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Effect of the relative abundance of conifers versus hardwoods on soil d13C enrichment with soil depth in eastern canadian forests

Summary

Published in Ecosystems 18: 629-642

Soils are a major component of the global C cycle, and considerable effort has been dedicated to improve our understanding of factors controlling soil organic C (SOC) turnover and stabilization in the last decades. Carbon stable isotopes are useful in this respect as they represent an integrative indicator of SOC biogeochemical processing. In the present study, C concentration and d13C were measured in soil horizons of 21 forest sites located at the transition zone between the hardwood and the conifer forest in Québec, Canada, and related to 13 biophysical variables to identify the main drivers of SOC storage and turnover. Carbon concentrations in the forest floor (FF) and the B- and C-horizons were, respectively, strongly correlated with percentage of clay (Pclay), the mean annual precipitation: potential evapotranspiration ratio (MAP:PET), and percentage of hardwoods (Phwd). In FF, d13C was poorly correlated with the studied variables, whereas in mineral horizons, it was significantly correlated with mean annual air temperature (MAAT) and the percentage of conifers (Pc) and Pclay. Across the studied area, d13C increased on average by 2.00/00 from the FF to the C-horizon. The isotopic enrichment with soil depth (b) was strongly negatively correlated with Pc, which explained 55% of its variability among sites. This suggests that the vegetation type is an important driver of soil C long-term turnover rate in forest ecosystems. Overall, our data suggest that hardwood forest expansion in response to climate change might reduce the stability and the storage of SOC in the future.

Sector(s): 

Forests

Categorie(s): 

Scientific Article

Theme(s): 

Ecosystems and Environment, Forest Ecology, Forestry Research, Forests

Author(s)

MARTY, Charles, Daniel HOULE and Christian GAGNON

Year of publication :

2015

Keywords :

sols, d13C, carbone organique du sol, taux de renouvellement du carbone, forêts boréales, écologie forestière, écosystèmes et environnement, article scientifique de recherche forestière, ecosystems and environment, forest ecology, forest soils, d13C, soil organic carbon, carbon turnover time, isotopic enrichment factor, boreal forests

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