# Carbon Dynamics of _Pinus palustris_ Ecosystems Following Drought
## 1 Introduction
While the longleaf system will continue to be subjected to anthropogenic influence, this fire-maintained system is now dependent on humans to manage and maintain ecosystem integrity with low intensity, high frequency prescribed fire [27]. Moreover, climate change is expected to alter temperatures and precipitation patterns in the SEUS region, which, in turn, may reduce managers' ability to maintain burn cycles, placing additional stress on the system and its ability to sequester carbon [14]. In this study, we follow up on the early findings of [PERSON] _et al._[18; 19], which examined the role that drought plays in the biogeochemical cycles of longleaf ecosystems along an edaphic gradient. These earlier studies showed that drought played a larger role in controlling the carbon dynamics of these forests compared to prescribed fire. Fire's effect on these systems was limited to \(\sim\)30 days post-fire [20], after which, carbon uptake retuned to pre-fire rates. However, our earlier study also emphasized the need for longer-term studies that incorporate time series covering larger variations in climate. In our current study, we focus on the two sites at the ends of this edaphic moisture gradient, and follow their recovery from drought (as discussed in References [18; 19]). This synthesis activity presents an opportunity to reduce uncertainties in our understanding of the pace, pattern, and process of carbon dynamics of differently adapted longleaf sites over a range of climates. Dependent on their position in the landscape, forest sites may respond differently to cumulative, chronic environmental stresses and disturbances [28]. This study also sheds light on differences in adaptive strategies of forest ecosystems and their recovery capabilities as a result of their placement in the landscape. We hypothesize that (i) the magnitude of physiological change during recovery from drought would be minimal in the xeric site because the plants' phenotypical responses have evolved with water as a limited resource, as compared to the mesic site, and (ii) following a drought, the mesic site would be a greater sink of carbon compared to the xeric site. The increase in the ecosystem's capacity to sequester more carbon would be associated with an increase in photosynthetic capacity following recovery from drought. In this study, we tested the physiological variations of whole ecosystem processes (carbon capture) at each site under drought and non-drought conditions, with emphasis on drought recovery by examining and quantifying changes in light and temperature response on carbon processes over a seven-year period, which included \(\sim\)4 years of 'normal' conditions and \(\sim\)3 years of drought. We also utilized orthonormal wavelet transformation to analyze the frequency distribution of net ecosystem exchange of CO2 (NEE), gross ecosystem CO2 exchange (GEE) and ecosystem respiration (Reco) rates during pre-drought, drought and recovery from drought. In addition, we examined diurnal activity of carbon dynamics to detect the physiological adaptive capacity of these two sites.