Spatial and Temporal Patterns of Carbon Dioxide Flux in Crop and Grass Land‐Use Systems

Abstract

Understanding the field‐scale variability of CO2 fluxes in space and time under different land‐use conditions is important for designing efficient sampling schemes for monitoring C loss from soil. The objectives of this study were to characterize the variability structure of CO2 fluxes and its change throughout a year, evaluate the temporal stability of spatial CO2 flux patterns, and quantify relationships with biotic and abiotic factors in crop and grass systems. In an 80‐ by 60‐m field divided into grass and crop systems, CO2 fluxes were measured with a photo‐acoustic analyzer at 60 locations 22 times during a year. Soil respiration was high when it was warm and wet and low under cool and wet conditions. Measurements of CO2 flux were spatially and temporally dependent for a longer distance and time in the grass system than in the crop system. Spatial patterns of soil respiration were temporally stable, and the larger the average spatial CO2 flux, the more obvious was the temporal stability. The variation of soil respiration was more pronounced in time than in space during the study period. At each location, soil temperature was the major factor controlling the temporal variability of CO2 flux; however, soil temperature did not explain the spatial CO2 flux pattern. Land use impacted the spatial and temporal variability dynamics of CO2 flux. These dynamics should be taken into account for experimental design, the detection of spatial and temporal associations with other variables, and C loss prediction.

Spatial and Temporal Dynamics of Soil‐Surface Carbon Dioxide Emissions in Bioenergy Corn Rotations and Reconstructed Prairies

“…Growing season, cumulative soil-surface CO 2 effluxes ranged from 2.6 to 7.8 Mg CO 2 -C ha −1 with 4.6, 4.5, and 21 as the mean, median, and percent coefficient of variation, respectively. These data are consistent with those commonly reported in the literature (Guzman and Al-Kaisi, 2014;Kreba et al, 2013;Kaspar and Parkin, 2011;Vargas et al, 2010;Pumpanen et al, 2003). Significant intra-crop management zone main effect or the interaction by date were observed for weekly sampled soilsurface CO 2 efflux in the CC and CCW but not for C-s and c-S cropping systems when analyzed across all years (Table 1 and 2).…”

“…Although Wilson and Al-Kaisi (2008) reported that N applications decreased soil-surface CO 2 effluxes for corn rotations in Iowa, Guzman and Al-Kaisi (2014) reported that N application can result in greater potential C inputs to the soil. Kreba et al (2013) reported that soil-surface CO 2 effluxes in a mowed tall fescue and clover system was correlated farther across space and time than effluxes in a winter wheat (Triticum aestivum L.) cropping system. Kreba et al (2013) also reported that soil temperature controlled temporal variability of soil-surface CO 2 effluxes in both the annual and perennial systems but did not control the spatial variability.…”

“…Kreba et al (2013) reported that soil-surface CO 2 effluxes in a mowed tall fescue and clover system was correlated farther across space and time than effluxes in a winter wheat (Triticum aestivum L.) cropping system. Kreba et al (2013) also reported that soil temperature controlled temporal variability of soil-surface CO 2 effluxes in both the annual and perennial systems but did not control the spatial variability. If spatial and temporal variability of soil-surface CO 2 effluxes differ among these types of systems (i.e., wheat and tall fescue), then it would be reasonable to expect even greater differences among corn rotations and perennial systems intended for supplying feedstock to the bioenergy industry.…”

Spatial and temporal variability of soil gas diffusivity, its scaling and relevance for soil respiration under different tillage

“…We carefully removed any litter and crop residuals at the sampling position and extracted the cores directly at the soil surface. The lateral distance between the sampling positions was 0.50 m with two nests of increased sampling intensity (distance: 0.25 m) in the middle of each treatment as demonstrated by Kreba et al (2013). The samples were taken prior to seeding in the end of March 2014.…”

“…It is well known that carbon transformation and respiration are strongly influenced by nutrient availability, soil type, soil water content, and soil temperature (Heimann and Reichstein, 2008;Kreba et al, 2013;Raich and Tufekcioglu, 2000). Scott-Denton et al (2003) studied seasonal changes in soil respiration rates and their variances to identify possible covariates (soil temperature, soil water content, soil C) for upscaling respiration measurements.…”