Loblolly Pine Productivity and Water Relations in Response to Throughfall Reduction and Fertilizer Application on a Poorly Drained Site in Northern Florida

Maxwell Wightman,Eric Ward,Wendell Cropper,Timothy Martin,Carlos Gonzalez-Benecke,Eric Jokela

doi:10.3390/f7100214

Abstract

Loblolly pine (Pinus taeda L.) forests are of great ecological and economic value in the southeastern United States, where nutrient availability frequently limits productivity. The impact of fertilizer application on the growth and water relations of loblolly pine has been investigated by numerous studies; however, few field experiments have examined the effects of drought. Drought is of particular interest due to the potential for climate change to alter soil water availability. In this study, we investigated the impact of fertilizer application and a 30% reduction in throughfall on loblolly pine productivity, transpiration, hydraulic conductance, and stomatal conductance. The study was installed in a ten-year-old loblolly pine plantation on a somewhat poorly drained site in northern Florida. Throughfall reduction did not impact tree productivity or water relations of the trees. This lack of response was attributed to abundant rainfall and the ability of trees to access the shallow water table at this site. Fertilizer application increased basal area production by 20% and maximum leaf area index by 0.5 m2∙m−2, but it did not affect whole-tree hydraulic conductance or the sensitivity of stomatal conductance to vapor pressure deficit. During the spring, when leaf area and vapor pressure deficit were high, the fertilizer-only treatment increased monthly transpiration by 17% when compared to the control. This relationship, however, was not significant during the rest of the year.

Highlights

The concentration of carbon dioxide (CO2 ) and other greenhouse gases in the Earth’s atmosphere have increased markedly due to the combustion of fossil fuels and land use changes
It is likely that the trees at the study site were able to access the water table as numerous studies have shown that the water table typically fluctuates between 2m and the surface on somewhat poorly to poorly drained sites in the lower Coastal Plain flatwoods [40,41,42,43,44]
A 30% reduction in throughfall did not significantly affect the growth or water use of a loblolly pine plantation on a poorly drained site in the lower Coastal Plain

Summary

Introduction

The concentration of carbon dioxide (CO2 ) and other greenhouse gases in the Earth’s atmosphere have increased markedly due to the combustion of fossil fuels and land use changes. The concentration of atmospheric CO2 has increased from 280 parts per million (ppm) to over 400 ppm since the start of the Industrial Revolution [1,2]. Increased average temperature and potential decreases in precipitation would decrease soil water availability and increase vapor pressure deficits (D). These changes could influence the carbon gain and water use of loblolly pine (Pinus taeda L.) plantations due to the sensitivity of stomatal conductance to these variables

Objectives

Methods

Results

Discussion

Conclusion