Effect of ecosystem retrogression on stable nitrogen and carbon isotopes of plants, soils and consumer organisms in boreal forest islands

• Published in: Rapid Communications in Mass Spectrometry
• Main Authors: Hyodo, Fujio, Wardle, David A.
• Other Authors: Vetenskapsrådet, FORMAS, The Research Institute for Humanity and Nature, Japan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Northern Sweden
• Online Access: http://dx.doi.org/10.1002/rcm.4095; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Frcm.4095; http://onlinelibrary.wiley.com/wol1/doi/10.1002/rcm.4095/fullpdf

Abstract In the prolonged absence of catastrophic disturbance, ecosystem retrogression occurs, and this involves increased nutrient limitation, and reduced aboveground and belowground ecosystem processes rates. Little is known about how the nitrogen and carbon stable isotope ratios ( δ 15 N and δ 13 C) of plants, soils and consumer organisms respond to retrogression in boreal forests. We investigated a 5000 year chronosequence of forested islands in the boreal zone of northern Sweden, for which the time since lightning‐induced wildfire increases with decreasing island size, leading to ecosystem retrogression. For this system, tissue δ 15 N of three abundant plant species ( Betula pubescens , Vaccinium myrtillus and Pleurozium schreberi ) and humus all increased as retrogression proceeded. This is probably due to enhanced ecosystem inputs of N by biological fixation, and greater dependency of the plants on organic N during retrogression. The δ 13 C of B . pubescens and plant‐derived humus also increased during retrogression, probably through nutrient limitation increasing plant physiological stress. Unlike the plants, δ 15 N of invertebrates (lycosid spiders and ants) did not increase during retrogression, probably because of their partial dependence on aquatic‐derived prey that had a variable δ 15 N signature. The δ 13 C of the invertebrates increased as retrogression proceeded and converged towards that of an aquatic prey source (chironomid flies), suggesting increased dependence on aquatic‐derived prey during retrogression. These results show that measurement of δ 15 N and δ 13 C of plants, soils, and consumers across the same environmental gradient can provide insights into environmental factors that drive both the aboveground and belowground subsystems, as well as the linkages between them. Copyright © 2009 John Wiley & Sons, Ltd.