Spatial and temporal variation of CO<sub>2</sub> efflux along a disturbance gradient in a <i>miombo</i> woodland in Western Zambia

Abstract

Abstract. Carbon dioxide efflux from the soil surface was measured over a period of several weeks within a heterogeneous Brachystegia spp. dominated miombo woodland in Western Zambia. The objectives were to examine spatial and temporal variation of soil respiration along a disturbance gradient from a protected forest reserve to a cut, burned, and grazed area outside, and to relate the flux to various abiotic and biotic drivers. The highest daily mean fluxes (around 12 µmol CO 2 m −2 s −1 ) were measured in the protected forest in the wet season and lowest daily mean fluxes (around 1 µmol CO 2 m −2 s −1 ) in the most disturbed area during the dry season. Diurnal variation of soil respiration was closely correlated with soil temperature. The combination of soil water content and soil temperature was found to be the main driving factor at seasonal time scale. There was a 75% decrease in soil CO 2 efflux during the dry season and a 20% difference in peak soil respiratory flux measured in 2008 and 2009. Spatial variation of CO 2 efflux was positively related to total soil carbon content in the undisturbed area but not at the disturbed site. Coefficients of variation of efflux rates between plots decreased towards the core zone of the protected forest reserve. Normalized soil respiration values did not vary significantly along the disturbance gradient. Spatial variation of respiration did not show a clear distinction between the disturbed and undisturbed sites and could not be explained by variables such as leaf area index. In contrast, within plot variability of soil respiration was explained by soil organic carbon content.Correspondence to: L. Merbold (merboldl@ethz.ch) Three different approaches to calculate total ecosystem respiration (R eco ) from eddy covariance measurements were compared to two bottom-up estimates of R eco obtained from chambers measurements of soil-and leaf respiration which differed in the consideration of spatial heterogeneity. The consideration of spatial variability resulted only in small changes of R eco when compared to simple averaging. Total ecosystem respiration at the plot scale, obtained by eddy covariance differed by up to 25% in relation to values calculated from the soil-and leaf chamber efflux measurements but without showing a clear trend.

Validation and comparison of two soil‐vegetation‐atmosphere transfer models for tropical Africa

“…The Kissoko (forest) and Tchizalamou (grass) sites are representative for a near‐equatorial (4°S) moist climate and are discussed in‐depth by Nouvellon [2010] and Castaldi et al [2010]. Two other sites have a more pronounced seasonal climate resulting in a deciduous woodland vegetation at the Mongu site (15°S) and a savannah vegetation at the Demokeya site (13°N), discussed in Merbold et al [2010] and Ardö et al [2008].…”

Eddy covariance for quantifying trace gas fluxes from soils

“…Chambers can be used to assess specific topographic effects and therefore provide essential information on the small-scale variability of trace gas fluxes, while EC measurements integrate over larger surface areas. Examples focusing on CO 2 were presented by Norman et al (1997), Lavigne et al (1997), Janssens et al (2000), and Merbold et al (2011). Combined CH 4 flux measurements were carried out by Parmentier et al SOIL, 1, 187-205, 2015 www.soil-journal.net/1/187/2015/ (2011), Zhang et al (2012), and J. M. , and N 2 O was assessed by Christensen et al (1996), Laville et al (1999, and K. .…”

Temporal and spatial variations of soil CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O fluxes at three differently managed grasslands

“…Moreover, chamber methods, in contrast to the eddy covariance method, are capable of detecting small flux magnitudes that are characteristic for CH 4 and N 2 O fluxes between climatic-or management-driven pulse events (Baldocchi et al, 2012). In addition, the use of chambers allows for detection of spatial patterns in GHG fluxes (Flessa et al, 2002;Merbold et al, 2011), an important aspect when studying managed or undulating grassland sites (Ambus and Christensen, 1994;Ball et al, 1997;Mathieu et al, 2006). Especially N 2 O and CH 4 fluxes are known for their non-uniform spatial distribution of sources and sinks (e.g., Matthias et al, 1980;Folorunso and Rolston, 1984;van den Pol-van Dasselaar et al, 1998).…”