The effects of decreased water availability on loblolly pine (Pinus taeda L.) productivity and the interaction between fertilizer and drought.
As part of the regional PINEMAP (Pine Integrated Network: Education, Mitigation, and Adaptation project) funded by the NIFA - USDA, we established a factorial study in McCurtain County, OK near Broken Bow. This study examined the effects of fertilization and ∼30 percent reduction in throughfall on an seven-yearold loblolly pine (Pinus taeda L.) plantation. The objective of this study was to determine effects of decreased water availability and fertilization on tree growth. We measured tree and stand development as well as a suite of ecophysiological variables. Tree growth was reduced in throughfall exclusion treatments and increased in fertilizer treatments. At various times during the measurement period, throughfall exclusion reduced net photosynthesis, stomatal conductance, and mid-day leaf water potential. These results indicate that lower availability of soil moisture reduces leaf gas exchange and slows growth.