Fertilized Pines Use Water More Efficiently But May Suffer Worse in Droughts
Southeastern forests contain one-third of U.S. forest carbon and form the backbone of an industry that supplies 5.5 percent of the jobs and 7.5 percent of the industrial economic activity of the region as well as 16 percent of global industrial wood. The Pine Integrated Network: Education, Mitigation, and Adaptation Project (PINEMAP) aims to connect research, extension, and education professionals with the private landowners representing 20 million acres of planted pine forests in the Atlantic and Gulf coastal states from Virginia to Texas, plus Arkansas and Oklahoma. As part of PINEMAP’s efforts to improve the resilience and sustainability of these forests under variable climates, university and Eastern Threat Center scientists investigated the impacts of fertilization and simulated drought on stand productivity and tree physiology in a 9-year old loblolly pine plantation in central Virginia. The researchers simulated drought by removing 30% of precipitation before it reached the ground using extensive exclusion structures and then continuously monitored environmental conditions and tree water use with a network of more than 100 automated sensors. Recently published results concluded that both fertilization and simulated drought reduced tree water use, with the combination of the two treatments causing the largest reductions (~30%). Meanwhile, fertilized trees had 21 percent larger stems, meaning that fertilization led to greater harvestable wood production with less water used. Since reduced water use is also a sign of stress, fertilized trees may suffer more under a more severe drought. Results to date vary by site, so researchers are studying why fertilization might have a greater impact on drought stress at some sites to help practicing foresters develop site-specific management plans.
Right: An exclusion structure allowed researchers to simulate a 30 percent rainfall reduction in the loblolly plots. Photo by Marshall A. Laviner, Virginia Tech.
References:
Ward, E.J.; Domec, J.-C.; Laviner, M.A.; Fox, T.R.; Sun, G.; McNulty, S.; King, J.; Noormets, A. 2015. Fertilization intensifies drought stress: water use and stomatal conductance of Pinus taeda in a midrotation fertilization and throughfall reduction experiment. Forest Ecology and Management 355: 72-82.
External Partners/Collaborators: North Carolina State University; Virginia Tech
Contact: Steve McNulty, Ge Sun, and Asko Noormets
