Model Estimates of Nutrient Uptake by Red Spruce Respond to Soil Temperature

J Michael Kelly,J Devereux Joslin,Frank C Thornton

doi:10.4236/jep.2011.26089

Abstract

A better understanding of the mechanisms that control nutrient acquisition in the context of plant and ecosystem responses to climate change is needed. Mechanistic nutrient uptake models provide a means to investigate some of the impacts of temperature change on soil nutrient supply and root uptake kinetics through the simulation of key soil and plant processes. The NST 3.0 model, in combination with literature values on plant and soil parameters from a red spruce (Picea rubens L.) site in the southern Appalachians, was used to conduct a series of model simulations focused on the combined effects of changes to the maximal rate of nutrient influx at high concentrations (Imax), root growth rate (k), concentration of nutrient occurring in the soil solution (Cli), and the ability of the soil solid phase to buffer changes to the soil solution nutrient concentration (b). Previous research has indicated that these four parameters are responsive to changes in root zone temperature. Simulated uptake of NH4 increased by a factor of up to 2.6 in response to increases in soil temperature of 1°C to 5°C. The model also projected an increase in P uptake coupled with up to an 80% reduction in solution P concentration in response to a 1°C -5°C increase over a 147-d simulation period. These hypothetical changes, if validated, have interesting implications for plant growth and competition and point to a need for additional studies to better define the impacts of soil temperature on soil nutrient supply and root uptake.

Highlights

Over the 100 years, mean global temperature is projected to increase by 1.5 ̊C to 4.5 ̊C [1]
The NST 3.0 model, in combination with literature values on plant and soil parameters from a red spruce (Picea rubens L.) site in the southern Appalachians, was used to conduct a series of model simulations focused on the combined effects of changes to the maximal rate of nutrient influx at high concentrations (Imax), root growth rate (k), concentration of nutrient occurring in the soil solution (Cli), and the ability of the soil solid phase to buffer changes to the soil solution nutrient concentration (b)
Before proceeding further it is appropriate to consider the assumptions that have been made concerning the magnitudes and directions of change associated with the Cli, b, k, and Imax values used for each nutrient

Summary

Introduction

Over the 100 years, mean global temperature is projected to increase by 1.5 ̊C to 4.5 ̊C [1]. Most studies of soil warming in the forest environment have focused on changes in plant productivity and soil nutrient availability [3,4,5,6] with only Gessler et al [7] and Adam et al [8] assessing the potential changes in nutrient uptake as a function of changes in root zone temperature. Since nutrient uptake is a physiologically mediated process, it follows that changes in soil temperature could have an impact on the rate at which plants take up nutrients. Weih and Karlsson [5] found that mountain birch root-N uptake rate and plant-N concentration were positively correlated with increases in soil temperature. In a field and laboratory study of Norway spruce, Gessler et al [7] found that very little NO3 was taken up by roots when solution NH4 concentrations were elevated and that NH4 uptake increased by ap-

Objectives

Methods

Results

Conclusion