Effects of climate factors and vegetation on the CO2fluxes and δ13C from re-established grassland

Yaroslav Bezyk,Izabela Sówka,Maxim Dorodnikov,B Kaźmierczak,H Jouhara,J Danielewicz,K Piekarska,M Kutyłowska

doi:10.1051/e3sconf/20172200017

Abstract

The relationship between stable carbon isotope composition (δ13 C -CO2 ) of soil CO2 flux, vegetation cover and weather conditions was investigated in a short-term campaign at a temperate re-established grassland in Germany. During August-September 2016, we measured surface CO2 flux with a closed-chamber method at high and low soil moisture content (‘wet’, ‘dry’), with and without above ground vegetation (‘planted’, ‘clear-cut’) and estimated the effects of treatments on respective δ13 C -CO2 values. The concentration and stable carbon isotope composition of CO2 were determined using the gas chromatography and mass spectrometry analyses. The δ13 C -CO2 of the soil fluxes decreased over sampling time for the ‘dry-warm’ conditions and canopy manipulation. The ecosystem-derived δ13 C -CO2 values (corrected for the atmospheric δ13 C -CO2 ) which included predominately soil-and rhizosphere respiration were –26.2 ± 0.8‰ for the ‘dry-warm’ conditions and decreased down to –28.1 ± 1.4‰ over a period of 28 days from late August to the end of September. The decrease coincided with the lowering of CO2 flux and could be attributed to changes in plant physiological processes at the end of the vegetation season. Though the removal of shoots did not significantly affect the δ13 C -CO2 values as compared with the control, the pattern of further δ13 C -CO2 decrease (down to –28.8 ± 0.8‰) supported the role of living vegetation in a contribution of 13 C-enriched CO2 to the ecosystem respiration.

Highlights

Soils as source and sink of the carbon dioxide (CO2) are an important component in the global carbon (C) balance
Analysis of field observations in large part demonstrates that the soil temperature is the primary factor determining the rates of soil respiration [3, 4], while other numerous data considers that the effect of temperature is constrained by soil moisture availability [5, 6]
The weather conditions data on the day of the sampling: air temperature, photosynthetic active radiation (PAR) relative humidity, precipitation [14] are summarised in table 2

Summary

Introduction

Soils as source and sink of the carbon dioxide (CO2) are an important component in the global carbon (C) balance. The gas exchange between the atmosphere, vegetation and soil is controlled by the complex mechanisms related to various physical (temperature, moisture) and biochemical soil properties (microbial communities and activity, organic matter content), regional geographical features and meteorological conditions (duration of vegetation period, photosynthetically active radiation, precipitation, etc.) [1]. In order to predict the response of C balance to environmental changes, it is necessary to determine effects of different climate factors including diurnal and season temperature changes, precipitation level as well as the role of live vegetation (aboveground biomass, plant ground cover) in an ecosystem. The impact of moisture on soil respiration and microbial activity is more complex than temperature because moisture availability depends on physical characteristics of soil (texture, porosity, and organic matter content) [7]. The separating the effect of temperature on respiration from the effect of moisture or vice versa in the field face difficulties, since these parameters tend to vary continuously and inversely

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