Effects of a prescribed fire on water use and photosynthetic capacity of pitch pines
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Although wildfires are important in many forested ecosystems, increasing suburbanization necessitates management with prescribed fires. The physiological responses of overstory trees to prescribed fire has received little study and may differ from typical wildfires due to the lower intensity and timing of prescribed fire in the dormant season. Trees may be negatively affected by prescribed fires if injury occurs, or positively affected due to reduced competition from understory vegetation and release of nutrients from partially consumed litter. We estimated sap flow and photosynthetic parameters before a late-March prescribed fire and throughout the growing season in burned and unburned pitch pine (Pinus rigida L.) sites in the New Jersey Pinelands to determine how water use and photosynthetic capacity were affected. Water use was similar between sites before the fire but 27 % lower in burned trees immediately following the fire. After about a month, water use in the burned site was 11–25 % higher than pines from the unburned site and these differences lasted into the summer. Photosynthetic capacity remained similar between sites but instantaneous intrinsic water use efficiency increased by 22 % and maximum Rubisco carboxylation rate (V cmax) was over three times greater in the summer compared to the pre-fire period in the burned site, whereas the unburned site exhibited similar V cmax and intrinsic water use efficiencies between pre-fire and summer measurements. These differences in physiology suggest that the prescribed fire altered the amount of water and nutrients that pines had access to and led to increased water use and water use efficiency; both of which are important in this water- and nutrient-limited ecosystem.
KeywordsControlled burn Disturbance Photosynthesis Pine-dominated Sap flow
The authors would like to thank the New Jersey Forest Fire Service, specifically Section Warden J. Earlin, for conducting the prescribed fire and R. Tripathee, S. Wadhwa, S. Bautista and M. Monzon for laboratory support. This research was supported by United States Department of Agriculture joint venture agreement 10-JV-11242306-136 and the Office of Science (BER), United States Department of Energy DE-SC0007041.
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