural carbon (NSC) allocation shunt photosynthate away from wood formation, to feed other demands during periods of lower insolation, thereby decreasing potential radial growth in trees. We are testing this in three stands of spruce (Picea) in east central New York. Seven trees were instrumented to monitor radial growth over two years, with two-point high-resolution dendrometers. Also measured, beginning in spring 2016, are soil moisture, PAR, temperature, root growth (min-rhizotrons), sap flow rates, and reflectance indices. NDVI and other reflectance indexes were derived from satellite data (LANDSAT), deployment of a UAV, and application of a ground-based IR camera (PHENOCAM network). A novel instrument will be deployed in spring, 2017, to monitor in situ sugar content of tree sap. It consists of enzyme-coated probes and open-source potentiometers calibrated to report concentrations of glucose and sucrose. We report preliminary evidence for seasonal patterns of growth and describe the planning and development of the new probes.


Over two seasons, radial growth has been coordinated among trees and stands each year, beginning by mid-April, and ending in mid- to late September. Early radial growth was coordinated with bud break, separated by a few days. The latter, in turn, coincided with the maximum spring change (infliction point) in NDVI. We interpret this to mean that the infliction point in seasonal NDVI may serve as a phenological marker for shifts in NSC allocation associated with the length of the growing season. In 2016, stem height extension concluded in June, but termination of root growth was not evident until early November, when both air and soil temperature minima had fallen below freezing. Although these observations are generally consistent with our hypothesis, more direct measurements of carbon sequestration and flux are needed. In addition to further applications of high resolution remote sensing NDVI, we will use the new NSC probe to estimate phloem sugar concentrations at key seasonal intervals. This probe has advanced to a field-ready stage, albeit one requiring in situ sap extraction by the user. Following field tests and refinements, an advanced instrument is planned for direct insertion into tree phloem, modeled in part after phloem-feeding aphids.