Connecting soil organic carbon and root biomass with land-use and vegetation in temperate grassland.

Devan Allen Mcgranahan,James R Miller,Jessica J Veenstra,Diane M Debinski,David M Engle,Aaron L Daigh

doi:10.1155/2014/487563

Abstract

Soils contain much of Earth's terrestrial organic carbon but are sensitive to land-use. Rangelands are important to carbon dynamics and are among ecosystems most widely impacted by land-use. While common practices like grazing, fire, and tillage affect soil properties directly related to soil carbon dynamics, their magnitude and direction of change vary among ecosystems and with intensity of disturbance. We describe variability in soil organic carbon (SOC) and root biomass—sampled from 0–170 cm and 0–100 cm, respectively—in terms of soil properties, land-use history, current management, and plant community composition using linear regression and multivariate ordination. Despite consistency in average values of SOC and root biomass between our data and data from rangelands worldwide, broad ranges in root biomass and SOC in our data suggest these variables are affected by other site-specific factors. Pastures with a recent history of severe grazing had reduced root biomass and greater bulk density. Ordination suggests greater exotic species richness is associated with lower root biomass but the relationship was not apparent when an invasive species of management concern was specifically tested. We discuss how unexplained variability in belowground properties can complicate measurement and prediction of ecosystem processes such as carbon sequestration.

Highlights

Soils constitute the greatest stock of terrestrial organic carbon [1] and soil properties can be affected by land-use and management [2, 3]
We studied the effect of grazing history, prescribed fire, and the invasion of an exotic C3 grass on root biomass and soil organic carbon (SOC) in rangeland managed with fire and grazing in the tallgrass prairie region of central North America
Deep sampling clearly increases the amount of organic carbon and root biomass accounted for under these grasslands

Summary

Introduction

Soils constitute the greatest stock of terrestrial organic carbon [1] and soil properties can be affected by land-use and management [2, 3]. Approximately one-quarter of the potential carbon sequestration in soils occurs in rangelands [4]. Rangelands are one of the most widespread humanimpacted biomes on Earth [5], making their role in carbon sequestration sensitive to land-use and climate change [6, 7]. In rangeland, grazing can increase bulk density [8, 9] and has a neutral or negative effect on soil organic carbon (SOC) [10,11,12]. Fire increases root growth in tallgrass prairie [13, 15], but across fire-adapted ecosystems the effect of fire on soil carbon varies with severity and temporal scale [16,17,18,19]. Temporal scale is especially important to SOC because SOC can decline over just a few years, SOC accumulation occurs on the scale of decades [20, 21]

Methods

Results

Conclusion