Forest Floor and Mineral Soil Respiration Rates in a Northern Minnesota Red Pine Chronosequence

Matthew Powers,Martin Jurgensen,John Bradford,Brian Palik,Randall Kolka

doi:10.3390/f9010016

Abstract

We measured total soil CO2 efflux (RS) and efflux from the forest floor layers (RFF) in red pine (Pinus resinosa Ait.) stands of different ages to examine relationships between stand age and belowground C cycling. Soil temperature and RS were often lower in a 31-year-old stand (Y31) than in 9-year-old (Y9), 61-year-old (Y61), or 123-year-old (Y123) stands. This pattern was most apparent during warm summer months, but there were no consistent differences in RFF among different-aged stands. RFF represented an average of 4–13% of total soil respiration, and forest floor removal increased moisture content in the mineral soil. We found no evidence of an age effect on the temperature sensitivity of RS, but respiration rates in Y61 and Y123 were less sensitive to low soil moisture than RS in Y9 and Y31. Our results suggest that soil respiration’s sensitivity to soil moisture may change more over the course of stand development than its sensitivity to soil temperature in red pine, and that management activities that alter landscape-scale age distributions in red pine forests could have significant impacts on rates of soil CO2 efflux from this forest type.

Highlights

Soil respiration represents about 70% of ecosystem respiration in temperate forests [1,2], and includes a combination of respiration from plant roots, mycorrhizae, and microorganisms in the leaf litter, humus, and mineral soil
Our results suggest that the forest floor early stages of stem exclusion (Y31) showed a distinct seasonal pattern of RS compared to a young influences soil respiration both directly, through the contribution of CO2 efflux associated with the stand regenerating after a clearcut, a mature stand, and an old stand
As other studies have indicated [10,19,37], we found that RS increased exponentially with increasing soil temperature, so low soil temperatures are a likely cause of the low soil respiration rates in Y31

Summary

Introduction

Soil respiration represents about 70% of ecosystem respiration in temperate forests [1,2], and includes a combination of respiration from plant roots, mycorrhizae, and microorganisms in the leaf litter, humus, and mineral soil Variables such as soil temperature [3,4], soil moisture [2,5,6,7], litter quality and quantity [4,8], and local stand structure [3,9] exert strong controls over soil respiration in forests. Soil temperature and soil moisture may covary seasonally, or show varying relationships across sites, leading to confounded effects on soil respiration [10,11] Changes in these variables that occur over the course of stand development could lead to changes in soil respiration as forests age. As land management agencies begin to incorporate C storage and sequestration into their management goals there is an increasing need to understand how developmental changes influence belowground C cycling

Methods

Results

Conclusion