Seasonal Soil Respiration Dynamics and Carbon-Stock Variations in Mountain Permanent Grasslands Compared to Arable Lands

Matteo Francioni,Ayaka Wenhong Kishimoto-Mo,Laura Trozzo,Marco Toderi,Nora Baldoni,Roberto Lai,Giulio Tesei,Marina Allegrezza,Lucia Foresi,Katarina Budimir,Paride D’Ottavio

doi:10.3390/agriculture9080165

Abstract

Permanent grasslands provide a wide array of ecosystem services. Despite this, few studies have investigated grassland carbon (C) dynamics, and especially those related to the effects of land-use changes. This study aimed to determine whether the land-use change from permanent grassland to arable lands resulted in variations in the soil C stock, and whether such variations were due to increased soil respiration or to management practices. To address this, seasonal variations of soil respiration, sensitivity of soil respiration to soil temperature (Q10), and soil C stock variations generated by land-use changes were analyzed in a temperate mountain area of central Italy. The comparisons were performed for a permanent grassland and two adjacent fields, one cultivated with lentil and the other with emmer, during the 2015 crop year. Soil respiration and its heterotrophic component showed different spatial and temporal dynamics. Annual cumulative soil respiration rates were 6.05, 5.05 and 3.99 t C ha−1 year−1 for grassland, lentil and emmer, respectively. Both soil respiration and heterotrophic soil respiration were positively correlated with soil temperature at 10 cm depth. Derived Q10 values were from 2.23 to 6.05 for soil respiration, and from 1.82 to 4.06 for heterotrophic respiration. Soil C stock at over 0.2 m in depth was 93.56, 48.74 and 46.80 t C ha−1 for grassland, lentil and emmer, respectively. The land-use changes from permanent grassland to arable land lead to depletion in terms of the soil C stock due to water soil erosion. A more general evaluation appears necessary to determine the multiple effects of this land-use change at the landscape scale.

Highlights

Soil respiration is defined as the release of carbon dioxide (CO2 ) from the soil, and it includes the respiration of plant roots, the rhizosphere, microbes and fauna
Uncertainties and contrasting data on the size and distribution of CO2 sources and sinks such as grasslands indicate the need for further efforts to understand soil respiration dynamics, so as to better understand how the soil C sock responds to global changes, including land-use changes [8]. In this context of uncertainties, we investigated whether land-use change from permanent grassland to arable lands in temperate mountain areas results in variations in soil C stock, and whether such variations are due to increased soil respiration or to management practices
Soil respiration dynamics are influenced by climate and weather conditions, and different patterns of CO2 fluxes have been reported in different climate areas

Summary

Introduction

Soil respiration is defined as the release of carbon dioxide (CO2 ) from the soil, and it includes the respiration of plant roots, the rhizosphere, microbes and fauna This respiration is the second most relevant carbon (C) flux between terrestrial ecosystems and the atmosphere [1], and due to climate change, many studies have been focused on the CO2 emissions over the last decades. Land use changes are defined as conversion from one land cover type to another, and these can have key roles in terms of the global C budget [4,5,6] This is in turn affected by changes in management practices (e.g., reduced grazing pressure), which can lead to encroachment of shrubs and/or trees into grasslands [7]. The influence of soil respiration on climatic changes is well recognized and has been studied for a wide array of terrestrial ecosystems, there remains a lack of extensive assessment for grassland ecosystems [1,8,9]

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