Carbon Dynamics of Pinus palustris Ecosystems Following Drought

Gregory Starr,Susanne Wiesner,Andrew Whelan,Andrew Whelan,Sujit Kunwor,Lindsay Boring,Christina Staudhammer,Henry Loescher,Henry Loescher,Henry Loescher,Robert Mitchell,Andres Baron

doi:10.3390/f7050098

Abstract

Drought can affect forest structure and function at various spatial and temporal scales. Forest response and recovery from drought may be a result of position within landscape. Longleaf pine forests in the United States have been observed to reduce their carbon sequestration capacity during drought. We collected eddy covariance data at the ends of an edaphic longleaf pine gradient (xeric and mesic sites) over seven years; two years of normal rainfall were followed by 2.5 years of drought, then 2.5 years of normal or slightly above-average rainfall. Drought played a significant role in reducing the physiological capacity of the sites and was compounded when prescribed fire occurred during the same periods. The mesic site has a 40% greater basal area then the xeric site, which accounts for its larger sequestration capacity; however, both sites show the same range of variance in fluxes over the course of the study. Following drought, both sites became carbon sinks. However, the xeric site had a longer carry-over effect and never returned to pre-drought function. Although this study encompassed seven years, we argue that longer studies with greater spatial variance must be undertaken to develop a more comprehensive understanding of forest response to changing climate.

Highlights

Limitations in water availability in forested ecosystems can elicit varied responses over contrasting spatial and temporal scales
To evaluate the differences in physiological activity following before, during and after drought, we examined changes in the parameterization of net ecosystem exchange of CO2 (NEE) light response and temperature response curves over the time period
The timing of rain events is expect to be altered, with increases in heavy precipitation events and great periods of drought between these events. The combination of these changes leads to additional scientific questions regarding the future carbon cycles of longleaf pine forest and their ability to maintain structure and function [14]

Summary

Introduction

Limitations in water availability in forested ecosystems can elicit varied responses over contrasting spatial and temporal scales. On short temporal and spatial scales, individual trees or stands can alter their leaf morphology to limit the loss of water from the system and try to reduce the stress that is being imposed on the plant and the ecosystem [1]. Forests may reduce their physiological activity, on the order of minutes to hours, to reduce water loss when demands are greatest during drought or high afternoon vapor pressure deficits [2]. These reductions in physiological activity are typically associated with stomatal limitations, driven by lack of soil water availability. It has been hypothesized that the timing of leaf flush co-occurs with a plant’s ability to maximize carbon

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Discussion

Conclusion