Using spatial ecology to examine above and belowground interactions on a reclaimed aspen stand in northern Alberta

- Significant spatial patterns were detected in above and belowground properties.
- A fine scale spatial heterogeneity was found in macronutrient availability.
- N-P-S availability showed cyclic spatial association with microbial properties.
- Aboveground control on base cations and micronutrient availability was strong.
- Spatial coupling between above and belowground properties was in progress.

Examining the spatial interactions between above and belowground components of terrestrial ecosystems can give meaningful insight into the ecological processes happening at different scales. Understanding spatial dependence in these processes may help to evaluate reclamation success which is crucial for future management of such areas. The aim of this study was to measure the spatial patterns of soil biogeochemical properties in a young aspen stand reclaimed after oil sands extraction and to evaluate how the patterns were related to nutrient availability. Samples were collected from a 14-year old reclaimed site using a spatially explicit protocol with a minimum resolution of 0.5 m. Field-measured variables included forest floor depth and mass, tree cluster (canopy overlap), distance to nearest tree, and resin available nutrients. Soil microbial properties including microbial biomass C and N, basal respiration, and extracellular enzyme activity were measured during an eight-week laboratory incubation experiment. Geo-statistics were applied to examine the spatial patterns and model the space effect. A fine scale (< 10 m) spatial pattern was found for the majority of stand variables, soil microbial properties, and available macronutrients (N, P, S and base cations). Macronutrients such as N, P and S availability had a fine scale cyclic spatial association with soil microbial properties, with an 8-10 m oscillation, which indicated belowground control on these nutrients. Spatial regression models also suggested a stronger microbial influence on the availability of these nutrients when compared to stand characteristics. However, stand characteristics exhibited significant control on base cations and micronutrient availability through the effect of forest floor depth and tree clustering. Although nutrient availability showed strong spatial relationships with belowground processes in the studied reclaimed site, similar relationships with aboveground properties appeared to be weak, and might require further time to develop.