Variation in Soil Respiration across Soil and Vegetation Types in an Alpine Valley.

Pascal Vittoz,Wagner L Araujo,Aurélie Rubin,Eric P Verrecchia,Stephanie Grand

doi:10.1371/journal.pone.0163968

Abstract

Background and AimsSoils of mountain regions and their associated plant communities are highly diverse over short spatial scales due to the heterogeneity of geological substrates and highly dynamic geomorphic processes. The consequences of this heterogeneity for biogeochemical transfers, however, remain poorly documented. The objective of this study was to quantify the variability of soil-surface carbon dioxide efflux, known as soil respiration (Rs), across soil and vegetation types in an Alpine valley. To this aim, we measured Rs rates during the peak and late growing season (July-October) in 48 plots located in pastoral areas of a small valley of the Swiss Alps.FindingsFour herbaceous vegetation types were identified, three corresponding to different stages of primary succession (Petasition paradoxi in pioneer conditions, Seslerion in more advanced stages and Poion alpinae replacing the climactic forests), as well as one (Rumicion alpinae) corresponding to eutrophic grasslands in intensively grazed areas. Soils were developed on calcareous alluvial and colluvial fan deposits and were classified into six types including three Fluvisols grades and three Cambisols grades. Plant and soil types had a high level of co-occurrence. The strongest predictor of Rs was soil temperature, yet we detected additional explanatory power of sampling month, showing that temporal variation was not entirely reducible to variations in temperature. Vegetation and soil types were also major determinants of Rs. During the warmest month (August), Rs rates varied by over a factor three between soil and vegetation types, ranging from 2.5 μmol m-2 s-1 in pioneer environments (Petasition on Very Young Fluvisols) to 8.5 μmol m-2 s-1 in differentiated soils supporting nitrophilous species (Rumicion on Calcaric Cambisols).ConclusionsOverall, this study provides quantitative estimates of spatial and temporal variability in Rs in the mountain environment, and demonstrates that estimations of soil carbon efflux at the watershed scale in complex geomorphic terrain have to account for soil and vegetation heterogeneity.

Highlights

Soils play a major role in the global carbon (C) cycle [1]
This study provides quantitative estimates of spatial and temporal variability in Rs in the mountain environment, and demonstrates that estimations of soil carbon efflux at the PLOS ONE | DOI:10.1371/journal.pone
Soil Respiration in an Alpine Valley watershed scale in complex geomorphic terrain have to account for soil and vegetation heterogeneity

Summary

Introduction

Soils play a major role in the global carbon (C) cycle [1]. soil respiration (Rs) is a major contributor to carbon dioxide (CO2) release into the atmosphere, with a CO2 efflux estimated at 80 Pg C yr-1, representing 10% of the atmospheric C content [2] and nine times the recent annual emission from fossil fuels [3]. The explanatory power of temperature on Rs rate is limited in landscapes with strong ecological heterogeneity, such as arid to semiarid areas [10] and mountain environments [11] In the latter case, short-scale spatial variation in Rs has been previously reported (see for instance [12, 13, 14]), but remains largely unattributed [15]. The objective of this study was to quantify the variability of soil-surface carbon dioxide efflux, known as soil respiration (Rs), across soil and vegetation types in an Alpine valley To this aim, we measured Rs rates during the peak and late growing season (July-October) in 48 plots located in pastoral areas of a small valley of the Swiss Alps

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