Print PageWater availability and nutrients are the major factors limiting the growth of loblolly pine in the southeastern United States. Loblolly pine makes up the majority of the 12.8 million acres of pine plantations in the Southeast. Given the predicted changes in climate, a better understanding of the impact of the interaction between water and nutrient availability on the growth of loblolly pine is needed. The goal of this project is to investigate the influence of a 30% reduction in ambient precipitation combined with varying nutrient availability on the mechanisms controlling growth of loblolly pine. Four replicates of a randomized 2 x 2 factorial experimental design were installed in a 6-year-old loblolly pine plantation located in Taliaferro, Georgia. Treatments are two levels of precipitation, ambient and a 30% reduction, and two levels of fertilization, operational and none. Precipitation is reduced by rainfall interception troughs. Growth and physiology are being studied by examining leaf area index, intercepted radiation efficiency, photosynthetic capacity, chlorophyll fluorescence and tree and stand level transpiration and water use efficiency.
Results/Conclusions
At the beginning of the study, water potential ranged from -0.6 MPa to -2.20 MPa. Winter light-saturated net photosynthesis varied from 3.6 µmol m2 s-1 to 5.1 µmol m2 s-1. Transpiration measured using thermal dissipation sap flow probes was typical of the winter rates and maximum transpiration was 2 mm day-1. Fertilizer was applied on March 28, 2012 and as the summer progresses drought impacts on intercepted radiation efficiency, leaf area, photosynthesis, plant water relations and transpiration will be monitored. Improved understanding of the physiological and growth responses of loblolly pine to drought conditions will yield greater insight into the productivity of the species in future climatic conditions and aid in the mitigation of a changing climate.
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