Life at the interface: above- and below-ground responses of a grazed pasture soil to reforestation

• Soil ecology in a reforested pasture and it an adjacent pasture were studied.
• Reforestation changed vegetation above- and below-ground.
• Soil C, N and C:N were increased with reforestation.
• Total PLFA, fungal:bacterial ratios where higher with reforestation.
• Reforested pasture and it an adjacent pasture had distinct microbial communities.

Conversion of agricultural lands to mixed species woody plantings is increasingly being undertaken as a means of sequestering C and increasing biodiversity. The implications of such changes in land use for soil communities, and the ecosystem services they provide (e.g., nutrient and C cycling), are relatively little understood. Results of a detailed study of vegetation, soil physicochemical properties and soil communities (primarily microbial) to reforestation of a pasture (15 years post reforestation), and its immediately adjacent un-restored pasture, are presented. Whereas the reforested portion of the site had significantly higher levels of tree canopy cover and a well-developed litter layer than the immediately adjacent pasture, the reverse was true for grass biomass. Although there were no differences in total root biomass between the sampling zones, the pasture zone was dominated by fine roots and the reforested zone by coarse roots. Reforestation had a significant impact on soil physicochemical properties, with soil C, C:N and mineral N being higher than in the pasture. The reforestation also supported a greater microbial PLFA, a higher Fungal:Bacterial PLFA ratio and a different microbial community (based on PLFA profiles) from that of the adjacent pasture. There were also differences in earthworm abundance, with earthworms present and absent in soils from the pasture and reforested zones, respectively. All of the changes in vegetation, soil physicochemical properties and biotic communities occurred abruptly at the interface between the land-use types, with no evidence of an interaction between side of fence (reforested versus pasture zones) and distance from the fence. Results are discussed in the context of changes in land-use on soil ecology and their potential functional significance.