Impacts of prescribed fire onPinus rigidaMill. in upland forests of the Atlantic Coastal Plain

Abstract

A comparative analysis of the impacts of prescribed fire on three upland forest stands in the Northeastern Atlantic Plain, NJ, USA, was conducted. Effects of prescribed fire on water use and gas exchange of overstory pines were estimated via sap-flux rates and photosynthetic measurements on Pinus rigida Mill. Each study site had two sap-flux plots, one experiencing prescribed fire and one control (unburned) plot for comparison before and after the fire. We found that photosynthetic capacity in terms of Rubisco-limited carboxylation rate and intrinsic water-use efficiency was unaffected, while light compensation point and dark respiration rate were significantly lower in the burned vs control plots post-fire. Furthermore, quantum yield in pines in the pine-dominated stands was less affected than pines in the mixed oak/pine stand, as there was an increase in quantum yield in the oak/pine stand post-fire compared with the control (unburned) plot. We attribute this to an effect of forest type but not fire per se. Average daily sap-flux rates of the pine trees increased compared with control (unburned) plots in pine-dominated stands and decreased in the oak/pine stand compared with control (unburned) plots, potentially due to differences in fuel consumption and pre-fire sap-flux rates. Finally, when reference canopy stomatal conductance was analyzed, pines in the pine-dominated stands were more sensitive to changes in vapor pressure deficit (VPD), while stomatal responses of pines in the oak/pine stand were less affected by VPD. Therefore, prescribed fire affects physiological functioning and water use of pines, but the effects may be modulated by forest stand type and fuel consumption pattern, which suggests that these factors may need to be taken into account for forest management in fire-dominated systems.

Pyrogenic Carbon Increases Pitch Pine Seedling Growth, Soil Moisture Retention, and Photosynthetic Intrinsic Water Use Efficiency in the Field

“…It was easier to assign an ecophysiological value to PyC amendment. We found a more modest increase (about 12%) in iWUE fostered by PyCF or PyCA treatments than other investigators (Carlo et al, 2016), who reported a 22% increase in pitch pine photosynthetic iWUE based on PyCF alone. There are bound to be anomalies which arise between PyC analytes for a considerable number of reasons.…”

“…One prominent benefit is ecophysiological; it results from nutrient mobilization and moisture retention. As an increase in photosynthetic intrinsic water use efficiency or iWUE (Renninger et al, 2013;Carlo et al, 2016), iWUE is derived from stable isotope analysis (stated as per mils: parts per thousand, notated as (…”

Decadal-Scale Reduction in Forest Net Ecosystem Production Following Insect Defoliation Contrasts with Short-Term Impacts of Prescribed Fires

“…However, foliar N content of sub-canopy and understory species increased following defoliation, and thus little net change in the total amount of N in foliage occurred and ecosystem WUE was not significantly different pre-and post-disturbance [37,57,63]. Increased foliar N levels and enhanced maximum assimilation rates in the remaining pine needles were observed following relatively intense prescribed burns in the PNR, but not during low-intensity burns [25,64]. Increased N levels and photosynthetic rates following wildland fires are likely related to the transient pulse of inorganic N associated with consumption of forest floor material, in addition to pyro-mineralization and release of phosphorus and basic cations [65,66].…”

“…Increased N levels and photosynthetic rates following wildland fires are likely related to the transient pulse of inorganic N associated with consumption of forest floor material, in addition to pyro-mineralization and release of phosphorus and basic cations [65,66]. Enhanced photosynthetic rates in pine needles did not persist beyond the first growing season following each fire [25,64].…”