Effects of Restoration Techniques on Soil Carbon and Nitrogen Dynamics in Florida Longleaf Pine (Pinus palustris) Sandhill Forests

Abstract

Historic fire suppression and intensive forest management in longleaf pine (Pinus palustris) sandhill forests has resulted in hardwood encroachment and degradation of this fire-dependent ecosystem. Active management is now required to restore native community structure and composition, but little is known about the long-term impacts of typical restoration techniques on ecosystem properties. In 1994, the Longleaf Pine Restoration Project (LPRP) was established in fire-excluded longleaf pine sandhills of Eglin Air Force Base, Florida, to explore the effects of restoration treatments on plant and animal community composition and soil processes. Experimental treatments applied included three hardwood reduction techniques and delayed burn. Reference sites were concurrently monitored. Fifteen years later, we revisited the LPRP plots to determine whether soil processes showed lasting treatment effects. This study showed that there were OPEN ACCESSForests 2014, 5 499 no differences in soil C and N between the reference and the fire-suppressed plots prior to the treatments, suggesting that soil C and N were relatively resistant to degradation. This study also showed that the restoration treatments had a significant effect by reducing soil C, but this effect was only short-lived (<3 years). In addition, a MRPP (multi-response permutation procedure) analysis showed that only the herbicide treatment was still different from the reference plots 15 years after the initial treatments. Thus, this study suggests that repeated fires (or lack of) or hardwood removal treatments have little detectable effect on soil nutrients in these nutrient-poor ecosystems.

Overstory‐derived surface fuels mediate plant species diversity in frequently burned longleaf pine forests

“…While unmeasured and outside the scope of this study, nutrient input post‐fire is highly variable (Lavoie et al. ) and has been shown to stimulate the growth of understory species (Certini ).…”

Bioturbation by mammals and fire interact to alter ecosystem-level nutrient dynamics in longleaf pine forests

“…Restoration efforts in longleaf pine ecosystems, as in other systems, rely on considerable human intervention to restore ecosystem structure and species diversity (e.g., repeated prescribed fires and selective silvicultural treatments) [ 21 , 36 , 37 , 73 , 74 ]. By altering interactions between biotic and abiotic processes, pocket gophers and other ecosystem engineers can produce one of the target outcomes of restoration for longleaf pine ecosystems, increased heterogeneity of the litter layer, while simultaneously conserving limiting nutrients that potentially are depleted during frequent fires.…”

Opportunities for Research on Carbon Management in Longleaf Pine Ecosystems

“…This includes reducing the hazard and risk of insect and disease outbreaks and wildfire in fire-suppressed, overstocked stands with dense midstories. Restoration treatments that involve prescribed burning and hardwood removal may initially reduce live tree and soil C [35] but may limit the probability of substantial C emissions from catastrophic wildfires and insect and disease outbreaks. For example, mastication (also referred to as mulching) can also be used to reduce hardwood encroachment and to create favorable conditions for using prescribed fire (e.g., reduced midstories and ladder fuels).…”