Seasonal variation in soil CO2 emission and leaf gas exchange of well\u2010managed commercial Citrus sinensis (L.) orchards

K. K. Ayisi,K. E. Mabitsela,L. Munjonji,T. P. Mafeo,T. Maphanga

doi:10.1007/s11104-021-04986-x

K. K. Ayisi, K. E. Mabitsela + Show 3 more

Open Access

https://doi.org/10.1007/s11104-021-04986-x

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Abstract

PurposeTo investigate whether soil clay content, cultivar and seasonal variation have any effect on soil CO2 emission rates and leaf CO2 assimilation rates in a drip-irrigated commercial Citrus sinensis orchard.MethodsThe study was carried out in the field as a randomised complete block design in a 2 × 2 factorial consisting of two soil types and two citrus cultivars on a drip-irrigated commercial Citrus sinensis orchards with 2-week interval measurements of soil CO2 emission and leaf gas exchanges for a year.ResultsSoil clay content did not influence plant CO2 assimilation rates and soil CO2 emission rates in irrigated citrus. However, seasonal variation significantly influenced both processes. Soil CO2 emission rates were highest in summer and were more than double the rates observed in winter while leaf CO2 assimilation rates were highest in autumn and four times higher than the winter season rates. Mean seasonal soil CO2 emission rates were strongly influenced by mean minimum seasonal temperatures while leaf CO2 assimilation rates only showed a relatively weak relationship with mean maximum seasonal temperatures.ConclusionsSoil clay content did not influence soil CO2 emission and assimilation rates in drip irrigated citrus suggesting a non-significant effect of clay content for soils subjected to similar management practices. Citrus CO2 assimilation rate peaks in the autumn while soil CO2 emission rates peak in summer. A snapshot analysis of CO2 sequestration rates suggests that irrigated citrus orchards are net sinks of CO2 in summer, autumn and winter season.

Highlights

Soil CO2 fluxes play a vital role in the terrestrial carbon cycle as they integrate the decomposition of organic matter and root respiration (Paudel et al 2018; Wu 2020)
Soil clay content did not influence soil CO2 emission and assimilation rates in drip irrigated citrus suggesting a non-significant effect of clay content for soils subjected to similar management practices
Citrus CO2 assimilation rate peaks in the autumn while soil CO2 emission rates peak in summer

Summary

Introduction

Soil CO2 fluxes play a vital role in the terrestrial carbon cycle as they integrate the decomposition of organic matter and root respiration (Paudel et al 2018; Wu 2020). Soil respiration is anticipated to contribute even more CO2 to the atmosphere due to its sensitivity to global warming (Davidson and Janssens 2006). The dynamics of soil respiration are still not well understood due to the high measured variability in terrestrial ecosystems (Bond-Lamberty and Thomson 2010). Soil CO2 emission rates and leaf CO2 assimilation rates respond strongly to environmental conditions such as temperature and water availability (Avola et al 2008; Bond-Lamberty and Thomson 2010; Davidson and Janssens 2006; Qu et al 2020; Tankari et al 2019; Wu 2020). Soil with high clay content can physically protect organic carbon within aggregates from microbial decomposition decreasing the amount of CO2 lost through decomposition (Hassink et al 1993; Razafimbelo et al 2008)

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