Browsing by Author "West, Jason B."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- A Range-Wide Experiment to Investigate Nutrient and Soil Moisture Interactions in Loblolly Pine PlantationsWill, Rodney E.; Fox, Thomas R.; Akers, Madison; Domec, Jean-Christophe; González-Benecke, Carlos; Jokela, Eric J.; Kane, Michael B.; Laviner, Marshall A.; Lokuta, Geoffrey; Markewitz, Daniel; McGuire, Mary Anne; Meek, Cassandra; Noormets, Asko; Samuelson, Lisa; Seiler, John R.; Strahm, Brian D.; Teskey, Robert O.; Vogel, Jason G.; Ward, Eric J.; West, Jason B.; Wilson, Duncan; Martin, Timothy A. (MDPI, 2015-06-03)The future climate of the southeastern USA is predicted to be warmer, drier and more variable in rainfall, which may increase drought frequency and intensity. Loblolly pine (Pinus taeda) is the most important commercial tree species in the world and is planted on ~11 million ha within its native range in the southeastern USA. A regional study was installed to evaluate effects of decreased rainfall and nutrient additions on loblolly pine plantation productivity and physiology. Four locations were established to capture the range-wide variability of soil and climate. Treatments were initiated in 2012 and consisted of a factorial combination of throughfall reduction (approximate 30% reduction) and fertilization (complete suite of nutrients). Tree and stand growth were measured at each site. Results after two growing seasons indicate a positive but variable response of fertilization on stand volume increment at all four sites and a negative effect of throughfall reduction at two sites. Data will be used to produce robust process model parameterizations useful for simulating loblolly pine growth and function under future, novel climate and management scenarios. The resulting improved models will provide support for developing management strategies to increase pine plantation productivity and carbon sequestration under a changing climate.
- Using δ13C and δ18O to analyze loblolly pine (Pinus taeda L.) response to experimental drought and fertilizationLin, Wen; Domec, Jean-Christophe; Ward, Eric J.; Marshall, John; Kin, John S.; Laviner, Marshall A.; Fox, Thomas R.; West, Jason B.; Sun, Ge; McNulty, Steve G.; Noormets, Asko (2019-12)Drought frequency and intensity are projected to increase throughout the southeastern USA, the natural range of loblolly pine (Pinus taeda L.), and are expected to have major ecological and economic implications. We analyzed the carbon and oxygen isotopic compositions in tree ring cellulose of loblolly pine in a factorial drought (similar to 30% throughfall reduction) and fertilization experiment, supplemented with trunk sap flow, allometry and microclimate data. We then simulated leaf temperature and applied a multi-dimensional sensitivity analysis to interpret the changes in the oxygen isotope data. This analysis found that the observed changes in tree ring cellulose could only be accounted for by inferring a change in the isotopic composition of the source water, indicating that the drought treatment increased the uptake of stored moisture from earlier precipitation events. The drought treatment also increased intrinsic water-use efficiency, but had no effect on growth, indicating that photosynthesis remained relatively unaffected despite 19% decrease in canopy conductance. In contrast, fertilization increased growth, but had no effect on the isotopic composition of tree ring cellulose, indicating that the fertilizer gains in biomass were attributable to greater leaf area and not to changes in leaf-level gas exchange. The multi-dimensional sensitivity analysis explored model behavior under different scenarios, highlighting the importance of explicit consideration of leaf temperature in the oxygen isotope discrimination (Delta O-18(c)) simulation and is expected to expand the inference space of the Delta O-18(c) models for plant ecophysiological studies.