Spatial variability of soil properties and trace gas fluxes in reclaimed mine land of southeastern Ohio

Uneven distribution of resources in reclaimed mine land could translate in heterogeneous gas fluxes in these ecosystems, but few studies have examined this linkage. In this study, the spatial variability of CO2, CH4 and N2O fluxes and soil properties was investigated at (i) a hay field (90 kg urea–N ha− 1 y− 1), and (ii) a meadow (without any grazing and fertilization since reclamation) established in 1978 and 1982, respectively on reclaimed mine land in southeastern Ohio. Using the static chamber method, gas fluxes were measured in July 2003 and May 2004 every 5 m along two 100-m long transects. Soil cores and disturbed soil samples were collected at each point to determine soil physical and chemical properties. Greater variability of soil properties at the meadow than at the hay site was found and, among the soil parameters, mineral N and N2O flux (CV up to 197%) exhibited the greatest variability. While no significant effect of landscape position on gas flux was found, several micro-depressions were identified as N2O hot spots. Relationships between soil properties and gas fluxes varied with site and gas species. The July 2003 data showed that both CO2 and N2O fluxes were significantly (P < 0.02) related to labile C at the hay site, and to mineral N at the meadow site. The PC1 of a principal component analysis of soil properties showed high loadings for total and labile C at the hay field, and for mineral N at the meadow. Inverse and significant relationships (r2: 0.17–0.24) were found between CH4 flux and macropore volume at the meadow site. These relationships were stronger (R2: 0.30–0.68) with inclusion of soil moisture in the regression. These results underscore the need to minimize soil compaction during reclamation in order to maintain macro-porosity and improve the CH4 uptake capacity of reclaimed mine soils.