Vegetation control on soil organic matter dynamics

S.A Quideau,O.A Chadwick,S.E Trumbore,J.L Johnson-Maynard,R.C Graham,M.A Anderson

doi:10.1016/s0146-6380(00)00171-6

Abstract

Soil organic matter (SOM) formation is one of the least understood steps of the global carbon cycle. An example is uncertainty around the role of plant communities in regulating SOM formation and turnover. Here we took advantage of the highly controlled conditions at the San Dimas lysimeter installation to quantify the influence of oak and pine vegetation on SOM dynamics. SOM turnover rates, estimated using total C and 14C content of litter and physically separable soil fractions, were faster under oak than under pine. In contrast to the rapid turnover for the oak litter (<2 years), the delay in litter incorporation into the mineral soil under pine was a controlling factor of SOM fluxes.

Highlights

Conceptual models of pedogenesis, and ecosystem models such as CENTURY, distinguish between distinct environmental controls over organic matter storage in soils, including climate, vegetation, and parent material (Schimel et al, 1994)
This radiocarbon enrichment has been used as a tracer for assessing Soil organic matter (SOM) turnover in situations where archived soils are available for comparison with modern soils (O'Brien and Stout, 1978; Scharpenseel et al, 1989; Trumbore et al, 1996)
Radiocarbon abundance was measured by accelerator mass spectrometry (AMS), using a sample size as small as 0.5 mg

Summary

Introduction

Conceptual models of pedogenesis, and ecosystem models such as CENTURY, distinguish between distinct environmental controls over organic matter storage in soils, including climate, vegetation, and parent material (Schimel et al, 1994). The detonation of thermonuclear weapons in the 1950's and 1960's enriched atmospheric CO2 with`bomb'' 14C, which subsequently was ®xed in terrestrial plants and incorporated into SOM This radiocarbon enrichment has been used as a tracer for assessing SOM turnover in situations where archived soils (i.e. samples taken prior to the 1960's) are available for comparison with modern soils (O'Brien and Stout, 1978; Scharpenseel et al, 1989; Trumbore et al, 1996). Changes in SOM storage were combined with isotopic measurements to estimate inputs to the soils and SOM turnover rates

Site description

Analyses

Soil carbon storage and 14C measurements

Modeling SOM dynamics